Postharvest biology and technology of tropical and subtropical fruits: Volume 4: Mangosteen to white sapote

Postharvest biology and technology of tropical and subtropical fruits

© Woodhead Publishing Limited, 2011

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Related titles: Postharvest biology and technology of tropical and subtropical fruits Volume 1 (ISBN 978-1-84569-733-4) While products such as bananas, pineapples and kiwi fruit have long been available to consumers in temperate zones, novel fruits such as litchi and longan are now also entering the market. Tropical and subtropical fruits are vulnerable to postharvest losses and may also be transported long distances for sale. Therefore technologies for quality maintenance postharvest and a thorough understanding of the underpinning biological mechanisms are essential. This authoritative four-volume collection considers the postharvest biology and technology of tropical and subtropical fruit. Volume 1 focuses on key issues of fruit physiology, quality, safety and handling relevant to all those in the tropical and subtropical fruits supply chain. Postharvest biology and technology of tropical and subtropical fruits Volume 2 (ISBN 978-1-84569-734-1) Chapters in Volume 2 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Postharvest biology and technology of tropical and subtropical fruits Volume 3 (ISBN 978-1-84569-735-8) Chapters in Volume 3 of this important collection review factors affecting the quality of different tropical and subtropical fruits, concentrating on postharvest biology and technology. Important issues relevant to each specific product are discussed, such as postharvest physiology, preharvest factors affecting postharvest quality, quality maintenance postharvest, pests and diseases and value-added processed products, among other topics. Details of these books and a complete list of Woodhead’s titles can be obtained by: • visiting our web site at www.woodheadpublishing.com • contacting Customer Services (e-mail: [email protected]; fax: +44 (0) 1223 832819; tel.: +44 (0) 1223 499140 ext. 130; address: Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK

© Woodhead Publishing Limited, 2011

Woodhead Publishing Series in Food Science, Technology and Nutrition: Number 209

Postharvest biology and technology of tropical and subtropical fruits Volume 4: Mangosteen to white sapote

Edited by Elhadi M. Yahia

© Woodhead Publishing Limited, 2011

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Published by Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK www.woodheadpublishing.com Woodhead Publishing, 1518 Walnut Street, Suite 1100, Philadelphia, PA 19102-3406, USA Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com First published 2011, Woodhead Publishing Limited © Woodhead Publishing Limited, 2011. Chapter 15 was prepared by US government employees; this chapter is therefore in the public domain and cannot be copyrighted. The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials. Neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Control Number: 2011929803 ISBN 978-0-85709-090-4 (print) ISBN 978-0-85709-261-8 (online) ISSN 2042-8049 Woodhead Publishing in Food Science, Technology and Nutrition (print) ISSN 2042-8057 Woodhead Publishing in Food Science, Technology and Nutrition (online) The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. Cover image: Fruit stand in Malaysia (Photo: Elhadi M. Yahia). Typeset by RefineCatch Limited, Bungay, Suffolk Printed by TJI Digital Limited, Padstow, Cornwall, UK

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Contents

Contributor contact details .......................................................................... Woodhead Publishing Series in Food Science, Technology and Nutrition ..... Foreword ......................................................................................................

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1 Mangosteen (Garcinia mangostana L.)............................................... S. Ketsa, Kasetsart University, Thailand and R. E. Paull, University of Hawaii at Manoa, USA 1.1 Introduction................................................................................. 1.2 Fruit development and postharvest physiology .......................... 1.3 Maturity and quality components ............................................... 1.4 Preharvest factors affecting fruit quality .................................... 1.5 Postharvest handling factors affecting quality ............................ 1.6 Physiological disorders ............................................................... 1.7 Pathological disorders ................................................................. 1.8 Harvesting practices.................................................................... 1.9 Postharvest operations ................................................................ 1.10 Processing ................................................................................... 1.11 Conclusions................................................................................. 1.12 Acknowledgements..................................................................... 1.13 References...................................................................................

1

2 Melon (Cucumis melo L.)..................................................................... M. E. Saltveit, University of California, Davis, USA 2.1 Introduction................................................................................. 2.2 Fruit development and postharvest physiology .......................... 2.3 Maturity and quality components and indices ............................ 2.4 Preharvest factors affecting fruit quality .................................... 2.5 Postharvest handling factors affecting fruit quality ....................

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Contents 2.6 2.7 2.8 2.9 2.10 2.11 2.12

Physiological disorders ............................................................... Pathological disorders ................................................................. Insect pests and their control ...................................................... Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

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3 Nance (Byrsonima crassifolia (L.) Kunth).......................................... O. Duarte, National Agrarian University, La Molina, Peru 3.1 Introduction................................................................................. 3.2 Fruit development and postharvest physiology .......................... 3.3 Maturity and quality components and indices ............................ 3.4 Preharvest factors affecting quality ............................................ 3.5 Postharvest handling factors affecting quality ............................ 3.6 Physiological disorders ............................................................... 3.7 Pathological disorders ................................................................. 3.8 Insect pests and their control ...................................................... 3.9 Postharvest handling practices .................................................... 3.10 Processing ................................................................................... 3.11 Conclusion .................................................................................. 3.12 References...................................................................................

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4 Noni (Morinda citrifolia L.) ................................................................. A. Carrillo-López, Autonomous University of Sinaloa, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico 4.1 Introduction................................................................................. 4.2 Fruit growth, development and maturation ................................ 4.3 Preharvest conditions and postharvest handling factors affecting quality .......................................................................... 4.4 Pathological disorders ................................................................. 4.5 Insect pests and their control ...................................................... 4.6 Postharvest handling practices .................................................... 4.7 Processing ................................................................................... 4.8 Conclusions................................................................................. 4.9 References...................................................................................

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5 Olive (Olea europaea L.) ...................................................................... C. H. Crisosto and L. Ferguson, University of California, USA and G. Nanos, University of Thessaly, Greece 5.1 Introduction................................................................................. 5.2 Fruit development and postharvest physiology .......................... 5.3 Maturity and quality components and indices ............................ 5.4 Postharvest handling factors affecting quality ............................ 5.5 Physiological disorders ...............................................................

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Contents 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14

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Pathological disorders ................................................................. Insect pests and their control ...................................................... Harvest operations ...................................................................... Packinghouse handling practices ................................................ Grades and standards for processed olives ................................. Recommended storage and shipping conditions......................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

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6 Papaya (Carica papaya L.)................................................................... S. P. Singh, Curtin University of Technology, Australia and D. V. Sudhakar Rao, Indian Institute of Horticultural Research, India 6.1 Introduction................................................................................. 6.2 Fruit development and postharvest physiology .......................... 6.3 Maturity indices .......................................................................... 6.4 Preharvest factors affecting fruit quality .................................... 6.5 Postharvest factors affecting fruit quality ................................... 6.6 Physiological disorders ............................................................... 6.7 Postharvest pathological disorders ............................................. 6.8 Postharvest insect pests and phytosanitary treatments ............... 6.9 Postharvest handling practices .................................................... 6.10 Processing ................................................................................... 6.11 Conclusions................................................................................. 6.12 References...................................................................................

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7 Passion fruit (Passiflora edulis Sim.) .................................................. W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain and G. Fischer, National University of Colombia, Colombia 7.1 Introduction................................................................................. 7.2 Preharvest factors affecting fruit quality .................................... 7.3 Postharvest physiology and quality ............................................ 7.4 Postharvest handling factors affecting quality ............................ 7.5 Crop losses .................................................................................. 7.6 Processing ................................................................................... 7.7 Conclusions................................................................................. 7.8 References................................................................................... 8 Pecan (Carya illinoiensis (Wangenh.) K. Koch.)................................ A. A. Gardea and M. A. Martínez-Téllez, Research Center for Food and Development, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico 8.1 Introduction.................................................................................

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Nutritional value of pecan nuts ................................................... Harvesting, handling and storage ............................................... Current quality grading system ................................................... In-shell and shelled pecan ........................................................... Description of main quality attributes ........................................ Storage ........................................................................................ Postharvest physiology factors affecting nut quality .................. Potential improvements in handling ........................................... Processing ................................................................................... Conclusions................................................................................. Acknowledgements..................................................................... References...................................................................................

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9 Persimmon (Diospyros kaki L.) ........................................................... A. B. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand and R. Ben-Arie, Israel Fruit Growers’ Association, Israel 9.1 Introduction................................................................................. 9.2 Fruit development and postharvest physiology .......................... 9.3 Maturity, quality at harvest and phytonutrients .......................... 9.4 Preharvest factors affecting postharvest fruit quality ................. 9.5 Postharvest handling factors affecting fruit quality .................... 9.6 Physiological disorders ............................................................... 9.7 Pathological disorders ................................................................. 9.8 Insect pests and their control ...................................................... 9.9 Postharvest handling practices .................................................... 9.10 Processing ................................................................................... 9.11 Conclusions................................................................................. 9.12 References...................................................................................

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10 Pineapple (Ananas comosus L. Merr.) ................................................ A. Hassan and Z. Othman, Malaysian Agricultural Research and Development Institute (MARDI), Malaysia and J. Siriphanich, Kasetsart University, Kamphang Saen, Thailand 10.1 Introduction................................................................................. 10.2 Fruit development and postharvest physiology .......................... 10.3 Physical and biochemical changes during maturation and ripening ................................................................................ 10.4 Preharvest factors affecting fruit quality .................................... 10.5 Postharvest factors affecting quality ........................................... 10.6 Physiological disorders ............................................................... 10.7 Pathological disorders ................................................................. 10.8 Insect pests and their control ...................................................... 10.9 Postharvest handling practices ....................................................

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Processing ................................................................................... Conclusions................................................................................. Acknowledgements..................................................................... References...................................................................................

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11 Pistachio (Pistacia vera L.) .................................................................. M. Kashaninejad, Gorgan University of Agricultural Sciences and Natural Resources, Iran and L. G. Tabil, University of Saskatchewan, Canada 11.1 Introduction................................................................................. 11.2 Physiological disorders ............................................................... 11.3 Postharvest pathology and mycotoxin contamination ................ 11.4 Postharvest handling practices .................................................... 11.5 Processing of fresh pistachio nuts............................................... 11.6 Processing of dried pistachio nuts .............................................. 11.7 References...................................................................................

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12 Pitahaya (pitaya) (Hylocereus spp.) .................................................... F. Le Bellec and F. Vaillant, Centre for Agricultural Research and Development (CIRAD), France 12.1 Introduction................................................................................. 12.2 Uses and market .......................................................................... 12.3 Botany, origin and morphology .................................................. 12.4 Cropping system ......................................................................... 12.5 Cultivation techniques ................................................................ 12.6 Pests and diseases ....................................................................... 12.7 Quality components and indices ................................................. 12.8 Postharvest handling factors affecting quality ............................ 12.9 Processing ................................................................................... 12.10 Conclusions................................................................................. 12.11 References...................................................................................

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13 Pitanga (Eugenia uniflora L.) .............................................................. M. Vizzotto and L. Cabral, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil and A. Santos Lopes, Federal University of Pará, Brazil 13.1 Introduction................................................................................. 13.2 Postharvest physiology ............................................................... 13.3 Maturity and quality components and composition.................... 13.4 Postharvest handling factors affecting quality ............................ 13.5 Postharvest handling practices .................................................... 13.6 Processing ................................................................................... 13.7 Conclusions................................................................................. 13.8 References...................................................................................

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14 Pomegranate (Punica granatum L.).................................................... M. Erkan, Akdeniz University, Turkey and A. A. Kader, University of California, Davis, USA 14.1 Introduction................................................................................. 14.2 Fruit development and postharvest physiology .......................... 14.3 Maturity and quality components and indices ............................ 14.4 Preharvest factors affecting fruit quality .................................... 14.5 Postharvest handling factors affecting quality ............................ 14.6 Physiological disorders ............................................................... 14.7 Pathological disorders ................................................................. 14.8 Postharvest handling practices .................................................... 14.9 Processing ................................................................................... 14.10 Conclusions................................................................................. 14.11 References...................................................................................

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15 Rambutan (Nephelium lappaceum L.) ................................................ M. M. Wall, US Department of Agriculture, Agricultural Research Service (USDA-ARS), USA, D. Sivakumar, Tshwane University of Technology, South Africa and L. Korsten, University of Pretoria, South Africa 15.1 Introduction................................................................................. 15.2 Fruit development and postharvest physiology .......................... 15.3 Maturity and quality components and indices ............................ 15.4 Preharvest factors affecting fruit quality .................................... 15.5 Postharvest handling factors affecting quality ............................ 15.6 Physiological disorders ............................................................... 15.7 Pathological disorders ................................................................. 15.8 Insect pests and their control ...................................................... 15.9 Postharvest handling practices .................................................... 15.10 Processing ................................................................................... 15.11 Conclusions................................................................................. 15.12 References...................................................................................

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16 Salak (Salacca zalacca (Gaertner) Voss) ............................................ S. Supapvanich, Kasetsart University, Thailand, R. Megia, Bogor Agricultural University, Indonesia and P. Ding, University of Putra Malaysia, Malaysia 16.1 Introduction................................................................................. 16.2 Fruit development and postharvest physiology .......................... 16.3 Changes in quality components during maturation .................... 16.4 Preharvest factors affecting fruit quality .................................... 16.5 Postharvest factors and physiological disorders affecting fruit quality ................................................................................. 16.6 Postharvest pathology and entomology ...................................... 16.7 Postharvest handling practices ....................................................

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16.8 Processing ................................................................................... 16.9 Conclusions................................................................................. 16.10 References...................................................................................

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17 Sapodilla (Manilkara achras (Mill) Fosb., syn Achras sapota, L.) ... E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 17.1 Introduction................................................................................. 17.2 Fruit development and postharvest physiology .......................... 17.3 Maturity and quality components and indices ............................ 17.4 Preharvest factors affecting fruit quality .................................... 17.5 Postharvest handling factors affecting quality ............................ 17.6 Physiological disorders ............................................................... 17.7 Pathological disorders ................................................................. 17.8 Insect pests and their control ...................................................... 17.9 Postharvest handling practices .................................................... 17.10 Processing ................................................................................... 17.11 Conclusions................................................................................. 17.12 References...................................................................................

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18 Soursop (Annona muricata L.) ............................................................ M. A. Coêlho de Lima and R. E. Alves, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil 18.1 Introduction................................................................................. 18.2 Fruit growth and ripening ........................................................... 18.3 Maturity and quality components and indices ............................ 18.4 Preharvest factors affecting fruit quality .................................... 18.5 Postharvest handling factors affecting quality ............................ 18.6 Physiological disorders ............................................................... 18.7 Pathological disorders ................................................................. 18.8 Postharvest handling practices .................................................... 18.9 Conclusions................................................................................. 18.10 References................................................................................... 19 Star apple (Chrysophyllum cainito L.) ................................................ E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 19.1 Introduction................................................................................. 19.2 Fruit development and postharvest physiology .......................... 19.3 Maturity and quality components and indices ............................ 19.4 Preharvest factors affecting fruit quality .................................... 19.5 Postharvest handling factors affecting quality ............................ 19.6 Physiological disorders ............................................................... 19.7 Pathological disorders ................................................................. 19.8 Insect pests and their control ......................................................

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Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

20 Sugar apple (Annona squamosa L.) and atemoya (A. cherimola Mill. × A. squamosa L.) ................................................ C. Wongs-Aree, King Mongkut’s University of Technology Thonburi (KMUTT), Thailand and S. Noichinda, King Mongkut’s University of Technology North Bangkok (KMUTNB), Thailand 20.1 Introduction................................................................................. 20.2 Fruit development and postharvest physiology .......................... 20.3 Maturity ...................................................................................... 20.4 Preharvest factors affecting fruit quality .................................... 20.5 Postharvest handling factors affecting quality ............................ 20.6 Physiological disorders ............................................................... 20.7 Diseases, insect pests and their control....................................... 20.8 Postharvest handling practices .................................................... 20.9 Processing ................................................................................... 20.10 Conclusions................................................................................. 20.11 Acknowledgements..................................................................... 20.12 References...................................................................................

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21 Tamarillo (Solanum betaceum (Cav.)) ................................................ W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain, A. East, Massey University, New Zealand and A. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand 21.1 Introduction................................................................................. 21.2 Preharvest factors affecting fruit quality .................................... 21.3 Postharvest physiology and quality ............................................ 21.4 Postharvest handling factors affecting quality ............................ 21.5 Crop losses .................................................................................. 21.6 Processing ................................................................................... 21.7 Conclusions................................................................................. 21.8 References...................................................................................

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22 Tamarind (Tamarindus indica L.) ....................................................... E. M. Yahia, Autonomous University of Queretaro, Mexico and N. K.-E. Salih, Agricultural Research Corporation, Sudan 22.1 Introduction................................................................................. 22.2 Fruit growth and ripening ........................................................... 22.3 Maturity and quality components and indices ............................ 22.4 Preharvest factors affecting fruit quality .................................... 22.5 Diseases and pests and their control ...........................................

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Contents 22.6 22.7 22.8 22.9 22.10

Postharvest handling factors affecting quality ............................ Postharvest handling practices .................................................... Processing ................................................................................... Conclusions................................................................................. References...................................................................................

23 Wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry) and related species .......................................................... Z.-H Shü, Meiho University, Taiwan, C.-C. Hsieh and H.-L. Lin, National Chung-hsing University, Taiwan 23.1 Introduction................................................................................. 23.2 Fruit development and postharvest physiology .......................... 23.3 Maturity, quality components and indices .................................. 23.4 Physiological disorders ............................................................... 23.5 Pathological disorders ................................................................. 23.6 Insect pests and their control ...................................................... 23.7 Postharvest handling practices .................................................... 23.8 Conclusions................................................................................. 23.9 References...................................................................................

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24 White sapote (Casimiroa edulis Llave & Lex) ................................... E. M. Yahia and F. Guttierrez-Orozco, Autonomous University of Queretaro, Mexico 24.1 Introduction................................................................................. 24.2 Fruit development and postharvest physiology .......................... 24.3 Maturation and quality components and indices ........................ 24.4 Preharvest factors affecting fruit quality .................................... 24.5 Postharvest handling factors affecting quality ............................ 24.6 Physiological disorders ............................................................... 24.7 Pathological disorders ................................................................. 24.8 Insect pests and their control ...................................................... 24.9 Postharvest handling practices .................................................... 24.10 Processing ................................................................................... 24.11 Conclusions................................................................................. 24.12 References...................................................................................

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Index.............................................................................................................

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Contributor contact details Chapter 3

(* = main contact) Chapter 1 S. Ketsa* Department of Horticulture Faculty of Agriculture Kasetsart University Bangkok, 10900 Thailand

O. Duarte Universidad Nacional Agraria – La Molina Monte Real 207, Dept. 7 Chacarilla, Surco Lima 33 Peru Email: [email protected]

Email: [email protected] R. E. Paull Department of Tropical Plant and Soil Sciences University of Hawaii at Manoa Honolulu, HI 96822 USA Email: [email protected] Chapter 2 M. E. Saltveit Mann Laboratory Department of Plant Sciences University of California Davis, CS 95616 USA

Chapter 4 A. Carrillo López* Maestría en Ciencia y Tecnología de Alimentos Facultad de Ciencias QuímicoBiológicas Universidad Autónoma de Sinaloa Blvd de las Américas s/n Culiacán Sinaloa, C. P. 80000 México Email: [email protected] [email protected]

Email: [email protected]

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Contributor contact details

E. M. Yahia Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida de las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México

D. V. Sudhakar Rao Division of Postharvest Technology Indian Institute of Horticultural Research Hessaraghatta Lake Bangalore, 560 089 India

Email: [email protected]

Email: [email protected]

Chapter 5

Chapter 7

C. H. Crisosto* and L. Ferguson Department of Plant Sciences University of California, Davis One Shields Avenue Davis, CA 95616 USA

W. C. Schotsmans* Department of Postharvest Science Institut de Recerca i Tecnologia Agroalimentàries Avenida de Alcalde Rovira Roure 191 25198 Lleida Spain

Email: [email protected] [email protected]

Email: [email protected]

G. Nanos School of Agricultural Sciences University of Thessaly Fitoko Str 38446 Volos Greece

G. Fischer Facultad de Agronomía Universidad Nacional de Colombia A. A. 14490, Av. Carr. 30 No. 45–03 Bogotá Colombia

Email: [email protected]

Email: [email protected]

Chapter 6

Chapter 8

S. P. Singh* Department of Environment and Agriculture Curtin University of Technology GPO Box U1987 Perth 6845 Australia

A. A. Gardea* Unidad Guaymas Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a Varadero Nacional km 6.6. Guaymas, Sonora, 85480 Mexico

Email: sukhvinder.pal.singh@gmail. com

Email: [email protected]

© Woodhead Publishing Limited, 2011

Contributor contact details M. A. Martínez-Téllez Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a la Victoria, km 0.6 Hermosillo, Sonora, 83000 México Email: [email protected] E. M. Yahia Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México Email: [email protected]

Chapter 10 A. Hassan* and Z. Othman Malaysian Agricultural Research and Development Institute (MARDI) GPO Box 12301 50774 Kuala Lumpur Malaysia Email: [email protected] J. Siriphanich Department of Horticulture Faculty of Agriculture Kamphaeng Saen Kasetsart University Nakhon Pathom, 73140 Thailand Email: [email protected]

Chapter 9

Chapter 11

A. B. Woolf* The New Zealand Institute for Plant and Food Research Mt Albert Private Bag 92169 Auckland Mail Centre 1142, Auckland New Zealand Email: [email protected] R. Ben-Arie Fruit Storage Research Laboratory Israel Fruit Growers’ Association Kiryat Shemona 10200, Israel Email: [email protected]

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M. Kashaninejad* Department of Food Science and Technology Gorgan University of Agricultural Sciences and Natural Resources Beheshti Avenue Gorgan 49137-15739 Iran Email: [email protected] [email protected] L. G. Tabil Department of Chemical and Biological Engineering University of Saskatchewan 57 Campus Drive Saskatoon SK S7N 5A9 Canada Email: [email protected]

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Contributor contact details

Chapter 12 F. Le Bellec* CIRAD, UPR 103 HORTSYS TA B-103/PS4, Boulevard de la Lironde 34398 Montpellier Cedex 5 France Email: [email protected] F. Vaillant CIRAD, UMR 95 QUALISUD TA B-95/16, 73 rue Jean François Breton 34398 Montpellier Cedex 5 France Email: [email protected] Chapter 13

L. Cabral Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Food Technology Av. das Américas, 29501 Guaratiba, Rio de Janeiro CEP 23020-470 Brazil Email: [email protected] Chapter 14 M. Erkan* Department of Horticulture Faculty of Agriculture Akdeniz University 07059 Antalya Turkey Email: [email protected]

M. Vizzotto* Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Temperate Agricultural Rodovia BR 392, km 78 Pelotas RS – Brazil – CEP 96010-971 Email: marcia.vizzotto@cpact. embrapa.br

A. A. Kader Department of Plant Sciences University of California, Davis CA 95616 USA Email: [email protected] Chapter 15

A. S. Lopes Federal University of Pará (UFPA) College of Food Engineering Rua Augusto Corrêa 01, Guamá Belem, PA CEP 66075-110 Brazil

M. M. Wall* US Department of Agriculture Agricultural Research Service P.O. Box 4459 Hilo Hawaii 96720 USA

Email: [email protected]

Email: [email protected]

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Contributor contact details D. Sivakumar Department of Crop Sciences Tshwane University of Technology Pretoria 0001 South Africa Email: [email protected] L. Korsten Department of Microbiology and Plant Pathology University of Pretoria Pretoria 0002 South Africa Email: [email protected] Chapter 16 S. Supapvanich* Faculty of Natural Resources and Agro-Industry Chalermprakiat Sakonnakhon Province Campus Kasetsart University 59 Chiangkhrua, Muang Sakonnakhon Province 47000 Thailand Email: [email protected] R. Megia Department of Biology-FMIPA Bogor Agricultural University Darmaga Campus Bogor 16680 Indonesia Email: [email protected]

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P. Ding Department of Crop Science Faculty of Agriculture Universiti Putra Malaysia 43400 UPM Serdang, Selangor Malaysia Email: [email protected] Chapters 17, 19 and 24 E. M. Yahia* and F. Guttierrez-Orozco Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México Email: [email protected]; [email protected] Chapter 18 M. A. Coêlho de Lima* Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Tropical Semi-Arid BR 428 Km 152 P. O. Box 23 56302-970, Petrolina Pernambuco State Brazil Email: [email protected] R. E. Alves Brazilian Agricultural Research Corporation (EMBRAPA) Embrapa Tropical Agroindustry Dra Sara Mesquite Street, 2270 60511-110, Fortaleza Ceará State Brazil Email: [email protected]

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Contributor contact details

Chapter 20 C. Wongs-Aree* Postharvest Technology Program School of Bioresources and Technology King Mongkut’s University of Technology Thonburi (KMUTT) Bangkok 10140 Thailand

A. B. Woolf The New Zealand Institute for Plant and Food Research Limited Mt Albert Research Centre Private Bag 92169 Mt Albert New Zealand Email: allan.woolf@plantandfood. co.nz

Email: [email protected] S. Noichinda Faculty of Applied Science King Mongkut’s University of Technology North Bangkok (KMUTNB) Bangkok 10800 Thailand

Chapter 22 E. M. Yahia* Facultad de Ciencias Naturales Universidad Autónoma de Querétaro Avenida las Ciencias S/N Juriquilla, 76230 Querétaro, Qro México

Email: [email protected] Email: [email protected] Chapter 21 W. C. Schotsmans* Department of Postharvest Science Institut de Recerca I Tecnologia Agroalimentàries Avenida de Alcalde Rovira Roure 191 25198 Lleida Spain Email: [email protected]

N. K.-E. Salih Forestry Research Center Agricultural Research Corporation P. O. Box 7089 Khartoum Sudan Email: [email protected] Chapter 23

A. East Centre for Postharvest and Refrigeration Research Massey University Private Bag 11222 Palmerston North 4442 New Zealand

Z.-H. Shü* Research Institute of Health and Biotechnology and Department of Science and Technology Meiho University Neipu, Pingtung 912 Taiwan

Email: [email protected]

Email: [email protected]

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Contributor contact details C.-C. Hsieh Department of Horticulture National Chun-hsing University Taichung 400 Taiwan

H.-L. Lin Department of Horticulture National Chung-Hsing University Taichung 400 Taiwan

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Email: [email protected]

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134 Microbiological analysis of red meat, poultry and eggs Edited by G. Mead 135 Maximising the value of marine by-products Edited by F. Shahidi 136 Chemical migration and food contact materials Edited by K. Barnes, R. Sinclair and D. Watson 137 Understanding consumers of food products Edited by L. Frewer and H. van Trijp 138 Reducing salt in foods: practical strategies Edited by D. Kilcast and F. Angus 139 Modelling microorganisms in food Edited by S. Brul, S. Van Gerwen and M. Zwietering 140 Tamime and Robinson’s Yoghurt: science and technology Third edition A. Y. Tamime and R. K. Robinson 141 Handbook of waste management and co-product recovery in food processing Volume 1 Edited by K. W. Waldron 142 Improving the flavour of cheese Edited by B. Weimer 143 Novel food ingredients for weight control Edited by C. J. K. Henry 144 Consumer-led food product development Edited by H. MacFie 145 Functional dairy products Volume 2 Edited by M. Saarela 146 Modifying flavour in food Edited by A. J. Taylor and J. Hort 147 Cheese problems solved Edited by P. L. H. McSweeney 148 Handbook of organic food safety and quality Edited by J. Cooper, C. Leifert and U. Niggli 149 Understanding and controlling the microstructure of complex foods Edited by D. J. McClements 150 Novel enzyme technology for food applications Edited by R. Rastall 151 Food preservation by pulsed electric fields: from research to application Edited by H. L. M. Lelieveld and S. W. H. de Haan 152 Technology of functional cereal products Edited by B. R. Hamaker 153 Case studies in food product development Edited by M. Earle and R. Earle 154 Delivery and controlled release of bioactives in foods and nutraceuticals Edited by N. Garti 155 Fruit and vegetable flavour: recent advances and future prospects Edited by B. Brückner and S. G. Wyllie 156 Food fortification and supplementation: technological, safety and regulatory aspects Edited by P. Berry Ottaway 157 Improving the health-promoting properties of fruit and vegetable products Edited by F. A. Tomás-Barberán and M. I. Gil 158 Improving seafood products for the consumer Edited by T. Børresen 159 In-pack processed foods: improving quality Edited by P. Richardson 160 Handbook of water and energy management in food processing Edited by J. Klemeš, R. Smith and J-K Kim 161 Environmentally compatible food packaging Edited by E. Chiellini 162 Improving farmed fish quality and safety Edited by Ø. Lie 163 Carbohydrate-active enzymes Edited by K-H Park 164 Chilled foods: a comprehensive guide Third edition Edited by M. Brown 165 Food for the ageing population Edited by M. M. Raats, C. P. G. M. de Groot and W. A Van Staveren 166 Improving the sensory and nutritional quality of fresh meat Edited by J. P. Kerry and D. A. Ledward 167 Shellfish safety and quality Edited by S. E. Shumway and G. E. Rodrick 168 Functional and speciality beverage technology Edited by P. Paquin

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198 Freeze-drying of pharmaceutical and food products T-C Hua, B-L Liu and H Zhang 199 Oxidation in foods and beverages and antioxidant applications Volume 1: understanding mechanisms of oxidation and antioxidant activity Edited by E. A. Decker, R. J. Elias and D. J. McClements 200 Oxidation in foods and beverages and antioxidant applications Volume 2: management in different industry sectors Edited by E. A. Decker, R. J. Elias and D. J. McClements 201 Protective cultures, antimicrobial metabolites and bacteriophages for food and beverage biopreservation Edited by C. Lacroix 202 Separation, extraction and concentration processes in the food, beverage and nutraceutical industries Edited by S. S. H. Rizvi 203 Determining mycotoxins and mycotoxigenic fungi in food and feed Edited by S. De Saeger 204 Developing children’s food products Edited by D. Kilcast and F. Angus 205 Functional foods: concept to product Second edition Edited by M. Saarela 206 Postharvest biology and technology of tropical and subtropical fruits Volume 1 Edited by E. M. Yahia 207 Postharvest biology and technology of tropical and subtropical fruits Volume 2 Edited by E. M. Yahia 208 Postharvest biology and technology of tropical and subtropical fruits Volume 3 Edited by E. M. Yahia 209 Postharvest biology and technology of tropical and subtropical fruits Volume 4 Edited by E. M. Yahia 210 Food and beverage stability and shelf life Edited by D. Kilcast and P. Subramaniam 211 Processed Meats: improving safety, nutrition and quality Edited by J. P. Kerry and J. F. Kerry 212 Food chain integrity: a holistic approach to food traceability, safety, quality and authenticity Edited by J. Hoorfar, K. Jordan, F. Butler and R. Prugger 213 Improving the safety and quality of eggs and egg products Volume 1 Edited by Y. Nys, M. Bain and F. Van Immerseel 214 Improving the safety and quality of eggs and egg products Volume 2 Edited by F. Van Immerseel, Y. Nys and M. Bain 215 Feed and fodder contamination: effects on livestock and food safety Edited by J. Fink-Gremmels 216 Hygienic design of food factories Edited by J. Holah and H. L. M. Lelieveld 217 Technology of biscuits, crackers and cookies Fourth edition Edited by D. Manley 218 Nanotechnology in the food, beverage and nutraceutical industries Edited by Q. Huang 219 Rice quality K. R. Bhattacharya 220 Meat, poultry and seafood packaging Edited by J. P. Kerry 221 Reducing saturated fats in foods Edited by G. Talbot 222 Handbook of food proteins Edited by G. O. Phillips and P. A. Williams 223 Lifetime nutritional influences on cognition, behaviour and psychiatric illness Edited by D. Benton

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Foreword

Most published postharvest research on fruit, covering decades of activity, has concentrated on temperate or model crops. There are good reasons for this, mainly associated with the well-established production and marketing industries, and long-established research teams in Europe, North America and Australasia. This great effort has given us much of our current understanding of fruit ripening, the characterisation of ethylene as a growth regulator, far reaching fundamental knowledge on core issues in plant science such as respiration, cell wall metabolism, aroma volatiles, and more latterly, on genetic and molecular control of fruit properties. This work has particularly provided the technology which has allowed a remarkable level of control of fruit quality after harvest, and provided the mainstay for substantial economic gains at the levels of both industry and national economies. However, estimates of world fruit production (2005–07) show that tropical crops including citrus make up to about 60% of world major fruit crop production (World Kiwifruit Review, 2010). In conjunction with this, the volume of global exports of tropical and subtropical fruit is about twice that of temperate fruit crops (data for 2007, for instance, show about 19 million tonnes for temperate and 38 million tonnes for tropical/subtropical produce; FAOSTATS database). Such crops comprise a major part of the economies of tropical and subtropical countries, and some such as bananas, plantains and breadfruit, are staple foods with critical dietary components. While the scale and importance of this in itself would warrant an extensive research base, one of the most compelling issues for postharvest researchers is the level of food waste. Various analyses of wastage along the value chain have been made, but the consensus seems to be that in developing countries, where most of the tropical and subtropical crops are grown, food losses can amount to up to 50% or more. A breakdown of this (Kader, 2005; World Economic Forum, 2009) suggests that most waste occurs between harvest and retail, with low percentages of food loss at the consumer end of the chain.

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Foreword

This provides an immediate target for postharvest research, and there is some urgency on this, given current concerns over food security in the next few decades (Nature, 2010). There will be collateral benefits. The most important may well be in increasing export potential of crops that traditionally have short storage lives and that are easily damaged during transport and handling. Even increasing access to near markets will provide economic gain, but there is greater potential in targeting more affluent markets and consumers who are seeking a wider range of fruit types and eating experiences, and are prepared to pay more for them. There are other advantages. Optimised postharvest procedures will result in greater maintenance of the nutritive and calorific value of fruit crops by minimising physiological deterioration and that from pests and diseases. And now that sustainability has become a serious market issue, there are environmental impacts from reducing food loss. For instance, there have been estimates that water losses associated with food wastage could reach a level where up to half the original water supply from irrigation is lost (World Economic Forum, 2009). So how will postharvest research on tropical and subtropical fruit crops help? We have to know our commodities, and the contents of this book directly addresses this. Understanding the fruit crop, fruit development, when to harvest, the specific ripening process, and postharvest response, is critical to optimising postharvest storage and handling. We tend, however, to try to impose traditional postharvest practices on all crops, often when this is not appropriate. Low temperature storage is an obvious case, and tropical crops particularly are chillingly sensitive: there is a constant struggle to prolong storage life through temperature control with a recalcitrant commodity. Many improvements in quality control through the supply chain can be made for a lot of crops with very simple application of basic postharvest handling and storage practices. These target pest and diseases, disinfestation issues, and ways of reducing the rate of fruit ripening while increasing tolerance to storage and transport conditions. However, we can be more innovative. In most cases, there has been relatively little done in breeding and selection of tropical and subtropical fruit crops with postharvest quality attributes as targets. There is a lot of scope here, particularly in the new genomics era, where faster and smarter breeding can be undertaken, and more value extracted from existing genetic material. There is quite a lot of research currently underway on tackling tropical fruit problems through fresh cut technology, and the use of edible coatings and biofilms, to prolong storage and shelf life. While this may have a minor impact on local use and in decreasing food wastage in less urban environments and markets, there may be larger benefits for urban and export markets. There is also an approach that might require extra thought and greater interrogation of the properties of the particular crops. Instead of imposing highly technical storage conditions, understanding how the fruit responds to ambient conditions and then seeing if there are innovative ways of handling the crop under those conditions might be more economical and practical under less sophisticated systems. The history of postharvest suggests that local innovation has often been

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very effective and perhaps we have been persuaded to look at modern technology at the expense of more original thinking. We need robust knowledge of our crops, and then very targeted postharvest approaches to reducing waste and ensuring high market quality. This is not a choice, but is an imperative for local economies, and for future food security. Ian Ferguson The New Zealand Institute for Plant & Food Research

References FAOSTATS database. Kader A A (2005) Increasing food availability by reducing postharvest losses of fresh produce. Acta Hortic, 682, 2169–2175. (2010) The growing problem. Nature, 466, 456–561. World Economic Forum (2009) Driving sustainable consumption. Value chain waste: Overview briefing. World Kiwifruit Review (World Kiwifruit Review).

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1 Mangosteen (Garcinia mangostana L.) S. Ketsa, Kasetsart University, Thailand and R. E. Paull, University of Hawaii at Manoa, USA

Abstract: Mangosteen (Garcinia mangostana L.) is one of the most admired tropical fruit and known widely as the Queen of Fruits for its beautiful purple blue pericarp and delicious flavor. The edible aril is white, soft and juicy with sweet pleasant taste. Mangosteen is a climacteric fruit that undergoes rapid postharvest changes resulting in a short shelf life at ambient temperature. Physiological disorders induced by preharvest and postharvest factors have a major impact on the appearance and eating quality. In addition to fresh consumption, the aril is processed into other products. The fruit pericarp also contains many chemical compounds that have possible medicinal value. Key words: mangosteen, postharvest change, physiological disorder, postharvest handling quality.

1.1

Introduction

1.1.1 Origin, botany, morphology and structure The mangosteen (Garcinia mangostana L.) originated in Southeast Asia and is a member of the family Clusiaceae. In earlier works, the genus had been placed in the Guttiferae. The genus name Garcinia was given by Linnaeus in honor of French naturalist Laurent Garcin for his work as a botanist in the eighteenth century. Laurent Garcin with others had made one of the most detailed descriptions of the fruit. Although the word ‘mango’ occurs in the word ‘mangosteen’ there is no botanical relationship at the genus or family levels. The name mangosteen is thought to have been derived from Malay or Javanese. According to Verheij (1991: 443): The mangosteen as a fresh fruit is in great demand in its native range and is savored by all who find its subtle flavors a refreshing balance of sweet and sour. It should be pointed out that Asians consider many foods to be either ‘cooling’ such as the mangosteen or ‘heating’ such as the durian depending on whether they possess

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Postharvest biology and technology of tropical and subtropical fruits elements that reflect yin and yang. This duality is commonly used to help describe balance in many aspects of life in general and food in particular throughout Asia.

Morton (1987: 505) describes the mangosteen as follows: The mangosteen is a very slow-growing, erect tree with a pyramidal crown. The tree can attain 6 to 25 m (20 to 82 ft) and has dark-brown or nearly black, flaking bark, the inner bark containing much yellow, gummy, bitter latex. This evergreen has opposite, short-stalked leaves that are ovate-oblong or elliptic, leathery and thick, dark-green, slightly glossy above and yellowish-green and dull beneath. New leaves have a rosy hue. The mature leaves are 9 to 25 cm long (3 1/2 to 10 in) and 4.5 to 10 cm wide (1 3/4 to 4 in) with conspicuous, pale midribs. Female flowers are 4 to 5 cm wide (1 1/2 to 2 in). The flowers are borne singly or in pairs at the tips of young branchlets; their fleshy petals may be yellowish-green, edged with red or mostly red, and the petals are quickly shed.

No male flowers or trees have been described, though it is said to be dioecious. Mangosteen is only known as a female cultivated plant. Based on morphological characters, mangosteen may be a sterile allopolyploid hybrid (2n = 88 − 90) between two Garcinia spp. Morton (1987: 505) further describes that: the smooth round fruit, 3.4 to 7.5 cm in diameter (1 1/3 to 3 in), is capped by a prominent calyx at the stem end that has 4 to 8 triangular, flat remnants of the stigma in a rosette at the apex. When the fruit is mature and ripe, it is dark-purple to reddishpurple. The rind (pericarp) is 6 to 10 mm thick (1/4 to 3/8 in) and spongy and in cross-section is red outside and purplish-white on the inside. The pericarp has a bitter yellow latex, and a purple, staining juice. Inside the pericarp are 4 to 8 triangular segments of snow-white, juicy, soft edible flesh (aril) that clings to the seeds. The fruit may be seedless or have 1 to 5 fully developed seeds. The seeds are ovoid-oblong, somewhat flattened, 2.5 cm (1 in) long and 1.6 cm wide (5/8 in).

The edible aril is white, juicy, sweet and slightly-acid, with a pleasant flavor (Fu et al., 2007; Ji et al., 2007). It is similar in shape and size to a tangerine. The circle of wedge-shaped arils contains 4 to 8 segments, the larger of which contain the apomictic seeds that are unpalatable unless roasted. Fruit are harvested at various stages of ripeness, referred to as Stage 1 to Stage 6. During ripening, Hue angle and pericarp firmness decline significantly, while soluble solids contents (SSC) increases and titratable acidity (TA) decreases resulting in an increase of SSC : TA ratio, and better tasting fruit. Fruit harvested at Stage 1 and allowed to ripen to Stage 6 show no significant differences in sensory quality and fruit appearance to fruit harvested at Stage 6. In the absence of fertilization, asexual ovary nucellus tissue development occurs that ensures fruit and aril growth. The asexual embryos develop from the nucellus tissue and these apomixic ‘seed’ are used in propagation. The ‘seed’ is a clone of the mother plant with little variation (Richards, 1990; Ramage et al., 2004), but the absence of true seed associated with sexual fertilization limits varietal development and selection. DNA and RNA marker analysis from material sourced globally has shown variation among the different mangosteen populations.

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The majority of the samples had essentially the same genetic make-up (genotype) but significant differences were found in same samples (Yapwattanaphun and Subhadrabandhu, 2004). This difference could be due to chance mutation or selection within the limited variation that is known to occur. 1.1.2 Worldwide importance Mangosteen fruit is now grown worldwide and is being exported and marketed in more developed countries. Often it is advertised and marketed as a novel functional food and is sometimes called a ‘super fruit’. It is presumed to have a combination of

• • • •

appealing characteristics, such as taste, fragrance and visual qualities, nutrient richness, antioxidant strength, and potential impact for lowering risk of human diseases (Gross and Crown, 2007).

1.1.3 Nutritional value and health benefits The aril, though having a pleasant taste and flavor, has a low nutrient content (Table 1.1). Recent research on antioxidant determination showed that plant foods with rich colors had high scores of oxygen radical absorbance capacity (ORAC) whereas those that were white (without pigments) had low ORAC (Wu et al., 2004). Following this simple and subjective index, the white mangosteen aril Table 1.1 Nutritional values of mangosteen fruit (per 100 g edible portion). Content

per 100 g edible portion

Water Energy Protein Fat Carbohydrate Dietary fiber Ash Calcium Phosphorus Iron Copper Zinc B1 (Tiamine) B2 (Riboflavin) Niacin Vitamin C

80.9 g 76.0 cal 0.5 g 0.2 g 18.4 g 1.7 g 0.2 g 9.0 mg 14.0 mg 0.5 mg 0.11 mg 0.1 mg 0.09 mg 0.06 mg 0.1 mg 2.0 mg

Source: Anon. (2004). Fruits in Thailand. Department of Agricultural Extension, Ministry of Agriculture and Cooperatives, Bangkok, Thailand.

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should have a low ORAC, though no ORAC results have been reported for the aril to date. Some mangosteen juice products contain whole fruit purée or polyphenols extracted from the inedible pericarp (rind) as a formulation strategy to add phytochemical value. The resulting juice has a purple color and astringency derived from pericarp pigments. Xanthone extracts taken from the pericarp (Jung et al., 2006) and added to a juice could be beneficial (Anon, 2007). Apha-mangostin, a xanthone, can stimulate apoptosis in leukemia cells in vitro (Matsumoto et al., 2004). The preliminary nature of this research means that no definite conclusions can be drawn about possible health benefits for humans eating mangosteen.

1.2

Fruit development and postharvest physiology

1.2.1 Fruit growth, development and maturation At fruit set, fruit shape is almost spherical, with fruit length and width being almost equal and remaining so throughout the fruit growth (Fig. 1.1). Width and length increase slowly during the first two weeks after flowering then increase rapidly up to week 5 and more slowly thereafter. Fresh weight showed a similar pattern of growth, slow during the first two weeks and rapidly increasing. Aril fresh weight increased steadily from week 2 until the end of week 12 when it was 29% of the whole fruit (Wanichkul and Kosiyachinda, 1979a). Surprisingly, pericarp thickness

Fig. 1.1 Changes in length (●), width ({), fresh weight (∆), pericarp thickness (▲) and soluble solids (■) content in aril (…) of mangosteen fruit during growth and development (Wanichkul and Kosiyachinda, 1979a).

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changed only slightly between weeks 2 and 12. The data also suggested that growth was mainly expansion rather than cell division after week 2. Mangosteen fruit take about 12 weeks from fruit set to maturity that can vary about one week (Wanichkul and Kosiyachinda, 1979b). This small variation in maturation time is not commercially significant as growers can harvest fruit at a range of maturities. Fruit can be harvested as early as Stage 1 when fruit are light greenish-yellow with 5–10% scattered pink spots that ripen to acceptable eating quality at room temperature. The earlier Stage 0, when the fruit are yellowish-white or yellowish-white with light-green, are also considered mature though the aril eating quality is inferior to fruit harvested at Stage 1 and later (Palapol et al., 2009a). 1.2.2 Respiration, ethylene production and ripening Ripening fruit exhibits a respiratory climacteric pattern (Noichinda, 1992; Piriyavinit, 2008). The respiratory rate of fruit harvested at Stage 0 and ripened at 25 °C is about 10 ml/kg-h rising to about 30 ml/kg-h at the climacteric peak on day 4 and then falls to about 18 ml/kg-ml on day 7 (Fig. 1.2). Stage 0 fruit treated with exogenous ethylene treatment have an earlier climacteric respiratory rise. The higher the concentration of ethylene applied, the sooner the climacteric respiration occurs. The respiratory peak of Stage 0 fruit occurs on day 4 and when treated with 1, 10 and 100 uL/L ethylene on days 2.6, 2 and 1.5 with respiration rate at 26, 30, 31 and 32.5 ml/kg-h, respectively. Mechanical impact also increases the respiration rate of the fruit, the greater the impact the greater respiratory rate increases (Noichinda, 1992).

Fig. 1.2

Respiration (∆), ethylene production (…) and internal concentrations of ethylene (●) in mangosteen fruit harvested at Stage 0 (Noichinda, 1992).

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Ethylene production during ripening is delayed compared to the rise in respiration (Fig. 1.2). The rise in ethylene begins to increase after day 4 with the peak occurring after the respiratory peak on day 6.5, and then declines. The initial rate of ethylene production on day 1 for Stage 0 fruit is about 2 ul/kg-h and at the maximum about 14 ul/kg-h. The internal ethylene concentration at Stage 0 on day 1 is about 0.75 ppm, increasing to 2.5 ppm on day 2.5 and rapidly increases to a maximum of about 19 ppm by day 6 (Noichinda, 1992). The increase in ethylene production by whole fruit and the aril parallels a similar increase in 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity by the fruit aril. The aril ACO activity largely explains the ethylene production data, while possible additional 1-aminocyclopropane-1-carboxylic acid synthase (ACS) activity occurs in the pericarp. Fruit stored at 15 °C showed an ethylene production peak on day 1, which is a few days earlier than the maximum found in fruit stored at 25 °C. The rapid appearance of the ethylene peak in fruit stored at 15 °C is likely associated with chilling injury. As the storage duration at 15 °C increases, the changes in ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) levels, and the activities of ACS and ACO occur later than in fruit held at 25 °C. The pericarp of fruit stored at 15 °C and treated with 1-MCP have reduced activity of both ACS and ACO (Piriyavinit, 2008). Pericarp color change is coincident with the changes in respiration and ethylene production (Noichinda, 1992). The climacteric rise starts on day 2 as the fruit turns from to a light-greenish yellow with 51–100% scattered pink spots (Stage 2) (see Plate I in the colour section between pages 238 and 239). Pericarp color develops rapidly from Stage 2 to Stage 3 (reddish-pink), 4 (red to reddish-purple), 5 (dark purple) and 6 (purple black) within five or six days, depending on temperature. Fruit firmness also sharply decreases when fruit turns reddish-pink on day 3. The TSS: TA ratio and eating quality of fruit ripened to Stage 3 are not significantly different from fruit ripened to Stages 5 and 6. Consumers prefer to eat fruit ripened to Stage 5 or 6 as the fruit pericarp of Stage 4 fruit is still firm and is difficult to remove by hand (Palapol et al., 2009a). 1.2.3 Color development The pericarp color development occurs both on and off the tree. Tongdee and Suwanagul (1989) developed a skin color index scale for mangosteen maturity that is divided into 6 Stages (see Plate I in the colour section). Stage 0 fruit are yellowish white or yellowish white with light green, changing to light greenishyellow with 5–50% scattered pink spots at Stage 1. When the fruit are light greenish-yellow with 51–100% scattered pink spots is Stage 2, to when the spots are not as distinct as in Stage 2 or reddish-pink is Stage 3. Later stages are when red to reddish-purple (Stage 4), dark purple (Stage 5) and purple-black (Stage 6). Fruit harvested at Stage 0 develop skin color the same as fruit ripened on tree at Stage 6. Fruit when harvested at Stage 1, 2, 3, 4 and 5 reach Stage 6 in 6, 5, 4, 3, 2 and 1 days at 25 °C, respectively (Palapol et al., 2009a). Ratanamarno (1998) reported that mangosteen fruit at Stage 1 when stored at low temperatures (15 °C)

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changed to Stage 6 later than fruit stored at 35 °C and fruit stored at room temperature (30 °C). After transferring fruit stored at 15 °C to 25 °C, the red coloration (Hue value) and anthocyanin content increased rapidly and the increase correlated closely with an increase in ethylene production (Palapol et al., 2009a). Color development in mangosteen pericarp is closely correlated with the increase total anthocyanins (Fig. 1.3). The rapid increase in anthocyanin suggests that the precursors are readily available for conversion to cyanidins. No other pigments appear to contribute to skin color.

Fig. 1.3 (a) Cross section of mangosteen pericarp showing outer pericarp (OP) and inner pericarp (IP). The bar denotes 2 mm. (b) Hue values (▲) of skin color and total anthocyanin contents of inner (■) and outer (…) mangosteen pericarp during color development from light greenish yellow with 5% scattered pink spots to purple black (Stages 1–6) (Palapol et al., 2009a).

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The increase in total anthocyanin contents of the inner pericarp tissue follows the same trend as the outer pericarp though with a lower Hue value and total anthocyanin content. Hue value is a good objective measure of fruit maturity (Palapol et al., 2009a). The anthocyanins in the outer pericarp have been separated and identified by HPLC/MS. The five compounds reported are cyanidin-sophoroside, cyanidinglucoside, cyanidin-glucoside-pentoside, cyanidin-glucoside-X, cyanidin-X2 and cyanidin-X, where X denotes an unidentified residue of m/z 190. The 190 mass does not correspond to any common sugar residue. Cyanidin-3-sophoroside and cyanidin-3-glucoside are the major compounds and the only ones that increased with fruit color development (Fig. 1.4). The anthocyanin biosynthesis pathway has several key steps. The mangosteen anthocyanin biosynthesis genes GmPAL to G23mUFGT have been completely characterized (Palapol et al., 2009b). GmPAL to G23mUFGT all belong to multigene families and show sequence similarity to anthocyanin related genes in many other plants including several fruit. The transcript levels of the three mangosteen MYBs, GmMYB1, GmMYB7 and GmMYB10, increased markedly with onset of red coloration both on-tree and after harvest (Fig. 1.5). GmMYB10 is the most

Fig. 1.4 Anthocyanin profiles in outer pericarp of mangosteen fruit harvested at Stage 1 to 6 (light greenish yellow with 5% scattered pink spots to purple black) during color development. Peak identity was as follows: (1) cyaniding-sophoroside, (2) cyanidingglucosider-pentoside, (3) cyanidin-glucoside and cyanin-glucoside-X (overlapping peak), (4) cyaniding-X2, and (5) cyaniding-X. X denotes a residue of m/z 190 which has not been identified (Palapol et al., 2009a).

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Fig. 1.5 Transient activation of the mangosteen and Arabidopsis DFR promoter by GmMYBs, AtPAPl, and AtbHLH2 transcription factors. All TFs were co-infiltrated with DFR-Luc promoter in transient tobacco transformation assays. The dual luciferase (LUC) to 35S Renilla (REN), where an increase in activity equates to an increase in LUC relative to REN (Hellens et al., 2005). Error bars are the means ± SE for four replicate reactions (Palapol et al., 2009a).

up-regulated of the GmMYB transcription factors (299-fold on the tree and 501-fold postharvest fruit at Stage 5 – (dark purple)) and declines at Stage 6 (black purple) (Fig. 1.5). This expression pattern is similar to that of MdMYB10 in apple (Espley et al., 2007) and VvMYBPA1 in grape berry skins (Bogs et al., 2007). The expression patterns suggest that GmMYB10 is a potential candidate to regulate anthocyanin biosynthesis in mangosteen fruit. The expression pattern of all anthocyanin biosynthesis genes correlated with that of GmMYB10, in expression changes and with onset of color development, and declines in synthesis at the final stages. Mangosteen fruit color changes correlate well with ethylene production. Treatment with the ethylene receptor inhibitor 1-MCP delays the increase in Hue value (red), ethylene production and anthocyanin accumulation. In both 1-MCP and ethylene plus1-MCP treatments, 1-MCP down-regulates the expression of GmMYB genes, especially GmMYB10, and the anthocyanin biosynthetic genes. This correlative data gives strong support to the conclusion that ethylene and the expression of the GmMYB10 transcription factors closely control anthocyanin biosynthesis in mangosteen (Palapol et al., 2009b). Direct data is needed to show that ethylene directly regulates GmMYB10 and all anthocyanin biosynthesis genes at the transcription level. Though 1-MCP delays ethylene production, exogenous ethylene does not induce ethylene and anthocyanin production (Piriyavinit, 2008; Palapol et al., 2009b).

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Ethylene application also does not increase the expression anthocyanin biosynthetic and MYB transcription genes (Palapol et al., 2009b). Mangosteen fruit stored at 15 °C developed fruit color more slowly than the fruit stored at 25 °C (Palapol, 2009a). Storage of fruit at 15 °C, besides having delayed color development and ethylene production, inhibits the transcript levels of all anthocyanin biosynthetic genes that increased in abundance when transferred to 25 °C (Palapol et al., 2009b). Maybe the failure to see an ethylene response is because ethylene sensitivity is changing (increasing) during ripening. 1.2.4 Softening Pericarp firmness declines sharply from Stage 1 at 779.3 to 46.5 N at Stage 6 (Palapol et al., 2009a). The softening of the pericarp and also the aril parallels fruit ripening. As ripening starts, the fruit pericarp changes from uniform green to the development of red spots while the aril remains firm and connected to the pericarp. As the fruit ripens further to the pericarp having dark purple at an overripe stage, the aril becomes soft and juicy, and easily separates from the pericarp. Aril firmness declines slowly at room temperature between day 0 and day 4, and then shows a sharp change from day 4 to day 10 as the fruit develop full pericarp purple color. At 13 °C, aril firmness changes little over the 10 days of ripening. The water soluble pectin content in aril increased more rapidly at room temperature than when held at 13 °C. Aril insoluble pectin content declines during ripening with a sharp change between day 4 and day 8, while both pectin methylesterase and polygalacturonase activities increase more rapidly when held at room temperature than at 13 °C. This data suggest that changes in cell wall solubilization may be responsible for aril softening during ripening (Noichinda et al., 2007). The difference in firmness of mangosteen aril held at different temperatures reflects a correlation between water soluble pectin and activities of pectin methylesterase and polygalacturonase. However, high pectin methylesterase activity is detected at harvest (day 0) while polygalacturonase activity increases after harvest when held at both temperatures (Noichinda et al., 2007). This result suggests that pectin methylesterase (PME) may not have access to pectin during early fruit ripening and polygaloturonase (PG) does not increase until later when cell wall changes allow esterase activity and provision for de-esterified substrate for PG.

1.3

Maturity and quality components

Fruit color is the major criterion used to judge maturity and for grading of mangosteen fruit. The fruit are usually harvested at different stages according to color, from light greenish-yellow with scattered pink spots to dark purple. After harvest, the purple color continues to develop very quickly. For high fruit quality, the minimum harvest color stage is that of a fruit with distinct irregular, pink-red spots over the whole pericarp surface. If fruit are harvested with a light greenishyellow with scattered pink spots, the fruit do not ripen to full flavor (Tongdee and Suwanagul, 1989; Paull and Ketsa, 2004).

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Table 1.2 Time, quality and sensory evaluation of mangosteen fruit harvested at Stage 1 (A) and allowed to ripen at 25 °C, or harvested at the six different maturity stages and measurements made when the fruit reached Stage 6 (B). Fruit Time Firmness (N) a*/b* ratio stage (d) A B A B

% SSC A

B

A

B

A

B

B

1 2 3 4 5 6

15.2c 15.3bc 16.3ab 16.6a 17.1a 17.2a

17.2 17.3 17.5 17.9 17.5 17.4

0.77bc 0.78b 0.84a 0.80ab 0.79b 0.73c

0.81 0.81 0.80 0.78 0.75 0.74

19.8bc 19.6bc 19.3c 20.8bc 21.7ab 23.7a

21.2b 21.3b 21.9ab 23.0ab 23.5a 23.7a

4.2 3.7 3.8 4.0 3.7 4.1

0 1 2 3 5 9

6.66a 5.30b 4.91c 4.59d 4.20e 3.84f

44.8 0.03b 43.6 0.44b 46.0 1.16b 42.9 2.28b 45.0 3.71b 47.9 16.69a

11.06b 12.09ab 12.10ab 10.04b 9.63b 13.95a

% TA

SSC/TA

Sensory

Source: Palapol et al. (2009a). Notes: The firmness values in column A are log (In) transformed data, with original data from Stage 1 to 6, being 779.3, 201.3, 136.0, 98.4, 66.5 and 46.5 N, respectively. Means within any column followed by the same letter are not significantly different (P > 0.05).

Postharvest fruit quality is generally dependent on the stage of maturity at harvest. Fruit harvested at Stages 1 to 6 and allowed to ripen to Stage 6 showed no significant differences in fruit quality or sensory characteristics (Table 1.2). This suggests that ripening had already initiated before harvest of Stage 1 fruit but not Stage 0. This ripening habit provides considerable harvest flexibility allowing the Thai grower to harvest fruit for export at Stage 1 (light greenish yellow with 5% scattered pink spots) that develop full flavor and have a slightly longer shelf-life over fruit harvested at later stages. The Malaysian harvest guideline for mangosteen export is similar to Thailand, being reddish-yellow with patches of red (Osman and Milan, 2006).

1.4

Preharvest factors affecting fruit quality

Like other fruit crops, fruit quality depends on many preharvest factors. However, only a few preharvest factors are considered to have significant impact on fruit quality after harvest. 1.4.1 Location Orchard on soils with poor drainage or a low slope favors the occurrence of translucent aril and ‘gamboges’ (Laywisadkul, 1994; Chutimunthakun, 2001). ‘Gamboges’ is a physiological disorder that leads to the occurrence of yellow latex exudate on the pericarp surface and occasionally the aril. Therefore, growers seek land for growing mangosteen trees that has good drainage and also higher slope. Over watering of trees can also result in translucent aril and ‘gamboge’. 1.4.2 Fertilizer Application of complete chemical fertilizers plus calcium and zinc, during fruit growth plays an important role in ensuring high yield and quality of mangosteen

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fruit. Good fertilization practice can also reduce the occurrence of translucent aril and gamboge. Fertilizer is applied at least three times during vegetative growth, again pre-flowering and lastly during fruit development (Sdoodee et al., 2006). 1.4.3 Pests Thrips are considered to be the most important insect pests. They feed on young fruit with the scars becoming obvious at fruit maturation concomitant with the change from green to reddish and purple (see Plate II(A) in the colour section). Typical symptoms include silvering of fruit skin, pale yellow/brown discoloration, elongated and patchy scars or hardened scars, and ‘alligator skin’ like scars that may cover the entire fruit surface (see Plate II(A) in the colour section). Heavily scarred skin can sometimes prevent normal fruit growth (Affandi and Emilda, 2009). Fruit from outside the canopy are more likely to have thrips damage than those inside the canopy (Sdoodee et al., 2006). According to Affandi and Emilda (2009), several thrips control methods used for other fruit can be adopted for mangosteen. For example, botanical pesticides such as ‘Sabadilla’ derived from the seeds of Schoenocaulon officinale, as well as biopesticides such as abamectin and spinosad can be used (Hoddle et al., 2002; Wee et al., 1999; Faber et al., 2000; Astridge and Fay, 2006). Other cultural control techniques used to reduce thrips population are composted organic yard waste, composted mulch applied under plant canopy, and augmentation of predatory thrips Franklinothrips orizabensis, F. vespiformis and Leptothrips mc-cornnelli (Hoddle et al., 2002; Wee et al., 1999). The University of California Statewide Integrated Pest Management Program (2006) suggested integrated pest management (IPM) for controlling thrips. Such a plan would include the optimal use of natural enemies, removing all weeds under the canopy to eradicate alternative hosts, regular pruning of infected trees, use of a fluorescent yellow sticky trap, and application of reflective mulch to disturb host plant orientation of the thrips. Use of fluorescent yellow sticky traps is limited for monitoring the population of thrips due to the cost of adhesive glues such as the one called tangle foot (Chu et al., 2006). Chemical insecticide should be used as a last alternative. If necessary, monochrotophos, methiocarb or carbosulfan can be applied in mangosteen orchards to control thrips. After harvest, thrip-damaged fruit can be coated with carnauba or shellac waxes that results in a better appearance. The appearance of damaged fruit after coating resembles that of normal fruit (Phongsopa et al., 1994). This practice is used by Thai exporters.

1.5

Postharvest handling factors affecting quality

1.5.1 Temperature management The rapid ripening of mangosteen fruit at ambient temperatures is accompanied by shriveling of the calyx. The pericarp color changes and calyx shriveling result

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in the loss of marketability within a few days. Temperature management is essential to prolong shelf life. Storage of fruit at low temperature is commonly used to maintain quality and extend shelf life, because low temperature reduces the rate of respiration, ethylene production and other metabolic processes (Wills et al., 1998). Mangosteen can be stored at 12–13 °C and have a shelf life of about three weeks with acceptable eating quality (Choehom et al., 2003). Storage at 4 or 8 °C can lead to significant pericarp hardening, although the aril may still be acceptable after 44 days (Augustin and Azudin, 1986). When stored at 4 to 8 °C, surface coatings can reduce weight loss, prevent calyx wilting and assist in maintaining appearance. Dipping the calyx and the stem end of the fruit in various concentrations of hormones (e.g., BA, GA3 and NAA) before storage at 12 °C also delays shriveling and extends the storage period (Choehom et al., 2003). 1.5.2 Physical damage The surface of the mangosteen pericarp consists of a continuous epidermis layer covered by cuticular wax with lenticels. The epidermis covers a thick layer of parenchyma tissue and inner strip of sclereids (Phongsopa et al., 1994). The spongy pericarp serves as an excellent packing material to protect the soft aril during transportation. However, mechanical injury due to compression or impact injury, common in handling, results in some pericarp hardening (Tongdee and Sawanagul, 1989; Ketsa and Koolpluksee, 1992). Mechanical injury induced firmness increase occurs within three hours of the injury to both reddish and dark purple fruit. The firmness increase in injured dark purple fruit occurs more rapidly than that to reddish brown fruit. Regardless of fruit maturity, holding fruit in a nitrogen atmosphere after injury significantly inhibits the firmness increase compared to fruit held in air (Bunsiri et al., 2003). The firmness that develops is directly related to the height from which the fruit are dropped, the higher the drop height, the greater the firmness that occurs in the damaged pericarp (Tongdee and Sawanagul, 1989; Bunsiri et al., 2003). Thrips caused the greatest percentage of fruit surface scarring (46.7%) preharvest, while pericarp hardening is a harvest and postharvest handling problem which at the consumers’ home can affect 33% of the fruit. Pushpariksha (2008) summarized the impact on postharvest quality of mechanical injury as pericarp cracking, surface scarring, pericarp hardening, aril translucency, gamboge and decay. 1.5.3 Water loss The thrip-damaged epidermis at anthesis leads to the formation of a periderm layer as the fruit develops. These thrip-damaged fruits have a higher weight loss rate of 2.23% per day after harvest, compared to 1.63% per day for undamaged fruit (Phongsopa et al., 1994). Weight loss also induces pericarp hardening similar to the pericarp hardening associated with chilling injury (Dangcham et al., 2008), whereas impact induces pericarp hardening only in the damaged area (Bunsiri et al., 2003). Calyx and stem end shrivel are related to weight loss and results in

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poor postharvest appearance (Choehom et al., 2003). When stored at 13 °C (89–90% RH), weight loss of up to 6.8% can occur in 18 days, while coated fruit lose about 4% (Noichinda, 1992). Wax application reduces weight loss during storage at both ambient and low temperatures (Noichinda, 1992; Phongsopa et al., 1994; Choehom et al., 2003). Plant growth regulators such as BA, GA3 and NAA applied in combination or alone prior to storage, delays calyx and stem end shriveling (Choehom et al., 2003). 1.5.4 Atmosphere and coatings The recommended controlled atmosphere storage conditions are 13 °C, with 10–15% carbon dioxide and 2% oxygen (Pakkasarn, 1997). Aryucharoen (2004) confirmed the 13 °C storage temperature but recommended 3–5% carbon dioxide and 2% oxygen. For maximum storage life Wichitrananon (2001) found that fruit stored at 13 °C are still acceptable after 42 days when stored in 0% carbon dioxide and 0% oxygen. Fruit wrapped with polyethylene and polyvinyl chloride films and stored at 13 °C had almost twice the storage life of fruit stored without wraps (Pranamornkij, 1997). Ratanatraiphop (2003) reported that fruit coated with Stra-fresh #7055, glucomanan, chitosan and methylecellulose reduced weight loss, softening and pericarp color change, respiration rate and ethylene production during storage at 15 °C and had a storage life of 28 to 32 days, while the control fruit had storage life of 24 days. Similarly, Chanloy (2006) reported that fruit coated with 1% methylcellulose and 1000 mg/l GA, placed into polyethylene bags with 3% carbon dioxide or without polyethylene bags and stored at 13 °C had storage life of 32 and 28 days, respectively, compared to 24 days for the control.

1.6

Physiological disorders

1.6.1 Chilling injury The symptoms of CI in mangosteen fruit included darkening and hardening of the pericarp (Kader, 2007). These symptoms occur when fruit are moved to higher temperatures following storage at less than 10 °C for longer than 15 days or more than five days at 5 °C. Decay susceptibility also increases at chilling temperatures. The aril may still have acceptable quality after 44 days at 4 to 8 °C (Augustin and Azudin, 1986). Pericarp hardening is the most common symptom of CI in mangostee fruit (Uthairatanakij and Ketsa, 1996; Ponrod, 2002; Choehom et al., 2003). Fruit stored at 6 °C had greater pericarp firmness than those stored at 12 °C and the more mature (reddish purple) fruit had greater firmness than less mature (reddish brown) fruit. The unacceptable CI symptom of pericarp hardening of mangosteen fruit is found within 5, 10 and 20 days after storage at 3, 6 and 12 °C, respectively (Choehom et al., 2003). The pericarp hardening is more pronounced after storage at 6 °C for nine days and then transferred to room temperature (29.5 °C) for three days.

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The lower the storage temperature the sooner pericarp hardening develops (Uthairatanakij, 1995; Uthairatanakij and Ketsa, 1996; Kosiyachinda, 1986; Dangcham et al., 2008). Pericarp hardening is associated with an increase in lignin content (Uthairatanakij and Ketsa, 1996; Dangcham et al., 2007). A negative correlation exists between total free phenolics and lignin contents, and pericarp firmness and is similar to that found in mangosteen fruit after impact (Ketsa and Atantee, 1998; Bunsiri et al., 2003). Lignin accumulation is also found in cherimoya fruit after prolonged storage at chilling temperature (Maldonado et al., 2002). Cai et al. (2006) reported that the firmness of loquat fruit increases during postharvest ripening and is positively correlated with lignin accumulation in the flesh tissue. Lignification is a process that also occurs in secondary wall formation and under special conditions such as wounding, pathogen attack or fungal elicitor treatment (Vance et al., 1980; Ride, 1983). The degree of mangosteen pericarp hardening due to CI is related to the activity of enzymes involved in phenolic metabolism. The decrease in phenolic occurs concomitantly with the increased firmness and lignin contents in mangosteen pericarp stored at low temperature and suggests that phenolics may be incorporated into lignin. The resulting incorporation leads to an increase in pericarp lignin contents and hardening. The turnover of phenolics in mangosteen fruit subject to chilling temperature may be more rapid than their synthesis resulting in decline in phenolics (Dangcham et al., 2008). Total free phenolics declined and lignin contents increased more rapidly in the more mature reddish purple fruit than in reddish brown fruit and was greater in fruit stored at lower temperatures (Dangcham et al., 2007). Total free phenolics declines throughout storage whereas phenylalanine ammonia lyase (PAL) activity slightly increases only at the end of storage. This result suggests that phenolics are being incorporated into lignin at the start of storage and that CI induced an increase in PAL. The increase in pericarp firmness following storage at 6 °C is about 16-fold, while the lignin contents increase about 1.75-fold. This difference in increase suggests that the increase in lignin contents alone may not fully explain the rapid increase in pericarp firmness after low temperature storage. Lignins are found in both the free and bound state in plant cell walls (Morrison, 1974) and participate in cross-linking cell wall polysaccharides (Kondo et al., 1990; Lam et al., 1994; Ralph et al., 1995). Ester linkage occurs between glycosyluronic groups and the lignin hydroxyl groups, and ether linkage between polysaccharides and lignins (Iiyama et al., 1994; Lawoko, 2005). In addition, linkages are formed between lignin and proteins (Keller et al., 1988; Whetten et al., 1998). In plant tissues, lignin synthesis is correlated with activities of many enzymes such as PAL, cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) (Lewis and Yamamoto, 1990). The increased firmness of loquat fruit (Cai et al., 2006) and bamboo shoot (Luo et al., 2007) is a consequence of lignification, and associated with an increase of PAL, CAD and POD activities. PAL is an important enzyme required for synthesis of phenolic compounds that catalyses the conversion of L-phenylalanine to trans-cinnamic acid, a precursor of various phenylpropanoids,

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such as lignins, coumarins and flavonoids (Hahlbrock and Scheel, 1989; Lewis and Yamamoto, 1990; Schuster and Retey, 1995). Chilling temperatures can generally stimulate the biosynthesis of phenolic compounds by enhancing PAL activity (Aquino-Bolaños et al., 2000). PAL activity has been reported to be involved with CI development in many plants such as ‘Fortune’ mandarin, pineapple and ‘Navelate’ oranges (Martínez-Téllez and Lafuente, 1993; SanchezBallesta et al., 2000; Zhou et al., 2003; Sala et al., 2005). PAL activity of fresh-cut asparagus also increased in the first 10 days, before decreasing during the latter period of storage concomitant with lignin content (An et al., 2007). These results are similar to the findings in mangosteen fruit stored at 6 °C. PAL mRNA accumulates at start of storage at 6 °C and then decreases. The increase in mangosteen PAL gene expression at low temperature occurs prior to the increased PAL activity, lignin accumulation and pericarp hardening (Dangcham et al., 2008). The accumulation of PAL mRNA initially without an increase in PAL activity and phenolic levels, might be the result of low temperature stress, while the accumulation when fruit are transferred to room temperature was concomitant with the pericarp hardening (Dangcham et al., 2008). Similarly an increase in LgPOD activity occurs in mangosteen fruit stored at 6 °C then transferred to room temperature. This increase in LgPOD is concomitant with an increase in POD activity, lignin content and pericarp hardening (Dangcham et al., 2008). Low O2 treatment applied during and after low temperature storage of mangosteen fruit does not reduce pericarp hardening. Pericarp firmness and lignin contents still increased under low O2 during storage at 6 °C and at room temperature after transfer from 6 °C. This contrasted previous reports that mangosteen pericarp damaged after impact and fruit stored at low temperature under N2 is not as firm, and had lower lignin contents and more total phenolics than damaged pericarp held in the air (Uthairatanakij, 1995; Ketsa and Atantee, 1998; Bunsiri et al., 2003). Low temperature may exert a greater inhibitory effect on many enzymes involved in lignin synthesis, while a low O2 level only affects the last lignifications step of monolignol polymerization (Imberty et al., 1985). We confirmed this by applying low O2 treatment to stored mangosteen fruit after transfer to room temperature, and this had a greater effect on pericarp hardening than low O2 treatment applied only during low temperature storage. This suggests that low temperature may delay biochemical reactions involved in PAL and POD activities and the metabolic turnover of phenolic would be slower. Upon transfer to room temperature, all biochemical reactions involved in lignin synthesis become more rapid and have a greater O2 requirement. POD activity in mangosteen pericarp is low when stored at 6 °C under low O2 level, but its activity increased after transfer to room temperature. Low O2 levels occur in fruit that have received a wax coating (Peng and Jiang, 2003; Dong et al., 2004) or in modified atmosphere packaging (Shen et al., 2006) and they also have reduced POD activity. POD activity in fruit pericarp after transfer from 6 °C to room temperature under low O2 level is low, while in normal air a small increase occurs. However, low O2 is also found to have no effect on POD activity at the

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end of storage. This confirms the previous idea that low temperature has a greater impact on biochemical changes than low O2 level. Moreover, POD activity in mangosteen fruit stored at 6 °C under low O2 and transferred to room temperature is high while lignin content is low. In contrast, POD activity in mangosteen fruit stored at 6 °C under normal air is low while lignin content is higher after transfer to room temperature. This indicated that O2 is required for the oxidation in the final step of polymerization for lignin synthesis in mangosteen pericarp (Bunsiri et al., 2003a). CAD activity in fruit pericarp does not change during low temperature storage or after transfer to room temperature while pericarp firmness increased. This suggested that CAD may not be a rate-limiting step in lignin synthesis in mangosteen fruit pericarp during low temperature storage. CAD activity in damaged pericarp of mangosteen fruit after impact increases 15 min after impact, concomitant with an increase in lignin synthesis, and CAD activity increases much more than PAL and POD activities (Bunsiri, 2003). The increase in lignin contents in loquat fruit (Cai et al., 2006), copper stress treated Panax ginseng root (Ali et al., 2006) and bamboo shoot (Luo et al., 2007) is associated with CAD activity. Furthermore, CAD activity in transgenic plants (CAD antisense) such as tobacco (Halpin et al., 1994) and poplars (Baucher et al., 1996) is reduced, but the amount of lignin does not change. Thus, CAD might not be related to lignin synthesis and pericarp hardening of mangosteen fruit stored at low temperatures. 1.6.2 Pericarp hardening after impact The firmness increase in mangosteen pericarp following impact is well recognized (Tongdee and Suwanagul, 1989; Ketsa and Atantee, 1998; Uthairatakij and Ketsa, 1996). The increase in damaged pericarp firmness is more rapid in more mature fruit, fruit subjected to a greater drop height, and when oxygen is present than in less mature fruit, lower drop height and low oxygen level. The increased firmness of damaged pericarp occurred concomitantly with an increase of lignin content (Fig. 1.6). Lignin content in damaged pericarp is less under nitrogen atmosphere than under oxygen, as the final step of lignin biosynthesis requires oxygen for the polymerization of monomeric lignin precursors catalyzed by peroxidase. The increase of lignin in damaged pericarp after impact is supported histochemical microscopy and consistent with the increase in thioglycolic lignin (Bunsiri et al., 2003b). Following impact, the firmness of damaged pericarp increased rapidly, concomitantly with an increase in lignin content. The increase in lignin content in damaged pericarp is substantial when compared to the increases in firmness of damaged pericarp, as the basal lignin content in undamaged pericarp is initially high. The increase in firmness of damaged pericarp three hours after impact is 215 to 385%, while the increase in lignin content of damaged pericarp is 150 to 288%, dependent upon fruit maturity and drop height. Lignin-carbohydrate complex (LCC) increase in damaged pericarp of mangosteen fruit and the increase in lignin and carbohydrate contents is greater than that of protein content. The increase in

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Fig. 1.6 Firmness (a) and lignin content (b) of undamaged (■) and damaged (…) pericarp of dark purple mangosteen fruit after physical impact at a drop height of 100 cm. Fruit were held at room temperature (29 °C) before impact (t = 0) or 15, 30, 60, 120 and 180 min after impact. Data are means ± SD of six replicate fruit (Bunsiri, 2003).

lignin, carbohydrate and protein contents in LCC of damaged pericarp requires oxygen (Whetten and Sederoff, 1995; Bunsiri et al., 2003b). A transient, significant increase is found in the activity of PAL, CAD and POD. The activity of PAL increases about four-fold, that of CAD about eight-fold; and POD activity increases about six-fold within 15 min after mechanical impact. The significant increase in activities is found to occur between 10 and 15 minutes after impact, and a considerable decrease in activities is observed between 15 and 20 minutes after impact (Bunsiri, 2003). The data indicates that mechanical impact induces a concomitant increase in the activities of several enzymes involved at the early (PAL) and late stages (CAD and POD) of lignin synthesis. The rapid increase in the activities of PAL, CAD and POD in the pericarp slightly precedes (15 min) a detectable increase in pericarp lignin levels (Fig. 1.7). The increase in the activity of these and other enzymes might therefore be the cause of the increased lignin levels (Boudet, 2000). The present results are similar

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Fig. 1.7 Phenylalanine ammonia lyase (a), cinnamylalcohol dehydrogenase (b) and peroxidase (c) activities of undamaged (…) and damaged (■) pericarp of dark purple mangosteen fruit after physical impact at a drop height of 100 cm. Fruit held at room temperature (29 °C) before impact (t = 0) or 15, 30, 60, 120, 180 min after impact. Data are expressed as units per mg pericarp protein, whereby one unit is defined as the activity to produce 1 μM cinnamic acid within 1 h. Data are means ± SD of six replicate fruit (Bunsiri, 2003).

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to those found in bamboo shoots, where an increase in firmness after harvest was positively correlated with an increase of the contents of lignin and cellulose. The lignin accumulation in the bamboo shoot is positively correlated with an increase in the activities of PAL, CAD and POD (Luo et al., 2007). The rapidity of the increase in enzyme activity (four- to eight-fold increase) in as little as 15 minutes after the mechanical impact indicates that de novo synthesis of the proteins is unlikely. A detectable increase in protein synthesis by an outside stimulus, if involving the activation of genes, usually requires at least one hour (Alberts et al., 2008). The present data suggest that the mechanical impact leads to activation of existing proteins. If so, it is at present unclear how the impact would exert such a post-translational effect. 1.6.3 Translucent aril Translucent aril is a major physiological disorder that develops in the field before harvest. Symptoms are internal and include flesh changes from white to translucent (see Plate II(B) in the colour section) and textural changes from soft to firm and crisp (Pankasemsuk et al., 1996). Heavy and continuous rains during fruit growth and ripening favor translucency development in certain locations where the drainage is poor. The greater the rainfall that occurs at harvest times, the higher the incidence of fruit with translucent arils. The incidence of translucent aril is assumed to be caused by excess water uptake during fruit growth and development. The excess water may penetrate fruit rind, subsequently causing translucent aril (Sdoodee and Limpun-Udom, 2002). Orchards with greater slopes and better drainage have a lower incidence of fruit with translucent aril. Orchards with shallow water tables (1 to 50 cm) also have higher incidence of translucent aril than orchards with deeper water tables (101 to 200 cm) (Chanaweerawan, 2001). Similarly, when mangosteen are irrigated (75 mm per day) for five days during the harvesting, more fruit have translucent aril than trees with normal irrigation (15 to 20 mm per day) (Laywisadkul, 1994). The crucial period when excess rainfall or irrigation can lead to greater incidence of fruit with translucent aril is from about nine weeks after blooming (Chutimunthakun, 2001). The aril that is translucent is firmer than normal, and the translucent aril tissue has twice the amount of damaged protoplasts than normal aril. This is assumed to be due to excessive water uptake causing higher turgor pressure resulting in disruption of plasma membrane and cell death. Subsequently water and solutes leak out from protoplasts to the intercellular space leading to translucent aril (Luckanatinvong, 1996; Dangcham, 2000). Translucent aril has lower alcohol insoluble solids, soluble pectin and CDTA soluble pectin and higher Na2CO3 soluble pectin than normal aril (Dangcham, 2000). The translucent aril also contains higher ratio of K : Ca, K : Mg, and K : Ca+Mg than normal aril (Pludbuntong, 2007). Accumulation of calcium in light-exposed fruit is higher than shaded fruit and the incidence of translucent aril is lower in fruit on the top of the canopy that are light-exposed (Chiarawipa, 2002). The pericarp of non-

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translucent fruit contains higher N, Ca, K, and B contents than fruit with translucent aril (Pechkeo, 2007). Since calcium plays an important role in maintaining cell wall integrity (Helper, 2005), low content of Ca may lead to weaken cell walls of aril that cannot resist the influx of water. Foliar application of calcium chloride and boric acid to mangosteen trees increases the ratio of normal aril to translucent aril fruit (Pechkeo, 2007). Top cutting, soil mulching and foliar application of calcium can also alleviate the incidence of translucent aril (Chiarawipa, 2002), while soil application of complete fertilizers to mangosteen trees prior to full bloom and foliar application of complete fertilizers plus zinc during fruit set can reduce translucency in aril (Jirapat, 2002). 1.6.4 Gamboge Gamboge or gummosis is also a physiological disorder characterized by yellow exudation of gum onto the fruit surface (see Plate II(C) in the colour section). Sometimes yellow gum is also exuded from the inner pericarp into aril surface or between the carpels inside the fruit (see Plate II(C) in the colour section). The aril with the yellow gum tastes bitter, so consumers avoid buying mangosteen fruit with yellow gum on the fruit surface. It is believed that the environmental conditions that cause both translucent aril and gamboge are the same. Heavy and continuous rains during fruit growth and ripening favor gamboge in certain locations where the drainage is poor. However, the evidence that water relations are involved in gamboge is not strong as for aril translucency. An imbalance or deficiency of essential elements in soil and mangosteen tree may also contribute to gamboge (Pechkeo, 2007). Fruit harvested early in the season have a higher incidence of gamboge than fruit harvested late irrespective of the amount of rainfall. Extra irrigation does result in more fruit with gamboge (Laywisadkul, 1994). Even though environmental conditions and nutrient deficiency are believed to be involved in the incidence of gamboges, it is not known how this occurs. Latex in mangosteen fruit is produced by latex cells or laticifer inside the pericarp and exported via laticiferous vessels. Under conditions of the excessive water uptake breakage of laticiferous vessels may occur, which in turn allows yellow gum to leak out from pericarp and this yellow gum moves inward to aril or outwards to the fruit surface. Soil drainage, soil mulching, top pruning and foliar application of calcium, boron and zinc can alleviate gamboge (Chiarawipa, 2002; Jirapat, 2002; Pechkeo, 2007).

1.7

Pathological disorders

Unlike other tropical fruit, pre and postharvest diseases of mangosteen fruit are not a serious problem. This may be due to the pericarps physical and chemical properties. The fruit pericarp is thick and hard, and contain chemicals whose activity can act as antibiotic compounds. Occasionally postharvest diseases are reported for mangosteen fruit such as black aril rot caused by Lasiodiplodia theobromae (Pat.) triffon and Manbl (Botryodiplodia theobromae), white aril rot

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caused by Phomopsis sp. (Sacc.) Bnbak and soft aril rot caused by Pestalotia sp. Seaver. Most of these diseases infect the fruit in orchards and it is recommended to periodically spray with an approved fungicide before harvest (Visanthanon, 1999).

1.8

Harvesting practices

Mature fruit at any stage from Stage 1 to Stage 6 can be harvested depending on the market and purpose. Common practice for growers in Thailand is to pick up fruit at Stage 1 (light greenish yellow with 5–50% scattered pink spots) for export markets, Stage 2 (light greenish yellow with 51–100% scattered pink spots) or Stage 3 (reddish pink) for the local and regional markets. The sensory quality of fruit harvested at Stages 1 to 5 and ripened to Stage 6 is similar to fruit harvested at Stage 6 from the tree (Palapol et al., 2009a). Since mangosteen fruit are prone to pericarp hardening after impact, growers harvest carefully to minimize physical damage using baskets made of linen cloth or nylon net connected to bamboo poles to reach mangosteen fruit high in the tree. Fruit are carefully placed into plastic baskets and then taken to a packinghouse or directly to the markets.

1.9

Postharvest operations

1.9.1 Packinghouse practices Fruit in containers are moved from the orchard to a packinghouse or packing station. The containers must be able to protect the fruit against bruising and abrasion, so fruit should not be packed in containers over 30 cm deep otherwise fruit at the bottom will be subject to compression injury resulting in pericarp hardening. Fruit are culled to separate good fruit without skin damage from fruit with skin and calyx blemish, and sorted so that undersize fruit can be sold in local markets. Fruit are graded based on color according to market requirement for export or local use. After grading, yellow gum on the fruit surface is scrapped off with a knife and pressurized air supply is used to blow insects and dirt from underneath the calyx. Fruit for export are graded by weight and the normal range is 70 to 100 g per fruit, while undersized fruit with and without skin blemish are sold at the local markets. Fruit for export are packed individually into partition sections of single-layered corrugated 5 kg cartons or four fruit are packed into individual foam or plastic trays wrapped with PVC film and packed into a master carton. The latter is better at preserving calyx and stem freshness but increases packing costs. 1.9.2 Control of ripening Mangosteen is a climacteric fruit with a respiratory peak that occurs sooner when fruit are treated with ethylene (Noichinda, 1992). Inhibition of ethylene biosynthesis or ethylene action, therefore, may be effective in slowing down a number of ripening

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processes. A six-hour treatment with 1-MCP delays pericarp color development and aril softening during storage at 25 °C or 15 °C, leading to a longer shelf life (Piriyavinit, 2008). In fruit stored at 25 °C and treated with 1-MCP, the typical pericarp color changes are delayed until about day 6, and the decrease of aril firmness is delayed until day 4. At 15 °C, the pericarp color changes are inhibited until day 15, and the aril firmness only until day 4. Thai exporters have adopted a six-hour 1-MCP fumigation to delay pericarp color change and this provides greater flexibility in handling. Care is needed to avoid high rates of 1-MCP fumigation that can lead to pericarp hardening and fruit that will not be ripened normally. The use of gaseous ethylene and calcium carbide does not stimulate early ripening of mangosteen fruit compared to the control fruit. This suggests that the ripening process has already been induced before Stage 1 (Piriyavinit, 2008) or that the fruit’s sensitivity to ethylene increases during ripening. 1.9.3 Storage recommendation Fruit can be stored at room temperature (28 to 29 °C) for a few days, and their calyx and stem ends will start to become shriveled. The fruit pericarp will also be hardened due to weight loss as the storage time at room temperature is increased. Mangosteen fruit is a tropical fruit which is prone to chilling injury if stored below 10–12 °C (Choehom et al., 2003; Dangcham et al., 2008). This optimum storage temperature of 10–12 °C (85–95% RH) gives a storage life of approximately three weeks with an acceptable aril quality (Choehom, 2003; Noichinda, 1992). Mangosteen fruit can be stored below the optimum temperature for only a few days and must be consumed right after removal from low temperature storage otherwise the fruit pericarp will become hardened due to chilling injury (Dangcham et al., 2008).

1.10

Processing

1.10.1 Fresh-cut Unripe mangosteen fruit are used in the fresh-cut trade and not the ripe stage as used for other fruit. The fresh-cut mangosteen product is crispy with a sweet taste. This product is popular in southern Thailand, one of the main mangosteen growing areas. Mangosteen fruit at Stage 0 (yellowish white or yellowish white with light green) or Stage 1 (light greenish yellow with 5 to 50% scattered pink spots) are chosen and their pericarp is carefully removed from the aril in order to prevent latex from the pericarp contaminating the aril and resulting in aril darkening and a bitter taste. Aril without the pericarp is soaked in lime water solution (calcium hydroxide solution) containing 1% alum + 1% NaCl, or 0.50% citric acid + 0.25% calcium chloride (Kitpipit, 2005) for 30 minutes to prevent browning and softening. Subsequently the aril is washed with clean water, and all arils with blemishes are removed. The whiteness of fresh-cut aril can only be maintained for about five hours and then it changes steadily to an unappealing darker color. Fresh-cut mangosteen is prepared daily to meet demand.

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1.10.2 Paste Ripe or over-ripe mangosteen fruit are used to make a mangosteen paste. Fruit are cleaned and the pericarp removed. Aril with or without seeds is heated and stirred with medium or low heat. Thirty kilograms of mangosteen fruit make about 1 kilogram of paste, which can be processed into leather or candy. The paste with seeds has a nutty taste. 1.10.3 Juice Mangosteen fruit has a high content of antioxidants which are thought to be beneficial for health and this presumed health benefit has meant that mangosteen juice has become increasingly popular. Aril is boiled (2:3, v/v) and filtered to remove the seeds. Sugar and salt are added to the juice to improve flavor and boiled once more. Since the juice is white, it is not regarded as attractive as the fresh intact mangosteen fruit. Therefore, colorant extracted from mangosteen pericarp is added to the juice to improve juice color to be slightly pink. If too much mangosteen colorant is added, the juice tastes astringent due to tannins in the pericarp. The juice is marketed in metal cans, plastic or glass bottles. 1.10.4 Drying The pericarp of ripe or overripe mangosteen fruit is removed. The aril with seeds whose water content is approximately 70% is dried at less than 80 °C for two hours and at 70 °C for eight hours. Aril and seeds become a homogenous mixture after drying and the water content is reduced to approximately 13%. Dried aril tastes sweet and sour and with seeds will also have a nutty taste because of seed kernel. Ten kilograms of mangosteen fruit yields about 1 kilogram of dried product. Since pericarp of mangosteen fruit is rich in chemicals whose properties can be used as medicine, the pericarp can be dried similarly to the aril and kept for future use. Dried pericarp can be also made into powder and kept for medical use. 1.10.5 Freezing Mangosteen fruit at Stages 4 or 5 can be frozen. Fruit without blemish and defects are cut into halves at the equatorial planet and opened to check if the fruit aril is translucent or has no gamboge. Blemish free fruit are then wrapped individually with plastic tape surrounding the cut area and frozen at −40 °C for 120 minutes. If the fruit had not been cut in halves, it takes ~140 minutes to freeze. The frozen fruit must be stored at −20 °C. Sophanodora and Sripongpunkul (1990) reported that arils dipped in the solution containing 0.25% calcium chloride and 0.50% citric acid for one minute before freezing at −30 °C for 220 minutes retained their natural color and were accepted by consumers. 1.10.6 Freeze-dried and other products After the pericarp is removed, the aril can be freeze-dried in a three step process. First, the aril is frozen at −40 to −20 °C for 2 to 6 hours, then held under vacuum

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(10 mtorr) at −20 to 10 °C for 5 to 10 hours. Thirdly, aril is frozen at −10 to 0 °C for 2 to 6 hours. Freeze-dried mangosteen is sealed in aluminum foil-lined plastic bags to prevent moisture absorption and light exposure. The freeze dried product has a shelf life at room temperature of at least six months. Mangosteen fruit can be processed into other products such as wine, vinegar, ice cream, yoghurt and cosmetics.

1.11

Conclusions

Mangosteen fruit is named the Queen of Tropical Fruit due to its attractive appearance and taste. Nowadays mangosteen fruit are consumed worldwide, either fresh or processed, because they have amazing compounds whose properties have a great potential benefit to human health. However, fresh mangosteen fruit are perishable and sensitive to chilling injury and a barrier to marketing. Preharvest fruit disorders for which solutions are not available can lead to significant harvest and postharvest loss.

1.12 Acknowledgements The research cited in this chapter was made possible, in part through financial support from the Thailand Research Fund (TRF) and the Commission on Higher Education, Ministry of Education and Kasetsart University Research and Development Institute (KURDI).

1.13

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Plate I

(Chapter 1) Color development of mangosteen fruit at different stages of growth and development (Palapol, 2009).

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(a)

(b)

(c)

(d)

Plate II (Chapter 1) Fruit damaged by thrips (a), translucent aril (b), gamboge with yellow gum outside on fruit surface (c) and with yellow gum inside on the aril (d) (courtesy of Yossapol Palapol).

Plate III (Chapter 2) Honeydew melons showing a packaging pattern in a cardboard container and symptom of chilling injury (darkening of the skin) (courtesy of Marita Cantwell).

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2 Melon (Cucumis melo L.) M. E. Saltveit, University of California, Davis, USA

Abstract: Melons contribute to the nutritive and aesthetic quality of our diet. When harvested mature, most melons exhibit a climacteric in respiration and ethylene production coincident with ripening (i.e., softening, aroma development). Ethylene antagonists, such as CO2 and 1-methylcyclopropene (1-MCP), can slow ripening. Sugar content usually declines after harvest because of the lack of storage carbohydrates to be hydrolysed into simple sugars. The chilling sensitivity of most melon cultivars precludes their storage below 5 ° to 10 °C, but this sensitivity varies greatly with cultivar and stage of maturity. Fresh-cut melons are increasingly important and present unique postharvest challenges to maintain quality. Key words: melon, postharvest, climacteric, chilling injury, fresh-cut.

2.1

Introduction

2.1.1 Botany, morphology and structure Melons are cucurbits; cultivated species of the Cucurbitacese. This family contains about 750 species in 96 genera that are found mainly in the tropics. Most plants are tendril-bearing vines that produce fleshy fruits derived from an inferior ovary; a pepo. The four major cucurbit crops are cucumber, melon, squash (pumpkin), and watermelon (Table 2.1). This chapter will focus on the postharvest biology and technology of melons (Cucumis melo L.). The specie Cucumis melo is further divided into several botanical varieties or types. The three most important types are cantalupensis, inodorus, and reticulates (Table 2.2) Melons are monoecious or andromonoecious annuals with long trailing vines and round stems. Staminate flowers are borne in axillary clusters on the main stem, while perfect flowers are borne at the first node of lateral branches. The flowers are predominately yellow. The fruit is a multi-carpled berry that is epigynous. Fruits vary in size, shape, rind characteristics, and flesh color depending on variety. Seeds are cream-colored, oval, and on average 10 mm long.

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Postharvest biology and technology of tropical and subtropical fruits Table 2.1 The four major cucurbit crops Common name

Scientific name

Melon Cucumber Watermelon

Cucumis melo L Cucumis sativus L. Citrullus lanatus (Thunb.) Matsum. & Nakai. Cucurbita maxima Duch. Ex Lam. Cucurbita moschata Duch. Ex Poir. Cucurbita pepo L.

Squash, pumpkin Squash, pumpkin Squash, pumpkin Table 2.2

Major groups of melons (Cucumis melo L.)

Scientific name

Characteristics

Cantalupensis

Skin that is rough and warty, not netted. European cantaloupe and Algerian melon.

Inodorus

Canary melon, Casaba, Kolkhoznitsa melon, Hami melon, honeydew, Navajo Yellow, Piel de Sapo/Santa Claus, sugar melon, tigger (tiger) melon, and Japanese melons.

Reticulatus

True muskmelons, with netted skin. Examples include Bailan melon, North American cantaloupe, Galia, Ogen, Persian, Sharlyn melons. Modern crossbred varieties, e.g. Crenshaw (Casaba X Persian), Crane (Japanese X N.A. cantaloupe)

2.1.2 Worldwide importance China produces about 50% of the world’s crop by weight. Turkey and Iran are the next largest melon-producing countries, with the U.S. and Spain rounding out the top five producers. Europe, Central America, and Africa are also important world production centers. In Japan, melons are usually grown in greenhouses. The yield of US Western Shipping melons has remained stable for the last 20 years. In 2008, the total value of US cantaloupe production was $371 million and honeydew production was valued at $68 million. Cantaloupe production was the highest on record since 2003, while honeydew production was the lowest on record since 1992. Combined, all melons made up the third highest ranked vegetable crop in the US behind lettuce and onions. 2.1.3 Culinary uses, nutritional value and health benefits Melons are usually consumed as desserts, snacks, breakfast or picnic foods. Recently, processed melon products (e.g., pre-cut product displays, in-store salad bars) have been developed to appeal to the single serving market and to smaller households. Seedless varieties have also helped spur consumption. Improved harvesting and handling techniques, as well as the development of sweeter hybrid varieties have improved quality and consumer acceptance. However, even under the best conditions, total carotenoids and vitamin C declined after harvest.

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A serving of cantaloupe is about 180 grams (1 cup; 250 ml) and contains 60 calories. There is little fat and only 1 g of protein per serving. The carbohydrates are comprised of 14 g of sugar and 2 g of dietary fiber. The yellow and orange fleshed melons contain beta-carotene (provitamin A), and all melons are good sources of vitamin C. A serving of cantaloupe supplies 120% and 110% of the daily requirements of vitamin A and C, respectively. This food is also a good source of niacin, vitamin B6, folate, and potassium.

2.2

Fruit development and postharvest physiology

2.2.1 Fruit growth, development and maturation After pollination, the kinetics of growth is a simple sigmoid curve with the initial phase of cell division accompanied by small changes in fruit size. Expansion of cells gives rise to a linear increase in size over time. Fruit growth is uniform along all dimensions to produce spherical fruit or predominately along the longitudinal axis to produce oblong fruit. Unlike fruit in which cellular expansion occurs primarily at the floral end, the roughly uniform expansion of melon fruit produces a uniform distribution of minerals throughout the tissue. The dilution of poorly translocated minerals (e.g., calcium) in tissues that expand to a greater extent than others can produce a dilution of essential minerals and make the tissues susceptible to physiological disorders such as blossom end rot in tomatoes and bitter pit in apples. This unequal distribution does not occur in melons, so if any physiological disorders occur (e.g., surface pitting from chilling injury), they are uniformly distributed about the surface. Maturation of the fruit is marked by a reduction and finally a cessation of increases in both size and fresh weight, while the rate of increase in dry weight due to translocation of sugars continues to decline as fruit near full ripeness. An abscission layer forms in the subtending stem in the cantaloupe and muskmelon types, while such a physical abscission zone fails to develop in the inodorus group. However, physiological abscission may occur in all melons even before the start of the development of a physical abscission layer as the result of diminished function of the vascular system (i.e., phloem and xylem) as fruit attain full size and start to ripen. The ease of separation of the fruit at the abscission zone provides an excellent indicator of harvestable maturity. The lack of an abscission zone in honeydew may explain why their maturity at harvest can be so variable. It is difficult to ascertain the level of maturity by a purely visual examination of the exposed honeydew fruit in the field. A gentle tug can easily separate a mature cantaloupe fruit from the vine, while honeydew fruit must be cut from the vine to prevent tearing of the fruit near the point of detachment from the stem. 2.2.2 Respiration, ethylene production and ripening Most melons are climacteric and exhibit elevated rates of respiration and ethylene production coincident with ripening (Fig. 2.1). During normal ripening, melons

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Fig. 2.1 Climacteric rise in respiration and ethylene production in cantaloupe melons left on the vine (attached) or harvested (detached). The arrows indicate when the fruit were harvested or when they naturally abscised (Shellie and Saltveit, 1993).

can produce copious amounts of ethylene which stimulates their further ripening and can affect ethylene sensitive crops stored with them. The stimulation of ethylene production by ethylene is termed auto-catalytic ethylene production. Holding partially ripe cantaloupes and other melons at 15 ° to 20 °C will allow them to produce their own ethylene and develop good eating quality without additional ethylene treatment. In fact, ethylene exposure may promote rapid ripening with the loss of shelf life. Honeydews (and other ‘winter’ melons) are sometimes harvested before they develop the ability to produce enough ethylene to ripen normally. Exposing these fruit to 100 to 150 ppm ethylene in air for around 24 hours stimulates ripening with its associated changes in aroma and softening. However, most melons are now harvested mature enough to not require a postharvest ethylene treatment. The sugar content of harvested melons does not increase upon ripening because at harvest, mature melons do not have extensive reserves of starch which can be hydrolyzed into sugars. Improper handling (e.g., elevated temperatures, injuries) can stimulate respiration with the loss of sugars and taste quality.

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Softening associated with ripening has been extensively studied and mutant lines have been created through traditional plant breeding or generic engineering with diminish rates of softening (Pech et al., 2008). The disruption of ethylene production or sensing has been a major focus of such research. However, the discovery that some components of ripening (e.g., aroma development) are not tightly coupled to ethylene production indicated that ripening could be modified by altering other metabolic pathways.

2.3

Maturity and quality components and indices

Melons are harvested by maturity, not by size; although size is an important component of their marketability. The soluble solids (e.g., sugar) content is the primary factor governing maturity. 2.3.1 Commercial maturity of cantaloupe Maturity is optimal at the firm-ripe stage or ‘3/4 to full-slip’ when a clear abscission (i.e., slip, separation) from the vine occurs with light pressure. Cantaloupes can ripen after harvest (i.e., soften and develop characteristic aroma and flavor) but do not increase in sugar content. For maximum quality, cantaloupes should be harvested at the ‘full-slip’ stage for local markets since the sugar content, flavor and texture improve very rapidly as the fruit approaches this stage of development, but a less mature stage is optimal for shipment to distant markets to avoid excessive losses from over-ripeness and decay. High quality melons should be nearly spherical and uniform in appearance. An abscission zone should have formed producing a full slip with no adhering peduncle (i.e., stem-attachment). Fruit can be harvested at one-half or quarter slip if their soluble solids content is sufficiently high. The surface should lack scars, sunburn or other defects. The fruit should be firm with no evidence of bruising or excessive scuffing. The fruit should be heavy for its size and have a firm internal cavity without loose seeds or accumulated liquid. U.S. grades are Fancy, No. 1, Commercial and No. 2. Distinction among grades is based predominantly on external appearances and measured soluble solids. Federal Grade Standards specify a minimum of 11% soluble solids for U.S. Fancy (‘Very good internal quality’) and 9% soluble solids for U.S. 1 (‘Good internal quality’). A refractometer is usually used to measure the °Brix, which is accepted as the current standard measurement for soluble solids. Sizing is based on count per 18.2 kg (40 lb.) container. There are typically 9, 12, 15 and occasionally 18 or 23 melons per carton. A cardboard divider is folded at different locations to produce compartments for the different sized fruit (see Plate III in the colour section between pages 238 and 239). 2.3.2 Commercial maturity of honeydew There are three commercial maturities for honeydew melons.

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1 Mature, unripe. Ground color white with greenish accents, no characteristic aroma, peel fuzzy/hairy and not waxy. California Grade Standards establish a minimum legal harvest index of 10% soluble solids (10 ° Brix). 2 Mature, ripening. Ground color white with slightly discernible green tint, slightly waxy peel, blossom-end firm and unyielding, no or slight aroma. Preferred commercial maturity class. 3 Ripe. Ground color creamy white with yellow accents, clearly waxy peel, characteristic aroma noticeable, blossom-end yields slightly to press. The fruit should be well-shaped, nearly spherical and uniform in appearance. There should be an absence of scars or surface defects, with no evidence of bruising. The fruit should appear heavy for size, and the surface should be waxy and not fuzzy. The US grades are similar to those for cantaloupe, but more emphasis is given to surface appearance. Sizing is based on count per 13.6 kg (30 lb) container, most typically four or five, and occasionally six melons per carton. The maturity and ripeness of ‘Winter’ melons (e.g., Crenshaw, Persian, Casaba, Juan Canary, and Santa Claus) can be difficult to determine because they do not form an abscission zone and ‘slip’ from the vine when ripe. These melons may require ethylene to enhance ripening, which can be administered in transit from production areas, or at distribution centers.

2.4

Preharvest factors affecting fruit quality

Good cultural practices should be followed with adequate and consistent watering to avoid rapid expansion of the fruit which could cause cracking. Fertilization should allow uniform growth and provide sufficient trace minerals (e.g., calcium) to lessen the development of physiological disorders. However, calcium fertilization may have limited benefit because most soils have adequate calcium and calcium has limited mobility in the plant. Like other field crops, melon yield increased with increasing nitrogen fertilization, but quality was not affected by nitrogen level. Exposure to chilling or excessively high temperatures before harvest may increase the fruits susceptibility to postharvest chilling injury. Intense solar radiation on exposed fruit (either in the field or during transit to a packing facility in uncovered field containers) may raise the skin and underlying flesh temperature sufficiently to cause damage (e.g., sunburn, sunscald) with symptoms of skin discoloration and poor or abnormal ripening. Incomplete pollination can produce misshaped fruit; e.g., a pear-shaped fruit.

2.5

Postharvest handling factors affecting fruit quality

2.5.1 Temperature management Melons are often harvested in the summer at elevated temperatures. The fruit should be rapidly cooled soon after harvest to maintain optimal quality. Precooling

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to 10 °C is typical, but cooling to 4 °C is more desirable. Forced-air is the most common method used to cool field packed fruit. The use of hydrocooling is diminishing as packing shifts from the packing shed to the field. Immersion of hot fruit in cold water during hydrocooling may permit intrusion of water through the stem scar and the absorption of contaminants that have accumulated in the cooling water. 2.5.2 Physical damage Surface abrasion and scuffing, especially in the non-netted inodorus varieties, increases skin discoloration and water loss, which is a major cause of the loss of firmness. The open seed cavity in many mature melons makes them susceptible to a postharvest defect in which the tissues associated with the seeds become separated from the pericarp wall because of violent physical motion (e.g., rolling, dumping, shaking). The early harvest of US Western Shipping melons and their relatively closed cavity minimizes this type of damage during transportation to distant markets (see Plate IV in the colour section). 2.5.3 Water loss The spherical nature of melon fruit minimizes the surface to volume ratio, and their well developed rind and skin combine to limit water loss. However, apart from biochemical changes in cell wall plasticity which produces tissue softening, water loss can cause a loss of firmness. This is especially true in fresh-cut melon products where the removal of natural barriers to diffusion leaves the exposed tissue susceptible to vapor-pressure deficit driven water loss. Waxing, plastic wraps, packaging and maintaining high relative humidity surrounding the commodity have been be used to lessen water loss. 2.5.4 Atmosphere Melons, especially cantaloupes, derive a slight benefit from storage at 2 ° to 7 °C in 3 to 5% oxygen and 10 to 20% carbon dioxide. This fungistatic level of carbon dioxide suppresses decay on the stem and rind, and acts as an ethylene antagonistic to slow ripening with its associated softening and color changes. Controlled and modified atmospheres may also reduce chilling sensitivity. However, 20% carbon dioxide will cause a carbonated flavor in the fruit flesh which can be lost upon transfer to air. Oxygen levels below 1% and carbon dioxide levels above 20% may impair ripening and produce off-flavors and odors. Beneficial atmospheres can be generated by enclosing the fruit in plastic films. Plastic wraps can also reduce water loss and its associated loss of firmness. Melons shipped substantial distances (e.g., cantaloupes shipped from South America to Europe) often use a bag-in-box design where cooled fruit are placed within a plastic bag in a box. The bag is folded over before the box is closed. The

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bag retards gas diffusion so the humidity around the fruit increases, which lowers water loss, and fruit respiration elevates the carbon dioxide level to around 10% which retards microbial growth. Since this beneficial carbon dioxide level is a balance between carbon dioxide diffusion out of the bag and carbon dioxide production by the fruit, it is very important to maintain the temperature (and thereby the rate of respiration) for which the package design was optimized. Melons must be cooled before packaging and the maintenance of the proper temperature is crucial if they are to be kept in plastic during retail marketing. The high rate of respiration during the climacteric of ripening melons can produce sufficient heat to raise their temperature. Package design should allow sufficient air movement around the fruit to remove this vital heat and maintain the desired storage temperature.

2.6

Physiological disorders

2.6.1 Chilling injury Melons are chilling sensitive and are adversely affected by storage at low, non-freezing temperatures. The level of sensitivity varies with maturity, cultivar and previous growing and handling conditions. Cantaloupes are slightly chilling sensitive and can exhibit surface browning and increased decay after extended storage below 2 °C. Honeydew and other melons are more sensitive. In these melons, chilling produces water-soaked areas in the flesh, browning of the surface, increased decay and a failure to ripen normally (see Plate III in the colour section). Since chilling affects ripening, riper fruit (e.g., maturity #3 honeydew) are less susceptible to chilling injury. Honeydew that are mature but unripe should be stored at 10 °C, while ripe fruit can be stored at 5 ° to 7 °C without suffering chilling injury. Experimental treatments involving exposures to low or high temperatures for short intervals, dips in various aqueous solutions, and modified atmospheres have been developed which lessen the development of chilling injury symptoms. However, commercial handling of melons is best served by adhering to proper temperature management to avoid chilling in the first place. 2.6.2 Other physiological disorders Most physiological disorders (e.g., water soaked and flesh browning) are associated with exposure to extreme conditions; elevated temperatures, and ethylene or carbon dioxide concentrations, and low temperatures or oxygen concentrations. Premature softening and water-soaking of fruit flesh have been associated with low calcium levels. Postharvest dips in aqueous calcium solutions increase calcium levels in whole and segmented fruit. However, this method cannot be used with field-packed fruit. Melons develop few disorders after harvest if held under proper storage conditions.

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Pathological disorders

Postharvest losses are predominately caused by physical injury due to bruising and chilling injury and not by diseases. However, melons are susceptible to a number of bacterial and fungal diseases; they include powdery mildew, downy mildew, Alternaria leaf spot, Anthracnose, and Fusarium wilt. Melons are also susceptible to watermelon mosaic, cucumber mosaic, cantaloupe latent virus; diseases which are transmitted by aphids. Squash mosaic virus is seed borne and beetle transmitted. Curly top virus is transmitted by beet leaf hoppers. Melon diseases can be controlled through crop rotation, using resistant cultivars and approved fungicides. Disease vectors can be controlled with insecticides. Postharvest fungicide dips are essential to control postharvest diseases during storage, or long distance transport. A recommended fungicide application is a mixture of 500 ppm benomyl (Benlate) and guazatine (Panoctine). Hot water dips may be used to supplement or augment such fungicidal treatments.

2.8

Insect pests and their control

The pests which affect melons include melon aphid, green peach aphid, cucumber beetle, leafhopper, leaf miner, red spider mites, and melon worm. Soil pests include nematodes, wire worms, and corn seed maggot. Some insects are disease vectors, with bacterial wilt being transmitted by the cucumber beetle.

2.9

Postharvest handling practices

2.9.1 Harvest operations Melons are harvested mature and undergo significant changes in aroma production and firmness, and lesser changes in sugar content after harvest. Mature cantaloupes are harvested at the full slip stage when the fruit easily separates from the stem. Reduced susceptibility to mechanically injury and additional marketing-life can be achieved by harvesting the fruit at a mature, but less ripe stage of development. Less mature fruit do not so easily detach from the stem and these half-slip and quarter-slip fruits can be identified by the portion of stem remaining attached to the harvested fruit. Honeydew types of melons do not form this abscission zone between the fruit and stem. These fruit should be cut, not pulled from the vine to prevent mechanical damage to the stem-end of the fruit. Harvesting is almost entirely done by hand because it is difficult to distinguish the proper stage of melon maturity mechanically and to permit multiple harvests. Harvest aids are commonly employed in field packing operations and to pick up the boxed melons. However, the large machines necessary for field packing can severely damage the vines and only permit one harvest.

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2.9.2 Packinghouse practices Melons are warm-season fruit that are often harvested when day time temperatures are quite hot. Harvesting in the early morning or at night can reduce the heat load. Melons can be harvested into lined, low-volume bins for transport to packing facilities (Fig. 2.2). Bulk melons are usually dry dumped before being sorted and cooled. However, field packing is preferred to minimize handling and subsequent mechanical injury. Field heat is removed at the packing facility by hydro-cooling before grading, sizing and packing of bulk melons, or by forced-air cooling for packaged melons. Sizing and sorting the fruit to produce uniform packs and the application of post-harvest treatments (e.g., applying wax, fungicides) is more easily accomplished in a packing facility. Diligent supervision is needed to maintain consistent quality in field packing operations.

Fig. 2.2 Postharvest harvesting and handling of melon fruit that are packed in the field or in a packing shed.

2.9.3 Control of ripening and senescence Temperature management remains the primary means of controlling the rate of ripening. The rate of respiration, and thereby the rate of most associated metabolic processes increases two- to three-fold for every 10 °C rise in fruit temperature. Rapid ripening increases moisture loss and reduces quality and storage life. To maximize quality retention, harvested fruit should be cooled to their lowest tolerated temperature. Most fruit and vegetables should be stored at the

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lowest non-freezing temperature; usually 0 °C. However, since melons are chilling sensitive they must be stored at a higher temperature which naturally results in a shorter shelf life than non-chilling sensitive fruit. Since ripening is so tightly coupled with ethylene production, genetically modified lines of melons have been produced with greatly diminished rates of ethylene production. These lines have slower rates of ripening and extended shelflife. The natural variability in the amplitude and rapidity of the climacteric has also been used to develop lines with altered rates of ripening by traditional breeding methods. Interestingly, fruit left to ripen on the plant continue to exhibit a climacteric in ethylene production, but the rise in respiration (i.e., carbon dioxide production), which usually accompanies the rise in ethylene production in harvested fruit, is greatly diminished until the fruit is detached or naturally abscises (Shelly and Saltveit, 1993; Hadfield et al., 1995: Bower et al., 2002). It appears that detachment of the fruit during harvest interrupts the flow of something into the fruit which lessens the climacteric rise in respiration. Since the respiratory climacteric consumes sugars which are critical to the taste quality of the fruit, maintaining the effect of this inhibitory factor in harvested fruit could extend their shelf life and taste quality. Ethylene antagonistic such as carbon dioxide and 1-MCP can block ethylene perception and the positive feedback of ethylene on ethylene production and slow the rate of natural or imposed ethylene-induced ripening. However, although these treatments can slow ripening, their use does not diminish the need for prompt cooling and proper temperature management for optimal retention of quality. 2.9.4 Recommended storage and shipping conditions Storage life of cantaloupes is typically 12–15 days within the optimal range of 2.2 °–5.0 °C and 85–90% R.H. Holding the temperature at 2.2 °C can extend the storage life to 21 days, but sensory quality will be reduced as this reduces the production of characteristic flavors and aromas. Honeydews are slightly more chilling sensitive than cantaloupes and should be stored at 7 °C and 85–90% R.H for a storage life of 12–15 days. Short term storage during transit can range from 2.5–5 °C, but these exposures should be minimized since holding melons at these temperatures for seven days may induce chilling injury; especially in the more susceptible cultivars. The damage may not be apparent until the fruit are transfer to typical retail display temperatures where the symptoms of chilling injury will quickly develop. Temperature fluctuations resulting in condensation of water on the fruit’s surface should be avoided as the free water on the surface promotes mold growth. The optimum temperature and handling conditions for honeydew melons are essentially the same as for Crenshaw and Persian melons. Their storage period, however, is shorter and generally does not exceed 14 days. Casaba, Juan Canary,

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and Santa Claus melons retain best quality at the high end of the storage temperature range, 10 °C for up to 21 days.

2.10

Processing

2.10.1 Fresh-cut processing The main impediment to marketing fresh-cut melons is the loss of firmness and development of water-soaked areas. Retention of firmness and texture can be maximized with post-processing dips in aqueous calcium solutions. Various calcium salts have been studied (e.g., calcium chloride, calcium lactate), but each imparts a flavor which consumers may find objectionable. Rapid marketing and proper temperature and humidity management is absolutely crucial to maintain the quality of fresh-cut melons. Fresh-cut melon portions should be washed in a chilled chlorinated water bath immediately after cutting. A further wash in a chilled citric acid and tribasic calcium phosphate solution after sorting and grading would help to maintain quality. Although not the only route of contamination, edible portions of the melon flesh may be contaminated in the cutting or rind removal process. Treatments which would be too severe to apply to the whole fruit destined for prolonged storage and transit (e.g., gaseous ozone and hot water), can be used prior to processing since their main target is to decontaminate the peel which is removed during processing.

2.11

Conclusions

As packing moves away from using a packing shed to predominately field packing, postharvest treatments of whole fruit will be limited to those that can be applied to boxed fruit. Aqueous applications of waxes and fungicides, and quarantine treatments will need to be modified to accommodate the types of containers used in field packaging. The genetic engineering of various metabolic pathways; especially those involved in ethylene production and perception, will continue to be active areas of research and commercial implementation. Instruments are currently being developed that could nondestructively and rapidly measure fruit soluble solids. Once perfected, these instruments could be incorporated into mechanical harvesters, used by pickers to distinguish ripe and unripe fruit more effectively in the field, or used on a pack house grading line to segregate the fruit into maturity and quality classes that would have more uniform postharvest characteristics. Future genetic modifications and technological innovations may augment postharvest melon handling, but they will not eliminate the need for the basic tenants of postharvest biology and technology; maintain proper fruit temperature, relative humidity, and sanitation, and handle the fruit gently and rapidly.

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References

Beaulieu JC, and Gorny JR (2004) ‘Fresh-cut fruits’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/ contents.html Bower J, Holford P, Latché A, and Pech JC (2002) Culture conditions and detachment of the fruit influence the effect of ethylene on the climacteric respiration of melon, Postharvest Biol Tech, 26, 135–146. Hadfield KA, Jocelyn K, Rose C, and Bennett AB (1995) The respiratory climacteric is present in Charentais (Cucumis melo cv. Reticulatus F1 Alpha) melons ripened on or off the plant, J Expt Bot, 46(293), 1923–1925. Lester G and Shellie KC (2004) ‘Honey dew melon’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/contents.html Miccolis V and Saltveit ME (1991), Morphological and physiological changes during fruit growth and maturation of seven melon (Cucumis melo L.) cultivars, J Amer Soc Hort Sci, 116(6), 1025–1029. Miccolis V and Saltveit ME (1995), Influence of storage period and temperature on the postharvest characteristic of six winter-type muskmelon (Cucumis melo L.) cultivars, Postharvest Biol Tech, 5, 211–219. Pech JC, Bouzayena B, and Latchéa A (2008) Climacteric fruit ripening: Ethylenedependent and independent regulation of ripening pathways in melon fruit, Plant Science, 175(1–2), 114–120. Saltveit ME (2003), A summary of CA requirements and recommendations for vegetables, Acta Hortic, 600, 723–727. Saltveit ME (2003), ‘Fresh-cut vegetables’, in Postharvest Physiology and Pathology of Vegetables, eds. J.A. Bartz and JK Brecht, Marcel Dekker, Inc. pp. 691–712. ISBN: 0-8247-0687-0. Saltveit ME (2005), Wound-induced physiological changes in fresh-cut produce, Proc. APEC Symposium, August 1–3, Bangkok, Thailand. Shellie KC and Saltveit ME (1993), The lack of a respiratory rise in muskmelon fruit ripening on the plant challenges the definition of climacteric behavior, J Expt Bot, 44, 1403–1406. Shellie KC and Lester G (2004) ‘Netted melons’, in The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Agriculture Handbook Number 66, eds. Gross KC, Wang CY, and Saltveit ME, http://www.ba.ars.usda.gov/hb66/contents.html Suslow TV, Cantwell M, and Mitchell J (2009) Melon Produce Facts. http://postharvest. ucdavis.edu/Produce/ProduceFacts/Fruit/honeydew.shtml

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(a)

(b)

(c)

(d)

Plate II (Chapter 1) Fruit damaged by thrips (a), translucent aril (b), gamboge with yellow gum outside on fruit surface (c) and with yellow gum inside on the aril (d) (courtesy of Yossapol Palapol).

Plate III (Chapter 2) Honeydew melons showing a packaging pattern in a cardboard container and symptom of chilling injury (darkening of the skin) (courtesy of Marita Cantwell).

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Plate IV (Chapter 2) Cantaloupe melons with a closed (left) and open (right) seed cavity (courtesy Marita Cantwell). Note the thickness of the rind and the structural stability of the seeds and associated tissues.

Plate V

(Chapter 3) Nance inflorescences. Notice the change in color of the petals from yellow to orange as they get older.

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3 Nance (Byrsonima crassifolia (L.) Kunth) O. Duarte, National Agrarian University, La Molina, Peru

Abstract: Nance is a popular minor fruit in Central America commonly found in markets although there are practically no commercial plantations. The fruit is gathered from seedling trees that are sown either by birds or by man as backyard trees. The fruit can be sweet or acid and is used fresh in juices, boiled in syrup, candied or after having gone through an alcoholic fermentation process. Many people dislike it because of the soapy smell produced by its high fat content. The tree bark has high tannin content and is used to cure diarrhea and other ailments. Key words: nance, Byrsonima crassifolia, postharvest, tannin, fat content, alcoholic fermentation.

3.1

Introduction

3.1.1 Origin, botany, morphology and structure Nance, nancite (Central America), peralejo (Cuba), nanche, nanchi, chi, nanchite (Mexico), indano (Perú), changugu, craboo, maricao, peralejo, perdejo, peralejo de sabana (Caribbean), muricí (Brazil), golden spoon or golden cherry (USA), are some of the names of the fruit of Byrsonima crassifolia. This species is native to the dry tropical forests of southern Mexico, the Antilles, Central America and the Amazon basin in South America. It belongs to the Malpighiaceae family and several related species exist, such as Byrsonima coriacea, B. verbascifolia and others (Standley and Steyermark, 1946; Williams, 1981; Barbeau, 1990). It is an evergreen tree that can reach 10 m but normally will grow to 3–4 m in height. The trunk is not very straight and its wood can be used to make small wooden objects. The leaves are simple, entire, opposite, shiny on their upper side and have a short petiole. They can reach 6 to 16 cm length and 3 to 8 cm width. According to Morton (1987) the showy flowers are hermaphroditic with a diameter of about 1.5 cm. The five sepals are green and the five petals turn from yellow to an orange or reddish color as they get older. The flowers come in terminal

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inflorescences and change color gradually according to the age of the flowers so that the different colors can be seen in the inflorescence (see Plate V in the colour section between pages 238 and 239). The flowers are dependant on pollination by insects like Trigona folviventris Guerin., Apis mellifera and Polyubia occidentalis Oliver (Duarte and Vernon, 2002). The ovary is trilocular with one ovule per locule and with three stigmas. The fruit is a globular drupe measuring from 1 to 2 cm in diameter (see Plate VI in the colour section). The external peel is soft and normally turns from green to yellow, and sometimes orange, red when ripe. However the peel of some types remains green when ripe. The pulp is about 0.5 cm thick and white to yellowish-white or cream in color. The fruit can be sweet, acid or sometimes bitter. Fruit weight can vary from 2 to 5 g. The fruit has a single round stone in the center that consists of three embryos with their covers fused together. Therefore sometimes three plants can germinate from a single ‘seed’, but normally only one of the embryos germinates (Donadio et al., 2002). 3.1.2 Worldwide importance and economic value Nance is mainly consumed in its areas of production where most of the crop is sold by roadside vendors. The rest reaches the markets of certain cities in Mexico and Central America. In many of these countries, restaurants, juice vendors and housewives buy the fruit mainly to make juices or desserts. Some fruit is exported from Central America to Canada and the United States as frozen fruit or pulp, to avoid quarantine barriers. Also fruit in syrup or alcohol is exported in small amounts for Central American and Caribbean immigrants living in the United States or Canada. 3.1.3 Culinary uses, nutritional value and health benefits The fruit is normally eaten fresh but can also be processed into juices, pulps (which can be used in fruit yoghurts), jams (which have a buttery taste), alcoholic products or candied products or preserved in syrup (fruit composition is shown in Table 3.1). The fruit has a relatively high fat content and in some places lipids are extracted from it. According to Donadio et al. (2002) the peel can contain 25% fat and the seed around 11%, the pulp acidity is about 2.45% with a Brix of 4.49 °, the pH is around 3 and it has a low content of vitamins that according to Morton (1987) is about 0.010 to 0.014 mg thiamine, 0.015 to 0.039 mg riboflavin, 0.266 to 0.327 niacin and 90 to 129 mg ascorbic acid per 100 g of fresh pulp. Bayuelo-Jimenez (2008) says the distinct fruit aroma that some people dislike is mainly due to ethylbutanoate (sweet and fruity), ethylhexanoate (fruity), butyric acid (rancid cheese), hexanoic acid (pungent cheese) and phenylethyl alcohol (floral scent). The leaves and the trunk bark are rich in tannins, as well as the unripe fruits. The tannins are used for tanning and a decoction of this bark is used to cure diarrhea, to lower fever and as an anti inflammatory.

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Table 3.1 Chemical composition of 100 grams of the edible portion of fresh nance (Byrsonima crassifolia) fruit in the green-mature and mature stages and weight composition of the fruit Chemical composition

Green-mature

Mature

Moisture Total dry matter: – Ashes – Organic matter

83.99 g 16.01 g 0.70 g 15.30 g

83.04 g 16.96 g 0.74 g 15.22 g

Organic matter breakdown: – Crude protein – Ether extract (Fats) – Crude fiber – Nitrogen free extract of which reducing sugars constitute

0.92 g 1.59 g 2.26 g 10.54 g 7.45 g

0.89 g 2.23 g 2.33 g 10.77 g 8.86 g

Weight composition: Seed Pulp and peel

10.22% 89.78%

14.42% 85.58%

Source: Duarte and Vernon, 2002.

3.2

Fruit development and postharvest physiology

3.2.1 Fruit growth, development and maturation According to Duarte and Vernon (2002) this species needs cross pollination for adequate fruit set. These authors found that when using a mosquito net to cover the inflorescences almost no fruit set occurred (0.5–1.0%) whereas the percentage of fruit set in uncovered fruits was 40–46%. The fruit will take from five to six months from anthesis to ripening (Fig. 3.1). The fruit are initially green in color turning lighter as they mature and finally becoming yellow, although some types can be almost red, dark orange or green. The mature fruit will normally drop to the ground from where it is picked at harvest time. The day the fruit drops from the tree it cannot be eaten because it has

Fig. 3.1 Nance (Byrsonima crassifolia) fruit growth curve for weight (continuous line) and diameter (dotted line) at El Zamorano, Honduras (Duarte and Vernon, 2002).

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an astringent taste due to high concentration of tannins. This unpleasant taste will normally disappear next day and by that time the fruit will have a softer texture (this can be checked by pressing it between the fingers). The fruit can also be harvested several days before it drops naturally, as is described in the following section.

3.2.2 Respiration, ethylene production and ripening There is not much written information on this aspect. According to Velásquez de Klimo (2006), the fruit shows a climacteric rise in ethylene production during the third day of storage at 20 °C, while there is no defined pattern in carbon dioxide production. Yet, at the same time this author indicates that other workers claim that nance is not a climacteric fruit. However, there is no doubt that the fruit can be harvested as soon as it starts changing color to paler green or yellow or to the color of the variety. This fruit will ripen normally and can be eaten as soon as the calyx abscises from it and the fruit shows certain softness when pressed between the fingers. Further studies need to be done to define the behavior of this fruit that from the above information seems more likely to be climacteric.

3.3

Maturity and quality components and indices

As already mentioned, the fruit is normally considered mature when it drops naturally. No maturity indices has been developed other than color or fruit drop, which is the more commonly used index. There are no commercial orchards and therefore no standard varieties of nance exist. There is a broad classification of fruit by flavor as acid or sweet, sometimes by the ripe fruit color. The main quality criteria are size and degree of damage, either mechanical, from insects or from diseases. The spotlessly clean fruit are separated sometimes from the fruit that are damaged, contain larvae or show bruises. Insects can also attack the fruit and sometimes larvae are found inside. Aside from this there are no strict quality control measures, since nance is most frequently sold for making juices or pulp or desserts or alcoholic beverages, than for consumption as a raw fruit. Obviously the consumer prefers a spotless fruit but many times there is not much to choose from in the market.

3.4

Preharvest factors affecting quality

Damage by some fungal diseases and attack from insects that lay eggs that evolve into larvae can occur. Sometimes leaf cutting ants (Atta sp.) can be a problem, cutting and taking pieces of the fruit which normally will render the fruit useless.

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Postharvest biology and technology of tropical and subtropical fruits

Postharvest handling factors affecting quality

Mixing fruit of different sizes and maturity stages causes problems, as the softer fruits get squeezed by the less soft fruits and ooze their juices. There is a tendency to pack the fruits incompetently using inadequate packing material and containers that have excessive volumes. In many instances fruit arrives squashed at the market or supermarket due to excessive size of the packing container or its roughness.

3.6

Physiological disorders

No information is available on physiological disorders of nance.

3.7

Pathological disorders

Nance plant and fruit are both very tolerant and there are very few diseases that affect them. Sooty molds, though, that live on the honey dew (secretion) that certain sucking insects leave on the plant, can be problematic.

3.8

Insect pests and their control

According to Bayuelo-Jimenez (2008) there are some insects that attack nance trees, among them Macrospis festina which eats the fruits, and Oncideres dejean and Orthezia insignis which cut the branches.

3.9

Postharvest handling practices

Ideally the fruit should be picked from the tree just before it will drop. This is not practical and therefore it is recommended to harvest the fruits that are turning lighter green or to put a netting or canvas under the canopy so the fruit do not touch the ground when they drop. Fruits picked up from the ground are likely to have become moist and been attacked by insects like ants and others that will damage them. The fruits should be classified by size into at least three categories – small, medium and large. They should also be classified by softness and maturity stage as well as by appearance, separating fruit without blemishes from the others as well as those of different sizes or colors. Fruits of similar size and maturity stages should be packed together. Packing containers should be small, with a capacity of no more than five or six kilograms and with smooth and padded walls and bottoms. Storage temperatures should be around 9 to 13 °C as at these temperatures the fruit quality remains acceptable for 10 to 12 days. It is recommended that the fruit

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should not be left for more than 24 hours at room temperature. Keeping fruits under water is also mentioned as a storage technique (Morton, 1987).

3.10

Processing

The most common method of processing usually involves placing the fruit with some water in a blender at low speed to separate the pulp from the stones. This pulp can then be used to make juices. Another practice is boiling the fruit with sugar to make a jam. The seeds are strained afterwards. Sometimes the fruit is candied by boiling with a larger quantity of sugar so rather than producing syrup a sweet paste is left that surrounds the seed. Fruit with excellent appearance are processed in a light syrup and sold in supermarkets in glass jars. Various alcoholic products can be made with nance fruit. Ripe and blemish free fruits can be put in a jar after washing, some sugar added and the spaces filled with water. The jars are then left in the sun until alcoholic fermentation has taken place. The resulting product is a good tasting liquor that can be stored for years. Alternatively the fruit can be put in a jar and the spaces filled with boiled water before it is left for the internal sugars to ferment. This method takes longer. Another method is to fill the jar with fruit and sugar cane alcohol (aguardiente) instead of water. The jar is left for several months so that the alcohol penetrates the pulp and at the same time takes on the flavors and aromas of the ripe fruit. When freezing the fruit it is best to use the Individually Quick Freeze (IQF) system to avoid the formation of ice crystals in the fruit. If ice crystals form they damage the fruit′s internal structure, so it will look bad once it has thawed. The fruit should be kept at −18 °C for best results after prolonged storage.

3.11

Conclusion

Nance is probably among the five or six most popular fruits in countries like Guatemala, El Salvador, Honduras and Nicaragua and is fairly popular in Mexico, Panama and parts of Brazil. However, there is very little literature available on this crop. It is normally not cultivated in technically conducted plantings and its propagation is sexual resulting in high variability. An export market for the crop already exists, as the fruit is exported to the United States and Canada where it is an ethnic product for a particular population sector. This reinforces the need for more research on this crop in order to raise its level of production, quality and commercial importance. In all probability if selected plant materials are propagated asexually (which can be done very successfully), the plants properly cultivated, and the fruit handled and stored according to the latest technical information, nance could become an interesting species to grow in some areas, especially for the export market.

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Postharvest biology and technology of tropical and subtropical fruits

References

Barbeau G (1990), Frutas tropicales en Nicaragua, Dirección General de Técnicas Agropecuarias. Managua, Nicaragua, Editorial Ciencias Sociales. Bayuelo-Jimenez J (2008), The nance (Byrsonima crassifolia). In: Janick J and Paul R (eds). The Encyclopedia of Fruit and Nuts. Wallingford, UK, CAB International, pp 459–461. Donadio L C, Moro F V and Servidone A A (2002), Frutas Brasileiras. Jaboticabal, Sao Paulo, Brasil, Editora Novos Talentos, p 288. Duarte O and Vernon R (2002), Biología floral y reproductiva del nance (Byrsonima sp). Proc. Interamerican Soc. Trop. Hort. 46: 40–41. Morton J (1987), Fruits for Warm Climates. Greensboro, N.C., USA. Media Incorporated. Standley P C and Steyermark J A (1946), Flora de Guatemala. Fieldiana: Botany 24(5): 478–479. Velásquez de Klimo I (2006), Manejo pos cosecha del nance (Byrsonima crassifolia (L) HBK). Ministerio de Agricultura y Ganadería. San Salvador, El Salvador. IICA Frutales, Programa Nacional de Frutales. Williams L O (1981), The Useful Plants of Central America. Ceiba 24(1–2): 202–203.

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Plate IV (Chapter 2) Cantaloupe melons with a closed (left) and open (right) seed cavity (courtesy Marita Cantwell). Note the thickness of the rind and the structural stability of the seeds and associated tissues.

Plate V

(Chapter 3) Nance inflorescences. Notice the change in color of the petals from yellow to orange as they get older.

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Plate VI

(Chapter 3) Nance ripening fruits: some are starting to turn yellow.

Plate VII

(Chapter 4) Unpicked Noni fruit.

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4 Noni (Morinda citrifolia L.) A. Carrillo-López, Autonomous University of Sinaloa, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico

Abstract: Noni (Morinda citrifolia L.) is the small tropical evergreen tree native to South-East Asia whose whole fruit, juice, seed, leaf, bark and root are used as sources of traditional medicines by Australian aboriginal, Pacific Island and South-East Asian communities. These plant parts have shown antioxidant, antimicrobial, anti-cancer and anti-inflammatory properties. Noni cultivation has spread extensively to regions such as Mexico, Central and South America, and in recent years its economic value has grown significantly worldwide due to assertions of its health benefits. The largest markets for noni products are North America, Europe, Japan, Mexico, Asia and Australia. It is sold mainly as juice, but the fruit is also often marketed in its fresh, unprocessed form in both formal and informal markets. Optimization of agricultural techniques, postharvest practices and processing technologies for noni are required. Postharvest handling information on the fruit is quite scarce. Key words: Morinda citrifolia, noni, postharvest, processing, postharvest handling, anticancer, anti-inflammation.

4.1

Introduction

4.1.1 Origin, botany, morphology and structure The noni (Morinda citrifolia), a small evergreen tree, is native to South East Asia (Indonesia to Australia) and is a member of the Rubiaceae family. Its fruit is known worldwide by many vernacular names including Indian mulberry, hog apple, mengkudu, pain killer, gogu atoni, great morinda, jo ban, mona and kesengel, but the most widely-used commercial name is noni (Wagner et al., 1999). The plant flowers and fruits all year round, producing a small, white, perfect flower (one that has both male and female organs). The fruit develops into an oval shape, reaching 4–10 cm in length and 3–4 cm in diameter (see Plate VII in the colour section between pages 238 and 239). When ripe the fruit has a rancid cheese odor, and therefore is also known as cheese fruit. It contains many seeds,

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which are similar in size and shape to apple seeds, but have a harder seed coat. Whereas, there have been many assertions of the health benefits of noni, no governments have yet approved any claims of its health benefits. However, the European Commission (2010) has recently authorized the placing on the market of puree and concentrate of Morinda citrifolia as a novel food ingredient. Previously, the European Commission did the same for leaves of Morinda citrifolia in 2008 (European Commission, 2008) and pasteurized noni juice in 2003 (European Commission, 2003). 4.1.2 Worldwide importance Morinda citrifolia cultivation has spread extensively to regions beyond its origin area: Mexico, Central and South America (Panama, Venezuela, Surinam). It is a source of traditional medicine in coastal Aboriginal communities in Cape York, the Pacific Islands and South East Asia, and in recent years has experienced significant economic growth worldwide due to assertions of its various health benefits. The largest markets for noni are North America, Europe, Japan, Mexico, Asia and Australia, with the worldwide market for these products estimated at US$400 million (McPherson et al., 2007). Some countries (e.g. Costa Rica and Cambodia), have increased cultivation of noni accordingly. Plate VIII in the colour section shows noni fruit in a popular market in Mexico. 4.1.3 Chemical composition Some of the physicochemical characteristics of noni fruit are as follows: water: 90%; pH: 3.72; dry matter: 9.87; total soluble solids: 8 °Brix; protein content: 2.5%; lipid content: 0.15%; glucose content: 11.97 g L−1; fructose: 8.27 g L−1; potassium: 3900 mg L−1; sodium: 214 mg L−1; magnesium: 14 mg L−1; calcium: 28 mg L−1; vitamin C: 155 mg 100 g−1 (Chunhieng 2003). The main components of the dry matter appear to be soluble solids, dietary fiber and proteins, and the main amino acids are aspartic acid, glutamic acid and isoleucine (Chunhieng et al., 2005). Minerals (mainly potassium, sulphur, calcium and phosphorus) account for 8.4% of the dry matter. Vitamins that have been reported in the noni fruit include ascorbic acid (24–158 mg 100 g−1 dry matter) (Morton, 1992; Shovic and Whistler, 2001), and provitamin A (Dixon et al., 1999). Altogether, more than 150 phytochemical compounds have been identified in the fruit and other parts of the noni plant. The major phytochemicals are phenolic compounds, organic acids and alkaloids (Wang and Su, 2001). Commonly reported phenolic compounds include antraquinones (damnacanthal, morindone and morindin), aucubin, asperuloside, and scopoletin (Wang and Su, 2001). Caproic and caprilic acids are the main organic acids (Dittmar, 1993). The principal alkaloid, at least according to Heinicke (1985) is xeronine, however this author reported no chemical characterization for the ‘alkaloid’ xeronine, nor has this subsequently been found and characterized in noni or other plant tissue by anyone else (McClatchey, 2002).

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Phenolic compounds have been found to be the major group of functional phytochemicals in noni juice. Damnacanthal (in root), scopoletin (plant), morindone (in root), alizarin (in root), aucubin (in plant), nordamnacanthal, rubiadin (in root), rubiadin-1-methyl ether (in root bark) and other anthraquinone glycosides have been identified (Morton, 1992; Dittmar, 1993; Dixon et al., 1999; Wang and Su, 2001). According to Farine et al. (1996), fifty-one compounds were abundant enough to be identified by gas chromatography-mass spectroscopy. The ripe fruit is characterized by a large amount of carboxylic acids, especially octanoic and hexanoic acids, but also alcohols (3-methyl-3-buten-1-ol), esters (methyl octanoate, methyl decanoate), ketones (2-heptanone), and lactones ((E)-6-dodeceno-Y-lactone) can be found (Farine et al., 1996). More recently, Pino et al. (2010) reported that ninety-six compounds were identified in noni fruit, out of which octanoic acid (about 70% of total extract) and hexanoic acid (about 8% of total extract) were found to be the major constituents. During fruit maturation and ripening, the concentrations of octanoic acid, decanoic acid and 2E-nonenal decreased, while concentration of some esters (methyl hexanoate, methyl octanoate, ethyl octanoate and methyl 4E-decenoate) increased (Pino et al., 2010). Two unsaturated esters, 3-methyl-3-buten-1-yl hexanoate and 3-methyl-3-buten-1-yl octanoate, were reported for the first time in noni fruit. Concentrations of these two constituents also significantly decreased during maturation and ripening (Pino et al., 2010). 4.1.4 Culinary uses, nutritional value and health benefits Despite its strong smell and bitter taste, the fruit is eaten either raw or cooked. South East Asians and Australian Aborigines consume the fruit raw with salt or cook it with curry. The seeds are also edible when roasted. The main use of Morinda citrifolia today, though, is in the form of a liquid tonic extracted from the fruit. An industry has developed around this fruit juice which is marketed as ‘Noni’ or ‘Noni juice’. The whole fruit of Morinda citrifolia, its juice, seeds, leaves, bark and root are recognized to possess medicinal properties and the Polynesians have been using the noni plant for food and medicinal purposes for more than 2000 years. The fruit is claimed to prevent and cure several diseases (Chan-Blanco et al., 2006; Hirazumi et al., 1994). Traditional uses of noni include the treatment of diarrhea, intestinal parasites, indigestion and stomach ulcers, diabetes, high blood pressure, headache, kidney and bladder tumors, fevers, inflamed and sore gums, sore throat with cough, toothache, arthritis, sprains and broken bones, cough, tuberculosis, asthma and respiratory afflictions, menstrual cramps, regulation of menstruation and prostate complaints, skin problems such as abscesses, boils, blemishes, wounds and infections (Macpherson et al., 2007). In particular, parts of the plant and its fruit are considered remedies for imbalances of the digestive, intestinal, respiratory and immune systems. The likely mode of action is stimulation of the immune system to fight bacterial, viral, parasitic and fungal infections and to prevent the formation and proliferation of tumors (Dixon et al., 1999).

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In recent years different parts of the noni plant have been the subject of medical research aimed at investigating noni’s effects on health. Some of these studies are discussed below. Anti-microbial effects Atkinson (1956) reported that noni inhibits the growth of certain bacteria, such as Staphylococcus aureus, Pseudomonas aeruginosa, Proteus morgaii, Bacillus subtilis, Escherichia coli, Helicobacter pylori, Salmonella and Shigella. It is claimed that the antimicrobial effect may be due to the presence of phenolic compounds such as acubin, L-asperuloside, alizarin, scopoletin and other anthraquinones. Duncan et al. (1998) also reported that the antioxidant scopoletin has an anti-microbial effect. Another study by Locher et al. (1995) showed that an acetonitrile extract of the dried fruit inhibited the growth of Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Streptococcus pyrogen. Saludes et al. (2002) found that ethanol and hexane extracts of noni have an anti-tubercular effect since they inhibit 89–95% the growth of Mycobacterium tuberculosis. The major components identified in the hexane extract were E-phytol, cycloartenol, stigmasterol, β-sitosterol, campesta-5,7,22-trien-3-b-ol, and the ketosteroids, stigmasta-4-en-3-one and stigmasta-4-22-dien-3-one. Other studies reported a significant antimicrobial effect on different strains of Salmonella, Shigella and E. coli (Bushnell et al., 1950; Dittmar, 1993). The antimicrobial effect in these studies was highly dependent on the stage of ripeness and processing. A greater effect was seen in ripe fruit that had not been dried. Anti-cancer properties Noni juice is a rich source of antioxidants (Wang et al., 2009) which are important in neutralizing ‘free radicals’ or particles that cause DNA damage that can lead to cancer. When mice were inoculated with Lewis lung carcinoma, those ingesting a daily dose of 15 mg of noni juice had an increase of 119% in life span (Hirazumi et al., 1994) and nine out of 22 mice with terminal cancer survived for more than 50 days. In addition, the ingestion of noni extract, combined with conventional chemotherapy in the treatment of mice with cancer, proved to increase their life spans (Hirazumi et al., 1994). Commercial noni juice has been shown to be able to prevent the formation of chemical carcinogen-DNA adducts (Wang and Su, 2001). Rats with artificially-induced cancer in specific organs were fed for one week with 10% noni juice in their drinking water. They showed reduced DNA-adduct formation, depending on sex and organ (Wang and Su, 2001). In addition, the antioxidant damnacanthal, an anthraquinone found in the plant’s root, has been characterized and has shown some important functional properties, mainly anti-carcinogenic attributes (Solomon, 1999). Anti-inflammatory and other effects Noni juice selectively inhibited COX enzyme activity in vitro and had a strong anti-inflammatory effect comparable to that of CELEBREX® and without side effects (Su et al., 2001). Kamiya et al. (2004) have demonstrated the effects of

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noni fruit on preventing arteriosclerosis, a disease related to the oxidation of low density lipoproteins (LDL). Methanol and ethyl acetate extracts from noni inhibited copper induced LDL oxidation by 88 and 96%, respectively, using the thiobarbituric acid reactive substance method. This beneficial effect could be due to the presence of lignans and phenylpropanoid dimers (Kamiya et al., 2004). Two clinical studies also reported relief of arthritis and diabetes due to noni consumption (Elkins, 1998; Solomon, 1999). Lastly, noni juice has a low glycemic index which helps balance blood sugar levels (Macpherson et al., 2007). The antioxidant scopoletin, a coumarin was also found to have analgesic properties as well as a significant ability to control serotonin levels in the body (Levland and Larson, 1979). Safety issue The suggested link between noni juice ingestion and liver toxicity has been refuted on the basis that it is not consistent with histopathology and clinical chemistry results of subchronic oral toxicity tests in animals as well as observed laboratory values of clinical safety studies (West et al., 2006). Furthermore, the opinion of the European Food Safety Authority (EFSA, 2006) through the scientific panel on dietetic products, nutrition and allergies, was that it is unlikely that consumption of noni juice, at the observed levels of intake, induces adverse human liver effects. There is no convincing evidence for a causal relationship between the acute hepatitis observed in the case studies reported by Stadlbauer et al. (2005), Millonig et al. (2005) or Yuce et al. (2006) and the consumption of noni juice. Conversely, liver protective effects of noni juice have been demonstrated by Jensen et al. (2006).

4.2

Fruit growth, development and maturation

In Hawaii, noni fruit are harvested year round, although there are seasonal trends in the amount of flowering and fruit production that may be affected or modified by the weather and by fertilizers and irrigation. Fruit production may diminish somewhat during the winter months in Hawaii (Nelson, 2003). It is possible to find fruits at different stages of maturity on the same plant at the same time (Chan-Blanco, 2006). In Hawaii, the flowers of Morinda citrifolia develop into mature fruits over a span of at least several weeks. However, there are no published scientific data on the precise time required for fruit growth and development from fruit set to maturation and ripening. The fruit is light green when unripe, becoming whitish yellow when ripe (hard white stage). When harvested at ‘hard white’ stage, in few days the fruit turns soft and translucent yellow (Janick and Paull, 2008). A personal experience with this fruit was as follows: the noni fruit was harvested from a small orchard in Culiacán México at the ‘hard white’ ripeness stage and became very soft, with translucent yellow skin and acquired a putrid smell in two days at about 30 °C. Fruit may be picked and used at any stage of development. Fruit with the appropriate level of maturity should be selected depending on its end use.

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Postharvest biology and technology of tropical and subtropical fruits Table 4.1 Skin color and firmness during noni fruit maturation and ripening Maturity stage

Color

Firmness

1 2 3 4 5

Dark green Green-yellow Pale yellow Pale yellow Translucent-grayish

Very hard Very hard Very hard Fairly hard Soft

Source: Chan-Blanco et al. (2006).

Table 4.2

Noni fruit physical characteristics

Fruit weight, g Length of fruit, cm Girth of fruit, cm Specific gravity, g mL−1 Recovery of juice (%) Pulp percentage Seed percentage

147.9 9.8 5.26 1.13 38.95–46.72 44.76–46.72 3.24–4.31

Adapted from Rethinam and Sivaraman, 2007.

The evolution of the color and firmness of fruits maturing and ripening on the tree is shown in Table 4.1. Some physical fruit characteristics of importance to noni fruit processors are shown in Table 4.2.

4.3

Preharvest conditions and postharvest handling factors affecting quality

Scientific publications about the effects of preharvest conditions and postharvest handling of noni fruit quality are scarce. At the preharvest stage, a high incidence of pathological infection such as sooty mold can reduce photosynthesis in the plant, resulting in poor plant growth and reduced fruit size and quality. Pathological disorders are treated in more detail in the following section. Singh et al. (2007) indicated that the shelf life of the fruit postharvest was up to 5–7 days in open conditions at room temperature of 25–30 °C and relative humidity of 70–75%. Mature fruit tend to change color from greenish yellow to creamy yellow from the third day onwards, whereas ripe fruit of yellowish green color, turn to white on the fifth day. Regarding weight, 12–15 g of loss in weight was found in mature fruits and about 16–18 g of loss in weight of ripe fruit. Optimum storage conditions and the effects of changing temperatures on fruit quality remain to be investigated.

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57

Pathological disorders

A very severe pathological problem called ‘black flag’ has been reported from the Hawaiian area (Nelson, 2004), which is caused by phytophtora species. Infection results in extensive blight of leaves, stem and fruit and green fruit of all ages are susceptible to infection. Fruit may be infected through the flowers, epidermis, or pedicel. More often, though, fruit infection occurs through the peduncle, which joins the fruit with the stem, and progresses from the base of the fruit to the fruit apex. The entire fruit and the adjacent stems turn dark brown or black. Rotten fruit may become desiccated (‘mummified’) when dry weather follows a black flag epidemic. The disease may be controlled with foliar applications of phosphorus acid fertilizers (Nelson, 2004). Nelson and Abad (2010) reported a new species of phytophtora causing black flag. They described how this taxon’s morphology does not match any of the valid 95 Phytophthora species described to date and proposed a name for this new species: Phytophtora morindae. Another pathological problem in noni is sooty mold, a black, superficial growth of a nonparasitic fungus that utilizes the sugary exudates produced by softbodied insects such as scales and aphids. Sooty mold can easily be wiped off leaves by hand or can be controlled by a soapy water spray (Nelson, 2001). A big threat to noni cultivation in the Pacific is root-knot disease caused by nematodes (Meloidogyne spp.). Attack by nematodes severely stunts plant growth and allows the root infection by opportunistic pathogens such as the fungus Sclerotium rolfsii (Janick and Paul, 2008). Root-knot is best controlled by avoiding infection in the seedlings in the nursery, using disease-free plantlets and avoiding the introduction of nematode-infected plants to a new field. Moderate irrigation is recommended.

4.5

Insect pests and their control

According to Nelson (2001), pests known to attack noni in Hawaii include aphids (Aphis gossypii), ants, scales (the green scale), mites (eriophyid mites), whiteflies (fringe guava whitefly), and slugs. Noni monocultures favor pest outbreaks; thus, the severity and frequency of pest attacks can be minimized by intercropping with other species of non-host plants. Pest outbreaks can also be prevented by the elimination of weeds that favor pests development and mites can be reduced by pruning affected leaves. According to Janick and Paul (2008) the most severe damage in Hawaii is associated with whiteflies, whereas in Micronesia the most problematic species is the leaf miner. In general, insect damage may be more severe in locations that are dry or have low rainfall.

4.6

Postharvest handling practices

4.6.1 Harvest operations Noni fruit are harvested by hand by picking individual fruit from the branches. After harvesting, the fruit ripens within a week at ambient temperature, and

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therefore because of its short storage life the fruit cannot currently be transported to distant places even within the same country. According to Singh et al. (2007), harvesting fruit with the pedicel helps to maintain quality postharvest and improve market acceptability. In this study, the highest level of spoilage was observed in fruit harvested without the pedicel. 4.6.2 Packinghouse practices Fruit are placed in baskets, bags or bins for transport to the processing facility. Noni fruit do not bruise or damage easily, so usually no special padded containers or other precautions are used to prevent significant fruit damage (Nelson, 2003). However, for commercialization purposes some fruits are wrapped together in small trays (Fig. 4.1). 4.6.3 Recommended storage and shipping conditions If harvested at the ‘hard white’ ripeness stage or earlier, exposure of noni fruit to direct sunlight or to warm temperatures immediately after harvest is not a significant concern. Noni fruit are usually not refrigerated after harvest (Nelson, 2003). However, because of the increased interest in noni products, it will become important to investigate the optimal handling practices so sale of the fresh fruit outside its area of cultivation becomes possible.

Fig. 4.1

Packaged noni fruit.

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Noni (Morinda citrifolia L.)

4.7

59

Processing

Most noni is consumed as juice (Dixon et al., 1999). Fruit for juice production are picked at their ‘hard white’ stage a few days before they turn whitish yellow, become soft and fall from the tree. The ‘hard white’ fruit should be washed before the flesh softens, then the fruit are held at ambient or room temperature for one to several days to ripen and soften before they are processed. The juice seeps out naturally from the pulp into juice-collection containers, but it can be extracted by squeezing the fruit with a press (Janick and Paull, 2008). If ripe fruit are allowed to sit for an extended period, they begin attracting unwanted fruit flies, rats and other insects or pests, so this should not be allowed to happen. According to Nelson (2003), in Hawaii, noni fruit juice and juice products are processed and prepared by a variety of methods. ‘Traditional’ juice is drip-extracted and then fermented/aged for at least two months. The ‘non-traditional’ method of juice extraction involves pressing or squeezing the juice from ripe fruits. Noni juice may be diluted, or bottled in its pure state. Some noni juices are pasteurized, but not all (Nelson, 2003). Noni juice concentrate can be produced by flash evaporation and the pulp of the fruit is also chopped, dehydrated and powdered for use in reconstituted noni juice products in the dietary supplement industry (Nelson, 2003). For powders or fresh-cut products, fruit can be processed before it fully ripens, as unripe fruit is easier to handle with some types of chopping and drying equipment.

4.8

Conclusions

The noni (Morinda citrifolia) plant, and especially its fruit, has been used for centuries in folk medicine. The most important compounds identified in noni fruit are phenolics (such as damnacanthal and scopoletin), organic acids (caproic and caprylic acid), vitamins (ascorbic acid and provitamin A), amino acids (such as aspartic acid), and minerals. In vitro research and some animal experiments have shown that noni has antimicrobial, anti-cancer, antioxidant, anti-inflammatory, analgesic and cardiovascular activity. Consumption of noni juice is currently high, not only in the producing countries, but also in the USA, Japan and Europe, and this market interest suggests a promising future. However, to determine the real potential of this fruit, more studies are needed to identify its nutritional and functional compounds and the technological processes required to preserve them. Furthermore, studies on the postharvest handling of the fresh fruit are also still needed, due to the necessity of transporting the fruit far from the local production areas for processing or sale. Postharvest physiology (respiration rate, ethylene production rate and ethylene sensitivity), optimal ripening and storage temperatures, and other factors that affect fruit quality after harvest should be investigated.

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4.9

Postharvest biology and technology of tropical and subtropical fruits

References

Atkinson N (1956), Antibacterial substances from flowering plants. 3. Antibacterial activity of dried Australian plants by rapid direct plate test. Australian Journal of Experimental Biology 34:17–26. Bushnell OA, Fukuda M and Makinodian T (1950), The antibacterial properties of some plants found in Hawaii. Pacific Science 4:167–183. Chan-Blanco Y, Vaillant F, Perez AM, Reynes M, Brillouet J-M and Brat P (2006), The noni fruit (Morinda citrifolia L.): A review of agricultural research, nutritional and therapeutic properties. Journal of Food Composition and Analysis 19(6–7):645–654. Chunhieng MT (2003), Développement de nouveaux aliments santé tropicale application á la noix du Brésil Bertholettia excelsa et au fruit de Cambodge Morinda citrifolia. PhD thesis, INPL, France. Chunhieng T, Hay L and Montet D (2005), Detailed study of the juice composition of noni (Morinda citrifolia) fruits from Cambodia. Fruits (Paris) 60(1):13–24. Dittmar A (1993), Morinda citrifolia L. – Use in Indigenous Samoan medicine. Journal of Herbs, Spices and Medicinal Plants 1(3):77–92. Dixon AR, McMillen H and Etkin NL (1999), Ferment this: The transformation of Noni, a traditional Polynesian medicine (Morinda citrifolia, Rubiaceae). Economic Botany 53(1):51–68. Duncan SH, Flint HJ and Stewart CS (1998), Inhibitory activity of gut bacteria against Escherichia coli O157 mediated by dietary plant metabolites. FEMS Microbiology Letters 164: 258–283. EFSA (2006). European Food Safety Authority. Opinion on a request from the Commission related to the safety of noni juice (Juice of the fruit of morinda citrifolia). EFSA Journal 376:1–12. Available from: http://www.efsa.europa.eu/en/scdocs/scdoc/376.htm [Accessed 29 July 2010]. Elkins R (1998), Hawaiian Noni (Morinda citrifolia) Prize Herb of Hawaii and the South Pacific. Woodland Publishing, Utah. European Commission (2003), Commision decision of 5 June 2003 authorising the placing in the market of noni juice (juice of the fruit of Morinda citrifolia) as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2003, 001. European Commission (2008), Commision decision of 15 December 2008 authorising the placing in the market of leaves of Morinda citrifolia as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2008. European Commission (2010), Commision decision of 21 April 2010 authorising the placing in the market of puree and concentrate of the fruits of Morinda citrifolia as a novel food ingredient under regulation (EC) No 258/97 of the European Parliament and of the council. In Official Journal of the European Union, 2010. L102/49. Available from: http://ec.europa.eu/food/food/biotechnology/novelfood/index_en.htm [Accessed 29 July 2010]. Farine, JP, Legal L, Moreteau, B, Le Quere, JL (1996), Volatile components of ripe fruits of Morinda citrifolia and their effects on Drosophila. Phytochemistry 41: 433–438. Heinicke RM (1985), The pharmacologically active ingredient of Noni. Pacific Tropical Botanical Garden Bulletin 15:10–14. Hirazumi A, Furusawa E, Chou SC and Hokama Y (1994), Anticancer activity of Morinda citrifolia (noni) on intraperitoneally implanted Lewis lung carcinoma in syngenic mice. Proceedings of the Western Pharmacological Society 37:145–146. Janick J and Paull RE (2008), The Encyclopedia of Fruit & Nuts. CAB International, London UK. pp. 954. ISBN 9780851996387. Jensen CJ, Westendorf J, Wang MY and Wadsworth, DP (2006). Noni juice protect the liver. European Journal of Gastroenterology & Hepatology 18:575–577.

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Kamiya K, Tanaka Y, Endang H, Umar M and Satake T (2004), Chemical constituents of Morinda citrifolia fruits inhibit copper-induced low-density lipoprotein oxidation. Journal of Agricultural and Food Chemistry 52:5843–5848. Levland O and Larson HO (1979), Some chemical constituents of Morinda citrifolia. Planta Medica 36(2):186–187. Locher CP, Burch MT, Mower HF, Berestecky J, Davis H, et al. (1995), Anti-microbial activity and anti-complement activity of extracts obtained from selected Hawaiian medicinal plants. Journal of Ethnopharmacology 49:23–32. McClatchey W (2002), From Polynesian healers to health food stores: changing perspectives of Morinda citrifolia (Rubiaceae). Integrative Cancer Therapies 1(2): 110–120. Macpherson H, Daniells J, Wedding B and Davis C (2007), The potential for a new value adding industry for noni tropical fruit producers. Australian Government Rural Industries Research and Development Corporation. Publication No 07/132. p 46. Millonig G, Stadlman S and Vogel W (2005). Herbal hepatoxicity: acute hepatitis caused by a Noni preparation (Morinda citrifolia). European Journal of Gastroenterol & Hepatology 17:445–447. Morton JF (1992), The ocean-going noni or Indian mulberry (Morinda citrifolia, Rubiaceae) and some of its ‘colorful’ relatives. Economic Botany 46(3):241–256. Nelson SC (2001), Noni cultivation in Hawaii. Fruit and Nuts 4:1–4. Nelson SC (2003), Noni cultivation and production in Hawaii. In: Proceedings of the 2002 Hawaii Noni Conference. University of Hawaii at Nanoa, College of Tropical Agriculture and Human Resources, Hawaii. Nelson SC (2004), Black flag of noni (Morinda citrifolia) caused by a Phytophtora species. Honolulu (HI), University of Hawaii. p. 4 (Plant Disease; PD-19). Nelson SC and Abad ZG (2010), Phytophthora morindae, a new species causing black flag disease on noni (Morinda citrifolia L) in Hawaii. Mycologia 102(1):122–134. Pino JA, Márquez E, Quijano CE and Castro D (2010), Volatile compounds in noni (Morinda citrifolia L.) at two ripening stages. Ciencia e Tecnologia de Alimentos 30(1):183–187. Rethinam P and Sivaraman K (2007), Noni (Morinda citrifolia L.) the miracle fruit – a holistic review. International Journal of Noni Research 2(1–2):4–37. Saludes JP, Garson MJ, Franzblau SG and Aguinaldo AM (2002), Antitubercular constituents from the hexane fraction of Morinda citrifolia L. (Rubiaceae). Phytotherapic Research 16:683–685. Shovic AC and Whistler WA (2001), Food sources of provitamin A and vitamin C in the American Pacific. Tropical Science 41:199–202. Singh DR, Srivastava RC, Subhash Chand and Abhay Kumar (2007), Morinda citrifolia L. – An evergreen plant for diversification in commercial horticulture. International Journal of Noni Research 2(1–2): 45–61. Solomon N (1999), The Noni Phenomenon. Discover the powerful tropical healer that fights cancer, lowers high blood pressure and relieves chronic pain. Direct Source Publishing; ISBN: 1887938877. Stadlbauer V, Fickert P, Lackner C, Schmerlaib J, Krisper P, et al. (2005). Hepatotoxicity of Noni juice: Report of two cases. World Journal of Gastroenterology 11: 4758–4760. Su C, Wang MY, Nowicki D, Jensen J and Anderson G (2001), Selective COX-2 inhibition of Morinda citrifolia (Noni) in vitro. In: Proceedings of the Eicosanoids and other bioactive lipids in cancer, inflammation and related disease. The 7th Annual Conference, 14–17 October 2001, Loews Vanderbilt Plaza, Nashville, Tennessee, USA. Wagner WL, Herbst DH and Sohmer, SH (1999), Manual of Flowering Plants of Hawai’i (Revised Edition); University of Hawai’i Press. Wang MY, Lutfiyya MN, Weidenbacher-Hoper V, Anderson G, Su CX and West B J (2009), Antioxidant activity of noni juice in heavy smokers. Chemistry Central Journal 3(13):1–5.

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Wang MY and Su C (2001), Cancer preventive effect of Morinda citrifolia (Noni). Annals of the NY Academy of Science 952:161–168. West BJ, Jensen CJ, Westendorf J and White LD (2006), A safety review of noni fruit juice. Journal of Food Science 71:R100–R106. Yuce B, Gulberg V, Diebold J and Gerbes AL (2006). Hepatitis induced by noni juice from Morinda citrifolia: a rare cause of hepatotoxicity or the tip of the iceberg? Digestion 73:167–170.

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Plate VI

(Chapter 3) Nance ripening fruits: some are starting to turn yellow.

Plate VII

(Chapter 4) Unpicked Noni fruit.

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Plate VIII

(Chapter 4) Picked Noni fruit on a market stall.

Plate IX (Chapter 9) Bruising and cutting damage produced during mechanical olive harvest in ‘Manzanillo’ table olives destined for California black ripe olive processing.

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5 Olive (Olea europaea L.) C. H. Crisosto and L. Ferguson, University of California, USA and G. Nanos, University of Thessaly, Greece

Abstract: Olives (Olea europaea L.) are extensively cultivated around the world today in proper climates apart from the Mediterranean region. Olives must be properly harvested, handled, processed and stored for successful high quality table olives or oil production. Most of the world table olives are processed as Spanish-style green olives and California-style black-ripe olives, but Greek-style naturally ripe olives, stuffed olives and many other types and forms of olive fruit foodstuffs are marketed around the world. Most olives are used for olive oil extraction, which is produced and consumed, not only in the Mediterranean basin, but also all over the world. Key words: Olea europaea, curing, pickled, canning, olive packed styles, chilling injury.

5.1

Introduction

5.1.1 Origin, botany, morphology and structure A member of the Oleaceae family (Olea europaea L.), is a small tree native to the eastern part of the Mediterranean region. The ancient Egyptians, Greeks, Romans and other Mediterranean nations cultivated olives for their oil and fruit. The olive is a drupe, botanically similar to other stone fruits. It consists of the carpel with the wall of the ovary developing into both fleshy and dry portions; the skin (exocarp), which is free of hairs, and contains stomata; and the pit (endocarp) enclosing the seed. The fleshy mesocarp, from which edible oil is also extracted with physical methods, is the edible portion of the olive after processing. When processed, the exocarp is also eaten. Fruit shape, size and pit size and surface morphology vary greatly among cultivars. 5.1.2 Worldwide importance and economic value Olives are one of the most extensively cultivated and fast expanding fruit crops in the world. The area under olive cultivation tripled from 2 600 000 to 8 500 000

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Postharvest biology and technology of tropical and subtropical fruits Table 5.1

Eleven largest olive producing countries

Rank

Country/region

Production (in tons)

Cultivated area (in hectares)

— 1 2 3 4 5 6 7 8 9 10 11

World Spain Italy Greece Turkey Syria Tunisia Morocco Egypt Algeria Portugal Lebanon

17 317 089 6 160 100 3 149 830 2 300 000 1 800 000 998 988 500 000 470 000 318 339 300 000 280 000 275 000

8 597 064 2 400 000 1 140 685 765 000 594 000 498 981 1 500 000 550 000 49 888 178 000 430 000 250 000

Source: http://www.internationaloliveoil.org

hectares between 1960 and 2004. The ten largest producing countries, according to the Food and Agriculture Organization, are all located in the Mediterranean region and produce 95% of the world’s olives (Table 5.1). Thus, olives are one of the few crops with such major economic importance for the region. In the Mediterranean region including southern Europe, northern Africa and the Middle East, olives and olive oil have been common ingredients of everyday foods for many centuries. Much lower consumption of olive products is found around the world, but due to the positive effects on human health, olive products are highly appreciated today in the markets worldwide. Commercial olive production is today a multimillion dollar business in California, Australia and other southern hemisphere countries. Olive oil is the major commercial product from olives including all kinds of specialty olive oils (from certain cultivars or blends, locations and growing methods), followed by table olives and their products. Only a few raw olives are marketed, usually locally for home curing. 5.1.3 Culinary uses, nutritional value and health benefits Table olives are prepared from sound, clean, and sufficiently mature fruit classified by stage of ripeness and the processing method used. Fresh harvested olive has a bitter component (oleuropein), a low sugar content (2.6–6%) compared with other drupes (12% or more) and a high oil content (12–35%) depending on the time of year, production method, location and cultivar. These characteristics make it a fruit that (almost always) cannot be consumed directly from the tree and it has to undergo a series of processes that differ considerably from region to region, and depending on variety. The bitterness is generally removed by treatment (curing) with one of the following: dilute base of sodium or potassium hydroxide (lye), salt and water (brine), dry salt or repeatedly rinsing the fruit in water at room temperature prior to canning or packing in brine solution.

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Spanish-style green olive is a major processing method around the Mediterranean region and highly consumed. Most olives grown in California and an appreciable amount of fruit around the world are processed into California-style black-ripe for canning. These fruit are mainly used for salads, pizza, and even finger food. Olives can be sold in various sizes, whole, pitted, chopped, sliced, stuffed or as paste. After curing to remove bitterness, the olives are conserved or packed into brine and often some edible acid in small quantities. Lactic or acetic acid in the form of vinegar may be added to acidify the solution and prohibit further fermentation during storage. Various other methods of olive processing are used around the world. Olive oil is extracted with physical methods from olives after washing, crushing, shaking and centrifuging. The olive oil is stored, packed and marketed around the world for use as raw oil or for cooking. One serving of olives has only 2.5 grams of fat, which is only 3% of the total suggested fat intake per day. Olives contain 12–35% olive oil with the table olive cultivars usually containing less oil than the small-fruited cultivars for oil production. The fatty acid content of olive oils varies by cultivar, maturity, cultivation practices and growing area. Generally, based on the Committee of Codex Alimentarius, they are as follows: stearic acid (18:0), 0.5 to 5%; oleic (18:1), 56 to 83%; linoleic (18:2), 3.5 to 20%; linolenic (18:3), 0.1 to 1.5%; palmitic (16:0), 7.5 to 20%; palmitoleic (16:1), 0.3 to 3.5%; arachidic (20:0), <0.8%; and ecosanoic (20:1), <0.4%. Oleic acid is the major fatty acid and its contribution to the total content of an olive oil may change even further than the levels presented above reaching up to 94%, but also as low as less than 55%. In especially hot regions of the world, where olive has been cultivated during the last decades, oleic acid content may drop below 55% and the oil extracted from the olives is not classified as olive oil but as generic plant oil. Anthocyanins are the major pigments in olives. The most prevalent anthocyanins in ripe olive fruit are cyanidin-3-glucoside and cyanidin-3-rutinoside. During olive development, anthocyanins increase rapidly to a maximum, and then decrease as the fruit becomes overripe. The phenols (tyrosol, hydroxytyrosol) and all antioxidants present in the olive fruit and oil are the major component making this oil, together with its fatty acid synthesis and the physical extraction method, the healthiest oil and the processed olives one of the healthiest foods for human diet around the world. They include tocopherols, carotenoids, sterols, terpenes, chlorophyll and the hydrocarbon squalene.

5.2

Fruit development and postharvest physiology

5.2.1 Fruit growth, development and maturation Approximately one month after full bloom (AFB), a period of intense cell division, the exocarp, mesocarp and endocarp are visible. Then, the endocarp cells cease dividing and become stony, division in the mesocarp cells slows and they start to produce oil approximately 60 days AFB. The oil accumulation is very intense between 100 and 180 days AFB. Skin color changes from green to whitish to red and finally to black starting around 160–180 days AFB in parallel with a decrease

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in flesh firmness and flesh coloring. Fruit respiration is high during cell division, moderate during fruit growth and oil synthesis and low during the initial period of ripening, when a climacteric rise seems to occur only on fruits attached to the tree, but an increase in respiration rate was measured even in harvested ripening fruit (Ranalli et al., 1998). In general, black fruit have a higher respiration rate than mature green fruit (Kader et al., 1990). The fruit photosynthesis is linked to chlorophyll content and is high until the fruit is fully colored, while fruit starch and soluble sugar content decrease during maturation. The young fruit have high proportions of polar lipids relative to the neutral lipids that predominate at maturity; these are largely triglycerides of oleic acid, but with important amounts of 16:0, 18:0 and 18:2 fatty acids. Dry matter accumulation is continuous during fruit growth, while seed, stone, pulp and oil had specific periods of rapid growth influenced by changes in the source–sink ratio. In the last period of ripening, the fruit acquire specialized flavor compounds that are transferred to oil during the extraction or contribute to characterize the processed olives. Olive fruit ripening is a combination of physiological and biochemical processes that can be influenced by fruit load, climatic and cultural conditions, even though most of the events are under strict genetic control. The olive fruit is considered ripe when skin and flesh color has turned to black and no further improvements in oil content and quality or fruit taste are expected except of a progressive slow loss of bitterness due to destruction of oleuropein from natural fermentation. 5.2.2 Respiration, ethylene production and ripening Respiration rates of fresh olives range between 5 to 10 mL of carbon dioxide per kg per hour for mature-green olives and 10 to 20 mL of carbon dioxide per kg per hour for black-ripe olives at 5 °C (Table 5.2). Respiration rates increase two- to three-fold for every 10 °C increase in fruit temperature. The accompanying heat production (2200 to 4400 Btu/ton [0.9 metric t] day−1 at 5 °C) must be included in calculating the refrigeration load required to maintain the olive temperature during storage. Effective air circulation throughout the olives within the storage room is critical to preventing respiratory heat accumulation in any area within the stored olives since this heat can accelerate deterioration of the fruit. Table 5.2 Respiration rates of fresh olives at different temperatures Temperature

mg CO2 kg−1 h−1

5 °C 7.5 °C 10 °C 20 °C

10 to 20 16 to 24 24 to 32 40 to 80

Note: To calculate mL kg−1 h−1, divide the mg kg−1 h−1 rate by 2.0 at 0 °C, 1.9 at 10 °C, and 1.8 at 20 °C. To calculate heat production, multiply mg kg−1 h−1 by 220 to get BTU per ton per day or by 61 to get kcal per metric ton per day.

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Fresh olives produce very small quantities of ethylene (less than 0.1 microliters per kg per hour by mature-green olives and 0.3 to 0.5 microliters per kg per hour by ripe black olives kept at 20 °C). These rates decrease as temperatures decrease. Although olives produce very little ethylene, they are moderately sensitive to ethylene. Exposure to ethylene above one part per million hastens the loss of green color and softening of mature-green olives. To keep the ethylene concentration below one part per million, ethylene-free air should be introduced into the storage room, and sources of ethylene, such as ripening fruits and propaneoperated forklifts, must be avoided.

5.3

Maturity and quality components and indices

For the Spanish-style green olives, horticultural maturity occurs about 2.5 months before physiological maturity when the fruit are firm with green skin. When green skin changes to straw or yellow-green and the flesh partially softens, the fruit is unacceptable for Spanish-style green olive processing. The harvest period will change depending on fruit load, cultivar and the balance between fruit size (increasing with later harvest) and flesh firmness (decreasing with later harvest). Green olives for California-style black-ripe processing are harvested when they are uneven, pale green with a minimum of whitish spots (lenticels) through the characteristic ‘straw’, when green is partially lost with a yellowish cast, color. An olive is considered California mature if it exudes a characteristic white juice from the stem end when squeezed. Further delay in harvest will give unacceptably soft fruit for processing. For the Greek-style naturally black olives, horticultural maturity coincides with fruit ripening which is evidenced from the skin color change from whitish to purple or black. The harvest time after skin color development depends on the cultivar and the final product as harvest delays will give soft final processed fruit, which can be acceptable only for certain fruit processing types. Olives for oil extraction can be harvested from green all the way to the over-mature black stage. Oil quality will be substantially different depending on time of harvest besides all other preharvest and postharvest factors. It depends on olive fruit processing but also consists of fatty acid composition, phenol and other antioxidant content (including chlorophyll), taste, free acid content, and some other oil stability characteristics. Oil quality decreases as fruit maturity progresses, but oil quantity increases until the fruit become ripe (black). From that stage on, no more oil accumulation takes place, the oil quality decreases, but, due to water loss, it is mistakenly thought that as the fruit get overripe, they contain more oil. In general, maturity indices that can be used include size, defects, skin color (depending on processing method to be used), flesh firmness, and oil content. The most important quality indices are the combination of skin color and flesh firmness for processed olive quality and skin color (ripeness stage) for olive oil quality. The olive fruit has a bitter component (oleuropein), a low sugar content (2.6–6%), and high oil content (12–35%) depending on the time of year and variety. These

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characteristics make it a fruit that cannot be consumed directly from the tree and it has to undergo a series of processes that differ considerably from region to region, and depending on cultivar. Some olives are, however, an exception to this rule because, as they ripen, they sweeten right on the tree. In most cases, this is due to fermentation from locally available yeasts as in the case of Thrubolea variety in Greece. The chemical components of processed olives are given in the Table 5.3. Table 5.3

Chemical components of processed olives

Nutrient Proximates Water Energy Energy Protein Total lipid (fat) Ash Carbohydrate, by difference Fiber, total dietary Sugars, total Minerals Calcium, Ca Iron, Fe Magnesium, Mg Phosphorus, P Potassium, K Sodium, Na Zinc, Zn Copper, Cu Manganese, Mn Selenium, Se Vitamins Vitamin C, total ascorbic acid Thiamin Riboflavin Niacin Pantothenic acid Vitamin B-6 Folate, total Folic acid Folate, food Folate, DFE Vitamin B-12 Vitamin A, IU Vitamin A, RAE Retinol Vitamin E (α-tocopherol) Tocopherol, β Tocopherol, β Tocopherol, Δ Vitamin K (phylloquinone)

Units

1.00 X 1 jumbo 8.3 g

g kcal kj g g g g g g

7.00 7 28 0.08 0.57 0.18 0.47 0.2 0.00

mg mg mg mg mg mg mg mg mg mcg

8 0.28 0 0 1 75 0.02 0.019 0.002 0.1

mg mg mg mg mg mg mcg mcg mcg mcg_DFE mcg IU mcg_RAE mcg mg mg mg mg mcg

0.1 0.000 0.000 0.002 0.001 0.001 0 0 0 0 0.00 29 1 0 0.14 0.00 0.00 0.00 0.1

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Olive (Olea europaea L.) Lipids Fatty acids, total saturated 4:0 6:0 8:0 10:0 12:0 14:0 16:0 18:0 Fatty acids, total monounsaturated 16:1 undifferentiated 18:1 undifferentiated 20:1 22:1 undifferentiated Fatty acids, total polyunsaturated 18:2 undifferentiated 18:3 undifferentiated 18:4 20:4 undifferentiated 20:5 n-3 22:5 n-3 22:6 n-3 Cholesterol Amino acids Threonine Isoleucine Leucine Lysine Methionine Phenylalanine Tyrosine Valine Arginine Histidine Alanine Aspartic acid Glutamic acid Glycine Proline Serine Other Alcohol, ethyl Caffeine Theobromine Carotene, beta Carotene, alpha Cryptoxanthin, beta Lycopene Lutein + zeaxanthin

g g g g g g g g g g g g g g g g g g g g g g mg

0.075 0.000 0.000 0.000 0.000 0.000 0.000 0.063 0.013 0.421 0.005 0.415 0.002 0.000 0.049 0.045 0.003 0.000 0.000 0.000 0.000 0.000 0

g g g g g g g g g g g g g g g g

0.003 0.003 0.005 0.003 0.001 0.003 0.002 0.004 0.006 0.002 0.004 0.009 0.009 0.005 0.004 0.003

g mg mg mcg mcg mcg mcg mcg

0.0 0 0 17 0 1 0 42

Source: USDA National Nutrient Database for Standard Reference, Release 17 (2004).

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5.4

Postharvest biology and technology of tropical and subtropical fruits

Postharvest handling factors affecting quality

5.4.1 Temperature management Fresh olives picked at the mature-green or fully-ripe (black) stages can be stored between harvest and processing for a few days to a few weeks, depending on storage conditions. Storage can be used to maintain quality and safety of fresh olives and to extend the processing season while maintaining an orderly flow to the processing plant. Storage conditions and duration can greatly influence the quality of the fresh olives at the time of processing and of their processed products, including oil. Quality attributes of fresh olives include size, color, and freedom from defects (such as mechanical damage, shriveling, surface blemishes, scale and other insect injuries, and chilling injury) and decay. Initial sorting of fresh olives to remove those with serious defects or decay, as well as leaves and twigs, is the first step in successful storage. Cooling fresh green olives to 5 °C (41 °F) and black olives to 2 °C using forced-air cooling before storage and maintaining good air circulation within the storage room are strongly recommended to maximize the benefits of refrigerated conditions between harvest and processing. In general, olives should be stored at 5 to 7.5 °C with 90 to 95% RH; temperatures <5 °C accelerate chilling injury. Black-ripe Manzanillo and Ascolano olives can be stored at 5 °C for up to four weeks, whereas Mission and Sevillano olives can be stored for up to eight weeks at 5 °C, while maintaining good fruit and oil quality. In Greece, Konservolea green olives can store successfully at 5 °C for up to five weeks and Chondrolia Chalkidikis for only two weeks before Spanish-style processing. Black olives can be stored at 2 to 5 °C, because they are less susceptible to chilling injury than green olives. Differences in storage potential between different cultivars are related to a cultivar’s rates of softening, color development and decay, chilling injury incidence and method to be processed. Harvested green olives begin to lose moisture immediately. When harvested in hot, sunny weather, fruit should be set in the shade while waiting to be hauled away. Olives exposed to sun sunburn easily, and are graded as culls. Rough handling causes bruises (very obvious in a few hours on green olives destined for green processed product) and a reduction in grade. Ideally olives should be graded and storage or processing begun within less than 24 hours of picking.

5.4.2 Atmosphere Exposure to carbon dioxide levels above 5% aggravates chilling damage (internal browning) and decay incidence and severity, if olives are kept below 7 °C. A 2% oxygen atmosphere enhances the maintenance of green color and flesh firmness of olives kept at 5 °C or higher temperatures. Exposure to oxygen concentrations below 2% can cause off-flavors in both green and black olives. Under an optimal controlled atmosphere of 2 to 3% oxygen and 0 to 1% carbon dioxide, fresh green olives can be stored for up to 12 weeks at 5 °C or nine weeks at 7 °C, while fresh black olives maintain good quality for both table fruit and oil production for up to

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four weeks at 2 °C to 5 °C or at 2% O2 at 5 °C. The incidence of decay is the main factor in determining storage potential.

5.5

Physiological disorders

5.5.1 Chilling injury Olives are sensitive to temperatures <5 °C. The order of susceptibility to chilling injury, from most to least susceptible is: ‘Sevillano,’ ‘Ascolano,’ ‘Manzanillo,’ and ‘Mission’ for the California grown cultivars. Symptoms include a slight, gray to brown discoloration which develops in the flesh adjacent to the pit. Over time, the discoloration becomes more intense and progresses through the flesh up to the skin, at which time the olive has the appearance of having been boiled. Later on, skin will become brown to black. Chilling injury becomes visible on olives stored for >2 weeks at 0 °C, 5 weeks at 2 °C, or 6 weeks at 3 °C. Chilling injury seems to positively relate to total phenol content of the fruit (G.D. Nanos, unpublished data). Therefore, the optimal storage temperature range is 5 to 7 °C as the lower temperatures cause chilling injury of green olives and higher temperatures accelerate ripening as indicated by changes in skin color and flesh softening. A relative humidity of 90 to 95% is recommended to minimize water loss from fresh olives. 5.5.2 Nailhead This disorder is characterized by surface pitting and spotting. It results from the death and collapse of epidermal cells, which create air pockets underneath the fruit skin. Symptoms are observed on fresh olives kept at 10 °C for six weeks or longer or 7.5 °C for 12 weeks or longer. Delay in placing the olives in brine after harvest may cause nailhead. These depressions persist in the pickled product and are thought to be caused by bacterial action, as colonies of bacteria are found in them. Nailhead is avoided by pickling olives promptly after harvest or storing them promptly in brine. 5.5.3 Carbon dioxide injury Internal browning and increased decay incidence and severity result from exposure to more than 5% CO2 for longer than four weeks. CO2 injury is evidenced by internal browning and increased decay incidence and severity.

5.6

Pathological disorders

Fungal pathogens can develop on olive fruits before harvest and during postharvest storage. Preharvest fruit rots include Glomerella cingulata, Botryosphaeria dothidea and Pseudocercospora cladosporioides. There is no literature describing microorganisms attacking stored fresh olives, but green olives without defects do not rot (most probably they contain an antimicrobial

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agent – phenols, oleuropein) and black olives rot severely with extended cold storage. These postharvest diseases occur if olives have been chilled at temperatures below 5 °C, mechanically damaged, not cooled promptly after harvest to 5 to 7.5 °C, or exposed to undesirable atmospheres (>5% CO2 and/or <2% O2). Occasionally storage containers of processed olives develop an off-odor and off-flavor, termed Zapatera spoilage. This spoilage is characterized by a penetrating, unpleasant odor in fermenting olives. In the early stages, the odor is usually described as cheesy or sagey, but as deterioration progresses it becomes a foul, fecal stench. Under California conditions, Zapatera spoilage, unlike butyric fermentation, occurs when lactic acid fermentation is allowed to cease before the brine pH has dropped below 4.5. A continuous loss of acidity (or rise in pH) causes spoilage to progress only at pH values above 4.2. Hence, maintaining pH values below 4.2 is advisable. Whereas normal brines contain acetic and lactic acids, suspect and spoiled samples contain additional acids. Propionic acid occurs most frequently, followed by butyric acid; succinic, formic, valeric, caproic, and caprylic acids have also been found. These latter volatile acids, together with butyric acid, are partly responsible for the odor of Zapatera spoilage. The lactic and acetic acids furnish energy for the bacteria – two species of the genus Propionibacterium and several species of Clostridium – that appear to cause Zapatera spoilage. If the start of lactic fermentation in olives is delayed unduly the continued high pH permits various butyric acid bacteria to grow, producing butyric odor and flavor and making the olives inedible. Either inoculation with lactic cultures or initial acidification prevents butyric spoilage. Yeasts and bacteria of the Enterobacter group may cause Fisheye spoilage to processed olives. Acidification of the brine with lactic acid and using a higher initial salt content (44 ° salometer or higher) in the brine discourage this type of spoilage.

5.7

Insect pests and their control

5.7.1 Quarantine issues Olive fruit fly (Bactrocera oleae) is present around the Mediterranean region and South Africa, but absent in South America, China and Australia. In 1999, olive fruit fly was found in California and is now present in most California olivegrowing areas. There are limited imports of fresh olives from Argentina and Mexico to California and minimal exports to Canada, which cause no threat for olive fruit fly quarantine matters. Similar problems may exist with scale insects, but there is no information available. All other olive products are processed and very often pasteurized or sterilized, thus are free of insect pests.

5.8

Harvest operations

Table olive harvest customarily begins in mid-September, peaks in mid-October, and finishes in mid-November for green (earlier) and California-style black-ripe (later). For black olives, the harvest period starts with the change in skin color to

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purple–black usually mid-November. The primary reason for delaying table olive harvest early in the season is to accrue value through weight and size. The primary reason for accelerating harvest late in the season is to decrease losses due to over-ripeness, drying wind, and cold damage. The two components of olive crop value are the weight and size of the crop as the total percentage in the standard canning categories of medium, large, and extra large, are closely related to the crop’s net value and olives continue to grow until skin color change. Harvesting table olives costs 50 to 70% of the total production costs and 30 to 50% of the gross return from the crop. Harvested fruit begin to lose moisture, therefore weight and value, immediately, so protection from high temperatures and proper cooling is required. Rough handling causes bruises and grade reduction especially in green olives. Most olives destined for table olive processing are hand harvested when physiologically unripe, thus the abscission zone is unformed, the fruit is more difficult to detach and picking may result in more obvious damage to the fruit and the tree. Olives for oil extraction can be harvested from the straw-color stage through the black-ripe stage, are generally physiologically mature and fruit detachment forces are much lower. However, the fruit is softer and therefore more susceptible to damage during and after harvest. Traditionally, few table or oil olive growers have harvested their fruit mechanically. However, the new oil olive industries developing in the Mediterranean, Argentina, Australia and California are all based on high density hedgerow orchards that can be harvested mechanically. The table olive industry is attempting to emulate the oil olive industry. Therefore, mechanical harvesting is likely to increase in the future for California-style black-ripe and naturally black processing as substantial research on the subject has been going on for decades in California. 5.8.1 Hand harvesting Hand harvesting is the most expensive of the harvest options due to labor costs. In the first few years after planting, olives are hand harvested without any ladders or other equipment. The fruit are removed by sliding the cupped, nude or gloved hand down the shoot in a milking action. The shoot is placed so that fruit fall into the picking bag. When the bag is full, the fruit are dumped into standard orchard bins that hold 454 kg. This process can result in considerable fruit and tree damage. In the Mediterranean small-size orchards, green fruit is detached by the above described ‘milking’ technique or by pulling each fruit and placing it in plastic or metal buckets. The fruit is then carefully transferred to 16-kilo bins. Fruit damage occurs from using a rough technique, dropping fruit from a great distance, and including debris with the fruit. Tree damage results from leaves being torn off with the fruit. At each leaf scar, olive knot bacteria can enter. 5.8.2 Mechanical harvesting There is great interest in mechanical harvesting among olive growers in the world. The major reason for developing mechanical olive harvesting is the high cost

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of hand harvest. In California’s San Joaquin Valley the 2009 average hand harvest cost per ton was approximately 50% of the gross return per ton. Other major olive producing countries report similar percentages. Most table olives are harvested when physiologically immature, therefore the abscission zone is unformed, and the fruit has a higher FRF force (around 1 kgF) than oil olives harvested at physiological maturity (<0.1 kgF). Mechanical harvesting can produce the unacceptable fruit damage seen in Plate IX in the colour section between pages 238 and 239. This immaturity, combined with the traditionally large trees, 4–6 m tall and 3–6 m wide, the pendulous, thick growth habit of most irrigated table olive orchards, and low tolerance for fruit damage, makes mechanical harvesting difficult. Oil olives are harvested physiologically mature. Therefore the FRF is generally less that 0.25 kgF. Mechanical harvesting of oil olives has developed much more rapidly because new olive oil cultivars have been bred for slow growth, planted in high to super high densities (486–1800 trees per hectare) and trellised or trained in a hedgerow easily harvested by over the row adapted grape, coffee and blueberry harvesters. The olive oil industry simultaneously pursued the long term goal of tree genetics, the mid term goal of new orchard conformations with hedgerow tree training and pruning, and the short term goal of adapting existing mechanical harvesters from other crops. As a result, the world’s newest olive oil orchards are exclusively and successfully mechanically harvested with harvesters adapted from other crops. As an example, in Australia nearly all olive plantations are mechanically harvested for oil extraction. If the table olive industry is to ultimately succeed, it must also pursue tree breeding, new orchard conformations with hedgerow training and pruning, and mechanical harvesting technology. However, currently there are no table olive tree breeding programs with mechanical harvesting as an objective. Therefore, the world’s table olive industries must pursue the short term goals of developing a picking technology and tree pruning method for the current table olive orchards. For the midterm the goal is developing a picking technology and new orchard conformations, with new training and pruning methods. Bruising and cutting damage was produced by early versions of the canopy contact head mechanical olive harvester in ‘Manzanillo’ table olives destined for California black ripe olive processing (see Plate IX in the colour section). Trunk shaking did not produce this damage. The two viable picking technologies currently being evaluated for table olives are canopy contact harvesting heads (Fig. 5.1), and trunk shakers (see Plate X in the colour section). The canopy contact harvester can be successfully used in existing orchards that have been pruned to a hedgerow. It can also be used for newer high density orchards trained to a hedgerow. The trunk shaking technology can be used in new high density orchards with straight trunks, but is ineffective in older conventionally trained orchards. Interestingly, both have approximately the same final harvest efficiency, from 58 to 64%. However, the mechanism of fruit removal is different, the two machines harvest different parts of the canopy more efficiently, and the potential for tree damage is different. However, both a sensory panel trained to evaluate California black-ripe processed olives for specific qualities, and a consumer panel drawn from the

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75

Canopy contact head harvester in hedgerow olive orchard.

public could not distinguish mechanically harvested from hand harvested olives. Together with the receiving station quality evaluation of the fresh olives, the evaluation by the trained sensory panel, and the evaluation by the consumer panel strongly supported the conclusion that mechanical harvesting does not decrease processed California black-ripe table olive quality. The same would be expected for naturally black processed olives.

5.9

Packinghouse handling practices

During harvest, if the table olive processing plants do not have enough vats to process all the olives available, the fruit must be stored until processing. Fresh fruit storage is virtually unknown before table olive processing and has been described in this chapter previously. Storage of fresh green olives destined for Castel-Vetrano processing is always necessary. The fruit for Spanish-style green olives can be stored as fresh before lye processing and will be stored in brine after lye processing. The fruit for California-style black-ripe olives may be stored for months before lye processing. Today this storage is done in a relatively dilute, acidulate solution that includes an antimicrobial agent rather than in the traditional salt brine. 5.9.1 Holding in salt-free solution Because it is difficult to dispose of waste brines without contaminating the soil or water, an alternative method for storage of olives destined for California-style

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black-ripe olives uses an acidulate solution containing 0.67% lactic acid, 1.0% acetic acid, 0.3% sodium benzoate, and 0.3% potassium sorbate. Sorted, size-graded olives are placed in open-top tanks of 2.5 ton (2.3 metric t) capacity, the olives are completely covered with the solution, and the tank is completely sealed with plastic sheets and wax. No fermentation occurs in this system, unlike in brine storage. The flavor of olives kept in salt-free storage is as good as or better than that of the same cultivars processed from salt storage. Shrivel, always a problem with some cultivars stored in salt brine, is virtually eliminated. More than 90% of California olives are now stored by the salt-free method. 5.9.2 Holding in brine The traditional method of storage in sodium chloride brine uses paraffin- or plastic-coated concrete, plastic or wooden tanks of large capacity [10–20 ton (9–18 metric t)]. The initial brine contains 5.0 to 7.5% salt, or about 20° to 30° salometer (a saturated solution of sodium chloride, 26.5% salt, reads 100° salometer). At intervals of one to several days, salt or saturated brine is added so that the brine is gradually strengthened to 30° to 36° salometer (7.5 to 9% salt) and the brine is kept at this concentration for the first three months of storage. Added salt or brine must be mixed thoroughly into the tank by means of a circulating pump. As the weather becomes warmer, the brine should be strengthened to 40° salometer. Ascolano and Sevillano olives require an initial brine of 15° salometer to avoid shriveling, and the final salometer reading should be maintained at 30° to 32°. Mild lactic acid fermentation takes place that helps preserve the fruit until processing. The lactic acid content in the brine may reach 0.4 to 0.45% in four to six weeks. It is important that olives be kept under the brine. The cover must have openings that allow circulation by pump when salt or saturated brine is added. If the salt concentration is too low or the acidity insufficient, bacterial softening in the olives is apt to occur due to the growth of bacteria of the Escherichia coli and Enterobacter aerogenes group. These bacteria cause gas blisters in the olives and are responsible for what is termed Fisheye spoilage. At the first sign of spoilage, the brine should be fortified to an 8% concentration and acidified with 0.5% lactic or 0.25% acetic acid. Delay in placing the olives in brine after harvest may cause nailhead, a condition in which small depressions form beneath the skin. These depressions persist in the pickled product and are thought to be caused by bacterial action, as colonies of bacteria are found in them. Nailhead is avoided by pickling olives promptly after harvest or storing them promptly in brine. The pink yeasts associated with softening of olives – Rhodotorula glutinis var. ghainis, R. minuta var. minuta, and R. rubra – produce polygalacturonases that cause a slow softening of olive tissue. Commercial control of these yeasts is not difficult when anaerobic conditions are provided. Otherwise, processors must remove the yeast film from the brine surface manually, by skimming or by beating.

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5.9.3 California-style black-ripe olives California-style black-ripe olives can be made from either fresh or stored olives. Generally, the olives are size graded before being loaded into tanks for lye treatment and storage. Loading Processing tanks of 10–20 ton (9–18 metric t) capacity are supplied with four overhead pipelines containing water, dilute lye, dilute brine, and compressed air. Air for aeration and stirring is distributed by perforated pipes at the bottom part of the tank. The tanks are equipped with outlets for discharging spent lye, brine, and washwater. Lye treatment In the pickling process, olives are subjected to two to six applications of 0.5 to 1.5% lye (sodium hydroxide) solution at temperatures of 10–21 °C, depending on the cultivar. Also, when fruit has been stored longer and ambient storage temperatures have been high, lower temperatures and weaker lye concentrations are required in processing. The greater the number of lye applications and the shorter the duration of each one, the better the color will be. Lye treatments help natural phenolic compounds in olives to oxidize and polymerize, forming a black pigment. Proper lye treatment and exposure of olives to air, or aerating olives in water between lye treatments, develops the black color. In most processing plants, the first lye treatment is allowed to penetrate about one-fourth of the distance into the flesh, determined by using a drop of phenolphthalein in 95% alcohol as an indicator on the cut surfaces of olives or by noting discoloration of skin and flesh. Each subsequent lye application penetrates another one-fourth of the distance to the pit. In some plants, the first three or four lye treatments last only long enough for the lye to barely penetrate the skins of all olives. Color formation is most rapid at a pH of 8.0 to 9.5. Color retention is better in olives pickled in solutions made with hard water probably because calcium salts aid color fixation. Calcium chloride greatly improves color retention when added in low concentration (0.l to 0.5%) to storage solutions before pickling, to lye solutions, or to the water bath between lye treatments. Olives harvested at a green-straw color have the best firm texture after canning. Lye removal Lye is removed by changing the water in the pickling tanks at least twice daily and stirring it frequently by means of compressed air or paddles. If the washwater is stirred continuously, it is possible to remove the lye in three to four days. In several plants, the washwater is replaced with 10° to 12° salometer brine after leaching in water for two to three days. Curing in dilute brine When all the lye is removed by washing, olives are stored in dilute brine for about two days, first in 3°, then in 6°, and finally in 10° salometer brine (2.5% salt).

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Longer storage is undesirable because bacterial growth, texture breakdown, and other microbial troubles may arise. It is at this time that ferrous gluconate at a concentration of 0.1% (P/V) is added to fix the color. Aeration must be avoided during this time. Usually, only 24 hours is required to fix the color. Canning The pH value of olives at the time of canning greatly affects color retention during canning and subsequent storage; a pH of 7.0 to 7.5 appears to be most favorable. Well-pickled olives are packed by weight into cans with a protective C-enamel, which prevents bleaching of the olive color after canning. The most commonly used can sizes are No. 300 (300 × 407 mm), Buffer (211 × 304 mm), Picnic (211 × 400 mm), No. 1 Tall, and No. 10. For chopped or sliced olives, 113 g (4 ounce) cans are used. After filling, a brine of 8° to 10° salometer (2 to 2.5% salt) is added. The cans are exhausted at 93–96 °C for five minutes to reach 77 °C or higher; then they may be rebrined and sealed at 77 °C in a double seamer. An alternative practice is to add hot brine at 96 °C to the cans, followed by sealing at 77 °C in the double seamer. If the olives are cold, it is advantageous to seal with steam injection at 0.35 kg/cm2. Another variation of this procedure is to add a salt tablet and hot water at 96 °C to each can, followed by double seaming with steam injection. Larger metal and glass containers are heat processed at 116 °C for 60 and 70 minutes, respectively. Spoilage Spoilage in California-style black ripe olives during processing is characterized by the softening and ultimate sloughing of skin and tissue from the olive. Spoilage can be controlled by reducing the washing period from the customary four to a maximum of three days. Microorganisms associated with spoilage include some gram-negative pectinolytic bacteria (Entcrobacter aerogenes, Escherichia intemedia, Paracolobactruin aerogenoides, Aeromonas liquefaciens, and Achromobacter). 5.9.4 Spanish-style pickled green olives Pickling of green olives is the most important olive processing method around the world. Olives for pickling are allowed to reach full size but are picked before they have begun to lose green color and soften. Fruit are graded for size and placed promptly in shallow paraffin- or plastic-coated concrete or plastic pickling vats. Lye treatment Dilute lye solution (1.25 to 1.75%) is applied at 12–21 °C. The alkali is allowed to penetrate three-fourths of the way to the pit in eight to 12 hours. Removing the lye solution before it penetrates to the pits leaves a small amount of untreated bitter flesh, which contributes to the flavor of the pickled olives. The phenolphthalein indicator solution is applied to the cut surface of an olive to show the depth of lye penetration into the flesh.

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After the lye treatment, olives are washed with cold water for 36–48 hours; the water is changed at least three times. After washing, the treated flesh of the olive should respond only faintly to the phenolphthalein color test. Fermentation Washed, lye-treated olives are transferred to barrels or much larger [10–20 ton (9–18 metric t)] storage tanks made of various materials. After filling, brine of 7% salt (approximately 28° salometer) is added. Addition of 0.3% lactic acid is also common (or small amounts of glucose or sucrose or even a small quantity of actively fermenting current season brine from other olive-processing containers) and after 15 days fermentation is complete. The pH should be 3.8 or less when fermentation starts. About 15 days later, the storage tank is sealed and processed olives are stored until packing and selling. Under favorable conditions, lactic acid bacteria, some yeasts, and some gasforming bacteria of the Enterobacter aerogenes group grow fairly well. Eventually, the lactic acid bacteria predominate. Packing Pickled olives are de-stemmed and size graded, if this was not done earlier, then sorted on a conveyor belt to remove defective, blemished, and off-color olives. Pickled olives should be free of fermentable sugar and have a total acidity above 0.75% (0.75 g lactic acid per 100 g). Other desirable qualities include a uniform, yellow-green color, a crisp texture, and a pleasant flavor and aroma. Sorted olives are packed carefully, often in glass jars in a definite pattern. Packed jars are then filled automatically with water or brine, then emptied to rinse off any adhering sediment. The jars are then filled with brine of 28° salometer. Some packers may acidify the brine with 0.2 to 0.5% lactic acid, if the olives are below the optimal acidity and jars are then sealed in a capping machine. Although it is not customary, it is advantageous to pasteurize bottled olives at 60 °C or to use hot brine at 79–82 °C. This will prevent sedimentation from bacterial growth. 5.9.5 Olives turning color Olives turning color are rose, wine rose, or light brown in color. They are harvested before complete ripeness is attained and may or may not have been subjected to lye treatment. Treated olives turning color are obtained from fruit treated with lye solution, preserved in brine, and heat sterilized as described above. Natural olives turning color are preserved in brine and are ready for consumption. 5.9.6 Stuffed olives To prepare stuffed olives, pickled and fermented green olives are pitted, either by hand or with high-speed automatic pitters. The pitted olives are stuffed with strips

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of red pimento previously preserved in heavy brine. Small onions, almond meats and other foodstuff are also used. The stuffed olives are barrel fermented for several weeks in 30° salometer brine before packing. Occasionally, stuffed, Spanish-style green olives in bottles show gas formation and spoilage. To prevent this, the pimento must be properly treated in brine to remove the sugars before stuffing. Stuffed olives are packed in the same manner as Spanish-style pickled green olives, described in the previous section. 5.9.7 Greek-style naturally ripe olives Greek-style olives are made from olives picked when they are purple or black. The fruit is put into wooden, plastic or concrete tanks coated with paraffin or plastic paint of a 1–20 ton (0.9–18 metric t) capacity. These are covered with brine of about 20° salometer (5% salt) initially until March and then brine is increased to 10% salt. Fermentation occurs through the action of lactic acid bacteria and yeasts. When fermentation is completed, the olives are graded for size and color and packed in fresh brine in tin, glass or paraffin-coated plastic containers of various sizes. They may also be packed in vinegar brine to be used as an appetizer. In an alternative method, olives are picked when over-ripe, placed in baskets, and washed with water. After 2 to 3 days, the olives are removed and placed in fresh baskets in alternate layers with solid salt. By this means, the natural wrinkles become more pronounced, and the partially dried product keeps well due to the high salt concentration. The fermentation of Greek naturally ripe olives in brine is thought to be due to the activity of a mixed flora composed of coliform, yeast, and possibly Lactobacillus species. The total acidity of the brine is usually less than 0.5%. Sometimes a layer of molds, yeasts, and bacteria forms over the surface of the brine, causing removal of sugar and acids and thereby increasing the pH of the brine. This spoilage may also result from the growth of clostridia, propionic acid bacteria, and possibly sulfate-reducing organisms. Softening is another type of undesirable change. As no lye treatment is used in the preparation of this product, bitterness and other fruit components are only partially and slowly leached into the brine. The degree of blackening depends on, and is favored by, high pH values. Under certain conditions, naturally ripe black olives undergo complete lactic fermentation, developing a total acidity as high as 0.8 to 1.0%. The product can be kept in brines of moderate salt content.

5.10

Grades and standards for processed olives

Food standards are the body of rules directly governing foodstuffs, whether they are issued by official, semiofficial, or factory authority. The U.S. Department of Agriculture (USDA) grade standards for processed olives are voluntary, and

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therefore not required by federal law for olive processors and distributors. The European Union in collaboration with IOOC has developed obligatory grades and standards to be followed, which are briefly summarized below.

5.10.1 Canned table olives Table olives are prepared from sound, clean, and sufficiently matured fruit classified according to trade type (in which both the stage of ripeness and the processes undergone are taken into account). Trade types Processed olives fall into five main trade types: 1 Green olives in brine: treated green olives (bitterness eliminated by treatment with lye) and untreated green olives. 2 Olives turning color in brine: treated olives turning color and untreated olives turning color. 3 Black olives in brine: lye-treated black olives, brine-treated black olives, and naturally shriveled black olives. 4 Black olives in dry salt: black olives in dry salt, and pierced black olives in dry salt. 5 Other trade types: bruised olives, treated split olives, untreated split olives, treated olives darkened by oxidation, and specialties. Styles Whole olives may be offered in one of the following styles: 1 Whole: olives of natural shape from which the pit has not been removed, with or without the stem attached. 2 Whole stoned (pitted): olives of natural shape. 3 Whole stuffed: whole stoned olives stuffed with suitable products, such as pimento, onion, almond, celery, or anchovy. 4 Halved: whole stoned or stuffed olives that have been split into two approximately equal parts along or perpendicularly to the fruit’s major axis. 5 Quartered: stoned olives split into four approximately equal parts. 6 Sliced: stoned or stuffed olives sliced into parallel segments of fairly uniform thickness. 7 Chopped or minced or as paste: small pieces of random shapes and sizes with or without other additions. 8 Broken: olives that have broken while being stoned or stuffed. Sizes Table olives may or may not be size graded. Whole olives should be size graded according to the number of fruit in one kilogram or hectogram. When the unit

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is a kilogram, the size range is expressed in steps of ten olives up to size 111/120, 20 from this up to size 181/200, and 30 up to size 351/380; above 400 per kilogram, the steps are 50 olives. When the weight unit is the hectogram (not shown here), the range is expressed in steps of one olive up to size 15/16; two olives from this up to size 20/22, and three olives up to size 37/40; above 40 olives per hectogram.

5.10.2 Qualitative classification of trade types The following descriptions are adapted from the Standards of the International Olive Oil Council, applicable to table olives for delivery to international trade. More detailed tolerances are given in the Standard. Table olives ready for consumption are classified as first class, standard class, or market class. Stuffed olives may be prepared only from first- or standard-class (green) olives. First-class olives Olives in this class must be prepared using fruit of suitable ripeness, of one sole variety, and having the organoleptic characteristics of this variety in the highest degree. First-class olives must be very uniform in color, taste, appearance, texture, and size. Provided that the general good appearance is not impaired, first-class olives may have very slight variations in color, shape, and firmness of flesh – if these slight variations do not upset the general uniformity – and very slight superficial damage, hardly visible to the naked eye, in the form of scratches or scalds, or that caused by insects or physical knocks. In the case of whole olives stuffed with pimento, very slight defects of color or very slight imperfections in the consistency or placing of the stuffing are permissible. A tolerance of 10% not possessing the required first-class characteristics but having those required for classification as standard class is permissible, excluding such olives admitted into the standard class though in fact belonging to the market class. Batches of table olives (including stuffed olives) meeting the requirements for the first class, but containing no fruit benefiting from tolerances of size or quality and packed in containers of less than 2.5 kg and of perfect appearance, may be offered on the international market under the description ‘extra’. Standard-class olives Olives in this class must be prepared using fruit of suitable ripeness, of one sole variety, and having the organoleptic characteristics of that variety. Standardclass olives ready for consumption must be very uniform in color, taste, appearance, texture, and size. Provided that their general appearance is not affected, standard-class olives may have slight variations in color, shape, and firmness of the flesh – if those slight variations do not upset the general uniformity – and

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slight superficial damage in the form of scratches or scalds or that caused by insects or physical knocks. In the case of whole olives stuffed with pimento, slight imperfections of color or slight imperfections in the consistency or placing of the stuffing are permissible. A tolerance of 10% of olives lacking the required standard-class characteristics but having those required for classification as market class is permissible. Market-class olives Olives in this class must be prepared using fruit of suitable ripeness, of one sole variety, and having the organoleptic characteristics of that variety. They are prepared from fruit that cannot be included in the higher classes but that nonetheless meet the minimum quality requirements of goods recognized as sound, fair, and marketable according to international trade practices. Provided that they do not in any way affect the nature of the product, olives with the following defects or blemishes are allowed: variations of color, shape, firmness of the flesh; defects in the specific flavor of the fruit; damage in the form of scratches or scalds or that caused by insects or physical knocks; and olives not meeting the general specifications for ripeness.

5.11

Recommended storage and shipping conditions

Fresh olives picked at the mature-green or fully-ripe (black) stages can be stored between harvest and processing for a few days to a few weeks, depending on storage conditions. Storage can be used to maintain quality and safety of fresh olives and to extend the processing season while maintaining an orderly flow to the processing plant. Storage conditions and duration can greatly influence the quality of the fresh olives at the time of processing and of their processed products, including oil. Quality attributes of fresh olives include size, color, and freedom from defects (such as mechanical damage, shriveling, surface blemishes, scale and other insect injuries, and chilling injury) and decay. Initial sorting of fresh olives to remove those with serious defects or decay, as well as leaves and twigs, is the first step in successful storage. Fresh green olives should be stored at 5–7.5 °C with 90 to 95% RH; temperatures < 5 °C accelerate the appearance of chilling injury in fresh olives. Optimum CA is 2–3% O2 + 0–1% CO2, which delays senescence and softening for up to 12 weeks at 5 °C and nine weeks at 7.5 °C. O2 < 2% can cause off-flavors. CO2 >5% may increase severity of chilling injury if olives are stored below 7.5 °C for fresh ‘Manzanillo’ green olives before California-style black ripe processing (Kader et al., 1990). Fresh black table olives should be processed as soon after harvest as possible. But, if necessary, black olives can be kept in air or 2% O2 at 5 °C for four weeks or higher depending on cultivar (Agar et al., 1998; Garcia and Streif, 1991). Ripe olives before oil extraction can be stored for the above period even at lower temperatures without negative effects on oil quality (Agar et al., 1999; Kiritsakis et al., 1998).

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5.12

Postharvest biology and technology of tropical and subtropical fruits

Processing

5.12.1 Fresh-cut processing Fresh olives are not edible or suitable for a fresh-cut product. 5.12.2 Other processing practices Some olive cultivars are dedicated to olive oil production. Table olive cultivars are usually larger with a lower concentration of oil. Some dual-purpose cultivars are both large enough for traditional table fruit and have very high oil content. High quality extra virgin olive oils are usually monovarietal or made from varietal blends in order to balance good flavor components with a stable shelf life. Oil quantity and quality are highly dependent on variety, all preharvest factors (climate, soil, cultural practices), the postharvest handling and processing. It has taken centuries for the best oil varieties in the world to develop reputations for fruit yields, oil content, flavor, stability, maturity stage, and ease of harvest.

5.13

Conclusions

Olives are among the oldest of the cultivated tree crops. The processed olive fruit and the extracted oil have played a major role in both ancient and modern cultures. The city of El Djem, Tunisia, the site of the third largest Roman amphitheatre in the world, developed because it was the North African center of olive oil production and trading but interestingly that olive oil was for lamps. In our time, the ‘Mediterranean’ diet is based upon olive oil. Therefore it is surprising that cultivation of the olive, so important for so long, has changed so little over the centuries. However recently, major changes are taking place in olive production toward intensive mechanized production. The major recent change in olive production is in harvesting, the most expensive part of both table and olive oil production. The change is occurring more quickly in oil olives than in table olives as the physiological maturity, and therefore low fruit removal force, and processing methods of olive oil production are suitable to mechanical harvesting. Table olive production, with its earlier harvests, when the fruit is physiologically immature and the fruit detachment force as high as 1 kgF, and the lack of tolerance for bruising and cutting has adapted to mechanical harvesting slowly. In both cases, mechanical harvesting (or, in any case, all available harvest aids) is necessary for economic production.

5.14

References

Agar IT, Hess-Pierce B, Sourour MM and Kader AA (1998), ‘Quality of fruit and oil of black-ripe olives is influenced by cultivar and storage period,’ J Agr Food Chem, 46, 3415–3421.

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Agar IT, Hess-Pierce B, Sourour MM and Kader AA (1999), ‘Identification of optimum preprocessing storage conditions to maintain quality of black ripe “Manzanillo” olives’, Postharvest Biol Technol, 15, 53–64. Garcia JM and Streif J (1991), ‘The effect of controlled atmosphere storage on fruit and oil quality of “Gordal” olives’, Gartenbauwissenschaft, 56, 233–238. Kader AA, Nanos G and Kerbel E (1990), ‘Storage potential of fresh “Manzanillo” olives’, Cal Agric, 44(3), 23–24. Kiritsakis A, Nanos GD, Polymenopoulos Z, Thomai T and Sfakiotakis EM (1998), ‘Effect of fruit storage conditions on olive oil quality’, J Amer Oil Chem Soc, 75, 721–724. Ranalli A, Tombesi A, Ferrante ML and de Mattia G (1998), ‘Respiratory rate of olive drupes during their ripening cycle and quality of oil extracted’, J Sci Food Agric, 77, 359–367. University of California, Davis, Table Olive Fresh Produce Facts at Postharvest Center. Available from: http://postharvest.ucdavis.edu/produce/producefacts.

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Plate VIII

(Chapter 4) Picked Noni fruit on a market stall.

Plate IX (Chapter 9) Bruising and cutting damage produced during mechanical olive harvest in ‘Manzanillo’ table olives destined for California black ripe olive processing.

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Plate X

(Chapter 5) Trunk shaking harvester in high density hedgerow orchard.

(A)

(B)

Plate XI (Chapter 6) Effect of modified atmosphere packaging (MAP) on shelf life of ‘Red Lady’ papaya. Fruit were harvested at colour break stage, treated with fungicide (prochloraz; 100 ppm) and sealed in Cryovac® D-955 film. A. Storage for 12 days in MA plus 2 days in ambient air (2 weeks in total) at room temperature (RT; 26–32 °C, 32–45% RH) (D. V. Sudhakar Rao, unpublished). B. Storage for 21 days in MA plus 7 days in ambient air (4 weeks in total) at 18 °C, 72–80% RH (D. V. Sudhakar Rao, unpublished).

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6 Papaya (Carica papaya L.) S. P. Singh, Curtin University of Technology, Australia and D. V. Sudhakar Rao, Indian Institute of Horticultural Research, India

Abstract: Papaya is a commercial fruit crop in many tropical regions of the world. The fruit is a rich source of vitamins, minerals and dietary antioxidants. Short postharvest life and susceptibilities to physical damage, water loss, chilling injury, diseases, and insectpests are the major postharvest constraints for papaya fruit. This chapter reviews the economic importance, postharvest physiology, maturity indices and effects of pre and postharvest factors on papaya fruit quality. Postharvest quality and marketing losses attributed to non-pathological, pathological and insect-pests problems are discussed. Finally, the processing of fruit into fresh-cut and other products is reviewed. Key words: Carica papaya, maturity, postharvest physiology, quality, storage, fresh-cut.

6.1

Introduction

6.1.1 Origin, botany, morphology and structure The papaya (Carica papaya L.) belongs to the family Caricaceae. It is often called ‘pawpaw’ in Australia and ‘tree melon’ in some other countries, but it is different from the North American ‘pawpaw’ (Asimina triloba Dunal), which is a member of the family Annonaceae. Carica papaya is believed to be native to tropical America, its region of origin perhaps being southern Mexico and neighbouring Central America (Morton, 1987). Spanish explorers took it to the Caribbean and South East Asia in the sixteenth century. The large number of seeds in the fruit and their long viability are among the factors that are thought to have contributed to the wide geographical distribution of the fruit (Chan and Paull, 2008). The papaya is a herbaceous perennial 2–10 m in height. It usually has a single, semi-woody, hollow, erect stem, which terminates with a cluster of large, palmately-lobed leaves with 25–100 cm long petioles and latex vessels in all tissues. Five-petalled, fleshy and slightly fragrant flowers borne in modified

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cymose inflorescences in the axils of leaves are primarily of three types: staminate (male), pistillate (female) and hermaphrodite or perfect (having both female and male organs). The papaya plants may be classified into three categories – male, female or hermaphrodite depending on their flower type. Some plants may bear both male and female flowers, and are called monoecious. Sex expression in papaya is strongly influenced by genotype and climatic conditions. Male and hermaphrodite flowers may undergo sex reversal and morphological changes under the influence of environmental conditions. In the tropics, the interval between seed sowing to the fruit harvesting is generally 8–9 months. The plant flowers and sets fruit throughout the year, so harvesting takes place all year around (Chan and Paull, 2008). The fruit shape varies from oval to somewhat round, pyriform, or elongated club-shaped, depending on the flower-type. The fruit that develops from a female flower is round or ovoid in shape, while a hermaphrodite flower develops into a fruit that is elongated and cylindrical or pyriform in shape. The fruit size may vary from 15–50 cm long, 10–20 cm thick, and 1–3 kg or more in weight (Morton, 1987). Cultivars with small size (~1 kg) fruit are preferred as they are more convenient to pack and market. The immature or mature unripe fruit has green skin and greenish to white flesh and is rich in white milky latex. The skin colour changes to deep yellow or reddish-orange as the fruit ripens. The flesh of the ripe fruit is aromatic, juicy, and yellow, orange, pink or salmon-red in colour with numerous small, dark grey to black, ovoid, peppery seeds clustered in the central cavity, which may be round or star-shaped. These seeds are usually attached to the flesh by soft, white fibrous tissue, and have transparent and gelatinous arils (Morton, 1987). Consignments of black peppercorns have been on occasion fraudulently adulterated with papaya seeds. 6.1.2 Worldwide distribution and economic importance In the past decade, papaya has attained great popularity among growers due to the fact it can be intensively cultivated, its rapid returns and the increased demand for the fresh fruit and its processed products. It is commercially cultivated between 23 ° North and 32 ° South latitude (Chan and Paull, 2008), an area which includes many tropical and sub-tropical countries of the world. World papaya production in 2008 was about 9.1 million tonnes (FAOSTAT, 2010), registering a growth of 40% between 1998 and 2008. The share of different geographical regions in global papaya production is depicted in Fig. 6.1. India was the world’s largest producer of papaya and contributed about 33% of global production in 2008. Brazil, Nigeria, Indonesia, and Mexico were the other leading papaya producing countries (Table 6.1). Other than the top-ten producing countries, papaya is cultivated on a commercial scale in countries such as Peru, Venezuela, China, Thailand, Bangladesh, Cuba, Kenya, Malaysia, El Salvador, Costa Rica, Ecuador, Mozambique, Mali, South Africa, and the United States of America (countries arranged in the decreasing order of their production volumes in 2008, FAOSTAT, 2010). The international trade in papaya fruit has exhibited buoyant growth during

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Fig. 6.1 The share of different geographical regions to the global production of papaya (FAOSTAT, 2010). Table 6.1 Total area and production of papaya in the top-ten producing countries of the world in 2008 Country

Area (thousand hectares)

Production (thousand tonnes)

India Brazil Nigeria Indonesia Mexico Ethiopia D.R. Congo Colombia Guatemala Philippines

80.3 36.8 92.5 9.0 16.1 12.5 13.5 5.5 3.5 9.2

2686 1900 765 653 638 260 224 208 185 183

Source: FAOSTAT, 2010

the past ten years. The export value of papaya increased by 2.7-fold from US$70 million in 1997 to 186 million in 2007. Out of the total papaya export volume of 276 thousand tonnes in 2007, 145 thousand tonnes (53%) was from Central America. In monetary terms, the international export market was dominated by Mexico (US$55 million, 36%), followed by Brazil (US$34 million, 22%), the USA (US$18 million, 10%), the Netherlands (17 million tonnes, 9%), Belize (US$13 million, 8%), and Malaysia (US$8.4 million, 5%). The other major producing countries such as India, Indonesia, and Nigeria contributed very little to the global trade. In 2007, the USA was the largest importer of papaya fruit in the world, and imported about 138 thousand tonnes, which is about 54% of total world imports. Singapore, Canada, the Netherlands, China, the United Kingdom, Germany, Spain, and the United Arab Emirates are the other major papaya importers in the world.

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Table 6.2 Papaya cultivars/hybrids grown in different parts of the world Country

Cultivar(s)

Australia

‘Petersen’, ‘Improved Petersen’, ‘Sunnybank’, ‘Richter Gold’, ‘Arline/57’, ‘Bettina’, ‘Guinea Gold’ ‘NT Red’, and ‘Yarwun Yellow’

Brazil

‘Golden’, ‘Sunrise Solo’, and ‘Tainung-01’

India

‘Honey Dew’, ‘Coorg Honey Dew’, ‘Ranchi’, ‘Washington’, ‘CO–2’, ‘CO–7’, ‘Pusa Delicious’, ‘Pusa Dwarf’, ‘Pusa Majesty’, ‘Surya’, and ‘Red Lady’

Indonesia

‘Dampit’, ‘Jingga’, and ‘Paris’

Malaysia

‘Eksotika’, ‘Eksotika II’, ‘Sekaki’, ‘Batu Arang’, ‘Subang 6’, and ‘Sitiawan’

Mexico

‘Maradol’, ‘Cera’, ‘Chincona’, ‘Gialla’ and ‘Verde’

Philippines

‘Cavite Special’ and ‘Sinta’

South Africa

‘Hortus Gold’ and ‘Honey Gold’

Thailand

‘Khaek Dam’, ‘Kaegnuan’, ‘Koko’, ‘Sainampeung’, ‘Tainung’ series, and ‘Red Lady’

USA (Hawaii)

‘Kapoho Solo’, ‘Sunrise’, ‘Waimanalo’, and ‘Rainbow’

USA (mainland)

‘Betty’, ‘Cariflora’, and ‘Homestead’

Source: Chan and Paull, 2008; Chan, 2009.

A number of papaya cultivars are available in different parts of the world (Table 6.2). The breeding programmes run by many countries have evolved cultivars which are diverse in size, shape, skin and flesh colours, suitability for eating fresh and processing, and resistance to diseases such as papaya ring spot virus (PRSV). ‘Solo’ types are much in demand in the international market due to their small size (Firmin, 1997). Consumers in western countries prefer a fruit without the musky, sweet odour found in some cultivars of South East Asia. The odour is due to methyl butanoate, levels of which are low in ‘Solo’ types, but high in other cultivars (Flath and Forrey, 1977; MacLeod and Pieris, 1983). 6.1.3 Uses, nutritional value and health benefits The ripe papaya fruit is eaten as dessert, in fruit salads, and is processed into a variety of products such as jam, jelly, nectars, ice cream, canned and dried fruit. Mature unripe fruit has culinary value and is used in green salads, candy-making and fermented products. Papaya leaves and flowers are also used in Asian cooking. Papain, a proteolytic enzyme, is extracted from the immature fruit by lancing their surfaces and collecting the white exuding latex, then drying it into a powder. The lanced fruit may be allowed to ripen partially, and can be used to make fruit leathers, candy, papaya powder, and pectin extract. Papain has diverse commercial uses. In the food processing industry, it is used in meat tenderizing and for

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chill-proofing of beer among other applications. Papain has widespread uses in the pharmaceutical and medical industries in manufacturing drugs and other formulations to cure various digestive ailments, in the preparation of vaccines, for deworming cattle, in the treatment of wounds, reducing swelling and fever. Other industrial uses include degumming of silk and softening of wool in the textile industry and tanning in the leather industry. Several cosmetic products such as shampoo, soaps and skin-care products also have papain as an important ingredient. The major producers of crude papain are Democratic Republic of Congo, Tanzania, Uganda and Sri Lanka (Anonymous, 2010). Papaya fruit is low in calories and rich in vitamins and minerals. The average concentration of ascorbic acid (vitamin C) in Hawaiian papaya cultivars ranges from 45.3 to 65.4 mg 100−1 (Wall, 2006). Therefore, one cup of papaya cubes (140 g) can provide about 80–96% of the dietary reference intakes (DRI, established by the US Food and Nutrition Board, National Academy of Sciences) for vitamin C and 8–11% of the DRI for Mg for adult males and females (Wall, 2006). The ascorbic acid (48.4 mg 100 g−1) in the fruit flesh contributed about 97% of the total hydrophilic antioxidant capacity of the fruit (Isabelle et al., 2010). The carotenoids present in the fruit flesh contribute to its vitamin A level and lipophilic antioxidant capacity. The red-fleshed cultivars have high concentrations of lycopene (about 63% of the total carotenoid content) and have relatively lower retinol activity equivalents compared to the yellow counterparts, in which β-cryptoxanthin and β-carotene are the major carotenoid pigments. Lycopene is vitamin A inactive but is a more efficient antioxidant than β-carotene (Di-Mascio et al., 1989) and has been linked with a reduction in the risk of cancer especially lung, stomach and prostate cancers (Giovannucci, 1999). Therefore, the antioxidant activity of red-fleshed cultivars may make a greater contribution to human health than their vitamin A activity (Wall, 2006). Ripe papaya fruit has many medicinal uses. It is a digestive aid and is a stomachic, carminative, diuretic and expectorant. Its applications to combat dysentery and chronic diarrhoea, wounds of the urinary tract, ringworm and skin diseases have also been reviewed elsewhere (Krishna et al., 2008). The extracts from unripe fruit, leaves, seeds, and roots have antimicrobial properties and have been traditionally used to cure several ailments related to digestive and urinary complaints. The abortifacient properties of unripe fruit and seeds make them unsafe for consumption by pregnant women (Krishna et al., 2008).

6.2

Fruit development and postharvest physiology

6.2.1 Fruit growth, development and maturation Botanically, papaya fruit is a fleshy berry. Its growth and development rate depends on the cultivar, age of bearing trees, climatic conditions and the selected maturity index (Selveraj et al., 1982b; Nakasone, 1986). In general, it takes about 140–180 days after anthesis (DAA) to reach full maturity. The pattern of fruit growth corresponds to a single sigmoid growth curve with two major phases. The

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first phase lasts for about 80 days. A large increase in dry weight occurs during the second phase just before maturity (Chan and Paull, 2008). In fact, the fruit accumulates about 50% of its dry matter during this second phase of development (120–168 DAA), the duration of which is less than one-third of the complete fruit developmental period (Calegario et al., 1997). As mentioned previously, the climatic conditions during anthesis and fruit growth have a profound effect on the number of DAA to reach harvest maturity. For instance, in Hawaii (USA), fruit development is normally complete after about 150–164 days, but it is extended by another 14–21 days in colder months. ‘Sunset’ papaya fruit matured in 140 and 180 DAA from June and December flowers, respectively (Zhou and Paull, 2001). The difference in fruit maturation time was due to fruit growth and development being retarded mainly by temperature, and to a lesser extent by tree age and fruit competition. Fruit growth and development is even slower under sub-tropical conditions and may take 190–270 days (Chan and Paull, 2008). During the final phase of maturation (>120 DAA), the skin colour changes from dark green to light green. The appearance of yellow string on the fruit surface marks the completion of fruit maturation and when the yellow colour predominates, the fruit is ripe. Higher yellow colouration at the harvest has been linked to better fruit pulp eating quality. However, the number of days postharvest to reach eatingripe stage decreases as surface colouration at harvest increases. For example, a Venezuelan papaya cultivar ripened normally in 5–7 days when the initial yellow colour intensity on the major part of fruit exceeded the Hunter b* value of 20, whereas those with b* values of 18–20 took about 8–10 days. The majority of fruit with lower b* values at harvest did not ripen normally and those which did took about 11–14 days to reach acceptable ripeness (Peleg and Brito, 1974). Soluble solids concentration (SSC), which remains almost constant during the initial phases of growth (up to 120 DAA), undergoes a dramatic increase during the final growth phase (Ghanta, 1994; Calegario et al., 1997). In a study by Calegario et al. (1997), the increase in SSC observed was from 6% at 120 DAA to 15% at 168 DAA. A minimum of 11.5% SSC is required to meet the Hawaiian grade standards, which corresponds with the 6% skin coloration (Akamine and Goo, 1971a). Studies on sugar metabolism during growth and development of papaya fruit showed that sucrose synthase (SS) activity was very high in young fruit (14 DAA), decreased to about one-fourth of initial activity within 56 DAA and then remained relatively low during the subsequent period of fruit development (Zhou and Paull, 2001). The high levels of SS activity in the initial stages of fruit development seem to play an important role in papaya fruit sink establishment. On the contrary, the activity of acid invertase (AI) was very low in the young fruit and increased four weeks before fruit maturity and commencement of ripening during the last phase of fruit development (90–125 DAA). The increase in AI activity paralleled the increase in sugar accumulation in the fruit. The reduced AI activity two weeks prior to ripening together with an increased sucrose phosphate synthase (SPS) activity may contribute to sucrose accumulation in the vacuole. Papaya mesocarp does not contain measurable quantities of starch and other

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carbohydrate storage compounds. Sugar accumulation in the fruit is mainly reliant on continued sucrose import rather than starch degradation (Zhou and Paull, 2001). 6.2.2 Respiration and ethylene production Papaya is a climacteric fruit (Jones and Kubota, 1940; Nazeeb and Broughton, 1978; Fabi et al., 2007) and exhibits increases in rates of respiration and ethylene production during ripening. The rates of respiration and ethylene production are determined by many factors including cultivar, fruit maturity, and storage conditions. The peaks in rates of respiration and ethylene production coincide with full skin colour development (Jones and Kubota, 1940; Manenoi et al., 2007). The ethylene peak generally precedes the respiratory peak during papaya fruit ripening (Nazeeb and Broughton, 1978; Wills and Widjanarko, 1995; Fabi et al., 2007; Manenoi and Paull, 2007). Rates of respiration and ethylene production began to rise after two days at 22 °C in ‘Rainbow’ papayas harvested at colour-break stage (<10% yellow) and reached their maximum after 10 and eight days, respectively (Manenoi et al., 2007). However, the rate of respiration in relation to skin colour changes and fruit ripening varies greatly among papaya cultivars. The time between the start of skin yellowing and the rise in respiration at 22 °C varied from about two days in ‘Kapoho’ and ‘Sunrise’ to about four days in RL1–3 and eight days in RL1–12 (Zhang and Paull, 1990). Papaya cv. ‘Taiping’ exhibited higher rates of respiration and ethylene production compared to ‘Bentong’. Consequently, ‘Taiping’ ripened in four and six days at 20 and 26 °C, respectively, while ‘Bentong’ took seven and 11 days at the same temperatures (Nazeeb and Broughton, 1978). The number of days to reach respiratory and ethylene climacteric peaks and fruit ripening during postharvest also decreases with the advancement of fruit maturity at harvest. For example, ‘Golden’ papayas harvested at different stages, viz. mature green, up to 15% yellow, up to 25% yellow, and up to 50% yellow, reached the edible-ripe stage after 7, 6, 4, and 3 days at 23 °C, respectively (Bron and Jacomino, 2006). Storage temperature remarkably modulates the respiratory and ethylene production behaviour of papaya fruit (Nazeeb and Broughton, 1978; Lam, 1990), and thus the postharvest life of fruit. The respiratory and ethylene peaks in papaya cultivars, ‘Taiping’ and ‘Bentong’, appeared earlier at higher temperatures and the magnitude of the peaks also increased with temperature. Papaya cv. ‘Taiping’ showed the ethylene peaks after 7, 9, 17, and 28 days when the fruit were stored at 25, 20, 15 and 10 °C, respectively, whereas the respiratory peaks were observed on days 8, 12, 22 and 24 (Nazeeb and Broughton, 1978). Therefore, fruit ripening proceeded at a faster rate at higher temperatures and climacteric peaks were of greater magnitude. The respiration rates of papaya at 10 °C and 15 °C were almost double those at 5 °C (Lam, 1990). Humidity in the storage atmosphere has also been reported to influence the ethylene and respiratory rates of papaya fruit. The number of days to reach CO2 and ethylene peaks were significantly larger under high humidity conditions compared to low humidity conditions (Nazeeb and

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Broughton, 1978). The exogenous application of ethylene has been known to enhance the rates of respiration and ethylene production in papaya fruit, resulting in accelerated and uniform fruit ripening (Nazeeb and Broughton, 1978; Fabi et al., 2007). The removal of ethylene from the storage atmosphere and blocking of its action by the postharvest application of 1-methylcyclopropene (1-MCP) suppress the respiratory and ethylene production in papaya, resulting in delayed fruit ripening. Knowledge of the factors affecting the rates of ethylene production and respiration is therefore pivotal for the development of postharvest strategies aimed to retard them for quality maintenance and enhanced postharvest shelf life. 6.2.3 Biochemical changes during fruit ripening Fruit ripening in papaya involves several biochemical changes that convert mature–hard and inedible fruit into sweet, soft, juicy and aromatic edible fruit. During fruit ripening, chlorophyll in skin tissue is degraded, underlying carotenoids are unmasked and de novo biosynthesis occurs in chromoplasts leading to development of yellow or orange skin colour, depending on the cultivar (Selveraj et al., 1982a; Paull, 1993; Paull et al., 2008). Carotenoids are the major pigments in the skin and flesh of the fruit and variation in carotenoid composition profiles is often present among cultivars (Chandrika et al., 2003; Wall, 2006). The relative amounts of different types of carotenoids determine the skin or flesh colour and its intensity. The flesh colour intensifies parallel to the changes in skin colour during ripening. The major carotenoids present in yellow-fleshed cultivars are β-cryptoxanthin, β-carotene, lutein, and ζ-carotene; while red-fleshed cultivars contain lycopene as the major carotenoid pigment in addition to the presence of others (Chandrika et al., 2003; Wall, 2006). Lycopene is absent in yellowfleshed cultivars as lycopene β-cyclase catalyses conversion of lycopene to β-carotene in these cultivars. Recently, two different genes encoding lycopene β-cyclases (lcy-β1 and lcy-β2) have been characterized from red (‘Tainung’) and yellow (‘Hybrid 1B’) papaya cultivars (Devitt et al., 2010). The lcy-β2 transcript levels in ‘Hybrid 1B’ increased about four-fold from colour break to full ripe stage, while such increase was not noticed in ‘Tainung’ cultivar. The nonfunctional lcy-β2 might be responsible for the accumulation of lycopene in the red-fleshed ‘Tainung’ cultivar (Devitt et al., 2010). In ‘Golden’ papaya, the concentrations of the three main carotenoids, all-trans-lycopene, all-trans-βcryptoxanthin, and all-trans-β-carotene, increased by about 2.5-fold during fruit ripening at 25 °C for 7 days (Fabi et al., 2007). The concentration of total carotenoids, in general, increases during fruit ripening in papaya (Selveraj et al., 1982a; Wills and Widjanarko, 1995; Singh and Rao, 2005a; Fabi et al., 2007). The enzymatic and non-enzymatic modifications in the cell wall carbohydrates matrix are responsible for the tissue softening during fruit ripening. The activities of various hydrolytic enzymes such as pectin methylesterase (PME) polygalacturonase (PG), β-1,4-glucanase, galactosidase, endoxylanase, cellulase, and proteinase and changes in cell wall composition have been associated with the fruit softening in papayas (Paull and Chen, 1983; Lazan et al., 1995, 2004; Ali

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et al., 1998; Chen and Paull, 2003; Shiga et al., 2009). Paull and Chen (1983) reported that PME and cellulase activities gradually increased from the start of the climacteric rise attaining a peak, two days after the respiratory peak. PG and xylanase exhibited an increase during the climacteric and showed a close relationship with the rate of respiration. During the post climacteric phase, the PG declined to a level of one-quarter of peak activity with xylanase activity returning to zero, while proteinase activity declined throughout the climacteric and postclimacteric phases. A recent study has shown that the transcription of a gene (cpPG) encoding PG was ethylene-dependent, and coincided with the enhanced PG activity and flesh softening during fruit ripening (Fabi et al., 2009). Endoxylanase also played a very important role in xylan degradation of the cell wall matrix during the middle and late phases of fruit softening in papaya, but not in the early stages (Manenoi and Paull, 2007). The transcripts levels of CpaEXY1 and activity of endoxylanase increased during the climacteric rise in the rates of respiration and ethylene production during fruit ripening and also coincided with the firmness decline. The activity of β-galactosidase also increased about four- to eight-fold during the early stages of fruit ripening and coincided with the ripening phase when the fruit firmness begin to decline more rapidly (Ali et al., 1998). The inner mesocarp showed faster fruit softening compared to the outer part and was attributed to a lack of synchronization of cell-wall degradation processes in these regions. Furthermore, the activities of PG and β-galactosidase increased with the increase in tissue depth of mesocarp, resulting in the differential tissue softening in fruit (Lazan et al., 1995, 2004). The increased solubility and depolymerization of pectins and hemicelluloses has been linked with the fruit softening in papayas (Paull et al., 1999; Ali et al., 2004). During fruit ripening, pectin molecular size decreased with a 6-fold increase in water-soluble pectin. The hemicelluloses also showed a significant change in the molecular size with an increase in solubility of hemicellulose in KOH fractions (Paull et al., 1999). The typical changes occurring in the cell wall of ripening fruit are increases in the levels of polyuronides (UA, uronic acid) or neutral sugars (NS) (Lazan et al., 2004). Most of the polyuronides (~75%) were attributable to polymers that are water-soluble. There was a loss of about 25% of UA from the cell wall materials during fruit ripening and in the fully ripe fruit, soluble polyuronides accounted for about 85% of the total polyuronides compared to about 46% and 62% in unripe (5% yellow-skin) and half-ripe (50% yellow-skin) fruit, respectively. The ratio of UA/NS also decreased from 3.7 to 2.4 during ripening, indicating that chelator-soluble pectin polymers that were solubilized from alcohol-insoluble solid contained increasingly greater proportion of neutral sugars (Lazan et al., 2004). The concurrent solubilization and depolymerization of pectin and hemicellulose polymers are therefore responsible for the destabilization of the complex carbohydrates matrix in the fruit cell wall, causing tissue softening. The soluble sugars levels increase significantly during the final phase (~110 DAA) of fruit development in papaya. Sucrose contributed to about <18% of the total sugar content at 110 DAA, but increased rapidly to make up 80% of the sugars at about 135 DAA (Chan et al., 1979). Postharvest fruit ripening involves a small

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change (1–2%) in the soluble sugars levels in papaya fruit (Paull, 1993; Zhou and Paull, 2001). Papaya cultivars have also been reported to differ in the relative amounts of sucrose to total sugars. For instance, average sucrose concentration in ‘Kapoho’ cultivar was significantly higher than ‘Sunset’ ‘Waimanalo’, ‘UH 801’ and ‘Line 8’ cultivars. The contribution of sucrose to total sugars either decreased slightly in some cultivars or remained unchanged in others during the seven days of fruit ripening period (Zhou and Paull, 2001). Fabi et al. (2007) reported that sugars composition profile also changed during seven days of fruit ripening in ‘Golden’ papaya; the concentration of sucrose increased during the first three days of ripening and then showed a continuous decline during the next four days. On the other hand, the concentrations of fructose and glucose increased throughout the fruit ripening for seven days in the same cultivar. A large increase in acid invertase (AI) activity and decreases in activities of sucrose synthase and sucrose phosphate synthase have been reported during postharvest fruit ripening in papaya (Zhou and Paull, 2001). The higher AI activity may be associated with the enhanced cleavage of sucrose into glucose and fructose during papaya fruit ripening (Fabi et al., 2007). The low titratable acidity (TA) in papaya fruit limits its role in influencing fruit flavour. A general trend of either slight decrease or no change in TA has been noticed during fruit ripening in papaya (Selveraj et al., 1982a; Singh and Rao, 2005a; Nunes et al., 2006; Azevedo et al., 2008). Citric and malic acids are the predominant organic acids that contribute almost equally to the total acidity. The other organic acids present in minor concentrations include ascorbic, quinic, succinic, tartaric, oxalic, galacturonic, α-ketoglutaric and fumaric acids (Chan et al., 1979; Hernandez et al., 2009). Contrary to TA, the concentration of ascorbic acid increases during fruit ripening in papayas (Selveraj et al., 1982a; Wills and Widjanarko, 1995; Singh and Rao, 2005a). The increases in concentrations of ascorbic acid and carotenoids contribute to the increased hydrophilic and lipophilic antioxidant capacity of fruit a respectively. Papaya fruit also contains high amounts of benzylglucosinolates (BG) and benzyl isothiocyanates (BITC) and these compounds are also important from a nutritional viewpoint. The BG levels increased in the fruit pulp during the late stages of fruit ripening, while no significant change occurred in BITC (Rossetto et al., 2008). The ripening process, therefore, improves the nutritional quality of papaya fruit, in addition to other favourable changes such as skin colour and flesh softening. The production of aroma volatile compounds during fruit ripening also determines the flavour of fruit. Many volatile compounds (~300) which contribute to the aroma of fruit have been identified and quantified from different cultivars (Flath and Forrey, 1977; MacLeod and Pieris, 1983; Heidlas et al., 1984; Flath et al., 1990; Pino et al., 2003). Linalools, BITC, methyl butanoate and ethyl butanoate were the most abundant volatile compounds, depending upon the cultivar and geographical region. For example, in Hawaiian papaya, terpenoids were the most abundant group of volatile components (81% of the total volatiles) (Flath and Forrey, 1977). The most abundant aroma volatile compounds, linalool and BITC, in the ripe ‘Solo’ papaya contributed about 68% and 13% to the total volatiles, respectively. Both compounds were present in glycosidically bound form in the intact fruit and were released by

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the activity of β-glucosidase enzyme during tissue disruption (Heidlas et al., 1984). The relative amounts and total concentrations of volatile compounds have been reported to vary with the stage of fruit ripeness (Katague and Kirch, 1965; Flath et al., 1990). The concentration of the linalool increased about 400-times from mature green stage to full ripe stage, while the benzyl isothiocyanate increased by about seven-fold during the same time (Flath et al., 1990). In a Sri Lankan cultivar, the principal volatiles (52% of the total volatiles) were represented by esters; the methyl butanoate being the major aroma compound imparting sweaty odour to the fruit (MacLeod and Pieris, 1983). The presence of BITC was also relatively lower (1.5%) compared to 13% in ‘Solo’ papayas (Flath and Forrey, 1977). The Sri Lankan and Hawaiian papaya cultivars thus showed a contrast in the composition of their aroma volatile profiles. The volatile components of ‘Maradol’ cultivar were also dominated by esters (62, about 40.8% of the total volatiles), with the major representatives being methyl butanoate and ethyl butanoate (Pino et al., 2003). The effects of various preharvest and postharvest factors on the production of aroma volatile compounds in papaya require more investigations.

6.3

Maturity indices

Harvesting at appropriate maturity is important for development of excellent eating quality of papaya fruit and for better consumer outcomes. Fruit harvested before optimum maturity fail to ripen properly, with unacceptable skin and flesh colour, lower SSC and rubbery texture (Paull et al., 1997). The skin colour break is considered the best harvest maturity index for papaya fruit, depending on the destination of fruit (Akamine and Goo, 1971a; Selveraj et al., 1982b). The appearance of yellow string on the blossom-end of the fruit surface indicates the optimum maturity for long-distance transport. In Hawaii, fruit must reach 11.5% SSC to meet the quality standard and the fruit harvested at 6% surface coloration have been shown to meet this standard (Akamine and Goo, 1971a). Abrasion injury is a major problem in fruit harvested at <25% surface colour (Quintana and Paull, 1993). For local markets, fruit harvesting may be delayed till the fruit surface is ≥50% yellow. However, the postharvest life of fruit declines with the on-tree advancement of fruit maturity (Bron and Jacomino, 2006), while fruit quality in terms of skin and pulp colour and soluble sugars improves with the delayed harvesting. The susceptibility to fruit fly attack increases when the surface yellowing exceeds >25% (Seo et al., 1982). The fruit with 40 to 60% skin yellowing are also more prone to impact and compression injuries (Quintana and Paull, 1993) and diseases (Alvarez and Nishijima, 1987) during postharvest handling.

6.4

Preharvest factors affecting fruit quality

Orchard practices such as defoliation, fruit thinning and fertilization have been shown to influence fruit quality in papayas. Leaf pruning of ‘Solo’ papaya to

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15 functional leaves did not adversely affect the production and SSC of the fruit (Ido, 1976). The removal of 50% of the leaves has been reported not to influence fruit set and SSC of fruit, but excessive pruning involving removal of 75% of the leaves reduced the fruit set, flesh dry matter and SSC of ripe fruit. However, continual defoliation appeared to reduce the supply of photosynthates below the compensation point resulting in smaller fruit with lower SSC (Zhou et al., 2000). Fruit thinning is another practice that can ensure an optimum leaf to fruit ratio, thereby maintaining a favourable source–sink relationship and achieving desirable fruit size, uniform fruit production and fruit sweetness (Zhou et al., 2000). Fruit thinning to one fruit per node level has been reported to increase fruit size without any effect on sugar content of fruit (Martinez, 1988). The beneficial effects of fruit thinning in ‘Sunset’ papaya included increased new fruit set and higher SSC in ripe fruit (Zhou et al., 2000). The removal of old fruit stimulated fruit development and accumulation of sugars in young fruit and also resulted in increased fruit size. These authors concluded that each mature leaf can provide sufficient photosynthate for growth and development of about three fruit in the cultivar ‘Sunset’ under Hawaiian conditions. A comprehensive study on the effects of fertilization on papaya fruit quality and the mineral composition of fruit was conducted by Qiu et al. (1995) in Hawaii. Papaya trees that were six months old and had just begun to flower, received additional fertilization with CaCO3 (48.5% CaO) at the rate of 192 g tree−1 per month, KCl (61% K2O) at the rate of 197.5 g tree−1 per month, and urea (46% N) at the rate of 158.7 g tree−1 per month. The extra application of nitrogen significantly delayed skin and flesh colour development during fruit maturation and postharvest fruit ripening. Calcium fertilizer treatment alone or in combination with potassium significantly increased Ca concentration in the fruit mesocarp, while potassium fertilization alone reduced the Ca concentration in the fruit mesocarp. The presence of a higher concentration of Ca in the mesocarp tissue was positively correlated with higher firmness retention in the ripe fruit. For instance, Ca and Ca plus K fertilization significantly increased fruit firmness with an average deformation force of 76 and 78 N, respectively, against 68 N in the control treatment. Fruit softening was delayed during the ripening process when the mesocarp Ca concentration was ≥130 μg g−1 FW. The fruit with the mesocarp Ca concentrations lower than this threshold were more susceptible to soft fruit disorder. The strategy to increase the Ca concentration in the fruit mesocarp by spraying papaya fruit six times over 12 weeks with CaCl2 (2% w/v) during fruit growth and development was not successful (Qiu et al., 1995). Boron (B) fertilization is also important as its deficiency causes a serious ‘bumpy’ fruit disorder (Wang and Ko, 1975). The localised areas of fruit that are deficient in boron cease to increase in size, resulting in an uneven growth of fruit. Proper fertilization of papaya trees during fruit growth and development with boron alleviates this disorder. Foliar applications of borax (0.25%) and soil application of 1–3 kg ha−1 elemental boron have been effective in preventing the development of this disorder (Nishijima, 1993). A boron concentration in the leaf petiole of more than 25 ppm is essential to reduce the incidence of this disorder. A

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recent study in India has also shown that the fertilization of ‘Surya’ and ‘Red Lady’ cultivars that were grown in a boron-deficient soil, with 2 kg boron per hectare (as Colemanite) significantly increased the Ca concentration in fruit tissue, improved skin smoothness, fruit size and seed health resulting in better fruit yield and quality (Raja, 2010). The postharvest shelf life in ‘Surya’ and ‘Red Lady’ cultivars was also enhanced to 10 and 12 days in the B-fertilized fruit against four and six days in control, respectively. Preharvest factors also affect the development of superficial skin freckles or spots on fruit surface. The skin freckles begin to develop in half-mature fruit and their size and incidence increases during the final phase of fruit maturation. The exposed fruit surface is more prone to skin freckles. The development of freckles has been physiologically associated with a rapid growth rate in the final phase of fruit development, a thicker cuticle, and greater latex soluble solids leading to a higher osmotic, and hence turgor pressure in the laticifer (Eloisa et al., 1994). Low and high temperatures, two months before harvest, increased stress leading to occasional rupture of laticifers and thus development of skin freckles. Bagging of fruit before the final growth phase significantly reduced freckle incidence and can be an important control measure to prevent the losses caused by the skin freckles (Eloisa et al., 1994).

6.5

Postharvest factors affecting fruit quality

6.5.1 Temperature management The management of storage temperature can regulate the respiratory and ethylene production behaviour of papaya fruit, thereby offering an opportunity to increase the postharvest life of fruit through retardation of these processes (refer to section on respiration and ethylene production). Therefore, low temperature storage is recommended to retard the physiological activity of fruit and extend the storage/ shipping/shelf life potential. The optimum storage conditions for papaya fruit (breaker stage) are 7 °C temperature and 85–90% relative humidity (Paull, 1999). The tolerance of papayas to temperatures below 10 °C varies with the maturity of the fruit and the duration and temperature of exposure (Chen and Paull, 1986). For example, mature green fruit can be stored at 10 °C for < 14 days and the fruit ripen at 22.5 to 27.5 °C in 10–16 days. Fruit at colour break stage can be stored at 7 °C for 14 days, while quarter-ripe (25% skin yellowing), half-ripe (50% yellow) and ¾ ripe-fruit (75% yellow) can be stored at 7 °C for less than 21 days (Paull et al., 1997). The storage of fruit below optimum temperature or even at optimum temperature for a longer duration leads to the development of chilling injury symptoms (Thompson and Lee, 1971; Chen and Paull, 1986; Chan, 1988; Paull et al., 1997; Wills and Widjanarko, 1997). Symptoms of chilling injury are skin scald, water soaked areas and hard lumps in the mesocarp and failure to ripen properly. The fruit also has increased susceptibility to diseases. The development of water-soaked lesions on the skin appears during cold storage, and the above

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described symptoms manifest and intensify when the fruit are transferred to ambient conditions for ripening. As the storage temperature decreased from 20 °C to 5 °C during 7 to 21 days of storage, the number of days required for fruit ripening and severity of chilling injury also increased when the fruit were transferred to 20 °C (Wills and Widjanarko, 1997). Chilling injury symptoms have even been observed on ripe fruit stored for seven days at 15 °C (Nazeeb and Broughton, 1978). ‘Bentong’ and ‘Taiping’ papaya cultivars stored below 15 °C for more than seven days developed chilling injury and failed to ripen when returned to 20 and 25 °C (Nazeeb and Broughton, 1978). However, Thompson and Lee (1971) reported that Trinidad ‘Solo’ papaya stored at 13 °C for 21 days ripened normally when transferred to ambient conditions (25–28 °C). These contradictions in the literature may arise due to the differences in the maturities of the fruit used in the studies.The susceptibility to chilling injury might have been enhanced due to the use of mature green fruit in the experiments by Wills and Widjanarko (1997) and Nazeeb and Broughton (1978). The storage potential of papaya fruit therefore depends on the fruit maturity, storage temperature and duration of storage. A study on the effects of simulated commercial temperature regimes during air-transport on the quality of papaya fruit throughout the handling chain showed that the fruit handled in the fluctuating cold or warm temperature regimes normally experienced during the actual conditions lost more weight, developed objectionable colour, were softer and more shrivelled, had more decay, and had lower soluble solids, acidity and ascorbic acid contents than papayas handled in the semiconstant temperature regime (12 °C for 52 h, 8 °C for 24 h and seven days at 20 °C) (Nunes et al., 2006). A brief exposure of fruit to 1 °C for two hours developed chilling injury symptoms during seven days of ripening period at 20 °C in ‘Redy Lady’ papayas handled in a fluctuating cold temperature regime (at 8–15 °C for 76 h). Therefore, proper temperature management without any significant deviations from the recommended conditions is crucial to provide consumers with high quality fruit and limit the possibility of rejection of papaya consignments. Ways to reduce the incidence and severity of chilling injury are discussed in more detail in section 6.6.1. 6.5.2 Physical damage The fruit skin in papaya is delicate in nature which predisposes it to physical damage that leads to excessive weight loss and pathogen infections (Alvarez and Nishijima, 1987; Quintana and Paull, 1993; Paull et al., 1997). The fruit at ripe stage show some sunken areas that fail to degreen, called ‘green islands’ that are primarily caused by mechanical injury. Mechanical injury has been reported in 14.8% of the papaya shipments evaluated in New York markets (Quintana and Paull, 1993) and is one of the major causes of postharvest losses in papaya (Paull et al., 1997). The skin injury caused by mechanical damage increased in fruit as it moved through postharvest handling system. A five-fold increase in the skin injury was observed from at harvest to after packing stage in a commercial packing house (Quintana and Paull, 1993). The fruit samples from the sides of field bins

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showed skin injury, but it was absent in fruit sampled from the centre of bins. This study clearly indicated that abrasion and puncture injury were more important than impact injury for papaya fruit. Fruit with 60% or more colour are susceptible to impact injury causing internal bruising (Paull et al., 1997). However, the impact and abrasion injury in papaya fruit did not stimulate the respiration rate or ethylene production during ripening. The severity of skin injury could be reduced by waxing of fruit with a carnaubabased wax (FMC-819) or a polyethylene-paraffin wax (FMC-820) applied before or after heat treatment (Quintana and Paull, 1993). Papaya fruit should be carefully handled postharvest during all stages of supply chain to prevent bruising on the fruit surface. Bin liners may be used to reduce the damage. The adoption of bins made of materials less prone to have rough surfaces can reduce mechanical injury (Paull et al., 1997). The use of cushioning material in packing can also minimise bruising damage. The identification of critical points in handling system associated with mechanical injuries and taking corrective or precautionary measures can help reduce the qualitative and quantitative losses in papaya fruit. 6.5.3 Weight loss Weight loss in papayas occurs mainly due to water lost through the skin and the stem–scar (Paull and Chen, 1989). The amount of weight loss in papayas is dependent on several factors such as cuticle thickness, fruit maturity, storage conditions (temperature and relative humidity) and postharvest treatments (Paull and Chen, 1989; Singh and Rao, 2005a; Nunes et al., 2006). Weight loss symptoms in papaya fruit are shrivelling, low gloss, and rubbery texture. The loss of about 8% of initial weight from ‘Sunset’ and ‘Sunrise’ papayas harvested at mature green stage produced these symptoms and rendered the fruit unacceptable (Paull and Chen, 1989). The cuticle thickness has been found to decrease when the fruit skin colour changes from half yellow to yellow. Therefore, fruit harvested at advanced maturity exhibit more weight loss than the less mature fruit during the postharvest. The maintenance of high relative humidity (>90%) has been reported to be beneficial to reduce postharvest weight loss, thus preventing the development of associated symptoms and resulting marketing losses (Nunes et al., 2006). Modified atmosphere packaging (MAP) is another effective way to reduce the weight loss of papaya fruit (Paull and Chen, 1989; González-Aguilar et al., 2003; Singh and Rao, 2005a, 2005b). The weight loss in papaya fruit during two weeks at 10 °C plus two days at ambient could be reduced by 14–40% in waxed fruit and by about 90% in plastic shrink wrapped fruit (Paull and Chen, 1989). The packaging of individual papaya fruit harvested at colour-break stage in a 25 μm thick low density polyethylene (LDPE) film or Pebax-C® film significantly reduced the weight loss during 14 days storage at ambient conditions (27–32 °C and 50–55% RH) and 20 days storage at 13 °C plus seven days at 20 °C (Singh and Rao, 2005a). The individual shrink-wrapping of ‘Solo’ papayas in Cryovac® D-955 or LDPE (25 μm thick) significantly reduced the weight loss to <2% during 14 days storage at ambient conditions (27–32 °C and 50–55 % RH) against 20% weight loss in

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control fruit (Singh and Rao, 2005b). The development of off-flavour caused by accumulation of CO2 concentration higher than 7–8% has also been reported in papaya fruit wrapped in plastic films (Paull and Chen, 1989; Singh and Rao, 2005a). The adoption of MAP technology should therefore be considered carefully to prevent the build-up of CO2 concentration and/or exhaustion of O2 below a certain level capable of inducing anaerobiosis. 6.5.4 Storage atmosphere Modified/controlled atmospheres (MA/CA) have been used for long distance shipping of tropical fruits. The modification of storage atmospheres with low O2 and high CO2 extends the storage/shipping potential of tropical fruits including papaya (Akamine, 1959; Hatton and Reeder, 1969; Maharaj and Sankat, 1990; Cenci et al., 1997). The ideal storage atmospheres for papaya fruit should range between 2–5 kPa O2 and 5–8 kPa CO2 (Yahia, 1998; Yahia and Singh, 2009). However, the response of fruit to CA/MA depends on several other factors including cultivar, fruit maturity and storage temperature (Yahia, 1998). Delayed fruit ripening and reduced decay in papaya were the major benefits associated with CA/MA. ‘Solo’ papaya fruit kept in 10 kPa CO2 at 18 °C for six days showed less decay compared to those held in normal air or atmospheres with higher levels of CO2 (Akamine, 1959). Papaya fruit held in 1 kPa O2 and 3 kPa CO2 at 13 °C for three weeks and then ripened at 21 °C showed 90% acceptability, whereas 10% of the fruit held in normal air for the same duration were acceptable (Hatton and Reeder, 1969). Delayed fruit ripening in ‘Bentong’ and ‘Taiping’ cultivars in Malaysia was achieved by removal of ethylene from the storage atmosphere and enrichment of the storage atmospheres with 5% CO2 at 15 °C for about 25 days (Nazeeb and Broughton, 1978). The removal of CO2 from the storage atmosphere accelerated the onset of ethylene rise in both cultivars and fruit ripened at a faster rate. Maharaj and Sankat (1990) reported that ‘Known You No. 1’ and ‘Tainung No. 1’ papayas at the colour break stage could be stored for 29 days in atmospheres containing 1.5–2.0% O2 and 5% CO2 at 16 °C, compared to 17 days in air. Similarly, the storage life of ‘Sunrise’ papaya could be extended to 31 days at 10 °C in atmospheres containing 8% CO2 and 3% O2 and fruit ripened normally in five days at 25 °C (Cenci et al., 1997). In addition to delayed fruit ripening, CA/MA have been found very effective to alleviate chilling injury in some tropical fruits (Yahia, 1998). However, CA containing low O2 (1.5 to 5%) with or without high CO2 (2 or 10%) did not reduce chilling injury symptom development in ‘Kapoho’ and ‘Sunrise’ papayas (Chen and Paull, 1986). The exposure of ‘Sunrise’ papayas to an insecticidal atmosphere (0.17 to 0.35 kPa O2, balance is N2) up to five days at 20 °C delayed fruit softening without any external or internal injury. The development of a very weak fermentative odour occurred after three days and its intensity increased with the increase in exposure period to low O2 (Yahia, 1991, 1993; Yahia et al., 1992). Therefore, the tolerance to these insecticidal atmospheres was less than three days for papaya fruit. Hypobaric storage has also been suggested to extend storage life and reduce the decay incidence in papaya. The exposure of papaya fruit to subatmospheric

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pressure (20 mm Hg, 10 °C and 90–98% RH) for 18–21 days during shipment in hypobaric containers from Hawaii to Los Angeles and New York inhibited both fruit ripening and disease development (Alvarez, 1980). The storage conditions after removal from the hypobaric containers did not affect the ripening process. The disease incidence was significantly reduced in the hypobaric-stored fruit; these fruit had 63% less peduncle infection, 55% less stem-end rot and 45% fewer fruit surface lesions than those stored in a refrigerated container at normal atmospheric pressure (Alvarez, 1980). The inhibitory effect of hypobaric storage on the disease development in papaya was further confirmed by Chau and Alvarez (1983). The fruit artificially inoculated with Colletotrichum gloesporioides held at 15 mm Hg at 10 °C for three weeks, and then ripened at ambient conditions for five days showed less anthracnose than the control fruit. A significant delay in the infection progress on fruit has been reported under hypobaric conditions (Chau and Alvarez, 1983). The gaseous atmosphere surrounding a fruit can also be modified passively or actively by packaging of an individual or a group of fruit in polymeric films. In passive MAP, the O2 levels are depleted and the CO2 levels increase inside the package due to fruit respiration. Active MAP involves the flushing of a mixture of gases with desired concentrations so that an equilibrium modified atmosphere is established rapidly. MAP also enriches the surrounding atmosphere with high humidity that results in reduced water loss, increased shelf life and better textural properties (Singh, 2010). The compositions of atmosphere inside the MA packs is dependent upon several factors such as film permeability to O2, CO2, and water vapour, produce respiration and the influence of temperature on these processes. Therefore, choice of an appropriate packaging film is a key factor in order to maintain optimum MA. The use of polymeric films to achieve atmospheric modification has been demonstrated to extend the storage life of papaya fruit (Paull and Chen, 1989; González-Aguilar et al., 2003; Singh and Rao, 2005a; Singh and Rao, 2005b). MAP of papaya with Cryovac® D-955 film increased the shelf life of fruit to two weeks at room temperature (26–32 °C, 32–45% RH) and up to four weeks at 18 °C, 72–80% RH (see Plate XI in the colour section between pages 238 and 239). MA (3–5 kPa O2 and 6–9 kPa CO2) were created inside the LDPE (43 μm thick) package during storage of ‘Sunrise’ papayas at 10 °C for 32 days and did not result in any off-flavour development (González-Aguilar et al., 2003). Similarly, the individual packing of ‘Solo’ papaya in a LDPE (25 μm thick) film created the MA containing CO2 and O2 levels in the range of 3–7% and 8–15%, respectively at 7 or 13 °C during 20–30 days storage, while Pebax-C® film maintained 2–3% CO2 and 10–12% O2 (Singh and Rao, 2005a). The internal concentration of CO2 more than 7–8% resulted in development of off-flavour when the fruit were wrapped in plastic films (Paull and Chen, 1989). The range of CO2 concentration (8–10%) was slightly higher in the atmospheres generated inside the polypropylene (PP) film compared to LDPE and Pebax-C® films (Singh and Rao, 2005a). Thus, the development of off-flavour has been reported in the fruit packed in the PP film. The concentration of gases in the MA packs and their

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effects on fruit flavour should therefore be closely monitored by considering the multiple variables such as fruit maturity, storage temperature and potential temperature fluctuations in the supply chain.

6.6

Physiological disorders

6.6.1 Chilling injury Chilling injury is the major postharvest physiological disorder limiting the storage and transport of papaya fruit at low temperature. Symptoms of chilling injury and a discussion of the effects of low temperature storage on development of the disorder can be found in section 6.3. The recommended conditions for papaya fruit storage are: temperature 7–13 °C relative humidity 90–95% (Paull, 1999; Chen et al., 2007). However, chilling injury can occur under these conditions, as the duration of exposure to low temperature and level fruit maturity determine its incidence and severity in papaya fruit (Wills and Widjanarko, 1997; GonzálezAguilar et al., 2003; Singh and Rao, 2005a). This section will mainly focus on the strategies that have been tested to alleviate chilling injury in papaya fruit. The best method to alleviate chilling injury is to avoid the exposure of fruit to the storage temperatures and durations that cause it. Optimum storage conditions are primarily governed by the fruit maturity. The chilling tolerance in papaya fruit increases as the fruit ripens (Chen and Paull, 1986). For instance, fruit harvested at mature green stage should not be stored at temperatures below 10 °C and should not be stored for more than 14 days at 10 °C. The fruit showing one-quarter, half and three-quarters skin yellowing should not be stored at 7 °C for more than 21 days (Paull et al., 1997). Fully-ripe fruit can be stored at 1–3 °C for more than a week (Chen et al., 2007). Short-term exposure of less ripe papaya fruit to very low temperatures during commercial handling can also induce chilling injury symptoms in the fruit that were otherwise kept at optimum storage conditions (Nunes et al., 2006). Temperature fluctuation during postharvest handling should therefore be minimised to prevent the fruit quality losses. Postharvest heat treatments and temperature preconditioning have been known to enhance the chilling tolerance of papaya fruit. Pérez-Carrillo and Yahia (2004) showed that postharvest exposure of papaya fruit to dry air (50% relative humidity) at 48.5 °C for 4 h was safer than the moist air (100% relative humidity) at the same temperature. The dry air treatment alone or in combination with a fungicide, thiabendazole, decreased the severity of the chilling injury and inhibited fungal growth in ‘Maradol’ papaya during six weeks storage at 5 °C (Pérez-Carrillo and Yahia, 2004). The temperature preconditioning involves the exposure of the fruit to temperatures slightly above the critical chilling temperature for a short duration and that increases the resistance in fruit during subsequent storage at lower temperature. The temperature preconditioning increased the fruit ripeness in papaya which imparted tolerance to chilling stress as the sensitivity of fruit to chilling injury depends on the fruit maturity (Chen and Paull, 1986; Chan, 1988). The modification of storage atmosphere with low O2 alone or in combination with

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high CO2 has not been beneficial to alleviate the chilling injury in papaya fruit (Chen and Paull, 1986). MAP, seal packaging, waxing and treatment with methyl jasmonate have been found to be effective in alleviating chilling injury in papaya fruit. The postharvest treatment of ‘Sunrise’ papaya fruit with methyl jasmonate vapours (10−5 or 10−4 M) for 16 h at 20 °C has been reported to reduce chilling injury during 14–32 days storage at 10 °C and four days shelf life at 20 °C (GonzálezAguilar et al., 2003). The combination of MAP using LDPE film with methyl jasmonate treatment significantly improved the quality retention of fruit with lower severity of chilling injury and better visual quality of fruit. Similarly, the individual packing of ‘Solo’ papaya in LDPE or Pebax-C® film significantly reduced the incidence of chilling injury during 30 days of storage at 13 °C and the fruit ripened normally in seven days at 20 °C, while non-packed fruit showed these symptoms after 14 days of storage at 13 °C (Singh and Rao, 2005a). Though, MAP also prevented the appearance of chilling injury in these fruit during cold storage at 7 °C for 30 days, but the fruit failed to ripen properly showing uneven surface colour development and skin bronzing when these were transferred to ambient conditions. Individual shrink wrapping of fruit with LDPE or Cryovac® D-955 film significantly alleviated chilling injury symptoms in ‘Solo’ and ‘Red Lady’ papayas during four weeks storage at 13 °C (Singh and Rao, 2005b; Sudhakar Rao unpublished). These studies suggest that maintenance of high humidity by MAP could be the major factor contributing to the alleviation of chilling injury in papaya fruit. 6.6.2 Soft fruit Soft fruit is another problem encountered during the payapa postharvest supply chain. The problem of soft fruit is sporadic in nature and appears most commonly in the autumn in Hawaii, USA. Some batches of fruit ripen very rapidly, limiting the long–distance transport and marketing of fruit (Paull et al., 1997). This problem may be caused by bruising or crushing injury during handling, or, as mentioned in section 6.4, by low Ca levels in the fruit (Qui et al., 1995; Paull et al., 1997). The concentration of Ca in the fruit mesocarp has been positively correlated with the retention of firmness during ripening. Fruit with high Ca concentration (>130 μg g−1) are expected to be less susceptible to soft fruit problem (Qui et al., 1995). The uptake of Ca in papaya fruit is influenced by the preharvest environmental conditions and the fertilisation (Qui et al., 1995). The Ca concentration generally varies with the harvest date and it can result in the problem of soft fruit only in a particular season. Soil application of Ca is effective to raise its levels in the mesocarp and can possibly reduce the problem of soft fruit. Careful postharvest handling to prevent bruising and compression can also be helpful to mitigate the soft fruit.

6.7

Postharvest pathological disorders

Postharvest losses due to diseases can reach about 93% depending upon the postharvest handling and packing procedures (Alvarez and Nishijima, 1987). The

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inspection of shipments that had arrived in New York terminal markets revealed that anthracnose rot caused by Colletotrichum gloeosporiodes affected 62% of shipments, while other diseases such as Rhizopus rot, stem-end rot and grey mould affected about 35% of the shipments (Cappellini et al., 1988). Californian inspections also showed that 73% of the inspected cartons have decay and mould growth and 52% had sunken defects (Paull et al., 1997). These statistical figures on postharvest losses caused by decay in papaya clearly demonstrate the scale and importance of this problem. Postharvest diseases of papaya fruit can be categorised into three groups: fruit surface rots, stem-end rots and internal fruit infections (Alvarez and Nishijima, 1987). The fruit surface rots are further of two types depending upon the nature of pathogen. The first group includes the fungal pathogens which invade the immature fruit still attached to the plant in the orchard. Anthracnose, chocolate spot, Phytophthora fruit rot and Cercospora black spot are the examples of this group. The symptoms of Phytophthora rot and Cercospora black spot are not a major problem during postharvest handling of fruit because the symptoms appear on fruit before harvest and the fruit can be culled in the packinghouse. The second group of surface rots includes the weak fungi that infect the fruit through various wounds or injuries occurring during and after harvest, for example, Mycosphaerella, Phomopsis, Alternaria, Fusarium and Guignardia (Alvarez and Nishijima, 1987). Anthracnose rot, caused by a fungus Colletotrichum gloeosporiodes (Penz.) Sacc., is the major postharvest disease in papaya fruit. The infection occurs on the developing fruit in the field, but it remains latent until the fruit begin to ripen. The symptoms appear on fruit surface in the form of round, water-soaked and sunken spots. Several small spots may enlarge and coalesce to form a bigger lesion that can be as large as 5 cm in diameter. These lesions are light brown to salmon colour initially and eventually turn dark brown or black. Although they are sunken, they rarely extend deep into the flesh tissue. Chocolate spot is also caused by C. gloeosporiodes, but the initial symptoms are superficial reddish brown lesions. These lesions become sunken with water-soaked margins as the fruit ripening progresses. Among the other surface rots, dry rot and wet rots are caused by Mycosphaerella sp. and Phomopsis sp., respectively. The dry rot symptoms include surface lesions with brown and translucent margins. The wet rot causing Phomopsis sp. is frequently associated with the stem-end rots. The other fungi causing stem-end rot are Botryodiplodia theobromae, Alternaria alternata, and Mycosphaerella sp. The spores of these fungi enter through the crevices between the fruit peduncle and the flesh, producing stem-end rot symptoms. The affected area is soft and translucent, and the rot progresses rapidly from the surface into the fruit cavity. Another common fruit rot is caused by a fungus, Rhizopus stolonifer, which penetrates through wounds and causes fruit rotting without affecting the fruit cuticle. It is considered one of the most destructive postharvest fungal pathogens of papaya fruit due to its ability to rapidly develop and spread. Internal fruit infections are mainly caused by fungi such as Penicillium sp., Cladosporium sp., and Fusarium spp. These fungal pathogens make their entry into seed cavity through the small narrow passage at the blossom end. The seed cavity of the

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infected fruit is filled with fungal spores, seeds and the internal flesh is damaged. These fruit also show uneven ripening behaviour (Alvarez and Nishijima, 1987). Internal yellowing is a bacterial disease of ripe papaya fruit that is caused by the enteric bacterium Enterobacter cloacae. The fruit infected with E. cloacae can affect the coliform bacterial counts in the fresh-cut products. 6.7.1 Postharvest disease management Orchard sanitation is the most important consideration in reducing the pathogen inoculum from the field. The discarded and infected fruit should be removed immediately to control spread and survival of the pathogen. The preharvest application of fungicide sprays is an effective approach to reduce the incidence of postharvest diseases. The protective fungicides should be sprayed once every 7–14 days in rainy season when high disease pressure is expected, but the spray intervals can be increased to 14–30 days in dry conditions (Alvarez and Nishijima, 1987). Packinghouse hygiene and decontamination of packing line equipment is essential to prevent the build-up of inoculum and re-infection of the fruit subjected to disease control measures. There should be utmost care during harvest and postharvest handling to minimise the physical damage to fruit. The mechanical injuries caused during different packinghouse operations provide excellent opportunities for the entry of wound pathogens that causes serious fruit rot problems. The use of plastic liners for field bins, proper fruit arrangement and cushioning material in the box, and avoiding impact and compression damages during handling could be some of the ways to reduce the fruit rots problems caused by secondary pathogens (Paull et al., 1997). Postharvest temperature management is an important key to prevent the development of latent infections and also to suppress the growth and development of wound pathogens. The conditions favourable for slow ripening of fruit (15–18 °C) allow the latent fungus to grow appreciably. Therefore, rapid postharvest cooling of fruit to 13 °C before cold storage or transport and then faster ripening of fruit at 22.5 to 27.5 °C can be helpful to reduce the losses caused by diseases. Postharvest heat treatments have been used to meet quarantine requirements either to eliminate fruit fly eggs and larvae or to control diseases (Nishijima, 1995). Single hot water dip treatment (49 °C for 20 min) has been very promising to control postharvest diseases in papaya fruit without detrimental effect on fruit quality. The quarantine treatments aimed to control fruit fly such as forced air dry heat (FADH) and vapour heat (VH) also provide some control of postharvest diseases. Moreover, the single hot water dip before or after FADH and VH treatments can provide additional disease control to the same level as provided by the combination of fungicide thiabendazole with FADH and VH treatments (Nishijima et al., 1992). The double hot water dip treatment (42 °C for 30 min and then 49 °C for 20 min) that was used as a quarantine treatment in Hawaii from 1984 to 1992, also provided a good control of postharvest diseases, but the fruit quality was affected due to high levels of heat stress, which were close to the maximum that papaya fruit can tolerate.

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Though fungicide treatments are the most effective and least expensive method to control postharvest diseases in fruit (Nishijima, 1995), there are increasing concerns about the harmful effects of the fungicides on human and environmental health. As a result, the consumers demand residue-free fruit and the regulatory authorities have discontinued the use of several fungicides on fruits. Fungal pathogens have also developed resistance to synthetic fungicides due to their continuous use for several years. All these reasons have spurred investigations into alternative methods of disease control in papaya fruit. There is increasing interest in the exploitation of antibacterial and antifungal properties of essential oils, chitosan and other generally recognised as safe (GRAS) compounds to control postharvest diseases in fruits. A recent study has shown that incorporation of essential oils of thyme and Mexican lime with fruit coating material reduced the incidence of anthracnose and Rhizopus rot in ‘Maradol’ papayas (Bosquez-Molina et al., 2010). The fruit immersed in mesquite gum emulsion and formulated with both the essential oils, it was possible to reduce the disease incidence caused by C. gloeosporioides by 100% and Rhizopus rot by 60% with the thyme (0.1%) and Mexican lime (0.05%) essential oils. The postharvest treatment of papaya fruit with 1.5% chitosan before inoculation with C. gloeosporioides also provided adequate control of anthracnose during five days of shelf life at ambient conditions (Bautista-Baños et al., 2003). Gamagaea et al. (2003) reported that the postharvest application of sodium bicarbonate (2%) reduced the incidence and severity of anthracnose disease during 14 days storage at 13.5 °C and subsequent two days shelf life at 25 °C. The efficacy of sodium bicarbonate to control anthracnose increased when combined with a biocontrol agent, Candida oleophila (yeast; strain 1–182). The incorporation of sodium bicarbonate with a paraffin-wax and C. oleophila has been suggested to be the best combination to control anthracnose (Gamagaea et al., 2003, 2004). The survival of the biocontrol agent in 2% sodium bicarbonate-incorporated wax coating was not adversely affected (90%) during 14 days storage at 13.5 °C. Another study on testing the efficacy of antagonistic yeasts against the Colletotrichum gloeosporiodes showed that fruit treated with the Cryptococcus magnus at concentrations of 107 to 108 cells ml−1, as early as 24 h, preferably 48 h, before inoculation with the pathogen reduced the development of disease (de Capdeville et al., 2007). The research on the application of biocontrol agents and alternative disease control methods has gained momentum in the recent past and appears to be promising for commercial situations in the near future.

6.8

Postharvest insect pests and phytosanitary treatments

The international trade in papaya is constrained by the problem of regulated insect-pests. Fruit flies are the predominant insect-pests species of global concern. The major fruit flies species that infest papaya include Mediterranean fruit fly (Ceratitis capitata, Wiedemann), oriental fruit fly (Bactrocera dorsalis, Hendel), and melon fly (Bactrocera cucurbitae, Coquillett) (Seo et al., 1974, 1982; Armstrong et al., 1989). Fruit harvested after colour break stage are more prone

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to fruit fly infestation (Seo et al., 1982). The presence of the regulated insect-pests hampers the marketing of fruit not only between countries, but also between geographical areas within countries (e.g. Florida to California; Hawaii to the U.S. mainland; Queensland to Victoria, Australia; Okinawa to the Japan mainland) (Follett and Neven, 2006). Therefore, the strict phytosanitary procedures are followed to eliminate, sterilise, or kill the regulatory pests in exported papayas to prevent their introduction and establishment to new areas in countries such as the U.S.A. (mainland), Japan, Australia and New Zealand. Heat treatments and irradiation are legally approved and commercially used for papaya exports depending upon the destination country. 6.8.1 Heat treatments Heat treatments have been widely used and accepted measures of providing phytosanitary security against a number of insect-pests in tropical fruits (Paull and McDonald, 1994). The other benefits of postharvest heat treatments include disease control and modification of the ripening and storage behaviour of fruits (Paull and Chen, 2000 and references therein). All quarantine treatments including heat must provide probit 9 quarantine security (99.9968% mortality); this implies that no more than 32 individuals will survive from a treated population of 1 000 000 at the 95% confidence limit (Sharp, 1993). The application of heat can be achieved by different methods that include hot water immersion, dry hot air and vapour heat (VH) treatments. Akamine and Arisumi (1953) showed that single hot water dip (49 °C for 20 min) can control postharvest diseases in papaya fruit and it has been used by the papaya industry since then. This treatment was modified into double hot water immersion (Couey and Hayes, 1986) and was also accepted by the USDA–APHIS as a quarantine treatment in 1990. The first step involved hot water dip of one-quarter ripe fruit for 30 min at 42 °C followed by the second step of 20 min at 49 °C, and then immediate cooling of fruit to less than 30 °C with ambient water dips or sprays. There were several issues related to the effectiveness of this treatment against the larvae present in deep pulp (Hallman, 2000) and the quality of fruit (Paull and Chen, 1990). The one-quarter or less ripe fruit are expected not to be containing the third instar larvae of fruit flies. However, the blossom end defects allowed the fruit flies to oviposit in the papaya at an earlier stage than usual and for larger larvae than first instar to be found deeper in the pulp than usual (Zee et al., 1989), rendering the double dip hot water treatment ineffective to meet the quarantine requirements. The treated fruit also failed to ripen properly due to uneven or overheating with hard lumps in the mesocarp and poor skin colour (Paull and Chen, 1990). The double hot water dip treatment significantly altered the physiology of fruit ripening in papaya and the major processes affected by this treatment included skin colour development, respiration, ethylene production and its biosynthetic pathway, and flesh carotenoid biosynthesis (Chan, 1986; Paull and Chen, 1990). The sensitivity of fruit to heat is also determined by several other factors. For example, fruit harvested in winters showed more sensitivity to heat

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treatments. The fruit with lower calcium concentration in the mesocarp and exposed to a three day preharvest mean low temperature higher than 22.4 °C did not show heat sensitivity (Paull, 1995). The sensitivity of papaya fruit to heat decreased due to accumulation of heat shock proteins caused by a preconditioning treatment of 4 h at 42 °C or 1 h at temperatures >35 °C followed by 3 h at 22 °C (Paull and Chen, 1990). The research interest in hot water treatments for quarantine purposes has diminished due to their lack of approval by various quarantine regulatory authorities in the world. VH treatment involves heating fruit with warm air saturated with water vapours at temperatures between 40 and 50 °C to kill insect eggs and larvae. Seo et al. (1974) reported probit 9 security against oriental fruit fly (Bactrocera dorsalis) eggs and larvae in Hawaiian papayas using an average 11-hour approach time to raise the fruit temperatures from 23.3 to 44.4 °C, followed by maintaining the fruit temperatures at 44.4 °C for 8.75 hours. According to the current VH treatment protocol, the centre of fruit requires to reach 47.2 °C in >4 h, with 90–100% relative humidity in the last hour of the treatment, followed by the rapid cooling of fruit to <30 °C within an hour. The longer duration of VH treatment is disadvantageous from operational efficiency perspective. The VH treatment is an approved quarantine treatment for imports of Hawaiian papayas into the mainland U.S.A. and Japan (Armstrong and Mangan, 2007). Hot air treatment involves exposure of fruit to hot air in a closed system and is similar to VH treatment except the relative humidity is relatively lower to avoid water condensation on fruit. High temperature forced air (HTFA) treatment (43– 49 °C) provided phytosanitary security in Hawaiian-grown papayas against the eggs and larval stages of Mediterranean fruit fly, melon fly, and oriental fruit fly. The fruit that were exposed to forced hot air at 49 ± 0.5 °C with 40–60% relative humidity reached the 47.2 °C temperature at their centre in less than one hour (Armstrong et al., 1989). The HTFA is an approved quarantine treatment for papaya imports in the USA, Japan and New Zealand (Armstrong and Mangan, 2007). However, the papaya imports into New Zealand from the Pacific region (Fiji, Samoa, Tonga, and Cook Islands) require the fruit to be held at 47.2 °C for an additional 20 min. The HTFA is less detrimental to fruit quality compared to vapour heat and hot water immersion treatments. The exposure of papaya fruit to moist air (100% relative humidity) at 48.5 °C for 4 h produced more fruit damage compared to dry air (50% relative humidity) treatment for the same duration at the same temperature. Unlike double dip hot water treatment, there is no restriction on the ripeness of fruit to be exposed to the HTFA, but best results are obtained when the fruit are treated at colour break to 1/8-colour stage (Cavaletto, 1989, cited in Moy, 1993). 6.8.2 Irradiation Irradiation is an ideal technology for developing ‘generic’ quarantine treatments because it is effective against most insect and mite pests at dose levels that do not affect the quality of most commodities (Follett, 2009). According to Follett and

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Neven (2006), ‘a generic treatment is a single treatment that controls a broad group of pests without adversely affecting the quality of a wide range of commodities’. In 2006, low-dose generic radiation of 150 Gy for tephritid fruit flies and 400 Gy for all insects, except pupa and adult stages of Lepidoptera, was approved for the first time by the U.S. Department of Agriculture–Animal and Plant Health Inspection Service (USDA–APHIS, 2006). In 2009, the International Plant Protection Convention (IPPC) approved and annexed the generic dose of 150 Gy for all tephritid fruit flies to International Standards for Phytosanitary Measures No. 28, Phytosanitary treatments for regulated pests (IPPC 2007, cited in Follett, 2009). A practical advantage of generic treatments is that if a new fruit fly species or other quarantine pest should invade a new area, the fruit export trade using radiation as a disinfestation treatment would not be interrupted because the generic doses also would apply to the new invasive species (Follett, 2009). The ban on the postharvest use of chemical fumigants such as methyl bromide and the quality concerns from heat treatments increased the scope and prospects of irradiation as a phytosanitary treatment (Moy and Wong, 2002). Papayas irradiated with 400 Gy have been exported from Hawaii to the U.S.A. mainland since 2000 and this dose provided phytosanitary security against all tephritid fruit flies, white peach scale (Pseudaulacaspis pentagona, Targioni Tozzetti), and mealybug (Paracoccus marginatus, Williams & Granara de Willink) (Follett, 2009). Australia also exports papaya to New Zealand after radiation treatment at 250 Gy, a generic dose developed for their specific quarantine pests (Follett, 2009). A variation in the absorbed doses of radiation is often encountered under commercial situations. The doses are generally higher on the outside of the stack and lower in the centre of the stack. A recent study on dose mapping showed that dose variation (ratio of maximum to minimum values) was about 1.3 for papaya fruit packed alone and 1.37 for a mixture of papaya, longan and banana (Follett and Weinert, 2009). The treatment of papaya alone or in a mixed fruit box resulted in the absorption of the required minimum dose of 400 Gy. This study shows that there is a great scope of using generic irradiation treatments for single and mixed loads of fruits. Irradiation has shown to be superior to several thermal treatments as a phytosanitary measure for papayas and other tropical fruits in efficacy, product quality and economics (Moy, 1993). Many researchers have reported the beneficial response of papaya fruit to irradiation doses in the range of 250 to 1000 Gy (Balock et al., 1966; Akamine and Goo, 1971b; Akamine and Moy, 1983; Paull, 1996; Zhao et al., 1996; Camargo et al., 2007). These doses are sufficient to meet quarantine requirements without any adverse effect on fruit quality. The response of papaya fruit to irradiation depends upon several other factors such as fruit maturity, amount of dose absorbed, preharvest and postharvest conditions. Papaya can tolerate radiation dose up to 1000 Gy without any surface scald (Zhao et al., 1996). Sensory and nutritional quality of most of the tropical fruits including papayas is not affected by irradiation treatment (Moy, 1993; Moy and Wong, 2002). Harvest maturity is an important factor that governs the potential effects of irradiation treatment on the rate of fruit ripening, especially the fruit softening

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(Paull, 1996). Paull (1996) reported that irradiation (250 Gy) of 30% yellow fruit was effective in delaying skin yellowing, fruit softening and flesh colour development. However, the fruit irradiated at colour break stage (<10% yellow) with 250 Gy dose exhibited increased rates of respiration and ethylene production and faster skin yellowing compared to non-irradiated fruit. The radiation doses higher than 250 Gy (up to 1.5 kGy) have been tested on Hawaiian papayas. ‘Sunset’ papayas at 25 to 30% yellow stage, when irradiated with 0.5 to 1.0 kGy, had less pectic depolymerisation, and firmer texture at ripe stage than nonirradiated ones (Zhao et al., 1996). The firmness of these irradiated fruit was retained for two days longer than the non-irradiated control. However, the higher doses of irradiation (1.5 kGy) induced solubilisation of pectic substances and resulted in premature softening of fruit. In conclusion, the irradiation treatment with a dose of up to 1.0 kGy does not adversely affect the fruit quality in papayas treated at 25–30% skin colour stage. It is common to adopt a single postharvest phytosanitary treatment to prevent the introduction of exotic pests into the new regions. However, alternative approaches such as combination treatments, non-host status, identification of pest free areas, pest eradication, system approaches, and special inspection procedures can also provide the basis for establishing phytosanitary security (Follett and Neven, 2006).

6.9

Postharvest handling practices

6.9.1 Harvest operations Fruit maturity in papaya is mainly judged by the skin colour. The fruit at colour break stage are harvested by hand. The fruit pickers keep them in shoulder bags and then they are placed into plastic crates or field bins. There is a great need to educate fruit pickers to handle the fruit as gently as possible. Scars from pickers’ nails may become apparent injury when the fruit is ripe. The field bins and crates should preferably be lined with plastic liners and efforts should be made to minimise the bruising injury to the fruit. After harvesting, the fruit are transferred to the packinghouse for further operations. 6.9.2 Packinghouse practices The typical packinghouse operations followed in Hawaii are summarised in Fig. 6.2 (Paull et al., 1997). The fruit received in the packing shed are washed with a sanitising agent and sorted for colour, size, and defects. Culling involves the removal of fruit with defects such as mechanical injuries, deformities, scars, overripeness and size. After culling, the fruit are subjected to disinfestation treatment involving vapour heat. Vapour heat treatment involves increasing the fruit centre temperature to 47.5 °C over a period of 6–8 h, followed by cooling of fruit to < 30 °C with water (Paull et al., 1997). A very rapid cooling after heat treatment should be avoided to prevent the development of skin scald. After disinfestations

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Fig. 6.2 A flow diagram of the postharvest handling system of fresh papaya in Hawaii. The time scale on the left hand side is for the movement of fruit if there is no holding of fruit before the next step. [Adapted from Paull et al., 1997, with permission from Elsevier Ltd., UK].

treatment, the fruit are waxed and treated with fungicide before packing and sealing into 4.54 kg cartons. The bottom of cartons should be cushioned with foam mesh sleeves and foam padding; additionally, paper wrapping is important to prevent abrasion injury and development of ‘green islands’ on fruit. These cartons are then ready for air or surface shipment at 8–10 °C.

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According to CODEX standard for fresh papaya (Codex, 2001; amended 2005), fruit can be graded into three classes: Extra class, Class I, and Class II. Extra class fruit must be of superior quality and free from defects, with the exception of very slight superficial defects, provided these do not affect fruit appearance, quality, keeping quality and presentation in the package. Class I fruit must be of good quality, but with slight defects on the skin due to mechanical bruising and other superficial defects not exceeding 10% of the total surface area. Class II includes the fruit which do not qualify for the higher classes, but should meet minimum quality requirements including the total surface area with defects not to exceed 15%. There are ten size codes depending upon the fruit weight (in grams): A 200–300; B 301–400; C 401–500; D 501–600; E 601–700; F 701–800; G 801–1100; H 1101–1500; I 1501–2000; J >2001. 6.9.3 Control of ripening and senescence Papaya fruit ripening can be regulated by exposure to ethylene and 1-MCP, in addition to temperature management practices. A temperature of ~25 °C is considered ideal fruit ripening in papaya. The fruit harvested at colour break stage take about 10–16 days to reach full yellow stage at 22.5 to 27.5 °C (An and Paull, 1990). The ripening temperature of more than 27.5 °C increased weight loss and external abnormalities in fruit. Flesh softening and ripening progresses from inward to outward in papaya. The exogenous application of ethylene promoted skin yellowing, softening and flesh colour development in the outer mesocarp (Fabi et al., 2007), whereas the inner mesocarp near to seed cavity was not responsive to ethylene (An and Paull, 1990). ‘Red Lady’ fruit at colour break stage when treated with 100 ppm ethylene reached full yellow stage in three days at room temperature (26–32 °C, 46–65 % RH) while untreated fruit reached the same stage in seven days (see Plate XII in the colour section). Ethylene treatment is not recommended commercially because it limits the marketing period (Paull et al., 1997). However, it may be used to ensure uniform and rapid fruit ripening to regulate marketing at the retail level. 1-MCP has emerged as a wonderful postharvest tool to control ripening and senescence, and thus to enhance the storage/shipping potential of fruits. Many researchers have reported the beneficial effects of 1-MCP on the ripening and storage behviour of papaya fruit (Hofman et al., 2001; Karakurt and Huber, 2003; Ergun et al., 2006; Karakurt and Huber, 2007; Manenoi et al., 2007; Manenoi and Paull, 2007). 1-MCP treatment has been shown to suppress the rates of respiration and ethylene production in different cultivars of papaya such as ‘Sunrise Solo’, ‘Golden’, and ‘Rainbow’ (Ergun and Huber, 2004; Fabi et al., 2007; Manenoi et al., 2007). Manenoi et al. (2007) showed that treatment time of 4–24 hours had similar effect on the response of fruit to 1-MCP doses in the range of 50–1000 nL L−1. The development of skin and flesh colour and fruit softening was also delayed significantly by the 1-MCP treatment (100 nL L−1 for 12 h). However, the response of fruit to 1-MCP in papaya varied greatly due to fruit maturity. The fruit treated with 1-MCP at < 25% yellow stage failed to ripen properly, and developed a more

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elastic flesh texture, termed ‘rubbery’. Contrarily, the fruit at more ripe stage (40– 60% yellow) showed limited response to 1-MCP, in terms of number of days to reach edible ripe stage. Therefore, the beneficial effects of 1-MCP in papaya fruit can be obtained in a very narrow window of fruit maturity (25–30% yellow). Manenoi et al. (2007) reported that fruit treated with 1-MCP (100 nL L−1 for 12 h) at the colour break storage showed a delay in skin colour development of about seven days and at 25 and 50–70% yellow approximately five and one or two days, respectively. These treated fruit also showed a dramatic delay in softening and developed the ‘rubbery’ texture when fully ripe. The development of rubbery texture has been attributed to the lower enzyme activity of endoxylanase in the flesh tissue (Manenoi and Paull, 2007). The fruit with more than 25% yellow skin when treated with 1-MCP softened normally without any rubbery texture. Ethephon treatment before or after 1-MCP application was unable to overcome the effect of 1-MCP on fruit treated at colour break stage (Manenoi et al. 2007). The concentration of soluble solids and titratable acidity are not affected much by the 1-MCP treatment, but this treatment has also been shown to delay the disease development in papaya fruit. ‘Surya’ papayas treated with 1-MCP (100 nL L−1 for 18 h) at colour break stage could be stored for three weeks at 18 °C without any decay and flesh softening (Sudhakar Rao, unpublished data). Though the skin colour of the 1-MCP-treated fruit was completely yellow after storage, but failed to soften to reach edible-ripe stage. These studies clearly indicate that papaya should be treated with 1-MCP (100 nL L−1 for 12 h) when it attains > 25% skin colour. 6.9.4 Recommended storage and shipping Storage and shipping at low temperature (7–13 °C) and high relative humidity (90–95%) is recommended to maintain fruit quality in papaya (Paull et al., 2007). Long-term cold storage is limited by susceptibility of fruit to chilling injury. As mentioned previously, less mature (< 25% yellow) fruit are more susceptible to chilling injury at ≤ 10 °C, while more mature (25–75% yellow) fruit can tolerate the chilling conditions (7–10 °C) for about 2–3 weeks. The short-term (~24 h) exposure of fruit to severe chilling conditions such as 1–2 °C can be injurious to fruit. Temperature fluctuations during the surface or air-shipment of papayas can increase marketing losses due to more decay and poor fruit quality (Nunes et al., 2006). The application of MAP technology, in supplementation with optimum storage temperature, can also be very beneficial to reduce weight losses and retard fruit ripening during storage and long-distance shipping of papaya fruit.

6.10

Processing

6.10.1 Fresh-cut Demand for fresh-cut fruits (i.e. products have been subjected to various degrees of peeling, trimming, coring, slicing, shredding or dicing (Karakurt and

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Huber, 2003)) has increased several fold in the past decade. Production of freshcut products involves wounding the fruit tissue to a degree, which triggers several physiological and biochemical changes in the fruit that are generally associated with abiotic stresses. The most common symptoms are browning of cut surfaces, increased rates of respiration and ethylene production, loss of flavour, tissue softening, weight loss, and decline in phytonutrients (Hodges and Toivonen, 2008). The problems associated with fresh-cut products vary according to the fruit species, degree of maturity and handling and storage conditions. Fresh-cut papaya is a popular product. Two reasons for the rapid growth of the fresh-cut papaya industry may be that consumers consider the fresh-cut fruit more convenient than the whole fruit (which has to be peeled, deseeded and sliced before consumption) and find the large size of some papaya cultivars, such as ‘Maradol’ off-putting (Rivera-López et al., 2005). Fresh-cut papaya is not chilling sensitive and can be stored for about 8–10 days at 4–5 °C. A storage temperature of 5 °C has been suggested to be optimal (O’Connor-Shaw et al., 1994; Karakurt and Huber, 2003; Rivera-López et al., 2005; Ergun et al., 2006). An early report suggested that the potential shelf life of fresh-cut papaya was limited to two days at 4 °C, with tissue softening the limiting factor (O’Connor-Shaw et al., 1994). The susceptibility to tissue softening is mainly influenced by the degree of fruit maturity, post-cut treatments, packaging and storage conditions. Selecting fruit at optimum maturity is paramount for consumer acceptability of fresh-cut product. Paull and Chen (1997) reported that fruit with < 25% yellow skin had no soft edible flesh; an increase in skin yellowing to > 55% also increased the percentage of edible flesh to more than 60%. Fruit with < 55% skin yellowing showed more wound-induced respiration and ethylene production due to slicing and deseeding and fully ripe fruit were easily bruised and difficult to handle. Therefore, selecting fruit with 55–80% yellow skin, which ensures > 50% edible flesh recovery, has been recommended for production of fresh-cut papaya (Paull and Chen, 1997). Tissue softening in fresh-cut papaya is primarily due to changes in cell wall composition induced by the activities of various hydrolytic enzymes and stressrelated proteins. Wounding of 60–70% yellow fruit used to make fresh-cut product enhanced the activities of various enzymes such as polygalacturonase, α-galactosidase, β-galactosidase, lipoxygenase, phospholipase D, and ACC synthase and ACC oxidase within 24 h, and levels remained significantly higher compared with those in intact fruit during 8 days storage at 5 °C (Karakurt and Huber, 2003). The total amount of pectin in fresh-cut papaya also declined, increased in solubility and exhibited depolymerization. In addition, this study confirmed that tissue softening was due to the physiological and biochemical alterations in the cell wall and membranes rather than to microbial activity. Gene expression analysis of the fresh-cut papaya has also revealed that wounding induces the expression of proteins involved in membrane degradation, free radical generation, and enzymes involved in stress responses (Karakurt and Huber, 2007). It has been suggested that tissue softening in fresh-cut papaya can be delayed by treatment of 70–80% ripe fruit with 1-MCP (2.5 μL L−1 for 12 h) before slicing

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(Ergun et al., 2006). Softening in fresh-cut product from 1-MCP-treated fruit was significantly delayed during 6–10 days storage at 5 °C. The slices from 1-MCP treated fruit were acceptable to the sensory panel for six days while those from control fruit could only be stored for 2–3 days. The potential shelf life of fresh-cut ‘Maradol’ papaya has been suggested to be 2, 6 and 10 days at storage temperatures of 20, 10 and 5 °C, respectively. The degree of tissue softening and weight loss were also lower at 5 °C compared to 10 or 20 °C (Rivera-López et al., 2005). Storage of fresh-cut papaya at 5 °C also helped to prevent losses of soluble solids, ascorbic acid, β-carotene, and antioxidant capacity. This study also showed that slices were a better shape for fresh-cut products than cubes as the latter presented higher weight loss, lower SSC and lower overall quality. Another study on the comparison of cut shapes showed that papaya flesh cut into spheres (1.55 cm radius) showed lower weight loss, firmer texture, higher SSC and ascorbic acid and lower microbial count compared to the cubes (1.4 cm side) during 10 days storage at 4 °C (Argañosa et al., 2008). Furthermore, edible coatings have great potential to reduce problems of weight and textural losses in fresh-cut products, increasing their shelf life. The application of alginate- (2 % w/v) or gellan-based (0.5 % w/v) coating formulations containing 1% ascorbic acid on fresh-cut papaya reduced weight loss through improved water vapour resistance and delayed tissue softening during eight days storage at 4 °C (Tapia et al., 2008). González-Aguilar et al. (2009) reported that a medium molecular weight chitosan coating (0.02 g mL−1) maintained the quality of fresh-cut papaya in terms of higher colour values (L* and b*) and firmness. It showed antimicrobial activity and suppressed plate counts of mesophiles, moulds and yeasts during 14 days of storage at 5 °C. To summarize, the huge research interest in fresh-cut products has led to the development of techniques that involve minimum use of synthetic food additives which result in better retention of fruit quality. Both technological developments and consumer preferences indicate great scope for expansion of the fresh-cut papaya industry. 6.10.2 Other processed products Ripe papaya fruit can be processed into a number of other products such as pure juice, blended beverages, jam, jelly, dehydrated, fruit bars, candy, intermediate moisture and frozen products. Purée is the major intermediate product of papaya. It is further processed into products like juice, nectar, jam, jelly and leather. The slices and chunks of semi-ripe fruit can also be canned.

6.11

Conclusions

Papaya fruit is a rich source of vitamins, minerals and dietary antioxidants. The mature unripe and ripe fruit including seeds have been used in traditional medicine since ancient times. There is a great demand for papaya fruit in the fresh market and processing industry. A consistent supply of high quality fruit to the consumers

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and processors is a great challenge for papaya industry around the world. The tropical environmental conditions, where the papayas are grown, are congenial for the development of various diseases and insect-pests, and for promoting postharvest losses in fruit. The lack of cold chain, proper postharvest handling facilities, and limited market access due to phytosanitary requirements could be some of the reasons for the small share of major papaya producing countries in the world trade. Harvest maturity in papaya is a critical factor that determines fruit quality, shelf life, storage/shipping potential at low temperature, and susceptibility to mechanical injuries and diseases. Harvesting at colour break stage (10–12% yellow) is a commercial practice to ensure better postharvest life and long-distance shipping of fruit. The fruit harvested before optimum maturity fail to develop good eating quality. The delayed harvesting (>25% yellow) improves fruit quality, but limits shelf life and increases susceptibility to fruit-fly attack. The harvest maturity should therefore be determined by considering all these factors. Fruit harvested at colour break stage can be stored for 2–3 weeks at 7–13 °C temperature and 90–95% relative humidity. Fruit at advanced stages of ripeness are more tolerant to chilling conditions compared to less mature ones. The delicate nature of fruit skin predisposes it to mechanical injuries during harvest and postharvest handling operations, resulting in increased susceptibility of fruit to rots caused by wound pathogens. The marketability of fruit can be significantly increased by proper care to avoid the mechanical injuries and weight loss. MAP of papaya fruit with very low permeability films is beneficial to retard weight loss, fruit ripening and alleviate chilling injury during cold storage. The benefits associated with blocking of ethylene action by 1-MCP can be obtained only if the fruit are treated at >25% skin yellowing stage. The possibility of integration of 1-MCP into the current papaya handling protocol is limited because fruit treated at colour break stage fail to soften and produce ‘rubbery’ texture. However, the exposure of quarter- to half-ripe fruit to 1-MCP can delay the fruit softening and provide some benefits at the retail end. The phytosanitary treatments such as vapour heat, forced hot air and irradiation have been adopted commercially for fruit to be exported to countries such as the U.S.A. (mainland), Japan, Australia and New Zealand. The response of papaya fruit to these treatments varies greatly due to a number of factors including fruit maturity and growing conditions. The thermal treatments have been shown to cause some damage to fruit quality; while irradiation has been proven to be a safe technology without adverse effects on fruit quality. The postharvest diseases such as anthracnose, Rhizopus rot and stem-end rot are responsible for huge economic losses in fruit. The incidence and severity of these diseases can be reduced by integrated management practices such as orchard hygiene, preharvest and postharvest fungicide applications, packinghouse sanitation, heat treatments, and use of GRAS compounds alone or in combination with biocontrol agents. There is a great demand for fruit in the fresh-cut and processing industries. The fruit at 75% ripe stage are the most suitable for fresh-cut products, which can be safely handled at 5 °C for 5–10 days. The ‘tissue-softening’ is commonly a limiting

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factor in the stability of the fresh-cut papaya. This problem can be minimized by treatment of fruit with 1-MCP before cutting. The fruit can also be processed into a number of products such as puree, juice, jam, jelly, fruit bars, etc. The demand for healthy and nutritious fruits and their products is increasing as the consumers are adopting a healthy lifestyle. These trends present a positive outlook for the papaya industry in the near future.

6.12

References

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Hofman PJ, Jobin-Décor M, Meiburg GF, Macnish AJ and Joyce DC (2001), ‘Ripening and quality responses of avocado, custard apple, mango and papaya fruit to 1-methylcyclopropene’, Australian Journal of Experimental Agriculture, 41, 567–572. Ido PJ (1976), ‘The effect of leaf pruning on yield and quality of “Solo” papayas in Hawaii’, Proceedings of the American Society for Horticultural Science Tropical Region, 101, 45–50. Isabelle M, Lee BL, Lim MT, Koh WP, Huang D and Ong CN (2010), ‘Antioxidant activity and profiles of common fruits in Singapore’, Food Chemistry, 123, 77–84. Jones WW and Kubota H (1940), ‘Some chemical and respirational changes in the papaya fruit during ripening and the effects of cold storage on these changes’, Plant Physiology, 15, 711–717. Karakurt Y and Huber DJ (2003), ‘Activities of several membrane and cell-wall hydrolases, ethylene biosynthetic enzymes, and cell wall polyuronide degradation during lowtemperature storage of intact and fresh-cut papaya (Carica papaya) fruit’, Postharvest Biology and Technology, 28, 219–229. Karakurt Y and Huber DJ (2007), ‘Characterization of wound-regulated cDNAs and their expression in fresh-cut and intact papaya fruit during low-temperature storage’, Postharvest Biology and Technology, 44, 179–183. Katague DB and Kirch ER (1965), ‘Chromatographic analysis of the volatile components of papaya fruit’, Journal of Pharmaceutical Sciences, 54, 891–894. Krishna KL, Paridhavi M and Patel JA (2008), ‘Review on nutritional, medicinal and pharmacological properties of papaya (Carica papaya Linn.)’, Natural Product Radiance, 7, 364–373. Lam, PF (1990), ‘Respiration rate, ethylene production and skin colour change of papaya at different temperatures’, Acta Horticulturae, 257–266. Lazan H, Ng S, Goh L and Ali ZM (2004), ‘Papaya β-galactosidase/galactanase isoforms in differential cell wall hydrolysis and fruit softening during ripening’, Plant Physiology and Biochemistry, 42, 847–853. Lazan H, Selamat MK and ALi ZM (1995), ‘β-Galactosidase, polygalacturonase and pectinesterase in differential softening and cell wall modification during papaya fruit ripening’, Physiologia Plantarum, 95, 106–112. MacLeod AJ and Pieris NM (1983), ‘Volatile components of papaya (Carica papaya L.) with particular reference to glucosinolate products’, Journal of Agricultural and Food Chemistry, 31, 1006–1008. Maharaj R and Sankat CK (1990), ‘Storability of papayas under refrigerated and controlled atmosphere’, Acta Horticulturae, 269, 375–385. Manenoi A, Bayogan ERV, Thumdee S and Paull RE (2007), ‘Utility of 1-methylcyclopropene as a papaya postharvest treatment’, Postharvest Biology and Technology, 44, 55–62. Manenoi A and Paull RE (2007), ‘Papaya fruit softening, endoxylanase gene expression, protein and activity’, Physiologia Plantarum, 131, 470–480. Martinez ORZ (1988), ‘Estudio preliminar sobre el rendimiento de la papaya, Carica papaya L. var. “Sunrise Solo”. Mediate raleo de frutas’, Proceedings of the InterAmerican Society for Tropical Horticulture, 32, 74–78. Morton JF (1987), Fruits of Warm Climates, Winterville, U.S.A., Creative Resources, Inc., 336–346. Moy JH (1993), ‘Efficacy of irradiation vs thermal methods as quarantine treatments for tropical fruits’, Radiation Physics and Chemistry, 42, 269–272. Moy JH and Wong L (2002), ‘The efficacy and progress in using radiation as a quarantine treatment of tropical fruits: a case study in Hawaii’, Radiation Physics and Chemistry, 63, 397–401. Nakasone HY (1986), ‘Papaya’, in Monselise PS, CRC Handbook of Fruit Set and Development, Boca Raton, FL, CRC Press, Inc., 277–301. Nazeeb M and Broughton WJ (1978), ‘Storage conditions and ripening of papaya “Bentong” and “Taiping” ’, Scientia Horticulturae, 9, 265–277.

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Plate X

(Chapter 5) Trunk shaking harvester in high density hedgerow orchard.

(A)

(B)

Plate XI (Chapter 6) Effect of modified atmosphere packaging (MAP) on shelf life of ‘Red Lady’ papaya. Fruit were harvested at colour break stage, treated with fungicide (prochloraz; 100 ppm) and sealed in Cryovac® D-955 film. A. Storage for 12 days in MA plus 2 days in ambient air (2 weeks in total) at room temperature (RT; 26–32 °C, 32–45% RH) (D. V. Sudhakar Rao, unpublished). B. Storage for 21 days in MA plus 7 days in ambient air (4 weeks in total) at 18 °C, 72–80% RH (D. V. Sudhakar Rao, unpublished).

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(a) (b)

(c) (d)

Plate XII (Chapter 6) Effect of exogenous application of ethylene on fruit ripening in ‘Red Lady’ papaya harvested at colour break stage. Ethylene (a & b) and control (c & d) fruit after 3 and 7 days at room temperature (RT; 26–32 °C, 46–65% RH) (D. V. Sudhakar Rao, unpublished).

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7 Passion fruit (Passiflora edulis Sim.) W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain and G. Fischer, National University of Colombia, Colombia

Abstract: The species Passiflora edulis (sour passion fruit), is native from Brazil and is known in two forms, the purple and the yellow passion fruit. It is a climacteric fruit that quickly respires and produces a high amount of ethylene after harvest leading to a shorter shelf life for storage and transportation. The main quality issue is shrivelling due to water loss which affects consumer purchase decisions. Skin colour can be used as a maturity index for both the purple and the yellow form. For purple passion fruit storage at 4–5 °C is optimal whereas for yellow passion fruit a higher temperature of 10 °C is recommended. Both should be stored under high relative humidity to prevent water loss and shrivelling. Key words: Passiflora edulis, passion fruit, postharvest, processing, juice.

7.1

Introduction

7.1.1 Origin, botany, morphology and structure Sour passion fruit (Passiflora edulis Sim.) is a perennial vine of the Passifloraceae family (Rodriguez-Amaya, 2003). The Passifloraceae family consists of 18 genera one of which is the Passiflora genus with 530 species of which 50–60 are edible. The highest genetic diversity in Passifloraceae species is found in Colombia, where 167 species have been found, of which 165 were native, followed by Brazil (127 species) and Ecuador (90). This confirms the Andean area to be the birthplace of the genus (Ocampo Pérez et al., 2007). The species P. edulis (sour passion fruit) in particular however, is native from Brazil and is the species that dominates in the commercial orchards (Bernacci et al., 2008). Within this species, two distinct forms can be distinguished, the purple (often referred to as P. edulis f. edulis), and the yellow (mostly referred to as P. edulis f. flavicarpa Deg.). However, officially only P. edulis is accepted and P. edulis ‘Flavicarpa’ is considered a cultivar (Bernacci et al., 2008). Both have a similar round shape with

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a leathery skin containing aromatic juicy pulp with small seeds. However, besides the difference in colour they also differ in certain other properties as will be discussed later on. The purple passion fruit is mainly cultivated in Africa and Australasia and the yellow passion fruit in South America. General names for both in Spanish are granadilla, parcha, maracuyá (mainly used for the yellow), gulupa (mainly used for the purple); in Portuguese, maracuja peroba, maracujazeiro; in French, grenadille, or couzou, adding the colour to distinguish between the yellow and purple form. The vine is woody and perennial with shallow roots and climbs with the aid of tendrils. The vines can be supported by trellises (commercial plantations) or by wires in small domestic farms (Rodriguez-Amaya, 2003) or garden walls in gardens. It can grow very fast (4.5–6 m per year) but has a relatively short life (3 to 6 years) (Morton, 1987; Rodriguez-Amaya, 2003). The leaves are evergreen, alternate and deeply three-lobed when mature. They are 7.5–20 cm long, glossy green on the upper surface, paler and dull beneath. Leaves, young stems and tendrils, especially those of the yellow form are tinged with red or purple. The plant generally begins to bear fruit in one to three years, but in Colombia purple passion fruit already starts to produce after 9–10 months. A single, bisexual flower forms at the nodes of the new growth at the same spot as the tendrils. The flower is 5–7.5 cm across and surrounded by three large, leaf like bracts and has five greenish-white sepals and five white petals (Morton, 1987; RodriguezAmaya, 2003). At the apex of the androgynophore, each flower has a central prominent style which branches out into three stigma and situated below five stamens with large anthers, making self-pollination difficult (Rodriguez-Amaya, 2003). From the basis of the androgynophore, many slender straight rays, white at the tip and purple at the base, form a corona or ‘crown’, which is probably the most recognizable feature of the flower. The fruit are nearly round or ovoid, 35 (purple) to 80 (yellow) grams on average, 4–7.5 cm in diameter with a smooth, leathery rind ranging in hue from dark-purple with faint, fine white specks, to light-yellow or pumpkin colour (Morton, 1987). The rind is 3 mm thick, wrinkles when the fruit is ripe (more in the purple than the yellow form) and adheres to a 6 mm thick white pith (Morton, 1987; Rodriguez-Amaya, 2003). Numerous (up to 250) small, hard, edible, black (purple fruit) or dark brown (yellow fruit) seeds are embedded in double-walled, membranous sacs filled with yellow-orange, pulpy juice in a cavity (Morton, 1987). The pulp has an intense fragrance and has an appealing, musky, guava-like, sub-acid to acid flavour (Morton, 1987; Rodriguez-Amaya, 2003). The purple passion fruit is subtropical and will grow and produce best at elevations of 650–2000 m. However, in Colombia, the commercial production of purple passion fruit can be found between 1400 and 2200 m above sea level (Fischer et al., 2009) and in Kenya cultivation is found up to 2500 m (Ulmer and MacDougal, 2004). The yellow passion fruit is tropical and prefers lower elevations (0–1000 m) but commercial production can be found in Colombia between 0 and 1300 m above sea level (Fischer et al., 2009). With respect to the

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production at higher altitudes, the temperature and radiance seem to have an important effect on the timing of production. However, in orchard without irrigation, water deficits also play a role (Menzel and Simpson, 1994). A temperature between 21 and 32 °C is best for development of the plant with the optimum being 26.5 °C (Rodriguez-Amaya, 2003). Depending on the region the annual rainfall should be between 600 mm (Northern Transvaal with high relative humidity (RH)) and 2500 mm (India) (Morton, 1987) and this needs to be well distributed with heavy rainfall during flowering problematic for pollination; and irrigation recommended during the dry periods (Rodriguez-Amaya, 2003). They need protection from wind and frost, although they have been known to recover from frost damage after drastic pruning (Morton, 1987). The plant is not very demanding when it comes to soil type but prefers light to heavy sandy loams (Morley-Bunker, 1999) with sufficient organic matter, few salts, and a pH in the range of 5.0 to 7.5 (Morton, 1987). Good drainage is necessary to avoid water logging and collar rot (Nakasone and Paull, 1998) but enough water needs to be available during flowering and fruiting. Since the vines are shallow-rooted they need protection which can be provided with organic mulch. 7.1.2 Worldwide importance and economic value Production of passion fruit occurs in South America, Africa, India, many countries of South-east Asia (particularly Indonesia), and the South Pacific, including Hawaii, Australia and New Zealand (Morley-Bunker, 1999). Previously, the countries covering more than 80–90% of the world production were Hawaii, Fiji, Australia, Kenya, South Africa, Papua-New Guinea and New Zealand; however, in the last two decades the production centre has shifted back to the original habitat of the plant, the Latin-American continent. The main producers for purple passion fruit are now Brazil, Ecuador and Peru, and for the yellow form, Brazil, Ecuador, Peru, Venezuela, Costa Rica, Kenya, Zimbabwe, Thailand, Malaysia and Indonesia (Isaacs, 2009). The biggest passion fruit producer in the world is Brazil where the purple form is preferred for fresh consumption and the yellow for juicing in large-scale juice extraction plants. In 2007, 664 286 ton were produced on 47 032 ha (IBRAF, 2007), mainly yellow passion fruit. Ecuador has also consolidated itself as the main juice exporter (18 000 ton in 2008) in a market strongly influenced by the seasonality of the production resulting in problems of over production and scarcity (Isaacs, 2009). Another considerable problem is the variability of the price for fresh passion fruit. In good years (2004 and 2007), prices reach above $2.5 per kg for yellow passion fruit or even $4.5 (2005), but in contrast in lesser years (2000) prices drop to $1.4 per kg. The main clients for passion fruit in Europe are Germany, Belgium, Luxemburg and the Netherlands (Isaacs, 2009). In Australia, the purple passion fruit was flourishing up to 1943 when Fusarium caused massive wilting resulting in the adaptation of yellow passion fruit as a rootstock for the production of purple passion fruit. In New Zealand, similar

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problems arose but today, mostly in the Bay of Plenty region a profitable purple passion fruit industry exporting fruit and juice has developed. After recurring disease and pest problems on larger plantations, currently commercial culture of purple passion fruit can be found in Kenya on small and isolated plantings which can be better controlled. South Africa has successfully been producing purple passion fruit since the beginning of the century without serious problems. Purple passion fruit has been produced in India for many years, while the yellow form was only introduced a few decades ago. The latter was soon preferred for its more pronounced flavour and heavier and more regular crops (Morton, 1987). In Hawaii, a yellow passion fruit industry is firmly established and Fiji has a small juice-processing industry. 7.1.3 Cultivars and genetic variability Discussion has been ongoing as to whether the purple and yellow fruit were different forms, P. edulis forma edulis (purple) and P. edulis forma flavicarpa (yellow), but at taxonomic level, the use of the name P. edulis Sim. for either colour of sour passion fruit is indicated (Bernacci et al., 2008). There are a considerable amount of cultivars available but the specification of which cultivar is used is hardly ever given. A selection of available purple cultivars in Australasian and American markets include Australian Purple or Nelly Kelly, Black Beauty, Black Knight, Edgehill, Frederick, Kahuna, Paul Ecke, Purple Giant, Purple Possum, Red Rover. In the yellow range we find: Brazilian Golden, Golden Giant, Hawaiiana, McCain, Panama Gold, ‘Noel’s Special, Sweet Sunrise. The Brazilian cultivar BRS Ouro Vermelho produces both purple and yellow fruit. In Brazil a substantial amount of breeding work is being done to improve production and quality of the fruit. For the purple passion fruit attention has gone to Roxinho-Miúdo, Paulista and Maracujá-Maçã (Meletti et al., 2005). In the yellow range, IAC-273 and IAC-277 are gaining importance for fresh consumption with the main benefit in increased productivity with an average yield of 35–45 ton ha−1 whereas the average in Brazil so far is 10–15 ton ha−1. For the juice industry, IAC-275 was introduced, having a thin rind, a totally filled internal cavity, a higher soluble solids content (SSC), more vitamin C and a yield of more than 45 ton ha−1. This cultivar is now produced in six states of Brazil, as well as in Colombia and Venezuela (Pommer and Barbosa, 2009). 7.1.4 Culinary uses, nutritional value and health benefits The purple passion fruit is typically consumed fresh because it is sweeter, while the yellow passion fruit is used for processing due to its higher juice yield. Fresh passion fruit is eaten by cutting it in two and scooping out the pulp with a spoon. The pulp is also used in fruit salads, mousse, desserts, ice cream, and yoghurt or as a topping, with or without addition of sugar. After removing the seeds and homogenizing, it is also used to make jam and sauce which is then used in desserts as flavouring for cakes, and in icing. The juice is used pure or for preparation of

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cocktails and is used in the processing industry to make juice blends. Cooking the juice with sugar makes thick passion fruit-flavoured syrup. The juicy pulp has high contents of potassium and vitamins A, B6, C and E (see Table 7.1) and carotenoids (Pruthi, 1963). In yellow passion fruit, 13 carotenoids have been identified (Mercadante et al., 1998), with ζ-carotene (1.26–12.86 μg g−1 FW) and β-carotene (2.39–13.35 μg g−1 FW) the main carotenoids available (Silva and Mercadante, 2002). Additionally, in yellow passion fruit juice substantial levels of polyphenols (435 mg l−1) have been reported (Mercadante et al., 1998). The main anthocyanin found is pelargonidin 3-diglucoside (1.4 mg 100 g−1 FW) (Pruthi et al., 1961). The predominant volatile compounds in passion fruit pulp belonged to the classes of esters (59.24%, mainly hexyl butanoate and hexyl hexanoate), aldehydes (15.27%, mainly benzaldehyde), ketones (11.70%, mainly 3-pentanone) and

Table 7.1 Nutritional characteristics of purple and yellow passion fruit. Ranges are presented. Purple

Parameter

Weight (g) Diameter (cm) Length (cm) pH Soluble solids content (%Brix) TA (%) Moisture (%) Proteins (%) Fat (%) Glucose (%) Fructose (%) Sucrose (%) Citric acid (%) Malic acid (%) Fibre (%) Ash (%) Sodium (mg 100 g−1 FW) Potassium (mg 100 g−1 FW) Calcium (mg 100 g−1 FW) Magnesium (mg 100 g−1 FW) Iron (mg 100 g−1 FW) Vitamin B6 (mg 100 g−1 FW) Vitamin C (mg 100 g−1 FW) Vitamin E (mg α-tocopherol equivalent 100 g−1 FW)

Yellow

Min

Max

Min

Max

34.49 4.35 4.68 2.97 11.9 0.5 71.83 2.2 0.07 1.93 1.95 2.67 2.58 0.22 11.84 0.47 7.08 100 6.06 16 0.6 0.236 20.9 0.05

55.86 5.57 5.37 4.64 17 5.7 72.57 3.1 0.7 2.27 2.25 3.13 3.42 0.38 13.76 1.887 30 764 53 29 1.6

85 6 7 2.8 11 2.2 55 0.7 0.2

165 8.5 11 3.15 21.4 4.5 79

30 1.12

0.5 3.8 0.4 20

40 0.8

Sources: Arjona et al. (1992), Romero-Rodriguez et al. (1994), Shiomi et al. (1996b), Silva and Mercadante (2002), Nascimento et al. (2003), Rodriguez-Amaya (2003), Leterme et al. (2006), Fonseca and Ospina (2007) and Vasco et al. (2008).

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alcohols (6.56%, mainly benzyl alcohol and 1-hexanol), the other characteristic aroma compounds for passion fruit were limonene, β-ionone and linalool (Narain et al., 2004). Additionally, the difference in flavour and aroma between the purple and yellow passion fruit can be attributed to presence or absence of certain compounds (Rodriguez-Amaya, 2003). Various parts of this plant are biologically active and extracts have been used to treat anxiety, insomnia, asthma, bronchitis, urinary tract infection (Zibadi and Watson, 2004), as a mild sedative, in the treatment of bronchial asthma, nervous gastrointestinal disorders and menopausal problems. These effects have been partially proven, leaf extract have shown antioxidant (Ferreres et al., 2007), anxiolytic (Petry et al., 2001; Coleta et al., 2006) and anti-inflammatory activity (Benincá et al., 2007; Montanher et al., 2007). Peel extract of purple passion fruit reduce blood pressure (Ichimura et al., 2006; Zibadi et al., 2007) and improves wheezing, coughing, and shortness of breath in asthma patients (Watson et al., 2008). The fruit extract accelerates healing of abdominal wall and gastric sutures (Gomes et al., 2006; Silva et al., 2006), colonic anastomosis (Bezerra et al., 2006) and bladder wounds (Gonçalves Filho et al., 2006) in the rat model. Additionally, passiflin, a protein extracted from the seeds has antifungal properties and inhibits growth of breast cancer cells (Lam and Ng, 2009) and inducing apoptosis and decreasing cell viability of MOLT-4 leukaemia lymphoma (De Neira, 2003).

7.2

Preharvest factors affecting fruit quality

7.2.1 Flowering and pollination In tropical regions flowering and production are almost uninterrupted, with two main production periods of three months. In subtropical regions, only one 6–7 months production period occurs. Long days (>10–12 h of daylight) are required to induce flowering (Rodriguez-Amaya, 2003), with day lengths of 11 h or less inhibiting flowering under natural conditions in Hawaii (Nakasone and Paull, 1998). Additionally, a reduction in irradiance below full sun will negatively affect yield and even short periods of low irradiance have residual effects during periods of full sun. Furthermore, flowering is prevented under high temperatures and low irradiance indicating an interaction between temperature and irradiance. This is an important consideration when growing passion fruit in wet tropical environments with extended cloud cover (Menzel and Simpson, 1994). Although they are hermaphrodites (containing male and female organs), passion fruit flowers are self-sterile (self-fertilization cannot happen), and yellow passion fruit flowers are even self-incompatible (self-pollination cannot occur). The different forms open at different times in the day, the flowers of the purple passion fruit from dawn until midday, the yellow open at midday and close in the evening. Three types of flowers can be found on yellow passion fruit and they are very sensitive to rain during the pollination period, with rain within 1.5 h after pollination preventing pollen germination and pollen tube growth (Morton, 1987; Rodriguez-Amaya, 2003).

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Fruit set, numbers of seed, fruit weight, and juice yield depend on the amount of pollen deposited on the stigma (Akamine and Girolami, 1959); and without seed development, no juice will form (Knight and Winters, 1962). Passion fruit are usually pollinated by large bees (Xylocopa, Centris, Epicharis, Eulaema, Bombus, Ptiloglossa). Smaller bees like honeybees (Apis spp.) and stingless bees (Trigona sp.) are too small; they will visit the flowers but cannot transfer the pollen. Wooden logs are often placed in the orchards to ensure carpenter bee nesting. Hand pollination is also used to great extent and field workers can pollinate about 600 flowers per hour (Westerkamp and Gottsberger, 2000) with high success rates. Additionally, hand pollinated flowers are said to produce larger and juicier fruit (Rodriguez-Amaya, 2003). 7.2.2 Fruit growth, development and maturation Passion fruit have a single sigmoid growth curve with accelerated fruit growth during the first 20–21 days after anthesis (DAA) (Shiomi et al., 1996b; Hernández and Fischer, 2009). Pocasangre Enamorado et al. (1995) found that in yellow passion fruit, the maximum fruit size found at 21 DAA was due mainly to rind growth. For purple passion fruit, during this period there is also high respiration and ethylene production, followed by very low production up to 70 DAA (Shiomi et al., 1996b). The titratable acidity (TA) increases during the first 60 DAA for purple (Shiomi et al., 1996b) and 63–70 DAA for yellow (Pocasangre Enamorado et al., 1995; Vianna-Silva et al., 2005) and decreases thereafter. In general, SSC in the juice increases up to harvest; however, Pocasangre Enamorado et al. (1995) observed the highest accumulation of SSC 63 DAA. During this whole period the skin stays green up to 70 DAA after colour changes rapidly within the next 20–30 days (Shiomi et al., 1996b; Vianna-Silva et al., 2005). During the final stage of fruit maturation, vitamin C and carotene content will also increase. Purple (Arjona and Matta, 1991) and yellow (Vianna-Silva et al., 2005) passion fruit are mature around 70 DAA. 7.2.3 Maturity and harvest The skin colour of passion fruit can be used as a maturity index (Pruthi, 1963); seven maturity stages have been defined, related to the changes in colour of the skin from green to purple (see Plate XIII in the colour section between pages 238 and 239) for purple passion fruit (Pinzón et al., 2007) and from green to yellow (see Table 7.2) for yellow passion fruit (Vianna-Silva et al., 2008). Pinzón et al. (2007) recommend harvesting the purple passion fruit when the index reaches 3, which corresponds with 50% green and 50% purple (see Plate XIII in the colour section), approximately 70 days after flowering (Shiomi et al., 1996b). If harvested before this stage, fruit will not develop the full purple colour. Additionally, consumers prefer a purple colour at least 80–90% of the fruit surface and less than 75% is unacceptable for markets (Arjona and Matta, 1991).

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Maturity stages of yellow passion fruit

Maturity stage

Characterization

1 2 3 4 5 6 7

Peel totally green 4.7% of peel yellow 21.3% of peel yellow 28.5% of peel yellow 65.9% of peel yellow 82.4% of peel yellow 100% of peel yellow

Source: With permission from Vianna-Silva et al., 2008.

Fruit can be harvested when the skin is partially purple (approximately 70 days after flowering) as it will then continue to develop the full purple colour after harvest (Shiomi et al., 1996b). However, fruit will not develop the full purple colour if it is harvested at an immature stage (before 70 days after flowering). Additionally, consumers prefer a purple colour at least 80–90% of the fruit surface and less than 75% is unacceptable for markets (Arjona and Matta, 1991). The SSC/TA ratio is another parameter that can also be used as a maturity or ripening index. A higher SSC corresponds to more sweetness and a higher TA to more sourness (Harker et al., 2002). Shiomi et al. (1996a) and Pongjaruvat (2008) found that eating quality of purple passion fruit improved mainly due to a decrease in acidity. This is probably because in sensory tests, sourness has been shown to overshadow the sweetness sensation, and as sourness decreases with a decrease in TA during storage, sweetness is unmasked.

7.3

Postharvest physiology and quality

7.3.1 Respiration and ethylene production Passion fruit is a climacteric fruit with a high respiration rate of 400–1890 nmol kg−1s−1 for purple passion fruit at 20–25 °C (Shiomi et al., 1996b; Schotsmans et al., 2008). Ethylene production is also high and increases with ripening from 0.03 to 9.35 nmol kg−1s−1 (Shiomi et al., 1996b). The content of 1-aminocyclopropane-1carboxylic acid (ACC) and the activity of ACC synthase are low during the initial stage of ripening while the ACC oxidase activity is already high and they all increase during ripening, especially in juice sac and seed (Shiomi et al., 1996a; Mita et al., 1998). Expression of Pe-ACS1 and Pe-ACO1 are enhanced during ripening with increased expression of Pe-ACO1 starting first and expression much higher in arils than in seeds, resulting in a much higher level of ethylene being produced in arils than in seeds or peels during ripening (Mita et al., 1998). The level of expression of the ethylene receptors Pe-ETR1 and Pe-ERS1 did not significantly change over the course of ripening, but again much higher levels were found in arils than in seeds (Mita et al., 1998).

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7.3.2 Ripening, quality components and indices The most noticeable change is in skin colour. For purple passion fruit (see Plate XIII in the colour section) the colour gradually changes from green to purple (Pinzón et al., 2007) and for yellow passion fruit (see Table 7.2) from green to yellow (Vianna-Silva et al., 2008), which makes this characteristic perfect for use as a maturity index as discussed before. In purple passion fruit, at the same time as the colour change, the weight of the pulp increases, reaching a maximum around maturity stage 4 (85–95% coloured, 15–20% green) (Pinzón et al., 2007) while the total weight decreases (Kishore et al., 2006; Pongjaruvat, 2008). This is also related to the development of shrivelling, which is maximal at full ripeness (Schotsmans et al., 2008) and negatively affects consumer and market perception. The seemingly contradictory effect of increase in pulp with decrease in total weight is due to water loss which happens mainly from the peel (Pongjaruvat, 2008) evidenced in the decrease in thickness of the skin (Kishore et al., 2006; Pinzón et al., 2007). Firmness decreases fastest in the initial stage of ripening, slowing down thereafter (Kishore et al., 2006; Pinzón et al., 2007). The pH remains stable between stages 0 and 4 at 3.0 and then increases to 3.5. The SSC increases up to stage 3 whereas the TA decreases, resulting in an increase in SSC/TA ratio (Kishore et al., 2006; Pinzón et al., 2007; Pongjaruvat, 2008). Additional changes include loss of vitamin C (42.6–34.0 mg 100 g−1) increase in reducing and total sugars and changes in the pulp colour from light yellow to pink with a perceptible increase in flavour with ripening (Kishore et al., 2006). In yellow passion fruit, as the colour changes, the pH remains stable between stages 0 and 6 at 2.6 and then increases to 3.7. SSC increases from 13.43 (totally green) to 16.3 (totally yellow), the TA increases from 5.21% to 5.37% at stage 2 and then decreases to 4.64 at stage 7. This again results in an increase in SSC/TA ratio during maturation from 2.4–2.6 at stage 0 to 3.5 at stage 7 (Vianna-Silva et al., 2008).

7.4

Postharvest handling factors affecting quality

7.4.1 Handling and grading Fruit is harvested weekly or more frequently depending on the demand. Harvest is done by hand and preferably in the early hours of the day when the fruit is cooler and not subjected to sun and increase in temperature. Pressure is applied at the abscission zone near the calyx of the fruit or using scissors. Depending on market requirements, fruit are harvested with or without stem (Hernández and Fischer, 2009). For purple passion fruit, the colour changes can be used as a guide (Shiomi et al., 1996b). In other cases, fruit is gathered from the ground as it naturally drops when it ripens (Chavan and Kadam, 1995), however this is not advised as it increased the risk of bruising and infections. Passion fruit are harvested in small plastic baskets (of 2.5 kg) or cardboard boxes. Once harvested, diseased and damaged fruit (insect damage, physiological

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or physical disorders) are removed. Fruit is further graded according to size and marketed in boxes containing three to four layers of fruit separated by newspaper to prevent deterioration (Hernández and Fischer, 2009). 7.4.2 Temperature and relative humidity The optimal reported storage conditions for passion fruit vary between 5 °C and 10 °C and 85–90% RH. Temperature markedly affects the changes during storage, with a lower temperature decreasing the weight loss of the fruits (Arjona et al., 1992; Shiomi et al., 1996b; Schotsmans et al., 2008), the respiration rate (Pongjaruvat, 2008; Schotsmans et al., 2008) and the loss of SSC (Arjona et al., 1992). For purple passion fruit storage at 4–5 °C is reported to increase the commercial life of the fruit by 50% compared with fruit stored at room temperature (Hernández and Fischer, 2009). However, for yellow passion fruit a higher temperature of 10 °C is recommended since at this temperature shrivelling and weight loss is minimal compared with lower (5 °C) and higher (15 °C) temperatures (Arjona et al., 1992). Water loss and thus weight loss and shrivelling can be decreased even more by ensuring a high RH using packaging (Pongjaruvat, 2008) or film wrap (Arjona et al., 1994a). The lower water loss will also ensure turgor pressure in the cells remains high and improve the stiffness or compression firmness of the fruit (Pongjaruvat, 2008). High RH appears to negatively affect pulp yield, however, this is due to the fact that less water is being lost from the skin thus keeping the fruit weight the same (Arjona et al., 1994a; Pongjaruvat, 2008). High RH also prevents shrivelling and toughening of the peel (Pruthi, 1963; Arjona et al., 1994b; Schotsmans et al., 2008). Although increasing RH has many beneficial effects, care has to be taken when using high RH since it can also result in increased fungal growth (Pongjaruvat, 2008). 7.4.3 Packaging The beneficial effect of packaging is already clear at higher temperatures. Wrapping purple passion fruit in ‘Vinipel’ film wrap (PVC), at ambient temperature (18 °C) preserves quality for up to 10 to 12 days. Lowering the temperature (6 °C) prolonged this beneficial effect to 24 days (16 days in cold room + 8 days shelf life) (Pachón et al., 2006). Likewise, packaging purple passion fruit in perforated HDPE of 0.03 mm thickness increased shelf life to 24 days at 5 °C while better preserving quality (SSC, TA) and nutritional value (vitamin C) of the fruit (Singh et al., 2007). Wrapping yellow passion fruit in plasticized PVC film slows down shrivelling and weight loss during 30 days of storage at 10 °C (Arjona et al., 1994b), this could be attributed to the high RH of 85% of the modified atmosphere (13% O2 and 0.5% CO2) in the packaging. Pongjaruvat (2008) also found that packaging of purple passion fruit reduced weight loss and shrivelling, slowed down the changes in colour, pH, TA, sweetness, and sourness, maintained fruit firmness, and extended shelf life. However, again it was not clear if this was due to the altered gas composition (1–4 kPa O2 and 6 kPa CO2) or purely the increase in RH.

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Care must be taken when using modified atmosphere packaging since condensation and adverse atmosphere conditions can cause disorders like an increase in fungal growth and red bleeding. 7.4.4 Controlled atmosphere storage Pruthi (1963) noted that purple passion fruit could be kept in 5% O2 and 5% CO2 for six weeks. 7.4.5 Ethylene Purple passion fruit is sensitive to exogenous ethylene as it accelerates endogenous ethylene production (Shiomi et al., 1996a) and can thus accelerate ripening. This sensitivity is not clearly present at harvest since application of 1000 ppm ethylene for 24 h did not induce earlier onset of ethylene production when applied on harvest day, but was effective when applied one day or five days after harvest (Shiomi et al., 1996a). This has to be taken into account when using MAP packaging because it can result in accumulation of ethylene thus counteracting the beneficial effects on ripening delay. Ethylene can also be used to improve colour development of fruit harvested at the mature-green stage (Arjona and Matta, 1991). 7.4.6 Waxing The application of paraffin wax coating to purple passion fruit reduced weight loss and enhanced fruit appearance for five weeks (Pruthi, 1963). This is different from findings in purple passion fruit by Dagame et al. (1991) and Pongjaruvat (2008) where adding wax on the fruit surface did not improve storage life. Pachón et al. (2006) had the same experience in purple passion fruit but stated that even though the effects of the treatment are minimal, this would be a good general practice for fruit that does not have to be transported far if only for the effect on the external appearance for the fruit going to the local markets.

7.5

Crop losses

7.5.1 Chilling injury Below 6.5 °C fruit is affected by chilling injury resulting in red discolouration on the surface (Pruthi, 1963). This was also noted in trials by Pongjaruvat (2008) who recorded red bleeding but attributed this more to development of atmospheric conditions within MAP. 7.5.2 Pathological disorders One of the most important disorders in passion fruit is woodiness or ‘bullet’ with incidences of 71.8–73.1% in commercial orchards in Brazil (Novaes and

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Rezende, 2003), which is caused by the passion fruit woodiness virus (PWV) (Inch, 1978) or by the cucumber mosaic virus. Affected leaves are stunted, curled and discoloured, while the fruits are often under-sized, misshapen, hard and dry (Griesbach, 1992). The virus is easily transmitted by mechanical means and by aphids, especially Myzus persicae Sulz. and Aphis gossypii Glover (Chagas et al., 1981). In Australia, the disorder has been successfully controlled by introducing hybrid cultivars since these are tolerant of the common strains of woodiness virus (Taylor and Greber, 1973; Inch, 1978). After massive wilting in commercial plantations of purple passion fruit, grafting on wilt-resistance seedlings of the yellow passion fruit has proven to be the only satisfactory method to control soilborne diseases such as fusarium wilt (F. oxysporum f. passiflorae) (Inch, 1978; Nakasone and Paull, 1998). The often used harvest method to gather from the ground as the fruit naturally drops when it ripens (Chavan and Kadam, 1995) also results in fruit that is highly contaminated with soil-borne pathogens. Additionally, the use of polyethylene bags to ensure high RH does not reduce fungal attack (Pruthi, 1963). However, adding a 5% Lysol solution to the polyethylene bag successfully reduced fungal attack. The common fungal attacks are by Alternaria passiflorae with circular, sunken, and brown spots on the fruit surface, and septoria blotch caused by Septoria passiflorae (Rodriguez-Amaya, 2003). Pruthi (1963) noted that during long term storage at 6.5 °C, passion fruit was attacked by white (Fusarium oxysporum), blue (Penicillium expansum), and black (Aspergillus niger and Rhyzopus nigricans) fungus. Experiments with yellow passion fruit from conventional and organic orchards started at ambient temperature (25 °C) and high RH, revealed that all fruit contracted anthracnose, caused by Colletotrichum gloeosporioides and presenting as light-brown patches that increase in size and evolve into a soft rot. Fusarium rot affected 25.5% and 19% and Phomopsis rot 11% and 2% of conventional and organic fruit, respectively (Fischer et al., 2007). Phomopsis rot can be found as a stem end rot on the passion fruit. Cladosporium herbarum and Cladosporium oxysporum cause powdery spot and fruit scab in cooler moist areas, but so far no fungicidal measures have been found. Fytosanitary actions to prevent these diseases include foliar fungicide application with Mancozeb + cupper oxychloride or thiophanate methyl, and sporadically the insecticide Fenthion. In the search for biological control measures against anthracnose, Cymbopogon citratus essential oil has been evaluated for the control of postharvest decay in yellow passion fruit but it could not prevent anthracnose in yellow passion fruit (Anaruma et al., 2010). 7.5.3 Insect pests and their control Thrips (Trips spp.) can damage plants, mainly during dry weather. Damage by thrips while feeding leads to mottled punctures on the leaves and fruit which may shrivel and drop prematurely (Ondieki, 1975).

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Mites (Tetranychus urticae) cause brown coloured abrasions on the rind because they puncture the cells and drain their contents, especially close to the stalk (Mora and Benavides, 2009). Various types of flies can attack passion fruit. In Colombia, a complex of Dasiops sp. and Hexachaeta sp. cause severe damage. They cause flower and fruit abortion by consuming the content of the ovarian or the fruit itself. The affected fruit progressively wrinkle depending on the number of larvae present in the fruit and eventually drop. When cut open, the fruit is empty and shows initiation of fungal growth (Mora and Benavides, 2009). Suggested control measures include trapping, removal of pupae and larvae by destroying fallen flower buds and fruits. Passion fruit can also be a host to Mediterranean fruit fly so all quarantine measures related to this pest will apply when exporting to countries imposing quarantine measures for Mediterranean fruit fly. Additionally, since PWV is transmitted by aphids, especially Myzus persicae Sulz. and Aphis gossypii Glover (Chagas et al., 1981), it is important to control these. Care should be taken to apply only those insecticides and acaricides which are recommended for use on fruit crops and which will not interfere with the canning quality of the juice (Ondieki, 1975).

7.6

Processing

Passion fruit juice is the third most wanted exotic flavour after mango and pineapple and can be provided as juice at 14 °Brix or in concentrated form at 50 °Brix, which is more in demand (Isaacs, 2009). Fruit for processing is collected daily or weekly and transported to the processing plant, where rotten and unfit are removed. Then the fruit are washed with strong sprays of water to remove all dirt and leaves and other substances adhering to the fruit. The entire fruit is dropped between two rotating converging cones and when it bursts open, skins are carried through the cones whereas the pulp drops into a finisher (Hui et al., 2006). In another method, rotating, circular knives slice open the fruit and all is put in a continuous basket centrifuge, or the juice, pulp and seeds are forced through the holes in the wall and the rind stays behind. Afterwards, the seeds are removed from the pulp and juice by a screened pulper followed by a screened finisher leaving only clean juice (Hui et al., 2006). The main concern is the extreme heat sensitivity of the aroma and flavour components of the juice, making pasteurization difficult. Additionally, the high starch content of the juice can cause accumulation on the surfaces of the processing equipment, affecting efficiency (Hui et al., 2006). The juice can be consumed pure or diluted into a nectar or in mixes with other fruit juices. Additionally it can be concentrated to a juice of 43.5–50 °Brix but about 39% of the volatile components are lost in the process (Shaw et al., 2001). For yellow passion fruit, research has been directed to determine the ideal maturity stage for processing, and even though some changes may occur, fruit from stage 4 onwards (see Table 7.2) are suitable for processing (De Marchi et al., 2000).

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Another important consideration in passion fruit processing is the waste production, which constitutes almost 75% of the raw material. Of this, 90% is the peel which can be used for the production of pectin (Schieber et al., 2001), which is used as a gelling agent and stabilizer. Pectin can be extracted successfully from passion fruit peel with citric acid (Pinheiro et al., 2008). Oil from passion fruit seeds is high in linoleic and linolenic acid, making passion fruit seed a valuable non-conventional source for high-quality oil (Liu et al., 2008).

7.7

Conclusions

Passiflora edulis (sour passion fruit), native from Brazil, is known in two forms, the purple and the yellow passion fruit. Both behave similarly during flowering, fruit growth, maturation and ripening but they mainly differ in colour, SSC and TA level as well as their aroma components. They are both climacteric fruit with high respiration and ethylene production. The main quality changes during storage and ripening include decrease of acidity resulting in higher apparent sweetness and weight loss resulting in shrivelling. The latter is not appreciated by consumers who prefer a smooth fruit. Another important difference is the temperature requirement during storage. Where purple passion fruit is best stored at 4–5 °C, yellow passion fruit prefers a higher temperature of 10 °C. The main market for both forms is the processing industry and most of the export consists of juice.

7.8

References

Akamine E K and Girolami G (1959), ‘Pollination and fruit set in the yellow passion fruit’, Hawaii Agr Expt Sta Tech Bul, 59, 44. Anaruma N D, Schmidt F L, Duarte M C T, Figueira G M, Delarmelina C, et al. (2010), ‘Control of Colletotrichum gloeosporioides (Penz.) Sacc. in yellow passion fruit using Cymbopogon citratus essential oil’, Braz J Microbiol, 41, 66–73. Arjona H E and Matta F B (1991), ‘Postharvest quality of passion fruit as influenced by harvest time and ethylene treatment’, HortScience, 26, 1297–1298. Arjona H E, Matta F B and Garner J O (1992), ‘Temperature and storage time affect quality of yellow passion fruit’, HortScience, 27, 809–810. Arjona H E, Matta F B and Garner J O (1994a), ‘Wrapping in polyvinyl chloride film slows quality loss of yellow passion fruit’, HortScience, 29, 295–296. Arjona H E, Matta F B and Garner J O (1994b), ‘Wrapping in polyvinyl chloride film slows quality loss of yellow passion fruit’, HortScience, 29, 295–296. Benincá J P, Montanher A B, Zucolotto S M, Schenkel E P and Fröde T S (2007), ‘Evaluation of the anti-inflammatory efficacy of Passiflora edulis’, Food Chem, 104, 1097–1105. Bernacci L C, Soares-Scott M D, Junqueira N T V, Passos I R d S and Meletti L M M (2008), ‘Passifora edulis Sims.: The correct taxonomic way to cite the yellow passion fruit (and of others colors)’, Rev Bras Frut, 30, 566–576. Bezerra J A F, Campos A C L, De Vasconcelos P R L, Nicareta J R, Ribeiro E R, et al. (2006), ‘Extrato de Passiflora edulis na cicatrização de anastomose colônica em ratos: estudo morfológico e tensiométrico’, Acta Cirurg Bras, 21, 16–25.

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Chagas C M, Kitjima E W, Lin M T, Gama M I C S and Yamashiro T (1981), ‘Grave moléstia em maracujá amarelo (Passiflora edulis f. flavicarpa) no Estado da Bahia, causado por um isolado do vírus do “woodiness” do maracujá’, Fitopatol Bras, 6, 259–268. Chavan U D and Kadam S S (1995), ‘Passion fruit’, in Salunkhe D K and Kadam S S Handbook of Fruit Science and Technology: Production, composition, storage, and processing, New York, M. Dekker. Coleta M, Batista M T, Campos M G, Carvalho R, Cotrim M D, et al. (2006), ‘Neuropharmacological evaluation of the putative anxiolytic effects of Passiflora edulis Sims., its sub-fractions and flavonoid constituents’, Phytotherapy Res, 20, 1067–1073. Dagama F S N, Manica I, Kist H G K and Accorsi M R (1991), ‘Additives and polythene bags in the preservation of passion fruit stored under refrigeration’, Pesqu Agropecu Bras, 26, 305–310. De Marchi R, Monteiro M, Benato E A and Silva C A R d (2000), ‘Uso da cor da casca como indicador de qualidade do maracujá amarelo (Passiflora edulis Sims. f. flavicarpa Deg.) destinado à industrialização’, Ciencia e Tecnologia de Alimentos, 20, 381–387. De Neira C M (2003), ‘The effects of yellow passion fruit, Passiflora edulis flavicarpa, phytochemicals on cell cycle arrest and apoptosis of leukemia lymphoma molt-a cell line’, MSc Thesis. University of Florida. Ferreres F, Sousa C, Valentão P, Andrade P B, Seabra R M and Gil-Izquierdo à N (2007), ‘New C-deoxyhexosyl flavones and antioxidant properties of Passiflora edulis leaf extract’, J Agric Food Chem, 55, 10187–10193. Fischer G, Casierra-Posada F and Piedrahíta W (2009), ‘Ecofisiología de las especies pasifloráceas cultivadas en Colombia’, in Miranda D, Fischer G, Carranza C, Magnitskiy S, Casierra-Posada F, Piedrahíta W and Flórez L E, Cultivo, poscosecha y comercialización de las Pasifloráceas en Colombia: maracuyá, granadilla, gulupa y curuba, Bogotá, Sociedad Colombiana de Ciencias Hortícolas. Fischer I H, De Arruda M C, De Almeida A M, Garcia M, Jeronim E M, et al. (2007), ‘Doenças e características físicas e químicas pós-colheita em maracujá amarelo de cultivo convencional e orgânico no centro oeste paulista’, Rev Bras Frut, 29, 254–259. Fonseca D I and Ospina N M (2007), ‘Relacion semilla/fruto en dos pasifloras: granadilla (Passiflora liguralis Juss.) y gulupa (Passiflora edulis Sims.)’, Facultad de Agronomía. Bogotá, Universidad Nacional de Colombia. Gomes C S, Campos A C L, Torres O J M, Vasconcelos P R L d, Moreira A T R, et al. (2006), ‘Efeito do extrato de Passiflora edulis na cicatrização da parede abdominal de ratos: estudo morfológico e tensiométrico’, Acta Cirurg Bras, 21, 9–16. Gonçalves Filho A, Torres O J M, Campos A C L, Tâmbara Filho R, Rocha L C d A, et al. (2006), ‘Efeito do extrato de Passiflora edulis (maracujá) na cicatrização de bexiga em ratos: estudo morfológico’, Acta Cirurg Bras, 21, 3–8. Griesbach J (1992), ‘A guide to propagation and cultivation of fruit-trees in Kenya’, GTZ, Technical Cooperation, Eschborn, Germany. Harker F R, Marsh K B, Young H, Murray S H, Gunson F A and Walker S B (2002), ‘Sensory interpretation of instrumental measurements 2: Sweet and acid taste of apple fruit’, Postharvest Biol Technol, 24, 241–250. Hernández M S and Fischer G (2009), ‘Cosecha y poscosecha en las frutas pasifloráceas’, in Miranda D, Fischer G, Carranza C, Magnitskiy S, Casierra-Posada F, Piedrahíta W and Flórez L E, Cultivo, Poscosecha y comercialización de las Pasifloráceas en Colombia: maracuyá, granadilla, gulupa y curuba, Bogotá, Sociedad Colombiana de Ciencias Hortícolas. Hui Y H, Barta J, Cano M P, Gusek T W, Sidhu J S and Sinha N K (Eds.) (2006), Handbook of Fruits and Fruit Processing, Ames, Blackwell Publishing. IBRAF (2007), ‘Instituto Brasileiro de Frutas’, www.ibraf.org.br/estatisticas/ ProducaoBrasileiradeFrutas2007.pdf [accessed May 2011].

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Ichimura T, Yamanaka A, Ichiba T, Toyokawa T, Kamada Y, et al. (2006), ‘Antihypertensive effect of an extract of Passiflora edulis rind in spontaneously hypertensive rats’, Bioscience, Biotechnol Biochem, 70, 718–721. Inch A J (1978), ‘Passionfruit diseases’, Qld Agric J, 104, 479–484. Isaacs M (2009), ‘Mercados nacionales e internacionales de las frutas pasifloráceas’, in Miranda D, Fischer G, Carranza C, Magnitskiy S, Casierra-Posada F, Piedrahíta W and Flórez L E, Cultivo, poscosecha y comercialización de las Pasifloráceas en Colombia: maracuyá, granadilla, gulupa y curuba, Bogotá, Sociedad Colombiana de Ciencias Hortícolas. Kishore K, Bharali R, Pathak K A and Yadav D S (2006), ‘Studies on ripening changes in purple passion fruit (Passiflora edulis Sims.)’, J Food Sci Technol–Mysore, 43, 599–602. Knight R J J and Winters H F (1962), ‘Pollination and fruit set of yellow passionfruit in Sourthern Florida’, Fla State Hort Soc Proc, 75, 412–418. Lam S K and Ng T B (2009), ‘Passiflin, a novel dimeric antifungal protein from seeds of the passion fruit’, Phytomedicine, 16, 172–180. Leterme P, Buldgen A, Estrada F and Londoño A M (2006), ‘Mineral content of tropical fruits and unconventional foods of the Andes and the rain forest of Colombia’, Food Chem, 95, 644–652. Liu S, Yang F, Li J, Zhang C, Ji H and Hong P (2008), ‘Physical and chemical analysis of Passiflora seeds and seed oil from China’, Int J Food Sci Nutr, 59, 706–715. Meletti L M M, Soares-Scott M D and Bernacci L C (2005), ‘Caracterização fenotípica de três seleções de maracujazeiro-roxo (Passiflora edulis Sims.)’, Rev Bras Frut, 27, 268– 272. Menzel C M and Simpson D R (1994), ‘Passion fruit’, in Schaffer B and Andersen P C Handbook of Environmental Physiology of Fruit Crops: Sub-tropical and tropical crops, Boca Raton, FL, CRC Press. Mercadante A Z, Britton G and Rodriguez-Amaya D B (1998), ‘Carotenoids from yellow passion fruit (Passiflora edulis)’, J Agric Food Chem, 46, 4102–4106. Mita S, Kawamura S, Yamawaki K, Nakamura K and Hyodo H (1998), ‘Differential expression of genes involved in the biosynthesis and perception of ethylene during ripening of passion fruit (Passiflora edulis Sims.)’, Plant Cell Physiol, 39, 1209–1217. Montanher A B, Zucolotto S M, Schenkel E P and Fröde T S (2007), ‘Evidence of anti– inflammatory effects of Passiflora edulis in an inflammation model’, J Ethnopharmacol, 109, 281–288. Mora H and Benavides M (2009), ‘Plagas de importancia económica asociados a las pasifloráceas y su manejo en Colombia’, in Miranda D, Fischer G, Carranza C, Magnitskiy S, Casierra-Posada F, Piedrahíta W and Flórez L E, Cultivo, poscosecha y comercialización de las Pasifloráceas en Colombia: maracuyá, granadilla, gulupa y curuba, Bogotá, Sociedad Colombiana de Ciencias Hortícolas. Morley-Bunker M (1999), ‘Passionfruit’, in Jackson D I and Looney N E, Temperate and Subtropical Fruit Production, Wallingford, Cabi Publishing. Morton J (1987), ‘Passionfruit’, Fruits of Warm Climates, Winterville, Creative Resource Systems Inc. Nakasone H Y and Paull R E (1998), Tropical Fruits, Wallingford, CAB International. Narain N, Almeida J d N, Galvao M d S, Madruga M S and Brito E S d (2004), ‘Compostos voláteis dos frutos de maracujá (Passiflora edulis forma Flavicarpa) e de cajá (Spondias mombin L.) obtidos pela técnica de headspace dinâmico’, Ciencia e Tecnologia de Alimentos, 24, 212–216. Nascimento W M O d, Tomé A T, Oliveira M d S P d, Müler C H and Carvalho J E U d (2003), ‘Seleção de progênies de maracujazeiro-amarelo (Passiflora edulis f. flavicarpa) quanto à qualidade de frutos’, Rev Bras Frut, 25, 186–188. Novaes Q S d and Rezende J A M (2003), ‘Selected mild strains of Passion fruit woodiness virus (PWV) fail to protect pre-immunized vines in Brazil’, Sci Agric, 60, 699–708.

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Ocampo Pérez J A, Coppens d’Eeckenbrugge G, Restrepo M, Jarvis A, Salazar M and Caetano C (2007), ‘Diversity of Colombian Passifloraceae: biogeography and an updated list for conservation’, Biota Colomb, 8, 1–45. Ondieki J J (1975), ‘Diseases and pests of passion fruit in Kenya’, Acta Hortic, 19, 291–293. Pachón A, Montaño A and Fischer G (2006), ‘Efecto del empaque, encerado y temperatura sobre las características fisicoquímicas y organolépticas de la gulupa (Passiflora edulis f. edulis) en postcosecha’, in Salamanca G Propiedades fisicoquímicas y sistemas de procesado: productos hortofrutícolas en el desarrollo agroalimentario, Bogotá, Ed. Guadalupe. Petry R D, Reginatto F, de-Paris F, Gosmann G, Salgueiro J B, et al. (2001), ‘Comparative pharmacological study of hydroethanol extracts of Passiflora alata and Passiflora edulis leaves’, Phytotherapy Res, 15, 162–164. Pinheiro E s R, Silva I M D A, Gonzaga L V, Amante E R, Teófilo R F, et al. (2008), ‘Optimization of extraction of high-ester pectin from passion fruit peel (Passiflora edulis flavicarpa) with citric acid by using response surface methodology’, Bioresour Technol, 99, 5561–5566. Pinzón I M d P, Fischer G and Corredor G (2007), ‘Determinación de los estados de madurez del fruto de la gulupa (Passiflora edulis Sims.)’, Agron Colomb, 25, 83–95. Pocasangre Enamorado H E, Finger F L and Puschmann R (1995), ‘Development and ripening of yellow passion fruit’, J Hortic Sci, 70, 573–576. Pommer C V and Barbosa W (2009), ‘The impact of breeding on fruit production in warm climates of Brazil’, Rev Bras Frut, 31, 612–634. Pongjaruvat W (2008), ‘Effect of modified atmosphere on storage life of purple passion fruit and red tamarillo’. MSc Thesis. Massey University, Palmerston North. Pruthi J S (1963), ‘Physiology, chemistry, and technology of passion fruit’, Adv Food Res, 12, 203–282. Pruthi J S, Susheela R and Girdhari L A L (1961), ‘Anthocyanin pigment in passion fruit rind’, J Food Sci, 26, 385–388. Rodriguez-Amaya D B (2003), ‘Passion fruits’, in Caballero B, Encyclopedia of Food Sciences and Nutrition, Oxford, Academic Press. Romero-Rodriguez M A, Vazquez-Oderiz M L, Lopez-Hernandez J and Simal-Lozano J (1994), ‘Composition of babaco, feijoa, passion-fruit and tamarillo produced in Galicia (NW Spain)’, Food Chem, 49, 251–255. Schieber A, Stintzing F C and Carle R (2001), ‘By-products of plant food processing as a source of functional compounds–recent developments’, Trends Food Sci Technol, 12, 401–413. Schotsmans W C, Nicholson S E, Pinnamaneni S and Mawson A J (2008), ‘Quality changes of purple passion fruit (Passiflora edulis Sims.) during storage’, Acta Hortic, 773, 239–244. Shaw P E, Lebrun M, Dornier M, Ducamp M N, Courel M and Reynes M (2001), ‘Evaluation of concentrated orange and passionfruit juices prepared by osmotic evaporation’, LWT-Food Sci Technol, 34, 60–65. Shiomi S, Kubo Y, Wamocho L S, Koaze H, Nakamura R and Inaba A (1996a), ‘Postharvest ripening and ethylene biosynthesis in purple passion fruit’, Postharvest Biol Technol, 8, 199–207. Shiomi S, Wamocho L S and Agong S G (1996b), ‘Ripening characteristics of purple passion fruit on and off the vine’, Postharvest Biol Technol, 7, 161–170. Silva J R, Campos A C, Ferreira L M, Aranha Jr. A A, Thiede A, et al. (2006), ‘Efeito do extrato da Passiflora edulis na cicatrização de gastrorrafias em ratos: estudo morfológico e tensiométrico’, Acta Cirurg Bras, 21, 52–60. Silva S R d and Mercadante A Z (2002), ‘Composição de carotenóides de maracujá– amarelo (Passiflora edulis flavicarpa) in natura’, Ciencia e Tecnologia de Alimentos, 22, 254–258.

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Singh A, Yadav D S, Patel R K and Mousumi B (2007), ‘Effect on shelf-life and quality of passion fruit with polyethylene packaging under specific temperature’, J Food Sci Technol–Mysore, 44, 201–204. Taylor R H and Greber R S (1973), ‘Passion fruit woodiness virus.’, CMI/AAB, Description of Plant Viruses, 122. Ulmer T and MacDougal J M (Eds.) (2004), Passiflora: Passionflowers of the World, Cambridge, Timber Press, Inc. Vasco C, Ruales J and Kamal-Eldin A (2008), ‘Total phenolic compounds and antioxidant capacities of major fruits from Ecuador’, Food Chem, 111, 816–823. Vianna-Silva T, Resende E D d, Viana A P, Pereira S M d F, Carlos L d A and Vitorazi L (2008), ‘Qualidade do suco de maracujá-amarelo em diferentes épocas de colheita’, Rev Bras Frut, 28, 545–550. Vianna-Silva T, Resende E D d, Viana A P, Rosa R C C, Pereira S M d F et al. (2005), ‘Influência dos estádios de maturação na qualidade do suco do maracujá-amarelo’, Rev Bras Frut, 27, 472–475. Watson R R, Zibadi S, Rafatpanah H, Jabbari F, Ghasemi R, et al. (2008), ‘Oral administration of the purple passion fruit peel extract reduces wheeze and cough and improves shortness of breath in adults with asthma.’, Nutr Res, 28, 166–171. Westerkamp C and Gottsberger G (2000), ‘Diversity pays in crop pollination’, Crop Sci, 40, 1209–1222. Zibadi S, Farid R, Moriguchi S, Lu Y, Foo L Y, et al. (2007), ‘Oral administration of purple passion fruit peel extract attenuates blood pressure in female spontaneously hypertensive rats and humans’, Nutr Res, 27, 408–416. Zibadi S and Watson R R (2004), ‘Passion fruit (Passiflora edulis): Composition, efficacy and safety’, Evidence-Based Integrative Medicine, 1, 183–187.

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Plate XIII

(Chapter 7) Maturity index/colour scale for purple passion fruit with six maturity stages from totally red (0) to over mature (6) (with permission from Pinzón et al., 2007).

8 Pecan (Carya illinoiensis (Wangenh.) K. Koch.) A. A. Gardea and M. A. Martínez-Téllez, Research Center for Food and Development, Mexico and E. M. Yahia, Autonomous University of Queretaro, Mexico

Abstract: A native species of North America, pecans are grown in several countries around the world. The nuts are well known for their important benefits for consumers’ health, including properties to prevent heart disease. Pecan quality attributes are well defined and set the standards not only for marketing issues, but also for breeding programs as well. Because of their low respiration rates, pecans are suitable for long-term storage, providing that conditions to prevent oxidation reactions are minimized. Both kernel darkening and rancidity development are oxidative reactions, which can be prevented by proper cold storage and limited exposure to air; however cold storage by itself reduces the reaction rate significantly. This chapter describes the guidelines for the management of pecans from harvesting to storage. Key words: Carya illinoiensis, pecan, postharvest, nutrition, processing.

8.1

Introduction

Public perception about the importance of selecting appropriate foods to support healthy lifestyles dictates particular attention not only to nutritional contents, but also to all of the nutraceutical properties found in foods. The nuts of the pecan tree are particularly rich in compounds that offer such positive impacts in our body (Yahia, 2010). It is recommended that regular intake of these nuts has protective effects against several maladies related to our modern sedentary life. Endemic to North America, pecans have been the staple of natives for centuries. Today, they are also grown in many countries, and although most of the crop is still produced in its original region, their marketing is expanding. Oleic and linoleic fatty acids are the main constituents of pecan oils and their content of unsaturated lipids is ten times higher than their saturated fats, not to mention a

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wide series of other protective mechanisms related to their nutrients, micronutrients, vitamins, tocopherols, and diverse phytochemicals (Yahia, 2010). Pecan nuts, like all nuts, have very low respiration rates and quality deterioration. This chapter describes general guidelines for proper management of pecans from the moment they are harvested, through their postharvest handling and storage. 8.1.1 Origen and distribution Although native to North America, at present pecans are widely distributed in Australia, Brazil, China, Israel, Peru and South Africa; the largest acreage being found in the USA, followed by Mexico. Commercial pecan growing started in the United States, where the oldest groves are found, although Australian orchards have been under cultivation for the last forty years (Wakeling et al., 2000). The Spaniards were the first Europeans to find pecans in northern Mexico in the sixteenth century and legend has it that the birth rate of local natives was closely associated with the biannual bearing cycle characteristic of this species, implying its important role as a staple food. Pecans are a conspicuous element of the gallery forests (Beard, 1955; Sparks, 2005), typical of the semiarid regions of both Southern USA and Northern Mexico, as well as the deciduous forests of the USA east of the Mississippi. Not surprisingly, the largest diversity in native pecans is found in the USA, a situation that was considered when the United States Department of Agriculture (USDA) established a breeding and selection program that has yielded results for the last seventy years. Many of the commercially important varieties were originated from such a program, and continue to provide the industry with improved germplasm (Thompson and Grauke, 2003). So far, breeding programs in the United States continue to lead the search for improved germplasm (Sparks, 1992), and a review of the initial parameters is in continuous demand by the industry (Heaton et al., 1975). Taxonomically classified in the Junglandaceae family, pecans (Carya illinoinensis (Wangenh.) K. Koch) (USDA, 2010b) are an American species related to English walnuts (Juglans regia L.), actually a Caucasian species, and other American species such as Arizona, Southern California and Northern California walnuts and black walnut (Juglans nigra L.), whose high quality wood and veneers are highly demanded. Also, 21 other hickory species are included in this family (USDA, 2010a). 8.1.2 Production and consumption Pecan consumption in its countries of origin, the USA and Mexico, is higher than elsewhere. In the United States, almonds (Prunus amygdalus Batsh) and English walnuts (Juglans regia L.) are the nuts recording the highest consumption, followed by pecans. Pecan consumption in the United States, with a ten year average production of 114.4 M kg (Hadjigeorgalis et al., 2005), is 218 to 375 g per capita (Geisler, 2010). In Mexico, official numbers report an annual consumption of 250 g per person (Milenio, 2008), however, the inclusion of temporal inventories (like temporal imports for shelling), may be artificially increasing an otherwise more realistic figure. The United States accounts for the

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largest export and import of pecans; its top buyer being Hong Kong, while most of in-shell and shelled pecan imports are from Mexico (Geisler, 2010). Nonetheless, pecan consumption is expected to grow given an increase in plantings and an expanding market. The increase in consumption will depend on several factors, the most important of them being the extent of increasing trends in consumption of healthy foods.

8.2

Nutritional value of pecan nuts

Tree nuts are considered rich sources of different phytochemicals that may contribute to health benefits because of their antioxidant, anti-proliferative, antiinflammatory, anti-viral and hypocholesterolemic properties (Bolling et al., 2010; Yahia, 2010). Such compounds include carotenoids, hydrolysable tannins, lignans, naphtoquinones, phenolic acids, phytosterols, polyphenols and tocopherols (Bolling et al., 2010). Pecan meat is an excellent source of many nutrients and phytochemicals (Table 8.1). By contrasting those figures it is clear that, as compared with almonds and English walnuts, pecans are richer in calories, linoleic acid, some micronutrients (zinc, copper and manganese) and some vitamins (particularly vitamins A and K), as well as γ-tocopherol (Self Nutrition Data, 2010). Kernel protein content accounts for 9 g per 100 g−1 of meat, although it is considered as genotype related. Wakeling et al. (2001) found that protein content was the only significant difference between Western Schley and Wichita pecans grown in Australia as compared to higher contents found when grown in the United States. Therefore, the information below must be viewed as a reference rather than universal values, and differences due to genotype, environment and their interaction should be taken in account. Pecans are rich in mono and polyunsaturated fatty acids. According to Rudolph et al. (1992) the most abundant fatty acids in pecan kernels are: oleic>linoleic> palmitic>stearic> linolenic, although their concentration may vary with genotype, maturity and year crop (McMeans and Malstrom, 1982). Other works report up to ten different fatty acids (Senter and Hdrvat, 1976). Oleic and linoleic acids comprise from 90% (Villarreal-Lozoya et al., 2007) to 95% (Herrera, 2005) of total kernel oil content, the high oleic acid content being the source for biosynthesis of linoleic and linolenic acids, as occurs in oilseeds (Toro-Vazquez et al., 1999). It is during embryo and cotyledon expansion when fatty acids accumulate in kernels (Wood and McMeans, 1982). Another benefit for consumers’ health is that pecan oil has ten times more unsaturated than saturated fatty acids (Yao et al., 1992), besides up to 22 g and 1 g per serving of total omega-6 and total omega-3 fatty acids, respectively (Self Nutrition Data, 2010). It has been reported that consumption of pecans lowers the risk of heart disease (Yahia, 2010). Mukuddem-Petersen et al. (2005) concluded that consumption of 50 to 100 g d−1 of nuts, at least five times a week, as part of a heart-healthy diet with a total fat content of 35% of energy, significantly decreased total cholesterol and LDL-cholesterol in normo- and hyperlipidemic individuals.

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Table 8.1 Nutrients and health improving compounds present in the three most consumed nuts in the USA Nutrients in 100 grams of meat

Calories, kcal Protein, g Total fat, g Saturated fat, g Monounsaturated fat, g Polyunsaturated fat, g Linoleic acid (18:2), g Linolenic acid (18:3), g Carbohydrates, g Fiber, g Calcium, mg Iron, mg Magnesium, mg Phosphorus, mg Potassium, mg Sodium, mg Zinc, mg Copper, mg Manganese, mg Selenium, μg Vitamin C, mg Thiamin, mg Riboflavin, mg Niacin, mg Pantothenic acid, mg Vitamin B6, mg Folate, μg Vitamin A, intl. units Vitamin K, μg Vitamin E Tocopherol, α, mg Tocopherol, β, mg Tocopherol, γ, mg Tocopherol, δ, mg

Phytochemicals in 100 grams of meat

Wal

Alm

Pec

650 15 65 6

580 21 51 4

690 9 72 6

9

32

41

47

12

22

38

12

21

9

0

1

14 7 98 2.91 158 346 441 2 3.09 1.59 3.41

20 12 248 4.30 275 474 728 1 3.36 1.11 2.53

14 10 70 2.53 121 277 410 0 4.53 1.20 4.50

4.90 1.30 0.34 0.15 1.12 0.57

2.80 0 0.24 0.81 3.92 0.35

3.80 1.10 0.66 0.13 1.17 0.86

0.54 98 20 2.70 0.70 0.15 20.8 1.89

Wal Carotenoids Carotene β, μg Lutein, μg Lutein + zeaxanthin, μg Cryptoxanthin, β

0

3 8.47 1

29 17.6 17

0

9

Total phytosterols, mg 72

120

97

Stigmasterol, mg Campestrol β-sitosterol

4 5 111

3 5 89

Phytosterols

Flavonoids Catechin, mg Cyanidin, mg Delphinidin, mg Epicatechin, mg Epigallocatechin, mg Epigallocatechin gallate, mg Proanthocyanidins Monomers, mg Dimers, mg Trimers, mg 4–6mers, mg

0.13 0.21 7–10mers, mg 29 22 Polymers, mg 5 56 0

12 7.1 9

Alm Pec

1 7 64 0 2.47 0 0 0 0

7.34 6.0 7.62 23.3

2.47 0 0 0.35 2.12 0.70

6.70 9.88 6.70 0.70 5.29 2.12

8.22 18.23 10.1 44.6 9.35 27.6 42.3 107.3

5.71 39.9 21.2 84.9

89.1 235.9

3.50

25.9 1.40 0.43 0.39 0.89 24.4 0.25 0.47

Sources: Nutrients. USDA National Nutrient Database for Standard Reference, Release 16, last update 2005. International Tree Nut Council Nutrition Research and Education Foundation, September, 2003. Phytochemicals. USDA Phytochemical Study (2004), USDA Nutrient Database Standard Reference, Release 17, 2006. USDA database for the Proanthocyanidin Content of Selected Foods (2004), www.nal.usda.gov/fnic/foodcomp. All data were normalized from original units to 100 g of meat. Wal: walnuts, Alm: almonds, Pec: pecans

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A close look at the data in Table 8.1 also shows that pecans represent the highest source of antioxidants of these three species, confirming earlier findings by Villarreal-Lozoya et al. (2007), who demonstrated that phenolic compounds with high antioxidant capacity in both kernels and shells make pecan nuts an important dietary source of antioxidants. Villarreal-Lozoya et al. (2007) reported that phytochemical constituents and antioxidant capacity (ACORAC values) of pecan varieties ranged from 372 to 817 mu mol trolox equivalents g−1 defatted kernels, while total phenolics ranged from 62 to 106 mg of chlorogenic acid equivalents g−1 defattened kernels. They also reported that condensed tannins varied from 23 to 47 mg catechin equivalents g−1 defattened kernels. Phenolic compounds with high antioxidant capacity in kernels and shells indicate that pecans can be considered as an important dietary source of antioxidants. Another important consideration when determining phenolic compounds and antioxidant capacity of pecan kernels is that samples must be previously defattened and measured in the acetone fraction, since different solvents deplete the samples and allow a more precise measurement (Pinheiro do Prado et al., 2009a, b). Importantly, pecans are rich in carotenoids, flavonoids and proanthocyanidins, having high content of phytosterols as well (Bhagwat et al., 2004). All of these are associated with improving the antioxidant capacity of our body. For the reasons described above, health specialists recommend the inclusion of nuts in diets to achieve a healthier feeding style (Mukuddem-Petersen et al., 2005; López-Uriarte et al., 2009). Observational studies suggest that nut consumption is inversely associated with the incidence of cardiovascular disease and cancer (Oliver-Chen and Blumenberg, 2008). These facts may explain why nowadays pecans are receiving a wider attention from health-caring consumers. It must be emphasized also that pecans, like other nuts and almost any foodstuff, may trigger allergic reactions in susceptible individuals and specific antigens have been developed for accurate diagnosis (Venkatachalam et al., 2007).

8.3

Harvesting, handling and storage

Harvest is accomplished in different ways, and in an increasing fashion. Mechanization is becoming the most common way, varying depending on the financial resources available to growers. Figure 8.1 shows a typical sequence common to heavily mechanized operations. 8.3.1 Soil preparation Since the nuts are picked directly from the ground, soil preparation is very important and its objective is getting a surface as flat and smooth as possible. 8.3.2 Tree shaking Once the soil is prepared, the next step is getting the nuts off the tree. This is accomplished by shaking the trees with machinery specially developed for

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Fig. 8.1

Description of typical mechanized harvest operations in a commercial pecan orchard.

nut crops (see Plate XIV in the colour section between pages 238 and 239). Growers have the choice of having their own machinery or hiring a contractor. Many prefer the latter since they avoid the high investment and maintenance costs involved, as well as the problem of having to train personnel every season, not to mention the highest risk of inflicting mechanical injuries to trunks and limbs because of a careless operation or an unskilled operator. By shaking the main trunk and limbs, the nuts are separated and fall to the soil or onto canvas previously spread underneath the trees. In the latter case, the nuts are collected from the canvas and loaded directly into containers to be transported to the sorting facility (Figs 8.2–8.5 and Plate XV in the colour section). If felled directly onto the soil, then the next procedure is followed. 8.3.3 Wind row formation Wind roads are rows of nuts between the tree lines, leaving them ready to be picked by a harvester, and specially designed implements named V-rakes are connected to the front of tractors to create these wind roads of pecans.

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Fig. 8.2 Manual collection, an alternative to mechanization (courtesy of Dr Humberto Núñez).

Fig. 8.3

Nuts in a row ready for pick up (courtesy of Dr Humberto Núñez).

8.3.4 Nuts pick up and initial transport The harvester outputs the nuts into containers to be transported to the sorting facility and separates leaves and light debris by blowing them away to the sides. It must be pointed out that normally harvest should follow shuck dehiscence, but

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Fig. 8.4

Picking up of nuts and loading for transport to sorting facility (courtesy of Dr Humberto Núñez).

Fig. 8.5 Manual selection, sizing and grading of in-shell pecans (courtesy of Dr Humberto Núñez).

under particular circumstances it may be desirable to harvest as soon as the endosperms are ripe, without regard to shucks still being closed. Therefore they must be eliminated in an intermediate step, before sorting and grading can be attempted. Since a wide range of technologies are available, the above procedure is adjusted accordingly, but the final objective remains the same: getting the nuts

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off the trees and collecting and transporting them to the storage facility, as fast as possible. 8.3.5 Immediate nut management Once the nuts are in the storage facility, they are handled either in sacs or metal containers that hold up to 1000 kg of in-shell pecans. Commercial storing conditions commonly used are −13.8 to −9.4 °C and 40% relative humidity (RH). Given the necessity that nuts may be stored for up to three years (more commonly for up to 10 months) the rancidity index must stay below 0.1% of free fatty acid content. 8.3.6 Preparing nuts for processing Once the nuts are ready for process, they are tempered at ambient temperature for 24 to 36 hours, which brings some moisture back into the nuts. Before pasteurization may be attempted, the nuts must be conditioned at room temperature for 4 to 8 hours in tanks, while water is sprayed on top. Pasteurization is achieved by hot water baths with a temperature range between 71.1 to 76.6 °C and an exposure time that varies widely within the industry. Since this is considered a critical control point, it is important that if any microbial assessment is to be considered, sampling should be done right after this step. 8.3.7 Shelling At this point the nuts are ready to be shelled and this is accomplished by a two step process. First, the nuts are mechanically cracked and second, the shells are removed by aspiration. Another alternative is by running everything on water and separating materials by flotation, although this causes water intake by kernels, which has to be adjusted later on. 8.3.8 Sizing and grading Afterwards the nuts are sorted by size, and arrays of several electronic sorters guarantee a good separation. Grading according to color may be achieved through a wide spectrum ranging from manual to infrared technologies depending on the operation size and financial resources. As a final selection step, sizing is done by running the meats through screens, although it can also be done along a band and manually picked. Before packing, the meats may be screened for metal debris using magnets and metal detectors. This process may be repeated two or three times to ensure the absence of this type of physical contaminant, which may include ferrous, non-ferrous and stainless steel particles. 8.3.9 Packing A 13.6 kg box is the industry standard for packing pecans, but bags of 226.8, 453.6 and 907.2 g (8, 16 and 32 ounces, respectively) are also commonly found

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at retailers. Even when boxes are used, the meats are first bagged in food grade polyethylene bags, heat sealed under vacuum. Box dimensions are 38.7 × 28.6 × 25.7 cm (15¼ × 11¼ × 10⅛ inches) (L × W × D) and preferred construction is single-wall corrugated Kraft fiberboard, wax-coated inside to delay oil penetrations. When using boxes, palletizing standards are ten boxes per layer by five boxes high for a total of 50 boxes on a 121.9 × 101.6 cm (48 × 40 inches) standard GMA pallet. 8.3.10 Early season harvest Seed testa color is a quality attribute of paramount economical significance in the pecan industry. It is negatively affected by exposure to high temperatures, as occurs while ripenned nuts are left on the tree waiting for shuck dehiscence to start harvesting. Therefore, early season harvest is becoming popular, particularly in those places where fall temperatures are still high. Herrera (1994) found that Western Schleys grown at Las Cruces, New Mexico can be harvested up to four weeks in advance and artificially dried without deleterious effects on flavor. However, this creates a different problem as shucks must be mechanically removed from nuts, so specific equipment has needed to be designed (Verma et al., 1991). Also, nut water content must be lowered to 4% from as high as 24% (Herrera, 2005) since it has been noted that nuts with a 6% water content do not store well (LSU, 2009). Early harvest is a common practice in the southern Sonoran Desert of Mexico, which advances harvest for up to 40 days as compared with its counterparts in the Mexican highlands growing at the same latitude.

8.4

Current quality grading system

The following account summarizes the quality expected for export pecan halves and pieces in the American industry as followed by The Green Valley Pecan Company of Southern Arizona (www.greenvalleypecan.com) and is based on outlines defined elsewhere. 8.4.1

Quality standards

Microbiological A total plate count of less than 10 000 cfu g−1, yeast and mold below 1000 cfu g−1, and coliforms below 100 cfu g−1, while E. coli, Staphylococcus and Salmonella should not be detectable. Chemical To ensure minimum rancidity, a maximum free fatty acid content of 0.4% and a maximum peroxide value of 5 meq kg−1 are required. As for contaminants, on aflatoxin level of 2 ppb is set as the maximum limit.

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Physical contaminants Since shell pieces may escape detection and become a physical contaminant, the maximum standard allowed for each 45.4 kg (100 lbs) has been set at three hard shells for pecan halves, for large to medium pieces up to four hard shells and no more than five hard shells in the case of small pieces. As described before, magnets and metal detectors are used to avoid metal contaminants, both ferrous and nonferrous, as well as stainless steel pieces. Although no particular mention is made regarding insects and insect parts, it is advisable to avoid their presence and it is in the smallest pieces where their detection may become more difficult. 8.4.2 Color As for physical characteristics, nut color must be a characteristic golden or amber, while meat texture should be firm and crispy. No musky or rancid odors should be present. The high linoleic acid content of pecan kernels make them highly susceptible to becoming rancid (Herrera, 2005), thus every attempt to avoid this defect must be taken into consideration. 8.4.3 Sizing Classification for halves and pieces according to size is accomplished through screens of different sizes, and these are shown in Table 8.2. First, there are three broad categories, Halves, Pieces and Meal, and each is subdivided in Table 8.2 Size classification of pecan halves and pieces according to industry standards in the USA and equivalents in the metric system Category

Units

Nut halves Mammoth Jr. Mammoth Jumbo

per pound 200–250 250–300 300–350

per kilogram 440–550 550–660 660–770

Pieces Extra large Large Large/medium Medium Small/medium Small Midget

Screen size in inches 36/64 to 28/64 28/64 to 19/64 26/64 to 19/64 22/64 to 16/64 19/64 to 16/64 16/64 to 12/64 12/64 to 8/24

in mm 14.3 to 11.1 11.1 to 7.5 10.3 to 7.5 8.7 to 6.4 7.5 to 6.4 6.4 to 4.8 4.8 to 3.2

Meal Granule Meal

Screen size in inches 8/64 to 5/64 5/64

in mm 3.2 to 2.0 2.0

Source: The Green Valley Pecan Company (2010) (http://www.greenvalleypecan.com).

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smaller categories. For example, in descending order, nut halves are divided into Mammoth, Jr. Mammoth and Jumbo. Nut pieces are comprised by Extra Large, Large, Large/Medium, Medium, Small/Medium, Small and Midget. Finally, Meal can be either Granule or Meal. The count of units per pound of meat implies that the smaller the count, the bigger the kernel parts; therefore, the Mammoth class includes the biggest halves, while Meal includes the smallest particles, basically the finest pieces capable of going through a very small mesh.

8.5

In-shell and shelled pecans

Once harvested, pecans can be managed in-shell or shelled, depending on several factors as described below. 8.5.1 In-shell nuts Although the shell itself represents a good barrier for gas exchange, it does not prevent air from coming in contact with kernels and eventually triggering oxidation processes, leading to oil rancidity and skin darkening. It should also be taken into account that in-shell pecans use more storing space than shelled kernels, therefore in-shell pecans are less efficient in space use in the cold room and during transport. However, very often pure economic reasons are the sole basis to define if the nuts are to be shelled or not, since extra infrastructure is required, and that implies expensive facilities and equipment, as well as trained labor. Often, because individual growers do not have the resources or do not meet the volumes for a profitable cost/benefit ratio, cooperative associations are formed to make a more efficient investment. Otherwise the crop is sold to middlemen, with obvious disadvantages and repercussions for growers but without the need for further investment and the concomitant risks. Advantages associated with in-shell pecans include that they can be stored longer than shelled kernels, and that the shells are natural barriers protecting kernels from bruising and delaying kernel oxidation and rancidity (LSU, 2009), as mentioned before. 8.5.2 Shelled kernels If shelling is an option, then the nuts are sorted according to size and color and cracked open to harvest the meals, following specific schedules according to market demands. If shelling is not an option, then the nuts must be cold stored anyway to avoid quality deterioration, which, although slow, occurs anyway. Often, however, cold storage is not possible and rancidity will develop depending directly on temperature. It must be considered that shelled kernels become darker and develop red colorations quicker than in-shell pecans (Grauke et al., 1998). When temperatures are higher (warmer sites) rancidity develops quicker. Hence, the need for marketing such a crop is greater and the likeliness of getting a fair price declines drastically. From the sanitary standpoint, since shelled pecans are

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more likely to harbor pests like pecan weevil and others, avoiding transport of in-shell pecans must be part of any quarantine effort, making shelling part of an integrated pest control strategy.

8.6

Description of main quality attributes

Florkowski et al. (1992) acknowledged the complexity of communicating on quality issues in the pecan industry, so that standard grades could be related to quality attributes and prices. Quality pecans are defined by several factors, among the most important being kernel size and color, nutmeat-to-shell ratio, freedom from rancidity, and lack of defects, either physical or caused by insects. These factors, along with specific gravity and shell thickness, are useful not only to grade nuts but are also important factors for the design of handling and processing equipment (Kotwaliwale et al., 2004). Not restricted to processing, they have also been helpful in defining trait targets in breeding programs as well (Florkowski et al., 1992). Using direct gas chromatography (GC) as an objective measurement of several volatile compounds and a trained panelist to assess flavor scores as subjective variables, Forbus et al. (1980) reported that the best correlation coefficients were found when comparing flavor score vs. total volatiles (−0.95) and flavor score vs. tridecane levels (−0.93). Kernel size defines the best possible use for each product. While the biggest sizes are usually used to improve the visual appearance of the final product, the smallest are demanded for baking purposes, with a whole range of uses and demands for the intermediate sizes. Prices correspond accordingly. Kernel color is an indication of quality, since the darker colors are associated with rancidity development, the result of oxidation processes. Oxidation of endogenous leucoanthocyanidin to phlobaphe, cyanidin and delphinidin has been pointed out to be the cause of the red-brown discoloration of kernel testa (Senter et al., 1978). Kernel color is one of the parameters to estimate quality and value, before actual shelling and processing (Heaton et al., 1975), and a simplified color rating system, based on the Munsell Color System but with only six classes, was developed for the pecan industry (Thompson et al., 1996). When kept at room temperature, most color changes occur during the first 18 weeks (Kanamangala et al., 1999), therefore avoiding exposure to such conditions delays the onset of color deterioration. Kernel color transitions change from yellow to red hues and from lighter to darker values, although it changes very little in chroma. Color is also dependent upon genotype, and different years yield different colors for the same variety (Grauke et al., 1998). Therefore, environmental conditions during nut ripening, around harvest and after harvest have a decisive influence in color development. The warmer the temperature, the darker color the kernel develops. Higher elevations and latitudes (cooler temperatures) tend to produce light colored kernels, while the opposite occurs at lower elevations and latitudes where both day and night temperatures will be warmer. However, for the

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same latitude, elevation plays a key role in defining quality, and it is expected to find the lightest colored kernels at high elevations, but as a convenient trade off, lower sites may achieve an earlier ripening, as is commonly noted in Northern Mexico, where Western Schleys and Wichitas are grown along 28° NL, but with differences in elevation up to 1000 m. The nutmeat-to-shell ratio describes how much of the total crop is usable. It is the result of orchard management, as much as it is a genetic trait, and nuts from improved varieties have higher ratio than native trees, which are typically thickshelled and small. Also, careful management with appropriate technologies will result in bigger ratios. Although the current nut and kernel evaluation system was developed by the USDA-ARS, and it has been in use for decades to evaluate shelling efficiency, data suggest that there is still room for improvement and other variables should be taken into consideration (Thompson and Grauke, 2003).

8.7

Storage

An efficient strategy for pecan storage calls for a fast and effective drying after harvest, followed by cooling of nuts or kernels, in order to delay kernel quality deterioration (Heaton et al., 1982), regardless if the crop will be shelled or not. In general, benefits of low temperature storage are a better retention of fresh flavor, followed by color, aroma and texture (Herrera, 2005). A brief description of some of the recommended practices follows. 8.7.1 Nut moisture content Nut moisture content during harvest is in the order of 24%, and it should be lowered to 4%, since a 6% water content may lead to mold development and the nuts do not store well (Herrera, 2005; LSU, 2009). Besides the regular gravimetric methods to determine water content, pecan kernel moisture has also been measured by rf-impedance methods with promising results (Nelson et al., 1992). To achieve appropriate moisture content, growers may artificially induce nut dehydration by means of adding heat and dry air. When nuts are harvested early in the season, this practice is a must and is commonly done in processing facilities. However, without access to such infrastructure, a common practice is letting the nuts dehydrate while still on the tree, which leads to a late harvest season. Depending on whether this may pose a risk, since losses of quality are inherent. For example, Heaton et al. (1982) when comparing Stuart, Wichita and Schley nuts harvested in late season, found no color differences on these cultivars, but the latter has less flavor stability. 8.7.2 Appropriate temperature and humidity Having access to pecan samples stored in hermetically sealed containers for 25 years at 20 °C, Hao et al. (1989) were able to compare them with nuts kept

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under the same conditions but for only ten months. They evaluated sensory, microbial and compositional characteristics, finding that the only significant change was in texture, concluding that pecan can be stored for up to 25 years under those particular conditions. However, achieving those conditions is both difficult and costly for the industry, and appropriate adjustments must be done under commercial conditions. Studying changes in pecans stored at 0.6 °C and 75% RH for 12 months, Yao et al. (1992) did not detect changes in kernel color, oil quality, tocopherols nor conjugated diene levels. Color changes in kernels frozen for up to a year were followed by Grauke et al. (1988) finding that, compared with unfrozen controls, frozen kernels were more red in hue but could not be distinguished on the basis of lightness; also, samples frozen for 12 months had reduced chroma compared to those frozen for six months or unfrozen. Present knowledge leads extension programs to advise that in-shell pecans can be stored for longer periods than shelled nuts, because of the shell protective effect. Also, native pecans storage life can be extended from three months at 21 °C up to eight years at −18 °C (LSU, 2009). Varieties like Western Schley can be kept at 21 °C for up to four months when in-shell, but only three months when shelled, but no difference were found at −18 °C lasting between two and five years (Herrera, 2005). Differences like those may be attributed to unsaturated oil contents, which along with temperature and moisture content are the main factors defining storability (Herrera, 2005). Nonetheless, other conditions should be taken into account, like the fact that pecan pieces have shorter shelf life than halves because of their larger surface/size ratio. As a result, nutmeats may be expected to last only for one or two months at 0 °C (Herrera, 2005). 8.7.3 Packaging materials Refrigerated or frozen pecans should be placed in airtight containers (LSU, 2009). Since shells are a natural barrier protecting kernels from oxidizing faster, very often the situation calls for storing shelled kernels, which requires packaging materials of specific conditions. Dull and Kays (1988) found that kernels packaged in polyvinylidenechloridecoated cellophane packaging films with low oxygen transmission rates were of acceptable quality after six months storage at 24 °C and 60% RH. Later Kanamangala et al. (1999) found that reducing fatty acid content of kernels by partial lipid extraction, resulted in a longer shelf life. They assumed that in addition to decreasing the total amount of lipid available for oxidation, the free fatty acid lipid component that correlated with the development of rancidity was reduced by extraction, most likely the linoleic fraction (Herrera, 2005). Although interesting from the analytical standpoint, implementing a strategy like this would represent an extra task that industry must consider. Using either polypropylene plastic containers or nylon-polyethylene plastic films under vacuum, Oro et al. (2008) evaluated kernels at 23 °C for up to 150 days without significant differences between the two packages. Shelf life was estimated at 120 days, although kernel darkening was detected.

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8.8

Postharvest physiology factors affecting nut quality

8.8.1 Respiration Pecans, like all nuts, have a very low respiration rate [about 1 mL kg−1h−1 at 10 °C] (Kader, 2002; Kader et al., 2010), as dormant embryos metabolism is very low, a situation accentuated when they are artificially dehydrated after harvest. Therefore, their shelf life is not threatened because of respirationdependent anabolic reactions, but because of the lipid oxidation process leading to rancidity and skin darkening (Senter and Hdrvat, 1976; Florkowski et al., 1992; Toro-Vazquez et al., 1999; Herrera, 2005).

8.8.2 Color Kernel color is one of the most important quality attributes and develops once shuck dehiscence starts (Kays and Wilson, 1977). Kernel darkening is associated with oxidation of oils (Woodroof, 1979) and rancidity development of free fatty acids (Oro et al., 2008). The seed testa, another designation for the kernel surface, may also become dark when shucks fail to open because of mechanical damage and insect injuries, particularly those caused by sucking insects like stink and coreid bugs, whose bite can penetrate through shells (Yates et al., 1991). There are varietal differences in hemipteran kernel damage susceptibility, but interestingly, it is the females that cause most of the injuries (Dutcher et al., 2001) and dark spots develop around the feeding site. Conditions during late harvests favor kernel darkening and to avoid such problem spraying with ethylene-liberating products in conjunction with auxins used after endosperm filling cause the shucks to open allowing uniform harvests without deleterious effects on foliage (Martínez-Téllez et al., 1995).

8.8.3 Rancidity As mentioned before, along with darkening, rancidity is the other major issue causing pecan quality deterioration. Both are the result of oxidation processes. In the first case is the oxidation of leucoanthocyanidins in kernels (Senter et al., 1978), while rancidity develops when pecan oils are oxidized (Toro-Vazquez et al., 1999). Because pecan oil is so rich in fatty acids (Santerre, 1994), particularly linoleic acid (Villarreal-Lozoya et al., 2007), this makes it particularly susceptible to becoming oxidized, thus getting rancid (Herrera, 2005). Oxidation of unsaturated fatty acids results in the development of undesirable aromas and flavors as well; when this occurs nut shells will have a dark and oily appearance. Peroxide content is the major variable used to measure rancidity and most standards call for a peroxide index value <4 milliequivalents of peroxide Kg−1 of oil. Oro et al. (2009) obtained pecan oil from orchards grown in Brazil by cold pressing and evaluated their shelf life for up to 120 days at 22.5 °C in amber glass flasks. Their findings demonstrated that according to chemical analyses and color assessment, after 120 days the oil still had adequate quality according to Brazilian

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legislation for crude oils; on the other hand, sensory analysis showed that sensory characteristics were unaltered for 60 days of storage, a significant increase in oxidized taste and bitterness developed reducing nut taste and acceptability after 90 days and after 120 days sensory changes became more pronounced and were unacceptable. Therefore, shelf life of crude pecan oil stored under those conditions was restricted to only 90 days. To avoid rancidity postharvest management, including storage, plays an important role, as described below.

8.8.4 Storage Besides the storage conditions previously described, it is also important to consider that pecan nuts must be stored in clean facilities free from biological, chemical and physical contaminants at adequate temperatures and relative humidities as described. Because of its high lipidic content, pecan nuts favor the absorption of odors from external sources, consequently they should not be stored along with produce with strong aromas (Kader et al., 2010) and other odoriporus materials (Herrera, 2005). In the case of cold storage facilities run with ammonia, particular emphasis must be taken into consideration because ammonia leaks may lead to kernel darkening (Kader, 2002).

8.8.5 Pests and diseases This section is discussed under the premise of postharvest management and implications in consumer safety and do not describe those from the agronomic and plant pathology standpoints. During crop development pecan may be exposed to different microbiological contaminants like Aspergillus flavus and A. parasiticus, but it is after harvest that their mycelium develops and aflatoxins may be synthesized and accumulate (Beuchat, 1975). Other fungi like Penicillium, Fusarium, Rhizopus, Cladosorium and Alternaria may also be invading the nuts and their development is favored by high humidity during storage (LSU, 2009). Nowadays, pecan weevil (Curculio caryae [Horn]) is the most serious insect threat to the pecan industry. Although capable of destroying the whole crop, even minor injuries may become the point of entry for spores of opportunistic fungi, whose effects become evident during postharvest management (Ree et al., 2010). Weevil infestations also present another hazard, since their control must rely on highly residual, broad spectrum pesticides, which increase the possibilities to contaminate the chemical residues of the nuts. Therefore, every single strategy to avoid dispersal of this pest should be taken seriously, since once infested, typical integrated pest management (Harris, 1983), or organic farming becomes almost non viable and environmental effects increase dramatically.

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8.8.6 Other disorders of postharvest influence Shuck decline and premature nut germination are two problems associated with fruiting stress caused by the biannual bearing characteristic of pecans, as well as water relations (Sparks et al., 1992). Smith et al. (1993) discussed the positive effects of mechanical fruit thinning to avoid overloading the trees in the cropping year. Wakeling et al. (2002) also described the presence of opalescent kernels in Australian pecans. This disorder is described as the presence of unattractive browning of the nut interior, as compared to the white interior of normal kernels. Opalescent kernels have lower levels of calcium and higher amounts of oils compared to normal nuts. It is considered that up to 70% of the Australian crop may exhibit opalescence to some degree.

8.9

Potential improvements in handling

Although shucks may be seen as the part of the crop biomass without further use, they are rich in phenolic compounds and lignins. Also, they are proportionally correlated with nut fresh and dry weight (Thompson, 2005) and as such should be taken into account in breeding programs as favorable traits. As an interesting lateral use for a crop residue like nut shells, a recent study conducted in Northern Mexico found that poly- and monomeric phenolic extracts of pecan shells, even at low concentrations, showed high antifungal capacity against many fungal species, in particular up to an 80% control of the Fusarium oxysporum strains tested, which are responsible for wilting in many commercially important crops (Osorio et al., 2010). New technologies are in the making and some may revolutionize the way pecans are managed. For example, electron beam irradiation may become a potential tool to avoid microbial contaminants. Little effect on nut phytochemical components and antioxidant capacity has been found, although tocopherol content decrease with irradiation, while the peroxide value increased at later stages without significant changes in fatty acid composition. Nonetheless, some browning may develop during storage. This may become an interesting technology in the near future (Villarreal-Lozoya et al., 2009). Also, recent work has demonstrated that disinfection of pecans with gamma irradiation at 1 kGy did not affect either its vitamin E content, nor its sensory qualities and was recommended by Taipina et al. (2009). As far as imaging, Kotwaliwale et al. (2007) used soft X-ray digital imaging for non-destructive quality evaluation, being able to determine nutmeat content, kernel defects and insect presence. This implies that in the near future nut selection may be assisted by more powerful techniques, not just for quality aspects, but for pest screening and producing quarantine definitions. Pecan nut quality has also been assessed by determining X-ray attenuation coefficients by polychromatic X-ray imaging. Attenuation coefficient values along with pixel intensity in digital radbiographs can be used non-destructively to evaluate quality features such as: nut fill; mechanical, insect or physiological injuries to nut meat and intact pecans; as well as shell thickness (Kotwaliwale et al., 2006).

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An important challenge during storage is decreasing nut exposure to air (oxygen), since this favors rancidity development. Oro et al. (2008) reported changes in pecan quality packed in either polypropylene plastic containers or nylon-polyethylene plastic films and stored at 23 °C for up to 120 days. They did not find significant differences in kernel quality attributes and shelf life was estimated at 120 days, but kernel darkening was detected. From the consumer safety standpoint, it has been recommended as a safe practice to routinely screen the pecan crop for the potential presence of aflatoxinproducing fungi, as well as microbial contamination by coliforms and Salmonella, as established for other crops (Arrus et al., 2005).

8.10

Processing

Pecans, like other dried fruits, can be marketed in a wide variety of presentations, each implying a different process. Although most of pecans are marketed either as shelled or in-shell, many uses have been developed and could be classified in two groups, as follows. 8.10.1 Minimal processing Besides in-shell pecans, this group includes shelled pecans and the different qualities obtained after shelling, which includes all stages from halves to meal. The final presentation in the retail market varies from rustic burlap bags to containers in plastic or from mammoth sizes to fine meal made for direct consumption or for baking and cooking. Marketing of large volumes for either the international or domestic markets may be included in this group as well. 8.10.2 Processed products Candied pecans are representatives of a more detailed processing. It is possible to find pecans prepared as brittles, toffee, spiced with cinnamon, flavored as cajun, jalapeño, mesquite and garlic. They can be smoked, honey roasted, honey toasted, roasted and salted or honey corn and presented as pralines or pieces covered with either dark, milk or white chocolate. Several other presentations are available depending on regional preferences and inventions. Cold pressed pecan oil is sold as dressing, while pecan syrup is offered as an alternative for sweets. Considering all of the positive health attributes of pecan consumption, isolation of individual components is another potential processing alternative.

8.11

Conclusions

Consumers are looking for healthy foods that offer a protective means against diseases associated with our lifestyle and pecans are a rich source of

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phytochemicals with antioxidant, anti-proliferative, anti-inflammatory, antiviral and hypocholesterolemic properties. Their nuts are rich in calories, linoleic acid, some micronutrients and vitamins. They are particularly rich in mono- and polyunsaturated fatty acids and regular pecan consumption decreases total cholesterol and LDL-cholesterol, lowering the risk of heart disease. Given the present consumer interests, it is expected that the pecan market will expand. Technologies for harvest, storage and handling pecans are diverse and depend mostly on the resources available for growers. Besides, increasing knowledge in designing new tools will be continuously available. Quality attributes for pecans are well defined and increasing regulations allow the industry to offer better products. Main quality attributes include kernel size and color, nutmeat to shell ratio, free from rancidity and lack of defects. Kernel darkening and rancidity are the most important postharvest challenges as far as quality deterioration. Both are the result of oxidative processes, the first related to oxidation of leucoanthocyanidins, while the latter is caused by oxidation of unsaturated fatty acids. A careful management, beginning in the orchard and followed through harvest and postharvest management and storage, delays those oxidative reactions, keeping kernels in excellent conditions. Reducing nut water content, avoiding high temperature exposure, and cold storing as soon as possible set the conditions to prevent quality deterioration. Following good agricultural and manufacturing practices and establishing HACCP programs are good strategies to avoid the presence of contaminants that may affect consumer health. Pecan benefits are not circumscribed to nut consumption; shells represent an important biomass byproduct and exploitation of its properties will soon be available.

8.12 Acknowledgments The authors express their gratitude to Roger Hooper and Bruce Caris from The Green Valley Pecan Company for their valuable inputs.

8.13

References

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The Green Valley Pecan Company (2010), Green Valley AZ. Available from: http://www. greenvalleypecan.com/freshness.asp [Accessed on 25 July 2010]. Thompson TE (2005), Pecan fruit shuck thickness is related to nut quality, HortScience, 40(6), 1664–1666. Thompson TE and Grauke LJ (2003), Pecan nut and kernel traits are related to shelling efficiency, HortScience, 38(4), 586–590. Thompson TE, Grauke LJ and Young EF (1996), Pecan kernel color: Standards using the Munsell Color Notation System, J Amer Soc Hort Sci, 121(3), 548–553. Toro-Vazquez JF, Charó-Alonso MA and Pérez-Briceño F (1999), Fatty acid composition and its relationship with physicochemical properties of pecan (Carya illinoensis) oil, JAOCS 76(8), 957–965. USDA (2004) ‘Database for the Proanthocyanidin Content of Selected Foods 2004’. Available from: http://www.nal.usda.gov/fnic/foodcomp/Data/PA/PA.html [Accessed on 10 August, 2010]. USDA (2005) ‘Nutrient Database for Standard Reference. Release 16’. Available from: http://www.nal.usda.gov/fnic/foodcomp/Data/SR16/sr16.html [Accessed on 10 August, 2010]. USDA (2006) ‘Nutrient Database for Standard Reference. Release 17’. Available from: http:// www.nal.usda.gov/fnic/foodcomp/Data/SR17/sr17.html [Accessed on 10 August, 2010]. USDA (2010a) ‘Classification’, Natural Resources Conservation Service. Available from: http://plants.usda.gov/classification.html [Accessed on 10 August, 2010]. USDA (2010b) ‘Classification for Kingdom Plantae Down to Genus Carya Nutt’, Natural Resources Conservation Service. Available from: http://plants.usda.gov/java/Classificat ionServlet?source=display&classid=CARYA [Accessed on 10 August, 2010]. Venkatachalam M, Kshirsagar HH, Seeram NP, Heber D, Thompson TE, et al. (2007), Biochemical composition and immunological comparison of select pecan [Carya illinoiensis (Wangenh.) K. Koch] cultivars, J Agric Food Chem, 55, 9899–9907. Verma BP, Heaton EK and Zaltzman A (1991), Machine for removing shucks from pecans, Transactions of the ASAE, 34(1), 38–42. Villarreal-Lozoya JE, Lombardini L and Cisneros-Zevallos L (2007), Phytochemical constituents and antioxidant capacity of different pecan Carya illinoinensis (Wangenh.) K. Koch cultivars, Food Chem, 102(4), 1241–1249. Villarreal-Lozoya JE, Lombardini L and Cisneros-Zevallos L (2009), Effects on phytochemical constituents and antioxidant capacity of pecan kernels [Carya illinoiensis (Wangenh.) K. Koch] during storage, J Agric Food Chem, 57(22), 10732–10739. Wakeling LT, Mason RL, D’Arcy BR and Caffin NA (2000), Australian pecan nut production and processing, Food Australia, 52(12), 574–578. Wakeling LT, Mason RL, D’Arcy BR and Caffin NA (2001), Composition of pecan cultivars Wichita and Western Schley [Carya illinoinensis (Wangenh.) K. Koch] grown in Australia, J Agric Food Chem, 49(3), 1277–1281. Wakeling LT, Mason RL, D’Arcy BR and Caffin NA (2002), Opalescence in Australiangrown pecan kernels: Occurrence and causes, J Food Sci, 67(8), 2873–2880. Wood BW and Mc Means JL (1982), Carbohydrates and fatty acids in developing pecan fruit, J Am Soc Hort Sci, 107(1), 47–50. Woodroof JG (1979), Tree Nuts, Vol II, Second Ed, The AVI Publishing Company, Inc, Westport, Connecticut, USA. Yahia EM (2010), The contribution of fruit and vegetable consumption to human health, In: Phytochemicals: Chemistry, Nutricional and Stability, Wiley-Blackwell, Chapter 1, pp 3–51. Yao F, Dull G and Eitenmiller R (1992), Tocopherol quantification by HPLC in pecans and relationship to kernel quality during storage, J Food Sci, 57(5), 1194–1197. Yates IE, Tedders WL and Sparks D (1991), Diagnostic evidence of damage on pecan shells by stink bugs and coreid bugs, J Amer Soc Hort Sci, 116(1), 42–46.

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Plate XIV (Chapter 8) Getting the nuts off the tree by shaking. Canvas to aid in collection (courtesy of Dr Humberto Núñez).

Plate XV

(Chapter 8) Manual sorting of kernels and elimination of shells (courtesy of Dr Humberto Núñez).

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9 Persimmon (Diospyros kaki L.) A. B. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand and R. Ben-Arie, Israel Fruit Growers’ Association, Israel

Abstract: Persimmons are temperate, climacteric fruit, externally attractive with very little acidity and primarily sweet flavour. Maturation involves colour changing from green to yellow-orange or red, accompanied by increased soluble solids content (SSC), reduced fruit firmness and astringency. Commercial maturity is generally determined by colour. Persimmon’s unique characteristic is a high soluble tannin content, responsible for astringency, which may or may not decline with maturation. Thus, cultivars are differentiated by the presence of low astringency (in ‘sweet’ persimmons), or extreme astringency, lost naturally with fruit softening. Treatments to remove astringency are generally applied postharvest, mostly using high CO2. Optimum storage is generally at 0 °C, but higher temperatures may result in chilling injury. 1-MCP and modified/ controlled atmosphere storage (MA/CA) can extend storage duration to three months. Most external disorders are expressed as skin blackening, and pathological disorders are generally low unless storage exceeds two months. Key words: Diospyros kaki, persimmon, tannins, astringency, chilling injury, anoxia tolerance.

9.1

Introduction

9.1.1 Origin, botany, morphology and structure The commercial persimmon fruit is derived from Diospyros kaki L. in the family Ebenaceae. It originated from China (with records of production over 3000 years ago) and was introduced to Japan and Europe in the seventh and seventeenth centuries, respectively. Other Diospyros species include D. virginiana (N. America) and D. lotus (Middle East), but these are generally used as rootstocks. The trees are small to moderate in size with large, leathery, green leaves, which turn brilliant yellow, orange and red during autumn (see Plate XVI in the colour section between pages 238 and 239). Leaves may fall, leaving the golden fruit hanging on bare branches, thus making it a popular subject for Japanese and Chinese art. Frost and cold tolerance is generally high.

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Persimmon fruit are botanically a berry, flat to round (‘Fuyu’ and ‘Triumph’) or elongated (‘Rojo Brillante’ and ‘Hachya’), with weights ranging from 50 to 300 g. The typical colour, yellow to orange, changing to a deep red with maturity and/or ripening, creates a visually pleasing fruit. The calyx is a green four-lobed structure surrounding the stem-end of the fruit. Persimmon fruit are dependent on the calyx for gas exchange into the fruit, as there are no stomata or lenticels on the fruit surface, which is covered with a waxy cuticle (Perez-Munuera et al., 2009). The flesh is orange coloured and made up of a dense cell structure, which may have large almond-shaped seeds in the inner section of each of the approximately eight carpels, but fruit will develop parthenocarpically (although they then tend to be somewhat smaller). Two significant characteristics of persimmons are the astringency of fruit at harvest, and variable pollination. Astringency is the dry sensation in the mouth caused when soluble tannins from the fruit bind to proteins of the saliva, stopping them from ‘lubricating’ the mouth (the same sensation that occurs when drinking strong black tea or red wine). ‘Variant pollination’ is expressed as browning of the tissues surrounding the locules when seeds are present, whereas with ‘pollination constant’ types flesh colour is invariable. These two characteristics have led to the practice of classifying persimmons into four groups: pollination constant nonastringent (PCNA), pollination variant non-astringent (PVNA), pollination variant astringent (PVA), and pollination constant astringent (PCA). The most desirable are the PCNA group, which are edible at harvest. Cultivars of this group, mainly ‘Fuyu’, are primarily grown by Japan, Korea, Brazil, and New Zealand. Production in other countries is based on ‘Kaki Tipo’ (PVA) in Italy, ‘Rojo Brillante’ (PCA) in Spain and ‘Triumph’ (PVA) in Israel and South Africa. A number of ‘new’ PCNA cultivars have been ‘discovered’ in China in recent years (e.g. ‘Luotiantianshi’ and ‘Tianbaogai’), sparking considerable collaborative breeding research. It should be noted that there can be significant confusion in the correct identification of cultivars internationally and even within countries. Molecular screening tools might be helpful to clarify the identity of some of the various strains. 9.1.2 Worldwide importance and economic value FAO Statistical Databases (2001) shows 300 000 ha and 2 300 000 tonnes in production, a 2.5-fold increase since 1961. Current production (2008) is 3 628 000 tonnes (thus showing a continual increase in production), but only 18 000 tonnes of this is traded internationally. The approximate order of production by country is China (>60% of production), Japan, Korea, Brazil, Italy, Spain, Israel and Turkey, with over 90% of world production in Asia. Production is increasing in countries such as China, Korea, Brazil and Spain. 9.1.3 Culinary uses, nutritional value and health benefits Consumption is mostly in Asian countries where the sweetness, subtlety of flavour and lack of acidity is (generally) more appreciated. Persimmons can be consumed

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fresh, are rarely used in cooking, or may be consumed dried. Drying fruit is the main form of processing, but is generally labour intensive, since fruit must first be peeled, then hung to dry. Astringency is lost as fruit ripen, or they can be treated to remove astringency rapidly after harvest (e.g. CO2 treatment, see later). There is a return of astringency when the latter are subjected to heating, or cooked. The high contents of tannins, polyphenols, carotenoids, ascorbic acid and sugars indicate the high potential for health benefit from persimmon consumption, and these compounds have been the subject of intensive study in the last decade. Although clinical studies still need to be conducted, diseases that are considered likely to benefit from persimmon ingestion are cardiovascular, high cholesterol, diabetes, cancer, stroke and even intoxification effects (see review of George and Redpath, 2008). The greater antioxidative activity of high versus low molecular weight tannins might indicate that astringent cultivars are likely to have superior health benefits (Gu et al., 2008), but the effect of removing astringency has not been studied in this respect. The re-solubilisation of polymerised tannin under simulated stomach conditions might make such a study superfluous. It should also be noted that this re-solubilisation might be a reason for caution in consuming excessive amounts of fruit that have had their astringency artificially removed, since the formation of phytobezoars may occur under certain conditions.

9.2

Fruit development and postharvest physiology

9.2.1 Fruit growth, development and maturation Generally, the growth, development and maturation of persimmon fruit do not differ substantially from those of most fleshy, climacteric fruit, be they from temperate deciduous trees or evergreen subtropical and tropical trees. They exhibit a double sigmoid growth curve, whether seeded or parthenocarpic, and demonstrate typical colouration and softening once they complete their growth cycle and begin to mature and ripen. A very comprehensive review of the development of nonastringent persimmons is also relevant for the astringent types (George et al., 1997). Special attention has been paid to the involvement of the calyx lobes in fruit growth and development (Yonemori et al., 1996). Removal of the calyx during stage I of the growth cycle inhibited fruit growth, indicating the importance of the contribution of assimilates produced in this organ. However, at stage III, fruit growth remained unaffected by calyx detachment, unless the scar was sealed with Vaseline®, in which case fruit growth rate decreased. Apparently, this decrease is due to inhibition of fruit respiration, which was shown to be necessary for photo-assimilate accumulation during the final fruit swell at growth stage III, required to maintain the sink strength of the fruit (Nakano et al., 1998). A unique feature of the persimmon fruit is the abundance of specified tannin cells and the varietal differences in their morphology and metabolism, resulting in the four distinct groups described above. Non-astringent cultivars contain fewer and smaller tannin cells than astringent cultivars (Itoo, 1986), have different cell wall characteristics (Gottreich and Blumenfeld, 1991; Yonemori and Matsushima,

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1987), colour and shape (Yang et al., 2005). However, the PCNA group has been developmentally distinguished from the other three groups, with regard to its tannin content. Whereas in the latter the tannin content increases during stages I and II of fruit growth, in PCNA-type fruit its accumulation ceases during stage I and the tannin concentration therefore declines as the fruit continues to grow, resulting in a loss of astringency. Moreover, the tannin composition of PCNA fruit differs in that it does not coagulate in the presence of acetaldehyde. The loss of astringency in PVNA-type cultivars is related to the presence of the seeds that produce acetaldehyde and ethanol, thus causing a coagulation of the tannin, even before the fruit ripens. The PCNA-type cultivar is supposedly a recessive mutant of the astringent type and the cessation of condensed tannin accumulation at stage I of fruit development in these cultivars was shown to coincide with the gradual disappearance of DNA sequences of nine genes involved in flavonoid biosynthesis (Ikegami et al., 2005). 9.2.2 Respiration, ethylene production and ripening The ripe persimmon produces extremely low levels of ethylene (peaks below 5 nL g−1 h−1) and because of this, its climacteric status was initially questioned (Takata, 1983). The issue was more or less resolved when it was shown that postharvest fruit softening and colouration were accompanied by ethylene synthesis (Itamura et al., 1991). In the last decade, a number of molecular studies have demonstrated the involvement of the ethylene biosynthetic pathway and signal transduction in persimmon fruit ripening (Ortiz et al., 2006; Pang et al., 2007; Zheng et al., 2005). 1-MCP (a potent inhibitor of ethylene action that binds to the ethylene receptor site and applied commercially as SmartFreshSM) has been a valuable tool in elucidating the climacteric nature of the persimmon (Harima et al., 2003; Luo, 2007). The initiation of pseudo-climacteric ethylene production in detached young fruit (stage I) and in ripened mature fruit was shown to occur in the calyx, being modulated by water stress (Nakano et al., 2002, 2003). A water stress signal activates the expression of one of the three ACC-synthase genes (Dk-ACS2) in the calyx and the ethylene produced diffuses to the other fruit tissues, inducing autocatalytic ethylene production in the fruit by stimulating the expression of all three AC-synthase and two ACC-oxidase genes. Inhibition of ethylene production in the calyx by preharvest application of nickel, delayed ACC accumulation in the fruit, reduced on-tree fruit softening and prolonged the postharvest life of ‘Saijo’ persimmons by retarding softening (Zheng et al., 2006b). Other stresses that induce climacteric ethylene production, but without calyx involvement, are de-astringency treatments and wounding. Wounding also induces Dk-ACS2 expression, which is stimulated by 1-MCP, indicating a negative feedback response to ethylene (Zheng et al., 2005, 2006a). Ethylene perception and signal transduction in persimmon have been studied in relation to the expression of three ethylene receptor genes: Dk-ETR1, Dk-ERT2 and Dk-ERS1 (Pang et al., 2007). Dk-ETR1 is constitutive at a low basal level and independent of ethylene, although probably responsible for its perception.

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Dk-ETR2 and Dk-ERS1 appeared to be regulated by ethylene during fruit development and ripening and were enhanced in response to exogenous ethylene, indicating a possible role in autocatalytic ethylene production, especially for Dk-ERS1, which was much more abundant than Dk-ETR2. This recent study suggests a possible answer to the question of differences in the ripening behaviour and sensitivity to ethylene between persimmon types and cultivars, which has so far not been addressed.

9.2.3 Cell wall metabolism and softening Persimmon fruit softening is associated with middle lamella degradation, loss of cell wall material, and cell wall separation (Shin et al., 1991). These cell wall changes result from the increasing activity of cell wall degrading enzymes common to most fleshy fruit: pectin methyl esterase, polygalacturonase, β-galactosidase and cellulase. These cause a reduction in high molecular weight carbohydrate polymers (pectin, hemicelluloses, and cellulose) and increases in soluble pectic fractions and neutral sugars. The direct involvement of these changes in fruit softening has been demonstrated by the inhibited softening incurred by gibberellins (Ben-Arie et al., 1996), 1-MCP (Luo, 2007) and heat treatment (Woolf et al., 1997; Luo, 2006), as opposed to ethylene-accelerated softening (Chang et al., 2009). However, in rapidly softening ‘Saijo’ fruit, α-L-arabinofuranosidase activity was more closely related to softening than that of the other hydrolases (Xu et al., 2004). This might possibly be a response to the CO2 treatment, since no comparison has been made between natural softening and that induced by artificial removal of astringency. Cell wall metabolism may also contribute to the natural loss of astringency concomitant with softening, because of complex formation between soluble tannin and solubilised cell wall fractions (Taira et al., 1997).

9.3

Maturity, quality at harvest and phytonutrients

9.3.1 Maturity and quality at harvest The most obvious feature of persimmon fruit maturation is the change in colour from light orange/yellow to deep orange and on to red, the result of chlorophyll degradation and carotenoid biosynthesis. The principal carotenoids are initially β-cryptoxanthin, zeaxanthin, antheraxanthin and violaxanthin (Ebert and Gross, 1985; Niikawa et al., 2007). The change to red is due to lycopene accumulation, especially after harvest. Its occurrence in fruit on the tree might be a good harvest index. However, the best objective method for assessing fruit maturity is the Hunter a value, although the Delayed Light Emission method might be more suitable for automated mechanical fruit sorting (Forbus et al., 1991). Chemical changes accompanying fruit maturation that contribute to the taste of the ripe fruit are sugar accumulation, acidity and a decline in soluble tannin. The

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predominant sugars, in almost equal amounts, are glucose, fructose and sucrose, which increase throughout fruit development, reaching a constant level prior to harvest maturity. During postharvest ripening, the reducing sugars continue to increase due to invertase activity (Zheng and Sugiura, 1990), and a concurrent decline in sucrose levels (Del Bubba et al., 2009). Acidity in persimmons is relatively low even in immature fruit (c. 1%), but does not change with ripening. Malic acid, which is predominant, increases with maturity, accompanied by a decline in citric acid (Senter et al., 1991). Succinic, fumaric, isocitric, ascorbic, gallic and quinic acids have also been identified (Daood et al., 1992). The polymerisation of tannin during maturation of PVNA cultivars is evidently due to the production of ethanol and acetaldehyde by the seeds (Yonemori and Tomana, 1983), but in PCNA cultivars the early decline in soluble tannin is as yet unexplained, although the different tannin composition (Suzuki et al., 2005) is probably involved. Tannin polymerisation also accompanies maturation of astringent cultivars, but at values of around 1% at maturity, the fruit are still highly astringent (Del Bubba et al., 2009; Taira, 1996). A possible explanation for this decline in soluble tannin might be the formation of a glycoside with soluble sugars, proposed to occur during treatment with CO2 (Ittah, 1993). The constant concentration of total sugars maintained when fruit growth ceases might indicate that part of the products of increased invertase activity interact with the soluble tannin. Fruit softening is characteristic of maturation for many fruit species and a measure of firmness can be used as an index of maturity, as a criterion for when to harvest. In general, this is also true for many persimmon cultivars (Salvador et al., 2006). However, with a number of cultivars, fruit firmness as measured with a penetrometer (Magness-Taylor) has been found to be less related to maturity than is the Hunter a colour (Del Bubba et al., 2009; Forbus et al., 1991). Other modes of assessing firmness, such as an impact (Sinclair IQ Firmness Tester) or acoustic (Aweta Firmness Sensor) response, have been found to correlate better with perceived ripeness or postharvest keeping quality. 9.3.2 Phytonutrients Phytonutrients in persimmon include, in addition to the sugars, vitamins and fibre content characteristic of most fruit, large amounts of condensed tannins, polyphenols and carotenoids (Gorinstein et al., 2000), which contribute to the high antioxidative potential of these fruit. High molecular weight tannins have a greater antioxidative activity than low molecular weight tannins (Gu et al., 2008; Kondo et al., 2004), but the effect of removing astringency on antioxidative activity is not known. Maturation and ripening are associated with a reduction in polyphenol content, which might lead to a reduced antioxidant potential. Conversely, the increase in the carotenoid content associated with ripening is likely to raise it. Although varietal differences have not generally been addressed, non-astringent cultivars were found to have higher levels of vitamins A and C than astringent cultivars (Homnava et al., 1990).

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9.3.4 Taste Persimmon overall has a subtle taste with little or no acidity and the aroma is not strong compared with that of many fruit species. Fruit with good sun exposure will tend to have best flavour (higher SSC and more volatiles/flavour). The two most important taste aspects tend to be sweetness and astringency. Higher levels of sweetness are generally preferred by consumers, and warmer growing environments will result in higher SSC content (up to or above 20%; Cristosto, 2004), while fruit in cooler environments may struggle to achieve an average of even 15% (Mowat and Collins, 2000). In astringent-type persimmons under prolonged MA storage that enables loss of astringency, flavour can become bland if CO2 levels in storage are low, or develop off-flavours if CO2 is too high. In non-astringent persimmons, a possible negative attribute that can affect repeat sales is that of ‘residual astringency’. The key factor that affects this appears to be the fruit temperature during development (Mowat and Collins, 2000), particularly during the period of 10–14 weeks after full bloom (Chujo, 1982; Jackman and Woolf, unpublished data).

9.4

Preharvest factors affecting postharvest fruit quality

9.4.1 Minerals – nutrition Studies conducted with a non-astringent cultivar (‘Fuyu’ in New Zealand) and with an astringent cultivar (‘Triumph’ in Israel) have not indicated any apparent postharvest effects of mineral status of the fruit at harvest (although the New Zealand study did not include nitrogen in the analysis). This could, however, be the result of specific environmental effects on the mineral composition and/or physiology of the fruit, since the same cultivars grown in Brazil, Spain and Australia were found to respond to preharvest calcium by producing firmer or higher quality fruit (Agusti et al., 2004; Ferri et al., 2008) and Redpath et al. (2009) found a correlation of leaf calcium content and postharvest softening rate. The keeping quality of coolstored ‘Fuyu’ was improved by preharvest sprays of calcium chloride or nitrate (0.5%) and boron (0.3%), because of reduction of skin cracks, and browning (Ferri et al., 2008). Application of 2% Ca(NO3)2 to astringent ‘Triumph’ fruit before colour break retarded colour development, fruit softening and ethylene production and reduced postharvest fruit softening and deterioration. However, the incidence of soft-blossomend fruit, which appeared to be related to low calcium levels, was not affected by orchard sprays of calcium nitrate throughout the growing season (Ben-Arie et al., 2008). Repeated heavy foliar application of calcium sprays in New Zealand was not found to reduce chilling injury following storage (Woolf and colleagues, unpublished data). Convincing data as to the ability of cultural practices to affect the mineral composition and postharvest quality of persimmon fruit are scarce. 9.4.2 Plant growth regulators The objective of preharvest application of plant growth regulators is to control fruit maturation or improve postharvest ripening and quality. Advanced maturation

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has been achieved by applying paclobutrazol (a gibberellin synthesis inhibitor), abscisic acid, ethychlozate or methyl jasmonate (presumably by stimulation of ethylene synthesis) and ethephon (an ethylene-releasing compound). These treatments enable earlier harvesting because of enhanced growth rate and fruit colouration, but may also accelerate the postharvest softening rate. This practice may be useful where limited storage/shelf life is acceptable (i.e. early season local or airfreight export markets). Paclobutrazol has been applied commercially with success, care being taken not to delay harvest from treated trees. It is applied to the soil in the spring, immediately retarding vegetative growth and the effect can last for 2–3 years. Conversely, delayed maturation is achieved by spraying GA3 (30–50 mg L−1), 10–20 days before harvest. Colour development and fruit softening are retarded, but the chief advantage of this treatment is an extended storage and shelf life. It is necessary to determine the optimum dose for each cultivar, since, although increasing the dose enhances the effect, it may be detrimental to fruit size and especially to the return bloom in the subsequent year. A similar effect can be obtained by spraying the cytokinin CPPU at a low concentration (2–10 mg L−1, ten days after full bloom (DAFB)). Combined with girdling, final fruit weight could be improved (Hamada et al., 2008). However, to the best of our knowledge, this treatment has yet to be adopted commercially. The delayed maturation induced by GA3 has been shown to increase the carbohydrate content, chiefly cellulose, together with reduced activity of PG and cellulase during fruit softening (Ben-Arie et al., 1996, 1997). It also reduces the rate of fruit respiration (Nakano et al., 1997) and the sensitivity of the fruit to ethylene ten-fold. 9.4.3 Climate and environment The persimmon is generally regarded as a crop that is highly adaptable to many soil types and conditions, as well as to a wide range of climatic conditions. Sunburn and abrasions caused by wind are easily recognised and can be dealt with to some extent, using appropriate training methods, wind-breaks (trees or artificial netting) and other methods of protection, such as net-houses or covering. Astringency is the most obvious of the fruit characteristics that is affected by climatic conditions during fruit development. As noted above, non-astringent cultivars require warmer conditions than astringent cultivars for maturation and may not lose their astringency when grown under relatively low temperatures (Mowat et al., 1997). On the other hand, excessively high temperatures may be detrimental to fruit size, partly because of accelerated maturation. Fruit can be susceptible to sunburn in mid-summer, particularly following pruning or leaf thinning. However, although net covering in a hot climate reduced the daily temperature and somewhat delayed maturation (chiefly because of a delay in colour development), it did not increase fruit size, which is positively affected only by increasing irrigation in both open and net-covered orchards. Nonetheless, net covering produced higher quality fruit because of reduced sunburn and wind abrasions, in addition to reduced bird damage (Ben-Arie et al., 2008).

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Canopy management contributes significantly to overall fruit quality. In a review of Australian persimmon management practices, Nissen et al. (2003) reported that in Australian orchards, trellised trees produce higher yields of marketable fruit than do other training systems. Trellising increased planting density, improved light interception, and structures that stabilised the tree significantly reduced fruit blemishes. Light exposure of the fruit has an effect on fruit temperature (Mowat, 2003). In Japan, Takano et al. (1991) reported that the level of light exposure had a greater effect on fruit weight, colour and soluble solids content than did crop load. Exposed fruit had higher colour and lower soluble tannins than unexposed fruit in the mid-canopy in New Zealand ‘Fuyu’ (Mowat, unpublished data). Specific leaf weight is useful as an indicator of light conditions in ‘Fuyu’ canopies in New Zealand orchards, where higher values were correlated with improved fruit quality (Mowat, 2003). 9.4.4 Calyx separation In some cultivars and growing conditions, calyx separation or ‘calyx cavity’ develops (Glucina, 1987). This disorder occurs late in the season, during the final phase of the double sigmoidal growth curve. It is thought that the fruit expands faster than the calyx, and this results in the flesh separating from the calyx tissue, resulting in potentially large gaps (up to 5 mm or more), which may even encircle the whole calyx. This leads to more rapid softening of non-stored persimmons and increased levels of chilling injury in stored fruit. Thus, commercial recommendations are to remove these fruit during packing, although detection of all but the most severe disorders can be difficult. These cavities also provide a refuge for insects such as caterpillars, mealybugs and even earwigs. The problem is more common in ‘Fuyu’, but less so in some other cultivars such as ‘Triumph’ and ‘Suruga’. Larger fruit are more likely to have calyx separation, probably because of the greater fruit expansion. It is considered to occur more on young trees, and generally declines after about 15 years. 9.4.5 Skin cracking/black blotch An additional practical and economic challenge to persimmons is the propensity for the occurrence of large or small cracking (‘crazing’) of the skin. This can occur as ‘ring cracks’ around the fruit, most often at the distal end, or as discrete brown/black patches on the skin (‘black stain’, Fumuro and Gamo, 2001; or ‘black blotch’, Woolf et al., 2008). Depending on market requirements, these may or may not be acceptable. Large cracks are evident at harvest, but smaller cracks may only become evident after harvest, or during storage, although the actual cracking is most likely to have occurred preharvest during the final stage of fruit growth (Chujo et al., 1982; Woolf et al., 2008). Factors that may increase this problem are rainfall or presence of seeds, both of which lead to increased fruit expansion, presumably placing more stress on the skin. The resulting cracks may be visible to the naked eye or microscopic (Woolf et al., 2008), and it is the latter

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ones that are likely to blacken after harvest or during storage. Thus, orchard management systems that avoid damage to the fruit skin (e.g. avoiding leaf contact with fruit; Woolf et al., 2008) or fruit bagging prior to harvest (Fumuro and Gamo, 2001) ensure development of continuous wax layers that will improve packout and final fruit quality.

9.5

Postharvest handling factors affecting fruit quality

Although there are significant differences between countries and cultivars, the maximum storage life of persimmons is generally in the order of 12–16 weeks. Typically this will only be achieved by use of a combination of treatments (such as optimised temperature, 1-MCP and MA storage) to overcome softening and/or chilling injury problems. The final limitation to long-term storage will typically be external quality due to skin browning, excessive softening or disease incidence. 9.5.1 Temperature management The standard recommended storage temperature is 0 °C (Crisosto, 2004; MacRae, 1987), and some countries recommend even lower temperatures such as −1 °C (Israel). Higher temperatures (3–8 °C) lead to increased chilling injury in ‘Fuyu’ (Collins and Tisdell, 1995), and at 5–15 °C for other cultivars (Crisosto, 2004). Since maintaining temperatures around or below 0 °C is important, determining the freezing point can be an important step in commercial temperature management. Crisosto (2004) suggests a freezing point of −2 °C and we have found freezing points as high as −1.25 °C (New Zealand) or as low as −3.2 °C (Israel), the variation being probably attributable to SSC level. 9.5.2 Physical damage An important problem with persimmons is that any puncturing or damage to the skin results in blackening that is very evident to consumers on the orange-red skin. Aside from the obvious deleterious visual effect, such damage can promote rots during storage. In some cultivars, bruising appears not to be important (‘Fuyu’ in New Zealand), but in other cultivars (‘Triumph’), careful handling at and after harvest is of major importance, to avoid the occurrence of blackened tissues beneath the skin. Fruit that have been treated with CO2 to remove astringency are especially susceptible. Therefore, the commercial recommendation is to pack the fruit prior to de-astringency treatment. 9.5.3 Water loss Unlike many crops, weight loss is not a key factor for persimmons, probably because little water loss occurs through the skin (Perez-Munuera et al., 2009), but

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Fig. 9.1 The relationship between weight loss, fruit shrivel and Alternaria decay development on ‘Triumph’ persimmons, after 14 weeks storage at −1 °C and RH levels ranging from 70 to 100%.

low RH can cause fruit shrivelling. For example, ‘Triumph’ fruit showed a linear relationship between increase in weight loss during storage and RH (Prusky et al., 1981), and the percentage of shrivelled fruit was unacceptable above 5% loss in weight, which occurred at 85% RH after 14 weeks at −1 °C (Ben-Arie and Prusky, unpublished data, Fig. 9.1). From the point of view of decay development, increased weight loss was accompanied by reduced infected area, so that optimum quality was achieved with 3–5% weight loss at 85–90% RH. However, maintenance of 90 to 95% relative humidity (RH) during storage has also been recommended (Crisosto, 2004). In terms of weight loss from the fruit, both before and during storage, no significant impacts on chilling injury have been noted for ‘Fuyu’ (Woolf, unpublished data). Softening of the tissue beneath and around the calyx after prolonged storage could possibly arise indirectly from water loss by the calyx lobe, which has been shown to trigger ethylene production (Nakano et al., 2002, 2003), as described above. Where there are cracks or punctures of the skin, water loss occurs more rapidly during storage and shelf life, and thus some shrivelling and sinking of tissue can become evident. In non-damaged fruit, the key area where weight loss may be commercially important is in the appearance of the calyx, where drying and browning of the green leafy tissue may affect retailer and consumer perceptions of freshness. 9.5.4 Atmosphere Controlled atmosphere (CA) storage Storage under low O2 of 2 to 5% delays ripening, and CO2 at 5 to 10% slows softening and can reduce chilling injury (CI) symptoms (Crisosto, 2004; Burmeister et al., 1997; Tanaka et al., 1971). The upper tolerable concentration of CO2 appears to be between 10% (Crisosto, 2004) and 20% (Haginuma, 1972),

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although there clearly are cultivar differences. Excessive exposure can result in skin browning and/or flesh browning beginning in the fruit centre. CA storage of the astringent ‘Triumph’ has the triple benefit of delaying fruit softening, retarding decay development and, if extended beyond three months, removing astringency (Guelfat-Reich and Ben-Arie, 1976; Guelfat-Reich et al., 1975). The atmosphere required to achieve these advantages is 1.0–1.5% O2 and 1.5–3.0% CO2. At higher CO2 levels, Alternaria decay control is improved, but fruit softening is enhanced and at >5% CO2, internal flesh browning occurs. The disadvantage of long-term CA storage (exceeding three months) is the very short subsequent shelf-life, due to rapid fruit softening. Below 1.0% O2, ethanol and acetaldehyde accumulation are excessive and off-flavours develop after three months at −1 °C, although astringency is completely removed (Ben-Arie, unpublished data). ‘Rojo Brillante’ storage life was extended to 30 days at 15 °C under CA (3% O2, 97% N2) because of delayed softening, thus circumventing CI, also with removal of astringency (Arnal et al., 2008). In this case, increased CO2 was of no additional benefit. Modified atmosphere storage Use of modified atmosphere (MA, or MAP) is common commercial practice in Korea, Japan and New Zealand (Kim and Lee, 2005; Kawada, 1982; MacRae, 1987). Fruit are heat-sealed in a 60-μm polyethylene (PE) bag, which generates an atmosphere of approximately 0.5–1.5% O2 and 4–8% CO2 (MacRae, 1987; Kim and Lee, 2005) and this delays and ameliorates CI symptoms, but does not eliminate them. Fruit of an entire tray (e.g. 4–10 kg) tend to be stored in one bag, but individual fruit-bags, or fruit in lots of 3–5, may also be used in Japan. An additional benefit of the MA bag system is that fruit are maintained in the MA environment during storage at the packhouse facility, during shipment/ transport (e.g. seafreight container), and during the steps through the wholesale and retail chain. This has a range of advantages other than the continual MA atmosphere, including reduced temperature fluctuation, avoiding condensation and improved food safety. A key commercial challenge is the reliability of bagsealing, where even one pin-prick sized hole can compromise the MA atmosphere and result in chilling injury development. In addition, once sealed in the MA bag, exposure to higher temperatures than the target storage temperature may result in reduced O2 and elevated CO2 concentrations, which may damage fruit (‘glassy ring’ and calyx abscission). Ethylene Persimmons are climacteric and sensitive to ethylene and thus exposure to ethylene results in increased rates of softening and reduced storage and shelf life, and therefore marketability (Takata, 1983; Krammes et al., 2005; Park and Lee, 2005; Besada et al., 2010). Besada et al. (2010) examined the effect of a wide range of concentrations and durations of ethylene exposure on shelf and storage life of ‘Fuyu’ in simulated air (non-stored) and seafreight (MA-stored) commercial scenarios. Exposure of fruit at 20 °C for one day, at even 0.2 μL L−1, resulted in

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an increased softening rate (non-stored fruit). If fruit were stored under MA for seven weeks after treatment, chilling injury was increased with ≥1 μL L−1 for 1 d, and slightly increased with ≤0.5 μL L−1 for 2 d. However, ethylene exposure of MA packed fruit during storage (0 °C), at either the beginning or end of the storage period, had either little or no influence on chilling injury (even with exposure times of seven days at 10 μL L−1). The lack of response of ‘Fuyu’ persimmons at low temperature is supported by results with ‘Triumph’, which (although this cultivar is not sensitive to CI), can be stored at −1 °C with ethylene levels up to 5 μL L−1, without any softening effect. Other treatments that will ameliorate the effects of exogenous ethylene are 1-MCP treatment. Krammes et al. (2005) showed that fruit treated with 1-MCP (0.1 and 1.0 μL L−1) were less responsive to even continuous exposure to ethylene (0.1 or 3 μL L−1) at 23 °C. Thus, although eliminating ethylene exposure before storage is critical, exposure during storage may be less important. However, Neuwald et al. (2009) reported benefits of ethylene scrubbing in terms of softening and skin browning under long-stored MA conditions. Thus, clearly commercial best practice is to minimise ethylene concentrations during storage. Anoxic tolerance of persimmons A remarkable characteristic of persimmons is their ability to tolerate nearcomplete anoxia (Tanaka et al., 1971). Storage of persimmons in flowing nitrogen (<0.1% O2) at 0 °C has been shown to almost completely eliminate chilling injury in storage for up to eight weeks (Forbes, Ball and Woolf, unpublished), although skin browning problems were sometimes observed (Burmeister et al., 1997). In addition, we found that chilling injury could be minimised (<20%) by storing fruit already packed in MA bags in a low O2 environment (<0.2%) for six weeks, then continuing to store the fruit in MA bags in air for a further three weeks while control (standard MA-stored) fruit had >80% chilling injury (Woolf, unpublished data). In general, we have found that storage under complete anoxia for more than nine weeks results in severe external damage (skin browning and pitting). Interestingly, for ‘Fuyu’ in New Zealand, this period of storage also appears to be a significant cut-off point from both pathology and physiology perspectives, with rots and skin pitting disorders increasing significantly (for example when 1-MCP treatment has minimised chilling injury disorders). 9.5.5 Removal of astringency Currently, three methods for the removal of astringency are in use: on-tree treatment with ethanol, postharvest ethanol application, and high CO2 treatment. Only in a few instances have comparisons been drawn between them (Taira et al., 1992, 1987; Yamada et al., 2002). On-tree removal of astringency with ethanol was developed and has been commercially adopted in Japan, where the higher prices that are paid for the resultant dark-fleshed fruit can presumably warrant the labour costs involved in bagging the fruit and applying the treatment. Physiologically, the

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resultant non-astringent fruit differ from those of other methods. This is evidenced by the reduced recurrence of astringency in on-tree ethanol-treated fruit, compared with postharvest-treated fruit, which occurs when the non-astringent fruit is subjected to heating. Both this phenomenon and the browning of the flesh, similar to that accompanying natural loss of astringency in tissues surrounding the seeds in PVA cultivars, suggest that the loss of astringency occurring in PVNA and in fully ripe astringent cultivars that lose their astringency when soft, is biochemically different from that occurring during other methods for de-astringency. Postharvest ethanol treatment, also popular in Japan, involves spraying packed fruit with 35% ethanol. The disadvantages of this relatively simple method are the extensive time required to achieve fully non-astringent fruit and accelerated fruit softening, presumably a result of the enhanced production of ethylene (Kato, 1984). However, when fruit were treated at 30 °C, tannin polymerisation was more rapid and softening was delayed. Drawbacks in this case are peel discolouration and inferior colour development, due to inhibited chlorophyll degradation and carotenoid biosynthesis. These difficulties can be overcome by applying a low dose of ethylene (3–5 μL L−1) following the ethanol treatment at 30 °C (Kato, 1990). The method was tested with success in large-scale trials, which produced fruit of superior quality (Kato, 1987). Postharvest anoxia, achieved by creating a vacuum or by replacing air with either nitrogen or CO2, has been found to be effective for removal of persimmon astringency (for all types other than PCNA), but there are differences both in the rate of the process and in their effects on fruit quality. With CO2 treatment, the reduction in soluble tannin is the most rapid, because of the higher levels of acetaldehyde that are produced in comparison with either nitrogen (Arnal and Del Rio, 2003; Pesis and Ben-Arie, 1984) or vacuum (Pesis et al., 1986). The more rapid and greater accumulation of acetaldehyde in a CO2 atmosphere was explained by its incorporation into malate, leading more directly to acetaldehyde production (Pesis and Ben-Arie, 1986). However, excess acetaldehyde can be detrimental to fruit quality and treatment with high CO2 may result in flesh browning, which does not occur in fruit treated with nitrogen. Removal of astringency has generally been shown to be more efficient when CO2 treatment is applied before cool storage, but because of its softening effect, the industry often prefers to treat the fruit after storage. ‘Rojo Brillante’ is an exception, in that prolonging its storage at 15 °C results in a very notable loss of effectiveness with post-storage treatment, because of a reduced ability for acetaldehyde production. This has been attributed to ultra-structural changes in the cell wall that progressively cause a blocking of the intercellular spaces with soluble and insoluble material, which presumably interferes with the enzymatic process (Salvador et al., 2008). During artificial loss of astringency, the proposed mode of action is insolubilisation of tannin by formation of a complex with accumulated acetaldehyde (Matsuo and Itoo, 1982). However, there have been some exceptions for ethanol-treated fruit (Fukushima et al., 1991; Taira et al., 1992). This could be related to the inability of certain cultivars to convert ethanol to acetaldehyde in air. Coagulated tannins

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following artificial removal of astringency differ from insoluble tannins in untreated fruit (Oshida et al., 1996), indicating that different modes of de-astringency probably occur (Ozawa et al., 1987). Indeed, it is unlikely that acetaldehyde accumulation accompanies the natural loss of astringency that occurs when astringent cultivars become very soft or when immature non-astringent cultivars lose their astringency before maturation and ripening. The mechanism of tannin precipitation in such cases might well be by the formation of a complex between soluble tannin and soluble pectin produced during ripening (Ozawa et al., 1987; Taira et al., 1997). Additional support for this theory can be concluded from the recurrence of astringency, which occurs when CO2-treated fruit are heated or exposed to high acidity (Ben-Arie and Sonego, 1993), but does not occur in fruit that have become naturally non-astringent. The polymerisation of the tannin in each situation is evidently of a different nature, with different bonding between molecules. This area requires further elucidation.

9.6

Physiological disorders

Persimmons have a range of external disorders, most of them not evident until fruit are stored for long durations (>8–10 weeks), and generally the key disorders are physiological rather than pathological. The most important internal disorder of persimmons is chilling injury resulting from low temperature storage. 9.6.1 Chilling injury This primary disorder of persimmons is manifest as development of a gel-like consistency in the flesh, with concomitant reduction in fruit firmness and development of a translucent deep red colour (MacRae, 1987; Plate XVII in the colour section). Fruit tissue exhibits classic mealiness and loss of free juice, and a chlorine-like off-odour. Typically of CI in other fruit systems, the full expression of CI is not evident until after removal from coolstore. However, where CI is very severe, a dark ‘star’ can be seen around the distal end of the fruit during storage. Chilling injury expression generally occurs about three days after removal from storage, although in severely damaged fruit, softening and gelling can occur in as little as one day. It is interesting that there appears to be significant variation in CI response of fruit from different countries to cool storage. For example, classic CI symptoms (gelling and loss of free juice) are seen in ‘Fuyu’ in New Zealand and in ‘Rojo Brillante’ in Spain, but not in ‘Fuyu’ in Korea or Israel. Expression of CI is associated with a burst of ethylene production on removal from storage (MacRae, 1987). Significantly, 1-MCP (a potent inhibitor of ethylene action that binds to the ethylene receptor site and applied commercially as SmartFreshSM) improves fruit storage by reduction of CI symptoms (Brackman et al., 2004; Kim and Lee, 2005; Park and Lee, 2005; Salvador et al., 2004). From a biochemical perspective, Grant et al. (1992) examined the cell wall metabolism of

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‘Fuyu’ persimmons and showed that chilling-injured fruit passed through the ripening changes more rapidly than non-stored fruit. However, CI was associated with higher molecular mass of solubilised polymers, and a higher proportion of neutral sugars than fruit ripened normally. In addition, CI resulted in loss of neutral sugars (characteristically associated with hemicelluloses) from the insoluble cell wall material and this was not observed in normally ripened fruit. There was a net increase in the insoluble cell wall material during storage. Woolf et al. (1997) examined the effect of hot air treatments (which can reduce CI) on cell wall metabolism and verified much of the work of Grant et al. (1992), but also showed an increase in viscosity of cell wall material in chilling injured fruit (which was reduced by heat treatment), and found that chilling injury resulted in solubilisation of a polyuronide fraction, which possessed a higher average molecular mass than polyuronide solubilised during normal ripening. Thus, CI (gelling) is related to polyuronide release from the cell wall during storage and a lack of subsequent degradation. 9.6.2

Other physiological disorders

Skin browning The key external postharvest disorder is skin browning, generally observed as large, diffuse areas of browning or blackening of the skin (Shin et al., 1994; Woolf et al., 2008). This disorder has proven to be a key challenge to long-term storage in Korea (e.g. 14 weeks; Shin et al., 1994). Browning appears to be related to high nitrogen (preharvest), and can be reduced by CA, MA and antioxidant treatment, such as DPA (Shin et al., 1994), or hot water treatments (Lee et al., 2008). Skin spotting In ‘Fuyu’, a disorder that occurs in long-stored fruit is skin spotting, which is expressed as black ‘pinpricks’ on the skin (these do not increase in size – as pathological disorders would). This disorder is probably due to skin integrity issues and can be reduced by hot water drenches (Woolf et al., 2008). A similar, but possibly not identical, disorder occurring on ‘Fuyu’, was controlled using MA (Ben-Arie and Zutkhi, 1992).

9.7

Pathological disorders

Persimmons have relatively few pathological issues postharvest compared with many other crops. A key limitation to control of many diseases is that the usual copper formulations – widely used in most horticultural crops as a preharvest protective fungicide – cannot be applied since they are phytotoxic for persimmon fruit. 9.7.1 Alternaria This fungus is the predominant postharvest pathogen of persimmon fruit in most cultivation regions. It causes a black spot disease (BSD) and has two manifestations

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– beneath the calyx lobe and on the exposed areas of the fruit, each of which has a different phenology. Disease development beneath the calyx may occur in the orchard as a result of mealybug injury or skin cracks due to excessive rain, and is visible at harvest upon lifting the calyx. Such infections develop further during storage at a rate dependent on storage conditions (temperature and RH). BSD development on the exposed area of the fruit is a result of latent infections occurring in the orchard, which develop slowly during cool storage, with symptoms generally appearing only after two or more months. The incidence of orchard infection and the extent of postharvest disease development are both significantly affected by relative humidity levels during fruit development and in storage, respectively. An effective method to control BSD has not yet been developed, but there are a few control measures that are known to reduce disease incidence. Multiple fungicide sprays throughout the growing season have been shown to reduce the extent of latent infections and the subsequent disease development on exposed areas of the fruit in storage, but decay beneath the calyx remains unaffected. To reduce the incidence of decay in this area, fungicides can be added to the preharvest sprays of GA3, which maintains the angle between the fruit and the calyx in an erect position during ripening. In this manner, the fungicide is able to penetrate the region susceptible to infection. Iprodione was found to be quite effective when the disease potential was not high. Three sprays of 20 μg mL−1 GA3, beginning a month before harvest, were more effective than a single spray (Perez et al., 1995). In addition, GA3 alone increases the fruit’s natural resistance by affecting its cell wall structure, so that BSD development from latent infections is reduced. A host-pathogen interaction is probably also involved, resulting in the reduced ability of the fungus to produce endo-1-4-β-glucanase in gibberellin-treated fruit (Eshel et al., 2000). The most effective postharvest treatment so far permitted is a dip in Troclosene-Na (dichloroisocyanuric acid sodium salt; Medentech Ltd., Loch Garman, Ireland), a chlorine-based product, applied commercially in Israel at 500 mg L−1 for 30 seconds (Prusky et al., 2006). This is chiefly a surface sterilisation and its effect is lost during extended storage periods or during subsequent shelf life. A repeated post-storage treatment has been reported to protect the fruit during shelf life. Storage atmosphere affects disease development, which can be dramatically reduced in CA or even more so in MA, in spite of the high RH. This is due chiefly to CO2 levels above 5%, but acetaldehyde accumulation may also contribute to the inhibition of fungal growth. 9.7.2 Botrytis This rot can be a significant problem because, like Alternaria, it can grow and develop during cold storage and thus result in large lesions (>10 mm diam.), evident to the retailer at removal from storage. Rots caused by Botrytis cinerea, a wound parasite, can develop at three different sites on the fruit (Woolf et al., 2008). ‘Apex punctures’ that occur during harvest or handling due to puncturing of the skin by the ‘apex spike’ (the hard structure present at the stylar end of the fruit), enable fungal penetration. The apex spike itself can become infected

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(during flowering) and these infections develop into rots during storage. ‘Calyx rots’ (around the calyx end of the fruit) occur sporadically and we have also found these to be caused by Botrytis cinerea. Keeping the amount of Botrytis inoculum low in orchards during the growing season is key to reducing the potential for storage rots. In addition to the postharvest impact of Botrytis, infection of the petal tissue at flowering can lead to cosmetic marking of the skin that causes rejection at packing. Postharvest treatments using a hot water drench at approximately 55 °C have been shown to be effective for control of postharvest diseases in long-stored ‘Fuyu’ (Woolf et al., 2008), and similar treatments (hot water brushing) are effective on ‘Triumph’ (Ben-Arie, pers. comm.). Other causes of decay in persimmons according to Crisosto (2004) and Palou et al. (2009) are Cladosporium, Colletotrichum, Mucor, Penicillium, Phoma and Rhizopus. Many of these infections take advantage of wounding or microscopic damage to the skin (e.g. Mucor, Kwong et al., 2004).

9.8

Insect pests and their control

Insects are a significant problem for persimmons, which can host fruit fly in the subtropics, and are readily infested in temperate environments by a wide range of other pests, such as caterpillars, thrips, mealybug and scale. There is also a wide range of insects that cause significant preharvest problems, but may not be a significant problem from a postharvest perspective (e.g. various stink bugs: Halyomorpha halys, Plautia crossota stali, Riptortus clavatus, Son et al., 2009; and cut worms, Choi et al., 2008). 9.8.1 Fruit fly Fruit flies are important fruit pests that attack several cultivated species of high commercial value in subtropical and tropical areas of the world. Three species are prevalent on persimmon in different growing regions: the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), the Mexican fruit fly, Anastrepha ludens (Loew) and the oriental fruit fly, Bactrocera dorsalis (Wendel). Because of the continuity of hosts and the relatively short life cycle of the pests, their control is difficult and fruitgrowing regions that are infected have developed regional protocols for dealing with the problem. These include detailed recommendations for sanitation, weekly monitoring, pesticide-bait spray programmes, release of sterilised males and traps to kill. Sanitation recommendations include total removal and disposal of fruit from the trees and orchard ground after harvest. Monitoring with traps containing the attractant trimedlure begins around the time of colour break. Bait sprays are frequently applied from aircraft and supplemented with spot spraying in the orchards. In recent years an effective and environmentally friendly insecticide, Conserve®-SC (Spinosad; Dow AgroSciences), has replaced the organophosphate malathion as a bait spray (Stark et al., 2004). The dispersal of sterilised males is increasing and new traps to attract

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and kill have been developed. In Hawaii a multi-lure trap (three attractants) with soapy water or sticky boards to kill, and in Israel two traps – Biofeed® and Protect® – based on attractant yellow boards, bait and Spinosad, are available. In the event that a combination of all treatments is not sufficiently effective and larvae are found in infected fruit, cover sprays with the organophosphate diviphos are recommended to achieve eradication (Thomas et al., 2007). Quarantine regulations in some persimmon importing countries are very strict, with zero tolerance. Cool storage at below 1 °C for two weeks kills all stages of the fly and is generally suitable for most cultivars. For chilling-sensitive astringent cultivars, it is possible that the high CO2 treatment at a high temperature to remove astringency could also be effective. 9.8.2 Other insects In more temperate environs, the most important pests of persimmon include mealybug (e.g. Pseudococcus longispinus, P. viburni, P. calceolariae and Phenacoccus graminicola) and various leafroller and other caterpillar species (e.g. Ctenopseustis obliquana, C. herana, Cnephasia jactatana, Planotortrix octo, Stathmopoda skelloni, Sperchia intractana and the lightbrown apple moth – Epiphyas postvittana). Postharvest treatments for such species include cold disinfestation and heat treatments either by hot air (Dentener et al., 1996) or hot water (Lee et al., 2008). Other important insects include thrips (e.g. Heliothrips haemorrhoidalis, Nesothrips propinquus) and scale insects (e.g. Hemiberlesia rapax, Hemiberlesia lataniae, Aspidiotus erii, Ceroplastes pseudoceriferus and Phenacoccus aceris). Scale insects can infest fruit or calyx, and where this occurs, it tends to result in an indentation in the fruit. Finally, various mites may also be an issue (e.g. Aceria diospyri, Oribatidae, Tetranychus urticae (TSM), Orthotydeus californicus and O. caudatus). 9.8.3 Passenger or ‘hitchhiker’ pests The issue of ‘passenger’ or ‘hitchhiker’ pests, including spiders, earwigs, centipedes, slaters, and even small snails, poses a problem. They often hide under the calyx or in the calyx cavity (if present). In this location, they are difficult to detect and are well protected from any preharvest insecticides and postharvest treatments (such as brushing). Some packhouses resort to checking under each lobe of the calyx, and use an air gun to remove insects, which is clearly an expensive practice and generally only practicable for very high value markets (such as Japan).

9.9

Postharvest handling practices

9.9.1 Harvest operations Different cultivars require different harvest techniques. For many cultivars (e.g. ‘Fuyu’ and ‘Triumph’), fruit must be cut from the tree using secateurs, leaving the

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calyx attached to the fruit, since hand-pulling can injure the fruit and adjoining stem. However, other cultivars (e.g. ‘Kaki-Tipo’), may be hand-harvested (twisted) from the stem. Another factor that has a significant influence on the harvest technique is that of fruit shape and the location and structure of the ‘apex spike’ (black spike at distal end of the fruit). If the spike is prominent, it is more likely to damage other fruit during handling and packing and in this case fruit must be harvested into single-layer trays (e.g. Italy) or 20-kg crates with three layers (New Zealand) rather than larger harvest bins (350 kg, Israel). The ability to harvest by hand and not use small trays clearly has significant impacts on speed and economics, but enhances the danger of bruising while filling the bins and during transport. 9.9.2 Packinghouse practices Generally persimmons do not require any specific handling procedure other than the usual grading, sizing and packaging, adapted to the marketing outlets. Only fruit harvested into bulk bins are dumped into water to ensure gentle fruit handling. Astringent cultivars have to be treated to remove astringency. The most common method used is exposure to 80% CO2 for one to three days, depending on the cultivar. The preference for this treatment is because of the maintained fruit firmness (relative to ethanol). In Japan, the method has been refined with temperature control, shortening the time required – CTSD (controlled temperature short duration). In Italy, ‘Kaki-Tipo’ is treated with ethylene (>100 μL L−1), in spite of its softening effect, since the response to CO2 is not optimal and that market favours the softer fruit. The treatment is applied at 25–30 °C for 24–36 hours, depending on the stage of maturity, and thereafter temperature is reduced to 15 °C until the desired colour is achieved. Fruit that are intended for storage periods in excess of 8–10 weeks require treatment to inhibit Alternaria black spot development. The recommended treatment in Israel for ‘Triumph’ is a 30-second dip in 500 mg L−1 hypochlorite or Troclosene-Na. 9.9.3 Control of ripening and senescence Using refrigeration to delay persimmon ripening and senescence is limited by chilling injury (CI), which is the decisive factor in choosing the appropriate storage temperature for each cultivar. Thus, the non-susceptible ‘Triumph’ can be stored at −1 °C for four months, ‘Fuyu’ develops CI within two weeks below 8 °C (air-stored), and the highly susceptible ‘Rojo Brillante’ maintains best quality at 15 °C, but only for three to four weeks. CA storage has been shown to be beneficial in retarding both softening and black spot development, but the optimal levels need to be determined for each cultivar. Internal injury is likely to appear at higher CO2 levels, especially under MA conditions, where the build-up of CO2 is controlled by the balance between fruit respiration (affected by temperature) and the selective permeability of the

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package material. Nonetheless, with films of suitable gas transmission, the storage life of ‘Fuyu’ persimmons can be tripled at 1 °C (Cia et al., 2006). The disadvantage of both storage methods is the rapid rate of fruit softening after removal of the fruit to shelf-life conditions. This has been shown to be remediable when CA storage follows 1-MCP treatment. Persimmon fruit respond very well to 1-MCP (commercially applied by AgroFresh as SmartFreshSM) at levels in the range of 0.3–0.6 mg L−1, at both storage and ambient temperatures, either before or after storage. In addition to alleviating CI in ‘Fuyu’ and ‘Rojo Brillante’, when applied before storage at 0 °C, the treatment extends the post-storage shelf life by retarding fruit softening. However, with long-term storage, decay development generally becomes the limiting factor. Hence, there is an advantage in combining 1-MCP pre-storage treatment with CA storage. Irrespective of this, it is convenient to apply 1-MCP in combination with the CO2 treatment to remove astringency (Harima et al., 2003), either before or after storage. Similarly, use of 1-MCP treatment prior to MA storage leads to near elimination of chilling injury for ‘Fuyu’ (Kim and Lee, 2005). This is typically carried out on only a small portion of the crop destined for long-term storage, because of the cost of treatment, additional handling and delays to packing, which generally make its universal use uneconomic. It should be noted that 1-MCP does not solve all physiological disorders, or pathological problems that typically result from storage for more than ten weeks. 9.9.4 Recommended storage and shipping conditions Optimum storage temperature is generally 0 °C, but variation between cultivars exists (e.g. ‘Rojo Brillante’ (see Section 9.5.1 above)). Ethylene scrubbing is generally not used under commercial conditions, but ethylene should be avoided where possible. Some cultivars respond well to MA storage (e.g. ‘Fuyu’) but CA is rarely used commercially (see Sections 9.5.4 and 9.9.3 above).

9.10

Processing

9.10.1 Fresh-cut processing Although there is potential for persimmons to be processed for fresh-cut, either as wedges or slices, there has been little development in this area. This is possibly because of the relative ease of preparation of persimmon fruit for serving and its relatively slow flesh browning in such situations. At 5 °C (a typical storage temperature for fresh-cut products), slices of ‘Fuyu’ have a shelf life of seven days in air, and eight days in a CA (2% O2 + 12% CO2; Wright and Kader, 1997). A longer shelf life can be expected at 0 to 2 °C (Crisosto, 2004). Itamura et al. (2009) found that ‘Saijo’ showed more softening when fruit were cut into vertical wedges rather than horizontal slices, and that fruit cut into small pieces softened the most rapidly. Application of 1-MCP slowed softening, but was not completely effective.

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Use of antioxidants such as sodium ascorbate and cysteine were found to reduce browning of fresh-cut ‘Rojo Brillante’ (Peraz-Gago et al., 2009). 9.10.2 Other processing practices The most common processing of persimmons is that of drying, which has been carried out for many centuries (Testoni, 2002). Typically the skin is removed (by hand or chemically), and the fruit then air-dried. Chinese and Japanese traditionally hang fruit to dry on strings, resulting in a high value product (Sugiura and Taira, 2009). Additional processing include dried powders from purees to prepare traditional sherbets (Cortellino et al., 2009), and, of course as carried out in nearly all cultures, various alcoholic beverages (Khositashvili et al., 2008).

9.11

Conclusions

Persimmon is a challenging fruit to work with and has many unique characteristics. 1-MCP has provided a key tool for elimination of chilling injury and/or softening. Indeed, the reduction in softening and chilling injury in persimmons is something very close to a ‘silver bullet’. However, rots still remain a challenge for long-stored fruit, particularly given the desire for non-chemical solutions. There are also a number of unexplained physiological disorders that appear mainly on the fruit surface after prolonged storage, which will probably gain importance once the application of 1-MCP and effective disease control enable extension of the fruit’s storage life. The issue of residual astringency is a problem in PCNA cultivars, which needs development of a rapid, simple measure of astringency that correlates with human perception. If this tool could be used in the field and/or packhouse, this would be advantageous. There are opportunities to further research the healthfulness of persimmons. To this end, a worldwide industry initiative into funding and co-ordinating this area was made at the recent International Persimmon Symposium in Italy (Wells, 2009).

9.12

References

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Ben-Arie R and Sonego L (1993), ‘Temperature affects astringency removal and recurrence in persimmon’, Journal of Food Science, 58, 1397–1400. Ben-Arie R, Zhou H W, Sonego L and Zutkhi Y (1997), ‘Plant growth regulator effects on the storage and shelf-life of “Triumph” persimmons’, Acta Horticulturae, 436, 243–250. Ben-Arie R, Zilka S, Klein I and Gamrasni D (2008), ‘Persimmon and environment: soil and water management for high quality fruit production’, Advances in Horticultural Science, 22, 286–293. Besada C, Jackman R C, Olsson S and Woolf A B (2010), ‘Response of “Fuyu” persimmon to ethylene exposure before and during storage’, Postharvest Biology and Technology (accepted). Brackman A, de Freitas S T, Pinto J AV (2004), ‘Ripening control with 1- Methylcyclopropene on “Fuyu” persimmon in cold storage and controlled atmosphere’, Rev. Fac. Zootec. Vet. Agro, 11, 123–134. Burmeister D M, Ball S, Green S and Woolf A B (1997), ‘Interaction of hot water and controlled atmosphere storage on quality of “Fuyu” persimmons’, Postharvest Biology and Technology, 12, 71–81. Chang X X, Rao J P, Zhao B and Liu L (2009), ‘Effect of propylene on softening and postharvest cell wall metabolism of persimmon fruit’, Acta Horticulturae, 833, 299–304. Choi S T, Kang S M and Park C G (2008), ‘Integrated and organic production: insect pest management’, Advances in Horticultural Science, 22, 294–300. Chujo T (1982), ‘Studies on the thermal conditions on the growth and quality of fruits of “Fuyu” kaki’, Memoirs of Faculty of Agriculture, Kagawa University. Chujo T, Honma A, and Ashizawa M (1982), ‘Ultrastructural changes of fruit surface of kaki (Diospyros kaki Linn. f.) through developmental phase’, Technical Bulletin Faculty of Agriculture Kagawa University, 33, 95–101. Cia P, Benato E A, Sigrist J M M, Sarantopoulos C, Oliveira L M and Padula M (2006), ‘Modified atmosphere packaging for extending the storage life of “Fuyu” persimmons’, Postharvest Biology and Technology, 42, 228–234. Collins R J and Tisdell J S (1995), ‘The influence of storage time and temperature on chilling injury in “Fuyu” and “Suruga” persimmon (Diospyros kaki L.) grown in subtropical Australia’, Postharvest Biology and Technology, 6, 149–157. Cortellino G, Scalzo R L Testoni, Bertolo G and Maestrelli A (2009), ‘Persimmon puree: a new ingredient to improve technological and health benefits in sherbets’, Acta Horticulturae, 833, 77–82. Crisosto C (2004), ‘Persimmon’. In: KC Gross, CY Wang and M Saltveit (eds), Agriculture Handbook Number 66. The commercial storage of fruits, vegetables, and florist and nursery stocks. Available at: http://www.ba.ars.usda.gov/hb66/ Daood H G, Biacs P, Czinkotai B and Hoschke A (1992), ‘Chromatographic investigation of carotenoids, sugars and organic acids from Diospyros kaki fruits’, Food Chemistry, 45, 151–155. Del Bubba M, Giordani E, Pipucci L, Cincinelli A, Checchini L and Galvan P (2009), ‘Changes in tannins, acorbic acid and sugar content in astringent persimmons during on-tree growth and ripening in response to different postharvest treatments’, Journal of Food Composition and Analysis, 22, 668–677. Dentener P R, Alexander S M, Lester P J, Petry R J, Maindonald J H, and McDonald A M (1996), ‘Hot air treatment for disinfestation of lightbrown apple moth and longtailed mealy bug on persimmons’, Postharvest Biology and Technology, 8, 143–152. Ebert G and Gross J (1985), ‘Carotenoid changes in the peel of ripening persimmon (Diospyros kaki) cv. Triumph’, Phytochemistry, 24, 29–32. Eshel D, Ben-Arie R, Dinoor A and Prusky D (2000), ‘Resistance of gibberellin-treated persimmon fruit to Alternaria alternata arises from the reduced ability of the fungus to produce endo-1,4-glucanase’, Phytopathology, 90, 1256–1262.

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Nakano M, Yonemori K, Sugiura A and Kataoka I (1997), ‘Effect of gibberellic acid and abscisic acid on fruit respiration in relation to final swell and maturation in persimmon’, Acta Horticulturae, 436, 203–214. Nakano R, Inoue S, Kubo Y and Inaba A (2002), ‘Water stress-induced ethylene in the calyx triggers autocatalytic ethylene production and fruit softening in “Tonewase” persimmon grown in a heated plastic-house’, Postharvest Biology and Technology, 25, 293–300. Nakano R, Ogura E, Kubo Y and Inaba A (2003), ‘Ethylene biosynthesis in detached young persimmon fruit is initiated in calyx and modulated by water loss from the fruit’, Plany Physiology, 131, 276–286. Nakano R, Yonemori K and Sugiura A (1998), ‘Fruit respiration for maintaining sink strength during final swell at growth stage III of persimmon fruit’, Journal of Horticultural Science and Biotechnology, 73, 341–346. Neuwald D A, Streif J, Sestari I, Giehl R F H, Weber A and Brackmann A (2009), ‘Quality of “Fuyu” persimmon during modified atmosphere storage’, Acta Horticulturae, 833, 227–238. Niikawa T, Suzuki T, Ozeki T, Kato M and Ikoma Y (2007), ‘Characterisitics of carotenoid accumulation during maturation of the Japanese persimmon “Fuyu” ’, Horticultural Research (Japan), 6, 251–256. Nissen R J, George A P, Collins R J and Broadley R H (2003), ‘A survey of cultivars and management practices in Australian persimmon orchards’, Acta Horticultuae, 601, 179–185. Ortiz G I, Sugaya S, Sekozawa Y, Ito H, Wada K and Gemma H (2006), ‘Expression of 1-aminocyclopropane-1-carboxylate synthase and 1-aminocyclopropane-1-carboxylate oxidase genes during ripening in “Rendaiji” persimmon fruit’, Journal of the Japanese Society for Horticultural Science, 75, 178–184. Oshida M, Yonemori K and Sugiura A (1996), ‘On the nature of coagulated tannins in astringent type persimmon fruit after an artificial treatment of astringency removal’, Postharvest Biology and Technology, 8, 317–327. Ozawa T, Lilley T and Haslam E (1987), ‘Polyphenol interactions: astringency and the loss of astringency in ripening fruit’, Phytochemistry, 26, 2937–2942. Palou L, Montesinos-Herrero A, Guardado A, Besada C and Del Rio MA (2009), ‘Fungi associated with postharvest decay of persimmon in Spain’, Acta Horticulturae, 833, 275–280. Pang J H, Ma B, Sun H J, Ortiz G I, Imanishi S, et al. (2007), ‘Identification and characterization of ethylene receptor homologs expressed during fruit development and ripening in persimmon (Diospyros kaki Thunb.)’, Postharvest Biology and Technology, 44, 195–203. Park Y M and Lee Y J (2005), ‘Ripening responses of “Fuyu” persimmon fruit to exogenous ethylene and subsequent shelf temperature’, Acta Horticulturae, 685, 151–156. Perez A, Ben-Arie R, Dinoor A, Genizi A and Prusky D (1995), ‘Prevention of black spot disease in persimmon fruit by gibberellic acid and iprodione treatments’, Phytopathology, 85, 221–225. Perez-Gago M B, del Rio M A, Argudo C, and Mateos M (2009), ‘Improving shelf life of cut persimmon fruit’, Acta Horticulturae, 833, 245–250. Perez-Munuera I, Quiles A, Larrea V, Arnal L, Besada C and Salvador A (2009), ‘Microstructure of persimmon treated by hot water to alleviate chilling injury’, Acta Horticulturae, 833, 251–256. Pesis E and Ben-Arie R (1984), ‘Involvement of acetaldehyde and ethanol accumulation during induced de-astringency of persimmon fruits’, Journal of Food Science, 49, 896–899. Pesis E and Ben-Arie R (1986), ‘Carbon dioxide assimilation during postharvest removal of astringency from persimmon fruit’, Physiologia Plantarum, 67, 644–648. Pesis E, Levi A and Ben-Arie R (1986), ‘Deastringency of persimmon fruits by creating a modified atmosphere in polyethylene bags’, Journal of Food Science, 51, 1014–1016.

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Plate XVI (Chapter 9) New Zealand persimmon orchard in late autumn. Note leaf colour and late season, highly coloured fruit and the reflective mulch which increases light, particularly in the lower canopy.

Plate XVII (Chapter 9) Photos of a range of chilling injury levels (0 to 5) in ‘Fuyu’ persimmons. From top (0, no chilling injury) to bottom right (5, complete, total gelling).

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10 Pineapple (Ananas comosus L. Merr.) A. Hassan and Z. Othman, Malaysian Agricultural Research and Development Institute (MARDI), Malaysia and J. Siriphanich, Kasetsart University, Kamphang Saen, Thailand

Abstract: The pineapple is the third most important tropical fruit in the world after banana and citrus; the world pineapple production in 2007 was estimated at 21 008 795 tonnes. This chapter discusses various aspects of postharvest biology and technology of pineapple. The chapter is divided into 11 sections covering postharvest physiology, physical and biochemical changes during maturation and ripening, preharvest and postharvest factors affecting quality, physiological disorders, pathological disorders, insect pests and their control, postharvest handling practices, and processing. Key words: Ananas comosus, pineapple, postharvest handling, storage, physiology.

10.1

Introduction

10.1.1 Origin, morphology and structure Pineapple (Ananas comosus L. Merr.) is believed to be originated from South America, in the region encompassing central and southern Brazil, northern Argentina and Paraguay. The fruit had already been domesticated by the native South Americans before the arrival of Christopher Columbus in 1493. Currently, pineapples are grown commercially over a wide range of latitudes from approximately 30° N in the northern hemisphere to 33°58′S in the south (Malezieux et al., 2003). The word ‘pineapple’ was used by the European explorers to describe the fruit, which resembles pinecones. ‘Ananas’, the original name of the fruit, comes from the Tupi word for pine ‘nanas’, and comosus means ‘tufted’ referring to the stem of the fruit (Collins, 1968). The pineapple is an herbaceous perennial plant of the Liliopsidae (monocotyledonous). The adult plant is 1–2 m high and 1–2 m wide, and it is inscribed in the general shape of a spinning top (d’Ecckenbruge and Leal, 2003). The main morphological structures are the stem, the leaves, the peduncle, the

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Morphological structure of pineapple.

multiple fruit, the crown, the shoots and the roots (Fig. 10.1). The multiple fruit is the result from the fusion of individual fruitlets on a single stalk (Rohrbach and Apt, 1986). Multiple flowers, helically arranged along the axis each produce a fleshy fruitlet that becomes pressed against the fruitlets of adjacent flowers, forming what appears to be a single fleshy fruit. Early European experts recognized as many as 48–68 pineapple cultivars and classified them based on spininess, fruit shape and flower colour. Py et al. (1987) classified pineapple into five groups namely Spanish, Queen, Cayenne, Pernambuco and Perolera. 10.1.2 Worldwide importance and economic value Pineapple is the third most important tropical fruit in the international trade after bananas and citrus; the world pineapple production in 2007 was estimated at 21 008 795 tonnes. About 70% of the total production is consumed domestically, whereas 30% is exported. The most important producing country is Thailand producing 2 815 275 tonnes followed by Brazil (2 676 417), Indonesia (2 237 858), Philippines (2 016 462), Costa Rica (1 968 000), China (1 386 811), India (1 308 000), Nigeria (900 000), Mexico (671 131), Vietnam (470 000), Kenya (429 065),

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Colombia (342 014), Venezuela (363 075) and Malaysia (360 000) (FAO, 2009). Successful production is influenced by several factors especially low production cost, and availability of manpower and land resources. Costa Rica is the most important exporting country with an export quantity of 1 353 027 tonnes followed by the Philippines (270 054), Ecuador (99 581), Cote D’Ivoire (96 558), USA (89 269) and Panama (61 210). Other exporting countries include Honduras, Guatemala, Brazil, Mexico, Ghana and Malaysia (FAO, 2009). The USA is the largest pineapple importer totalling 696 820 tonnes in 2007, followed by Belgium (292 499), the Netherlands (200 026), Germany (167 416), Japan (165 794), Italy (142 168), United Kingdom (116 730), Spain (113 182) and Canada (102 064). The European Union is the largest export market for pineapple (FAO, 2009). For a very long time, the world production and marketing of pineapple has been dominated by the Smooth Cayenne both for fresh and processing. However, in 1996 the world’s pineapple fresh fruit industry went through a transformation when the Del Monte Corporation introduced hybrid ‘MD-2’ for the United States and European markets (Bartholomew, 2009). ‘MD-2’, produced from a cross between the PRI hybrids 58–1184 and 59–443 (Chan et al., 2003), is now grown by many companies and growers in the world and believed to be the most important pineapple cultivar for the fresh market. It is being exported to many countries including the United States, Europe, United Kingdom, Japan, Korea, Hong Kong, China, Singapore and the Middle East (Bartholomew, 2009). 10.1.3 Culinary uses and nutritional value Pineapple is produced for both fresh consumption and processing. Pineapple for fresh consumption is marketed in whole or minimally processed form with a short marketable period. Besides being consumed as desserts, fresh pineapple is also eaten as salad where some spices or sauces may be added according to taste preference. Pineapple can be cooked into various forms or used as an ingredient in cooking. Various processed products from pineapple were described by Abd Shukor et al. (1998), Collins (1968) and Dev and Ingel (1982). Fresh pineapple is a good source of carbohydrate, fibre and minerals especially Ca, P, Fe, Na and K. It also contains some vitamins including A, B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B9 (folate) and C (ascorbic acid). The nutritional content is influenced by several factors including varieties, soil, climatic condition, maturity stage and handling. Processing may result in the nutritional components being altered in the final processed products (Tee et al., 1988).

10.2

Fruit development and postharvest physiology

10.2.1 Fruit growth, development and maturation The pineapple fruit and their components, including core, flesh and shell, show similar sigmoid development (Py et al., 1987; Singleton, 1965) and the maturation period of

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fruit is influenced by several factors, including cultivars, climatic condition, altitude and cultural practices. During the maturation period, the increase in fruit weight slows down while the accumulation of dry matter speeds up as well as the soluble solids content. The peduncle itself starts to dry out. At the same time, the quantity of air in the intercellular space as well as in the locule of each fruitlet reduces progressively (Py et al., 1987). When the intercellular space or pocket of air between cells disappears late in the fruit development, the translucency appearance may occur in some cultivars. Because of this development, specific gravity of the fruit increases (Smith, 1984). Artificial flower induction substances such as ethylene and α-naphthaleneacetic acid (NAA) could delay fruit development. NAA at 100 ppm and 2-chloroethylphosphonic acid (CPA) at 200 ppm applied to the developing inflorescence less than 2.5 cm in diameter can delay fruit maturity by one to four weeks, while increasing fruit size by 25% (Bartholomew and Criley, 1983; Gortner, 1969). The Smooth Cayenne normally takes 100–150 days to develop from flowering to maturation with a shorter maturation period in lower altitude and equatorial regions. Pernambuco takes a longer developmental period, while Red Spanish and Queen take shorter time (Py et al., 1987). The first sign of pineapple maturation is around seven weeks before harvest when the development of new leaves in the crown slows down and four weeks later shell colour begins to change (Gortner, 1965). The yellow colour formation at the base of the fruit starts at around 100 days after flowering and this shell colouring is the most common criteria to judge pineapple maturity. In cooler seasons, the yellow shell colour develops well and coincides with the development of flesh colour and translucency of the flesh. However, in warmer periods, pineapple can reach maturity when it is still green, especially in Smooth Cayenne. The flatness of the eye is also used as a maturity indicator in this cultivar, but not in Queen where the eyes are prominent (Py et al., 1987). 10.2.2 Respiration and ethylene production Pineapple is a non-climacteric fruit (Dull et al., 1967) and has a moderate respiration rate around 10 to 20 ml CO2.kg−1.h−1 at 20 °C. Ethylene production rate in pineapple is low, ranging between 9 and 300 nl.kg−1.h−1. However, ethylene production is higher in more mature fruit. Internal ethylene concentration ranged from 80 to 1140 μl. l−1 with lower concentration in the upper part of the fruit (Dull et al., 1967). Cazzonelli et al. (1998) showed that during ripening, the expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase increased by 16 fold, while there was no increase in ACC oxidase. The study shows a significant role of ethylene in the control of pineapple ripening.

10.3

Physical and biochemical changes during maturation and ripening

10.3.1 Colour During maturation, there is no change in both the shell and the flesh colour. As ripening begins, the chlorophyll in the shell degrades resulting in the yellowing of

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the fruit without any increase in carotenoid pigment except late in the senescence stage. During shell yellowing, the flesh also turns from white to yellow in concomitance with accumulation of carotenoids (Gortner, 1965; Py et al., 1987). There is similar change in shell and flesh colour and their chemical components between fruit harvested green and those attached on the plant (Dull et al., 1967).

10.3.2 Texture Pineapple texture changes gradually from firm to soft as the fruit advances in maturity and ripeness. There are some variations in the texture of different groups of pineapple where Smooth Cayenne are fibrous, Red Spanish and Pernambuco are non-fibrous while Queen and Perolera are crispy in texture (Py et al., 1987). In the case of Queen pineapple, the core can also be consumed. These textural variations could be due to the differences in the chemical compositions of the cell wall in different pineapple groups. Textural differences can also be influenced by maturity stage and growing location (Bartolome et al., 1995). Vidal-Valverde et al. (1982) reported that hemicellulose was the major pineapple cell wall component (41.8%) followed by cellulose 33.6 % and pectin 21.2%. Lignin was found to be only 0.05%. Alcohol insoluble solid (AIS) of pineapple fruit declined with their maturity (Singleton and Gortner, 1965; Dull, 1971). The fibre content, a component of the AIS, also increased up to the onset of ripening and then decreased (Dull, 1971). They also reported that a large amount of unaccounted material, probably hemicellulose, increased during maturation and could play a major role in pineapple texture.

10.3.3 Starch Pineapple fruit does not accumulate starch (Py et al., 1987; Dull, 1971) which explains the small changes in chemical composition and taste of the fruit during ripening. The starch content is very low throughout fruit development where the highest value is less than one per cent, achieved 60 days before ripeness (Dull, 1971).

10.3.4 Sugars The major sugar components in pineapple fruits are sucrose, fructose, and glucose (Flath, 1980). During the early stage of fruit development, glucose and fructose are the major sugar component with low content of sucrose. Around six weeks prior to full ripeness, sucrose abruptly accumulates up until harvesting (Chen and Paull, 2000). The accumulation of sugars up until harvesting was suggested to be due to the high activity of the cell wall enzyme, invertase. At harvest, soluble solids content in pineapple varied a great deal depending upon maturity, season, and cultural practices. A variation from 7 to 21% soluble solids content was reported in a study covering three seasons in Australia (Smith, 1988b). Sugar

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continues to accumulate if the fruit remains attached. However, soluble solids declined when the translucent area developed higher than 50 to 60% (Bowden, 1969). After harvest, there is only a small decline in sugar or soluble solids content. High storage and handling temperature enhances the decrease in sugar content (Paull and Rohrbach, 1982). There is a gradient of sugar concentration in an individual fruit where it is highest at the base and decreases towards the top. The difference between the base and the top portions could be up to four per cent. There is also different sugar distribution in a horizontal direction, sugar content is highest in the flesh near the core and decreases outward to the shell. Sugar in the core is slightly lower than that in the flesh nearby (Miller and Hall, 1953). Soluble solids content is the most correlated parameter with eating quality and always used as a quality criterion for selecting fruit suitable for fresh market (Smith, 1988a). Under commercial practice, a minimum soluble solids content requirement of 12% is used in both Hawaii and Australia. 10.3.5 Acids The major non-volatile organic acids are malic and citric, with a ratio of about 1 to 2–3 (Chan et al., 1973). During the first half of fruit development, the acidity remains quite stable at around 0.1–0.3%, and the malic acid content remains low throughout fruit development. Citric acid increases around six weeks to a maximum at 10 days before the fully ripe stage then declines as the fruit becomes more translucent (Singleton and Gortner, 1965). After harvest, the acid content may increase, particularly at temperatures below 20 °C, but at 29 °C and higher, the acid content decreases quickly. At intermediate temperatures, the acid content remains relatively stable (Dull, 1971). At harvest, the acid content can vary between 0.28 to 1.6%, depending on season, growing conditions, maturity stage and cultivar (Py et al., 1987). Acid distribution in individual fruit is reverse to that of sugar; lowest at the bottom and increases towards the top; high in the core, lowest in the flesh and intermediate near the shell (Miller and Hall, 1953). The acid content does not correlate well with the consumer acceptance of fresh fruit. As a result, sugar to acid ratio, which varies from 5.4 to 66.4 in three seasons’ study with Smooth Cayenne, is also not related to consumer acceptance (Smith, 1988b). 10.3.6 Ascorbic acid During the first half of fruit development, ascorbic acid content in pineapple is low then increases as the fruit becomes more mature, but declines later (Singleton and Gortner, 1965). At harvest, the ascorbic acid content varies according to maturity stage. For ‘Mauritius’ pineapple, the ascorbic acid content harvested between 120 to 130 days from flower induction varies from 23 to 40 mg.100−1 g flesh (Abdullah and Rohaya, 1997). The content in an individual fruit also varies and positively correlates with acid content. It is lowest at the bottom, which may be only half of that at the top, while it is intermediate at the middle (Miller and

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Hall, 1953). After harvest, the amount of ascorbic acid increases slightly or remains relatively constant for a few days, but ascorbic acid contents decrease gradually under prolonged storage at low temperature (Paull and Rohrbach, 1982). Upon exposure to higher ambient temperature following low temperature storage, ascorbic acid contents decrease very quickly (Abdullah and Rohaya, 1997; 1983; Abdullah et al., 1985; 1986; 1996). 10.3.7 Phenolic compounds Pineapple contains phenolic compounds, the major contributor to the antioxidant potential besides ascorbic acid (Gardner et al., 2000). The phenolic compounds include p-coumaric acid, ferulic acid, caffeic acid, sinapic acid, p-coumaroyl quinic acid, p-hydroxybenzoic acid, and p-hydroxy benzoic aldehyde (de Simon et al., 1992; van Lelyveld and de Bruyn, 1977). Each phenol, except sinapic acid, increases in concentration in pineapple fruitlets affected by blackheart disorder. 10.3.8 Protein Pineapple, like many other fruits, is very low in protein but contains bromelain, a glycoprotein having protease activity commonly used in the food industry. The amount of bromelain is roughly half of the protein found in pineapple where the content is much less in the fruit than the stem (Heinicke and Gortner, 1957), and it is higher at the top of the fruit and lower in the middle and the base (Miller and Hall, 1953). Bromelain activity remains relatively high during fruit development and declines at the ripening stage (Lodh et al., 1973) along with the total protein content (Gortner and Singleton, 1965). Another enzyme that received much attention in pineapple is polyphenol oxidase (PPO). Its activity is normally low at harvest, but following chilling stress, higher activity is induced (van Lelyveld and de Bruyn, 1977; Teisson et al., 1979b). PPO activity varies between different parts of the fruit at harvest, with significantly higher levels in the skin and crown leaves but negligible in any parts of the fruit pulp (Zhou et al., 2003). PPO activities increase in pineapple fruits affected by blackheart, a low temperature-related physiological disorder (Abdullah et al., 2009), and has also been implicated in black spot infected fruitlets of pineapple caused by Penicillium funiculosum and Fusarium monoliforme (Avallone et al., 2003). Peroxidase is another pineapple enzyme where the activity decreases during fruit development and during storage (Gortner and Singleton, 1965; Teisson et al., 1979b). Most amino acids decline during the development of the fruit, and those found are alanine, aspartic acid, asparagines, glycine and glutamic acid (Flath, 1980; Kermasha et al., 1987). However, aspartic acid is only found in high amounts at the mature stage. Histidine, the sulphur-containing amino acid methionine, and cystine are present in small amounts but increase abruptly during the ripening of the fruit (Gortner and Singleton, 1965).

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10.3.9 Mineral Pineapple contains some minerals including calcium, iron, magnesium, phosphorus, potassium and zinc. Variation in mineral content observed in pineapple could depend on the type of soil where the plants were grown, the water used for irrigation and the fertilizer applied (Flath, 1980). Deficiency of molybdenum may cause high nitrate levels in fruits, which leads to detinning in canned pineapple (Chairidchai, 2000; Chongpraditnun et al., 2000). 10.3.10 Volatile compounds Similar to other fruits, pineapple aroma increases with its maturity and ripening stages. More than 200 compounds have been identified including esters, lactones, aldehydes, ketones, alcohols, carbonyl acids, hydrocarbons, phenol and sulphur compounds. Summer fruit have more volatiles, especially ethyl alcohol and ethyl acetate, than winter fruit. More volatiles are produced as the fruit become more mature on the plant as well as during ripening after harvest (Flath and Forrey, 1970). As pineapple fruit turns from green to yellow, some volatiles increase while others decrease (Umano et al., 1992). Some volatiles are bound with sugar and released during the preparation of pineapple flesh with the reaction of β-glucosidase (Wu et al., 1991). Table 10.1 lists some of the major volatiles found in pineapple. Those with asterisk are identified as major contributors to pineapple aroma. Flavourist had already made available formulas of synthetic chemicals used to imitate pineapple aroma. Among the earlier compounds used are vanillin, n-dodecanal, allyl and amyl esters, maltol, ethyl maltol and isobutylfuryl propionate (Broderick, 1975).

10.4

Preharvest factors affecting fruit quality

10.4.1 Soil Pineapple have been grown on many types of soils including organic peat soil in Malaysia (see Plate XVIII in the colour section between pages 238 and 239); volcanic ash soil in Hawaii, many Caribbean islands and parts of the Philippines; and very sandy soils found in parts of southern Queensland and northern South Africa (Hepton, 2003). Pineapples grown on different types of soil may have different postharvest quality, for example in Malaysia, the pineapple grown on mineral soil is sweeter than those grown on organic peat. However, ‘Josapine’ pineapple grown on mineral soil is more susceptible to bacterial heart rot disease. 10.4.2 Climatic condition Fruit produced in winter in sub-tropical regions is known to be of poor quality as the fruit acidity is high (Bartholomew, 2009). The winter fruits are also subject to developing blackheart, a chilling-related physiological disorder, either in the field or after harvest (Leverington, 1968). Climatic conditions influence the nutritional

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Table 10.1

Major volatiles found in pineapple

Volatiles

References

Odour description

Methyl-3-(methylthio) propanoate*

Berger et al. (1985); Teai and Claude-Lafontaine (2001); Umano et al. (1992) Berger et al. (1985); HaagenSmit et al. (1945); Teai and Claude-Lafontaine (2001); Umano et al. (1992) Ohta et al. (1987); Umano et al. (1992) Ohta et al. (1987); Rodin et al. (1965); Umano et al. (1992) Takeoka et al. (1991); Teai and Claude-Lafontaine (2001) Ohta et al. (1987); Umano et al. (1992) Umano et al. (1992) Berger et al. (1983) Berger et al. (1985) Berger et al. (1985)

Pineapple-like

Ethyl-3-(methylthio) propanoate

3-hydroxy-2-butanone 2,5-dimethyl-4-hydroxy3-(2H) furanone Ethyl-2methylbutanoate* Ethyl acetate* Butane 2, 3 diol diacetate α-patchoulene 1-(E,Z)-3,5-undecatriene 1-(E,Z,Z)-3,5,8undecatriene

Fruity, pineapple-like

Burnt pineapple

Honey-like Fruity, spicy Balsamic, spicy, pinewood Balsamic, spicy, pinewood, more fruity

* Major contributors to pineapple aroma

content of fruit including ascorbic acid (Chan et al., 1973) and the acid content fluctuates markedly and consistently according to the weather variation before harvest, where there is a two-week lag before the effects of the weather factors become obvious. Ascorbic acid content is also influenced by the amount of sunlight received during the development as fruit under strong sunlight contains higher ascorbic acid (Singleton and Gortner, 1965). 10.4.3 Cultural practices Crown removal increases fruit size and the fruit becomes more cylindrical in shape, however, they become subject to sunburn (Py et al., 1987). Chemical application such as 3-chlorophenoxyacetic acid (3-CPA) at the early stage of crown development can reduce crown size and increase fruit size and yield (Bartholomew and Criley, 1983) and the size of the crown itself can be controlled by mechanically removing the apex at least two months before harvest to allow wound healing (Py et al., 1987). The use of 3-CPA for crown control may cause injury to the base of pineapple slips and the crown causing them to be easily detached from the fruit (Abd Shukor et al., 1998). The detached areas serve as entry points for disease causing microorganisms such as Thielaviopsis paradoxa and fruits with detached crowns have shorter storage life than those with the crown intact.

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Postharvest factors affecting quality

10.5.1 Physical damage Like other horticultural commodities, physical damage on pineapple may occur at any point throughout the handling chain right from harvesting until consumption. Physical damages are caused by mechanical factors such as cuts, abrasions, compaction and impact. The damages may appear immediately after the injury took place or in many cases they only become noticeable after some time during handling or marketing. Mechanical damage may affect fruit quality in terms of poor appearance, uneven fruit ripening and shorter storage life. Damaged fruits usually have higher respiration rates and the leakage cell content leads to infection by microorganisms (Paull and Chen, 2003). 10.5.2 Temperature The recommended optimum storage temperature for pineapple is between 7 and 13 °C (Hardenburgh et al., 1986; Paull, 1997). Temperatures lower than the optimum level may induce chilling injury. More mature fruits are more adaptable to lower temperature, but lower storage temperature and a longer storage period may induce acid accumulation. Up to 35% increase in titratable acidity has been found in pineapple stored for ten days at 8 °C. Prolonged exposure to lower temperatures may cause poor organoleptic quality, but under good handling practices, maintenance of the cold chain is necessary as interruptions may cause the development of internal browning, fungal diseases and shorter storage life (Paull, 1997). Exposure to extremely high temperature above 35 °C should be avoided as it may also affect fruit quality. Exposure to high temperature speeds up the deterioration process and increases weight loss due to excessive moisture loss through the fruit surface. Extremely high temperature may result in the shell and crown becoming dry, especially when fruits are transported without refrigeration. 10.5.3 Relative humidity The recommended range of relative humidity (RH) for storage of pineapple is 85–95% (Hardenburgh et al., 1986; Paull and Chen, 2003). Higher RH reduces water loss, which helps maintain the fruit appearance and freshness, while lower RH encourages moisture loss from the surface and affects fruit appearance. Loss of moisture causes physiological weight loss, but a reduction of water loss helps in maintaining the fruit external appearance. Wrapping the fruit in a perforated polyethylene (PE) sleeve helps the maintenance of the fruit external appearance by creating a moisture barrier, which slows down moisture loss. However, storing fruits under very high RH favours the growth of microorganisms on the shell and peduncle. 10.5.4 Atmosphere There is very limited use of controlled or modified atmosphere (CA or MA) for pineapple commercially (Yahia, 1998). The recommended condition is 2–5% O2

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and 5–10% CO2 (Kader, 1992). ‘Mauritius’ pineapple stored for more than three weeks under MA in sealed PE bags at 10 °C are affected by off-odour and off-flavour development (Abdullah et al., 1985), but waxing the fruit and high humidity during cold storage would give equal benefits as demonstrated by atmosphere modification.

10.6

Physiological disorders

10.6.1 Common chilling injury Chilling injury (CI) affects fruits exposed to temperatures below the optimum level for storage for sufficient time to cause injury. The symptoms of CI in pineapple include failure of the green shell to turn yellow, yellow-shelled fruit turning a brown or dull colour, wilting, drying and discolouration of crown leaves and a breakdown of internal tissue, giving a pale watery appearance (Dull, 1971; Abdullah et al., 2008). In bad cases, severe fungal diseases might infect the fruit. Visual symptoms of CI develop faster when the fruits are transferred to higher temperatures between 20 and 30 °C following exposure to low temperature, as different parts of the fruit have different levels of sensitivity towards CI (Abdullah et al., 2002). CI can be reduced or controlled through temperature manipulations. Pre-storage preconditioning at 15 and 10 °C also allows pineapple to be stored at sub-optimal temperature. The storage life of ‘N36’ pineapple is extended from five weeks at optimal temperature of 10 °C to more than eight weeks with less chilling injury at sub-optimal temperature of 5 °C (Abdullah et al., 2008). Similar treatments can also extend storage life of ‘Josapine’ pineapple. 10.6.2 Blackheart ‘Blackheart’, also known as ‘endogenous brown spots’ and ‘internal browning’, is another temperature-related physiological disorder of pineapple and has been comprehensively reviewed by Abdullah et al. (2010). The characteristic symptom of the disorder is the development of dark spots in the flesh area close to the core. In its early stage of development, the spots appear watery but they then enlarge and turn brown as the severity of the disorder increases. In severe cases, the entire flesh and core tissue of a fruit may be visibly affected. Fruits affected by blackheart appear normal externally and its presence is only detectable once the fruit has been cut open (Akamine, 1976; Akamine et al., 1975). The lack of detectable external symptoms creates substantial problems in the marketing of fresh fruit, as they have to be examined destructively. Blackheart may occur before harvest in the field or after harvest following exposure to low temperature and has been reported in fruits stored at temperatures as low as 4 °C and as high as 21 °C (Wills et al., 1985; Smith, 1983). Thus, in addition to the chilling at temperatures below the optimum, blackheart induction may also take place at temperatures higher than the normal range that causes CI. Blackheart has been associated with an increase in polyphenol oxidase (PPO)

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activity and reduction in ascorbic acid content in affected fruits (Teisson et al., 1979a,b). However, the initial PPO activity and ascorbic acid content do not necessarily indicate fruit susceptibility to blackheart (Stewart et al., 2002; Abdullah et al., 2010; Pauziah et al., 2005). Partial control of blackheart can be achieved by preharvest applications of chemicals such as parachlorophenoxyacetic acid (PCPA), α-naphthaleneacetic acid (ANA), potassium and calcium (Abdullah et al., 2009). Harvesting fruit at an earlier maturity can delay the appearance of blackheart symptoms but they can still appear at postharvest when exposure at ambient temperature is prolonged after low-temperature storage (Abdullah and Rohaya, 1997). After harvest, blackheart can be partially controlled by several methods including thermotherapy (Abdullah et al., 1983; Akamine et al., 1975), MA packaging (Abdullah et al., 1985; Haruenkit and Thompson, 1994; Mizuno et al., 1982), surface coating (Abdullah et al., 1983; Nimitkeatkai et al., 2006; Pimpimol and Siriphanich, 1993; Rohrbach and Paull, 1982; Zaulia et al., 2007) and 1-methylcyclopropene (1-MCP) (Selvarajah et al., 2001). Development of pineapple hybrids resistant to blackheart is the most practical approach to overcome the problem and some have been successfully developed in Hawaii and Malaysia (Abdullah et al., 2010). The Pineapple Research Institute of Hawaii has successfully developed two hybrid cultivars, ‘73–50’ and ‘53–116’ from Smooth Cayenne that show significant levels of resistance to blackheart. The ‘MD-2’, a superior hybrid developed by the Del Monte Corporation, is also resistant to blackheart (Bartholomew, 2009). Research on blackheart control through molecular breeding approaches has been conducted in Australia (Graham et al., 2000; Zhou et al., 2002) and Malaysia (Abu Bakar et al., 2008). 10.6.3 Flesh translucence Flesh translucence in pineapple is regarded as a physiological disorder by Py et al. (1987) and Paull (1997). The flesh affected by translucency shows water-soaking symptoms (Paull and Chen, 2003). It occurs together with fruit ripening when the shell colour at the base of pineapple fruit of some cultivars begins to turn yellow. It may also occur in green-ripe fruit where the whole flesh is affected while the skin is still green (Py et al., 1987). In the translucent flesh, the air space is filled with liquid where highly translucent fruit has a flat taste and might be off-flavour (Bowden, 1969). This off-flavour taste could be the result of anaerobic respiration of the flesh which is blocked from exchanging gases through the intercellular network. These fruits are very fragile and easily damaged during handling and transportation and are also susceptible to disease and preharvest sunburn (Paull and Reyes, 1996). The causes of flesh translucence are not well understood, but large fruit and fruit with small crowns tend to develop more symptoms of flesh translucence. High temperature, high radiation and high nitrogen fertilizer facilitate translucent flesh development, so shading the fruit may eliminate the translucency development (Py et al., 1987; Soler, 1993). Both crown weight and flesh translucency were

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reported to be correlated with monthly average air temperature two to three months before harvest (Paull and Reyes, 1996). However, crown removal does not influence translucency occurrence (Chen and Paull, 2001). After harvest, flesh translucency increases in stored fruits and it could be reduced by waxing (Rohrbach and Paull, 1982) and thermotherapy (Akamine et al., 1975).

10.7

Pathological disorders

The most important postharvest disease in pineapple is black rot, which can be found in all production areas around the world and the disease incidence could be as high as 70% of the inspected shipments to the New York market (Cappellini et al., 1988). The disease is caused by Thielaviopsis paradoxa (de Seynes) von Hohn which infects through a wound or cracked surface. The flesh of infected fruit becomes soft and watery and later turns dark due to the growth of the fungal mycelium and its chlamydospore. Postharvest control can be achieved by careful harvest and handling to prevent wounding or bruising and treating the fruit with suitable fungicides (see Table 10.2) within six to 12 hours after harvest (Rohrbach and Schmitt, 1994). Other pineapple diseases (Table 10.2) are caused by fungi or bacteria already present on the fruit at preharvest. Infection usually occurs through wound or cracks on the surface or damage caused by insects. The incidence of these diseases after harvest is rather limited as compared to black rot, and mostly cannot be controlled after harvest (Rohrbach and Schmitt, 1994). In addition to these infectious diseases, pineapple can be damaged by yeast and bacteria trapped inside the fruit during fruit development when individual fruitlets fuse together (Rohrbach and Apt, 1986). If fruit are damaged or overripe, the yeast and bacteria start growing leading to fermentation with bubbles of gas and juice escaping through cracks on the skin. The skin turns brown and leathery and the fruit becomes spongy with bright yellow flesh (Paull, 1997). Moulds on the cut surface of the peduncle are saprophytes but give an unsightly appearance (Paull, 1997). Dipping the fruit with a fungicide listed in Table 10.2 or adding coating material to the fungicide can control the mould growth.

10.8

Insect pests and their control

No major insects attack pineapple fruit, but a butterfly, Thecla basilides (Geyer) may lay eggs on the inflorescence. The larva penetrates and digs out holes causing misshapen fruit, and the fruit reacts by exuding an amber coloured gum which makes it impossible to sell. The existence of this insect is limited to Central and South America (Py et al., 1987). The Smooth Cayenne pineapple is resistant to all tropical fruit flies, namely the Mediterranean fruit fly (Ceratitis capitata Wiedemann), the melon fly (Dacus cucurbitae Coquillett) and the oriental fruit fly (D. Dorsalis Hendel) (Macion et al., 1968; Seo et al., 1970; 1973). The cultivar is not regarded as host and therefore quarantine treatment is not required for

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© Woodhead Publishing Limited, 2011 Fusarium subglutinans (Wollenweb. & Reinking)

Light to dark brown discolouration of fruitlet, sunken fruitlet, profuse pink sporulation and exudation of gum

Yellowish, reddish brown, to very dark, dull brown discolouration of fruit tissue. Infected tissues generally become harden, granular, brittle and speckled with colour variation

Fruit turns brown or black when cooked during canning process. Uncooked may be symptomless or light pink to brown and may smell like cantaloupe

Fusariosis

Marbling

Pink disease

Through open flower by nectar feeding, insects remain latent until fruit ripening

Usually low incidence, found mostly in cool area where air temperature does not exceed 29 °C

Compiled from: Damayanti et al. (1992); Lim (1985); Rohrbach and Phillips (1992); Rohrbach and Schmitt (1994); Py et al. (1987).

Erwinia herbicola, Erwinia sp. Gluconobacter oxyden (Henneberg) de ley Acetobacter aceti (Pasteur) (Syn. Acetobacter liquefaciens)

No postharvest control

No postharvest control

No postharvest control Worldwide but epidemic in lowland tropics where temperature remains above 21 °C

Flower through South America caterpillar wound

Brazil, Hawaii, South Africa

Low temperature 8–9 °C; gamma radiation 50–250 Gy; use of fungicides within 6–12 hours after harvest such as benomyl 1200–1400 ppm, triademenol 250 ppm, imazalil 250 ppm, triademefon 500 ppm, sodium salicyl anilide 1%, o-phenylphenol, captan, salicylic acid, benzoic acid No postharvest control, endosulfan at forcing and 3 weeks after forcing

Worldwide, especially in lowland tropics

Through wounds or cracks within 8–12 hours

Unopen flower through mite injured trichome

Control

Distribution

Infection

Open flower and Acetobacter peroxydans Visser’t Hooft, Acetobacter cracks on the fruit sp. and Erwinia herbicola var. ananas (Serrano)

Penicillium funiculosum Thom, Fusarium subglutinan (Wollenweb. & Reinking)

Thielaviopsis paradoxa (de Seynes) von Höhn (Syn. Chalara paradoxa (de Seynes) Sacc.)

Soft watery flesh later turn dark from the growth of mycellium and chlamydospore

Black rot, water rot, water blister, soft rot, or Thielaviopsis fruit rot

Centre part of an individual Fruitlet core rot, leathery pocket, eye rot, interfruitlet fruitlet becomes brown to black, distorted fruit shape corking, black spot, or fruitlet brown spot

Pathogen

Symptom

Nature and control of postharvest diseases in pineapple

Name

Table 10.2

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importation into fruit fly-free countries (Paull, 1997). For other cultivars, vapour heat treatment at 44.6 °C for 8.75 hours is required in mainland United States (Armstrong, 1994). Surface insects including mealy bug, scale and mite cause some postharvest problems. These insects should be well controlled before harvest since they can easily miss detection or removal during postharvest handling, by hiding underneath the bract on individual fruitlets and in the crown. They can be removed by using a brush or water jet during the washing procedure. If these surface insects are found upon entry to the United States, the fruit must be fumigated with methyl bromide at concentrations depending on the temperature at the time of fumigation (Armstrong, 1994). Exporting pineapple to China also requires the control of surface insects besides fumigation with methyl bromide.

10.9

Postharvest handling practices

10.9.1 Harvesting Pineapple is harvested once it has already achieved its optimum maturity for consumption. A minimum total soluble solids (TSS) level of 12% is the requirement under the worldwide Codex standard for fresh pineapple (Codex Alimentarius, 2007). Changes on the skin colour and shape of the eyes can be used to estimate fruit maturity. For ‘Mauritius’, the fruit are harvested at breaker stage, i.e. 120 days after flower induction. Fruits for nearby market are harvested at a more advanced stage as customers prefer ripe pineapple. Being a non-climacteric fruit, the taste and flavour of pineapple are better developed in the tree-ripened fruit and they will not improve after harvest (Dull, 1971). During harvesting, pineapple is cut off the plant with a machete. Harvesting should be done carefully to prevent bruising, especially for large fruit. Harvested fruits are placed inside the basket on the back of workers (see Plate XIX in the colour section). When the basket is full, the fruit are piled up at the end of rows or directly loaded on to a truck, for transportation to the packinghouse as soon as possible. The use of crates while in the field is encouraged to reduce mechanical injury. In large-scale plantations, carrying fruit by hand is avoided by using a harvesting aid. In this case, harvesting crews walk between rows of pineapple following the ‘harvester’, which has a boom with a conveyer belt extended to the side. Pickers harvest the fruit and place them on the belt, but fruit is better placed by hand in the field bin upside down to avoid injury (Py et al., 1987). While in-field it is also important to leave the fruits under shaded conditions for protection from the sun. 10.9.2 Packinghouse operations Harvested fruits are prepared for the markets at packinghouses which may be located either inside or outside the farm. Packinghouse operations for pineapple may include cleaning, washing, grading, sizing, fungicide treatment, surface coating, drying and

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packaging (Abd Shukor et al., 1998; Abdullah et al., 2000). Suitable operations conducted would depend on the market, method of transportation and duration to reach the market as the operations for the domestic market are usually simpler than for the export markets. Once arrived at the packinghouse, pineapple can be unloaded by hand, dumped, sliding or submerging the whole container into a water tank to remove dirt and surface insects. A water jet or brush could also be used for cleaning. Bracts at the base of the fruit should be removed by hand, since insects could be hiding underneath, and the fruit stem is trimmed to about 5–20 mm for vertical packing. Sorting for green-ripe fruit could also be done at this stage since they sink while others float in water (Py et al., 1987). Specific gravity may be used as an index of eating quality. Smith (1988a) suggested the use of two water tanks containing water and a 2.5% salt solution to grade pineapple into three groups: floated in water, sunk in water but floated in salt solution, and those sunk in salt solution. Due to the natural progressive development of flesh translucency from the base to the top of the fruit, the angle of fruit floating in water could also be used to separate fruit with different degrees of translucency. Those that float in an upright position are most translucent, while those that float at 45 degree or lay horizontal are less translucent (Songprateep, 1990). After washing, pineapples are sorted to remove defected ones such as malformed, bruised or insect damaged. Fruit with black rot can also be removed judging from early degreening of some fruitlets. Fruit with an under- or over-developed crown could also be removed (Py et al., 1987). In Hawaii, crown to fruit size ratio should be within 0.33 to 1.5 (Paull, 1997). Large crowns could also be reduced by ‘gouging’ in which part of the crown is removed. This technique leaves a wound, may reduce overall appearance, and could cause disease development during subsequent transport or storage. Gouging can also be done in the field two months before harvest to allow proper healing (Py et al., 1987). A fungicidal treatment such as thiabendazol (TBZ) is applied by dipping or spraying to control black rot disease caused by Thielaviopsis paradoxa. In small-scale operations, pineapple is classified manually according to sizes by experienced workers and a simple balance is used to check fruit weight when in doubt. Sizing machines either by diameter or by weight are also available in large-scale operations including diverging belt and rotary weighing sizer. Under Codex standards, pineapple is classified into three classes, namely ‘Extra Class’, ‘Class I’ and ‘Class II’ according to fruit quality. Size is determined by the average weight of the fruit with a minimum weight of 700 g, except for small size varieties, which can have a minimum weight of 250 g (Table 10.3). 10.9.3 Packaging and transportation Pineapple for local markets in some developing countries are transported either in bulk without container or placed in traditional containers such as bamboo baskets. In some countries, the use of traditional baskets has been replaced with returnable plastic baskets or containers with improved features including better strength and stackable. Corrugated fibreboard cartons with specific design, dimension and capacity are most commonly used for export markets. In Hawaii, large cartons of

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Postharvest biology and technology of tropical and subtropical fruits Table 10.3 Size classification of pineapple under the Codex standard for pineapple Size code

A B C D E F G H

Average weight (+/− 12%) (in grams) With crown

Without crown

2 750 2 300 1 900 1 600 1 400 1 200 1 000 800

2 280 1 910 1 580 1 330 1 160 1 000 830 660

Source: Codex Alimentarius (2007).

20 kg containing six to ten fruits are used for surface or sea shipment, whereas smaller cartons of 10 kg containing five to six fruits are used for air shipment (Paull and Chen, 2003). Fruits in the cartons are arranged either vertically or horizontally with cushioning pads placed at the inner bottom and in between layers for protection from mechanical injury during handling and transportation. 10.9.4 Recommended storage and shipping conditions The recommended optimum temperatures for pineapple are 7–13 °C with relative humidity of 85–95% (see Sections 10.5.2 and 10.5.3). Under this condition, mature green fruit can remain fresh for four to five weeks. Fruits of more advanced maturity have shorter storage life than those of lesser maturity. The same temperatures are used for shipping pineapples in refrigerated containers. For shipping by sea, matured green fruits are stored or transported at 10 °C, whereas a temperature of 7.5 °C is used for fruits of more advanced maturity. For air shipment, fruit harvested at advanced maturity can be used and stored temporarily at 7.5 °C before being transported. MA or CA is not needed for transportation, as the benefit is minimal for storage life extension. Pineapple is compatible with many types of non-climacteric fruits and vegetables when transported under mixed load conditions. The most important consideration in mixed loads is compatibility with respect to their requirements for temperature, relative humidity, atmosphere, protection from odours, and protection from physiologically active gases, such as ethylene (Wilson et al., 1998; Mohd Salleh et al., 2008). 10.9.5 Control of ripening and senescence Storage life extension by preconditioning and storage at sub-optimal temperature are discussed in Section 10.6.1. Suitable postharvest treatments are covered in Sections 10.6.2 and 10.7 of this chapter.

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Processing

10.10.1 Fresh-cut processing Being a large size fruit and relatively hard to peel, pineapple is well suited to be prepared and sold as fresh cut or minimally processed (Siriphanich, 1994). Good handling practices for minimally processed pineapple involve the use of high quality fruits, high sanitation in preparation, good packaging and maintenance of a cold chain. The common temperatures used are 1–4 °C. Tissue injuries in freshly cut pineapple lead to a higher metabolic rate and shorter storage life than for the whole fruit. The use of very sharp knifes for cutting is necessary as fruit with fewer cuts have a lower metabolic rate than those with more cuts (Iverson et al., 1989). Fresh cut pineapple is also subjected to spoilage by microorganism. Yeast and fungi are of primary concern, while bacteria are secondary due to the low pH of the pineapple flesh. Sanitation during the preparation of fresh cut pineapple should be of primary concern for quality and safety. Newly prepared fresh cut pineapple, under careful preparation, could have as much as 105 cfu.g−1 total plate counts of microbial contamination (O’Conner-Shaw et al., 1994). The count could also vary up to 100 fold between preparations. The two most important microorganisms are Listeria monocytogenes, a saprophyte able to grow at low temperature and Escherichia coli, which is acid resistant. Contamination by microorganisms in the flesh may originate from the fruit before cutting but the level of contamination could be reduced by washing the fruits with clean and chlorinated water. With careful preparation, fresh cut pineapple can be stored for up to three weeks at 4 °C (Fadrigalan et al., 2000; Latifah et al., 1999; 2000). Powrie et al. (1990) claimed that fresh cut pineapples sealed in plastic bags and flushed with 15–20% oxygen and 3% argon can be stored for up to ten weeks at 1 °C. Another food preservation technique by using ultra-high pressure has also been studied on fresh cut pineapple (Aleman et al., 1994). However, browning can still proceed after this high-pressure treatment where PPO is relatively resistant to inactivation under high-pressure treatment (Aleman et al., 1998). The addition of ascorbic acid and storage at low temperature could delay the browning (Chen and Paull, 2001; Chen et al., 2000).

10.10.2 Other processed products Various processed products from pineapple were described by Abd Shukor et al. (1998). The products include juice, canned flesh, fruit cocktail, crushed pineapple, fruit punch, frozen pineapple, yoghurt, pineapple powder, freeze-dried pineapple, wines, sauces, jams, marmalades and confectionery. Collins (1968) has comprehensively reviewed by-products from pineapple fruit. The possible by-products include syrup from a cannery, alcohol, feed yeasts, organic acids such as citric acid and malic acid from the mill juice, and starch, protease and fibres from the plant residues of pineapples. Other pineapple by-products include bromelain, vinegar, wine and feed (Dev and Ingel, 1982).

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10.11

Conclusions

The pineapple has become one of the most established tropical fruits in world trade. The global pineapple industry continues to play very important roles for the future in meeting consumers needs and providing a good source of income and livelihood for many people. Many aspects of pineapple production and postharvesting have been studied and investigated by producing beneficial results but the vast knowledge and technologies that have been generated need further expansion in order to face new challenges. Research on the aspects of quality, safety, health and highly efficient technology, besides greater concern for environment, should be given stronger emphasis in the future.

10.12 Acknowledgements The authors wish to express their sincere thanks to Mrs Rohaya Md Atan and Mr Md Syahril Md Khalil of MARDI for their kind assistance in the preparation of the manuscript.

10.13

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with blackheart development of Malaysian pineapples’. MARDI Horticulture Research Centre Technical Report, 172–175. Pimpimol J and Siriphanich S (1993), ‘Factors effecting internal browning disorder in pineapples and its control measures’, Kasetsart Journal (Nat. Sci.), 27, 421–430. Powrie W D, Chiu R, Wu H and Skura B J (1990), ‘Preservation of cut and segmented fresh fruit pieces’, U.S. Pat. #4, 895, 729. Py C, Lacoeuilhe J J and Teisson C (1987), The Pineapple Cultivation and Uses, Editions G-P Maisonneuve & Larose, Paris, 568 p. Rodin J O, Himel C M, Silverstein R M, Leeper R W and Gortner W A (1965), ‘Volatile flavor and aroma components of pineapple. I. Isolation and tentative identification as 2,5-dimethyl-4-hydroxy-3(2H)-furanone’, J Food Sci, 30, 280–285. Rohrbach K G and Apt W J (1986), ‘Nematode and disease problems of pineapple’, Plant Disease, 70, 81–87. Rohrbach K G and Paull R E (1982), ‘Incidence and severity of chilling induced internal browning of waxed “Smooth Cayenne” pineapple’, J Amer Soc Hort Sci, 107, 453–457. Rohrbach K G and Phillips D J (1992), ‘Postharvest diseases of pineapple’, Acta Hort, 269, 503–508. Rohrbach K G and Schmitt D P (1994), ‘Part IV. Pineapple’, in Ploetz R C, Nishijima W T, Zentmyer G A, Rohrbach K G and Ohr H D, Compendium of Tropical Fruit Diseases, St Paul, APS Press, 45–55. Selvarajah S, Bauchot A D and John P (2001), ‘Internal browning in cold-stored pineapples is suppressed by a postharvest application of 1-methylcyclopropene’, Postharvest Biology and Technology 23, 167–170. Seo S T, Chambers D L, Kobayashi R M, Lee C Y L and Komura M (1970), ‘Infestations of oriental fruit flies in 53–116 and Smooth Cayenne pineapple varieties grown near supporting guava or other host fruits’, J Econ Entomology, 63, 1830–1831. Seo S T, Chambers D L, Lee C Y L, Komura K, Fujimoto M and Kamakahi (1973), ‘Resistance of pineapple variety 59–443 to field populations of oriental fruit flies and melon flies’, J Econ Entomology, 66, 522–523. Singleton V L (1965), ‘Chemical and physical development of the pineapple fruit. I. Weight per fruitlet and other physical attributes’, J Food Sci, 30, 98–104. Singleton V L and Gortner W A (1965), ‘Chemical and physical development of the pineapple fruit. II. Carbohydrate and acid constituents’, J Food Sci, 30, 19–23. Siriphanich J (1994), ‘Minimal processing of tropical fruit’, in Champ B R, Highley E and Johnson G, Postharvest Handling of Tropical Fruit, ACIAR Proceedings, No. 50, pp. 127–137. Smith L G (1983), ‘Causes and development of black heart in pineapples, Trop Agric (Trinidad), 60, 31–35. Smith L G (1984), ‘Pineapple specific gravity as an index of eating quality’, Trop Agric (Trinidad), 61, 196–199. Smith L G (1987), ‘Quality improvements for Australian fresh market pineapples’, Food Technol Australia, 39, 64–68. Smith L G (1988a), ‘Indices of physiological maturity and eating quality in Smooth Cayenne pineapples. I. Indices of Physiological maturity’, Queensland J Agric Animal Sci, 45, 213–218. Smith L G (1988b), ‘Indices of physiological maturity and eating quality in Smooth Cayenne pineapples. II. Indices of eating quality’, Queensland J Agric Animal Sci, 45, 219–228. Soler A (1993), ‘Enzymatic characterization of stress induced translucence of pineapple flesh in the Ivory Coast’, Acta Hort, 334, 295–304. Songprateep P (1990), ‘The relationship of floating characteristics on maturity and chilling injury of pineapple cv. Smooth Cayenne’, Bachelor Special Problems, Department of Horticulture, Kasetsart University, Bangkok, Thailand, 26 p.

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Stewart R J, Sawyer B J B and Robinson S P (2002), ‘Blackheart development following chilling in fruit of susceptible and resistant pineapple cultivars’, Aust J Exp Agric, 42, 195–199. Takeoka G R, Buttery R G, Teranishi R, Flath R A and Guntert M (1991), ‘Identification of additional pineapple volatiles’, J Agric Food Chem, 39, 1848–1851. Teai T and Claude-Lafontaine A (2001), ‘Volatile compounds in fresh pulp of pineapple (Ananas comosus (L.) Merr.) from French Polynesia’, Journal of Essential Oil Research, 13, 314–318. Tee E S, Mohd Ismail N, Mohd Nasir A and Khatijah I (1988), Nutrient Composition of Malaysian Foods, Kuala Lumpur, ASEAN-Australia Economic Cooperation Programme. Teisson C, Lacoeuilhe J J and Combres, J C (1979b), ‘Le brunissement interne de l’ananas. V. Recherches de moyens de lutte’, Fruits, 34, 399–415. Teisson C, Martin-Prevel P and Marchal J (1979a), ‘Le brunissement interne de l’ananas. IV. Approche biochimique du phenomene’, Fruits, 34, 329–339. Umano K, Hagi Y, Nakahara K, Shoji A and Shibamoto T (1992), ‘Volatile constituents of green and ripened pineapple (Ananas comosus (L.) Merr.)’, J Agric Food Chem, 40, 599–603. van Lelyveld L J and de Bruyn J A (1977), ‘Polyphenols, ascorbic acid and related enzyme activities associated with black heart in Cayenne pineapple fruit’, Agrochemophysica, 9, 1–6. Vidal-Valverde C, Herranz J, Blanco I and Rojas-Hidalgo E (1982), ‘Dietary fiber in Spanish fruits’, J Food Sci, 47, 1840–1845. Wills R B H, Abdullah H, Scott K J (1985), ‘Effect of storage time at low temperature on the development of blackheart in pineapples’, Trop Agric (Trinidad), 62, 199–200. Wilson L G, Boyette M D and Estes E A (1998), ‘Part IV: Mixed loads’, in Postharvest Handling and Cooling of Fresh Fruits, Vegetables and Flowers for Small Farmers, North Carolina State University. Available from http://www.ces.ncsu.edu/hil/hil803html (accessed 12 December 1998). Wu P, Kuo M, Hartman T G, Rosen R T and Ho C (1991), ‘Free and glycosidically bound aroma compounds in pineapple (Ananas comosus L. Merr.)’, J Agric Food Chem, 39, 170–172. Yahia E M (1998), ‘Modified and controlled atmospheres for tropical fruits’, in Janick J, Horticultural Reviews, 22, 123–183. Zaulia O, Suhaila M, Azizah O, Mohamed Selamat M (2007), ‘Effect of various coatings on the chemical changes of different pineapple cultivars (N36 and Gandul) at low temperature storage’, J Trop Agric Food Sci, 35, 107–120. Zhou Y, Jobin-Decor M, Dahler J, Wills R, Underhill S, Graham M W (2002), ‘Optimising transient assays for studying the regulation of PPO gene expression in pineapple blackheart’, Acta Hort, 575, 595–601. Zhou Y, Dahler J M, Underhill S J R, Wills R B H (2003), ‘Enzymes associated with blackheart development in pineapple fruit’, Food Chem, 80, 565–572.

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Plate XVIII

Plate XIX

(Chapter 10) Pineapple production on peat soil in Johor, Malaysia.

(Chapter 10) Harvesting pineapple for processing in Johor, Malaysia.

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11 Pistachio (Pistacia vera L.) M. Kashaninejad, Gorgan University of Agricultural Sciences and Natural Resources, Iran and L. G. Tabil, University of Saskatchewan, Canada

Abstract: The pistachio nut (Pistacia vera L.) is one of the most popular tree nuts in the world and is valued globally for its nutritional value, health and sensory attributes and economic importance. It is high in unsaturated fatty acids and low in saturated fatty acids, a rich source of proteins, dietary fibers, vitamins, minerals and antioxidants, and is an increasingly important nut crop consumed raw, salted or roasted. In common with other tree nuts, pistachios are rich in nutrient content and beneficial for the human diet. Careful harvesting, appropriate postharvest handling and proper processing, storage and packaging, all contribute to achieve optimum yield of high quality nuts. Pistachio nuts should be processed as soon as possible after harvest and stored in appropriate conditions to avoid mold growth and undesirable chemical reactions such as oxidative rancidity. This chapter will provide information about the botany, worldwide importance, postharvest pathology, harvesting, handling, processing and storage of pistachio nut. Key words: Pistacia vera, pistachio nut, processing, drying, roasting, aflatoxin.

11.1

Introduction

11.1.1 Origin and history The word pistachio is a loanword from the Zendor Avestan (ancient Persian language) pista-pistak (Joret, 1976) and is a cognate to the modern Persian word Peste. According to Dioskurides, the pistachio is derived from pissa (means resin) and aklomai (means to heal), i.e. a plant with healthy resin. The common name of pistachio in different languages is: Peste (Persian), Pistache (French), Pistazie (Germany), Pistacchio (Italian), Pistacho (Spanish), Pista (Indian), Pistasch (Swedish), Fustuq (Arabic) and Pisutachio (Japanese). The origins of the pistachio are Asia Minor (now Turkey), Iran, Syria, Lebanon, the Caucasus in southern Russia and Afghanistan (Zohary, 1952). It probably developed in interior desert areas because it requires long, hot summers for fruit maturation, is drought and salt tolerant, and has a high winter chilling requirement.

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Archeologists have found evidence in a dig site at Jarmo, near northeastern Iraq, that pistachio nuts were a common food as early as 6750 BC (Kirkbride, 1966; Kramer, 1982). The history of pistachio nuts reflects their ‘royal character’, endurance and pride. Especially fine pistachios are said to have been a favorite delicacy of the Queen of Sheba, who confiscated all Assyrian deliveries for herself and for her royal court (Whitehouse, 1957). Nebuchadnezzar, the ancient king of Babylon, had pistachio trees planted in his fabled hanging gardens around the 8th century BC (Brothwell and Brothwell, 1969). In the 2nd century BC, Nicander found pistachio in Susa, a village in southwestern Iran close to the border with Iraq (Joret, 1976). In the 1st century BC, Poseidonius recorded cultivated pistachio in Syria (Joret, 1976), and the nuts traveled from Syria to Italy in the 1st century AD and spread throughout the Mediterranean from there (Banifacio, 1942; Moldenke and Alma, 1952). Pistachio has been spread eastward from its center of origin and was reported in China around the 10th century AD (Lemaistre, 1959). It was introduced to USA in 1854 but commercial plantings did not develop until 1970 (Rieger, 2006). More recently pistachio has been cultivated in Australia. 11.1.2 Botany Pistachio is the only commercially edible nut among the 11 species in the genus Pistacia that all exude turpentine or mastic. Pistacia vera L. (Latin name of pistachio) is by far the most economically important and a member of the Anacardiaceae or cashew family. Other important members of this family are cashew, mango, mombins (Spondias spp.), poison ivy, poison oak, pepper tree and sumac. P. nigricans Crantz, P. officinarium Ait, P. reticulate Willd and P. terebinthus Mill are the synonyms of P. vera L. Pistachio trees are small to medium size and can grow to 12 m, but are generally smaller in the cultivation period. Leaves are compound-pinnate and generally with three and sometimes five leaflets. Their shapes vary from ovoid to oblongovoid with dark green above and paler below on entire margins and obtuse tips. The flowering behavior of pistachio trees depends on their location, which can be steppe-forests, steppe or semi-desert. Floral bud differentiation takes place before blossoming. Shoot elongation usually commences at the end of March and ends between April and May (Crane and Iwakiri, 1981). One or two axillary buds located on the new growth are vegetative. Inflorescence buds which are conspicuously larger than vegetative buds expand at the following March, and anthesis generally takes place at the end of May and after about three weeks they grow and differentiate very fast. The pistachio tree is dioecious, meaning that male and female flowers are borne on separate trees. Therefore, both male and female trees are required to produce nuts. The pistachio tree has about 13 primary branches with each bearing one terminal and five to 19 lateral flowers. The flowers are apetalous and include up to five sepals. Male flowers have five small stamens and females include a single tricarpellate, superior ovary. Since the female flowers are nectarine-free they cannot attract bees, although they may be attracted to male

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flowers for pollen. Therefore, the pollen is spread by wind. Pistachios grow on trees in grape-like clusters on first-year-old wood (see Plate XX in the colour section between pages 238 and 239). Based on location and variety, fruit development occurs at different times. For ‘Kerman’ variety following proper and successful pollination, fruit set and endocarp (nut shell) begins to enlarge in late April until May, while the kernel does not grow. During this period, the shell is very soft and sensitive to insect attacks. The shell begins to harden in June and from late June until early August the kernel grows and fills the shell. Nut ripening takes place during late August and September and the shell splits more and more along the ventral suture, hull color changes from green to red and abscission of the individual nut begins from the rachis (Hendricks and Ferguson, 1995). Fruiting takes place four to five years after transplanting but full bearing and economically significant crops happen around ten years of age. The pistachio fruit (nut) is a drupe and almost oval shape. It consists of a single seed (kernel), encased by a thin soft and edible seed coat (testa or skin), enclosed by a hard smooth inedible shell (endocarp), which is further surrounded by the fleshy hull (mesocarp and epicarp), which is also inedible (see Plate XXI in the colour section). The hull is thin and fleshy, pale green in color, with a red blush at maturity. The shell dehisces along the ventral suture with kernel growth and progresses along both sutures until physiological maturity reaches maximum size. The seeds range in color from light to dark green or greenish-yellow (called pistachio kernel green) and contain two cotyledons surrounded by a thin coating. Physiological maturity is manifested by loosening and easy separation of the hull from the shell and changing of the hull color from green to red (Crane, 1978). 11.1.3 Varieties Many cultivated varieties of pistachio are available in different countries with significant variation in their characteristics particularly in terms of size, shape, color, taste and splitting. Maggs (1973) reported that the main pistachio varieties in the world have been spread from Iran, Turkey and Syria. These varieties were obtained through seedling selection in the field. Pistachio is cultivated in different regions of Iran but Kerman province is the largest and most important pistachio growing area with much higher genetic diversity of pistachio than other regions. More than 70 varieties have been recorded in this province. ‘Ohadi’ or ‘Fandoghi’, ‘Kalle-Ghuchi’, ‘AhmadAghaei’, ‘Badami’, ‘Rezaei’ and ‘Momtaz’ are the major varieties grown in Kerman province (Fig. 11.1). ‘Ohadi’ cultivation has been increased during the last 40 years and now includes about 70% of pistachio orchards in this region. It is round-shaped with a light yellow to green kernel, bearing large bunches of green hulled and high splitting nuts. It produces attractive and good quality nuts suitable for export. Large fruit, high yield and good split percentage are the main reasons for the popularity of ‘Kalle-Ghuchi’ variety. It is also round-shaped with light green kernel (Esmail-pour, 2001).

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Fig. 11.1 Pictorial view of nut (left) and kernel (right) of five Iranian pistachio varieties; from top to bottom: ‘Akbari’, ‘Badami’, ‘Kalle-Ghuchi’, ‘Momtaz’ and ‘Ohadi’.

There are about 20 female pistachio varieties in Syria of which ‘Ashouri’ (‘Red Aleppo’), ‘Red Oleimy’ and ‘White Batoury’ are three main varieties. ‘Ashouri’ accounts for about 85% of the total pistachio area in Syria. A 40-year-old tree of ‘Ashouri’ variety produces up to 200 kg of fresh nuts per year. It is the best Syrian variety in terms of splitting (with 99%) and excellent as a table variety. ‘Ashouri’ nuts are elongated and red with dark spots and medium size (27 mm length, 15 mm width and 14.5 mm thickness) (Hadj-Hassan, 2001). In Turkey, there are eight main domestic varieties including ‘Uzun’, ‘Kirmizi’, ‘Halebi’, ‘Siirt’, ‘Beyazben’, ‘Sultani’, ‘Degirmi’ and ‘Keten Gomlegi’ and five foreign varieties from Iran including ‘Ohadi’, ‘Bilgen’, ‘Vahidi’, ‘Sefidi’ and ‘Momtaz’. Most of the harvested crop consists of ‘Uzun’ and ‘Kirmizi’ varieties. The ‘Uzun’ variety is long (19 to 21 mm) and plump; some of the nuts are half as wide as they are long with a splitting percentage of 69%. ‘Kirmizi’ is a red-hulled, thin-shelled, free-splitting, green kernel nut of medium size. All Turkish varieties except ‘Siirt’ have elongated nuts while ‘Siirt’ has ovoid nut shape. ‘Siirt’ is the best Turkish variety in terms of splitting with 92%. Domestic varieties generally have yellowish green kernels (Ak and Acar, 2001). About 20 varieties have been imported as seed from other countries to the United States and tested to develop as a local variety but the results have demonstrated that a special variety’s success in another country does not mean a successful performance in the United States. ‘Kerman’, a developed California variety, named after the main pistachio area in Iran (Kerman province) was introduced in the 1950s after testing for several years in California. Now, it is the main commercial variety grown in California consisting of about 99% of pistachio production in this state. It produces high yields of large nuts but it has a strong alternate-bearing habit and many blanks and non-split nuts. It has light greenish-yellow kernel with minimum flavor particularly after drying in commercial dryer. American consumers prefer pistachios from other countries because of better flavor and color attributes. ‘Joley’ is another female variety that was introduced from Damghan, Iran and has been planted mainly in New Mexico and a few orchards in California. It is smaller than ‘Kerman’ variety with greener kernel and better taste. It has almond-shaped nuts with high non-split percentage in some years.

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11.1.4 Uses Pistachio is cultivated for nut production and the nuts are mainly used for eating out of hand as fresh, dried, and roasted with or without salt and flavorings. The pistachio is unique in the nut trade because of shell splitting naturally before harvesting. This advantage allows pistachio nuts to be marketed extensively in-shell for fresh consumption, because their kernels can be easily separated without mechanical cracking. It also enables the processor to roast and salt the kernel without shell removal while almonds, walnuts and pecans are generally sold shelled to the industrial trade. In the United States, after roasting and salting of raw pistachio nuts, the shell is colored with a red dye to cover shell stains and blemishes and sold as ‘Red’ pistachios. Pistachio nuts are also used in pastries, cakes, ice creams, confections, baked goods, candies, sausages and desserts. Pistachio is an excellent taste enhancer and can be added to many food products to improve nutrition, color and flavor. The utilization of pistachio nuts in the producing countries are more varied than in the importer countries. In Iran, the hulls are used for fertilizer, feed for ruminants and small amounts are made into a flavorful marmalade (Mohammadi Moghaddam et al., 2009). A small amount of pistachio oil is produced for eating and use in cosmetics, while a limited amount of pistachio is also used for production of pistachio butter (Taghizadeh and Razavi, 2009). This butter, a semisolid paste, is made from ground and roasted pistachio kernels with addition of some flavorings and sweeteners. Pistachio butter is a nutritive product rich in lipids, proteins, carbohydrates and vitamins, and can be used in different food products such as cookies, ice creams and cakes. The hull is used for dyeing and tanning in India. 11.1.5 Worldwide importance and economic value World commercial production of pistachio nuts increased more than tenfold, from 47 584 tonnes in 1970 to 517 823 tonnes in 2007 (FAOSTAT, 2009). Pistachio nuts are produced commercially in 18 countries on 608 729 hectares. According to the Food and Agriculture Organization (FAO), the top six pistachio producers in 2007 were Iran at 230 000 tonnes (44.4% of the world’s production), followed by the United States (108 598 tonnes, 20.97% share), Turkey (73 416 tonnes, 14.18% share), Syria (52 066 tonnes, 10.05% share), China (38 000 tonnes, 7.34% share) and Greece (9 000 tonnes, 1.7% share). Pistachio production in Iran, Turkey, Syria, China and Greece increased 4.14, 1.56, 3.93, 1.15 and 7.14-fold, respectively from 1970 to 2007. As shown in Fig. 11.2, Iran’s production has been the key factor driving the global growth trend. However, production of the United States increased from 0 in 1970 to 108 598 tonnes in 2007, making it the second highest world producer after Iran. Alternate bearing, blanking and non-splitting are three physiological disorders that affect the fluctuation of commercial yield. Plantings have recently increased dramatically in the major producer countries of Iran, United States and Turkey. For example, pistachio production in the United States has increased from 688 bearing hectares in 1977 to 46 136 in 2007. In Iran,

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Global, Iran and United States pistachio production from 1970 to 2007.

it increased from 47 000 to 440 000 hectares during the same period. Although pistachio production has been initiated in countries such as Australia, Mexico, Argentina and South Africa, their production numbers have not reached competitive levels. Average yield per tree ranges from 2 to 22.5 kg/year. An average 3 kg of unshelled nuts yield 1 kg shelled. In 2000, world yields varied from 500 kg.ha−1 to 3037 kg.ha−1 with an average of 1117 kg.ha−1 (Kaska, 2002). Duke (2001) reported yields from 2 to 8 kg unshelled nuts per tree or 200 to 800 kg.ha−1 for 8 to 15 year old trees and 8 to 30 kg per tree or 800 to 2400 kg.ha−1 for 16 to 30 year old trees. Global pistachio export has increased from 13 531 tonnes (valued $1.36 million) in 1970 to 313 372 tonnes (worth $1.36 billion) in 2007. Iran and Turkey has been the major exporter in 1970 with 74 and 25% of world exports, respectively. Figure 11.3 shows the major exporters of pistachio nuts in 2006. According to FAO, Iran was the leading exporter of pistachio nuts in 2006 with 163 431 tons or 55% of global export followed by the United States with 48 571 tonnes or 17% of world export. Most export of Iranian pistachio is bound for Hong Kong, Germany, United Arab Emirates, Russia, Spain, Italy and India. Some of Iranian pistachio markets are also major exporter such as Hong Kong and Germany although they were among the top global pistachio importers in 2006 (Fig. 11.4). As many of these countries are not pistachio producers, it proves that trans-shipment or further processing occurs often with this commodity. Hong Kong and Germany are the major trans-shipper of pistachio nuts. In 2006, Germany imported pistachio valued at $199 million, primarily from Iran and the United States and exported pistachios valued at $106 million to other European countries.

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Fig. 11.3 The leading global exporters of pistachio nuts 2006.

Fig. 11.4 Top global importers of pistachio in 2006.

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11.1.6 Composition, nutritional value and health benefits Pistachio nuts are highly valued for their nutritional, sensory and health attributes. In addition to being high in unsaturated fatty acids and low in saturated fatty acids, they are good sources of proteins, dietary fibers, vitamins, minerals and antioxidant phytochemicals. Nutritionally, pistachio nuts are better than other tree nuts and peanut because they are lower in calories and fat content and higher in protein, carbohydrate and potassium. The composition of pistachio nut may vary depending on variety and maturity at harvest time. Tables 11.1–11.3 present the chemical composition and nutritional value, fatty acid and amino acid profiles of two varieties of pistachio nut. Mono- and poly-unsaturated fatty acids constitute more than 80% of pistachio oil. Carbohydrate analysis of pistachio has indicated the predominant sugar to be sucrose followed by raffinose, glucose, fructose, maltose and stachyose with traces of isomaltose and cellobiose (Kashani and Valadon, 1984). The globulin fraction is the major protein in the pistachio, contributing about two-third of the total protein (66%). Albumins are second in predominance to globulins, contributing 25% of the total protein, followed by glutelins (7.3%) and prolamins (2%) (Shokraii and Esen, 1988). All essential amino acids are present in pistachio where lysine is present at a high level and with only cystine in a limited amount. Pistachio nut contains substantial levels of a diverse range of phytochemicals such as carotenoids (lutein), phytosterols and phenolic compounds (flavonoids and resveratrol) in the kernel and skin. The presence of anthocyanins in pistachio nut is a unique characteristic that causes the red-purple color in the skin of the pistachio. Anthocyanins are water-soluble pigments that impart the attractive red, Table 11.1 Chemical composition of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Component (unit)

Moisture (%) Oil (%) Protein (%) Carbohydrates (%) Crude fiber (%) Ash (%) Potassium (mg 100 g−1) Phosphorus (mg 100 g−1) Iron (mg 100 g−1) Calcium (mg 100 g−1) Magnesium (mg 100 g−1) Sodium (mg 100 g−1) Copper (mg 100 g−1) Energy (kcal 100 g−1)

Variety Ohadi

Kerman

2.54 57 20.8 13.8 1.93 2.6 1170 560.5 10.3 179.3 102.6 10.7 1.3 570

3.97 44.44 20.61 27.97 1.03 3.02 1025 490 4.15 107 121 1 ______ 557

Source: Shokraii (1977); USDA (2006).

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Postharvest biology and technology of tropical and subtropical fruits Table 11.2 Fatty acid profile of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Amount (%)

Fatty acid

C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C18:4 C20:0 C22:0

Ohadi

Kerman

____ 13.4 2.0 1.0 49.5 31.8 Trace 2.2 _____ _____

Trace 12.59 0.52 0.90 57.48 27.93 0.57 _____ Trace Trace

Source: Shokraii (1977); Clarke et al. (1976).

Table 11.3 Amino acid profile of two varieties (‘Ohadi’ from Iran and ‘Kerman’ from the USA) of pistachio nut Percent total amino acids

Amino acid

Alanine Arginine Aspartic acid Cystine Glutamic acid Glycine Histidine lsoleucine Leucine Lysine Methionine Phenyl-alanine Proline Serine Threonine Tryptophan Tyrosine Valine

Ohadi

Kerman

4.00 9.70 8.80 2.60 20.60 4.50 2.30 4.10 7.00 5.70 1.50 4.90 3.80 5.60 3.20 1.40 2.90 5.60

5.46 1.91 9.54 1.72 22.70 5.23 1.94 4.79 8.11 11.04 2.07 4.74 4.64 3.71 3.95 _____ 2.80 6.46

Source: Shokraii (1977); Clarke et al. (1976).

blue and purple colors of various fruits and many colorful vegetables. Pistachio anthocyanins are present as glycosides of cyanidin and include cyanidin-3galactoside (major; 696 μg.g−1) and cyanidin-3-glucoside (minor; 209 μg.g−1) (Seeram et al., 2006).

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Many studies have indicated that a diet containing pistachio nut can reduce the risk of coronary heart disease (CHD). Aside from their mono-unsaturated fatty acids and fibers, pistachio nuts are rich sources of antioxidant phytochemicals, which promote heart health by inhibiting the absorption of cholesterol from the intestine through direct competition with uptake mechanisms. Recent studies have shown that a diet that incorporates pistachio nuts can reduce the total cholesterol, total cholesterol/HDL cholesterol ratio, and low density lipoprotein/ high density lipoprotein ratio significantly, and also decrease the plasma malondialdehyde, an important indicator of lipid peroxidation (Sheridan et al., 2007). Several studies have indicated that regular consumption of pistachio nuts does not lead to remarkable weight gain. The results have shown that those who eat pistachio nut more frequently are leaner and have a lower body mass index (BMI) than the infrequent nut eaters, even though their energy intake is higher (Cotton et al., 2004). It has also been proven that regular consumption of pistachio nuts lowers the blood pressure and therefore might be recommended for hypertension. They reduce the absorption of glucose and lower the blood sugar. As a result of many vitamins and minerals, they are especially recommended for children for a healthy physical and mental development. Pistachio nuts are also a good source of vitamin E which boosts the immune system and alleviates fatigue. These days, it is strongly recommended to consume foods with minimal processing in order to gain maximum health benefits. Other than drying at low temperatures and sometimes roasting, no other treatment is commonly applied to pistachio. Therefore, fatty acids, minerals, vitamins and other nutritional compounds are retained at a maximum level. Pistachios have been reported as a folk remedy for scirrhus of the liver, abdominal ailments, abscess, amenorrhea, bruises, sores, trauma and dysentery. 11.1.7 Physical, mechanical and thermal properties of pistachio nuts Physical, mechanical and thermal properties of pistachio nut and its kernel are important in the design of equipment for harvesting, handling, processing, transportation, sorting, separation, packaging and storage. Designing equipment without taking these into consideration may yield poor results. Size, shape and dimensions of pistachio nut and kernel are important in sizing, sorting, sieving and other separation processes. Densities of pistachio nut and kernel are necessary to design the equipment for processing and storage such as hullers, dryers and bins. The porosity affects the resistance to airflow through bulk pistachio nuts and packing characteristics. Physical properties also affect the hydrodynamic and pneumatic conveying characteristics of pistachio nut and kernel. During harvesting, handling, processing and storage of pistachio nut, the product exerts frictional forces on machinery components or storage structures. The magnitude of these frictional forces affects the amount of power required to

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Fig. 11.5 Schematic of three major perpendicular dimensions of pistachio. The dotted lines represent the kernel inside the nut.

convey the material. The static coefficient of friction is useful to determine the angle at which chutes must be positioned to achieve a consistent flow of material through the chute. Terminal velocity is very critical in the design of the pneumatic conveyor, transporting pistachio nut and kernel using air and separation of pistachio nut and kernel from undesirable materials such as shells, hulls, leaves, blank pistachios and small branches. The terminal velocity is affected by the density, shape, size and moisture content of pistachio nuts. Mechanical properties such as rupture force, deformation and rupture energy are used to design equipment for shelling and grinding of pistachio nut. Thermal properties of pistachio nut, in particular specific heat, are used to design a new unit operation or to analyze current processes such as drying and storage. Moisture content and variety are the most important factors affecting the physical, mechanical and thermal properties of pistachio nut and kernel. Table 11.4 describes some physical properties of pistachio nut as a function of moisture content. The mathematical relationship between physical properties and moisture content are also presented in this table. In these measurements, length, width and height have been defined as the distance from the calyx end to the stem, the maximum diameter, and the distance from the highest point to the lowest point of pistachio nut when positioned on a horizontal plate, respectively (Fig. 11.5).

11.2

Physiological disorders

Blanking, non splits and alternate bearing are the three main physiological disorders related to fruiting of pistachio nuts. Blanks are nuts without kernels and occur when the embryo fails to develop and can take place during nut setting and nut filling. Promotion of shell development from ovary tissues without successful fertilization causes blanking in nut setting phase. Blanking may also occur during kernel growth when the tree cannot provide sufficient assimilate to complete

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Length (L) (mm) Width (W) (mm) Height (H) (mm) Sphericity (φ) (%) Unit mass (M) (g) Volume (V) (cm3) True density (ρt) (kg m−3) Bulk density (ρb) (kg m−3) Porosity (ε) (%) Emptying angle of repose (θe) (°) Filling angle of repose (θf) (°) Static coefficient of friction for rubber (μ) Rupture force (N) along the length (FL) Rupture force (N) along the width (FW) Rupture force (N) along the height (FH) Rupture energy (mJ) along the length (EL) Rupture energy (mJ) along the width (EW) 58.61–42.94 37.24–25.57 42.65–35.14 69.17–46.95 40.48–28.73

6.31–35.57

FW = −0.8965 Mc + 97.24

90.31–60.57

112.31–82.59 FH = −0.9348 Mc + 118.08 6.31–35.57 256.78–182.66 EL = −2.3512 Mc + 272.63 6.31–35.57 157.46–101.39 EW = −1.7335 Mc + 170.98 6.31–35.57

5.77–39.11

5.77–39.11

5.77–39.11

5.77–39.11

l = 0.0170Mc + 12.9176 w = 0.0447Mc + 8.8088 h = 0.0384Mc + 8.6632 φ = 0.0026Mc + 0.7432 M = 0.520 + 0.011Mc V = 0.622 + 0.011Mc ρt = 858.7 + 0.13Mc ρb = 572.73 + 0.19Mc ε = 33.24–0.04Mc θe = 0.1367Mc + 25.330

Equation

(Continued)

Ew = −0.3667 Mc + 42.88

El = −0.6261 Mc + 72.75

Fh = −0.2440 Mc + 44.42

Fw = −0.3398 Mc + 38.90

Fl = −0.4946 Mc + 61.93

24.50–27.02 θf = 0.0855Mc + 24.030 0.393–0.647 μ = 0.0083Mc + 0.3505

136.23–98.84 FL = −1.0904 Mc + 143.01 6.31–35.57

5.33–34.78 5.44–34.78

5.77–39.11

θf = 0.0896Mc + 15.155 μ = 0.0044Mc + 0.4687

13.1–13.6 8.1–9.8 8.8–9.7 82.5–74.8 0.547–0.873 0.634–1.013 860–864 574–581 61.65–49.86 26.17–30.39

15.72–18.47 0.497–0.633

5.30–34.80 5.30–34.80 5.30–34.80 5.30–34.80 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.78

5.44–34.78 5.44–34.78

L = 0.0335Mc + 16.6630 W = 0.0178Mc + 11.8664 H = 0.0251Mc + 11.954 ----------------M = 0.94 + 0.019Mc V = 1.13 + 0.020Mc ρt = 857.6 + 0.29Mc ρb = 551.38 + 2.56Mc ε = 35.30–0.24Mc θe = 0.2148Mc + 20.345

16.9–17.8 12.1–12.7 12.3–12.7 79.3–79.8 1.105–1.680 1.291–1.873 860–869 573–649 60.59–47.75 21.54–28.32

Value

5.40–34.80 5.40–34.80 5.40–34.80 5.40–34.80 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.33–34.77 5.44–34.78

MC (% w.b.)

Equation

MC (% w.b.)

Value

Kernel

Nut

Some physical, mechanical and thermal properties of pistachio nut and kernel of the ‘Ohadi’ variety as function of moisture content

Property (unit)

Table 11.4

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Continued

9.8–12.0 0.705–2.567 2.4–1.1 38.26 43.54

4.00–36.30 5.12–33.86

5.40–34.80

56.35–42.28

Value

Eh = −0.4929 Mc + 59.83

Equation

S = −0.0407Mc + 3.0342

--------------- ----------------- -----------------

Vt = 0.23Mc + 10.56 3.50–36.30 9.0–10.0 Vt = 0.17Mc + 9.53 Cp = 0.9310 ln(Mc)–0.7748 --------------- ----------------- -----------------

213.92–145.07 EH = −2.1427 Mc + 226.97 6.31–35.57

5.77–39.11

MC (% w.b.)

Equation

MC (% w.b.)

Value

Kernel

Nut

MC = moisture content (% w.b.). Source: Kashaninejad et al. (2006); Razavi and Taghizadeh (2007); Razavi et al. (2007a; 2007b; 2007c; 2007d); Nazari Galedar et al. (2009).

Rupture energy (mJ) along the height (EH) Terminal velocity (Vt) (m s−1) Specific heat (Cp) (kJ kgK−1) at 25 °C Shell splitting (S ) (mm) Hull/nut ratio Shell/nut ratio

Property (unit)

Table 11.4

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development of its entire crop. Insufficient irrigation and inadequate boron leaf levels were also reported as causes of blank formation in pistachio nuts (Freeman and Ferguson, 1995). Shell splitting is a unique characteristic of pistachio nuts compared with other nuts and significantly important for pistachio quality because it affects the price and marketability of the product. Splitting is one of the maturation criteria and continues with kernel growth through maturity. Nut splitting can be reduced by water stress late in the growing season. Harvest time and boron nutrition are also important factors affecting nut splitting. Heating in the drying process will decrease the moisture content of shells and increase the splitting of nuts. Non-split nuts are usually separated after processing of fresh nuts and cracked and sold as kernels for processing into mixed nuts or ice cream. Pistachios are strongly alternate bearing and produce heavy crops every other year, fluctuating with no or little crops in ‘off’ years. Carbohydrate competition is probably the cause of this phenomenon so that carbohydrate depletion prevents floral initiation in the summer of an ‘on’ year. Inflorescence buds develop partially but abscise during heavy crop years and inhibit to produce a heavy crop in the next year. Like blank production, rootstock has a significant effect on alternate bearing. Studies indicated that blanking and shells splitting are related to ‘on’ and ‘off’ crop years. Blanking is much higher in ‘off’ years and non-split nuts are much more common in ‘on’ years, while crop load is much higher in ‘on’ years (Freeman and Ferguson, 1995).

11.3

Postharvest pathology and mycotoxin contamination

Several fungi have been identified to infect pistachios and some of them cause considerable damage to the hull and kernel. Alternaria causes black spots on the hull that are sometimes surrounded by red margins causing shell staining and mold in the kernel in early split nuts or fruits with cracked hull. Saprophytic fungi such as Alternaria, Aspergillus, Cladosporium, Fusarium and Penicillium are associated with shell staining, consequently infecting and causing decay to kernels of pistachio nuts (Michailides et al., 1995). The greatest postharvest damage of pistachio nuts is from Aspergillus flavus and Aspergillus parasiticus. These fungi produce aflatoxin. They are among the most potent mutagenic substances known to result in liver cancer. As the pistachio nuts grow on the trees, aflatoxin producing fungi can infect the kernels. However, the hull covering the shell usually remains intact and protects the kernel from invasion by molds and insects. Damaged hulls or nuts with poor protection by hulls are most prone to fungal infection. Sometimes the hull is attached to the shell and both split together. This hull rupture often referred to as ‘early splitting’, exposes the kernel to mold and insect infestations. The proportion of early split pistachio nuts is usually 1–5%, although it can be as high as 30% in some situations. The navel orangeworm (Amyelois transitella) is the major insect problem that usually infests nuts with ruptured hulls, and high levels of aflatoxin

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contamination have been reported in insect-damaged kernels. Doster and Michailides (1994) in their study on California pistachios reported that early split nuts had over 99% of the aflatoxin detected and navel orangeworm infected nuts had substantially more infection by several Aspergillus species as well as over 84% of the aflatoxin detected. Very late harvest, bird damage and cracking also result in hull rupture and infection of kernels with Aspergillus molds at low levels. In addition to increasing aflatoxin production in infected nuts after harvest, early split and damaged nuts that are not infected on the trees may become infected during harvest, transport, handling and storage. High temperature and humidity within the bulk pistachio nuts during transport and storage can provide the best conditions for infection of early split and damaged nuts. Infected nuts will provide a source of inoculum for the spread of fungi to sound nuts under inappropriate storage conditions or during inadequate processing, thus increasing the incidence and level of aflatoxin contamination. Mold contamination and aflatoxin production can be prevented to ensure that contaminated nuts do not enter the food chain (Joint FAO/WHO Food Standards Program, 2002). This prevention program should consider the different steps before and after harvest until the nuts reach the consumers. Using cultivars with lower early split nuts, reducing inoculum sources such as fallen fruits and inflorescence from trees, burying or removing pistachio litter, manipulation of irrigation, application of microorganisms or saprophytic yeasts as biocontrol agents and minimizing insect damage such as navel orangeworm are the main approaches to prevent contamination of nuts before harvest. At harvest, pistachios should not be in contact with the orchard floor to avoid infection. Delaying harvest should be avoided to prevent more aflatoxin production in the infected pistachio nuts. The nuts should be transported to the processing plant and hulled and dried as soon as possible after harvest because of high temperature and relative humidity within the bulk pistachio nuts that provide the best conditions for further contamination. If temporary storage of fresh pistachio nuts at the processing plant is necessary, they should be stored at 0 °C and lower than 70% relative humidity. Drying at high temperature will probably kill the aflatoxin-producing fungi but it has little effect on the aflatoxin already present. Drying to appropriate moisture content (5–7%) or water activity (less than 0.7) will prevent the growth of these fungi. Aflatoxin producing fungi will not be able to grow and produce aflatoxin in dried pistachio nuts stored at 25 °C and relative humidity lower than 70% for a long time. Since nuts infected by molds and contaminated with aflatoxin have some distinct physical properties such as dark stain and hull adhesion compared to sound nuts, they can be easily machine sorted.

11.4

Postharvest handling practices

11.4.1 Maturity criteria and harvest time Although pistachios are traditionally harvested when the hull separates easily from the shell, ideal harvest time and optimum maturity is determined by

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several criteria such as compositional and visible changes. Moisture content of the kernels decreases continually throughout maturation and stabilizes at full maturity, while fresh and dry weights of the kernel increase with maturity and reach a peak at harvest time. Respiration rate and total protein content decrease throughout maturation, and ether-extractable fat and total sugar content reach a peak at optimum maturity. These compositional changes coincide with shell splitting and changing from translucent to opaque, although they are invisible because the fleshy hull covers the shell in the developing nuts. Color change of the hull is a visible evidence of maturation, which is green in immature nuts and progresses to ivory to rose with optimum maturation (Labavitch et al., 1982). The percent of blank and immature fruits decrease throughout maturation and is minimal at optimum maturity. When fully mature, the nut will be separated from the hull easily when the fruit is pressed between the thumb and fingers at the hull’s distal end. Activity in the abscission zones between the nuts and the rachis is another evidence of maturation. At this status, fruit removal force will decrease and nuts will easily detach by gentle shaking (Ferguson et al., 1995). Like other fruits, maturation does not occur evenly throughout the tree. Therefore, the optimum harvest time is when the maturity criteria are observed at 70 to 80% of fruits. Based on all mentioned criteria, mid- to end of September was determined as the best harvest time for ‘Ohadi’, ‘Kalle-Ghouchi’, ‘Ahmad-Aghaei’ and ‘Badami’ varieties in Kerman province, Iran. The harvest time for these varieties may be different in other regions. Optimum harvest time is very important in maintaining nut quality; harvest should not be delayed because this will increase losses to navel orangeworm (NOW, Amyelois transitella), birds and fungi (in particular Aspergillus flavus), as well as shell staining due to breakdown of the phenolic compound-rich hull tissues. Early harvest leads to weight loss and decreases the shelf life of freshly harvested pistachios. 11.4.2 Harvest operations Pistachio trees are grown on traditional plantations and the lack of space between trees and rows necessitates harvesting by hand in Iran, Turkey and Syria. Pistachio clusters are harvested by laborers and dumped into sacks. The sacks are collected into plastic bins and transported to processing plants by trucks or trailers. In the United States, young trees (less than six years old) are hand harvested by knocking the trunk or striking the branches onto tarps spread under the trees, while mature pistachios are mechanically harvested onto a catching frame. Since orchard soils have potential to contaminate the pistachios with Aspergillus flavus, it is very important to prevent dropping the pistachios to the floor during mechanical harvesting. As well, any mechanical damage during harvesting should be avoided because pistachio hulls are fragile and susceptible to injury; shell staining will intensively increase in pistachios with damaged hulls. Pistachios also require more careful handling due to their higher moisture content at harvest than other tree nuts.

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11.4.3 Postharvest storage Shell staining and decay incidence are the major deterioration after harvest if the nuts are left in the hull for a long time, particularly at high temperatures. Most of the heating of bulk freshly harvested pistachio nuts is due to respiration. The maximum respiration rate of unhulled pistachio nuts is 125 mLCO2.kg−1.h−1 at 20 °C (Thompson et al., 1997). This level of respiration would produce a heating rate of about 0.7 °C per hour. Roughly handled, pistachio nuts can be held for at least 32 hours at 25 °C without significant increases in light or dark shell staining. At 30 and 40 °C, shell staining can occur in 24 hours and less than 16 hours, respectively, and accelerates specially beyond these time durations. Gently handled pistachio nuts with intact hulls may be held for up to 48 hours at ambient conditions without significant increase in staining. Ambient air circulation in bulk pistachio nuts or keeping them in a cold place are the best methods to prevent heat increase and retard shell staining if delays are unavoidable before processing (Thompson et al., 1997). Fresh unhulled pistachio nuts can be stored up to six weeks at 0 °C and 70–75% relative humidity without any significant effects on appearance, flavor quality, composition and hull removal. Storage at higher temperatures results in more incidence of surface molds and shell staining. An adequate air flow rate (0.1 Ls−1kg−1) through nuts during storage is essential to minimize losses. Sorting the nuts before storage to eliminate defective nuts (which are much more susceptible to decay), leaves and debris helps to increase the shelf life of fresh pistachio nuts. Hulled pistachio nuts have a shorter shelf life because the hull protects the nut from decay organisms without affecting shell quality. Hulled fresh pistachio nuts can be held for up to three weeks at the best storage conditions (0 °C and 40–50% relative humidity). Increasing the relative humidity to 90% shortens the storage of hulled pistachio nuts to 2 weeks at 0 °C, 1 week at 5 °C, 4 days at 10 °C, 2 days at 20 °C and 1 day at 30 °C. After two weeks storage at 0 °C and less than 10% relative humidity, the moisture content decreases to 7% and hulled nuts are almost completely dry. Although freezing has no significant effects on kernel texture, its influence on flavor quality eliminate it as an alternative for extending shelf life of fresh hulled nuts (Kader et al., 1978; 1979).

11.5

Processing of fresh pistachio nuts

Proper and quick processing after harvest is very important for pistachio quality and its marketability. For hundreds of years, pistachio nuts were processed manually. After harvesting the ripe pistachios, are hulled by hand. Workers perform this job so fast and skillfully that it is very difficult to see the procedure even at close observation. In some regions pistachio nuts are hulled right away after harvest, but in other regions they are dried in the hull for later hulling at a convenient time. Sometimes the pistachio nuts are immersed in water to separate the hull easily when squeezed between fingers. Pistachio nuts are then spread on

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a concrete or earth floor in the sun to dry. These processing methods usually result in nuts with stained shells and lower quality. During the last 30 years, traditional methods have extensively been improved in the leading producer countries and now pistachios are mechanically hulled and processed within a short time. Figure 11.6 indicates the processing procedures using two methods when freshly harvested pistachios arrive at the processing plant (Nakhaeinejad, 1998). Separation of blank pistachios is the main difference in these methods. Further processing of dried pistachio nuts may be accomplished immediately at harvest season or later as indicated in Fig. 11.7. 11.5.1 Hulling Hulling must be accomplished as soon as possible to reduce the chances for fungal growth and to avoid shell staining. The hull of the freshly harvested and mature pistachio nuts slip off fairly easily. Generally, different types of machines are used satisfactorily for hulling pistachios. Cylindrical hullers are more popular and economic and are used at different sizes and capacities to hull pistachios in various regions of Iran. The cylindrical huller consists of two concentric metallic cylinders and the inner cylinder rotates inside the stationary outer cylinder. The outside surface of the inner cylinder and inside surface of the outer cylinder are covered by parallel rings or slabs that are positioned at certain points. Pistachio nuts are fed continuously between the two cylinders and the hulls are separated from nuts

Fig. 11.6 Scheme processing procedures of freshly harvested pistachio nut. Left: processing by air flow tank. Right: processing by water float tank.

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Fig. 11.7

Processing procedures of dried pistachio nut.

after impacting the rings. Basically, this is a dry hulling method wherein pistachio nuts are hulled without water, an important advantage for pistachio growers and processors in dry regions. In rubber machines, the pistachios are rubbed between two rubber drums and the hulls are separated from the nuts. This machine does not damage mature pistachios but is unable to peel unripe pistachios, which are easily separated in the next stages. The abrasive peeler is another machine that produces an attractive product but is limited to a batch of nuts at a time. This small machine is suitable for small-scale production because it is unable to hull large volumes of pistachios that are being produced currently in pistachio orchards. It consists of a vertical cylinder with its inside coated by an abrasive material; a rotating disc at the bottom of the cylinder is also coated with the same abrasive. Pistachios are thrown by the centrifugal force of the rotating disc against the abrasive wall surface; the disintegrated hulls are removed from the peeler by a water stream that is introduced from the top of the cylinder. In the United States, pistachios are hulled in machines that consist of two parallel rubberized belts rotating in the same direction but at different speeds. After the hulling process, undesirable materials including hulls, branches, leaves, shells, broken nuts and kernels, blank and unripe pistachios, unpeeled pistachios and small pistachios are separated from the hulled nuts quickly to promote quality and marketability of the final product and also to avoid fungal growth. The separation of undesirable materials takes place at several stages using proper devices such as air leg, water or air flow tank, a stick tight separator and picking or inspection tables. 11.5.2 Trash and debris removal Although most of the hulls, branches and leaves are separated from the nuts in the hulling process, a small amount of hull pieces, debris and bunches remain; they

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are separated at this stage using the air leg or air flow system. The remaining trash and debris do not exceed more than one percent of total materials separated in the huller. This process is based on the capacity of an air stream to lift particles against gravity. The effect depends on air velocity and the particle moisture content, shape, size and specific gravity. This apparatus contains a vertical column and a blower at the bottom that regulates the air flow rate and velocity. The air flows upward in the column from the bottom to the top and fractionates the undesirable materials and blank pistachios from hulled nuts based on their terminal velocity. 11.5.3 Washing Shell appearance is one of the most important characteristics of pistachio quality and marketability. Hull latex extracted after the hulling process includes some components that cause blemished appearance and consequently raise the cost and time for separation of stained nuts after the drying process. Shell staining can be greatly decreased by appropriately washing the hulled nuts and removing the latex from the shell after the hulling process. As the pistachios are moved forward in a layer by a particular steel conveyor during the washing process, high pressure water is sprayed on the pistachios. In addition to cleaning the nuts and removing the latex from shells, the remaining debris and trashes are also separated. Water consumption is minimal in this washing process which is an advantage for dry regions. 11.5.4 Separation of blank pistachio nuts The kernels of blank and immature pistachio nuts are usually not fully developed and most of them are empty. Thus, the ratio of kernel to nut and the mass of 100 nuts, particularly, the specific gravity of blank and immature pistachios is lower than fully mature pistachios. Water has been used as a media for separation of blank pistachios from ripe ones for many years. When hulled pistachio nuts after the washing process are immersed in the water tank, all blank pistachios will float and most (about 60 to 80%) of the split and fully mature nuts will sink. The floaters also consist of unsplit nuts with less than 15% meat content (Woodroof, 1979). The air entrapped between the shell and the kernel of some fully split pistachio nuts reduces their specific gravity and consequently they float with blank pistachios. Separation efficiency can be improved by the installation of a stirrer or propeller in the water tank to remove the air entrapped between the shell and the kernel in the split and mature nuts. The floaters will be removed by water stream from the top of water tank and the sinkers will be taken out from the bottom of the tank employing a steel conveyor. In some processing plants or regions where enough water is not available for the separation of blank pistachios, this process is accomplished by an air flow float tank called a ‘dry tank’ machine. Blank and immature pistachio nuts, small, undersized and broken pistachios, debris and tiny trashes are separated in this machine using air flow and vibration.

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11.5.5 Drying Drying is an important operation in pistachio processing. The moisture content which is as high as 40% (wet basis) in the freshly harvested nuts is reduced to about 4–6%. Drying time is a function of many parameters including dryer air temperature, ambient relative humidity, initial moisture content of pistachio nuts, drying stage, variety and drying method. Figure 11.8 shows the drying time and behavior of pistachio nut (‘Ohadi’ variety) at different temperatures in a thin layer dryer (Kashaninejad et al., 2007). The increase in the drying air temperature decreases drying time rapidly and consequently increases the drying rate. Drying curves shown in Fig. 11.9 demonstrate that drying of pistachio nuts occurs in the falling rate period. At higher air temperatures, two distinct drying periods can be detected, namely, an initial transitional nut warm-up period wherein a slight increase in the drying rate takes place, and a falling rate period characterized by a rapid decrease of the drying rate. At lower air temperatures, the falling rate period is only detected which suggests predominance of the internal diffusion phenomenon as the mass transfer controlling process. In the falling rate period, a high initial drying rate (with higher rates at higher temperatures) is observed followed by a gradual decrease as the material approaches the dried state. Initially, the drying rate is higher because the initial water for evaporation comes from regions near the surface. As the drying progresses, the drying rate decreases with decrease of moisture content because the water to be evaporated comes from parenchymal cells within the structure and must be transported to the surface. The falling rate region is indicative of an increased resistance to both heat and mass transfer through the inner cells. Table 11.5 shows the characteristics of different commercial dryers that are used for drying of pistachio nuts. Nowadays most processors prefer to use a

Fig. 11.8 Drying pattern of pistachio nut (‘Ohadi’ variety) at different air temperatures (air velocity = 1.5 m/s, relative humidity = 20%).

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Fig. 11.9 Drying rate of pistachio nut (‘Ohadi’ variety) at different air temperatures (air velocity = 1.5 m/s; relative humidity = 20%).

Table 11.5

Characteristics of commercial pistachio dryers

Dryer type

Average air temperature (°C)

Drying time (h)

Dimensions (m)

Bed depth (cm)

First stage

Second stage

Flat bottomed bin dryer

65

-------------

8

L = 2.0 W = 1.2 H = 0.5

40

Continuous column dryer

45

40

10

L = 5.0 W = 2.0 H = 4.0

30

Continuous belt dryer

55

40

9

L = 10.5 W = 6.7 H = 6.5

30

Vertical cylindrical dryer

55

-------------

8

H = 4.0 D1 = 0.5 D2 = 1.5

50

Funnel cylindrical dryer

80

-------------

5.5

H = 3.5 D = 2.0

300

L: length, W: width, H: height, D1: internal cylinder diameter, D2: external cylinder diameter, D: diameter.

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two-stage drying process as it uses less energy and increases the uniformity of drying of the nuts compared with the single stage process. Chemical composition and quality of pistachio nuts do not change significantly during the drying process but shell splitting increases and some of the closed shells split during drying because of moisture loss. In dryers with high nut depth, the pressure exerted by nuts in the upper layers may prevent the splitting of the shells in the lower layers (Kashaninejad et al., 2003). Drying air temperatures above 80 °C cause shells to split so widely that the nut drops out. Appropriate air temperature and uniform air flow distribution is very important to prevent potential of fungal growth during the early stage of drying. In some processing plants, sun drying may be used. Pistachio nuts are spread out in a thin layer 2–3 cm thick on a concrete floor under the sun and this requires about 48 hours at temperatures near 26 °C. Sun drying should be accomplished with protective cover to prevent access by birds and rodents. Pistachio nuts are planted in regions with plenty of sunshine during the harvest season. Therefore, solar energy is an advantageous alternative for drying of pistachio nuts in order to decrease the dependence of the drying process on fossil fuels. Ghazanfari et al. (2003) dried pistachio nuts by a forced air solar dryer to 6% moisture content for 36 hours. The maximum temperature in the solar collector reported was 56 °C, which was 20 °C above the ambient temperature. When air is forced through a layer of bulk pistachio nuts, resistance to the flow (the so-called pressure drop) develops as a result of energy lost through friction and turbulence. The resistance to airflow through bulk pistachio nut is an essential parameter to optimally design the forced ventilation systems for drying and also cooling the stored bulk. As well, the uniform and proper airflow distribution can prevent fungal growth during the drying process. Figure 11.10 shows the resistance

Fig. 11.10

Pressure drop of pistachio nut at different airflow rates and moisture contents.

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of bulk pistachio nuts at various airflow rates and moisture contents. Airflow resistance across a column of pistachio nuts increases linearly with increasing depth. The pressure drop through pistachio nut beds increases more rapidly with increasing airflow rate compared with bed depth (Kashaninejad et al., 2010). Airflow rate, moisture content and fill method affect the pressure drop, however airflow rate and fill method have greater influence on pressure drop of pistachio nut than moisture content. An increase in the moisture content in the range of 4.08–38.40% (wet basis) results in a 55% increase in the pressure drop across pistachio nut beds. The dense fill increases the bulk density which results in an increase in the airflow resistance of bulk pistachio nuts by 97% than that of loose fill (Kashaninejad and Tabil, 2009). 11.5.6 Storage of dried pistachio nuts Generally, nuts may be held for a long time (up to 2–5 years) if they are stored under optimum conditions but at unfavorable storage conditions, they may become inedible even within one month because of mold growth, off-flavor, rancidity, discoloration, absorption of undesirable flavors and insect infestation. Pistachio nuts dried to appropriate moisture content (4–6%) are very stable and can be stored for up to one year at 20 °C and 65–70% relative humidity without significant losses in quality attributes (Kader et al., 1982). No differences in chemical composition and sensory attributes were observed among nuts stored at different temperatures (0, 5, 10, 20 and 30 °C) for 12 months. Nuts held at 30 °C had lower moisture content and higher sugar content and rancid flavor than those stored at lower temperatures. Long storage potential of pistachio nut is a result of high oleic acid, natural antioxidants and reduction of moisture to monolayer moisture content during the drying process. Pistachios are more stable to rancidity and have a longer storage potential than other tree nuts such as almonds, pecans or walnuts. All these nuts are high in fat content, but walnut and pecan oils have a much higher content of polyunsaturated fatty acids than pistachio oil. For longer storage of pistachio nuts, low temperatures (between 0–10 °C) are recommended. Exclusion of oxygen, insect control through fumigation, vacuum packaging or N2 injection in packages and controlled atmospheres can maintain nut quality during storage. Storage under high concentration of CO2 (98%) and reduced O2 (less than 0.5%) provides good stability in terms of fatty acid loss and formation of peroxide and free fatty acids (Maskan and Karatas, 1998). Oxygen scavenger packaging is an efficient method to eliminate the oxygen content and retard the oxidation of pistachio nut during long storage. It has been reported that pistachio nuts stored in an oxygen scavenger system have a lower hexanal content than those in vacuum and atmospheric packaging (Leufven et al., 2007). Hexanal is an indicator of oxidation progress and is applied in various products to monitor quality deterioration. Wheat starch-based edible films are alternative packaging materials for pistachio nuts or kernels to improve the shelf life. The main advantage of edible films is the reduction of synthetic packaging materials, but they also retard peroxide formation and minimize water absorption during storage. Addition of

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PEG (polyethylene glycol) to wheat starch films enhances tensile and mechanical properties of the films (Forghani, 2008). Insect infestation is a potentially important problem during storage because the fungal infections often accompany insect damage. Fumigation with methyl bromide or phosphine has been used for disinfestation. Storage of nuts at temperatures near freezing (0 °C) or in 0.5% oxygen and 10% carbon dioxide also effectively kill all insects.

11.6

Processing of dried pistachio nuts

11.6.1 Separation of split from non-split pistachio nuts Non-splitting is one of the shell defects that affects marketability and the price of processed product, therefore the non-split nuts should be separated from split nuts before selling. Although some of the closed shells split during the drying process, non-splitting may comprise up to 30% depending on the variety. Closed shell nuts are separated from the open shell ones by mechanical devices called pinpicker or needle picking drums. In this machine, raw nuts are fed into a rotating drum that is covered by tiny needles or pins. Open shell nuts are picked by needles and lifted away with drum rotation and separated at the top of the drum by a brush. Closed shells nuts that are not picked by needles pass through the bottom of the drum and are collected at the other side of the rotating drum. 11.6.2 Grading of pistachio nuts Grading requirements for pistachio nuts in the shell, shelled pistachio nuts, artificially opened pistachio nuts and non-split pistachio nuts are available and used by the industry. The basic requirements of grading should be that nuts are free from foreign materials, loose kernels, shell pieces, particle and dust, and blank nuts. The grading criteria are divided into shell and kernel defects. Shell defects include any blemish affecting the appearance, edibility and/or marketing of pistachio nuts such as adhering hull material, light or dark stained shell, nonsplitting or splitting other than the suture, deformity and/or other damage. Kernel defects include immature kernels, rancidity, mold or decay and any damage or evidence of insects. Size and degree of dryness are also important quality attributes affecting grading. 11.6.3 Salting and roasting Pistachio nuts are mostly consumed salted and roasted in-shell. Salting and roasting tremendously enhance the flavor, color and texture of pistachio nuts and increase overall palatability of the valued products. Improvement of sensory attributes of pistachio nuts during roasting is a result of non-enzymatic browning or Maillard reaction which takes place between the reducing sugars and nitrogenous compounds, in particular amino acids and proteins. Nuts become

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Fig. 11.11

243

Roasting procedures in a continuous nut roaster.

more crumbly and brittle during the roasting process, which are typical characteristics of roasted products. Figure 11.11 shows the roasting process diagram in a continuous pistachio roaster (Dadgar, 1998). Pistachio nuts are salted by soaking in salt solution in a rotary salting machine and rotation of the drum and appropriate residence time provide uniform salting. Seyhan (2003) reported that 20% (W/V) salt solution and 20 min soaking may be used for salting of pistachio nuts. The higher concentration of salt solution results in lower moisture absorption throughout the soaking process. Other additives such as lemon juice or saffron may be added to the salt solution to enhance flavor of the roasted product. The excess salt solution entrapped between the shell and the kernel is removed by vibration to promote efficiency of the dryer. As the pistachio nuts are turned around and moved forward on the steel belt dryer, surface salt solution and the moisture absorbed during salting are evaporated. Then pre-dried pistachio nuts are fed to the top of a threelayer steel belt roaster and discharged from the bottom to the steel belt cooler. Pistachio nuts are roasted at 145 °C and cooled at ambient temperature. The outlet air of the cooler is utilized in the dryer to improve efficiency of the system. Kashani and Valadon (1983, 1984) have investigated the effect of the common roasting method (drying at 70 °C for 1 hr and roasting at 145 °C for 20 min) on components and quality of pistachio nut. After roasting, an obvious increase in fatty acids (from 2.7 to 5.5 mg.g−1) and phosphatidic acid (from 0.8 to 2.7 mg.g−1) and a slight decrease in triglycerides (from 437.6 to 434.9 mg−1g) and choline compounds took place, while most of the other lipid components did not change. Although iodine value or malonaldehyde did not change significantly, peroxide value clearly increased (from 0.73 to 1.04 meqkg−1) during roasting. Increase in the peroxide value demonstrates that some of the pistachio oil was degraded during roasting. After roasting, the total available carbohydrates, starch, dextrin, and in particular total free sugars decreased significantly. Reducing sugars such as glucose and fructose almost disappeared. No significant effect was observed in

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total protein, but about 40% of free amino acids were degraded. Some free amino acids such as cysteine, histidine, arginine, methionine and tyrosine disappeared totally. Reduction in free amino acids and reducing sugars might be a result of taking part in a Maillard reaction.

11.7

References

Ak B E and Açar I (2001), ‘Pistachio production and cultivated varieties grown in Turkey’, in Padulosi S and Hadj-Hassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. Banifacio P (1942), II Pistacchio: Coltivazione, Commercio, Uso, Rome, Ramo Editoriale degli Agricoltori. Brothwell D and Brothwell P (1969), Food in Antiquity: A Survey of the Diet of Early Peoples, New York, Frederik A. Praeger. Clarke J A, Brar G S and Procopiou J (1976), ‘Fatty acid, carbohydrate and amino acid composition of pistachio (Pistacia vera) kernels’, Pl Food Hum Nutr, 25 (3/4), 219–225. Cotton P A, Subar A F, Friday J E and Cook A (2004), ‘Dietary sources of nutrients among US adults, 1994 to 1996’, J Am Diet Assoc, 104, 921–930. Crane J C (1978), ‘Quality of pistachio nuts as affected by time of harvest’, J Am Soc Hort Sci, 103, 332–333. Crane J C and Iwakiri B T (1981), ‘Morphology and reproduction of pistachio’, Hort Rev, 13, 376–393. Dadgar F (1998), Salting and Roasting Pistachios in Iran, Kerman, Momtazan Industrial Co. Doster M A and Michailaides T J (1994), ‘Aspergillus molds and aflatoxins in pistachio nuts in California’, Phytopathol, 84, 583–590. Duke J A (2001), Handbook of Nuts, Boca Raton, Florida, CRC Press. Esmail-pour A (2001), ‘Distribution, use and conservation of pistachio in Iran’, in Padulosi S and Hadj-Hassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. FAOSTAT (2009), FAOSTAT database, FAO statistics database on the World Wide Web. Available from: http://apps.fao.org (accessed December 2009). Ferguson L, Kader A A and Thompson J (1995), ‘Harvesting, transporting, processing and grading’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 110–114. Forghani M (2008), ‘Moisture uptake, rancidity and physical properties of wheat starchbased edible films as a new package’, Int J Food Safety, 10, 65–71. Freeman M and Ferguson L (1995), ‘Factors affecting splitting and blanking’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 106–109. Ghazanfari A, Tabil L G and Sokhansanj S (2003), ‘Evaluating a solar dryer for in-shell drying of split pistachio nuts’, Dry Technol, 21 (7), 1357–1368. Hadj-Hassan A (2001), ‘Cultivated Syrian pistachio varieties’, in Padulosi S and HadjHassan A, Project on Underutilized Mediterranean Species. Pistacia: Towards a Comprehensive Documentation of Distribution and Use of its Genetic Diversity in Central & West Asia, North Africa and Mediterranean Europe, Rome, Italy, IPGRI. Hendricks L and Ferguson L (1995), ‘The pistachio tree’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 7–9.

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Joint FAO/WHO Food Standards Program (2002), Discussion paper on aflatoxins in pistachios, 34th session, Rotterdam, The Netherlands, 11–15 March. Joret C (1976), Les plantes dans l’antiquité et au moyenvâge; histoire, usages et symbolisme, Genève, Slatkine Reprints. Kader A A, Heintz C M, Labavitch J M and Rae H L (1982), ‘Studies related to the description and evaluation of pistachio nut quality’, J Amer Soc Hort Sci, 107, 812–816. Kader A A, Labivitch J M, Mitchell F G and Sommer N F (1978), Quality and safety of pistachio nuts as influenced by postharvest handling procedures, The Pistachio Association Annual Report, CA, pp. 45–51. Kader A A, Labivitch J M, Mitchell F G and Sommer N F (1979), Quality and safety of pistachio nuts as influenced by postharvest handling procedure, The Pistachio Association Annual Report, CA, pp. 45–56. Kashani G G and Valadon L R G (1983), ‘Effect of salting and roasting on the lipids of Iranian pistachio kernels’, J Food Technol, 18, 461–467. Kashani G G and Valadon L R G (1984), ‘Effect of salting and roasting on the carbohydrates and proteins of Iranian pistachio kernels’, J Food Technol 19, 247–253. Kashaninejad M and Tabil L G (2009), ‘Resistance of bulk pistachio nuts (Ohadi variety) to airflow’, J Food Eng, 90, 104–109. Kashaninejad M, Maghsoudlou M, Khomeini M and Tabil L G (2010), ‘Resistance to airflow through bulk pistachio nuts (Kalleghochi variety) as affected by the moisture content, airflow rate, bed depth and fill method’, Powder Technol., 203, 359–369. Kashaninejad M, Mortazavi A, Safekordi A and Tabil L G (2006), ‘Some physical properties of Pistachio (Pistachia vera L.) nuts and its kernel’, J Food Eng, 72, 30–38. Kashaninejad M, Mortazavi A, Safekordi A and Tabil L G (2007), ‘Thin layer drying characteristics and modeling of Pistachio nuts’, J Food Eng, 78, 98–108. Kashaninejad M, Tabil L G, Mortazavi A and Safekordi A (2003), ‘Effect of drying methods on quality of pistachio nuts’, Dry Technol, 21(5), 821–838. Kaska N (2002), ‘Pistashio nut growing in the mediterranean basin’, Acta Hort, 591, 443–451. Kirkbride D (1966), ‘Beidha: an early neolithic village in Jordan’, Archaeol, 19, 199–207. Kramer C (1982), Village Ethnoarchaelogy: Rural Iran in Archaeological Perspective, New York, Academic Press. Labavitch J M, Heintz C M, Rae H L and Kader A A (1982), ‘Physiological and compositional changes associated with maturation of “Kerman” pistachio nuts’, J Amer Soc Hort Sci, 107, 688–692. Lemaistre J (1959), ‘Le pistachier (étude bibliographique)’, Fruits 14, 57–77. Leufven A, Sedaghat N and Habibi M B (2007), ‘Influence of different packaging systems on stability of raw dried pistachio nuts at various conditions’, Iranian Food Sci Technol Res J, 3 (2), 27–36. Maggs D H (1973), ‘Genetic resources in pistachio’, FAO Plt Genet Resources Newsletter 29, 7–15. Maskan M and Karatas S (1998), ‘Fatty acid oxidation of pistachio nuts stored under various atmospheric conditions and different temperatures’, J Sci Food Agric, 77, 334–340. Michailides T, Morgan D P and Doster M A (1995), ‘Foliar and fruit fungal diseases’, in Ferguson L, Pistachio Production, Center for Fruit and Nut Crop Research and Information, Pomology Dept., Univ. Calif., Davis, CA, pp. 148–159. Mohammadi Moghaddam T, Razavi M A, Malekzadegan F and Shaker Ardekani A (2009), ‘Chemical composition and rheological characterization of pistachio green hull’s marmalade’, J Texture Studies, 40, 390–405. Moldenke H N and Alma L (1952), Plants of the Bible, Waltham, Chronica Botanica. Nakhaeinejad M (1998), Pistachio Hulling and Processing in Iran, Kerman, Momtazan Industrial Co. Nazari Galedar M, Mohtasebi S S, Tabatabaeefar A, Jafari A and Fadaei H (2009), ‘Mechanical behavior of pistachio nut and its kernel under compression loading’, J Food Eng, 95, 499–504.

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Razavi M A and Taghizadeh M (2007), ‘The specific heat of pistachio nuts as affected by moisture content, temperature and variety’, J Food Eng, 79, 158–167. Razavi M A, Emadzadeh B, Rafe A and Mohammad Amini A (2007a), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part I. Geometrical properties’, J Food Eng, 81, 209–217. Razavi M A, Emadzadeh B, Rafe A and Mohammad Amini A (2007b), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part II. Gravimetrical properties’, J Food Eng, 81, 218–225. Razavi M A, Mohammad Amini A, Rafe A and Emadzadeh B (2007c), ‘The physical properties of pistachio nut and its kernel as a function of moisture content and variety: Part III. Frictional properties’, J Food Eng, 81, 226–235. Razavi M A, Rafe A and Akbari R (2007d), ‘Terminal velocity of pistachio nut and its kernel as affected by moisture content and variety’, African J Agric Res, 2 (12), 663–666. Rieger M (2006), Introduction to Fruit Crops, New York, Food Product Press. Seeram N P, Zhang Y, Henning S M, Lee R, Niu Y, et al. (2006), ‘Pistachio skin phenolics are destroyed by bleaching resulting in reduced antioxidative capacities’, J Agric Food Chem, 54, 7036–7040. Seyhan F G (2003), ‘Effect of soaking on salting and moisture uptake of pistachio nuts (Pistachia vera L.) from Turkiye’, GIDA, 28 (4), 395–400. Sheridan M J, Cooper J N, Erario M and Cheifetz C E (2007), ‘Pistachio nut consumption and serum lipid levels’, J Am Coll Nutr, 26, 141–148. Shokraii E H (1977), ‘Chemical composition of the pistachio nuts of Kerman, Iran’, J Food Sci, 42, 244–245. Shokraii E H and Esen A (1988), ‘Composition, solubility, and electrophoretic patterns of proteins isolated from Kerman pistachio nuts (Pistacia vera L.)’, J Agric Food Chem, 36 (3), 425–429. Taghizadeh M and Razavi M A (2009), ‘Modeling time-independent rheological behavior of pistachio butter’, Int J Food Properties, 12, 331–340. Thompson J F, Rumsey T R and Spinoglio M (1997), ‘Maintaining quality of bulk-handled, unhulled pistachio nuts’, App Eng Agric, 13, 65–70. USDA (2006), ‘National Nutrient Database for Standard Reference’, Release 19, National Technical Information Service, USDA, Springfield, VA. Whitehouse W E (1957), ‘The pistachio nut – a new crop for the western United States’, Economic Botany 11, 281–321. Woodroof J G (1979), Tree Nuts: Production Processing Products, Westport, Conn., AVI. Zohary M (1952), ‘Amonographical study of the genus Pistacia’, Palest J Bot, 5, 187–228.

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Plate XX

Plate XXI

(Chapter 11) Grape-like clusters of pistachio fruits on a tree.

(Chapter 11) Kernel, skin, shell and hull of pistachio nut.

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12 Pitahaya (pitaya) (Hylocereus spp.) F. Le Bellec and F. Vaillant, Centre for Agricultural Research and Development (CIRAD), France

Abstract: While pitahaya (Hylocereus spp.) was originally domesticated by preColumbian Americans, it was still practically unknown until the mid-1990s in most parts of the world. Pitahaya is now a member of the ‘small exotic fruits’ category in many shops, though it remains a minor player. This chapter gives an initial evaluation of the advantages and disadvantages of this new fruit. Commercially, pitahaya appear to have numerous selling points; pitahaya’s fruit is attractive in shape and color, and it has very good internal properties of high interest for the food industry. Key words: Hylocereus, pitahaya, botany, agronomy, chemical composition, storage, postharvest technology, uses, markets.

12.1

Introduction

Practically unknown fifteen years ago, pitahaya1 today occupies a growing niche in the exotic fruit market as well as in the domestic markets of producer countries, such as Vietnam, Malaysia, Colombia, Mexico, Costa Rica and Nicaragua. Elsewhere, pitahaya is considered to be a new, promising fruit species; it is cultivated on different scales in Australia, Israel, and Reunion Island (Le Bellec et al., 2006). This success can be explained in part by the fruit’s appealing qualities and characteristics (attractive color and shape) and by the commercial policies of some producing and exporting countries (e.g., Vietnam, Colombia and Israel). The generic term ‘pitahaya’ includes several different species, which can often be a source of confusion. Currently, only a few species of pitahaya are commonly found on the market: yellow pitahaya (Hylocereus megalanthus Bauer), a fruit with yellow skin and white pulp, and red pitahaya (Hylocereus spp. Britt & Rose), a fruit with a red skin and either white or red pulp. These species are native to tropical 1

Different spellings are used : pitaya, pitahaya, pitajaya, pitajuia, pitalla or pithaya

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and sub-tropical America. Up to now, available publications have dealt with very specific topics on the difficulties of introducing pitahaya as a commercial fruit, the principal research topics being genetics, floral biology, ecophysiology and fruit characterization (physico-chemical composition). The aim of our work was to draw up an exhaustive list of literature currently available on Hylocereus and to group the references by discipline (uses and marketing, botany, biogeography, floral biology, agronomy, postharvesting and composition).

12.2

Uses and market

The pulp of the fruit is refreshing and possesses a texture close to that of kiwi fruit. It is much appreciated, especially if chilled and cut in halves so that the flesh can be eaten with a spoon. The juice is enjoyed as a cool drink, while syrup made of the whole fruit is used to color candy and the pulp is also used in sorbet and fruit salads. Flowers can be cooked and eaten as a vegetable. Hylocereus spp. are also used for medicinal purposes and their leaves and flowers have traditionally been used by the Mayas in Latin America as a hypoglycemic, diuretic, and cicatrizant agent (Pérez et al., 2007). The medicinal uses are increasingly sought as reported in recent studies. An aqueous extract of Hylocereus exhibited positive protective microvascular activity and wound-healing properties in diabetic rats (Pérez et al., 2005), while Pérez et al. (2007) isolated and showed properties of two triterpenes from H. undatus in the protection against increased skin vascular permeability in rabbits. Khalili et al. (2009) suggested that the consumption of red pitahaya play a role in the prevention of cardiovascular disease. Pitahaya is widely consumed in South America and Asia, but it was unknown in the European Union and North America until the mid-1990s. The fruit is still a niche product, but imports have increased considerably in the last two years and pitahaya now has its place in the displays of retailers devoted to rare exotic fruits (Le Bellec et al., 2006) and the range of supplier countries is growing rapidly. Israel, with a major cost price advantage thanks to sea transport, competes with Asian suppliers during the second half of the year. The fruit attracts two different market segments. Asian customers purchase it quite regularly, with a peak at the Chinese New Year. On this occasion, it is not usually bought for its taste, but for its fine appearance because it is displayed as an offering to ancestors. The greatest demand is for large fruits. This success can be explained in part by the fruit qualities and characteristics and also by the commercial policies of some producing and exporting countries.

12.3

Botany, origin and morphology

12.3.1 Botany and genetic Pitahaya belongs to the vine cacti of the genera Hylocereus (Berger) Britt and Rose of the botanical family Cactaceae. Hylocereus is characterized as a climbing plant

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with aerial roots that bears a large, scaly, glabrous berry (Britton and Rose, 1963). Hylocereus spp. are diploid (2n = 22) except H. megalanthus (allotetraploid, 2n = 4x = 44) (Lichtenzveig et al., 2000; Tel-Zur et al., 2004b). In Latin America, many different cultivated species and fruits are referred to as ‘pitahaya’, a generic and vernacular name that renders their botanical classification difficult. However, all pitahaya are grouped into four main genera: Stenocereus Britton & Rose, Cereus Mill., Selenicereus (A. Berger) Riccob and Hylocereus Britton & Rose (Mizrahi et al., 1997). We focused particularly on the Hylocereus species (see Plate XXII in the colour section between pages 238 and 239). There are many contradictions concerning the botanical classification of Hylocereus that are reflected in the difficulty of characterization. This is due to similar morphological characteristics and/or environmental conditions between species. For example, Britton and Rose (1963) have created a genus (Mediocactus) to classify the yellow pitahaya (actually H. megalanthus) due to a description of the morphology of a species which has a triangular stem like that of Hylocereus, and spiny fruits like those of Selenicereus. Accordingly, they classified it into a separate genus named Mediocactus, thereby implying both an intermediate morphology and an intermediate taxonomic status. Recent studies help to clarify this botanical classification (Bauer, 2003; Tel-Zur et al., 2004b). In our paper, we use Bauer’s nomenclature. Thus, there are 15 species of Hylocereus, whose ornamental value is due to the beauty of their large flowers (15–25 cm) that bloom at night (see Plate XXII in the colour section). Even if all these species can potentially produce fruits, only five are cultivated for this purpose and our study was limited to those. The characteristics of these species are presented below and summarized in Table 12.1:

•

•

H. costaricensis (Web.) Britton & Rose is characterized by vigorous vines, perhaps the most robust of this genus. Stems are waxy white and flowers are margined; the outer perianth sediments are reddish, especially at the tips; and stigma lobes are rather short and yellowish. Its scarlet fruit (diameter: 10–15 cm; weight: 250–600 g) is ovoid and covered with scales that vary in size; it has a red purple flesh with many small black seeds, pleasant texture and good taste. H. megalanthus Bauer (syn. Selenicereus megalanthus) has long, slender and green stems; not horned. The areoles are white. Its yellow fruit (diameter: 7–9 cm; weight: 120–250 g) is oblong, covered with clusters of deciduous spines, black seeds; its edible flesh has a pleasant, sweet flavor.

Table 12.1

Peel and flesh colors of Hylocereus spp.

Species

Weight

Peel color

Flesh color

Common name

H. costaricensis H. megalanthus H. purpusii H. monocanthus H. undatus H. undatus subsp. luteocarpa

250–600 g 120–250 g 150–400 g 200–400 g 300–800 g 100–480 g

Red Yellow Red Purple Rosy-red Clear yellow

Red purple White Red Red purple White White

Red pitaya Yellow pitaya Red pitaya Red pitaya Dragon fruit –

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•

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H. ocamponis (Weing.) Britton & Rose (syn. H. purpusii) has very large (25 cm) flowers with margins; outer perianth segments are more or less reddish; middle perianth segments golden, and inner perianth segments white. It produces scarlet, oblong fruit covered with large scales (length: 10–15 cm; weight: 150–400 g); red flesh with many small black seeds; and has pleasant flesh texture though not very pronounced. H. monocanthus Bauer (including H. polyrhizus) has very long (25–30 cm) flowers with margins; outer reddish perianth segments, especially at the tips; and rather short and yellowish stigma lobes. Its scarlet fruit (length: 10–15 cm; weight: 200–400 g) is oblong and covered with scales that vary in size; it has a red flesh with many small black seeds, pleasant flesh texture and good taste. H. undatus (Haw.) Britton & Rose (see Fig. 12.1) has long and green stems, more or less horned in the age margins. Flowers are very long (up to 29 cm), outer perianth segments are green (or yellow-green) and inner perianth segments

Fig. 12.1

Fruit of Hylocereus undatus (© F. Le Bellec).

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pure white. Its rosy-red fruit (length: 15–22 cm; weight: 300–800 g) is oblong and covered with large and long scales, red and green at the tips; it has a white flesh with many small black seeds, pleasant flesh texture and a good taste. A new subspecies of H. undatus subsp. luteocarpa from Mexico has been recently described, having yellow fruit with large foliaceous scales (De Dios, 2005). Many varieties of Hylocereus exist throughout the world, selected or not by humans. The custom of regarding fruit morphology and color is often the sole criterion for defining species. For example, a few varieties of H. costaricensis are known in Costa Rica as: ‘Lisa’, ‘Cebra’ and ‘Rosa’ (Vaillant et al., 2005). Recently, morphological variation was studied in 21 pitahaya genotypes in Mexico which allowed discriminating, by vegetative criteria, four groups within the species H. undatus (Grimaldo-Juárez et al., 2007). These authors conclude: ‘The variability of this group represents greater capacity to change in response to its environment, demonstrating different phenotypes, which are selected by man as suggested for yellow, red and magenta pitahaya’. This study has not been complemented by genetic analyses; perhaps they would have discovered subspecies as described by De Dios (2005) or hybrids. Indeed, reciprocal crosses among diploid Hylocereus species and the ease of obtaining partially fertile hybrids facilitates the creation of new variety (for natural or voluntary hybridization). For examples, Tel-Zur et al. (2004b) have created many hybrids for their experiment; to overcome the problems associated with self-incompatible varieties that are grown on Reunion Island, we have easily created a hybrid H. undatus × H. costaricensis, see Fig. 12.2 that allows the pollination of these two parents (Le Bellec et al., 2004). In conclusion, few studies seek to describe and characterize pitahaya varieties. The market reduces this apparent diversity to two colors of fruits: yellow and red!

Fig. 12.2

Hybrid of H. undatus (right) × H. costaricensis (left) (© F. Le Bellec).

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12.3.2 Origin, distribution and ecology of Hylocereus Most Hylocereus species originate principally from Latin America (probably from Mexico and Colombia), with others possibly from the West Indies (Britton and Rose, 1963). In these regions, pitahaya has been cultivated for many years. Ethnobotanical studies (Mesoamerican region) indicate Hylocereus species were domesticated by pre-Columbian cultures (Casas and Barbera, 2002) and have been a food source for inhabitants. Today they are distributed all over the world (in tropical and subtropical regions), but H. undatus is the most cosmopolitan species. In their region of origin, the fruits of Hylocereus sp. are the main traditional fruit and the most widely consumed local fruit (Mizrahi et al., 1997). The Hylocereus species is at present cultivated for fruit production in Cambodia, Colombia, Costa Rica, Ecuador, Guatemala, Indonesia, Malaysia, Mexico, Nicaragua, Peru, Taiwan and Vietnam, with more recent cultivation in Australia, Israel, Japan, New Zealand, Philippines, Spain, Reunion Island and the southwestern United States (Valiente-Banuet et al., 2007, Le Bellec et al., 2006). The robustness of Hylocereus species enables them to prosper under different ecological conditions. For example, in Mexico, they are found in very rainy regions (340 to 3500 mm year) and at altitudes of up to 2750 m above sea level (Mizarhi et al., 1997). They can survive in very hot climates, with temperatures of up to 38–40 °C (Le Bellec et al., 2006); nevertheless, in some species, temperatures below 12 °C can cause necrosis of the stems (Bárcenas, 1994). Hylocereus species are semi-epiphytes and consequently usually prefer to grow in half-shaded conditions (conditions provided in nature by trees). Some species tolerate sites totally exposed to solar radiation (H. undatus, H. costaricensis and H. purpusii, for example), however, gas exchange and growth or flowering are often inhibited (Nerd et al., 2002; Andrade et al., 2006) and very hot sun and insufficient water may lead to burning of the stems. In the Neveg Desert in Israel, the most favorable conditions for growth and fruit production are found to be 30% shade for H. polyrhizus (Raveh et al., 1996), while in the French West Indies (Guadeloupe and Saint-Martin), cultivation of H. trigonus is only possible with about 50% shade (Le Bellec et al., 2006). H. undatus tolerates prolonged drought, up to six weeks, without any effect on growth (Nobel, 2006). In Mexico, the rainy season provides optimal conditions for photosynthesis in H. undatus, due to low air temperature and, small deficit of vapor pressure during the night (Andrade et al., 2006) but excess water systematically results in the abscission of flowers and young fruits (Le Bellec et al., 2006). Hylocereus species can adapt to different types of welldrained soil (Bárcenas, 1994). 12.3.3 Morphology and reproductive biology of Hylocereus Few studies have been published on the floral biology of H. undatus and H. costaricensis, the two most widely cultivated Hylocereus species in the world. Some researchers are interested in them, in some cases to study the cultivation potential of this new fruit (Weiss et al., 1994), and in other cases to study the floral biology of this species that is endemic to Costa Rica and Mexico (Castillo et al.,

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2003). The flowers of Hylocereus appear under the areoles; they are large (more or less 30 cm), in the shape of a funnel, and nocturnal. The ovary is located at the base of a long tube carrying the foliaceous scales to the exterior and there are numerous stamens on a slender anther stalk. The unusually large, tubular style is 20 cm in length and 0.5 cm in diameter; the stigmas have 24 slender lobes, and are creamy green in color. Floral growth does not depend on water availability, but on day length; in Vietnam, floral induction is often triggered using artificial light to increase day length. On Reunion Island, it has been demonstrated that the number of flowers obtained using artificial light at night is proportional to the distance between the receiving point and the light source. The floral buds can remain in the latent stage for many weeks (Le Bellec et al., 2006), and the beginning of flowering generally occurs after the rainy season (Le Bellec et al., 2006). In the southern hemisphere, H. undatus and H. costaricensis flower from November to April, and in the northern hemisphere from May to October (Weiss et al., 1994; Le Bellec, 2004). Flowering episodes are cyclic and spread out over the whole period and the number of flowering episodes or flushes depends on the species: for example, seven to eight for H. costaricensis and five to six for H. undatus. There is a period of three to four weeks between flowering flushes (Le Bellec, 2004), which makes it possible to see floral buds, flowers, young fruits and mature fruits on the same plant at the same time. The periods between the appearance of floral buds (lifting of the areole) and flowering (stage 1), and between flower anthesis and fruit harvest (stage 2) are very short: around 15 to 20 days for the first stage and 30 days for the second stage. In their native countries, pollination of flowers occurs during the night by nectar-feeding bats such as Leptonycteris curasoae and Choeronycteris mexicana (Herrera and Martinez Del Rio, 1998; Valiente-Banuet et al., 2007) or by a species of butterfly belonging to the Sphingideae family, of the genus Maduca. During the day bees (Apis melifera) pollinate flowers (Le Bellec, 2004; Valiente-Banuet et al., 2007). There seems to be no major problems connected with fruit yields in the main producing countries in Latin America and Asia (Valiente-Banuet et al., 2007). Dehiscence takes place a few hours before the complete opening of the flower. Pollen is very abundant, heavy and not powdery. Flowers open at between 20:00 and 20:30; the stigma dominates the stamens (the position of the stigma at this stage encourages allogamy). Flowers bloom only for a day and then close (whether fertilized or not) in the morning of the day after anthesis. The following day, petals become soft and then slowly dry. The lower part of a non-fertilized flower becomes yellowish and the whole flower falls off four to six days later, while the lower part of a fertilized flower remains greenish and increases enormously in volume, indicating that the fruit has set. In some countries (Israel, South Africa, Madagascar, Reunion Island and French West Indies), natural production of fruits from clones introduced from H. undatus and H. costaricensis is practically non-existent (Le Bellec et al., 2006). The autoincompatibility (Weiss et al., 1994) of the clones of these species and the absence of efficient pollinators – interspecific crossing is possible – appear to be responsible for this lack of productivity. Honeybees are very attracted to the pollen of these flowers and the repeated visits of these insects can contribute to pollination (Weiss

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et al., 1994). However, the quality of the fruits resulting from free pollination is generally lower than that of those obtained by manual cross-pollination (Le Bellec, 2004). The origin of the pollen can also influence the time lapse between pollination and harvest of the fruit (known as the phenomena of metaxenia, this was previously only observed on H. polyrhizus) (Mizrahi et al., 2004).

12.4

Cropping system

Pitahaya has only been cultivated for a short time and the first published references to serious cultivation practices date back only to around 15 years ago (Le Bellec et al., 2006). Little agronomic knowledge has been acquired from the traditional cultivation of these species in tropical America, or this knowledge has perhaps not been published. Traditional methods of cultivation have changed considerably in new production areas, as they have been adapted and improved to overcome the problems encountered there (Weiss et al., 1994). Two major pitahaya production systems are considered: the undergrowth cropping system with a well-established ecology (of the forest type, see Plate XXIII in the colour section), and the intensive system where optimum conditions for pitahaya production (shade, feeding, and irrigation) are created and managed. The undergrowth cropping system can only be effective in the natural ecological area of pitahaya. It is appropriate for plantation projects emphasizing natural production (biological production, low input, production with labels, etc.). The intensive system, on the other hand, makes it possible to enlarge the pitahaya production zone. It is particularly appropriate for projects where potential extension surfaces are limited and/or the high cost of the workforce is a limiting factor. Each system carries advantages and disadvantages. The farming of pitahaya under a natural vegetable cover that was not established for shading purposes for this same pitahaya is practiced in many areas of production (Rondón, 1998). It is probably the most used system since it is the cheapest one. This undergrowth pitahaya production method is referred to as the ‘traditional’ method, which generally provides conditions that are favorable to pitahaya production: shade, organic matter resulting from the decomposition of the leaves and branches of the vegetable cover, hygrometry, etc. However, these conditions can vary notably according to the season and undergrowth type (Andrade et al., 2006). For these reasons, regular upkeep is essential in these pitahaya plantations in order to maintain optimum growing conditions. To improve production with this method, it is possible to recreate this environment by planting tutors specifically for this culture (De Dios and Castillo Martinez, 2000). This production system allows a better control of the shade through the choice of an adapted tutor as the shade is not always adequate or at least not easily controlled. The need for water is also not always provided for. The intensive production system of the pitahaya – including artificial shade, dead tutors and an irrigation system – make it possible to meet the exact requirements of the pitahaya production. Cropping system intermediaries can also be designed. For example, pitahaya can be cultivated on dead tutors between hedges, with the trees providing

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the necessary shade. If these cropping systems are different, the specific techniques of production will not change. Only investment, labor mobilization and quantities of inputs will be different from one system to another.

12.5

Cultivation techniques

12.5.1 Multiplication and planting density Hylocereus can be multiplied naturally and very easily by cutting off the stem as soon as it touches the ground. Its sequential stem segments can develop adventitious roots, so each rooted stem segment can act as an individual unit for water uptake (Nobel, 2006). The sowing of seeds and the in vitro multiplication of young shoots of mature plants are also possible (Yassen, 2002). However, in agriculture, multiplication by cuttings is preferable, as it allows reliable reproduction of the variety. In addition, the fruiting stage is reached more rapidly with cuttings, less than one year after planting, as opposed to three years for plants grown from seed. Finally, the robustness of these species enables cuttings to be taken directly in the field; provided cuttings are at least 50 to 70 cm in length and are regularly watered in order to ensure satisfactory rooting. Given these conditions and the plant’s characteristics, around 90% of the cuttings will grow (Le Bellec et al., 2006). The distance between plants depends on the type of support used. With an artificial vertical support (see Fig. 12.3), a 2–3 m distance between planting lines is required (between 2000 and 3750 cuttings.ha−1), at a rate of three cuttings per support. With horizontal or inclined supports, the density can be

Fig. 12.3

Plant and flowers of Hylocereus costaricensis (© F. Le Bellec).

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much higher since the cuttings are planted every 50–75 cm around the production table (6500 cuttings.ha−1) or along the inclined support (6500 cuttings.ha−1) (Le Bellec et al., 2006). The height of these different types of support should be between 1.40 and 1.60 m for vertical supports and between 1 and 1.20 m for horizontal and inclined supports to facilitate management of the crop. 12.5.2 Cultivation practices Pitahaya are semi-epiphytic plants, which crawl, climb and attach naturally to any natural or artificial support they meet (trees, wood or cement posts, stone walls, etc.) thanks to their aerial roots. Growing them flat on the ground is not recommended, first because it makes cultivation more difficult (pollination, harvest, etc.), and secondly because contact with the ground causes damage to the vines. Pitahaya are thus best grown on living or dead supports (De Dios and Castillo Martinez, 2000). Many different types of support are used, but we focus on vertical supports made of wood (or cement and iron posts) and on horizontal and inclined supports (Le Bellec et al., 2006). Plant growth is rapid and continuous, though possibly with a vegetative rest period when the climatic conditions are unfavorable (such as drought and very low temperatures). When vertical and horizontal supports are used, pruning is important and the stems should be selected in such a way as to force the plant to climb over the entire support. All lateral growth and parts of the plant facing the ground should be removed, while the main stems and branch stems are kept, except those that touch the ground. Major pruning is carried out the first year after planting. Whatever the support used, the stem must be attached to it with a clip. The aim of maintenance pruning is to limit bunch growth and this should be carried out as early as the second year after planting. In practice, the extent of pruning depends on the type of support and its strength. For example, a three-year-old plant weighs around 70 kg (Le Bellec et al. 2006). Even if this weight is not in itself a problem for the different types of support, bunches may not be able to withstand violent winds. Pruning consists of removing all the damaged stems from the plant in addition to those that are entangled with one another. The postharvest pruning encourages the growth of new young shoots that will bear flowers the following year. 12.5.3 Nutrition and irrigation In natural conditions, the pitahaya feeds exclusively on the organic matter that is contained in the superficial layers of the soil. In order to create ideal conditions of production, it is important to complete this natural nutrition. Yields vary as a function of the nutritive elements supplied. The pitahaya’s root system is superficial and can rapidly assimilate even the smallest quantity of nutrients. Mineral and organic nutrition is particularly advantageous and, when combined, their effect is even more beneficial (López and Guido, 1998; Le Bellec et al., 2006). Even if pitahaya can survive with very low rainfall – many months of drought – when good quality fruits are required, a regular water supply is needed. Regular irrigation is

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important, because it enables the plant to build sufficient reserves not only to flower at the most favorable time, but also to ensure the development of the fruits. To ensure good fruit production, irrigation is often necessary, and local microirrigation is particularly recommended. In addition to the efficiency of the water supplied by this system, micro-irrigation avoids uneven and excess watering that can result in flowers and young fruits falling off the vines. 12.5.4 Weed management Weed management is an important point of the pitahaya production; the pitahaya’s root system is superficial and is particularly sensitive to competition for water. Orchards are traditionally planted on sloping grounds or in the forest; this prevents the development of weeds. Then, the use of herbicides regularly sprayed on the whole farm is a common practice. Consequently, such a practice involves some impact on the environment and the production profit (for herbicides and labor costs). Introduction of cover crops on these orchards may be an interesting alternative. A vegetative cover plant established on the inter-row can be very advantageous: it allows near total control of erosion in the event of strong rains, ensures water conservation, restores soil fertility thanks to its biological reactivation and makes it possible to limit, and even control, the proliferation of adventitious. This weed management can be supplemented by a mulching around pitahaya. 12.5.5 Pollination The lack of genetic diversity and/or the absence of pollinating agents in certain production areas means that manual cross-pollination is needed to ensure fruit setting and development (Weiss et al., 1994; Catillo et al., 2003). Manual pollination (see Fig. 12.4) is simple and this operation is facilitated by the floral characteristics of Hylocereus, as the different floral parts are very large. Finally, manual pollination may be carried out from before anthesis of the flower from 4:30 p.m. until 11:00 a.m. the next day. These manual pollinations are worth undertaking and the fruits obtained are of excellent quality (Le Bellec, 2004). Pollination is accomplished by opening the flower by pinching the bulging part. This reveals the stigmata, which are then covered with pollen with a brush. Alternatively, the anthers can be directly deposited (with minimal pressure) on the stigmata with the fingers. The pollen can be removed from a flower of a different clone (or from another species) and stored in a box until needed. The pollen removed from two flowers will be enough for around 100 pollinations with a brush. It can be stored for 3 to 9 months at −18 to −196 °C without risk of damage. Fruits obtained after pollination using pollen stored at 4 °C for 3 to 9 months are usually very small (Metz et al., 2000). The activity of bees (Apis mellifera) can make manual pollination difficult, but it must nevertheless be accomplished (Le Bellec, 2004). Bees can be extremely efficient and, after only a few hours of activity, they will have harvested all the pollen. The pollen must thus be collected before the bees arrive and manual pollination carried out the next morning as soon as the bees have left the plantation.

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Fig. 12.4

Manual pollination of Hylocereus spp. (© F. Le Bellec).

12.5.6 Harvesting Fruits from Hylocereus species are non-climacteric and have a low respiration rate when mature and after being picked (ranging between 50 and 120 mg CO2 kg−1. h−1) (Hoa et al., 2006; Nerd et al., 1999; To et al., 2002), therefore fruits should be harvested when they have attained full maturity and development is complete. Up to now the only practical harvest indexes have been the color of the epidermis and fruit firmness (To et al., 2002) which are usually assessed subjectively by fruitpickers. For both Hylocereus species (H. undatus and H. polyrhizus) it has been shown that when the color of the epidermis turns fully red, the size, fruit weight, pulp content, total soluble solids, pulp betacyanins and flavor rating reach maximum values while firmness, mucilage content, starch and total titrable acidity are at a minimum (Nerd et al., 1999). For example, in previous studies, firmness reduced rapidly from values of up to 12 kg.cm−2 at 16–20 days after anthesis to 1.2 ± 0.5 kg cm−2 at the stage when fruit epidermis is fully red (Nerd et al., 1999; To et al., 2002). This firmness value remains high and decreases only slightly during storage. Therefore, the practice of picking fruits earlier to let them better withstand transport is counterproductive as they will never develop full flavor or proper texture. In Vietnam and Mexico, this optimal maturity stage is reached within 28–31 days after anthesis for Hylocereus undatus (To et al., 2002; Yah et al., 2008), while in Israel, fruits from both Hylocereus undatus and polyrhizus grown under

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greenhouse conditions reached optimum maturity between 33–37 days after anthesis (Nerd et al., 1999). Yields vary between 5 and 30 t.ha−1, being closely related to the density of planting and practice, type of pollination, etc.

12.6

Pests and diseases

The development of the culture of pitahaya in recent years has been accompanied by the appearance of some diseases, such as anthracnose caused by Colletotrichum gloeosporioides (Palmateer et al., 2007), basal rot caused by Fusarium oxysporum (Wright et al., 2007), stems necrotic lesions caused by Curcularia lunata (Masratul Hawa et al., 2009), stem spots caused by Botryosphaeria dothidea (ValenciaBotin et al., 2003). Different viral (Cactus virus X) and bacterial (Xanthomonas sp. and Erwinia sp.) diseases are also reported in the literature and can have major consequences (Liou et al., 2004). Several factors influence the development of these diseases: rainfall, badly decomposed compost, too humid or too dry soil, successive periods of continuous rain and dryness involving asphyxiates and lack of water. On the other hand, the eradication of these diseases seems unlikely, only preventive and prophylactic measures seem suitable. The sanitary quality of plant material is dominant and determines the life of the plantation. Few pests have been recorded on Hylocereus. Ants belonging to the genera Atta and Solenopsis (Le Bellec et al., 2006) can cause major damage to the plants as well as to the flowers and fruits (see Fig. 12.5). Cotinus mutabilis perforates the stem and Leptoglossus zonatus sucks the sap, leaving stains and some deformation. Different species of aphids and scales have also been observed on fruits and flowers. Rats and

Fig. 12.5 Ant damage on fruit (© F. Le Bellec).

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birds can cause serious damage, mainly to flowers and fruits, but also to ripe fruits. The marketing of fruit may be affected by various diseases as fruit rot caused by Bipolaris cactivora (Taba et al., 2007). In some regions, pitahaya fruits are hosts of fruit fly species (Bactrocera spp.), and thus export to many markets require a disinfestation treatment (Hoa et al., 2006). Hot air treatments (46.5 °C for 20 min) (Hoa et al., 2006) and irradiation with X-rays can be successfully applied to ensure a stable visual and compositional quality during storage (Wall and Khan, 2008).

12.7

Quality components and indices

The edible part of pitahaya fruit corresponds to the mesocarp which yields a viscous juice containing many small seeds. The main physico-chemical properties of pitahaya juice (without seeds) are reported in Table 12.2. Juice contains approximately 12 ± 2% dry matter, mainly composed of reducing sugars, glucose and fructose (sucrose was only detected in traces). The amount of reducing sugars ranges from 50 to 130 g l−1 depending on varieties and cultivars (see Table 12.2). In mature fruit, a gradual increase of total soluble solids (TSS) concentration is Table 12.2

Main physico-chemical composition of Hylocereus fruit pulp

Characteristics pH-valuea Dry matter Density (20 °C) Total titratable acidsa,b Malic acid Citric acid Total soluble solidsa Protein content Lipid Glucose

Unit % g.cm−3 g.l−1 g.l−1 g.l−1 °Brix g.l−1 g.l−1

Fructose Minerals Pectin L-Ascorbic acid Dehydroascorbic acid Total vitamin C Betacyanin

g.l−1 g.l−1 mg.100 g−1 g.100 ml−1 g.100 ml−1 g.100 ml−1 mg.l−1

Total dietary fiber Total phenolics

g.100 gl−1 μM GACb equ.g−1

Hylocereus spp. 4.3–4.7 (Stintzing et al., 2003) 12 ± 1 1.04 ± 0.01 2.4 (Vaillant et al., 2005) to 3.4 (Stintzing et al., 2003) 6.2–8.2 (Esquivel et al., 2007a) 0.95–1.2 (Esquivel et al., 2007a) 7.1–10.7 1.2–1.25 1.17–1.43 30–103 (Esquivel et al., 2007a; Stintzing et al., 2003) 19–29 (Esquivel et al., 2007a) 65–136 (Esquivel et al., 2007a) 1.6–3.5 (Esquivel et al., 2007a) 1.1–3.6 (Esquivel et al., 2007a) 3.2–5.8 (Esquivel et al., 2007a) 530–717a (Esquivel et al., 2007c; Stintzing et al., 2003; Vaillant et al., 2005) 3.2 ± 0.1 (Mahattanatawee et al., 2006) 5.6–7.4 (Vaillant et al., 2005)

Notes: a Hylocereus polyrhizus. b Gallic acid equivalent.

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observed from the external section of mesocarp to the center of the fruit (Nomura et al., 2005) though TSS concentration rarely reaches more than 140 g.100 g−1 in Hylocereus species, with common values ranging generally between 8 and 13 g TSS.100 g−1 (Esquivel et al., 2007a; Vaillant et al., 2005; Yah et al., 2008). In the white flesh fruits (H. undatus), TSS content in mature fruit is slightly higher (up to 190 g TSS.100 g−1) as reported for fruits grown in temperate climate (Ming Chang and Chin Shu, 1997). Total titratable acidity is also always relatively low in pitahaya species, ranging between 2.4 and 3.4 g.L−1 according to genotype (Le Bellec et al., 2006), with malic acid as the predominant acid present in the pulp (Esquivel et al., 2007a; Nomura et al., 2005; Yah et al., 2008). Protein content varies considerably depending on methods used (from 0.3% to 1.5%) because betalain, the nitrogen-containing pigment responsible for the red color, may interfere with results. The main amino acid present in pitahaya juice appears to be proline with a remarkably high content of 1.1 to 1.6 g.L−1 in juice (Stintzing et al., 1999). Mineral content is relatively high, with potassium the most prevalent mineral in juice, and followed by sodium and magnesium (Stintzing et al., 2003). Total dietary fiber content of pitahaya fruits is reported to be 3.2 ± 0.1 g.100 g−1 (FW) (Mahattanatawee et al., 2006), a relatively high value which is probably due to mucilage, a complex polymeric substance of carbohydrate nature with a highly branched structure. Nonetheless, mucilage has been reported to be only around 0.5% of fresh pulp for mature fruit from both Hylocereus undatus and polyrhizus (Nerd et al., 1999). Pectin was reported to be only 0.27% of fresh pitahaya pulp (Mahattanatawee et al., 2006). To our knowledge, no characterization of the mucilage of Hylocereus species has been reported so far, but it can be assumed that it displays similar characteristics of other cactus species, as recently reviewed for Opuntia sp. In this case, mucilage has been characterized as a complex mixture of at least five types of polysaccharides, less than 50% of which corresponds to a pectin-like polymer. The arabinogalactan backbone is apparently predominant but other branched polysaccharides are also associated (Matsuhiro et al., 2006). Residual starch is reported even in mature fruits but concentration is below 0.5% for both H. undatus and H. polyrhizus species (Nerd et al., 1999). Hylocereus species, both white and red flesh, appear to be surprisingly poor in total ascorbic acid, ranging between 12–17 mg.100 g−1 (FW) (Nerd et al., 1999; To et al., 2002) while other cactus species, for example prickly pear, have a much higher vitamin C content which is comparable to that of citrus. Other vitamins may be present but have not been reported. Betalains is predominant in the red flesh from Hylocereus species while non-colored phenolic compounds are predominant in the white flesh of H. undatus. The red color of flesh in Hylocereus species is due to the presence of betalains, a pigment that replaces anthocyanins in fruit-bearing plants belonging to most families of caryophyllales (Stintzing et al., 2003; Strack et al., 2003). Betalains are watersoluble pigments that comprise red-purple betacyanin and yellow betaxanthins, and are an immonium conjugate of betalamic acid with cyclo-dopa and amino acids or amines, respectively. In contrast to red beet and other cactus fruits, red-purple pitahaya (H. polyrhizus) is a pure source of betacyanin as betaxanthins have not been

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detected (Strack et al., 2003), which explains the deep glowing red-purple color of the flesh. In red flesh pitahaya, the average content of total betalain ranges from 40–70 mg.100 ml−1. Structural studies on H. polyrhizus pigments reveal the presence of many betalains, but the three main betacyanins identified are betanin, phyllocactin and hylocerenin (Stintzing et al., 2006; Wybraniec et al., 2009). Betalain pigments present in red-flesh pitahaya display a red color with an absorbance peak around 536 nm (Stintzing et al., 2002). Betalains are of high commercial interest for food coloring but also for their functional properties as they present high antioxidant (Vaillant et al., 2005; Wu et al., 2006; Tesoriere et al., 2009;), anti-inflammatory (Allegra et al., 2005; Gentile et al., 2004), anti-cancer (Asmah et al., 2008), and anti-hypercholesterolemia properties (Khalili et al., 2009), reported in both chemical and cellular-based tests. Nonetheless, little is known on the real bioavailability of betacyanin (Tesoriere et al., 2004a). Betacyanins are absorbed from the digestive tract into the systemic circulation in their intact forms, yet the extent of in vivo absorption remains unknown (Frank et al., 2005) although average absorption of betalains simulated during in vitro gastro-intestinal digestion depends on the individual betalain compounds. For example, the bio-accessible fraction of betanin is only 40% in cactus fruits (O. ficus indica L. Mill.), slightly lower than for betanin from red-beet (Tesoriere et al., 2008). Pitahaya juice displays high antiradical activity; around 8–12 μmole of Trolox equivalent assessed by the ORAC method for the red flesh Hylocereus, a value very similar to beetroot (Ou et al., 2002). The white flesh Hylocereus species has a much lower ORAC value (around 3.0 ± 0.2) (Mahattanatawee et al., 2006), indicating a high participation of betacyanin compounds in the total antioxidant capacity. In most studies, a positive correlation between antioxidant capacity to total betalain content is generally observed (Esquivel et al., 2007b). Total phenolic compounds in white flesh (52.3 ± 33.6 mg GAE.100 g−1 puree) (Mahattanatawee et al., 2006). The main phenolic identified is gallic acid which is detected in various Hylocereus genotypes and tyrosine, a precursor in betalain biosynthesis (Esquivel et al., 2007b). The small granny seeds that account for about 1.3–1.5% of fruit yield 32–39% oil. The main fatty acids of pitahaya seed oil are palmitic acid (18%), oleic acid (22%), and linoleic acid (50%). The content of unsaturated fatty acids is high, around 75%, with polyunsaturated fatty acid around 50% which make the pitahaya oil comparable to flaxseed or grape seeds (Ariffin et al., 2009).

12.8

Postharvest handling factors affecting quality

As a non-climacteric crop, the quality of pitahaya fruits picked at optimum maturity tends to decrease during storage. Several factors affect fruit quality, unfortunately this knowledge is not published. Here is a review to date. 12.8.1 Temperature management Pitahaya fruits harvested close to full color stage can undergo low storage temperature up to 6 °C. However, chilling injury can occur after long period storage at 6 °C, and

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fruits present wilting and darkening of the scales and browning of the outer layer of the pulp. Fruits from Israel keep their visual acceptance and marketing quality for at least three weeks at 6 °C, two weeks at 14 °C or one week at 20 °C (Nerd et al., 1999). Throughout storage at all these temperatures, the concentration of soluble solids remained fairly constant. Fruits stored at 6 °C maintain their eating quality (flavor) for at least three weeks but deteriorated rapidly when transferred to room temperature (Nerd et al., 1999). Both varieties Hylocereus undatus and H. polyrhizus respond to storage in a similar manner (Nerd et al., 1999). During storage at 20 °C respiration rate decreases, remaining relatively low, ranging between 0.52 to 0.78 ml.CO2.kg−1.h−1, with the production rate of ethylene ranging from 0.025 to 0.091 ml.kg−1.h−1 (Nerd et al., 1999). 12.8.2 Water loss Due to scales, important thickness of peel and high mucilage content in flesh, fruit preserve high water content during storage even though water loss increases at higher storage temperature. After one week of storage at 20 °C, water loss reach only 4.2% and 3 weeks of storage at 6 °C water loss is generally reported below 6% (Nerd et al., 1999). Both species H. undatus and H. polyrhizus respond in a similar manner. 12.8.3 Atmosphere Only modified atmosphere packaging (MAP) was assessed to extend shelf life of pitahaya fruits. The shelf life of pitahaya has been extended in this case up to 35 days when stored at 10 °C, using polyethylene bags with average oxygen transmission rates of 4 l.m2.h−1 (To et al., 2002).

12.9

Processing

Pitahaya fruits can be marketed as ready-to-eat (fresh-cut) products after being peeled and/or sliced and packed in microperforated polyethylene bags. At these conditions, quality is maintained for about two weeks at either 4 or 8 °C, though an additional treatment should be implemented to prevent slices from sticking together (Goldman et al., 2005). Pure pitahaya juice is marketed in some countries and even exported. Fruits are washed, halved, and manually pulped, generally using a spoon. In Nicaragua, the pitahaya pulp obtained (with seeds) is then frozen at −20 °C, stored and directly exported to ethnic markets in the United States (Vaillant et al., 2005). Pulp can be also sieved on appropriate screens (0.5 to 1.0 mm) using a pulper with soft paddle or brushes to separate the juice from particulate matter, including seeds. However, the highly gelatinous mucilage which envelops every seed is difficult to remove by simple sieving without significantly decreasing juice yield (Esquivel et al., 2007a; Schweiggert et al., 2009). The same occurs when complete separation of mesocarp fibbers and seeds is implemented through centrifugation (Mosshammer et al., 2005). Thus, the

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compromise between juice yield and quality dictates the juicing and subsequent steps. An enzyme-assisted process for the liquefaction of pitahaya pulp can be added to degrade mucilage and make easier separation of seeds. Partial degradation of mucilage can be achieved with pulp maceration at 40 °C for two hours with very high concentration of previously selected enzymes (2000 ppm) (Herbach et al., 2007) or at 8 °C for three days with 1% ascorbic acid and 1000 ppm enzyme preparation (Schweiggert et al., 2009). The last process allows for the decrease of juice viscosity by 50%, enabling overall juice yields of 48–60% and 80% betalain recovery (Schweiggert et al., 2009), compared to 25–39% overall juice yields when no enzyme treatment is implemented. However, when compared to other fruit, the concentration of enzyme needed is extremely high, and even though the cost of enzyme can be offset by an increase of juice yields, additional research efforts are needed to develop cheaper alternatives. Traditionally, reduction of viscosity is achieved by adding ½ to ¼ (v/v) of water, sieving the slurry on cotton or synthetic cloth for the removal of seeds, and adding sugar and citric acid (TSS = 15 g.100ml−1 and pH = 3.5). The beverage is then pasteurized in glass bottles (Campos-Hugueny et al., 1986). To increase yield substantially, crushing of the whole fruit (with peel) has been also tested, not for Hylocereus species but for cactus fruits possessing similar characteristics. Cactus peel can be palatable and the mash obtained pressed using a cone screw expresser or paddle pulper fitted with appropriate screens (Mosshammer et al., 2006). An enzymatic maceration step can be implemented prior to pressing in order to increase yields, then, vacuum concentration, freezedrying or spray drying can be implemented to yield fruit juice extracts with good overall pigment retention (71–83%). Additionally, microfiltration, a membrane process, was also tested to stabilize at ambient temperature the juice but flux density was very low (<23 l.h−1.m−2) even if ½ (v/v) water is added, possibly precluding industrial feasibility. Actually, the use of innovative athermal alternatives should be more convenient for processing pitahaya juice as betalains are highly thermosensitive (Vaillant et al., 2005) compounds, although their instability depends on the specific betacyanin compounds involved and food matrix. It has been shown that betacyanins from Hylocereus polyrhizus exhibit higher stability toward heat treatment than betacyanins from red beet (Herbach et al., 2004). Nonetheless, during classical pasteurization treatment, losses of betanin and phyllocatin can reach 30–40% and 50–70% respectively, depending on time of exposure to high temperature (80–90 °C) (Herbach et al., 2007). The stability of betacyanin in red pitahaya juice can be significantly improved by adding ascorbic acid at 1% (w/w) before thermal treatment (Herbach et al., 2006). Pitahaya slices can be also dried conventionally by hot air, though the long time required significantly affects quality, so an alternative method using microwave has been proposed (Mad Nordin et al., 2008). Fresh fruit, peeled and cut into 15 mm thickness and 35 mm diameter slices are dried for 20–30 minutes according to microwave power input. However, color browning is significant and slices shrank by more than 70%.

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The main interest of red-flesh pitahaya is its color. Therefore, the fruit is a valuable source of water-soluble and natural pigment with large commercial interest. The coloring of food with natural fruit extracts is an increasing demand of health-conscious consumers. Betacyanin presents the advantage of maintaining its color over a wide pH range from 3 to 7, which is not the case of anthocyanins, another coloring pigment much more widespread in plants (Esquivel et al., 2007c). This property makes betalains ideal for coloring low-acid foods such as dairy products (Stintzing and Carle, 2004). The most important source of betalain is red beet, and extracts containing mainly betanin and its C15-isomer isobetanin are already commercialized worldwide. Nonetheless, the earth-like flavor of redbeet extracts due to specific compounds such as geosmin and pyrazine derivatives, as well as high nitrate concentrations associated with the formation of carcinogenic nitrosamines, makes other sources, like the Hylocereus species, even more promising for the extraction of betalains (Stintzing and Carle, 2004). Hylocereus species exhibit an exceptional red-purple hue since betaxanthin, a yellow betacyanin present in red-beet and totally absent in pitahaya juice, tends to degrade more easily and results in a brownish color (Stintzing et al., 2002). Additionally, pitahaya juice features significantly higher betalain contents than other edible sources (Stintzing et al., 2003). Coloring pigment can be extracted by water, ethanol, or a mixture of both and extraction with high ethanol concentrations presents the advantage of additionally separating mucilage and pectin-like material. By mixing 66% (v/v) of ethanol pitahaya juice, the mucilage and pectinlike material precipitate within 15 minutes (Mosshammer et al., 2005). Other authors have stirred the homogenized fruits with 20% (w/v) of water:ethanol (60:40 v/v) for 20 minutes and applied high speed centrifugation at 15 000 g at 10 °C for 10 minutes to remove partially mucilage (Castellar et al., 2006). In both cases, resulting supernatant containing betacyanin pigment is then concentrated under vaccum to yield a raw betacyanin extract that presents good coloring characteristics (Mosshammer et al., 2005). Further purification steps can be implemented to remove sugars using ion exchange resins (XAD7) (Mosshammer et al., 2005) or by repeating extraction with more polar solvents, though this can be costly at industrial scales and probably unnecessary. The use of natural juice is recommended for the natural coloring of foods, and because pitahaya juice has a very neutral flavor, it can be used in a large variety of products. Another cheaper alternative to a solvent extraction of betacyanin is the fermentation of whole juice by microorganisms. For instance, Saccharomyces cerevisiae has been used with prickly pears of Opuntia sp to yield a fermented product which, after concentration under vacuum, produces an alcohol-free concentrated colorant with high color strength, high betacyanins concentration, and low viscosity and sugar content (Obon et al., 2007). Once betacyanin has been extracted, different natural colorants can be obtained. By blending the betaxanthin from Opuntia and betacyanin from Hylocereus, tailor-made hues covering the entire spectrum from bright yellow (hue value (h) = 84) to purplish-blue (h = 333) were successfully produced. Since mixtures from purified betalains do not provide color shades different from those obtained with raw cactus fruit juices, the use of the latter

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should be preferred because of consumer-friendly labeling and improved pigment stability (Mosshammer et al., 2005). Within an industry producing pitahaya juice, disposal of wastes can be a major problem. Nonetheless, the pitahaya peel as well as the seed can be commercially valuable. Betacyanin can be also extracted from the peel, with a very similar composition of coloring compounds to that of the pulp (Harivaindaran et al., 2008). The mesocarp is cut into 0.5 cm cubes and macerated in a blender at low speed using ice-cold water (10 volume of water to 1 volume of plant tissue). Extraction of pigment is claimed to be accomplished within few minutes (Stintzing et al., 2002). Then, the slurry is filtered and concentrated under vacuum, and pectin-like substances are precipitated with ethanol. The supernatant is concentrated, and the operation can be repeated until an extract enriched in betacyanin is obtained (Stintzing et al., 2002). The mucilaginous material recovered from peel or the juice after betacyanins extraction is a valuable co-product that can be dried and powdered. The resulting product can be used in the food or cosmetic industries as a thickening or moisturizer agent (Stintzing et al., 2002), as an edible coating agent to extend fruit shelf-life during storage (Del-Valle et al., 2005), as a natural coagulant for water purification (Miller et al., 2008) or simply a dietary fiber source with functional properties. Additionally, pitahaya seeds obtained during juice extraction can yield after solar drying, grounding and pressing, high quality oil enriched in essential unsaturated fatty acids. Pitahaya seed oil is rich in linoleic acid as compared to flaxseed, rapeseed (canola), sesame seed and grape seed oils. Nonetheless, if seeds contain more than 30% oil, less than 8% w/w has been extracted at pilot plant level by pressing, and even using a combination of enzymes and microwaves (Rui et al., 2009).

12.10

Conclusions

Our bibliographical study gives an initial evaluation of the advantages and disadvantages of growing pitahaya. As far as agronomy is concerned, these species are generally hardy, easy to multiply and cultivate. In general, they produce fruits quickly and few diseases and pests are encountered at the present time. Currently, the pitahaya is a highly economical crop for the traditional producer because little or no investment is required for its cultivation. These crop systems can be intensified to achieve better performance in which case lianas tutors are necessary and sometimes shade, depending on the ecology. In addition to the high cost of the support, labor is also needed if manual pollination is performed to ensure high-quality products. Commercially, pitahayas appear to have numerous selling points; the fruits are attractive in shape and color, and they have very good internal properties of high interest for the food industry. Pitahaya juice differentiates from other fruit juices essentially by the texture or viscosity due to the presence of mucilage and in the case of red-flesh fruits, additionally by its high content of betacyanins. Preserving both compounds during processing is

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not an easy task even if from the nutritional and functional point of view it can be ideal. A second advantage of pitahaya fruits is their appealing appearance. Conventional dehydration processes do not allow preserving the initial appearance of fruit slices. Other more innovative processes should be tested such as vacuum frying, microwave coupled with vacuum drying or dehydration/impregnation process to obtain half-candied fruit slices. Preservation of fresh-cut slices is also a major issue that requires more research. It can be investigated through the use of specific packages and modified atmosphere to preserve freshness or by the use of specific syrup to obtain canned fruit slices. The aroma of pitahaya is also very subtle, highly thermosensitive and consequently very difficult to preserve during processing. White flesh-pitahaya (H. undatus) is generally claimed to be more flavorful than red-flesh pitahaya, but a comprehensive study on aroma of pitahaya is needed to identify main aromatic compounds and their precursors. Technological alternatives such as the use of specific enzymes may help to increase the flavor of pitahaya. Additionally, knowledge about the functional properties of mucilage present in pitahaya juice and peel is an important issue. Most studies have been performed on prickly pears, so little is known about polysaccharides from pitahaya fruits because current research results are still not clear. Betacyanins bioavailability is another sensitive issue that should be investigated deeper to give additional arguments to the natural food colorant market. The impact of synergy between mucilage and betacyanins as well as phenolic compounds present in pitahaya is still totally unknown although it can be a major issue to get maximum health benefits.

12.11

References

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Valencia-Botin A J, Sandoval-Islas J S, Cardenas-Soriano E, Michailides T J and RendonSanchez G (2003), ‘Botryosphaeria dothidea causing stem spots on Hylocereus undatus in Mexico’, Plant Pathol, 52, 803. Valiente-Banuet A, Santos Gally R, Arizmendi M C and Casas A (2007), ‘Pollination biology of the hemiepiphytic cactus Hylocereus undatus in the Tehuaca′n Valley, Mexico’, J Arid Environ, 68, 1–8. Wall M M and Khan S A (2008), ‘Postharvest Quality of Dragon Fruit (Hylocereus spp.) after X-ray Irradiation Quarantine Treatment’, Hortscience, 43, 2115–2119. Weiss J, Nerd A and Mizrahi Y (1994) ‘Flowering behavior and pollination requirements in climbing cacti with fruit crop potential’, Hortscience, 29, 1487–1492. Wright E R, Rivera M C, Ghirlanda A and Lori G A (2007), ‘Basal Rot of Hylocereus undatus caused by Fusarium oxysporum in Buenos Aires, Argentina’, Plant Dis, 91, 323. Wu L C, Hsu H W, Chen Y C, Chiu C C, Lin Y I and Ho J A A (2006), ‘Antioxidant and antiproliferative activities of red pitaya’, Food Chem, 95, 319–327. Wybraniec S, Stalica P, Jerz G, Klose B, Gebers N, et al. (2009), ‘Separation of polar betalain pigments from cacti fruits of Hylocereus polyrhizus by ion-pair high-speed countercurrent chromatography’, J Chrom, 1216, 6890–6899. Yah A R C, Pereira S S, Veloz C S, Sanudo R B and Duch E S (2008), ‘Sensorial, physical and chemical changes of pitahaya fruits (Hylocereus undatus) during development’, Revista Fitotecnia Mexicana, 31, 1–5. Yassen M Y (2002), ‘Micropropagation of pitaya (Hylocereus undatus Britton & Rose)’, Vitro Cell Dev Biol Plant, 38, 427–429.

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(Chapter 12) Diversity of Hylocereus sp. (© F. Le Bellec). Plate XXII © Woodhead Publishing Limited, 2011

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43 44 45X

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43 44 45X

Plate XXIII (Chapter 12) Hylocereus trigonus in agroforest system (French West Indies) (© F. Le Bellec).

Plate XXIV (Chapter 13) Red pitanga (Eugenia uniflora L.).

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13 Pitanga (Eugenia uniflora L.) M. Vizzotto and L. Cabral, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil and A. Santos Lopes, Federal University of Pará, Brazil

Abstract: Originally from Brazil, pitanga (Eugenia uniflora L.), a Dicotyledoneae, Myrtaceae, grows in tropical and subtropical regions where it is appreciated mainly for its fruits. The chapter first discusses the importance of pitanga fruit, its uses, economic and nutritional value and health benefits, then also discusses postharvest physiology and handling practices; maturity and quality components and indices, and processing of pitanga fruits. Key words: health benefits, bioactive compounds, postharvest physiology, frozen pulp.

13.1

Introduction

13.1.1 Origin, botany, morphology and structure Pitanga is an indigenous Brazilian plant from the Mirtaceae family, extending over a wide area from north to south (Lorenzi, 1992). It occurs spontaneously in the states of Minas Gerais, Rio de Janeiro, Parana, Santa Catarina, and Rio Grande do Sul. In wild form it usually grows along the banks of streams and on the edge of the forest, but it is also commonly cultivated throughout many parts of Brazil, mainly in the northeast region (Lorenzi et al., 2006). While most commonly known botanically as Eugenia uniflora L., several synonyms have been used by botanists such as E. Micheli Lam., Stenocalyx Micheli (Lam) O. Berg, S. lucidius O. Berg, E. costata Cambess., Myrtus brasiliana L., and Plinia rubra L. (Lorenzi et al., 2006). The common names of this fruit are numerous but the one most frequently used is pitanga, which is used throughout Brazil and was given to the fruit by the Tupi Indians, who inhabited the region before the Europeans arrived. In the United States it is known as Surinam-cherry, and less commonly Cayenne-cherry and Florida-cherry. In India it is called Brazil-cherry; in Sri Lanka, goraka-jambo; in France, cerise de

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Cayenne, in Spanish, cereza de Cayena (Ctenas et al., 2000); and in many cases, showing a false origin to this fruit. Pitanga forms a large shrub or a small tree 4–12 m in height. The small, opposite, ovate-lanceolate leaves are glossy green, but immature leaves have a coppery color that adds to the ornamental value of this plant. The small creamcolored flowers are produced in profusion in the axils of the leaves (Lorenzi et al., 2006). On average pitanga plants produce around 10 kg of fruits per plant (Bezerra et al., 1997). The fruit is oblate in form, conspicuously eight-to-ten-ribbed, deep orange, red and purple in color when fully ripe (see Plates XXIV and XXV in the colour section between pages 238 and 239), and crowned at the apex with the persistent calyx-lobes. As the fruits ripen they lose their green color, becoming yellow, then orange, and finally red or purple (Bezerra et al., 2000). So far there is only one cultivar of pitanga in Brazil, known as Tropicana (Lira Júnio et al., 2007). However, three different types of pitanga are recognized, according to their color. One is the pitanga-laranja or orange pitanga, one is pitanga-vermelha or red pitanga and the other is pitanga-roxa or purple pitanga (Lorenzi et al., 2006). The three types can be found in nature but the pitanga-laranja and the pitanga-roxa are rarer (Lorenzi et al., 2006). The flesh is soft, juicy, concolorous with the skin, and of aromatic sub-acid flavor. Usually there is one large round seed, but sometimes two or more hemispherical ones can be found (Bezerra et al., 2000). There is great variability in pitanga fruit characteristics such as size, color, number and size of the seeds. The seeds can be disseminated by birds, mammals, carnivores and primates, and eventually by lizards. Comparing individuals within the same native population using molecular biology techniques has shown that the great variability in fruit characteristics is due to high genetic variability. This means that areas in which the pitanga population has been degraded close to those in which it has been preserved can be regenerated without loosing genetic variability by using seeds from the pitanga populations in the preserved areas. However, the possibility of entering genetic material from more distant populations is not ruled out (Slaviero et al., 2009). 13.1.2 Importance, economic value, culinary uses and health aspects Regarding the production and marketing of pitanga, there is neither official data from Brazil nor abroad; however, it is estimated that Brazil is the largest world producer. While the pitanga grows wild in a large area in Brazil there are a few regions that produce this fruit commercially (Lorenzi, 1992; Ctenas et al., 2000), the main one being the northeast (Lorenzi et al., 2006). Pernambuco and Bahia States are the main producers (Lira Júnio et al., 2007). Cultivation in Pernambuco State, the biggest producer, is particularly abundant, covering around 300 ha (Villachica, 1996; Bezerra et al., 2000; Lira Júnio et al., 2007). Outside Brazil pitanga is commonly grown in several countries such as the United States (Florida, Hawaii and California), India, Sri Lanka, China, Algeria, France, and Cuba (Ctenas et al., 2000). In most cases it was distributed in earlier

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times by the Portuguese settlers. Despite the wide geographical distribution of pitanga, it is abundant in any location in which it is produced commercially. The uses of the pitanga are abundant. When fully ripe, it is delicious as a fresh fruit, but fresh consumption before it is fully ripe is not recommended due to its bitter flavor. Pitanga juice and ice cream are very appreciated in northeast Brazil, and it is regularly served in coffee shops. It is salmon-pink in color and delicious in flavor. A liqueur is sometimes prepared from the fruit, and also syrups and wines which are considered by the Brazilians to have medicinal value (Ctenas et al., 2000). Jelly made from pitanga has a distinctive flavor (Lorenzi et al., 2006). Pitanga has also been used as a phytocosmetic by the Brazilian cosmetics industry to develop shampoos, hair conditioners, face and bath soaps and perfumes. The therapeutic activities of pitanga leaves are well known. The leaves are referred to as effective treatments for various diseases such as fever, stomach disorders and hypertension (Schmeda-Hirschmann et al., 1987; Weyerstahl et al., 1988), rheumatism (Alice et al., 1991), bronchitis (Rivera and Obon, 1995) and diabetes and obesity (Arai et al., 1999). They are also anti-inflammatory (Schapoval et al., 1994) and have diuretic activity (Consolini et al., 1999), cardiovascular activity (Wazlawik et al., 1997; Lee et al., 2000), and antioxidant activity, inhibiting lipid peroxidation and removing free radicals (Velazquez et al., 2003). The essential oil from pitanga leaves also has interesting antioxidant activity (Marin et al., 2008). In addition, it exhibits strong antibacterial effects against Staphylococcus aureus and has an excellent cytotoxic action against human tumor cell lines PC-3 and Hep G2, while completely inhibiting the growth of Hs 578T (Ogunwande et al., 2005). Despite the many studies related to the beneficial properties of pitanga leaves, there are few published studies about the health effects of the fruit and its derivative products. According to Fetter et al. (2009), pitanga fruit at immature stages has a higher antioxidant content than fruit at mature stages, suggesting that bioactive compounds for use in the food or cosmetic industries can be extracted at early stages saving time, money and avoiding unnecessary field treatments. Also, the same authors observed a good correlation between the antioxidant activity and the phenolic content in the fruits. Healthy eating is very important to prevent non-communicable chronic diseases such as cancer and cardiovascular diseases. Pitanga fruit has been gaining attention in countries other than Brazil for its exotic flavor and vitamin content and has been recognized as a natural and healthy food. So there are great prospects for its use not only in mixed juices of other fruits, but also as an additive in beverages and in the form of refreshment powder and nectars (Bezerra et al., 2000) or any designed functional foods.

13.2

Postharvest physiology

During maturation, several biochemical changes occur in fruit, including an increase in soluble solids and a decrease in acidity. Harvesting a fragile fruit as

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pitanga at an inappropriate time can accelerate the deterioration process, causing significant postharvest losses. If the physiology of fruit maturation is understood, appropriate parameters to define the harvest period can be established and alternative methods to extend shelf life and reduce postharvest losses can be generated. Pitanga is a non-climacteric fruit; in other words it has a high respiration rate in the early stages of development that declines over the course of maturation (Santos et al., 2002; Lorenzi et al., 2006). The high perishability of pitanga fruit is usually due to its high metabolism during ripening. Therefore, inadequate management in the harvest and postharvest periods accelerates the processes of maturation and senescence, affecting fruit quality significantly and limiting the marketing period. In particular, the stage of maturation at which the fruit is harvested determines the final quality for the consumer. Fruits harvested unripe are of poor quality, have high rates of water loss and are very susceptible to physiological disorders. On the other hand, fruits harvested very ripe have a very short shelf life. Santos et al. (2002) evaluated two types of pitanga fruits (red and purple) and observed that purple fruits have one more maturity stage than red fruits, because the red type has a shorter maturity cycle. The authors established five maturation stages for the red variety and six stages for the purple variety. There is a rapid anthocyanin accumulation in purple fruits in the last maturation stage which gives the fruit an attractive appearance and characterizes its ripeness. Table 13.1 and 13.2 show the maturation stages parameters for the red and purple varieties, Table 13.1

Changes during maturation of red pitanga fruit

Parameters

Maturation stages*

Diameter (mm) Length (mm) Fresh weight (g) Dry matter (%) Edible portion (%) (skin+pulp) Seeds (%) Firmness (N) Soluble solids (%) Total titratable acidity (% citric acid) pH Ratio (soluble solids/titrable acidity) Vitamin C (mg.100 g−1) Total anthocyanins (mg.100 g−1) Respiratory activity (mg CO2.kg fruit−1.hour−1)

1

2

3

4

5

19.9 13.2 3.54 19.02 72.36 27.61 21.36 8.13 0.86 3.36 9.42 22.50 0.00 25.50

21.4 14.3 4.25 19.44 70.40 29.69 20.13 8.96 1.23 3.11 7.25 26.93 0.09 23.27

21.7 15.0 4.65 18.26 76.14 23.86 10.91 10.33 1.61 3.13 6.46 40.65 0.29 19.87

22.4 15.1 5.25 17.83 79.60 20.41 8.16 11.00 1.58 3.16 7.12 51.00 0.51 18.53

21.2 14.6 4.40 18.81 74.95 25.04 8.77 12.56 1.57 3.28 7.99 33.00 0.98 14.90

* 1 – Green; 2 – Breaker (start skin color transition); 3 – Beginning red pigmentation; 4 – Partially red; 5 – Completely red. Source: Santos et al. (2002).

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Table 13.2

Changes during maturation of purple pitanga fruit Maturation stages*

Parameters

Diameter (mm) Length (mm) Fresh weight (g) Dry matter (%) Edible portion (%) (skin+pulp) Seeds (%) Firmness (N) Soluble solids (%) Total titratable acidity (% citric acid) pH Ratio (soluble solids/titrable acidity) Vitamin C (mg.100 g−1) Total Anthocyanins (mg.100 g−1) Respiratory Activity (mg CO2.kg fruit−1.hour−1)

1

2

3

4

5

6

17.9 14.3 2.56 26.26 64.73 35.26 17.30 8.53 1.66 3.38 5.67 21.85 0.00 28.30

17.8 13.9 2.56 24.70 71.76 28.20 17.92 9.73 1.74 3.29 6.16 29.15 2.40 26.77

17.8 15.1 2.96 22.36 72.35 27.64 6.68 10.76 1.98 3.24 5.83 32.85 9.40 26.33

17.8 15.0 3.37 23.51 69.06 30.93 4.47 12.53 1.55 3.43 7.04 42.65 16.30 23.43

17.0 14.6 2.67 22.86 65.73 34.26 5.41 10.56 1.73 3.28 7.04 55.00 21.60 20.83

17.6 15.1 3.32 24.41 61.76 38.23 4.80 13.04 1.64 3.55 10.61 38.35 29.60 17.33

* 1 – Green; 2 – Breaker (starting to change shell’s color); 3 – Beginning purple pigmentation; 4 – Partially purple; 5 – Completely purple; 6 – Dark purple. Source: Santos et al. 2002.

respectively. Measuring the increase in soluble solids content gives a good indication of the maturation level of the fruits. This is a simple and efficient maturity index.

13.3

Maturity and quality components and composition

In general, the purple pitanga is smaller, softer and sweeter than the other types of pitanga (Santos et al., 2002; Lorenzi et al., 2006). Red pitanga is on average larger than purple pitanga: the diameters of red and purple pitanga fruits measured by Santos et al. (2002) were 1.99–2.24 cm and 1.70–1.79 cm, respectively. In both types a smaller alteration in length than in diameter during maturation has been observed, indicating that fruits of pitanga have a tendency to swell during development (Santos et al., 2002). Also, when the pitanga fruits are mature the red type is firmer than the purple type (Santos et al., 2002; Lorenzi et al., 2006). Mature red pitanga has, on average, a firmness of 9 N, total soluble solids 12%, acidity 1.6% of citric acid, pH 3.3, and ratio (total soluble solid/acidity) of 8. Purple fruit has an average firmness of 5 N, total soluble solids 13%, acidity 1.6% of citric acid, pH 3.5, and ratio (total soluble solid/acidity) close to 11. The fresh weight of both varieties increases continuously, while the dry weight increases at the first maturation stages and decreases thereafter. At the final maturation stage there is an increase in dry weight indicating the end of ripening

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when the fruit begins to accumulate water. On average 66–69% of the weight of pitanga fruit is pulp and 31–34% seeds (Guimarães et al., 1982; Villachica, 1996). However this ratio can vary with pitanga type. Red pitanga can have 75% pulp and 25% seeds while purple pitanga can have 62% of pulp and 38% of seeds (Santos et al., 2002). The majority volatile compounds found in pitanga fruits include sesquiterpenes (α-Cubebene, Germacrene B and Spathulenol) and ketones (β-Damascenone, 2(4H)-Benzofuranone, 5,6,7,7a-tretraidro-4-4-7a-trimethyl, Selina-1,3,7(11)-trien8-ona, 2-Benzothiazolinone and 3,7-Ciclodecadien-1-one, 10-(1-methylethenyl)-(E, E)-), which are also present in essential oil from leaves. Extracts from the fruit obtained by Oliveira et al. (2009) also contained caffeine, vitamin E and γ-sitosterol (a phytosterol used to reduce blood cholesterol levels). The following long chain hydrocarbons, part of the fruit wax, were also present in the extracts: Eicosane, Heneicosane, n-Docosane, Eicosane, 10-methyl-, n-Tricosane, n-Pentatriacontane, n-Hexatriacontane and Tritetracontane. Volatile phenolic compounds such as 2,4-Bis(dimethyl benzyl)phenol (to which antioxidant properties have been attributed) are present in the extracts in high proportion as well (Oliveira et al., 2009). The major monoterpenes found in the pitanga fruits are trans-β-ocimene, followed by cis-ocimene, the isomeric β-ocimene and β-pinene (Oliveira et al., 2006a). Studies of the mineral composition of pitanga have shown that this fruit has considerable concentrations (expressed as mg 100 g−1 of edible dry fruit) of potassium (806), calcium (191), manganese (0.9), iron (5.2), copper (0.6), zinc (1.2) (Oliveira et al., 2006b). The vitamin C content is relatively high ranging from 21.85 to 55.0 mg of ascorbic acid equivalent to 100 g−1. The highest concentration of vitamin C in the fruit is when it is mature; however it decreases when fruits are at overripe stage (Santos et al., 2002). Regarding the anthocyanin concentration, there are variations in the total content among the three types of pitanga. Also, regardless of the type studied there is an increase in anthocyanin content as the fruit matures, indicating synthesis of these compounds, just as in other fruits (Fetter et al., 2009), and the rapid accumulation of these pigments in the later stages of maturation provides an attractive appearance, characteristic of ripe fruit. The total anthocyanin concentration in red pitanga can vary from around zero at green stage to 50 mg cyanidin-3-glycoside equivalent 100 mg−1 of fresh weight when the fruit is completely mature (Fetter et al., 2009). Two anthocyanins have been identified in pitanga, cyanidin-3-glycoside and delphinidin-3-glycoside (Einbond et al., 2004). The total phenolic content of red pitanga is higher in immature fruits than mature fruit (Fetter et al., 2009). Its content can vary from around 960 mg of chlorogenic acid equivalent 100 mg−1 of fresh weight when at green stage to 587 mg of chlorogenic acid equivalent 100 mg−1 of fresh weight when the fruit is completely mature (Fetter et al., 2009). The flavonols content in purple pitanga is around 14 mg 100 g−1 (Lima et al., 2002). Among the existing fruits in nature, pitanga is the one with the highest carotenoid content (225.9 μg g−1) and also has considerable vitamin A value

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(991 ER 100 g−1). Among the identified carotenoids in pitanga are phytofluene, β-carotene, ζ-carotene, β-criptoxantin, γ-carotene, lycopene, rubixanthin, cisrubixanthin, cis-lycopene, zeaxanthin, lutein, violaxanthin and β-carotene-5, 6-epoxide (Azevedo-Meleiro and Rodriguez-Amaya, 2004; Filho et al., 2008; Cavalcante, 1991). Lycopene is the most abundant representing 32% of the total carotenoid amount (Cavalcante, 1991). The total carotenoid content increases with maturation reaching its maximum pick at overripe stage (Fetter et al., 2009). Pitanga seeds, which are low in protein and fat, are a good source of insoluble dietary fiber and the seed extracts have a powerful antioxidant capacity that is partially correlated to their high phenolic content. Therefore, this low value waste of pitanga processing can be used as a source of natural antioxidants and dietary fiber for animal and/or human nutrition (Bagetti et al., 2009). Pitanga seeds also have a high proportion of unsaturated fatty acids (60–70%) being 13–16% monounsaturated fatty acids (MUFA) and 45–47% polyunsaturated fatty acids (PUFAS) (Bagetti et al., 2009). PUFAS, especially the n-3 fatty acids, are considered desirable compounds in the human diet because of their effect in reducing the incidence of cardiovascular disease. Some physical and chemical factors relating to maturation depend on fruit position on the tree (Pio et al., 2005) and more general environmental factors. For example, pitangas in apical position have a more oval shape and higher pulp yield and total soluble solids (Pio et al., 2005), probably due to higher luminosity incidence. Fruits produced in different Brazilian states have different amounts of carotenoids (Azevedo-Meleiro and Rodriguez-Amaya, 2004).

13.4

Postharvest handling factors affecting quality

13.4.1 Temperature management Temperature is one of the most important environmental factors that can affect the shelf life and quality maintenance of fruits during postharvest. Many metabolic processes depend on temperature and the storage temperature can reduce or increase the incidence and severity of some physiological disorders. Low storage temperatures are favorable to the reduction in rates of respiration and metabolism (Wills et al., 1989; Cheftel and Cheftel, 1992; Kays, 1997). As important as the use of low storage temperature, is rapid cooling or pre-cooling fruit after harvest. A delay in cooling after harvest promotes rapid deterioration of the fruits (Wills et al., 1981; Cheftel and Cheftel, 1992). According to Melo et al. (2000) the storage of pitanga fruit under refrigeration (8 °C) allows quality to be maintained for five days, but beyond this period intense physical-chemical alterations may occur. However, the fruit’s sensibility to lower temperatures can result in damage, decreasing its storage period (Morris, 1982). Melo et al. (2000) recommend fruit preservation by freezing only for the fruits which will be processed.

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13.4.2 Atmosphere Santos et al. (2002) evaluated postharvest changes in red pitanga fruits harvested in the red-orangish (RO) and predominantly red (PR) maturity stages kept under modified atmosphere (MA) by polyvinyl chloride film (PVC), at 10 ± 0.5 °C, 14 ± 0.5 °C, 90 ± 1% RH (relative humidity) and room temperature (23 ± 2 °C). The use of modified atmosphere associated with refrigeration maintained total soluble solids, titratable acidity, soluble sugars, and vitamin C, lowered the rate of increase of total carotenoids (Santos et al., 2002), and resulted in lower mass loss, incidence of fungi and wrinkling (Santos et al., 2006). It can be concluded that modified atmosphere associated with refrigeration of 10 °C allow a four-day increase in shelf life, keeping the quality above the limit of acceptance for eight days for pitanga fruits harvested at the orange-red skin color stage.

13.5

Postharvest handling practices

13.5.1 Harvest operations Pitanga is a perishable fruit, susceptible to mechanical injuries, physiological deterioration and high water loss. These factors make its storage and commercialization at long distances from the orchard difficult. As mentioned above, after harvesting, cooling can delay non desirable changes in quality and increase shelf life (Melo et al., 2000; Santos et al., 2002), but the fruit can also be damaged by low temperature storage beyond a certain period of time (Morris, 1982). Pitanga fruit are harvested after 50 days from flowering. The fruit have to be harvested carefully and stored in plastic bags, under shadow and covered to avoid injuries, dust deposition and sunburn (Lederman et al., 1992; Bezzerra et al., 1997). It is good practice to harvest the fruit periodically after the maturation period to minimize the number fruit that fall and are damaged by contact with the soil. The mature fruit are very sensitive and any bruise or stress can result in the peel being ruptured and fermentation being initiated. It must be pointed out that the fruit can support storage for up to 24 hours after harvest at room temperature. 13.5.2 Control of ripening and senescence The short shelf life of fresh pitanga fruits makes the use of modified atmospheres attractive to minimize fungal infections and extend the commercialization period. The postharvest changes in mature red pitanga fruits kept under modified atmosphere by polyvinyl chloride film (PVC), at 10 °C, 14 °C, 90 RH and room temperature were evaluated. This modified atmosphere resulted in maintenance of the acidity, vitamin C, chlorophyll and carotenoid content of pitanga fruits during a period of eight days, independent of the maturation stage. The temperature of 10 °C was found to be ideal (Santos et al., 2006). Packaging plays a decisive role in the improvement of fruit shelf life and new packaging materials are being developed, most of them are derived from renewable

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resources. Edible coatings act by creating a modified atmosphere surrounding the commodity, similar to that achieved by controlled or modified atmospheric storage conditions. Taking into account the surface and permeability properties of the obtained films, a filmogenic solution of 1.5% of galactomannan and 1% of glycerol has been selected to be used on pitanga fruits. This formulation should be either applied by immersion or sprayed on the fruits and let dry at room temperature during three hours (Cerqueira et al., 2009).

13.6

Processing

13.6.1 Processing practices As fresh pitanga is very difficult to commercialize due to its high perishability and susceptibility to physical damage during transportation, processing the fruit in the regions of cultivation into frozen pulp and integral juices is recommended. Pitanga is very suitable for processing into pulp on an industrial scale due to its high pulp yield, pleasant aroma and exotic flavor. The pulp is the raw material for the production of different products such as juice, nectars, ice cream, jellies and liquors. The wide range of fruit raw materials, natural and manufactured juice ingredients and juice preparation and processing methods, provide the food technologist with a practically infinite range of possibilities for developing juice products varying in quality, price and value. In the Brazilian food industry, the pitanga fruit has mostly been used to produce juice. This product has good economic potential due to its consumer appeal arising from its high concentration of antioxidant compounds, such as anthocyanins, flavonols and carotenoids. Pitanga pulp In general, the fruits destined for pulping should be of good edible quality and full flavor and be substantially more mature than fresh market fruit. Such fruit have softer tissues (which are more amenable to pulp extraction and generate a higher yield), higher sugar content, a deeper color and a lower acid content. However, overripe fruit is inappropriate as the flavor and acidity may suffer. Figure 13.1 shows the main steps for the production of pitanga frozen juice, which can then be processed at a later stage into pasteurized and concentrated pitanga juices. The fruit are first sorted, washed and drained. The fruit are usually washed in a mechanical washer that combines immersion bathing for the removal of the sludge with an aspersion system (Tocchini et al., 1995). The fruit entering a processing operation are sorted to remove damaged fruit, diseased or rotten fruit. When performed improperly the contamination level can actually be increased during pulp and juice processing. Thus sanitation of equipment and water sanitation with chlorination is critical and the recovery of the sanitation solutions tube recycled have been pointed out as usually necessary (Soler et al., 1991). The fruit is pulped to separate the edible pulp from the fibrous materials, seeds, peels, etc., and also, to reduce the size of the particles of the product, making it more homogeneous. Pitanga pulp extraction was studied using two depulpers: an

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Main steps for the production of pitanga frozen juice, pitanga pasteurized and concentrated frozen juices.

inclined brush depulper and a horizontal blade depulper. The brush and blade depulpers presented yields of 58.47 ± 3.93% and 46.61 ± 1.80%, respectively, on pulping pitanga fruits. According to the sensory analyses, there was no significant difference for the attributes aroma and flavor between the pitanga nectars formulated with pulps obtained from the two depulpers. Therefore a brush depulper should be used rather than a blade depulper. Frozen pitanga pulp is commonly packaged for commercialization in the internal market in plastic bags in portions of 100, 200 and 400 g. If the pulp is to be used as a raw material in other industries, drums of 200 kg can be used. The effects of process time and temperature during heat pasteurization on color (a*, b*) and enzyme activity of pitanga pulp was studied. The process was optimized from the more important responses in the experimental design: variation in a* color coordinate and decrease in pectinmethylesterase activity. The optimized time and temperature range for heat processing, obtained from the superposition of the response level curves, was between 59 and 68 seconds at about 90 °C. The pulp can be clarified with specific enzymatic preparations that act on fibers and pectin making it less viscous and cloudy. Albumin, gelatin, casein or bentonite can also be used to improve pulp clarity. Figure 13.2 shows the main steps to produce a clarified pitanga pulp. The stability of pitanga pulp during frozen storage at −18 °C was evaluated after different storage periods. By the sensory analysis, it was verified that pulp

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Fig. 13.2

Flow sheet of clarified pitanga juice.

appearance changed significantly after 90 days of frozen storage. Thus there was a marked fall in the sensory acceptance of nectar formulated with pitanga pulp that had been stored for 90 days at −18 °C and customers had a less positive attitude towards its purchase. Moreover, though pitanga pulp has good stability when stored under −18 °C, the level of carotenoids decreases. This mainly happens during the first 30 days of storage; the level remains practically constant after this period (Lopes et al., 2005). Frozen storage has little effect on the pitanga anthocyanin content (Lima et al., 2005). Pitanga juice Tropical pitanga juice is typically a non fermented beverage obtained from the edible part of the fruit through appropriate industrial processes. The juice must present the following characteristics: color: red; flavor: acid and characteristic; aroma: characteristic; pulp content: 60%; soluble solids content at 20 °C: 5.0 °Brix; total acidity: 0.50 g citric acid 100 g−1; total natural sugar: 8.60 g 100 g−1. Juices and nectars are often made on an industrial scale from frozen pulp. Figure 13.3 shows the main steps to produce a pitanga tropical juice or pitanga nectar from frozen pulp. The most important method for preserving fruit juices is pasteurization, which involves heating up the juice to a determined temperature for a period of time that will destroy microorganisms that can multiply and reduce the quality and safety of the product. Flash pasteurization involves heating up of the juice to its boiling point (greater than 88 °C) for 25 to 30 seconds. Even if a pasteurized pulp is used as raw material to make the juice or nectar, the final product needs to be pasteurized to be sold as pasteurized juice or nectar. Vacuum concentration reduces the boiling point of the juice and, when combined with short exposure to high evaporation temperatures, reduces heat

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Flow sheet of pitanga tropical juice or nectar.

damage. Since vacuum concentration strips the natural aroma from the juice, quality suffers. However, when producing concentrated pulp or juice, the addition of aromas recovered after the process is permitted. Water removal by concentration greatly simplifies juice handling, storage and shipping logistics. High Brix is limited by viscosity build-up due to the presence of pectin substances and insoluble solids or pulp. In the concentrated and frozen or refrigerated form the juice can be held for extended periods, shipped, or stockpiled for future use. Indeed, the global trade in frozen concentrate has profoundly influenced juice and juice beverage developments, since long term stability and ease of transport make concentrates a readily available commodity. Concentrates must be maintained cool, if not frozen to prevent quality loss primarily through Maillard browning type reactions affecting color and flavor. Apart from this, the main factors determining consumer acceptance are the knowledge of the introduction of good manufacture practices in the pulp industries and the final quality of the product. Single strength juice is generally commercialized at room temperature in 500 ml glass bottles with chemical additives and in ‘Tetra Pak’ cartons. Processing and formulation practices affect pitanga product characteristics. Oliveira et al. (2006c) carried out a comparative analysis of the physiochemical characteristics of pitanga pulp, pitanga pulp formulated with maltodextrin and spray-dried pitanga powder. In the pitanga pulp and formulated pulp the total

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soluble solids (°Brix), pH, levels of total moisture soluble solids, proteins, alcoholic extract, total titratable acidity, reducing sugars, ash and ascorbic acid and color parameters brightness (L*), redness (+a*) and yellowness (+b*) were determined. All of the parameters were statistically different. Powder samples collected from the drying chamber and cyclone had significantly different values of moisture, reducing sugars, alcoholic extract, density and time of drainage; but statistically similar average values of ascorbic acid, total titratable acidity and protein (Oliveira et al., 2006c).

13.7

Conclusions

Pitanga is an indigenous fruit from Brazil. It can be eaten fresh or used to make juice, jam, ice cream, and liquor among other products. The exotic flavor and high vitamin content together with carotenoid, anthocyanin and phenolic contents may provide a good source of health-promoting antioxidants. It is a very delicate nonclimacteric fruit that responds very well to refrigerated storage at temperatures around 8–10 °C allowing a fairly good shelf life. Some alternative postharvest technologies such as modified atmospheres can also be used to improve shelf life.

13.8

References

Alice C B, Vargas V M F, Silva G A A B, Siqueira N C S de, Schapoval E E S, et al. (1991), ‘Screening of plants used in South Brazilian folk medicine’, J Ethnopharmacol, 35, 165–171. Arai I, Amagaya S, Komatsu Y, Okada M, Hayashi T, et al. (1999), ‘Improving effects of extracts of Eugenia uniflora on hyperglycemia and hypertriglyceridemia in mice’, J Ethnopharmacol, 68, 307–314. Azevedo-Meleiro C H and Rodriguez-Amaya D B (2004), ‘Confirmation of the identity of the carotenoids of tropical fruits by HPLC-DAD and HPLC-MS’, J Food Compos Anal, 17, 385–396. Bagetti M, Facco E M P, Rodrigues D B, Vizzotto M and Emanuelli T (2009), ‘Antioxidant capacity and composition of pitanga seeds’, Ciênc Rural, 39(8), 2504–2510. Bezerra J E F, Preitas E V de, Pedrosa A C, Lederman I E, Dantas A P (1997), ‘Performance of surinam cherry (Eugenia uniflora L.) in Pernambuco, Brazil. II – Productive period 1989–1995’, Acta Hort, 452, 137–142. Bezerra J E F, Silva Júnior J F and Lederman I E (2000), Pitanga (Eugenia uniflora L.), Jaboticabal, FUNEP. Cavalcante M L (1991), ‘Composição de carotenóides e valor de vitamina A em pitanga (Eugenia uniflora L.) e acerola (Malpighia glabra L.)’, Master’s Dissertation, Universidade Federal do Rio de Janeiro, Rio de Janeiro. Cerqueira M A, Lima A M, Teixeira J A, Moreira R A, Vicente A A (2009) ‘Suitability of novel galactomannans as edible coatings for tropical fruits’, Food Eng, 94, 372–378. Cheftel J C and Cheftel H (1992), Introducción a la bioquímica y tecnología de los alimentos, Zaragoza, Acribia. Consolini A E, Baldini O A N and Amat A G (1999), ‘Pharmacological basis for the empirical use of Eugenia uniflora L. (Myrtaceae) as antihypertensive’, Ethnopharmacol, 66, 33–39.

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Ctenas M L de B, Ctenas A C and Quast D (2000), Frutas das Terras Brasileiras, São Paulo, C2 Editora e consultoria em nutrição. Einbond L S, Reynertson K A, Luo X-D, Basile M J and Kennelly E J (2004), ‘Anthocyanin antioxidants from edible fruits’, Food Chem, 84, 23–28. Fetter M da R, Corbelini D D, Vizzotto M and Gonzalez T N (2009), ‘Compostos bioativos e atividade antioxidante de pitanga (Eugenia uniflora L.) diferentes estádios de maturação’, Anais do XVIII Congresso de Iniciação Científica, XI EMPOS e I Mostra Científica da Universidade Federal de Pelotas, Universidade Federal de Pelotas, Available at: http://www.ufpel.tche.br/cic/2009/cd/pdf/CA/CA_00884.pdf [acessed 31 May 2010]. Filho G L, Rosso V V de, Ângela M, Meireles A, Rosa P T V, Oliveira A L, et al. (2008), ‘Supercritical CO2 extraction of carotenoids from pitanga fruits (Eugenia uniflora L.)’, Supercritic Fluid, 46, 33–39. Guimarães F A, Holanda L F F, Maia G A and Moura Fé J A (1982), ‘Estudos analíticos e físicos em polpa e semente de pitanga (Eugenia uniflora L.)’, Ciênc Tecnol Aliment, 2, 2, 208–215. Kays S J (1997), Postharvest Physiology of Perishable Plant Products, Athens, AVI. Lederman I E, Bezerra J E F and Calado G (1992), A pitangueira em Pernambuco, Recife, IPA. Lee M-H, Chiou J-F, Yen K-Y and Yang L-L (2000), ‘EBV DNA polymerase inhibition of tannins from Eugenia uniflora’, Cancer Lett, 154, 131–136. Lima V L A G de, Melo E A and Lima D E S (2002), ‘Fenólicos e carotenóides totais em pitanga’, Scient Agric, 59, 3, 447–450. Lima V L A G de, Melo E A and Lima D E S (2005), ‘Efeito da luz e da temperatura de congelamento sobre a estabilidade das antocianinas da pitanga roxa’, Ciênc Tecnol Aliment, 25, 1, 92–94. Lira Júnio J S de, Bezerra J E F, Lederman I E, Silva Júnior J F de (2007), Pitangueira, Recife, IPA. Lopes A S, Mattietto R and Menezes H (2005), ‘Estabilidade da polpa de pitanga sob congelamento’, Ciênc Tecnol Aliment, 25, 553–559. Lorenzi H (1992), Árvores Brasileiras, São Paulo, Editora Plantarum Ltda. Lorenzi H, Bacher L, Lacerda M, and Sartori S (2006), Frutas Brasileiras e Exóticas Cultivadas, São Paulo, Editora Plantarum Ltda. Marin R, Apel M A, Limberger R P, Raseira M C B, Pereira J F M and Zuanazzi J A (2008), ‘Volatile components and antioxidant activity from some Myrtaceous fruits cultivated in Southern Brazil’, Lat Am J Pharm, 27, 172–177. Melo E A, Lima V L A G and Nascimento P P (2000), ‘Temperatura no armazenamento de pitanga’, Sci Agric, 57, 4, 629–634. Morris L L (1982), ‘Chilling injury of horticultural crops: an overview’, HortScience, 17, 2, 161–162. Ogunwande I A, Olawore N O, Ekundayo O, Walker T M, Schmidt J M and Setzer W N (2005), ‘Studies on the essential oils composition, antibacterial and cytotoxicity of Eugenia uniflora L.’, Int Aromather, 15, 147–152. Oliveira A L, Lopes R B, Cabral F A and Eberlin M N (2006a), ‘Volatile compounds from pitanga fruit (Eugenia uniflora L.)’, Food Chem, 99, 1–5. Oliveira A L de, Almeida, E de, Silva F B D R da end Filho V F N (2006b), ‘Elemental contents in exotic brazilian tropical fruits evaluated by energy dispersive X-ray fluorescence’, Sci Agric, 63, 1, 82–84. Oliveira F M N, Figueiredo R F and Queiroz A J M (2006c), ‘Análise comparativa de polpas de pitanga integral, formulada e em pó’, Rev Bras Prod Agroind, 8, 25–33. Oliveira A L, Kamimura E S and Rabi J A (2009), ‘Response surface analysis of extract yield and flavour intensity of Brazilian cherry (Eugenia uniflora L.) obtained by supercritical carbon dioxide extraction’, Innovative Food Sci Emerg Technol, 10, 189–194.

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Pio R, Gontijo T C A, Ramos J D and Chalfun N N J (2005), ‘Physical-chemical characterization of Surinam cherry fruits according to the disposition and height in the plant’, R Bras Agrociência, 11(1), 105–107. Rivera D and Obon C (1995), ‘The ethnopharmacology of Madeira and Porto Santo Island: a review’, Ethnopharmacol, 46(2), 73–93. Santos A F dos, Silva S de M, Mendonça R M N, Silva M S da, Alves R E, Filgueiras A C (2002), ‘Alterações Fisiológicas Durante a Maturação de Pitanga (Eugenia uniflora L.)’, Proc Interamer Soc Trop Hort, 46, 52–54. Santos A F dos, Silva S M and Alves R E (2006), ‘Armazenamento de pitanga sob atmosfera modificada e refrigeração: I-transformações químicas em pós-colheita’, Rev Bras Frutic, 28(1), 36–41. Schapoval E E S, Silveira S M, Miranda M L, Alice C B and Henriques A T (1994), ‘Evaluation of some pharmacological activity of Eugenia uniflora leaves’, Ethnopharmacol, 44, 137–142. Schmeda-Hirschmann G, Theoduloz C, Franco L, Ferro E and Arias A R de (1987), ‘Preliminary pharmacological studies on Eugenia uniflora leaves: xanthine oxidase inhibitory activity’, Ethnopharmacol, 21, 183–186. Slaviero L B, Miotto S P, Kubiak G B, Aguiar R V de, Zanella C A, et al. (2009), ‘Variabilidade genética de Eugenia uniflora L. em áreas conservadas e em regeneração’, Anais do III Congresso Latino Americano de Ecologia, São Lourenço, Available at: http://www.seb-ecologia.org.br/2009/resumos_clae/241.pdf [acessed 31 May 2010]. Soler M P, Radomille R G and Tocchini R P (1991), ‘Processamento’, in Soler M P et al., Industrialização de Frutas, Campinas, Instituto de Tecnologia de AlimentosITAL, 53–113. Tocchini R P, Nisida A L A C and De Martin Z J (1995), Industrialização de polpas, sucos e néctares de frutas, Instituto de Tecnologia de Alimentos. Velázquez E, Tournier H A, Buschiazzo P M de, Saavedra G and Schinella G R (2003), ‘Antioxidant activity of Paraguayan plants extracts’, Fitoterapia, 74, 91–97. Villachica H (1996), Frutales y hortalizas promisorios de la Amazonia. Tratado de Cooperacion Amazonica, 228–213. Wazlawik E, Silva M A da, Peters R R, Correia J F, Farias M R, et al. (1997), ‘Analysis of the role of nitric oxide in the relaxant effect of the crude extract and fractions from Eugenia uniflora in the rat thoracic aorta’, Ethnopharmacol, 49(4), 433–437. Weyerstahl P, Marschall-Weyerstahl H, Christiansen C, Oguntimein B O and Adeoye A O (1988), ‘Volatile constituents of Eugenia uniflora leaf oil’, Plant Med, 54, 546–549. Wills R H H, Lee T H, Graham D, McGlasson W D and Hall E G (1981), Postharvest: An Introduction to the Physiology and Handling of Fruit and Vegetables, London, AVI. Wills R H H, Lee T H, Graham D, McGlasson W D and Hall E G (1989), Postharvest: An Introduction to the Physiology and Handling of Fruit and Vegetables, Oxford, Blackwell Scientific.

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Plate XXIII (Chapter 12) Hylocereus trigonus in agroforest system (French West Indies) (© F. Le Bellec).

Plate XXIV (Chapter 13) Red pitanga (Eugenia uniflora L.).

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Plate XXV

Plate XXVI

(Chapter 13) Purple pitanga (Eugenia uniflora L.).

(Chapter 14) Chilling injury symptoms in pomegranate fruit (Kader et al., 1984).

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14 Pomegranate (Punica granatum L.) M. Erkan, Akdeniz University, Turkey and A. A. Kader, University of California, Davis, USA

Abstract: During the past decade, research and development activities on pomegranate fruit were focused on the application of new postharvest storage technologies to extend the storage life and keeping the original quality of the freshly harvested fruits. These technologies included use of fungicides to control decay, and modified atmosphere packaging or controlled atmosphere storage to maintain postharvest quality and to alleviate chilling injury symptoms which occur during the storage of pomegranates below 5–7 °C, depending on the variety and storage duration. Today, consumption of fresh pomegranates and their juice is booming due to the mounting evidence about their health benefits. Pomegranate juice processing allows the use of fruits with external defects that do not influence aril quality. These fruits and the remaining tissues after juice extraction may be used for preparation of new products, such as flavonoids capsules and other nutraceuticals. This chapter provides an overview of postharvest biology and technology of pomegranates in relation to maintaining their quality between harvest and fresh consumption or processing. Key words: pomegranate, Punica granatum, controlled atmosphere, modified atmosphere packaging, arils.

14.1

Introduction

This chapter provides an overview of the postharvest biology and technology of pomegranates in relation to maintaining their postharvest quality between harvest and fresh consumption or processing.

14.1.1 Origin, botany, morphology and structure The pomegranate, Punica granatum L., belongs to the Punicaceae family, is native to central Asia and is one of the oldest known edible fruits. The name pomegranate derives from the latin name of the fruit Malum granatum which

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means grainy apple (Holland et al., 2009). From its origin in what is now Iran and Afghanistan, the pomegranate spread east to India and China and west to Mediterranean countries such as Turkey, Egypt, Tunisia, Morocco, and Spain, among others. Spanish missionaries brought the pomegranate to the Americas in the 1500s (Hodgson, 1917; LaRue, 1980). The primary commercial pomegranate growing regions of the world are the Near East, India and surrounding countries, and southern Europe. Nearly all production in the USA is centered in the southern San Joaquin Valley of California (LaRue, 1980), with about 4000 hectares predominately growing the ‘Wonderful’ variety. The pomegranate is a shrub or a small tree up to 3–8 meters high, evergreen in the tropics and deciduous in subtropical and temperate zones. However, there are several evergreen pomegranates in India (Singh et al., 2006). In addition, there are dwarf cultivars that do not exceed 1.5 m (Levin, 2006; Holland et al., 2009). The pomegranate plant is generally spiny, deciduous, with small, narrow, oblong leaves with short stems. The pomegranate fruit develops from the ovary and is a fleshy berry 6.25 to 12.5 cm wide, and weighs 200 to 650 grams (Fig. 14.1). The nearly round fruit is crowned by a prominent calyx and connected to the tree by a short stalk

Fig. 14.1

Pomegranate fruits at different sizes.

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(Holland et al., 2009). The pomegranate has a leathery smooth skin and is divided by thin inedible membranes into a number of cells, each packed full of angular seeds contained in a juicy pulp sac. Fruits may be white/green, pink or red with a yellow background on the exterior; the pulp color follows that of the exterior. There are some exceptional cultivars with a black external color. The arils (Fig. 14.2) contain a juicy edible layer that develops entirely from outer epidermal cells of the seed which elongate in a radial direction. The arils vary in size and the seeds vary in hardness among different varieties. Varieties known as seedless actually contain soft seeds (Holland et al., 2009). Fruit skin thickness varies among the cultivars grown in different parts of the world. The wild genotypes have higher aril hardness as well as higher seed hardness and toughness (Al-Said et al., 2009). In general, cultivars grown in different parts of the world show variations in morphology, physico-chemical and textural properties of arils and seeds (Al-Kahtani, 1992; Gil et al., 1995; Al-Said et al., 2009). As noted earlier, the pomegranate is mainly confined to the tropics and subtropics and grows well in arid and semi-arid climates. The optimal climatic growing conditions for pomegranate exist in the Mediterranean region, where the

Fig. 14.2

Pomegranate arils.

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fruit grows below 1000 m in altitude (Blasco et al., 2009). Favorable growth takes place where winters are mild and summers are hot without rain during the last stages of the fruit development. It has the ability to withstand frosty conditions, but will not survive long at temperatures below −12 °C (Levin, 2006). Areas with high relative humidity or rain are totally unsuitable for its cultivation, as fruits produced under such conditions tend to taste less sweet and are prone to cracking (Glozer and Ferguson, 2008). 14.1.2 Worldwide importance and economic value Apart from the increasing demand for fresh pomegranate fruits and juice, processed products like pomegranate wine and candy are also gaining importance in world trade. All parts of the pomegranate tree have a value and are used in the leather and dyeing industries. Demand in the international market has increased the profitability of this crop. The total world production is estimated currently at 2 million tons/year. However, there are no reliable statistics for pomegranate production when compared to other commodities. At present almost all of the world’s pomegranate production is in the northern hemisphere. The main producing and exporting countries are given in Table 14.1. In terms of export, the USA exports mostly pomegranate juice; Spain, Turkey, Iran and India are exporters of fresh fruit and juice to European markets, including Russia and Ukraine; and Israel exports both fresh fruit and packaged arils. There is a window of opportunity for countries in the southern hemisphere to provide fruit to these markets out of season when fruit is not available, particularly as storage of the fruit is limited to 2–6 months depending on the cultivars (Chamber of Commerce in Antalya, Turkey, personal communication).

Table 14.1 Top pomegranate producing countries in 2007 Countries

Production (×1000 metric tons)

India Iran USA Turkey Spain Iraq Afghanistan Azerbaijan Egypt Uzbekistan Israel

900 800 110 80 80 80 75 65 43 35 25

Sources: USDA, Foreign Agriculture Service; Spain and Iran Pomegranate Boards; and Egyptian Ministry of Agriculture and Land Reclamation.

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14.1.3 Culinary uses, nutritional value and health benefits The global production and consumption of pomegranate has greatly expanded in recent years, together with the recognition of the health-promoting potential of various components of this fruit (Aviram et al., 2008). Pomegranates are mainly grown for fresh consumption of arils or juice, although in various countries they are also used for syrup, jams, carbonated beverages or wine, and in the beverage industry as flavoring and coloring agents (LaRue, 1980; Kumar, 1990; Adsule and Patil, 1995; Roy and Waskar, 1997; Gil et al., 2000; Maestre et al., 2000; Kader, 2006). In many parts of the world, pomegranate kernels are also used as a garnish for salads and deserts. In addition to its use in the food industry, pomegranate juice is now increasingly used as dye in cosmetic and other products such as shampoos and high-value carpets (Al-Maiman and Ahmad, 2002; Al-Said et al., 2009). Similary, the fruit peel, stem, root bark and leaves are a good source of secondary products such as tannins, dyes and alkaloids (Mirdehghan and Rahemi, 2007). The edible portion (arils) of pomegranates is about 55 to 60% of the total fruit weight and contains 80% juice and 20% seeds. The fresh juice contains 85% water and 15% sugars, pectins, ascorbic acid, polyphenolic flavonoids, anthocyanins and amino acids (Roy and Waskar, 1997; Kader, 2006). Pomegranate juice contains fructose and glucose in similar quantities; calcium is 50% of its ash content; while the principal amino acids are glutamic and aspartic acids (El-Nemer et al., 1990; Cemeroglu et al., 1992; Aviram et al., 2000). The juice is also rich in sugars, organic acids, vitamins, polysaccharides and essential minerals (Al-Maiman and Ahmad, 2002). The levels of these compounds vary with pomegranate variety, maturity, and enviromental and cultivation conditions. Al-Maiman and Ahmad (2002) showed that composition of minerals varied markedly among the three ripening stages. The amounts of potassium, calcium and sodium were highest in both juice and seeds followed by magnesium, phosphorous, zinc, iron and copper. They demonstrated that pomegranate fruit can be a good source of nutrients and variation could originate from the pomegranate cultivar, and agro-climatic conditions. Mirdehghan and Rahemi (2006) studied physical changes of fruit during fruit growth and development and showed that the main changes in fruit size occurred within 60 days after full bloom. Potentially active phytochemicals found in pomegranates include sterol and terpenoids in seeds, bark and leaves; alkoloids in the bark and leaves; fatty acids and triglycerids in seed oil; simple gallyol derivatives in the leaves; organic acids in the juice; flavonols in the rind, fruit, bark, and leaves; anthocyanins and anthocyanidins in the juice and rind; and catechin and procyanidins in rind and juice (Seeram et al., 2006; Holland et al., 2009). Products from all parts of pomegranate tree, including the fruit, bark, flowers, roots, and leaves have been used for medical treatments of a wide list of diseases and ailments (Holland et al., 2009). In folk medicine, pomegranate preparations, especially of dried pericarp and the roots, barks of the tree and roots and the juice of the fruit, are used in the treatment of colic, colitis and dysentery (Schubert et al., 1999; Langley, 2000). It

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has been suggested that pomegranate juice has anticancer activities (Jeune Louise et al., 2005) and shown that consumption of pomegranate juice decreases retention of harmful low-density lipoprotein (LDL) cholesterol (Aviram et al., 2000). Pomegranate fruit is a rich source of two types of polyphenolic compounds: anthocyanins (such as delphinidin, cyanidin, and pelargonidin) which give the fruit and juice its red color; and hydrolysable tannins (such as punicalin, pedunculagin, punicalagin, gallagic and ellagic acid esters of glucose), which account for 92% of the antioxidant activity of the whole fruit (Gil et al., 2000). The soluble polyphenol content in pomegranate juice varies between 0.2 and 1.0%. It has been shown that the antioxidant activity of pomegranate juice is higher than that of red wine and green tea (Gil et al., 2000). Pomegranate juice is an important source of phenolic compounds, with anthocyanins being one of the most important, especially the 3-glucosides and 3,5-diglucosides of delphinidin, cyanidin, and pelargonidin (Du et al., 1975). These components along with gallagyl-type tannins, ellagic acid derivatives, and other hydrolysable tannins contribute to the antioxidant activity of pomegranate juice (Gil et al., 2000; Miguel et al., 2004). It has also been shown that pomegranate juice consumption by patients in Israel, monitored over a period of three years, reduced hardening and thickening of the arteries, blood pressure and LDL oxidation, which all increase the risk of heart disease (Aviram et al., 2004).

14.2

Fruit development and postharvest physiology

14.2.1 Fruit growth, development and maturation Pomegranate fruits follow a single sigmoid growth curve during their development (Shulman et al., 1984). In pomegranate fruit the outer layer of the testa or integuments develops into the edible aril. Active cell division in fruit flesh is usually limited to an initial period of a few weeks after anthesis (Bollard, 1970). The developmental period of pomegranate arils extends up to 80 days from fruit set, which is associated with a continuous increase in concentration of total soluble solids (TSS), total sugars, reducing sugars and anthocyanin pigments. This is accompanied by a significant reduction in total phenolics, ascorbic acid and titrable acidity up to 80 days, followed by a steady-state. For example, the lowest TSS (13%), total sugars (12.6%) and reducing sugars (12.2%) contents were recorded in 40 day-old fruit. A significant increase in all of the above three constituents was recorded after the 80th day of fruit development and the highest TSS (15.3%), total sugars (16.6%) and reducing sugars (15.7%) contents were recorded in 140 day-old fruit. However, the highest titrable acidity (0.56 as % citric acid) was recorded in 60 day-old pomegranate fruit arils. This was followed by a continuous, but significant decrease in titrable acidity to the lowest concentration of 0.33 (as % citric acid), which was recorded in 140 day-old fruit. Arils show a similar rapid and significant depletion (by 54.5%) in total phenolics during the initial stage of fruit development from 20 to 40 days. Later the decrease is more gradual but still significant up to 140 days. The highest

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phenolic content (506 mg.100 g−1 arils) was recorded in 20 day-old fruit. There was a nearly 73.9% reduction in total phenolics from 20 to 140 days of fruit development (Kulkarni and Aradhya, 2005). In contrast, the wild genotype has lower pH than that of standard cultivars. Similarly, the titratable acidity of fruit juice was higher in the wild genotype, resulting in a sugar:acid ratio (TSS:TA) that was nearly eight times less than the other standard cultivars (Al-Said et al., 2009). Pomegranate fruit are harvested between 130 to 180 days after fruit set depending on the variety. There is no consistent correlation between the outer skin color of the rind and the color of the arils. The external outer skin color does not indicate the extent of ripening of the fruit or its readiness for harvest and consumption because it can attain its final color long before the arils are fully ripened. The most pronounced difference in ripening time among cultivars is not derived from the differences in flowering dates but rather from the time required to ripening from anthesis (Holland et al., 2009). Titratable acidity, ascorbic acid and juice percentage decreases and soluble solids (mainly sugars) content, total and individual sugars, TSS/acid ratio, pH, and red color intensity of the juice increase with pomegranate fruit maturation and ripening (Lee et al., 1974; Elyatem and Kader, 1984; Kader et al., 1984; Al-Maiman and Ahmad, 2002). Due to the extended bloom, fruit can mature at different stages. For example, California-grown ‘Wonderful’ pomegranates picked in mid-October had an average soluble solids content of 18.1% and a titratable acidity of 1.58%, whereas those harvested in late September averaged 17% and 1.8%, respectively (Kader et al., 1984). Differences in soluble solids, juice color, percent edible portion, and percentage of extractable juice were small among fruits of various sizes. Large fruits (more than 250 grams) were generally lower in titratable acidity than smaller fruits (Kader et al., 1984). On the other hand, the type of organic acid is cultivar dependant (Melgarejo et al., 2000). For example, citric acid is the main organic acid in the ‘Mollar’ cultivar, followed by tartaric acid, whereas the ‘Assaria’ cultivar has almost equal levels of citric, oxalic and tartaric acids (Miguel et al., 2006). In contrast, a great variation in the organic acid composition among the Turkish pomegranate cultivars has been reported (Poyrazoglu et al., 2002). Similarly, considerable variation is found in some of the chemical and antioxidant properties of pomegranate cultivars widely grown in the Mediterranean region of Turkey (Özgen et al., 2008). 14.2.2 Respiration, ethylene production and ripening Pomegranate fruits have a relatively low respiration rate that declines with time during storage after harvest (Elyatem and Kader, 1984; Kader et al., 1984). The ranges of respiration (carbon dioxide production) rates for California-grown ‘Wonderful’ pomegranates were 2–4, 4–8, and 8–18 ml/kg.hr at 5 °C, 10 °C, and 20 °C, respectively, while ethylene production rates remained below 0.2 microliter per kilogram per hour. Pomegranates produce very low amounts of

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ethylene at <0.1 μL kg−1 h−1 at 10 °C and <0.2 μL kg−1 h−1 from 10 to 20 °C (Elyatem and Kader, 1984). Fruit are not particularly sensitive to ethylene exposure, although ethylene at ≥1 μL L−1 stimulates respiration and autocatalytic ethylene production. Ethylene treatment of ‘Wonderful’ pomegranates caused a rapid but transient rise in CO2, but no change in SSC, TA, or fruit and juice color (Ben-Arie et al., 1984). Based on the pattern of carbon dioxide and ethylene production, pomegranate is classified as a non-climacteric fruit, one that exhibits no dramatic changes in postharvest physiology or composition (Elyatem and Kader, 1984; Kader et al., 1984).

14.3

Maturity and quality components and indices

The acceptability of a pomegranate to the consumer and processor depends on a combination of several quality attributes that are related to physico-chemical and mechanical properties (Al-Said et al., 2009). These properties include:

• • • • • • •

freedom from internal and external decay freedom from preharvest defects (such as cracking/splitting and sunburn, which cause dark-brown to black discoloration of the affected skin area) freedom from defects that may occur during harvesting and handling (such as surface abrasions, cuts, and impact bruising) skin color and smoothness aril color intensity and uniformity fruit size, depending on the intended use of the pomegranates sugar content, acidity and flavour.

The quality of fresh horticultural products cannot be improved by postharvest technologies. It can only be maintained, which means horticultural products must be of high quality at harvest. To have a high quality product at harvest, it is essential to ensure that preharvest conditions are optimized. In addition, correct fruit maturity at harvest greatly influences subsequent storage life and eating quality. Pomegranates do not ripen off the tree and should be picked when fully ripe to ensure their best flavor (Kader et al., 1984). The pomegranate fruit reaches full maturity (ripeness) within 4.5 to 6 months after full bloom, depending on climactic conditions (LaRue, 1980; Ben-Arie et al., 1984; Kader, 2006). The fruits should be harvested before they become overripe and crack (split) open, especially under rainy conditions. Maturity indices are variety-dependent and include external skin color (changes from yellow to red) and juice color, acidity, and soluble solids content and TSS/acid ratio (Ben-Arie et al., 1984; Elyatem and Kader, 1984; Kader et al., 1984; Crisosto et al., 2000; Al-Maiman and Ahmad, 2002). A high quality pomegranate should have an attractive skin, small seeds in the aril and should be free from sunburn, growth cracks, cuts, bruises, and decay (Abbott, 1999). Skin color and smoothness are other quality indices. Sour and sour-sweet pomegranates have a reddish skin, in contrast to sweet pomegranates

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which have a yellowish-green skin. Skin thickness varies from 1.5 to 4.24 mm (Küpper et al., 1995). The acidic taste and related flavor are some of the important attributes of pomegranate juice, which contribute to its strong appeal in the food and beverage industry. In this regard, the wild genotypes represent a diversity in local pomegranate genetic resources with very low sugar:acid ratio that is suited for formulation of a wide range of food and beverage products (Mars and Marrakchi, 1999; Al-Said et al., 2009). Similary, fruit flavor and overall quality depends largely on the sugar and acid content of the juice. Pomegranates also have a low ascorbate content compared to many other fruits, and ranges from 0.49 to 30 mg per 100 g juice, depending on cultivar (Hussein and Hussein, 1972). The juice content of pomegranates is 45 to 65% of the whole fruit or 76 to 85% of the aril. The level of titratable acidity varies from one location to another and from one year to the next but generally remains stable at the time when the TSS content reaches 15%. After harvest, there is no further change in either TSS content or titratable acidity at 20 °C, but redness of the juice continues to increase up to the harvest time. In general, varieties that have whitish or pinkish arils (such as the ‘Mollar’ grown in Spain) are usually sweeter than those with purplish or dark crimson arils because the latter varieties contain higher concentrations of organic acids (Gil et al., 1996a). According to Küpper et al. (1995) titratable acidity (TA) of pomegranates varies between 0.13 and 4.98% at harvest. There are three types of pomegranates based on their acidity: < 1% TA are sweet cultivars, 1 to 2% are sweet-sour cultivars and > 2% are sour cultivars (Pekmezci and Erkan, 2004). The pH varies during the development and ripening of the fruit between 3.60 and 4.15, while minimum soluble solids vary from 15% to 17%. The minimum maturity indices for California grown ‘Wonderful’ pomegranates are red juice color equal to or darker than Munsel color chart 5R-5/12 and titratable acidity below 1.85% (Elyatem and Kader, 1984; Kader et al., 1984; Crisosto et al., 2000).

14.4

Preharvest factors affecting fruit quality

To have a high quality product at harvest, it is essential to ensure that preharvest conditions and cultural practices are optimized. Nutrition during the growth of the fruit before harvest is one of the important factors that affect quality. However, little information is available on preharvest factors affecting fruit quality in pomegranates. Bose et al. (1988) reported that increasing the levels of nitrogen in pomegranate fruit during the growth increased juice and rind percentage of fruits but decreased TSS and TSS/TA ratio. Similary, urea application at full bloom and one month after full bloom at concentrations of 1% and 2% significantly increased aril size, fruit length and diameter in ‘Malase-Yazdi’ cultivar. Calcium chloride at concentrations of 2% and 4% significantly increased average fruit weight and ascorbic acid (AA) content. Both urea and calcium chloride increased TSS at all of the used concentrations (Ramezanian et al., 2009). In another experiment, the

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effect of three preharvest chemicals: (1) CaCl2, (2) Ca(NO3)2 and (3) KH2PO4, on the quality of pomegranate fruits was investigated. These chemicals, at 1% and 2%, were sprayed onto pomegranate cv. ‘G-137’ trees at 90 days after full anthesis. Aril (68.93%) and juice (54.57%) percentage were markedly enhanced by 2% KH2PO4, while seed hardness was not affected by any treatment. TSS (16.36%) and ascorbic acid content (5.88 mg.100 g−1) were highest in the 2% Ca(NO3)2 treatment, while the highest total sugars (15.21%) and reducing sugars (11.94%) were recorded in the 2% KH2PO4 treatment (Heshi et al., 2001). Preharvest factors can also affect fruit cracking in pomegranate which is a major problem for marketing intact fruit. Onur (1988) reported that irregular irrigation practices or excessive rain during the maturation could be a reason for fruit cracking. Kumar (1990) also reported that fruit cracking may result from the fluctuation of soil moisture and relative humidity, e.g. rain or heavy irrigation following a dry spell. Increasing levels of nitrogen has been suggested as an effective treatment for fruit cracking as is the use of gibberellic acid (GA3) (Sepahi, 1986; Holland et al., 2009).

14.5

Postharvest handling factors affecting quality

14.5.1 Temperature management Temperature is the environmental factor that most influences the deterioration rate in pomegranate because of its effects on the metabolic activity of the fruit and microbial growth. The Q10 values for respiration of pomegranates are 3.4 between 0 °C and 10 °C, 3.0 between 10 °C and 20 °C, and 2.3 between 20 °C and 30 °C (Kader et al., 1984). Pomegranates should be promptly cooled to 7 °C as soon as possible after harvest and should be kept at the recommended temperature and humidity during transportation and storage to reach their maximum postharvestlife of two to four months, depending on the cultivar (Kader, 2006). Rapid cooling using forced air is one of the simplest ways to extend postharvestlife of pomegranates. The temperature has to be around 5 °C to prevent development of physiological disorders during storage (Kader et al., 1984; Artés et al., 1998a, 2000a). The minimal safe temperature to store sweet pomegranates is 7 °C (Kader et al., 1984). This temperature, however, does not prevent fungal development. Previous studies have demonstrated that storage of ‘Mollar’ pomegranate at 5 °C and 90–96% RH up to eight weeks, leads to an acceptable decrease in fungal decay losses (Artés et al., 1996). Storage of pomegranates below 5 °C results in chilling injury (CI), the severity of which increases with time and with lowered temperature. CI symptoms, which became more visible after transfer to 20 °C for three days, include brown discoloration of the white locular septa separating the arils (see Plate XXVI in the colour section between pages 238 and 239). Other symptoms of CI injury includes browning of the rind, pitting, scald, an increased sensitivity to fungal development and decay, and internal discoloration and browning of the seeds (Artés et al., 1998a, 2000a; Defilippi et al., 2006). Pomegranate can be stored at 5 °C for up to

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two months, but longer storage should be at 7 °C to avoid CI (Kader et al., 1984). Spanish ‘sweet’ pomegranates can suffer CI if they are stored for more than two months at temperatures below 5 °C. However, some cultivars such as ‘Wonderful’, can be stored without problems for two months at 5 °C. Heat treatments have been used to extend storability of pomegranates. Heat treatments of pomegranates at 45 °C for four minutes have a favorable effect on antioxidant activity. Mirdehghan et al. (2007) reported that arils from heat-treated pomegranates exhibited higher total antioxidant activity than controls, which was correlated primarily with the high levels of total phenolics and to lesser extent to ascorbic acid and anthocyanin content. Additionally, the levels of sugars (glucose and fructose) and organic acids (malic, citric, and oxalic acids) also remained at higher concentrations in arils from treated fruits. Intermittent warming treatments have proved useful in preventing CI symptoms while maintaining pomegranate quality in such areas as reducing electrolyte and K leakage, retention of anthocyanin and titratable acidity, and reduction of decay (Artés et al., 1998a, 2000a; Nanda et al., 2001; Mirdehgan and Rahemi, 2005). ‘Mollar de Elche’ pomegranates were stored at 0 °C and 5 °C and 95% relative humidity (RH) for 80 days. Intermittent warming treatments at 20 °C were applied in cycles, one day every six days storage, followed by a period of seven days at 15 °C and 70% RH. The warming treatments led to very good results in keeping the quality of pomegranates. Another technological treatment used with success in pomegranate is preconditioning at moderate temperature (30–40 °C) and high RH (90–95%) for a short period of time (1–4 days), a technique also known as curing, that is applied before the conventional refrigerated storage. In one study, a pre-treatment at 35 °C and 90–95% RH applied for three days previous to refrigerated storage during 80 days at 5 or 2 °C and 90–95% RH, reduced considerably pitting and husk scald compared to control pomegranates without the preconditioning treatment. The effects observed were more marked when the conservation was carried out at 2 °C than at 5 °C, particularly during the additional period of one week at 15–20 °C and 70–75% RH, applied to simulate the retail sale period (Artés et al., 1998b). Several other attempts have been made to alleviate the severity of CI in pomegranate, with satisfactory results such as with the use of methyl jasmonate (Zolfagharinasab and Hadian, 2007) and polyamines (Mirdehghan et al., 2007). Sayyari et al. (2009) reported that salicylic acid (SA) treatment at different concentrations (0.7, 1.4 or 2.0 mM), especially at 2 mM, were highly effective in reducing CI at 2 °C for three months. However, none of these chemicals are approved for commercial use on pomegranates. 14.5.2 Physical damage Pomegranates are not as hardy fruits as they may appear. They are as susceptible as apples to physical damage by abrasion, impact, compression and vibration. Careful handling to minimize physical damage is essential to keeping the quality of pomegranates. Similary, arils are highly susceptible to mechanical damage.

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Mechanical damage is caused by the use of inappropriate methods for extracting, packaging and transporting arils. This can lead to tissue wounds, abrasion, breakage, and squashing of the arils. Hess-Pierce and Kader (1997) reported that mechanical damage reduces the commercial value of the arils and it may increase their susceptibility to decay and the growth of microorganisms. They also reported that damaged arils were more susceptible to heavy mold infestations even under carbon dioxide-enriched controlled atmospheres. During extraction, air pressure and nozzle diameter significantly influence the percentage of damaged pomegranate arils. The data showed that removing the arils at an air pressure of 800 kPa caused a considerable portion of extracted arils to be mechanically damaged. However, at air pressures of 500 and 700 kPa, the percentages of damaged arils were not appreciable. With a 2.5 mm diameter nozzle a high percentage of the arils were damaged and the percentage of damaged arils increased with an increase in air pressure (Khazaei et al., 2008). 14.5.3 Water loss Pomegranates are very susceptible to water loss resulting in shriveling of the rind. Two of the main limiting factors to prolonged storage of pomegranates are weight loss and shrinkage (Elyatem and Kader, 1984; Ben-Arie and Or, 1986; Koksal, 1989). According to Elyatem and Kader (1984), weight loss of ‘Wonderful’ pomegranates during cold storage is largely due to water lost through natural porosity of the skin. Shriveling symptoms on fruit are noticeable only when weight loss exceeds 5% or more of the initial weight. The higher the temperature and the lower the relative humidty (RH), the greater the water loss. In general, pomegranates that are marketed without waxing should be kept at 90% to 95% RH to prevent water loss. However, use of plastic liners and waxing can reduce water loss, especially under conditions of lower RH. Modified atmosphere packaging (MAP) either using plastic bags or shrink film wrapping is beneficial in reducing water loss and shrinkage, and can facilitate maintenance of fruit quality for three months or more after harvest (Artes et al., 2000b; Nanda et al., 2001; Porat et al., 2008). 14.5.4 Atmosphere Exposure of pomegranates to 1, 10, or 100 ppm ethylene in air for up to 13 days at 20 °C stimulated their respiration rate in proportion to ethylene concentration (Kader et al., 1984). Subjecting pomegranates to 100 ppm ethylene in air for two days temporarily increased their respiration and ethylene production rates, which then declined to near the levels of control fruits after three days in air. This response occurred again when the fruits were exposed to a second two-day ethylene treatment after seven days in storage (Kader et al., 1984). These responses are typical of nonclimacteric fruits. None of the ethylene treatments had a significant effect on skin color, juice color, soluble solids, pH, or titratable acidity of the pomegranates. These results indicate that pomegranates do not ripen once

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removed from the tree and should be picked when fully ripe to ensure the best eating quality for the consumer. There is therefore no value in treating harvested pomegranates with ethylene (Kader et al., 1984). Modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage have been tested with satisfactory results in maintaining pomegranate quality during storage (Artes et al., 2000b; Nanda et al., 2001; Hess-Pierce and Kader, 2003; Porat et al., 2008). These technologies are discussed in more detail in sections 14.8.3 and 14.8.4.

14.6

Physiological disorders

14.6.1 Chilling injury As has been noted, pomegranate fruits are very susceptible to chilling injury (CI) if they are stored longer than one month at temperatures between their freezing point (−3 °C) and 5 °C or longer than two months at 5 °C (Elyatem and Kader, 1984; Kader et al., 1984). So, the minimum safe temperature for postharvest handling of pomegranates ranges between 5 °C and 8 °C, depending on variety and production area (Elyatem and Kader, 1984; Kader et al., 1984; Crisosto et al., 2000; Pekmezci and Erkan, 2004). Upon transfer to 20 °C, respiration and ethylene production rates increase and other chilling injury symptoms (brown discoloration of the white locular septa and pale color of the arils) appear. Their severity increases with lower temperatures (see Plate XXVI in the colour section) and longer periods of chilled storage. Depending on the storage duration and temperature, these symptoms affect the arils, producing brown discoloration of the white segments separating the arils and pale color of the arils themselves (Schotsmans et al., 2009). 14.6.2 Other physiological disorders Husk scald (see Plate XXVII in the colour section) is another important factor limiting the commercial storage potential of the pomegranates, and its symptoms appear as superficial skin browning initiating from the stem end of the fruit without affecting the internal tissues and spreading toward the blossom end as the severity increases (Ben Arie and Or, 1986; Defilippi et al., 2006). The similarities between pomegranate scald and apple scald, in terms of symptomatology and occurrence, suggest that the two disorders may be similar in the biochemical causes and mechanism of control. However, Defilippi et al. (2006) found that neither diphenylamine (DPA) nor 1-methylcyclopropene (1-MCP) treatments reduced incidence or severity of scald on ‘Wonderful’ pomegranates. Husk scald increases the susceptibility of the fruit to decay (Kader, 2006). Scald incidence and severity were greater on pomegranates harvested during late season than on those harvested during mid-season, indicating that this disorder may be associated with senescence. All pomegranates from both harvests that were kept in air exhibited some scald after 4–6 months at 7 °C.

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Controlled atmosphere (CA) storage significantly reduced scald incidence and severity on pomegranates from both harvest dates for up to six months at 7 °C (Defilippi et al., 2006). Artes et al. (1996) recomended 5 kPa O2 and 5 kPa CO2 as the optimal CA conditions for ‘Mollar’ pomegranate at 5 °C in controlling husk scald. The best CA combination controlling scald was 5 kPa O2 +15 kPa CO2 (see Plate XXVII in the colour section), which resulted in a lower accumulation of fermentative metabolites than the other CA treatments. CA storage (5 kPa O2 + 15 kPa CO2) also decreased or prevented changes in carotenoid, acyl lipid, and phenylpropenoid metabolism that were associated with scald development in stem-end peel tissue of air-stored fruit (Defilippi et al., 2006). Fruit cracking may affect pomegranate fruits and sometimes cause significant commercial losses, but fruit cracking actually may be regarded as the last stage of normal pomegranate fruit development process where the fruit is spreading its arils (Fig. 14.3). Cracking susceptibility among the cultivars vary in different parts of the world and can be reduced by regular irrigation (Prasad et al., 2003), however, most known cultivars eventually crack if they overripen and are not harvested at commercial maturity. It is well known that rainfall on mature

Fig. 14.3

Fruit cracking damage in pomegranate fruit.

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Sunburn damage in pomegranate fruit.

pomegranates following the end of the dry season can induce rapid fruit cracking. Spraying with gibberelic acid (GA3) at 150 ppm or with benzyladenine (BA) at 40 ppm can significantly reduce cracking (Yilmaz and Ozguven, 2006), while application of boron may also reduce fruit cracking (Singh et al., 2003). However, these chemicals are not approved for commercial use. Sunburn is another physiological disorder which may negatively affect commercialization of pomegranate (Fig. 14.4). The cause of sunburn is the combined action of high solar radiation, low humidity and high temperatures. Yazici and Kaynak (2006) reported that fruit surface temperatures that cause sunburn vary between 41 °C and 47.5 °C and kaolin treatment proved to be the best method to reduce sunburn injury in ‘Hicaznar’ cultivar. Holland et al. (2009) reported that in Israel, late cultivars such as ‘Wonderful’ are much more susceptible to sunburn than early cultivars such as ‘Akko’ and ‘Shani-Yonay’.

14.7

Pathological disorders

Gray mold, caused by Botrytis cinerea Pers.: Fr., is the most economically important postharvest disease of pomegranates (Tedford et al., 2005). Gray mold

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usually starts at the calyx. As it progresses, the skin becomes light-brown, tough and leathery. Other fungi-causing fruit rot worldwide include Aspergillus niger, Penicillium spp., Alternaria spp., Nematospora spp., Coniella granati, or Pestalotiopsis versicolor (Wilson and Ogawa, 1979; Snowdon, 1990; Palou et al., 2007). The application of fludioxonil has considerably reduced postharvest decay caused by B. cinerea and is at present a key factor in extending the postharvestlife of pomegranates (Palou et al., 2007; D’Aquino et al., 2009, 2010). Heart rot is another disorder that may be caused by Aspergillus spp. and/or Alternaria spp. Affected fruit show slightly abnormal skin color and a mass of blackened arils. The disease develops while fruit are on the tree (Salunkhe and Desai, 1984). The fungi can grow within the fruit without external symptoms except for slightly abnormal skin color. If the mass of blackened arils reaches the rind, it will cause softening of the affected area; these pomegranates can be detected and removed by the sorters in the packinghouse (LaRue, 1980). Minimizing physical damage during harvesting and postharvest handling plus maintaining optimal temperature and relative humidity throughout postharvest handling of pomegranates are very important decay control strategies. Carbon dioxide enriched atmospheres are fungistatic and inhibit growth of Botrytis cinerea. Use of Fludioxonil (Scholar) as a postharvest fungicide is effective in controlling this fungi and is approved by the United States Environmental Protection Agency with a maximum residue limit of 5 ppm. Natural incidence of decay of pomegranates has been shown to be significantly reduced to 0–8% after two or five months of storage at 10 °C in fruit treated with fludioxonil (FLU) (Adaskaveg and Förster, 2003). FLU, being a synthetic analogue of pyrrolnitrin (Rosslenbroich and Stuebler, 2000), belonging to the class of phenylpyrroles, and has recently registered for controling postharvest decay of pomegranates and other horticultural crops in the USA (Tedford et al., 2005). Pomegranates have benefited from CA (controlled atmosphere) or MA (modified atmosphere) treatments especially if combined with another effective treatment for decay control. ‘Mollar de Elche’ sweet pomegrantes stored at 2 or 5 °C for 12 weeks in unperforated polypropylene film of 25 μm thickness had less incidence of decay mainly due to Penicillium spp. Higher decay levels were found in pomegranate stored at 5 °C than those at 2 °C (Artes et al., 2000b). The combination of CA storage (5 kPa O2+15 kPa CO2) with antifungal treatment (potassium sorbate) reduced Botrytis decay during storage (Palou et al., 2007).

14.8

Postharvest handling practices

14.8.1 Harvest operations The stem of pomegranate fruit is strong and thick and so the fruit can be best detached by clipping. Pickers harvest pomegranates with clippers or sometimes by twisting the fruit stem off the tree. If possible, at least two selections for harvesting based on maturity should be made for clipping. Only fruit that is proportionately colored and sized should be removed at the first selection.

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Harvested fruits are placed in picking bags for transfer to harvest bins that will be transported to the packinghouse. Then the pomegranates are sorted to eliminate those with severe defects (such as scuffing, cuts, bruises, splitting, and decay) and the remaining fruits are separated according to the magnitude of the physical defects. Pomegranates with moderate external defects are used for processing into juice and those with slight or no external defects are marketed fresh. 14.8.2 Packinghouse practices Pomegranates are washed, air dried to remove surface moisture, fungicide treated, waxed, divided into several size categories, and packed in shipping containers. Various ways to immobilize the fruits within the shipping containers may be used to reduce incidence and severity of scuffing and impact bruising during handling. Perforated plastic box liners may be used to reduce water loss during postharvest handling of pomegranates. Packed fruits are cooled by forced-air cooling to 7 °C and kept at that temperature and 90–95% RH during storage and transport to retail distribution centers. The materials used inside the package must be new, clean, and of a quality such as to avoid causing any external or internal damage to the pomegranates. The use of labels or stamps bearing trade specifications is allowed, provided the printing or labeling has been done with non-toxic ink or glue. Pomegranates shall be packed in each container in compliance with the Recommended International Code of Practice for Packaging and Transport of Fresh Fruits and Vegetables (CAC/RCP 44-1995). 14.8.3 Control of ripening and senescence Modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage have been tested with satisfactory results in maintaining pomegranate quality during storage (Artes et al., 2000b; Nanda et al., 2001; Hess-Pierce and Kader, 2003; Porat et al., 2008). The tolerance limit for CO2 concentration is different for intact pomegranate and arils. For example, Hess-Pierce and Kader (2003) reported that, in intact fruit, carbon-dioxide-enriched atmospheres up to 10 kPa resulted in higher concentrations of fermentative metabolites, including acetaldedyde and ethanol, especially after four and five months at 5 °C, 7.5 °C or 10 °C. Accumulation of these volatiles was greater at 7.5 °C and 10 °C than at 5 °C. However, the highest concentrations were below the threshold values for off-flavors detection in fruits like pomegranates containing more than 10% total sugars (Ke et al., 1991). On the other hand, Holcroft et al. (1998) found that arils stored in air enriched with 10 kPa CO2 had a lower anthocyanin concentration than air-stored arils, and, in atmospheres enriched with 20 kPa CO2 had even lower levels, possibly from suppressed anthocyanin biosynthesis. In general, the tolerance atmosphere limit for pomegranate is 5 kPa oxygen + 15 kPa carbon dioxide and at 7.5 °C fruit can be stored for up to five months. A combination of 5 kPa O2 and 15 kPa CO2, has been shown to extend pomegranate postharvest life for up to five months at 7 °C (Hess-Pierce and Kader, 2003).

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As has been noted, one of the initial reports on CA storage of pomegranate published by Ben Arie and Or (1986) indicated that storage of ‘Wonderful’ pomegranate in 2 kPa O2 at 2 °C for six weeks prevented the development of husk scald. Artes et al. (1996) recomended 5 kPa O2 and 5 kPa CO2 as the optimal CA conditions for ‘Mollar’ pomegranate at 5 °C in controling husk scald. Küpper et al. (1995) found that CA storage of ‘Hicaz’ pomegranate at 6 °C containing 6 kPa CO2 and 3 kPa O2 reduced decay development and weight loss. Holcroft et al. (1998) showed that 10 or 20 kPa CO2 suppressed the anthocyanin biosynthesis in ‘Wonderful’ pomegranate. Hess-Pierce and Kader (2003) found that 5 kPa O2 and 15 kPa CO2 is the best atmosphrere for ‘Wonderful’ pomegranate and at 7 °C this cultivar can be stored for up to six months. Moreover, a combination of CA storage (5 kPa O2+15 kPa CO2) with antifungal treatment (potassium sorbate) reduced Botrytis decay during storage (Palou et al., 2007). MAP (unperforated polypropylene film of 25 μm thickness) at 5 °C for 12 weeks is very effective in controlling weight loss and CI in ‘Mollar de Elche’ pomegranates (Artes et al., 2000b). Nanda et al. (2001) found that individually shrink film wrapping of ‘Ganesh’ pomegranate significantly reduced weight and firmness losses. MAP has been suggested to extend the shelf life of minimally processed arils (Sepulveda et al., 2000; Lopez-Rubira et al., 2005). Sepulveda et al. (2000) reported that minimally processed ‘Wonderful’ pomegranate were able to be stored for 14 days at 4 °C ± 0.5 with the use of semipermeable film. Similary, the shelf life of the pomegranate arils commercially produced in Turkey is suggested as 10 days using 100% nitrogen in PET packages. However, drip loss was a big problem with the product (Ayhan and Esturk, 2009). Gil et al. (1996b) reported that pomegranate arils packaged in air and enriched oxygen had higher total anthocyanin contents than the samples packaged in nitrogen or low oxygen atmosphere during storage. No significant change in total anthocyanin content in arils of ‘Mollar’ pomegranates during MAP storage at 1 °C up to seven days. Lopez-Rubira et al. (2005) also reported that there was no significant change in total anthocyanin content of early harvested pomegranates after 13 days of storage. Similary, the shelf life of pomegranate arils of ‘Hicaznar’ pomegranates was suggested as 18 days under air, nitrogen, and enriched oxygen atmospheres, and 15 days under low oxygen atmosphere with the package type of PP (polypropylene) tray with BOPP (biaxially-oriented polypropylene) film at 5 °C storage (Ayhan and Esturk, 2009). 14.8.4 Recommended storage and shipping conditions A suggested gas composition recommended for the storage of pomegranate at 5 °C is 3 to 5 kPaO2 + 5 to 10 kPa CO2 (Kader, 1997). Artés et al. (1996) reported that a gas composition of 5 kPa O2 + 0 to 5 kPa CO2 during storage of ‘Mollar’ pomegranates at 5 °C was effective for reducing CI, decay, and weight loss. MAP of fruit can bring about the lowering of respiration activity, delay in ripening and softening, and a reduced incidence of physiological disorders and decay-causing

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pathogens (Artes et al., 2000b). The recommended MA storage conditions for ‘Hicaznar’ are 6 °C with 90% RH (Pekmezci and Erkan, 2004). Losses due to physiological disorders of fruit are higher at 5 °C than at 2 °C, mainly because of a higher husk-scald development, possibly because of an increase in polyphenoloxidase activity. After the refrigerated-storage period, no losses due to pitting and husk scald in pomegranates packaged in MA bags were found, but after the shelf life period, an increase in pitting and husk scald in all treatments was observed. MAP fruits suffered the lowest increase in physiological disorders. Only unpackaged control at 5 °C fruits showed a moderate (commercially objectionable) level of pitting and husk-scald severity index (Artes et al., 2000b).

14.9

Processing

14.9.1 Fresh-cut processing The major obstacles to realizing the fruit’s full potential are the difficulties involving extracting the arils (Sarig et al., 2001; Khazaei et al., 2008; Blasco et al., 2009). Both manual and mechanical extraction techniques are currently used commercially to a limited extent to present the consumer with fresh pomegranate arils. In recent years, minimally processed ‘ready-to-eat’ pomegranate arils have become popular due to their convenience, high value, unique sensory characteristics, and health benefits (Khazaei et al., 2008; Blasco, 2009; Ayhan and Esturk, 2009). Previously requiring an expensive and labor-intensive operation, pomegranate arils can now be extracted by fully automated systems with minimal seed damage, increased output, and labor cost savings. Industrial processing of pomegranate provides opportunities to create a new and innovative market for fresh arils, frozen arils, freeze-dried arils, dried arils, juices and wines; and health and pharmaceutical products. Hess-Pierce and Kader (1997) investigated the effects of pre-extraction storage duration and post-extraction packaging and handling conditions on deterioration rate of pomegranate arils as a value-added, ready-to-use product. Pomegranate arils have relatively low rates of respiration (1.5–3 and 3–6 ml carbon dioxide per kilogram per hour at 5 and 7 °C, respectively) and ethylene production (5–15 and 15–30 nl ethylene per kilogram per hour at 5 and 7 °C, respectively). It is possible to produce arils that retain good sensory and microbial quality for up to 14 days shelf life at 5 °C from pomegranate fruits that are stored at 7 °C for up to three months in air or up to five months in a controlled atmosphere of 5% oxygen + 15% carbon dioxide + 85% nitrogen. Mechanical damage to the arils must be minimized during their extraction from the fruit, washing, drying to remove surface moisture, and packaging since damaged arils are more susceptible to decay-causing fungi. Carbon dioxideenriched atmospheres have a fungistatic effect and their optimal range for decay control without inducing off-flavors in the arils is 15–20 kPa added to either air or

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5 kPa oxygen. Although intact pomegranate fruits are chilling-sensitive, the arils are chilling-tolerant and should be kept at temperatures between 0 °C and 5 °C to maintain their quality and microbial safety. Pomegranate arils that are not damaged or microbally-contaminated can be kept at 0 °C for up to 21 days, at 2 °C for up to 18 days, or at 5 °C for up to 14 days in marketable condition. It should be noted that these data are for arils extracted from freshly-harvested pomegranates and that the longer the storage duration of intact pomegranates before extracting the arils, the shorter the post-extraction life of the arils. 14.9.2 Juice extraction The composition of pomegranate juice depends on cultivar type, environmental and postharvest factors, and storage and processing factors. Due to increasing demand for high-quality pomegranate juice, processing of pomegranates to extract juice by crushing the intact fruit or by extracting the juice from the arils increased during the past few years. The main disadvantage of the squeezing or crushing method is the production of juice with astringent taste if no additional treatments are applied to reduce astringency. The presence of tannins is the main problem when juices are extracted from whole fruits. This problem can be avoided by extracting the arils, then squeezing them to extract the juice. However, the antioxidant activity, which is related to phenolic content of the juice, is higher in the juice extracted by crushing (Gil et al., 2000). Pomegranate juice is often concentrated to about 70% TSS and stored frozen for subsequent thawing and dilution with water to about 17% TSS and marketed as pure pomegranate juice or mixed with other fruit juices, such as blueberry, cherry, lime, mango, or orange. There is a need for developing markers of authenticity for pomegranate juice to detect adultration, which is common since pomegranate juice is more expensive than most other fruit juices.

14.10

Conclusions

Pomegranates should be handled with as much care as apples during harvesting and postharvest handling to minimize mechanical damage. Proper management of approved preharvest and postharvest fungicides is critical to avoiding development of fungal resistance. Use of MAP and/or CA storage as supplements to providing the optimal ranges of temperature and relative humidity are effective in extending postharvest-life of pomegranates. Further research is needed to evaluate the efficacy of continuos exposure to 0.2–0.3 ppm ozone during storage on preventing spread of decay among pomegranates. Increasing mechanization of aril extraction with minimal damage and subsequent preparation steps of arils as a ready-to-eat, value-added product will increase marketability. Further development of nutraceuticals derived from the edible and nonedible portions of pomegranates will increase profitability of pomegranates.

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Pomegranate (Punica granatum L.)

14.11

307

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Plate XXV

Plate XXVI

(Chapter 13) Purple pitanga (Eugenia uniflora L.).

(Chapter 14) Chilling injury symptoms in pomegranate fruit (Kader et al., 1984).

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1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43 44 45X

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43 44 45X

Plate XXVII

(Chapter 14) Husks scald symptom on pomegranate fruit (Defilippi et al., 2006).

Plate XXVIII (Chapter 15) Rambutan fruit (cv. R9), showing peel with hair-like spinterns and internal edible flesh.

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15 Rambutan (Nephelium lappaceum L.) M. M. Wall, US Department of Agriculture, Agricultural Research Service (USDA-ARS), USA, D. Sivakumar, Tshwane University of Technology, South Africa and L. Korsten, University of Pretoria, South Africa

Abstract: Rambutans (Nephelium lappaceum) are exotic tropical fruit with a relatively short shelf life. Fresh rambutans are bright red or yellow at harvest, but the peel color and spinterns darken during storage. Postharvest diseases also limit the successful marketing and export of this specialty fruit. Pericarp browning can be delayed when the fruit are held at 8–12 °C and 95% relative humidity, depending on cultivar. The use of modified atmosphere packaging or enhanced CO2 atmospheres (9–12%) can also maintain the visual quality of rambutans. Integrated preharvest and postharvest practices that achieve disease control while reducing desiccation and browning are needed to extend rambutan shelf life beyond two weeks. Key words: Sapindaceae, rambutan, postharvest quality, spintern, shelf life.

15.1

Introduction

15.1.1 Origin, botany, morphology and structure Rambutan (Nephelium lappaceum L.) is a popular tropical fruit in the Sapindaceae family, and closely related to litchi, longan, and pulasan. The origin of rambutan is uncertain (possibly the Malay peninsula), but the species ranges from southern China (Yunnan and Hainan) through the Indo-Chinese region, Malaysia, Indonesia, and the Philippines (Tindall, 1994). The plant is also cultivated throughout the humid tropics of Asia (Sri Lanka to New Guinea) and in small numbers in the humid tropics of America, Africa, and Australia (Van Weizen and Verheij, 1991). The fruit are valued for their attractive skin color, exotic flavor and sweet juicy flesh. Rambutan fruit differ in color from pink, red, deep crimson, yellow, to yellow-orange pericarp covered with hairy spinterns that give a characteristic appearance to the fruit (Watson, 1988) (see Plate XXVIII in the colour section between pages 238 and 239). The fruit are oval or round, and contain a single seed surrounded by a papery integument and an edible, fleshy, translucent sarcotesta.

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The rambutan tree is a medium sized (15 to 25 m) evergreen with a dense, spreading habit that thrives from sea level to 500 meters in tropical (22–32 °C), humid conditions with evenly distributed rainfall ranging from 200–350 cm. Rambutans grow best in well-drained, deep, clay loam or sandy loam soils with 5.5 to 6.5 pH range. The pinnate compound leaf has two to four pairs of ovate leaflets that are slightly hairy on the midrib (Van Weizen and Verheij, 1991). White flowers with tints of yellow or green are borne on panicle-type inflorescences and can be male or hermaphroditic. Rambutans require cross pollination. Trees that are produced from seeds have about 50% male flowers and will not bear fruit, and 50% female flowers which are functional. The commercially cultivated clones produce a large number of hermaphroditic flowers and a lower amount of male flowers to provide sufficient pollen. 15.1.2 Worldwide importance and economic value Rambutan has been classified as an underutilized fruit crop, but has grown in commercial importance. Thailand is the largest global producer of rambutan and the crop also is grown for domestic and export markets in Malaysia, Indonesia, the Philippines, Australia, Sri Lanka, Central America, South Africa, and the United States (Hawaii and Puerto Rico). 15.1.3 Culinary uses, nutritional value and health benefits Rambutans are enjoyed as a fresh fruit, but can also be used in preserves, sorbets, juices or wines. The edible portion (100 g) contains 80 g water, 1 g protein, 0.4 g fat, 2.9 g glucose, 3.1 g fructose, 9.8 g sucrose, 70 g ascorbic acid, 2.7 g dietary fiber, 0.8 g niacin, 0.02 mg thiamine, 0.06 mg riboflavin, 140 mg potassium, 2 mg sodium, 10 mg magnesium, 0.1 mg iron, and 0.6 mg zinc (Wills et al., 1986). Rambutans grown in Hawaii have ascorbic acid contents ranging from 22 to 47 mg·100 g−1 edible fresh weight (FW). The ascorbic acid levels of cultivars ‘R162’ and ‘Silengkeng’ are 47.8 mg·100 g−1 and 39.1 mg·100 g−1 FW, respectively (Wall, 2006). The dietary reference intake (DRI) values for vitamin C are 100 mg for adult males and 75 mg for adult females (IOM, 2000). Therefore, consumption of about 10–12 rambutan fruit could provide the DRI for the average adult (Wall, 2006). Rambutans are also a good source of minerals. The fruit (100 g) contain 135 to 249 mg potassium, 0.16 to 0.20 mg copper, and 0.07 to 0.38 mg manganese, providing 20% of the DRI for Cu, 8–10% of the DRI for Mn, and 2–6% of the DRI for minerals K, P, Fe and Zn (Wall, 2006).

15.2

Fruit development and postharvest physiology

15.2.1 Fruit growth, development and maturation Rambutan trees are prolific producers of flowers, but the number of flowers that set fruit is low (Kosiyachinda and Salma, 1987). The blooming of all flowers in an

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inflorescence takes about 24 days (Tongumpai, 1980). Usually, one of the two carpels in a flower develops into a fruit, and the other is abortive but remains attached to the mature fruit. An ovary of two carpels can take 13 to 16 weeks to develop into mature fruit (Salma, 1983; Wanichkul and Kosiyachinda, 1982). At almost six weeks, the protuberances on the surface change into light green spinterns. During subsequent growth, the spherical fruit lengthen and the skin thickens and increases in weight (Wanichkul and Kosiyachinda, 1982). A major phase of growth occurs 50 to 80 days after anthesis. Fruit development follows a simple sigmoidal growth curve for ‘Binjai’ in Hawaii (Kawabata et al., 2007) and ‘Seechompoo’ in Thailand (Kosiyachinda and Salma, 1987). The fruit become fully mature 15 weeks after fruit set and change in color from green to yellowish green, yellow, or red. In ‘Malaysian Yellow’ the skin color changes from dark green to greenish yellow, followed by yellow at optimum maturity and orange-yellow in over mature fruit (Sivakumar et al., 1998). In ‘Seechompoo’ fruit, color changes of the skin and spinterns are initially observed 12 weeks after fruit set. The spinterns change from green to yellowish pink, and two weeks later, the skin color turns yellow to deep yellow (Wanichkul and Kosiyachinda, 1982). At 15 weeks the entire fruit turns reddish pink to red. In the Sri Lankan cultivar ‘Malwana Special Selection’ the weight of the edible aril is highest at color stage 6 (pericarp 25% orangish red and 75% dark red). However, in ‘Malaysian Red’ and ‘Malaysian Yellow’ the highest fruit weight and percentage edible portion is observed at color stage 5 (pericarp 100% deep red with yellow spinterns) and at color stage 4 (pericarp 100% orange with orange spintern tips), respectively (Sivakumar et al., 1998). At maturity, rambutan panicles bear 10 to 20 fruit that weigh 20 to 50 g, varying with cultivar (see Plate XXIX in the colour section). Fruit are generally 3–8 cm in diameter and 5–6 cm long, with an outer skin 2–4 mm thick. The surface of the fruit has flexible spinterns about 6–15 mm in length. The juicy aril is attached to the seed coat during development. In certain rambutan cultivars the hard testa clings to the aril (clingstone), whereas in other cultivars the aril easily separates from the seed (freestone) (Watson, 1988). Freestone-type fruit with a firm, crisp flesh are preferred by consumers. 15.2.2 Respiration, ethylene production and ripening Rambutans are non-climacteric fruit that must be harvested at peak maturity, because further ripening does not continue after harvest. The respiration rates for mature fruit vary from 40 to 100 mg CO2·kg−1·h−1 at 25 °C, depending on cultivar. Immature fruit have higher respiration rates (Mendoza et al., 1972). Rambutans (‘Jitlee’ and ‘R167’) grown in Hawaii had respiration rates of 85 mg CO2·kg−1·h−1 at harvest, but rates were reduced to 25, 33, and 50 mg CO2·kg−1·h−1 when fruit were stored at 10, 15, and 20 °C, respectively (Fig. 15.1) (M. Wall, unpublished data). Rambutans exhibited very low ethylene production rates. After one week of storage at 10, 15, or 20 °C, ethylene production rates were 0, 0.55, and 2.56 μg·kg−1·h−1, respectively (Fig. 15.2) (M. Wall, unpublished data). The

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Fig. 15.1

Respiration rates of rambutans (cv. Jitlee and R167) stored at 10, 15, or 20 °C.

Fig. 15.2

Ethylene production of rambutans (cv. Jitlee and R167) stored at 10, 15, or 20 °C.

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increases in respiration and ethylene production during storage were associated with postharvest disease development.

15.3

Maturity and quality components and indices

Rambutans are ready for harvest when they have reached full color (red or yellow) and a suitable eating quality. Fruit harvested before full maturity are acidic and do not improve in flavor, whereas overripe fruit tend to have a dark color, bland flavor, cloudy pulp, and puffy texture (Kosiyachinda et al., 1987). Growers generally harvest rambutan based on their personal judgment of the fruit color, or by counting the number of days from full bloom or fruit set. 15.3.1 Physical indices Visual changes in spinterns and skin color are the most common harvesting criteria for rambutans (Wanichkul and Kosiyachinda, 1982). However, fruit maturity within a tree is not uniform, so multiple harvests are practiced. Fruit of the cultivars, ‘Binjai’, ‘Lebakbulus’, ‘Rongrien’ and ‘Jitlee’, are harvested when the pericarp turns reddish orange. The Malaysian cultivar, ‘R156’, is harvested when the skin color is yellow and spinterns are yellow with pink bases. ‘R134’ fruit are harvested when the skin is red and the spinterns are red with yellow-green tips, whereas ‘Seematjan’ fruit are generally harvested when the skin and spinterns are pinkish yellow (Kosiyachinda et al., 1987). 15.3.2 Compositional changes Although the rambutan is generally harvested on the basis of skin color, flavor should also be optimal. At peak maturity, the juicy aril has an acidic sweet flavor and delicate fruity aroma. The exotic aroma of rambutan fruit was attributed to the interaction of fruity-sweet (β-damascenone, ethyl 2-methylbutyrate, furaneol) and fatty-green (2-nonenal, nonanal, 2,6-nonadienal) notes, with sweaty (phenyl acetic acid, heptanoic acid), woody [(E)-4,5-epoxy-(E)-2-decenal, lactones, vanillin], and spicy (cinnamic acid, guaiacol, etc.) notes contributing to the complexity of the flavor (Ong et al., 1998). An appealing rambutan flavor is a balance between sugars and acids, and in some cultivars, external color changes have been related to compositional quality. Mature rambutans have 17 to 21% soluble solids content (SSC), 0.18 to 0.55% titratable acidity (TA), and a 4.25 to 4.6 pH range (Kosiyachinda et al., 1987). For ‘Malwana Special Selection’, changes in pH are observed at color stage 3 (pericarp 100% yellow with yellow spintern) (pH 3 ~3.5) followed by an increase in pH (4.5) at color stage 6 (pericarp 25% orangish red and 75% dark red) (Sivakumar et al., 1998). In ‘Malaysian Red’ the aril pH increases after color stage 3 (pericarp 50% pink and 50% yellowish green), reaches pH 4.5 at optimum color stage 5 (pericarp 100% deep red with yellow spintern tips), and then decreases. A similar

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trend is observed for ‘Malaysian Yellow’, where the fruit pH at color stage 4 (pericarp 100% yellow with yellow spinterns) ranges from 4.2–4.4 and TA declines at later stages (Sivakumar et al., 1998). In ‘Malwana Special Selection’ and ‘Malaysian Red’ the SSC remains between 18–19% at color stage 6 (commercial maturity). However, the SSC in ‘Malaysian Yellow’ vary from 17–18% at commercial maturity (Sivakumar et al., 1998). Compositional changes with maturity also have been shown with ‘Seechompoo’ fruit. At color break, the SSC was 19%, TA was 0.17%, and the fruit were suitable for harvest (Lam, 1982). The red cultivars do not necessarily reach similar total soluble solids at the same color intensity. In general, the pericarp color and the SSC/TA ratio can be considered as suitable harvest indices for rambutan.

15.4

Preharvest factors affecting fruit quality

A major constraint for rambutan growers or shippers is the lack of information on the influence of preharvest practices on postharvest quality. Cultivar selection likely has the greatest impact on fruit quality and shelf life. For example, cultivars with a high surface area to volume ratio and a high density of spinterns desiccate and darken faster than cultivars with fewer spinterns (Landrigan et al., 1996b; Yingsanga et al., 2006). Cultivar ‘R167’ appears to be more resistant to fungal infection than other varieties. Also, thin-skinned cultivars are susceptible to skin splitting following heavy rainfall. Different growing practices such as pruning practices, nutrition and irrigation management, and disease control methods may affect rambutan fruit quality at harvest. There is often a direct link between the health status of the tree, fertilizer management, and yield. Also, irrigation management is important during flowering and fruit growth because drought conditions are associated with poor aril development and may accelerate water loss from the fruit via evapotranspiration. Therefore, growers are advised to monitor the irrigation inputs with readily available soil moisture sensing technology and flow meters. Flowering is affected in orchards where leaf N exceeds 1.8%, and a positive correlation exists between macronutrient levels and yield (Pohlan et al., 2008). However, future investigations are needed to relate fertilizer application with fruit composition and quality parameters. For postharvest disease control, reduction of inoculum in the orchard with preharvest fungicide sprays, sanitation, and resistant cultivars is necessary. Fruit contact with the soil must be avoided, because soil-borne inoculum can be an important source of infection for many tropical fruits, including rambutans.

15.5

Postharvest handling factors affecting quality

The main causes of postharvest losses of rambutan are weight loss, skin browning, diseases, and physical damage. Skin browning does not directly affect the taste of the aril but gives an unattractive appearance to the fruit (Ketsa and Klaewkasetkorn, 1992). Pericarp browning initiates from the top of the spintern, progresses towards

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the base, and extends to the skin. Spintern and pericarp browning are associated with desiccation, and are aggravated by mechanical injury and warm temperatures. Therefore, proper postharvest handling practices and optimum environmental conditions can minimize postharvest losses of rambutan due to skin browning. 15.5.1 Temperature management The visual appearance of rambutan fruit declines two to three days after harvest if the fruit are held at 25 °C (Watson, 1988). The loss of cosmetic appearance is directly linked to accelerated moisture loss and skin browning (Brown et al., 1985; Pantastico et al., 1975), and low temperature storage reduces color loss and disease development. The optimum storage temperature ranges from 8 to 12 °C, depending on cultivar. Maximum shelf life is reached at 7.5 °C for ‘R162’ fruit, at 10 °C for ‘Jitlee’ and ‘R156’ fruit, and at 12 °C for ‘Rongrien’ fruit (O’Hare et al., 1994). Shelf life is limited by skin browning from senescence at higher temperatures (15– 20 °C) and by chilling injury at lower temperatures (0–5 °C) (O’Hare et al., 1994). 15.5.2 Physical damage Physical damage may include bruising, breakage, scarring, and skin browning. Improper harvesting, such as dropping fruit directly into the bins, tight packing, and bulk transportation can result in bruising. The spinterns are especially delicate and susceptible to injury. Any mechanical damage accelerates spintern browning (Landrigan et al., 1996a) and provides a wound entry for postharvest pathogens. 15.5.3 Water loss Weight loss in rambutan occurs mainly as moisture loss from the pericarp, specifically through the spinterns (Agravante, 1982). The high surface area to volume ratio of the spintern (hairy nature) partly accounts for its high propensity for moisture loss. The spinterns have a stomatal density about five times greater than the fruit body, and at a higher density of spinterns, moisture loss and browning occur more rapidly (Landrigan et al., 1996b). In stored fruit, spinterns showed the greatest weight loss, followed by the skin and then the pulp (Lam et al., 1987). The weight loss of stored fruit is directly proportional to the number of spinterns on the fruit (Natuwatthana, 1981), and browning of rambutan is highly correlated with water loss (Landrigan et al., 1996b). Fruit are deemed unmarketable at weight losses greater than 25% (Landrigan et al., 1996b). A strong correlation is observed between weight loss and spintern browning (Landrigan et al., 1996b). The spinterns consistently lose more weight than the skin or the whole fruit for the first four days of storage, but after seven days, both the spinterns and the skin had lost approximately 50% of their weight. The fruit has a continuous vascular system that connects both spinterns and skin and vascular bundles are present in tissues below the skin surface closest to the aril (Yingsanga et al., 2006). The transport of water from the rambutan fruit proceeds from the peduncle through the

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skin to the base of spinterns and then to the tips of the spinterns, where water is transpired via the stomata (Yingsanga et al., 2006). ‘Seechompoo’ fruit have a higher density of stomata than ‘Rongrien’, therefore water loss and susceptibility to skin browning are greater in ‘Seechompoo’ fruit (Yingsanga et al., 2006). 15.5.4 Atmosphere The composition of the postharvest atmosphere may alter the shelf life of rambutans. Exposure to ethylene can increase disease development and hasten senescence, but in general, rambutans are fairly insensitive to ethylene exposure. Rambutans tolerate 7–12% CO2, and 3–5% O2, depending on cultivar, and the use of enhanced CO2 atmospheres can maintain the visual quality of rambutans (O’Hare et al., 1994; Sopee et al., 2006).

15.6

Physiological disorders

15.6.1 Chilling injury Rambutans are susceptible to chilling injury (CI), but the severity of the chilling response varies among cultivars and maturity stages. Most cultivars should not be stored below 10 °C. CI was reported in ‘Jitlee’, ‘R156’, and ‘Lebakbulus’ fruit at 5 to 7.5 °C (Harjadi and Tahitoe, 1991; Leong, 1982; O’Hare et al., 1994), whereas ‘R7’ and ‘R162’ fruit were tolerant of storage temperatures at 7.5 to 8 °C (Mohamed and Othman, 1988; O’Hare et al., 1994). In ‘Malaysian Yellow’ fruit at color stage 4 (pericarp 100% yellow), the skin color and eating quality were retained during storage at 10 °C, and stage 4 was regarded as the optimum maturity for cold storage of this cultivar (Wilson Wijeratnam et al., 1996). The CI symptom is a distinct bronzing in yellow cultivars, and a skin darkening in red cultivars (O’Hare et al., 1994). During CI, the pericarp of rambutans showed a decline in anthocyanin content (Wilson Wijeratnam et al., 1996). 15.6.2 Pericarp browning Rambutans lose their attractive skin color after harvest, and this becomes the most limiting factor to shelf life. The browning of the pericarp and spinterns affect the value of the fruit at market (Watson, 1988). Pericarp browning occurs as a result of water loss from the spinterns and the skin (Landrigan et al., 1994; Pantastico et al., 1975), and develops slowly even when water loss is greatly reduced by storing the fruit in a humid environment (95% RH) (Landrigan et al., 1994). The browning is typically more pronounced on the spinterns than the skin (Yingsanga et al., 2006). When spinterns are damaged at the base, by bending, this area browns more quickly than the tips (Landrigan et al., 1996b). Anthocyanins are responsible for the attractive red coloration in rambutan pericarp. They are vacuole-bound, water soluble pigments. Browning occurs as a result of a series of biochemical reactions that lead to degradation of anthocyanins

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into quinones (Nip, 1988). A reduction in anthocyanin content was noted with skin browning in rambutan (Paull and Chen, 1987). The stability or maintenance of anthocyanin concentration in plant cells is dependent on its structure (Pifferi and Cultera, 1974), which is directly linked to the pH of the cell sap (Jude, 1972; Lukton et al., 1956). With an increase of cellular pH in the pericarp mediated by moisture loss or decay, anthocyanins are gradually converted to a colorless carbinol base more susceptible to enzymatic breakdown. It was shown that the content of anthocyanin present in carbinol form (colorless form) was directly proportional to the subsequent rate of browning (Jude, 1972). Desiccation leads to loss of intracellular integrity, allowing mixing of vacuolar phenols and anthocyanins with browning-related enzymes (Chen and Hong, 1992; Underhill and Critchley, 1994). As browning increased in rambutans, total phenol levels increased, suggesting that phenolic oxidation and polymerization contribute to browning (Landrigan et al., 1996b). Polyphenol oxidase (PPO) catalyses the oxidation of phenolics to quinones that further polymerize to produce brown pigments in wounded or desiccated tissues. The activities of PPO and peroxidase (POD) were higher in spinterns than in the skin of ‘Rongrien’ and ‘Seechompoo’ fruit stored at lower RH (60–70%) at 25 °C, and the PPO activity was higher than POD activity (Yingsanga et al., 2008). The rapid desiccation of spinterns, the presence of micro-fractures in the waxy surface, and the activity of enzymes may explain the sensitivity of rambutans to pericarp browning (Landrigan et al., 1996b; Yingsanga et al., 2008).

15.7

Pathological disorders

Postharvest diseases are major factors that contribute to quality loss of rambutans stored at low temperatures for more than 7 days (O’Hare et al., 1994). Anthracnose (Colletotrichum gloeosporioides), stem-end rot (Botryodiplodia theobromae) and brown spot (Gliocephalotrichum bulbilium and G. microchlamydosporum) were identified as the main postharvest diseases in the Philippines, Thailand, and Sri Lanka (Farungsang et al., 1994; Lam et al., 1987; Sivakumar et al., 1997, 1998). In Hawaii, Lasmenia sp., Colletotrichum sp., Pestalotiopsis sp., Gliocephalotrichum simplex, G. bulbilium, and Phomopsis sp. were the predominant pathogens isolated from nine cultivars. Pestalotiopsis, Phomopsis, and Glomerella species also were reported to cause postharvest rots in Thailand (Johnson et al., 1997; Sivakumar et al., 1998). In Australia, Colletotrichum sp., Dothiorella dominicana, Fusarium sp., Penicillium sp., Pestalotipsis sp., Phoma sp., and Phomopsis sp. have been isolated from fruit stored at 0–20 °C (Johnson et al., 1997). The infection by a range of fruit rot pathogens begins in the rambutan orchard. These pathogens gain entry through lesions at the preharvest stage, or through harvesting and handling practices (Sivakumar et al., 1999). During infection, the pathogens (Colletotrichum, Botryodiplodia and Gliocephalotrichum) invade the host tissue, macerate cells, and cause soft lesions. The symptoms suggest that pectic enzymes are secreted by these pathogens during growth and colonization of the host tissue (Sivakumar et al., 2001).

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15.7.1 Postharvest pathogens Gliocephalotrichum bulbilium and G. microchlamydosporum infect both green immature and mature fruit, causing symptoms of brown spot. Fruit symptoms develop at an early stage as water-soaked light brown areas on the pericarp. With prolonged incubation under humid conditions, the brown spots enlarge and turn dark brown in color with grayish brown mycelia on the infected areas (Farungsang et al., 1994; Lam et al., 1987). Anthracnose is caused by Colletotrichum gloeosporioides. The fungus produces latent infections and gains entry through direct penetration. Fruit symptoms are evident after the color break stage and appear similar to the brown spot, although aerial mycelial growth does not appear on the symptomatic area. The initial black circular lesions increase in size and develop into large sunken areas. Orange sporulating structures develop on infected fruit under humid storage conditions at 25 °C (Lam et al., 1987). The causal organism of stem-end rot, Botryodiplodia theobromae, causes latent infections on rambutan and can also gain entry through the cut stem-ends (Sivakumar et al., 1999). Symptoms begin as dark brown areas at the stem-end region and extend over the whole fruit body within four to five days. A stem-end rot can also be caused by Phomopis species (O’Hare, 1994). The fungus, Lasmenia, causes a serious fruit rot and dieback disease of rambutan cultivars grown in Hawaii (Nishijima et al., 2002). The fruit exhibit brown to black lesions that progress to blackening and drying of the fruit. Some fruit become totally mummified. Lasmenia is the most prevalent fungal disease on rambutans in Hawaii. Lasmenia sp. has been isolated from 93% of infected fruit of cultivars, R9, R156, R167, and ‘Silengkeng’ in Hawaii. 15.7.2 Control measures Postharvest disease control may be achieved by preventing infection, eradicating infection, or delaying symptom development so that the fruit can be marketed and consumed before disease appears. Fungicides, hot water treatments, sulphiting agents, controlled or modified atmospheres, biocontrol agents, volatile compounds, and combination treatments have been studied as methods for managing postharvest diseases of rambutans. Chemical control Fungicides such as carbendazim, imazalil, iprodione, thiabendazole and benomyl were tested in the past for the control of rambutan postharvest diseases and showed different levels of effectiveness (Sangchote et al., 1997). However, increasing public concern regarding the use of fungicides on fresh produce and its deleterious effect on the environment has hastened efforts to develop alternative disease control measures. Resistance to benomyl by postharvest pathogens was reported by Farungsang et al. (1991). On the other hand these fungicides were reported to eradicate the microbial population on the fruit surface, including beneficial microbes that may inhibit opportunistic decay-causing organisms (Farungasang and Farungsang, 1992).

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Hot water treatment Hot water treatment is a common method to control postharvest diseases in fruits, but the temperature and treatment duration can have a marked effect on the color, appearance and eating quality of rambutans. The specific temperature at which the pathogen’s germination or mycelia growth is completely inactivated is known as the thermal inactivation point (Lam and Ng, 1982). The thermal sensitivity of fungal pathogens was reported to vary (Barkai-Golan and Phillips, 1973). Hot water treatment at 52 °C for three minutes can inhibit the spore germination of C. gloeosporioides and G. microchlamydosporum, but this high temperature could adversely affect rambutan quality. Hot water treatment at a lower temperature (48 °C for 1 min) helped retain the color and eating quality of ‘Malwana Special Selection’ fruit stored at 13 °C and 95% RH up to 14 days (Sivakumar et al., 1998). Hot water treatment at temperatures over 50 °C for more than one minute duration showed significant weight loss after low temperature storage. When freshly harvested fruit and fruit dipped in hot water at 48 °C for one minute were stored at 10 °C and at 95% RH for 14 days, they showed similar levels of SSC, pH and titratable acidity. However with increasing hot water temperature and duration, a decline in SSC and an increase in titratable acidity were observed mainly due to the growth of saprophytic fungi (Sivakumar et al., 1998). Rambutans subjected to hot water treatment at 48 °C for one minute and stored at 10 °C for four days showed higher retention of ascorbic acid and anthocyanins. Also, the polyphenol oxidase activity in the fruit increased with a higher temperature and longer durations of the hot water treatment, and was correlated to browning severity of the pericarp (Sivakumar et al., 1998). Volatile compounds The volatile compounds, cinnamaldehyde, benzaldehyde and acetaldehyde, have fungicidal properties. The spore germination and the radial mycelial growth of C. gloeosporioides, B. theobromae and G. microchlamydosporum were completely inhibited by cinnamaldehyde at 30 ppm, acetaldehyde at 70 ppm, and benzaldehye at 50 μL·L−1 (Sivakumar et al., 2002a). Cinnamaldehyde is considered as a potential compound for postharvest application due to its low mammalian toxicity and its use as a surface disinfectant (Sivakumar et al., 2002a). ‘Malwana Special Selection’ fruit packed in one layer in cardboard cartons impregnated with cinnamaldehyde (30 μL·L−1) sheets and held at 13.5 °C and 95% RH showed acceptable postharvest disease control, and maintenance of color and fruit quality attributes for up to 18 days. Higher concentration (over 50 μL·L−1) of cinnamaldehyde showed higher incidence of skin browning (Sivakumar et al., 2002a). A sensory panel detected a strong odor of cinnamaldehyde, which could be limiting for consumer acceptance. It was concluded that reduction in observed disease severity may be due to the effects of this volatile compound on the growth of fungi and their pectic enzyme activities during the infection process (Sivakumar et al., 2001; Smid et al., 1996). Sulphiting agents The application of sulphiting agents is prohibited on fresh produce in the USA. However, SO2 fumigation on table grapes is accepted as a pesticide at levels less

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than 10 μL·L−1 (Sivakumar et al., 2001). The sulphiting agent, K2S2O5 at 250 μL·L−1 completely inhibited the spore germination and the mycelial growth of C. gloeosporioides, B. theobromae and G. microchlamydosporum. The K2S2O5 in aqueous solution (250 μL·L−1) inhibited both pectin lyase and polygalactouronase activity of C. gloeosporioides, B. theobromae and G. microchlamydosporum in vitro and in vivo (Sivakumar et al., 2001). These compounds were reported to be fungicidal at these concentrations (FDA, 1986; Sivakumar et al., 2000a). The K2S2O5 in aqueous solution dissociates to liberate SO2 and the fungicidal property of the metabisulphite is due to the released SO2 (Jacobs, 1976). Rambutans (cv. Malwana Special Selection) at commercial maturity dipped in 250 μL·L−1 K2S2O5 for 10 minutes, packed in commercial cartons lined with microperforated polypropylene, and held at 13 °C and 95% RH had reduced disease incidence, severity, and pericarp browning and acceptable eating quality for up to 18 days (Sivakumar et al., 2000a). The titratable acidity and SSC in K2S2O5-dipped fruit remained unchanged. Although the ascorbic acid and anthocyanin contents decreased during storage, a delay in this decrease was noted in comparison to the untreated fruit (Sivakumar et al., 2000a). However, application of K2S2O5 remains restricted due to the FDA and EPA regulations. Biocontrol agents As importing countries have enforced restrictions against pesticide residues on fresh fruit, research has increased on biocontrol treatments to replace fungicide applications. Biocontrol agents are commonly occurring nonpathogenic microbes such as fungi, bacteria or yeast antagonists. Generally, biocontrol agents are recommended for postharvest treatment rather than field application, because the storage environment can be controlled to favor the growth of the antagonist. Controlled atmospheres or modified atmospheres may especially favor the growth of a yeast antagonist. Anthracnose (C. gloeosporioides) incidence in mature rambutans was reduced from 85% to 42.5% after a bacterial antagonist cell suspension dip (unspecified) during storage at 13 ° C for 20 days. On the other hand, Pestalotiopsis sp. was controlled completely whereas Phomopsis sp. showed moderate disease incidence. Conversely, B. theobromae showed a higher disease incidence under the above mentioned storage conditions with a bacterial antagonist postharvest treatment (Farungsang et al., 1994). The biocontrol agent, Trichoderma harzianum, has been tested widely to control plant disease (Papavizas, 1985). T. harzianum showed antagonist activity against rambutan pathogens, C. gloeosporioides, B. theobromae and G. microchlamydosporum, with the highest effect against G. microchlamydosporum (Sivakumar et al., 2000b). The mode of action of T. harzianum is reported as mycoparasitism, secreting cell wall degrading enzymes such as glucanase and chitinases (Elad, 1995), but T. harzianum also is known to produce antifungal substances such as alkyl pyrones, inhibitory furanone, and antibiotic peptides (Claydon et al., 1987; Goulard et al., 1995; Ordentlich et al., 1992). Rambutan (cv. Malwana Special Selection) dipped in conidial suspension of T. harzianum and stored at 13.5 °C and 95% RH showed a significant reduction in natural

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infections and maintained postharvest fruit quality up to 12 days (Sivakumar et al., 2000b). It was concluded that the T. harzianum showed a residual effect, and a high recovery of the agent was observed after storage on the fruit surface, demonstrating its potential use as a protectant during the supply chain to prevent cross contamination. Integrated treatments Integrated approaches for controlling postharvest diseases show promise for extending the shelf life of rambutans. Practices that combine the use of biological control agents with reduced concentrations of fungicides, with modified atmosphere packaging (MAP), or with controlled atmosphere (CA) storage have been suggested (Govender et al., 2005; Sivakumar et al., 2007). A combination of MAP or CA with biocontrol agents may be synergistic if the specific gas composition around the fruit allows the antagonists to survive while being less favorable to pathogens. This concept was investigated to control anthracnose, brown spot and stem-end rot during long term storage and transportation to distant markets. Rambutans dipped in K2S2O5 (250 ppm) and stored under CA (3% O2 and 7% CO2) at 13.5 °C and 95% RH for 21 days, showed significantly lower disease incidence (25%) when compared to control fruits (48%) (Sivakumar et al., 2002b). Also, color retention and eating quality were improved for the treated fruit. The CA conditions (3% O2 and 7% CO2) were tested using the biocontrol agent T. harzianum in order to replace the application of sulphiting agent. Fruit dipped in T. harzianum conidial extracts and stored under CA (3% O2 and 7% CO2) at 13.5 °C and 95% RH for 21 days had reduced postharvest disease incidence, but the fruit marketability was still impacted by browning due to decay and poor eating quality (Sivakumar et al., 2002b). Another integrated process includes the use of sulfur dioxide (SO2) and hot water dips. Rambutans were fumigated with 3% SO2 for 10, 20, 40 and 80 min, subjected to hot water treatment at 50 °C for 20 minutes, dipped in 1M HCl for 2 minutes, packed in plastic punnets and stored at 22 °C for six days (Paull et al., 1995). The fruit were free of surface decay, but the spinterns and skin color were affected. The SO2 treated fruit had greater weight loss than non-SO2 treated fruit, that could be due to the rapid drying of pericarp (Paull et al., 1995).

15.8

Insect pests and their control

Surface pests such as mealy bugs, scales, thrips, mites, and ants are common on rambutans. Although these insects do not directly damage the aril, they affect the cosmetic appearance of the fruit skin (Ketsa and Klaewkasetkorn, 1992), and may impede successful marketing and export of rambutans. Rambutans are also hosts for the Mediterranean fruit fly (Ceratitis capitata) and the oriental fruit fly (Bactrocera dorsalis), and require quarantine treatment prior to export to a country or region in which these pests are not established (Follett and Sanxter, 2000).

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15.8.1 Quarantine treatments Port-of-entry inspection is used to provide phytosanitary security for rambutan surface pests. However, if external pests (i.e. mealy bugs, scales, ants) are intercepted on commercial shipments, quarantine action may be taken. For quarantine security against fruit flies, heat or irradiation treatments may be used. A hot forced-air treatment involves heating the fruit to a seed surface temperature of 47.2 °C for one hour and holding at 47.2 °C for 20 minutes for disinfestation of fruit flies (Follett and Sanxter, 2000). However, based on fruit quality, irradiation is superior to hot forced-air as a quarantine treatment for rambutans (Follett and Sanxter, 2000). Fruit treated with hot forced-air had poor visual quality after four days of storage at 10 °C, whereas irradiated fruit remained acceptable for eight days. Irradiation treatment with 400 Gy provides quarantine security against fruit flies and surface pests (mealy bugs and scales) and is the commercial treatment used for rambutans exported from Hawaii to the US mainland.

15.9

Postharvest handling practices

15.9.1 Harvest operations Rambutan harvest frequency varies throughout Asia. Fruit is harvested weekly with about three to ten harvests per season in Indonesia. However, in Malaysia, the Philippines, Thailand, and Hawaii harvesting is more frequent, depending on the market situation (Laksmi et al., 1987). Individual trees in an orchard usually are harvested once, with the harvest spread over several days, and manual harvesting in the early morning with pruning shears or pole pruners is common. The fruit is harvested in clusters that may then be tied together in bunches. In some countries, pickers use baskets made of leaves or bamboo to collect the harvested fruit and to prevent fruit fall during harvesting. Fruit separation from the panicle is done in the field under shade, and the fruit are collected in clean plastic crates or bins. Rapid transfer of fruit from the orchard to the packinghouse is recommended to retain postharvest quality during storage but fruit must be handled gently to prevent mechanical damage during harvest and handling. 15.9.2 Packinghouse practices Rapid cooling of fruit reduces moisture loss and is the first stage of packinghouse practices. Among precooling methods, hydrocooling is an efficient method to remove field heat from the fruit, thereby reducing weight loss, retarding color changes, and improving shelf life (Nampan et al., 2006). In Australia, harvested fruit are hydrocooled by spraying with cool water to dissipate field heat, or watersprayed and placed in a high humidity room held at 8 to 10 °C. Rambutans (cv. Rongrien) harvested at color stage 4–5 (light red and green spintern) and hydrocooled at 10°C prior to cold storage at 13 °C had less skin browning, with a lighter red fruit pericarp, than the non-hydrocooled fruit (Nampan et al., 2006). Hydrocooling efficiently reduced the weight loss, respiration rate and changes in

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ascorbic acid content, titratable acidity and SSC in the aril during storage at 13 °C. However when fruit were hydrocooled at 2 °C, CI, weight loss, and respiration rates increased, and fruit quality parameters declined during storage (Nampan et al., 2006). Many orchards have developed a postharvest handling system which includes destalkers, dip tanks, sorting tables, a size grader, and an area for assembling cartons and packing (Lim and Diczbalis, 1995). Fruit sorting and sizing is done with sizing rings, by fruit weight, or by classifying the fruit according to different grades to meet market requirements. Rambutans are not typically waxed before packaging. However, some wax formulations have been studied to determine the effect on rambutan weight, color, and postharvest decay (Mendoza et al., 1972; Sivakumar et al., 1998). Fruit waxed and stored at 10 °C for 14 days retained red color, whereas the unwaxed fruit turned a dull red color (Mendoza et al., 1972). Following grading, rambutans are packaged in 2.25 kg and 4.5 kg fiberboard boxes. Sometimes the fruit are prepacked in clamshell containers or microperforated plastic bags. In Southeast Asia, fruit clusters are sold with the stems still attached.

15.9.3

Control of ripening and senescence

Controlled atmospheres The ripening process for rambutans ceases at harvest, and therefore cannot be controlled postharvest. However, some technologies may slow senescence and pericarp darkening, thereby extending shelf life. Rambutans (cv. Malwana Special Selection) stored 21 days under CA conditions (3% O2 and 7% CO2) at 13.5 °C showed excellent color retention, but a higher rate of decay (Sivakumar et al., 2002b). The eating quality of the fruit also was adversely affected under CA conditions. Fruit (cv. Rongrien) stored under low O2 atmosphere (1%) at 13°C and 90–95% RH were absent of visible injury, but developed off-flavors in the aril after five days of storage (Ratanachinakorn et al., 2005). The CO2 levels at 20% and 40% caused skin and spintern browning after ten and five days of storage, respectively, and off-flavor development after five days. For ‘Rongrien’ fruit, CA conditions at 5 to 10% CO2 and ≥ 2% O2 prolonged the storage life of this cultivar, and low O2 provided better disease control than high CO2 (Ratanachinakorn et al., 2005). However in another study, ‘Rongrien’ fruit at export ripeness (color stage 4–5 with light red peel and green spinterns) stored at different CO2 concentrations (1 to 15% CO2) at 13 °C and 90–95% RH showed reduced weight loss, respiration and ethylene rates, and delayed senescence at the highest CO2 levels (Sopee et al., 2006). Shelf life was extended up to 20 days in 10–15% CO2 and up to 18 days in 5% CO2 storage, although postharvest disease control and sensory quality were not investigated. Modified atmosphere packaging The use of modified atmosphere packaging (MAP) for rambutans has the advantages of low cost compared to CA, easy implementation, and effectiveness at reducing water loss and preventing skin browning by maintaining a high RH around the fruit.

Rambutan (Nephelium lappaceum L.)

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Strict low temperature management is essential for postharvest use of MAP. Rambutans packed in foam trays, wrapped with plastic film, and stored at 15 °C for ten days, showed absence of disease symptoms and retention of overall fruit quality, whereas fruits stored at 20 °C showed rapid disease development and a shorter shelf life (Johnson et al., 1997). ‘Jitlee’ fruit packed in sealed polyethylene bags and stored at 10 °C showed reduced browning and decay up to 12 days, with CO2 levels reaching 7.5% to 9.2% (Lee and Leong, 1982). Rambutan quality may be negatively affected when fruit in MAP are subjected to temperature fluctuations during shipping, handling, or at retail display. Rambutans packaged in clamshell containers, microperforated bags, or MAP film (Peakfresh®) had higher visual quality and less disease incidence when stored at constant 10 °C compared to fluctuating shipping temperatures (M. Wall, unpublished data). The simulated shipping temperatures affected disease incidence for fruit in clamshells or microperforated bags with incidences three times higher (68% versus 20%) and two times higher (60% versus 30%), respectively, than when storage was at constant 10 °C. Rambutans stored in MAP (Peakfresh®) had the best overall external quality ratings and lowest disease incidence, but sensory analysis revealed adverse affects on fruit flavor. Further research is needed to optimize MAP for fluctuating temperatures and to identify suitable films that can extend storage life up to 21 days for specific export markets. 15.9.4 Cold chain management The weight loss, and subsequent appearance, of rambutan fruit is markedly affected by storage temperature (Inpun, 1984; Mendoza et al., 1972; Mohamed and Othman, 1988). A narrow temperature range must be maintained during cold chain management in order to minimize moisture loss, pericarp browning, and disease incidence without causing CI. For ‘Maharlika’ fruit, weight loss was reduced by 28% after six days storage at 7 °C, but fruit suffered CI. The longest shelf life (10 to 12 days) was at 10 °C (Mendoza et al., 1972). Also, when ‘Malwana Special Selection’ fruit at color stages 4 (pericarp 75% yellow and 25% pinkish red), 5 (pericarp 75% yellow and 25% pinkish red) and 6 (pericarp 25% orange-red and 75% dark red) were stored long term (up to 21 days) at 5, 10 and 14 °C, CI was noted at 5 °C for all three color stages, whereas reduced skin browning was observed at 10 °C for color stages 5 and 6 (Wilson Wijeratnam et al., 1995). The SSC and TA values were similar to freshly harvested fruit for all three color stages at 5 °C and 10 °C, but a slight decline in SSC and increase in TA were noted at 14 °C (Wilson Wijeratnam et al., 1995). Ascorbic acid content declined during storage at 10 °C and 14 °C compared to fruit held at 5 °C (Wilson Wijeratnam et al., 1995). A sensory panel showed higher preference for color stage 5 and 6 fruit stored at 10 °C. A similar investigation conducted for ‘Malaysian Red’ fruit at color stages 3 (pericarp 50% pink and 50% yellowish green), 4 (pericarp 75% pink, rest 25% dark red) and 5 (pericarp 100% deep red) showed that fruit at color stages 4 and 5 retained skin color and eating quality at 14 °C and 95% RH for 14 days (Wilson Wijeratnam et al., 1996). The storage life of ‘Malaysian Yellow’ was limited to seven days, and 10 °C was selected as the optimum storage temperature.

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15.9.5 Recommended storage and shipping conditions The optimum storage conditions for rambutans are 8–12 °C and 95% RH, depending on cultivar (Mendoza et al., 1972; O’Hare et al., 1994). For most cultivars, the optimum temperature is 10 °C. Under ideal conditions, rambutans have a storage potential of 14 days. Shelf life may be extended by four days with 9–12% CO2 (O’Hare et al., 1994). Rambutans do not benefit from ethylene treatment or ethylene scrubbing (O’Hare et al., 1994).

15.10

Processing

15.10.1 Fresh-cut processing Rambutans have limited use as a fresh-cut product, because it is difficult to separate the aril from the seed. In one study, minimally processed peeled rambutans (with seeds) had a 10 day shelf life when stored at 4 °C in nylon/LLDPE bags (Sirichote et al., 2008). Attempts to peel and core the fruit severely damaged the aril tissue and increased the respiration rates.

15.10.2 Other processing practices Although rambutans are grown for fresh consumption, some fruit are canned with syrup in Thailand and Malaysia. Also, individual quick frozen (IQF) rambutans are processed on a small scale. Local processors may use rambutans in boutique jams, jellies, sorbets, ice cream, and wines.

15.11

Conclusions

The attractive and exotic rambutan fruit, with its bright red or yellow color and distinctive spinterns, easily desiccates and browns during postharvest storage. The delicate, hair-like spinterns may be damaged during handling and rapidly lose water, turning brown or black. Storing fruit at 10 °C and 95% RH under modified atmospheres is most effective for retaining visual quality, and provides a 10 to 12 day shelf life. Although rambutan storage life is most limited by skin and spintern darkening, controlling postharvest diseases caused by fungal pathogens also is key to increasing shelf life. Integrated preharvest and postharvest practices that achieve disease control while reducing desiccation and browning are needed to extend rambutan shelf life beyond two weeks. Potential areas for future research include:

• •

the application of combination treatments (MAP, anti-fungal compounds, antioxidants, or biocontrol agents) to prevent pericarp browning, control postharvest diseases, and maintain edible fruit quality; investigations on cultivar resistance to postharvest diseases and the mechanisms of resistance;

Rambutan (Nephelium lappaceum L.)

• • •

329

studies of the mode of infection, colonization and inoculum sources of the various rambutan pathogens; controlled preharvest experiments to determine the effects of fertilization and irrigation practices on postharvest quality; development of protocols to optimize CA or MAP conditions to retain fruit color and control diseases without impacting flavor.

15.12

References

Agravante J (1982), ‘The browning disorder of rambutan. Relationship between moisture status and browning’, in Lam P F and Kosiyachinda S, Rambutan: Fruit Development, Postharvest Physiology, and Marketing in ASEAN, Kuala Lumpur, Malaysia, ASEAN, 51–55. Barkai-Golan R and Phillips D J (1973), ‘Postharvest heat treatment of fresh fruits and vegetables for decay control’, Plant Dis, 75, 1085. Brown B I, Wong L S and Watson B I (1985). ‘Use of plastic film packaging and low temperature storage for postharvest handling of rambutan, carambola and sapodilla’, Proc Postharvest Hort WorksShop, Victoria, Australia, 272–286. Chen W J and Hong Q Z (1992), ‘A study on the senescence and browning in the pericarp of litchi (Litchi chinensis Sonn.) during storage’, Acta Hort Sin, 19, 227–232. Claydon N, Allan M, Hanson J R and Avent G (1987), ‘Antifungal alkyl pyrones of Trichoderma harzianum’, Trans British Mycol Soc, 88, 503–513. Elad Y (1995), ‘Mycoparasitism’, in Kohmoto K, Singh U S, and Singh R P, Pathogenesis and Host Specificity in Plant Diseases. Histopathological, Biochemical, Genetic and Molecular Basis, Eukaryotes, Oxford, UK, Elsevier, pp. 289–303. Farungsang U, Farungsang N and Sangchote S (1991), ‘Postharvest diseases of rambutan during storage at 13 ° or 25 °C’, Proc 8th Austral Plant Path Soc Conf, Sydney, New South Wales, p. 34. Farungasang U and Farungsang N (1992), ‘Resistance to benomyl of Colletotrichum spp. causing anthracnose of rambutan and mango in Thailand,’ Acta Hort, 321, 891–897. Farungsang U, Sangchote S and Farungsang U (1994), ‘Rambutan postharvest diseases in Thailand’, in Johnson G I and Highly E, Development of Postharvest Handling Technology for Tropical Fruits, Australia, ACIAR, 58, 51–59. FDA (1986), ‘Food and Drug Administration food labeling: declaration of sulfating agents’, Federal Register, 51, 25012–25016. Follett P A and Sanxter S S (2000), ‘Comparison of rambutan quality after hot forced-air and irradiation quarantine treatments’, HortScience, 35, 1315–1318. Goulard C, Hilmi S, Rebuffat S and Bodo B (1995), ‘Trichorzins HA and MA, antibiotic peptides from Trichoderma harzianum: fermentation, isolation and biological properties’, J Antibiot, 48, 1249–1253. Govender V, Korsten L and Sivakumar D (2005), ‘Semi-commercial evaluation of Bacillus lichenifirmis to control mango postharvest diseases in South Africa’, Postharvest Biol Technol, 38, 57–65. Harjadi S S and Tahitoe D J (1991), ‘The effects of plastic film bags at low temperature storage on prolonging the shelf-life of rambutan (Nephelium lappaceum) cv. Lebakbulus’, Proc Interntl Symp Trop Fruits, Pattaya, Thailand, p. 67. Inpun A (1984), Effect of temperature and packaging materials (polyethylene bags, plastic baskets) on postharvest quality and storage life of rambutan (Nephelium lappaceum L.) var. Seechompoo: monograph, Department of Horticulture, Faculty of Agriculture, Kaesetsart University, Bangkok.

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Institute of Medicine (IOM) (2000), Dietary reference intake for calcium, phosphorus, magnesium, vitamin D, and fluoride, Washington, DC, National Academy Press. Jacobs D D (1976), ‘Effect of dissolved oxygen on free sulfur dioxide in red wines’, Amer J Enzy Viticult, 27, 2–45. Johnson G I, Joyce D C and Gosbee M J (1997), ‘Botryosphaeria (anamorphs Fusicoccum and Dothiorella) Diaporthe (anamorphs Phompsis spp.) and Lasiodiplodia infection and defense’, in Johnson G I and Highly E, Disease Resistance in Fruit, Australia, ACIAR, 80, 46–52. Jude L (1972), ‘Some advances in the chemistry of anthocyanin-type plant pigments’, in Chichester C O, Advances in food research supplement 3, The Chemistry of Plant Pigments, New York, Academic Press, 123–142. Kawabata A M, Nagao M A, Tsumura T, Aoki D F and Hara K Y (2007), ‘Phenology and fruit development of rambutan (Nephelium lappaceum L.) grown in Hawaii’, J Hawaiian Pacific Agric, 14, 31–39. Ketsa S and Klaewkasetkorn O (1992), ‘Postharvest quality and losses of “Rongrein” rambutan fruit in whole sale markets’, Acta Hort, 321, 771–777. Kosiyachinda S, Lam P, Mendoza D B Jr, Broto W and Wanichkul K (1987), ‘Maturity indices for harvesting of rambutan’, in Lam P F and Kosiyachinda S, Rambutan: Fruit Development, Postharvest Physiology and Marketing in ASEAN, Kuala Lumpur, ASEAN Food Handling Bureau, pp. 32–38. Kosiyachinda S and Salma S (1987), ‘Changes in rambutan during growth and development’, in Lam P F and Kosiyachinda S, Rambutan: Fruit Development, Postharvest Physiology, and Marketing in ASEAN, Kuala Lumpur, ASEAN Food Handling Bureau, pp. 28–32. Laksmi L D S, Lam P F, Mendoza Jr. D B, Kosiyachinda S and Leang P C (1987), ‘Status of the rambutan industry in ASEAN’, in Lam P F and Kosiyachinda S, Rambutan: Fruit Development, Postharvest Physiology, and Marketing in ASEAN, Kuala Lumpur, ASEAN Food Handling Bureau, pp. 1–8. Lam P F (1982), ‘Malaysian summary of research report on mango and rambutan project’, Proc Workshop on Mango and Rambutan, University of the Philippines at Los Banos, Laguna, The Philippines, pp. 21–25. Lam P F and Ng K H (1982), Storage of waxed and unwaxed rambutan in perforated and sealed polyethylene bag: report on food technology division, Selangor, Malaysian Agricultural Research and Development Institute. Lam P E, Kosiyachinda S M, Lizada C C, Mendoza D B Jr, Prabawati S and Lee S K (1987), ‘Postharvest physiology and storage of rambutan’, in Lam P E and Kosiyachinda S, Rambutan: Fruit Development, Postharvest Physiology and Marketing in ASEAN, Kuala Lupur, ASEAN Food Handling Bureau, pp. 39–50. Landrigan M, Sarafis V, Morris S C, and McGlasson W B (1994), ‘Structural aspects of rambutan (Nephelium Lappaceum) fruits and their relation to postharvest browning’, J Hort Sci, 69, 571–579. Landrigan M, Morris S C and Gibb K S (1996a), ‘Relative humidity influences postharvest browning in rambutan’, HortScience, 31, 417–418. Landrigan M, Morris S C and McGlasson B W (1996b), ‘Postharvest browning of rambutan is a consequence of water loss’, J Amer Soc Hort Sci, 121, 730–734. Lee S K and Leong P C (1982), ‘Storage studies on the rambutan in Singapore’, Proc Workshop on Mango and Rambutan, University of the Philippines at Los Banos, Laguna, The Philippines, pp. 172–175. Leong P C (1982), ‘Summary report on mango and rambutan project in Singapore’, Proc Workshop on Mango and Rambutan, University of the Philippines at Los Banos, Laguna, The Philippines, pp. 30–33. Lim T K and Diczbalis Y (1995), ‘Rambutans’, in Coombs B, Horticulture Australia—the Complete Reference on the Horticulture Industry, Victoria, Morescope Publishing, pp. 453–458.

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Lukton A, Chichester C O and Mackinney G (1956), ‘The break down of strawberry anthocyanin pigment’, Food Technol, 10, 427–432. Mendoza D B, Pantastico E and Javier F B (1972), ‘Storage and handling of rambutan (Nephelium lappaceum L.)’, Philippine Agric, 55, 322–332. Mohamed S and Othman E (1988), ‘Effect of packaging and modified atmosphere on the shelf-life of rambutan (Nephelium lappaceum L)’, Pertanika, 11, 217–228. Nampam K, Techavuthiporn C and Kanlayanarat S (2006), ‘Hydrocooling improves quality and storage life of “Rong-Rein” rambutan (Nephelium lappaceum L.) fruit’, Acta Hort, 712, 763–770. Natuwatthana S (1981), ‘Weight losses and modified atmosphere storage of rambutan (Nephelium lappaceum L.) cv. “Seechompoo” fruit’, Monograph, Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok, p. 9. Nip W (1988), ‘Handling and preservation of lychee (Litchi chinensis Sonn) with emphasis on color retention’, Trop Sci, 28, 5–11. Nishijima K A, Follett P A, Bushe B C, and Nagao M A (2002), ‘First report of Lasmenia sp. and two species of Gliocephalotrichum on rambutan in Hawaii’, Plant Disease, 86, 71. O’Hare T J, Prasad A and Cooke A W (1994), ‘Low temperature and controlled atmosphere storage of rambutan’, Postharvest Biol Technol, 4, 147–157. Ordentlich A, Wiesman Z, Gottlieth H E, Cojocaru M and Chet I (1992), ‘Inhibitory furanone produced by the biocontrol agent Trichoderma harzianum’, Phytochem, 31, 485–486. Ong P K C, Acree T E, and Lavin E H (1998), ‘Characterization of volatiles in rambutan fruit (Nephelium lappaceum L.)’, J Agric Food Chem, 46, 611–615. Pantastico E B, Pantastico J B and Cosico V B (1975), ‘Some forms and function of the fruit and vegetable epidermis’, Kalikasan Philipp J Biol, 4, 175–197. Papavizas G S (1985), ‘Trichoderma and Gliocladium: biology, ecology and potential for biocontrol’, Ann Rev Phytopath, 23, 23–54. Paull R E and N J Chen (1987), ‘Changes in longan and rambutan during postharvest storage’, HortScience, 22, 1303–1304. Paull R E, Reyes M E Q and Reyes M U (1995), ‘Litchi and rambutan insect disinfestations: treatments to minimize induced pericarp browning’, Postharvest Biol Technol, 6, 139–148. Pifferri P G and Cultera R (1974), ‘Enzymatic degradation of anthocyanins, the role of sweet cherry polyphenol oxidase’, J Food Sci, 39, 789–791. Pohlan J, Vanderlinden E J M, and Janssens M J J (2008), ‘Harvest maturity, harvesting and field handling of rambutan’, Stewart Postharvest Reviews, 2, 11. Available at http:// www.stewartpostharvest.com/Vol4_2008/April_2008/Pohlan.htm [accessed May 2011]. Ratanachinakorn B, Nanthachai S and Nanthachai N (2005), ‘Effect of different atmospheres on the quality of “Rong Rien” rambutan’, Acta Hort, 665, 381–386. Salma I (1983), Clonal variations and reproductive biology of Nephelium lappaceum L .in peninsular Malaysia, MS Thesis, University of Malaysia. Kuala Lumpur, Malaysia. Sangchote S, Farungsang U and Farubgsang N (1997), ‘Pre- and postharvest infection of rambutan by pathogens and effects of postharvest treatments’, in Coates L, Hoffman P J and Johnson G I, Disease Control and Storage Life Extension in Fruit, Australia, ACIAR, 81, 87–91. Sirichote A, Jongpanyalert B, Srisuwan L, Chanthachum S, Pisuchpen S and Ooraikul B (2008), ‘Effects of minimal processing on the respiration rate and quality of rambutan cv. Rong-Rien’, Songklanakarin J Sci Technol, 30, 57–63. Sivakumar D, Wilson Wijeratnam R S, Wijesundera R L C and Abeyesekere M (1997), ‘Postharvest diseases of rambutan (Nephelium lappaceum) in the Western Province’, J Nat Sci Council Sri Lanka, 25, 225–227. Sivakumar D, Wilson Wijeratnam, R S and Abeyesekere M (1998), Report on minimizing postharvest loss of rambutan in storage, Sri Lanka, Council of Agricultural Research Policy.

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Sivakumar D, Wilson Wijeratnam R S and Wijesundera R L C (1999), ‘Field sanitation and the occurrence of brown spot disease of rambutan (Nephelium lappaceum) fruits’, J National Sci Council Sri Lanka, 27, 93–97. Sivakumar D, Wilson Wijeratnam R S, Wijesundera R L C and Abeyesekere M (2000a), ‘Effect of potassium metabisulphite on low-temperature storage of rambutan’, Trop Sci, 40, 29–37. Sivakumar D, Wilson Wijeratnam R S, Wijesundera R L C, Marikar F M T and Abeyesekere M (2000b), ‘Antagonistic effect of Trichoderma harzianum on postharvest pathogens of rambutan (Nephelium lappaceum)’, Phytoparasitica, 28, 240–247. Sivakumar D, Wilson Wijeratnam R S and Wijesundera R L C (2001), ‘Effect of GRAS compounds on mycelial growth, pectic enzyme activity and disease severity of postharvest pathogens on rambutans (Nephelium lappaceum)’, Phytoparasitica, 29, 135–141. Sivakumar D, Wilson Wijeratnam R S, Wijesundera R L C and Abeyesekere M (2002a), ‘Control of postharvest diseases of rambutan using cinnamaldehyde’, Crop Protection, 21, 847–852. Sivakumar D, Wilson Wijeratnam R S, Wijesundera R L C and Abeyesekere M (2002b), ‘Control of postharvest diseases of rambutan using controlled atmosphere storage and potassium metabisulphite or Trichoderma harzianum’, Phytoparasitica, 30, 403–409. Sivakumar D, Zeeman K and Korsten L (2007), ‘Effect of biocontrol agent (Bacillus subtilis) and modified atmosphere packaging on postharvest decay control and quality retention of litchi during storage’, Phytoparasitica, 35, (5), 507–518. Smid E J, Hendriks L, Boerrigater H A M and Gorris I G M (1996), ‘Surface disinfecting of tomatoes using the natural plant compounds trans-cinnamaldehyde’, Postharvest Biol Technol, 9, 343–350. Sopee A, Techavuthiporn C and Kanlavanarat S (2006), ‘High carbon dioxide atmospheres improve quality and storage life of rambutan (Nephelium lappaceum L.) fruit’, Acta Hort, 712, 865–871. Tindall, H D (1994), ‘Rambutan cultivation’, FAO Plant Production and Protection Paper No. 121, Rome, FAO, 162 pp. Tongumpai P (1980), The study on floral, fruit and pulp development of rambutan (Nephelium lappaceum L. ‘Seechompoo’), Master’s Thesis, Kasetsart University, Bangkok, Thailand. Underhill S J R and Critchley C (1994), ‘Anthocyanin decolouratisation and its role in lychee pericarp browning’, Aust J Exp Agric, 34, 115–122. Van Weizen P C and Verheij E W M (1991), ‘Nephelium lappaceum L.’, in Verheij E W M and Coronel R E, Plant Resources of South-East Asia, Wageningen, the Netherlands. Wall M M (2006), ‘Ascorbic acid and mineral composition of longan (Dimocarpus longan), lychee (Litchi chinensis) and rambutan (Nephelium lappaceaum) cultivars grown in Hawaii’, J Food Comp Anal, 19, 655–663. Wanichkul K and Kosiyachinda S (1982), ‘Fruit development and harvesting index of rambutan (Nephelium lappaceum Linn.) var Seechompoo’, Proc. Workshop Mango Rambutan, University of the Philippines, Los Banos, 21–27. Watson B J (1988), ‘Rambutan cultivars in north Queensland’, Queensland Agric J, 114, 37–41. Wills R B H, Lim J S K, and Greenfield H (1986), ‘Composition of Australian foods. 31. Tropical and sub-tropical fruit’, Food Technol Australia, 36, 118–123. Wilson Wijeratnam R S, Abesekere A, and Sivakumar D (1995), ‘Studies on maturity indices for low temperature storage of Sri Lankan “Malwana special selection” rambutans’, Proc. Interntl Symp Postharvest Sci Techno Hort Crops, Beijing, China, p. 18. Wilson Wijeratnam R S, Abesekere A and Sivakumar D (1996), ‘Studies on maturity and low temperature storage of three rambutan cultivars grown in Sri Lanka’, Acta Hort, 464, 514.

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Yingsanga P, SriLaong V, Kanlayanarat S, McGlasson W B, Kabanoff E and Noichinda, S (2006), ‘Morphological differences associated with water loss in rambutan fruit cv. Rongrien and See-Chompoo’, Acta Hort, 712, 452–460. Yingsanga P, Srilaong V, Kanlayanarat S, Noichinda S and McGlasson W B (2008), ‘Relationship between browning and related enzymes (PAL, PPO and POD) in rambutan fruit (Nephelium lappaceum Linn.) cvs. Rongrien and See-Chompoo’, Postharvest Biol Technol, 50, 164–168.

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Plate XXVII

(Chapter 14) Husks scald symptom on pomegranate fruit (Defilippi et al., 2006).

Plate XXVIII (Chapter 15) Rambutan fruit (cv. R9), showing peel with hair-like spinterns and internal edible flesh.

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Plate XXIX

(Chapter 15) Panicles of mature rambutan fruit.

(a)

Plate XXX

(b)

(Chapter 16) Mature (a) and immature (b) Salak Pondoh.

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16 Salak (Salacca zalacca (Gaertner) Voss) S. Supapvanich, Kasetsart University, Thailand, R. Megia, Bogor Agricultural University, Indonesia and P. Ding, University of Putra Malaysia, Malaysia

Abstract: The salak is an indigenous palm found throughout the Indo-Malaysian region. It is a small spiny palm that grows on moist well drained soil with high organic matter content. The fruit is drupe oval or spindle shaped (like a fig) with a distinct tip, tapering towards the top and rounded at the top end. The skin is covered with regularly arranged scale, creating an appearance similar to that of snake skin, from which the name ‘snake skin fruit’ is derived. The salak is a crunchy fruit that has a taste that combines the flavours of apple, banana, and pineapple. It is a good source of antioxidants that cannot be matched by other tropical fruits. Key words: salak, Salacca zalacca, Salacca edulis, snake skin fruit, spiny palm, Indo-Malaysia region.

16.1

Introduction

16.1.1 Origin, botany, morphology and structure The salak (Salacca zalacca, syn. S. edulis, Calamus zalacca) belongs to the family Palmae or Arecaceae genus Salacca, which is the only family in the monocot order Arecales. It is an indigenous palm found throughout the Indo-Malaysian region, i.e. Thailand, Indonesia, Malaysia, Cambodia and South of Myanmar, Vietnam, Philippines and China (Draft ASEAN Standard for Horticultural Produce, 2009; Lestari and Ebert, 2002; Rangsiruji et al., 2006; Supriyadi et al., 2002; Wijaya et al., 2005). It has been introduced into the countries of New Guinea and Queensland, Australia (Lestari and Ebert, 2002). There are 21 species and four varieties of Salacca (Rangsiruji et al., 2006). In Thailand, the salak is cultivated in the eastern and southern parts of the country and the main commercial species grown are S. wallichiana Mart and S. rumphii, known as Rakam and Sala, respectively, by Thais (Dangcham, 1999; Thangjatuporn,

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Salak (Salacca zalacca (Gaertner) Voss)

Fig. 16.1

335

Salacca rumphii Wall (Sala) (A) and Salacca wallichiana Mart (Rakam) (B).

2000) (Fig. 16.1). There are three main species of salak grown commercially in Malaysia, which are S. glaberescens, S. edulis and S. sumatrana (Abu Bakar and Idris, 2006). S. glaberescens is known as local salak and there are nine clones being bred for planting (Tables 16.1 and 16.2), while S. edulis and S. sumatrana are the two species of salak introduced from Indonesia. In Indonesia, the important commercial cultivars for domestic and export markets are S. zalacca (Gaertner) Voss with the synonim S. edulis (Reinw) (Mogea, 1982) (Fig. 16.2A) and S. sumatrana Becc. S. zalacca is subdivided into two varieties, var. zalacca from Java and var. amboinensis (Becc.) Mogea from Bali (Fig. 16.2B) and Ambon. S. sumatrana is more commonly known as salak Padang Sidempuan (North Sumatra). In Indonesia there are more than 30 cultivars of salak, which are often distinguished by their place of origin (eg.: salak ‘Bali’, ‘Suwaru’, ‘Condet’, or ‘Enrekang’, ‘Padang Sidempuan’), fruit taste (eg.: salak ‘gula pasir’, ‘pondoh’, or ‘madu’), or fruit colour (eg.: salak ‘putih’ or ‘gading’). The cultivar may also be

Fig. 16.2

Salacca edulis, Reinw (Salak Pondoh) (A) and Salacca zalacca var. amboinensis (Salak Bali) (B).

© Woodhead Publishing Limited, 2011

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14–18 61

Dark brown White

Firm and juicy

Sourish sweet

14–18

57

Skin colour Flesh colour

Texture

Taste

Soluble solids concentration (°Brix) Edible portion (%)

Sourish sweet and aromatic

Juicy and crunchy

Brown Light orange

50–62 6–9 4–6 Oval with sharp tip

64–84 7–9 4–6 Round

SJ17

Weight (g) Length (cm) Width (cm) Shape

SJ15

Clone

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63

Sweet with slight astringent and aromatic 16–20

65–100 8–10 4–8 Oval with long sharp tip Brown Light yellow

SJ34

64

18–20

Firm and slightly juicy Sourish sweet

Red brown Pale orange

66–85 6–8 4–6 Round

SJ36

Physico-chemical characteristics of Malaysian salak, S. glaberescens clones

Fruit characteristics

Table 16.1

SJ40

69

16–19

Sweet with slight astringent

69

16–20

Sweet

50–85 6–9 5.7–7.5 3–5 5–6.7 Oval with sharp tip Round with sharp tip Dark brown Brown Light orange Red spot at bottom of flesh Soft Firm and juicy

SJ39

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 43 44 45X

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337

Physico-chemical characteristics of selected salak clones in Terengganu,

Fruit characteristics

Clone ST1

ST2

ST3

Weight (g) Length (cm) Width (cm) Shape Skin colour Flesh colour Texture Taste

80 8–10 4–6 Oval to oblong Reddish-brown Creamy white Juicy Sweet with slight astringent 16–20

75 6–8 4–6 Round to oval Reddish-brown Creamy white Juicy and crunchy Sweet

68 6–9 3–5 Oval with long sharp tip Reddish-brown Creamy white

15–18

Sweet with slight astringent 17–19

0.73

0.63

0.73

22.5 81 63

26.7 83 64

22.5 81 69

Soluble solids concentration (SSC) (°Brix) Titratable acidity (TA) (%) SSC/TA ratio Water content (%) Edible portion (%)

divided into sub-cultivars, i.e. salak ‘pondoh’ is divided into: ‘pondoh super’, ‘pondoh hitam’ and ‘pondoh manggala’. Some superior salak varieties that have been officially released by the Department of Horticulture, Agricultural Ministry of Indonesia Government include: salak ‘pondoh’, ‘suwaru’, ‘nglumut’, ‘enrekang’ (Celebes), and ‘gula batu’ (Bali). The salak is an extremely spiny palm, which does not form a trunk and which grows on a wide range of soils but prefers moist well-drained soil with high organic matter content (Kueh, 2003). It requires shade and is best intercropped with banana, durian, rubber, oil palm, coconut and cocoa. It is about 6 m tall. The leaves pinnate can reach 10 m long and 1.50 m wide; each leaf has a 2 m long spiny petiole and numerous leaflets measuring 20–89 cm long and 2–11 cm wide. The upper surface of the leaflets is dark green and shiny, while lower surface is light green. Long, strong, grey to blackish spine clusters are distributed along the frond base at intervals of 3–5 cm. The palm fruits at about 3–4 years after planting. It is usually dioecious, although some have been found to be monoecious (e.g. Salak Bali) where they could self pollinate. The inflorescence is an axillary compound spadix with a stalk: the female inflorescences are 20–30 cm long, and are composed of 1–3 spadices, 7–10 cm long; the male inflorescences are 50–100 cm long, consisting of 4–12 spadices, each measuring 7–15 cm × 0.7–2 cm. About 20% of the male palms are retained as pollinators, while the rest are removed. Assisted pollination is carried out to improve the fruit set.

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The fruit of the salak grows in clusters of 15–40 fruits/spadix, at the base of the palm. The fruit is drupe oval or spindle shaped (like a fig) with a distinct tip; it measures 5–8 cm × 5 cm, tapering towards the top and rounded at the top end and fits comfortably into a human palm and weighs about 70 g, depending on the species and variety. The skin, which is thin and strong, is covered with regularly arranged scales, which serve to create an appearance similar to that of snake skin, from which the name ‘snake skin fruit’ is derived. The colour of the fruit skin is reddish-brown to brown or dark brown, depending upon the species and cultivars (the skin of mature Thai Rakam and Sala fruits are reddish-brown [Thangjatuporn, 2000]). To peel the fruit, simply pinch the tip of the fruit and pull away, revealing the garlic-like clove inside, which is arranged in 1–3 irregular sized segments. Before eating the fruit, a paper-thin layer of membrane covering each segment needs to be rubbed off. Usually two of the three segments are bigger and each segment contains a large inedible dark brown seed, while the third segment is smaller and seedless. The taste is usually sweet and acidic with a pineapple, pear or banana-like aroma, and an apple-like texture, which can vary from very dry and crumbly to moist and crunchy or soft, depending on the species and cultivar. Rakam and Sala fruits grown in Thailand have creamy, moist, soft and thin flesh (Thangjatuporn, 2000). The salak fruit is astringent too due to its high tannin content. Generally, most salak fruits, such as Thai Rakam and Sala, have a sour and astringent taste during the immature stages (Supriyadi et al., 2002; Thangjatuporn, 2000) but become sweeter and lose their astringent taste during maturation. An exception to this trend is the Salak Pondoh (Lestari and Ebert, 2002; Wijaya et al., 2005). The salak is usually propagated from seeds, of which 50% of the seedlings will be males and the fruit produced are not uniform in quality (Abu Bakar and Idris, 2006). By propagating using suckers, it is possible to retain the characteristics of mother palms. Unfortunately, a palm can only produce 2–10 suckers in its life cycle, moreover, the mortality rate is about 40%. Recently, a few propagating techniques have been established to increase the number of seedlings using female palms that have produced a good quality of fruit. Splitting a 6–12 month old young palm into pieces with leaf, pseudostem and roots has been proven as one of the techniques. Inducing the growth of suckers using diesel or methamidophos has been practiced too. This technique removes the apical dominance of female palms by killing the meristem cells. 16.1.2 Worldwide importance and economic value Salak fruit has become an exotic and prominent fruit with good potential for both the domestic market and for export. The demand for the fruit per year is about 420 000 tons, including fresh consumption, processed fruit and export. Recently, the demand for the fruit in China, Japan, Europe and United States has increased. The popularity of the fruit has increased since Salak Pondoh was recognized and became a commercial fruit. Indonesia produces 60–70% (334 000 tons) of the world’s salak fruit and exports about 32 755 tons year−1 (Dimyati et al., 2008). In

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Salak (Salacca zalacca (Gaertner) Voss) Table 16.3 and 2007

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Production of salak fruit in Indonesia in 2006

Region/Island

Sumatera Jawa Bali and Nusa Tenggara Kalimantan Sulawesi Maluku and Papua Total

Production (tons) Th 2006

Th 2007

265 815 479 898 63 073 19 039 32 600 1 525 861 950

260 702 419 298 79 933 28 725 16 111 1 110 805 879

Modified from Dimyati et al. (2008).

Table 16.4 Province Jantaburi Trad Chonburi Kanchanburi Total

Production of salak fruit in Thailand in 2008 Average yield (kg ha−1) Total production (tons) 8 356.25 18 062.50 4 687.50 10 181.25 41 287.50

1 507 7 745 15 81 9 348

Modified from Department of Agricultural Extension (2008).

2006, Indonesian salak was being exported to Singapore, Malaysia and Hong Kong in volumes of about 4–10 tons per week. In 2008, the consumption per capita of the fruit in Indonesia was about 1.64 kg year−1 (Dimyati et al., 2008). The production of salak fruit in Indonesia is shown in Table 16.3. In Thailand, Rakam and Sala cv. ‘Nernwong’ and ‘Saynampueng’ are an important commercial fruit in the domestic market and the demand for the fruit both domestically and abroad has been increasing. The fruit has been exported to Singapore, Hong Kong and Malaysia (Thangjatuporn, 2000). The average yield and total production of salak fruit in Thailand are shown in Table 16.4. 16.1.3 Culinary use, nutritional value and health benefits Salak fruit is a good source of antioxidants (Aralas et al., 2009; Leong and Shui, 2002; Lim et al., 2007). With a level higher than that of other tropical fruits such as mangosteen, avocado, orange, papaya, mango, pomelo, lemon, pineapple, rambutan, banana and watermelon (Aralas et al., 2009; Leong and Shui, 2002). The nutritional values of salak fruit are shown in Table 16.5. The high level of antioxidants is due to salak having a high content of phytochemicals such as

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Table 16.5

Phytonutrients and minerals in salak fruit

Dietary fibre (b) Insoluble fibre Soluble fibre Total dietary fibre Total antioxidant capacity (b, c) Total DPPH Total ABTS Flavonoid (b) Free flavonoids Total flavonoids Phenolic content (b) Free polyphenol Total phenolic Ascorbic acid content (a) Minerals and trace elements (b) Na K Mg Ca Fe Mn Zn Cu

0.75 ± 0.07 g 100 g−1 fresh weight 0.35 ± 0.04 g 100 g−1 fresh weight 1.1 ± 0.1 g 100 g−1 fresh weight 110.4 ± 7.9 mM TE 100 g−1 fresh weight 260 ± 32.5 AEAC mg 100 g−1 fresh weight 14.1 ± 0.9 mg CE 100 g−1 fresh weight 61.2 ± 4.9 mg CE 100 g−1 fresh weight 33.2 ± 1.7 mg GAE 100 g−1 fresh weight 217.1 ± 13.2 mg GAE 100 g−1 fresh weight 0.73 − 1.28 mg 100 g−1 fresh weight 1.9 ± 0.1 mg 100 g−1 fresh weight 191.2 ± 12.6 mg 100 g−1 fresh weight 7.16 ± 0.5 mg 100 g−1 fresh weight 6.11 ± 0.4 mg 100 g−1 fresh weight 301.7 ± 11.2 μg 100 g−1 fresh weight 249.9 ± 11.7 μg 100 g−1 fresh weight 35.1 ± 2.9 μg 100 g−1 fresh weight 8.4 ± 0.6 μg 100 g−1 fresh weight

Modified from (a) Aralas et al. (2009), (b) and (c) Haruenkit et al. (2007), Leong and Shui (2002).

lignin, flavonols, and gallic acid. These chemicals have been shown to inhibit proliferation and induce selective cytotoxicity and apoptosis in cancer cells (Aralas et al., 2009; Lin et al., 2008; Surh et al., 1999). Gorinstein et al. (2009) found there was similarity between salak (cv. ‘Sumalee’) and kiwi fruit (cv. Hayward) in terms of their antioxidant and antiproliferative effects on two human cancer cell lines (Calu-6 for human pulmonary carcinoma, and SMU-601 for human gastric carcinoma, 90.5–87.6 and 89.3–87.1% cell survival, respectively). In West Java, the boiled skin of salak cv. ‘bongkok’ is traditionally used to decrease blood glucose concentration for patients with diabetes mellitus (Pratama, 2009). The fruit of the salak cv. bongkok is known for being sour and bitter, so its economic value is low, but the use of this cultivar as a medicinal product can increase the income of farmers and at the same time conserve the genetic diversity of this fruit. The fruit are not only consumed as fresh fruit, but they are also processed into many food products, such as minimally processed fruit, fruit juice, deseeded-fruit in syrup, canned fruit, jam, fruit candy and pickle, ‘dodol’, chips or cracker and salak wine (Aralas et al., 2009; Gorinstein et al., 2009; Thangjatuporn, 2000). The young salak can be used to make a salad called ‘rujak’ in Indonesia.

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Fruit development and postharvest physiology

16.2.1

Fruit development respiration and ethylene production during maturation A few reports have been published on the postharvest physiology of salak (Dangcham, 1999; Lestari et al., 2004; Supriyadi et al., 2002; Wijaya et al., 2005). The fruit weight of a salak increases continuously during its development and maturation, which is a common phenomenon in fruit. The weight of salak flesh increases gradually during its maturation, whilst the seed size does not change during maturation (Supriyadi et al., 2002). It is not clear whether salak fruit is climacteric or non-climacteric. Dangcham (1999) reported that the respiratory rate of the Thai Sala fruit at 36 and 37 weeks after pollination increased continuously during storage. At 38 weeks after pollination the fruit showed a respiration peak at day 3 after storage and then it declined. The increase in respiration was concomitant with an increase in ethylene production, where the peak was found to be at day 4. These findings suggested that the salak fruit might be classified as a climacteric fruit; however a further investigation is required to confirm this hyphothesis.

16.3

Changes in quality components during maturation

A combination of the day after pollination and the changes in the concentration of soluble solids, acidity, astringency, odours, skin and seed colours are used as the index for harvesting salak. In Thailand, it is recommended that Sala and Rakam are harvested at 37–39 and 28–30 weeks after pollination, respectively (Dangcham, 1999; Thangjatupon, 2000). Supriyadi et al. (2002) suggested that the optimum stage for the consumption of salak was 5.5 months after pollination, when the flesh showed high firmness, sugar content and aroma compounds.

16.3.1 Skin and flesh colours Skin, flesh and seed colours are used as a maturity index for salak. Basically, salak are harvested when the skin colour has changed to blackish brown and seed colour has turned black or blackish brown (Sukewijaya et al., 2009). At immature stages, the flesh colour is white, then it changes to yellowish white when the fruit ripens (Supriyadi et al., 2002). Plate XXX in the colour section between pages 238 and 239 shows immature and mature Salak Pondoh fruit. In Thailand, the skin colour of Sala and Rakam is dark brown in the immature stages, and the colour changes to brownish orange or reddish brown as the maturation increases (Thangjatuporn, 2000), see Plate XXXI in the colour section. The flesh colour of the Thai Sala and Rakam are light yellowish-white in the immature stages, after which the flesh colour changes to creamy or yellowish orange with the increase in maturation (Dangcham, 1999; Thangjatuporn, 2000). The seed colour also changes from light brown in the immature stages to blackish brown or grey-brown when the fruit ripens (Thangjatuporn, 2000).

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16.3.2 Soluble solids concentration and titratable acidity The soluble solids concentration of the fruit increases continuously during maturation (Dangcham, 1999; Supriyadi et al., 2002). Supriyadi et al. (2002) reported that the Salak Pondoh became sweet when the fruit was 4.5 months after pollination. The glucose and fructose contents of the fruit increased during maturation, whereas the sucrose content increased until 5 months after pollination and then decreased. Similarly, the soluble solids concentration of Thai Sala fruit increased until 37 weeks after pollination and it then slightly declined at 38 weeks (Dangcham, 1999). The reduction of the sucrose content might be associated with the increase in glucose and fructose content during fruit development (Supriyadi et al., 2002), while titratable acidity in the fruit decreases during maturation (Dangcham, 1999; Surpriyadi, 2002; Thangjatuporn, 2000). Dangcham (1999) reported that the titratable acidity of the Thai Sala at 36 and 37 weeks after pollination was higher than that of the fruit at 38 weeks after pollination (Table 16.6).

Table 16.6 Firmness, soluble solids concentration and titratable acidity of Sala fruit during development Weeks after pollination

Firmness (N)

Soluble solids Titratable concentration acidity (°Brix) (%)

36 37 38

26.55 32.72 25.02

17.47 19.12 18.79

0.81 0.87 0.74

Modified from Dangcham (1999).

16.3.3 Firmness Texture is universally known as a very important factor in evaluating the quality of fruit. During maturation, the firmness of the salak increases and it then declines at the later stages of maturation (Dangcham, 1999; Supriyadi et al., 2002). It is widely accepted that the texture of the Salak Pondoh is firm and crunchy, while the texture of the Thai Sala and Rakam fruits is soft and juicy at full maturation stage. During maturation, the pulp firmness of the salak increased until fruit reached 5.5 months after pollination and by 6 months after pollination the firmness declined (Supriyadi et al., 2002). Similarly, the firmness of the Thai Sala fruit at 37 weeks after pollination was higher than that of the fruit at 36 weeks and the firmness then decreased in the fruit at 38 weeks (Table 16.6). Mahendra and Janes (1993) reported that salak stored at 22–24 °C showed an increase in firmness at day 7 and then decreased throughout storage (it is normally recognized that the loss of firmness during fruit ripening is concomitant with the modification of the cell wall structure). However, Lestari et al. (2004) reported that even though there was a marked increase in the ratio of soluble pectin to insoluble pectin of the salak during ripening, a slight change in the fruit firmness occurred.

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16.3.4 Volatile compounds Aroma is widely known as an important factor affecting the quality of salak and reports have shown that methyl esters of short-chain carboxylic acids are the major volatile compounds in salak (Supriyadi et al., 2002, 2003; Wijaya et al., 2005). The volatile aroma compounds are responsible for the sweaty and fruity character of the fruit (Supriyadi et al., 2002; Wijaya et al., 2005). During maturation, the level of esters and carboxylic acid in the salak increased markedly throughout storage. At the first stage of maturation, methyl dihydrojasmonate and isoeugenol were identified as the key volatile compounds in the fruit (Wijaya et al., 2005). Supriyadi et al. (2002) suggested that the unsaturated fatty acids in the salak were oxidized to yield methyl ester of short-chain carboxylic acids, of which the level of the compounds increased remarkably throughout maturation, especially in the fruit at 5 and 5.5 months after pollination. Moreover, Supriyadi et al. (2003) reported that the methyl ester formation in the salak during development was associated with the action of pectinmethylesterase providing methanol, which was transferred to Acyl-CoA. 16.3.5 Ascorbic acid content Salak has moderate ascorbic acid content (about 0.73–2.4 mg 100 g−1) (Aralas et al., 2009; Leong and Shui, 2002) and the change in the ascorbic acid content in the Thai Sala fruit during storage at various temperatures was reported by Dangcham (1999). Ascorbic acid content in the Thai Sala was about 5.17–5.85 mg 100 g−1 and, compared to the salak, the Thai Sala has higher ascorbic acid content. During storage, the ascorbic acid content of the Thai Sala declined remarkably and storage at lower temperatures could delay the reduction of the ascorbic acid content during storage (Dangcham, 1999).

16.4

Preharvest factors affecting fruit quality

Water and sunlight are environmental factors affecting the growth rate of the salak palm, as well as its pollination and fruit quality. The palm requires about 50–70% of full sunshine and an average rainfall of about 200–400 mm month−1, or not less than 1500 mm year−1 (Sukewijaya et al., 2009; Thangjatuporn, 2000). Thangjatuporn (2000) suggested that the Thai Sala palm requires a good irrigation system, especially during pollination, as water deficiency causes the fruit to drop from the bunch during development, producing an undesirably low quality of the fruit.

16.5

Postharvest factors and physiological disorders affecting fruit quality

Storage temperature is widely recognized as a key factor affecting the quality of perishable crops, including the salak. Dangcham (1999) reported that the shelf life

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of the Thai Sala stored at room temperature (30 °C) was lower than that of the same fruit stored at cold temperatures (Dangcham, 1999; Mahendra and Janes, 1993). The storage at high temperature and low relative humidity results in dried skin, dark brown or brownish black skin colour, soft and brown flesh and an increasingly astringent taste (Dangcham, 1999). Moreover, high temperature increases the rate of fruit drop from the bunch during storage (Dangcham, 1999; Thangjatuporn, 2000). Even though cold storage is recommended to extend the shelf life and quality of the salak, chilling injury during storage must be considered. It is universally accepted that chilling injury is a normal physiological disorder of tropical and subtropical fruit stored at low temperature. The most common symptom of chilling injury occurring in the salak is skin pitting and dark or brownish black skin colour, and the pulp turning brown and soft (Dangcham, 1999; Mahendra and Janes, 1993). Mahendra and Janes (1993) suggested that the chilling injury symptoms of the salak stored at 3–5 °C exhibited after two days, while the chilling injury of the Thai Sala stored at 10 and 12 °C appeared at seven and 14 days, respectively. The symptoms became more severe with increasing storage time. It is recommended that the fruit is stored at a temperature above 15 °C to prevent chilling injury (Dangcham, 1999; Thangjatuporn, 2000). Mahendra and Janes (1993) reported that no chilling injury symptoms occurred on a salak stored at 15 °C. Exogenous ethylene from the environment causes fruit to drop during storage. Dangcham (1999) reported that the percentage of fruit drop increased with the increase of ethephon concentration and that exogenous ethylene had an effect on the decrease in titratable acidity of the Thai Sala during storage, resulting in the increase in sugar acid ratio. Table 16.7 shows the effect of exogenous ethylene on fruit drop and certain qualities in the Thai Sala. Table 16.7 The percentage of fruit drop and quality of Sala fruit treated with ethephon stored for three days Ethephon (mg L−1) Percentage of fruit drop

Soluble solids concentration, SSC (°Brix)

Titratable acidity, SSC/TA TA (%)

0 500 1,000

19.10 17.52 18.04

0.79 0.47 0.59

17.11 95.36 100

24.18 37.81 31.30

Modified from Dangcham (1999).

16.6

Postharvest pathology and entomology

Fungi that attack the salak include Fusarium sp., Aspergillus sp. and Certocystis paradoxa (Sukewijaya et al., 2009), while Marasmius palmivorus and Thielaviopsis paradoxa attack the Thai Sala and Rakam (Thangjatuporn, 2000). The disease spreads rapidly in the rainy season and infects immature fruit on the

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tree. The following are common symptoms caused by the fungi in mature fruit: a brownish-black or black, water-soaked area covered with white or pinkish-white mycelium forms on the skin and water-soaked on flesh, and the skin becomes very dry and hard, which causes problems in peeling (Thangjatuporn, 2000). Arbie (2010) had tested the effect of alpinia galangal rhizome as a natural antimicrobe on Salak Pondoh stored in a perforated polyethylene plastic bag sized 25 cm × 16 cm with a thickness of 40 μm. The result showed that immersion in 5% alpinia galangal extract for 30 s and storage at 15 °C (85–90% relative humidity (RH)) could extend the shelf life of the Salak Pondoh for 21 days, as compared to 14 days in control. Good agricultural practices, fruit thinning, orchard hygiene, weed and undesired plant management are required to prevent the spread of the disease in the orchard. Fungicides such as thiabendazol and caboxin are also being used to control the disease. Normally, the fungicide is sprayed before the rainy season and the spraying of the fungicide is stopped about 15 days before harvest (Thangjatuporn, 2000). Pests such as sugarcane white grub (Lepidiota stigma (Fabricius)) and Salacca beetle (Rhynchophorus ferrugineus) could affect the export of the Indonesian salak to China (Dimyati et al., 2008). In order to export the Salak Pondoh to China, The Indonesian Agriculture Quarantine Agency (IAQA) sent a list of pests to the Ministry of Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) of China. AQSIQ then sent a team of entomologists to verify the condition of Yogyakarta. After the verification, the Memorandum of Understanding between IAQA and AQSIQ was signed to declare that the exportation of the salak fruit from Indonesia was permitted. Thus, good agricultural practice is crucial in exporting the salak.

16.7

Postharvest handling practices

16.7.1 Harvesting, cleaning and grading Proper postharvest operations are important to maintain fruit quality and to avoid physical damages and diseases. It is recommended that salak fruit is harvested when the hairs on the skin surface disappear and the skin colour changes to blackish brown for the salak and to reddish-brown for the Thai Sala and Rakam; at maximum fruit size, seed colour turns to black or blackish-brown with a pleasant and aromatic taste (Sukewijaya et al., 2009; Thangjatuporn, 2000). The fruit is harvested using a sharp knife or scissors. The salaks are delivered to the packinghouse immediately after the harvest and the fruit are cleaned by spraying clean water or chlorinated water (50–100 ppm hypochloride) to remove soil, insects and undesired matter (Thangjatuporn, 2000). Salak fruit are classified as extra class, class I and class II. The extra class fruit must be of superior quality and free from defects with the exception of very slight superficial defects which do not affect the general appearance of the fruit. The class I fruit must be good quality and slight defects in shape, colour and skin should not exceed 5% of the total surface area. The quality of the fruit in class II

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satisfies the minimum requirements and the fruit may have defects in shape and colour, as well as skin defects, of which the total area of defect should not exceed 10% of the total surface area (Draft Asean Standard for Horticultural Produce, 2009). In Thailand, the Sala are classified into two classes for the domestic market which are class 1 (without physical damage and disease and no fruit drop from the bunch) and class 2 (with some physical damage and fruit drop from the bunch) (Thangjatuporn, 2000). 16.7.2 Ripening and senescence control The salak does not go through the ripening process as it is eaten when the fruit matures, but a few studies have been carried out to control senescence by prolonging storage life. Trisnawati and Rubijo (2010) conducted a study using fruits, either detached from or still attached with their bunch, wrapped using paper and placed in a braided bamboo basket for 15 days. They found that there was a significant decrease in the vitamin C, total acid, pH and soluble solids concentration as storage duration progressed. In another study, the storage life of Salak Bali fruit coated with 10% beeswax and stored in a bamboo basket at 22–26 °C and 70–75% relative humidity could be extended from seven to 12 days, while qualities of the fruit such as vitamin C, tannin content, organic acids and the pH of the fruit could be retained (Wrasiatil et al., 2001). Water loss or weight loss, and sugar degradation were inhibited, but microbiological decay and loss of firmness or texture still occurred even though the Salak Bali was coated with beeswax. The astringent taste of the salak may cause an unpalatable sensation to new consumers. The tannin content of the Salak Bali cv ‘Nangka’ can be significantly reduced by applying 25, 50 and 75% ethanol, both in solution and vapour, in a plastic bag with a volume of 5 L for 24 h (Utama et al., 2009). The efficiency of ethanol in removing the astringent taste is concentration dependent, with high ethanol concentration effective in short period of time and vice versa. In addition to this, soluble solids concentration increased while acidity decreased by treating the salak with ethanol. 16.7.3 Storage In Thailand, it is recommended that Sala and Rakam fruits are stored at 15 °C (Dangcham, 1999; Thangjatuporn, 2000). Dangcham (1999) suggested that the shelf life of Sala fruit stored at 15 °C could last 28 days without chilling injury, while the fruit stored at 12.5 °C showed slight chilling injury symptoms after 14 days of storage. Mahendra and Janes (1993) reported that the shelf life of salak fruit stored at 3–5 and 7–10 °C would last 15 days, which was longer than that of the fruit stored at 15 °C; however, temperatures of 3–5 and 7–10 °C could cause moderate to severe chilling injury. In Indonesia, waxing and wrapping the salak cv ‘Suwaru’ using perforated polyethylene plastic film and placing it either in a cardboard box or a bamboo basket at 15 °C could prolong the fruit shelf life for three weeks (Hubeis et al.,

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1995). Even after 23 days of storage the fruit retained fairly good nutrient values, with a 20% deterioration level and 2.04% weight loss as compared to day 0.

16.8

Processing

16.8.1 Fresh-cut processing Increasing working activities and salaries affect citizens’ preferences, where consumers tend to prefer ready-to-eat fresh fruit or minimally processed fresh fruit. The salak fruit is one of the potential horticultural products for this kind of industry. Coating fresh-cut salak fruit using 1.05% kappa-carrageenan and 0.15% carboxymethylcellulose (CMC) could extend its shelf life by three days as compared to control (Niam, 2009). The processed fresh-peeled fruit could be stored for up to 15 days in 10 °C and 87% RH and up to 9 days in 22 °C and 65% RH. An organoleptic test showed that the panelist could accept the colour, texture, flavour, and taste of fresh cut fruit stored at day 12 in 10 °C and day 6 in 22 °C. Another study using edible film made of a soya protein isolate and fatty acid showed that the combination of 0.5% soya protein isolate and 0.5% strearatpalmitat gave the lowest water vapour transmission rate to fresh-cut salak fruit (Widyasari, 2000). As a result of these coatings, the shelf life of fresh-peeled Salak Pondoh fruit could be prolonged by up to 10 days at 5 °C compared to only two days at room temperature. 16.8.2 Other processing practices A number of value-added products are produced from the salak in Indonesia. During the peak season, fruit is processed in order to overcome a surplus of salak production. Processed fruit products include wine, pickle, dried fruit, juices, candy, dodol, chips or crackers and jam (Palupi et al., 2009). Most of these products are processed on the scale of home industry, although some are in middle class industry, such as the production of chips by farmers in the Sleman Regency of Yogyakarta using a vacuum frying technology. The advantage of the vacuum frying technique was that it resulted in there being little change in the texture, flavour and colour of fruit due to the lower temperature used (85–90 °C) compared to frying under atmospheric conditions that leads to the boiling of the oil at 180–200 °C. Sanjaya (2007) found that the spinner rotation time during the process of de-oiling in vacuum frying technology also played an important role in the rancidity of salak chips obtained and therefore affected their shelf life. The longer (90 as compared to 60 and 30 s) spinner rotation time during de-oiling resulted in the shelf life decreasing. This may be caused by crispy chips absorbing greater amounts of water from their surroundings, so their rancidity hydrolize process is activated sooner. The longer the spinner process, the longer the chips are in contact with metal, which would serve as a catalyst for rancidity. By also comparing the type of packages, the study showed

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that the shelf life of salak chips obtained by using 30 s rotation time during de-oiling was 107, 95 and 81 days, respectively, by using alumium foil and oriented polypropylene packages. The quality of salak juice was studied by adding pectin and CMC in different concentrations of water (Christandy, 1999) and the result showed that the titrable acidity of the juice increased from 10.7 to 13.5% during storage, while the pH decreased from 4.26 to 4.10. The viscosity of the juice also increased from 0.43 to 0.57 cp. An organoleptic test showed that the panelist prefered the salak juice prepared by addition of 0.45% pectin, 0.45% CMC and two volumes of water. According to the microbiological standard, the juice became unconsumable six weeks after storage at room temperature. The panelist could accept the product after four weeks of storage with organoleptic scores as follows: taste (3.1), colour (2.9) and smell/flavour (3.7).

16.9

Conclusions

The Indo-Malaysian region is very rich in salak germplasm, where traditionally the fruit had been grown for more than 150 years in these countries. However, economically it was still considered to be a minor fruit. With the demand from China, Europe and United States, salak fruit became an important commercial fruit in the Indo-Malaysian region, especially in Indonesia and Thailand. However, there is little information on postharvest technology for the fruit. More studies are needed in order to achieve a better understanding of the postharvest biology and physiology and to develop postharvest technology for this unique fruit.

16.10

References

Abu Bakar H and Idris S (2006), Salak, Selangor, Malaysia, Dawama Sdn Bhd. Aralas S, Mohamed M and Bakar M F A (2009), ‘Antioxidant properties of selected salak (Salacca zalacca) varieties in Sabah, Malaysia’, Nutr Food Sci, 39, 243–250. Arbie A (2010), The effect of extract alpine galangal (Alpinia galanga L. Swartz) to extend the shelf life of Pondoh salacca fruit (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Institut Pertanian Bogor, Bogor, Indonesia. Christandy H (1999), The effect of water, pectin and CMC addition on the quality of bottled salacca juice during storage at room temperature (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Universitas Juanda, Bogor, Indonesia. Dangcham S (1999), Quality variation, storage and effect of ethephon on abscission of Sala fruit, Master Special Problem, Kasetsart University, Thailand. Department of Agricultural Extension (2008), Agricultural Extension Information Center, Department of Agricultural Extension, the Royal Thai Government. In Thai. Available from http://www.aggriinfo.doae.go.th (accessed 16 February 2010). Dimyati A, Suntarsih S, Iswari D and Nurcahya S (2008), ‘Meeting the requirements of international market for salacca (case study: export challenge of salacca “pondoh” variety to China)’, Directorate General of Horticulture, Ministry of Agriculture of the Republic of Indonesia, 1–17.

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Draft ASEAN Standard for Horticultural Produce (2009), ‘Draft Asean Standard for Salacca’, in 5th Meeting of the Task Force on the ASEAN Standard for Horticultural Produce, 14–16 April, Puerto Princesa City, Palawan, Philippines. Gorinstein S, Haruenkit R, Poovarodom S, Park Y, Vearasilp S, et al. (2009), ‘The comparative characteristics of snake and kiwi fruits’, Food Chem Toxicol, 47, 1884– 1891. Haruenkit R, Poovarodom S, Leontowicz H, Leontowicz M, et al. (2007), ‘Comparative study of health properties and nutritional value of durian, mangosteen and snake fruit: experiments in vitro and in vivo’, J Agri Food Chem, 55, 5842–5849. Hubeis M, Sjaifullah and Rulianto A (1995), ‘The effect of packaging treatments on maintaining quality of salak cv. Suwaru during storage (in Indonesian),’ Bul.Tek. Industri Pangan VI(2), 27–34. Kueh H O (2003), Indigenous fruits of Sarawak, Sarawak Forest Department, Sarawak, Lee Ming Press Sdn Bhd, 133–134. Leong L P and Shui G (2002), ‘An investigation of antioxidant capacity of fruit in Singapore markets’, Food Chem, 76, 69–75. Lestari R and Ebert G (2002), ‘Salak (Salacca zalacca (Gaertner.) Voss.) – The snakefruit from Indonesia preliminary results of an ecophysiological study’, in conference on International Research on Food Security Natural Resource Management and Rural Development, Deutcher Tropentag 9–11 October, Witzenhausen, Germany. Lestari D I (2003), The effect of different packaging and storage temperature to the quality of salak Wedi (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Institut Pertanian Bogor, Bogor, Indonesia. Lestari R, Keil H and Ebert G (2004), Physiological changes of Salak fruit [Salacca zalacca (Gaertn.) Voss.] during maturation and ripening. Available from http://oek.fbl. fh-wiesbaden.de/dgg-neu/fileadmin/poster-2004/O21.pdf (accessed 16 February 2010). Lim Y Y, Lim T T and Tee J J (2007), ‘Antioxidant properties of several tropical fruits a comparative study’, Food Chem, 103, 1003–1008. Lin S, Fuji M and Huo D (2008), ‘Molecular mechanism of apoptosis induced schizandraederived lignans in human leukemic HL-60 cells’, Food Chem Toxicol, 46, 590–597. Mahendra M S and Janes J (1993), ‘Incidence of chilling injury in Salacca zalacca’, in proceedings of Postharvest Handling of Tropical Fruit – an International Conference, 19–23 July, Chiang Mai, Thai, ACIAR Proceedings No. 50, 402–404. Mogea J P (1982), ‘Salacca zalacca, the correct name for the salak palm’, Principes, 26(2), 70–72. Niam R K (2009), Kappa-carrageenan based edible coating application by addition of CMC to extend shelf life of salacca fruit (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Institut Pertanian Bogor, Bogor, Indonesia. Palupi S, Hamidah S and Purwanti S (2009), ‘Productivity increase of salak processed by secondary diversification to support the development of Agropolitan region (in Indonesian)’, Jurnal Inotek, 13(1), 97–11. Pratama N R (2009), Activity of antihyperglycemic exocarp and mesocarp extract from snake fruit cv. ‘bongkok’ (in Indonesian), Master Thesis, Fakultas MIPA, Institut Pertanian Bogor, Bogor, Indonesia. Rangsiruji A, Pongpawe T and Donsakul T (2006), ‘Karyotypes of some Salacca in Thailand and Indonesia’, Srinakarinwirot Uni Sci J, 22, 48–61. Sanjaya Y (2007), The effect of rotation time on zalacca crispy chips production against estimating shelf life by using packages of orientedpolypropylene (OPP), metalized (Co-PP/Me) and alumunium foil (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Institut Pertanian Bogor, Bogor, Indonesia. Supriyadi S, Suhardi M, Suzuki M, Yoshida K, Muto T, et al. (2002), ‘Changes in the volatile compounds and in the chemical and physical properties of snake fruit (Salacca edulis Reinw) cv. Pondoh during maturation’, J Agri Food Chem, 50, 7627–7633.

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Supriyadi S, Suzuki M, Wu S, Tomita N, Fujita A and Watanabe N (2003), ‘Biogenesis of volatile methyl esters in snake fruit (Salacca edulis, Reinw) cv. Pondoh’, Biosci Biotechnol Biochem, 67, 1267–1271. Sukewijaya I M, Rai I N and Mahendra M S (2009), ‘Development of salak Bali as an organic fruit,’ Asian J Food Agro-Industry, Special Issue, S37–S43. Surh Y J, Hurh Y J, Kang J Y, Lee E, Su G K and Lee J (1999), ‘Resveratrol antioxidant present in red wine induces apoptosis in human promyelocytic leukemia (HL-60) cells’, Cancer Letter, 140, 1–10. Thangjatuporn S (2000), Sala and Sweet Rakam, Bangkok, Thailand, Naka Press. Trisnawati W and Rubiyo (2010), ‘The effect of packaging and duration of storage to the quality of salak Bali’ (in Indonesian), Balai Pengkajian Teknologi Pertanian, Denpasar, Bali. Utama I M S, Bagus I, Gunadnya P and Wrasiati L P (2009), The effect of ethanol on concentration of tanin, total soluble solid and total acid of the fresh salak fruit (in Indonesian), Master Thesis, Faculty of Agricultural Technology, Udayana University. Widyasari R R L E A (2000), Application of edible film made of soya protein isolate and fatty acid to preserve salak pondoh (in Indonesian), Master Thesis, Fakultas Teknologi Pertanian, Institut Pertanian Bogor, Bogor, Indonesia. Wijaya C H, Ulrich D, Lestari R, Schippel K and Ebert G (2005), ‘Identification of potent odorants in different cultivars of snake fruit [Salacca zalacca (Gaert.) Voss] using gas chromatography-olfactometry’, J Agri Food Chem, 53, 1637–1641. Wrasiatil L P, Sutardi and Darmadji P (2001), ‘Beeswax coating to maintain quality of snake fruit of Bali’, Mediagama III(2), (in Indonesian).

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Plate XXIX

(Chapter 15) Panicles of mature rambutan fruit.

(a)

Plate XXX

(b)

(Chapter 16) Mature (a) and immature (b) Salak Pondoh.

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Plate XXXI

(Chapter 16) Mature (a) and immature (b) Rakam.

(a) (b)

(c)

Plate XXXII

(Chapter 17) Sapodilla tree and fruit.

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17 Sapodilla (Manilkara achras (Mill) Fosb., syn Achras sapota L.) E. M. Yahia and F. Gutierrez-Orozco, Autonomous University of Queretaro, Mexico

Abstract: Sapodilla is a climacteric, chilling-sensitive fruit and the use of modified atmospheres and other methods of preservation are required for long-term storage and shipping. Some of the research needs for this fruit include the development of adequate maturity and harvesting indices. This chapter discusses the important physiological and handling aspects of the fruit. Key words: Manilkara achras, sapodilla, postharvest, nutrition, diseases, insects, processing, respiration, ethylene.

17.1

Introduction

The sapodilla tree (Manilkara achras (Mill) Fosb., syn Achras sapota, L.) (see Plate XXXII(A) in the colour section between pages 238 and 239) is native to Mexico and Central America and has been introduced to many tropical areas of the world. Cultivated in the past mostly for its latex, called chicle, to make chewing gum, the sapodilla tree is now mainly cultivated for its fruit. Sapodilla fruit present a climacteric behavior and need special handling postharvest to prevent losses and to maintain quality (Yahia, 2004). Optimal harvesting time is the key for keeping quality of the fruit at ripeness. Fruit at different development stages are commonly present in a single tree which makes it difficult to establish a general maturity index. Compared to some other minor tropical fruits, sapodillas have been the subject of more extensive research on ways to extend their storage life and keeping quality. 17.1.1 Origin, botany, morphology and structure The sapodilla is also known as sapota, chiku, ciku, dilly, nasberry, sapodilla plum, chico zapote, zapote, chico, níspero, and sapota plum. It is native to Mexico (specifically the Yucatan Peninsula), Central and South America (Mickelbart,

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1996) and has been introduced throughout tropical America, the West Indies, the Bahamas, Bermuda, the Florida Keys and the southern part of the Florida Mainland, and the Philippines (Morton, 1987). The tree is evergreen with an extensive root system, it reaches a height of more than 30 m and a diameter of up to 1.5 m (Orwa et al., 2009). The canopy is dense, generally with a rounded crown, ovate-elliptic to elliptic-lanceolate leaves, which are glossy and dark green and clustered at the tips of the branches (Mickelbart, 1996). The fruit is a fleshy berry, ellipsoidal, conical or oval, and contains one or several shiny black seeds. Its weight is about 70 to 300 g and its size ranges from 5 to 9 cm in diameter. Immature fruit are hard, gummy and very astringent (Morton, 1987). It has a dull brown color and thin skin and yellowish, light brown or red pulp with a grainy texture, and is prized for its pleasant aroma and sweet flavor once the fruit is ripe. 17.1.2 Worldwide importance and economic value The white latex extracted from the sapodilla tree was traditionally the main ingredient of chewing gum. Countries like Mexico, Venezuela and Guatemala still use it to produce chicle, however, sapodilla is currently cultivated mainly for its fruit in areas such as India, the Philippines, Sri Lanka, Malaysia, Guatemala, Mexico and Venezuela, among others (Mickelbart, 1996). India is one of the largest producers of sapodilla in the world with a cultivated area of around 24 000 ha (Chadha, 1992). Although the sapodilla fruit is not commonly seen in US markets, it is becoming popular as an exotic fruit in some restaurants (Mickelbart, 1996). 17.1.3 Culinary and other uses, nutritional value and health benefits Sapodilla fruit (see Plate XXXII (B and C) in the colour section) is mainly consumed fresh as a dessert due to its pleasant sweet flavor and aroma. Sometimes the fruit is chilled prior to eating which improves its flavor. The flesh is sometimes used to make sherbets, ice cream or is eaten as dried fruit in India (Mickelbart, 1996). Some people make syrup and vinegar from the sapodilla juice and jams from the flesh (Garcia, 1988). As mentioned above, for many years, the latex from the sapodilla tree called ‘chicle’ was the main ingredient of chewing gum. It contains 15% rubber and 38% resin and is tasteless. Steps to process the latex into chewing gum include drying, melting, elimination of foreign matter, mixing with other gums, sweeteners and flavors, and finally rolling into sheets and cutting into different sizes (Morton, 1987). Chicle has been increasingly substituted by synthetic gums, although countries like Mexico, Guatemala and Belize still use natural chicle. The wood from the sapodilla tree is dark red, hard, heavy and durable and has been used for railway cross-ties, flooring, tool handles, etc. The sapodilla red heartwood is also valued for furniture, banisters, and cabinetwork (Morton, 1987; Garcia, 1998). The tree is grown as an ornament in some areas although its height may become a problem in some gardens. According to the food composition database from the USDA, the nutrient value of sapodilla fruit is shown in Table 17.1.

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Table 17.1 Nutrient value of sapodilla fruit (100 g of fruit) Constituent

Approximate value

Water content Calories Protein Fat Cholesterol Carbohydrate Total dietary fiber Calcium Iron Magnesium Phosphorus Potassium Sodium Vitamin C Vitamin A

78% 83 0.4 g 1.1 g 0 mg 20.0 g 5.3 g 21 mg 0.8 mg 12.0 mg 12.0 mg 193.0 mg 12.0 mg 14.7 mg 60 IU

Source: USDA National Nutrient Database for Standard Reference, Release 22 (2009) (website: http://www.nal. usda.gov/fnic/foodcomp/).

Several medicinal properties have been ascribed to different parts of the sapodilla tree. For instance, the tannins in young fruit are used to stop diarrhea, tea is made from the young fruit and the flowers are used for pulmonary problems. Tea from old leaves is used to treat coughs, colds and diarrhea, crushed seeds are used as a diuretic, sedative, sopoforic and for kidney stones; the latex can be used to fill tooth cavities temporarily; and the bark can be used to make tea for treating fevers (Morton, 1987).

17.2

Fruit development and postharvest physiology

17.2.1 Fruit growth, development and maturation The development of the sapodilla fruit is characterized by a single sigmoidal pattern (Sulladmath et al., 1979; Abdul-Karim et al., 1987). Three stages can be identified during fruit growth: the first, where cell division and maturation of the embryo occur; second, where growth is greatly reduced; and third, where cell enlargement occurs giving rise to another phase of rapid and maximum growth. This phase occurs between 5 and 7.5 months from fruit set (Lakshminarayana and Subramanyam, 1966). Carbohydrates and tannins are the main constituents of sapodilla fruit. Free sugars are in high concentration in the mature fruit, while starch is almost absent (Lakshminarayana and Subramanyam, 1966; Lakshminarayana, 1980; Selvaraj and Pal, 1984; Roy and Joshi, 1997). The immature fruit is hard, with a high concentration of latex and tannins and the latter are responsible for the high astringency of immature fruits. The skin of the

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fruit has a sandy brown texture that disappears once fully ripe. The flesh becomes soft and very juicy while the sugar content increases with maturity giving the fruit a sweet flavor that resembles that of a pear (Mickelbart, 1996). Sugar content greatly increases in particular during the last growth phase when fruit harvested at this stage have a higher quality, are soft and have a sweet aroma. The fruit can also be harvested after the first growth stage. It can take 4–10 months for the fruit to be fully ripe depending on the variety, climate, and type of soil (Mickelbart, 1996). 17.2.2 Respiration, ethylene production and ripening Sapodilla is a climacteric fruit (Yahia, 2004) and can be picked from the tree both when fully mature and before it is ripe (Broughton and Wong 1979; Selvaraj and Pal 1984; Abdul-Karim et al., 1987; Brown and Wong 1987; Yahia, 2004). The fruit requires very special postharvest handling attention to reduce losses (Sastry 1966a, 1966b; Joshi and Paralkar, 1991; Joshi and Sawant, 1991; Yahia, 2004). Its respiration rate at 24–28 °C was 16 mg CO2 kg−1 hr−1. Preharvest spraying with isopropyl n-phenylcarbamate (IPC) at 100 ppm retarded the respiration rate, while maleic hydrazide at 500–1000 ppm accelerated it (Lakshminarayana and Subramanyam, 1966). For the cv. ‘Kalipatti’ the climacteric peak was seen on the fifth day after harvest (Rao and Chundwat, 1988). However, Selvaraj and Pal (1984) found a reduction in the respiration rate two days after harvest followed by an increase on the third day. An additional reduction was observed on the sixth day for the ‘Oblong’ cultivar and on day eight for ‘Cricket ball’. When the fruit is harvested at the appropriate maturity stage, it ripens in 5–7 days at ambient temperature, but fruit harvested before the optimum stage will have a poor quality when ripe. On the contrary, fruit harvested later than the optimum maturity stage will have a shorter postharvest life (Roy and Joshi, 1997). Ethylene production was 3 nmoles gfw−1 day−1 at 15 °C, and 6.5 at 25 °C (Broughton and Wong, 1979). Treatment of sapodilla fruit with etherel at 1000–3000 ppm accelerated ripening, reduced pectins, phenolic contents, total soluble solids, sugars, and vitamin C (Shanmugavelu et al., 1971; Das and Mahapatra, 1976; Ingle et al., 1982), while removal of ethylene was reported to delay ripening by 23 days (Chundawat, 1991). Roy and Joshi (1997) reported an increase in ethylene production during ripening that peaked after 144 hours, followed by a decline.

17.3

Maturity and quality components and indices

It takes from 120 (Purseglove, 1968) to 245 (Sulladmath et al., 1979) days from fruit set to maturity depending on the climate and cultivar. However, the erratic flowering habit of sapodilla, and the presence of fruit at all stages of development on the tree makes it difficult to determine the optimum harvesting time of the fruit. Visual signs of physiological maturity include shedding of the brown scaly external material which gives the peel a smooth texture (Lakshminarayana, 1980) and fruit with a smooth surface, shining brown potato color and rounded styler end are

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considered mature (Kute and Shete, 1995). In addition, fruit ready for harvest will not show a green tissue or latex when scratched with the fingernail and the fruit will separate easily from the stem without leaking latex. This is because the latex content of mature fruit is reduced to almost zero (Sulladmath and Reddy, 1990). Other maturity indices have been proposed for sapodilla. For instance, Sundararajan and Rao (1967) suggested using total soluble solids while others have found that fruit size (length and width) are better indices of maturity (Abdul-Karim et al., 1987). Flesh-to-peel ratio increases during ripening (Pathak and Bhat, 1953) and flesh sugar concentration ranges from 12 to 14%. Sucrose presents the greatest increase during ripening, followed by glucose and fructose (Lakshminarayana and Subramanyam, 1966), however when the fruit is overripe, the sucrose content is lower than glucose and fructose. Total and reducing sugars also increase during ripening reaching up to 16.7 and 26.0%, respectively, when the fruit is ready to eat (Lakshminarayana and Subramanyam, 1967). The concentrations of alcoholinsoluble solids and starch decrease during ripening in cvs. ‘Cricket Ball’ and ‘Oblong’ (Selvaraj and Pal, 1984). Flavor quality depends on the soluble solids content (13–26%) and acidity (0.2–0.3%) (Kader, 2009). Total soluble solids (TSS) increase during ripening and Shende (1993) found that for the cultivar ‘Kalipatti’, TSS ranged between 23.80 and 24.16 °Brix when the fruit was fully ripe, but declined steadily towards the end of the shelf life. Titratable acidity goes from a high concentration (0.48–1.36%) in the early stages of fruit development to a very low level (0.11–0.41%) when the fruit is fully ripe (Lakshminarayana and Subramanyam, 1967). This reduction in acidity during ripening and storage of sapodilla fruit is irrespective of the variety (Suryanarayana and Goud, 1984; Shende, 1993). Ascorbic acid content in sapodilla fruit decreases during ripening. For instance, Lakshminarayana and Subramanyam (1966) report that ascorbic acid went from 27.2 to 3.2 mg 100 g−1 fresh weight in mature and fully ripe sapodilla, respectively. Selvaraj and Pal (1984) found that not only vitamin C but also vitamin A decrease with ripeness. Reports on the content of pectin in fruit of sapodilla indicate levels from 0.5 to 3.9% with a decline during storage (Shanmugavelu and Srinivasan, 1973; Das and Mahapatra, 1976; Shende, 1993). Polyphenols, the main compounds responsible for the astringency in immature fruit, were found to decrease during fruit ripening and this change was independent of the storage condition (Paralkar, 1985; Sawant, 1989). Lakshminarayana and Subramanyam (1966) reported a reduction from 2.4% at harvest to 1.8% at ripeness. The content of minerals such as calcium, potassium, phosphorus, iron and manganese was found to decline during ripening, while zinc and copper contents increased (Selvaraj and Pal, 1984; Paralkar, 1985). The protein content at the eating-ripe stage has been reported to vary from 0.52 to 0.76%. Proteins and soluble amino acids decrease during ripening as well as the activity of several enzymes such as amylase, invertase, inulase and phosphatase (Salvaraj and Pal, 1984). On the other hand, enzymes such as catalase, pectinesterase, peroxidase, polyphenoloxidase and adenosintriphosphatase increased their activities (Rao and Chundawat, 1988).

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The moisture content of the sapodilla fruit at maturity ranges from 69 to 80% depending on the climate conditions and variety (Lakshminarayana et al., 1967, Lakshminarayana and Rivera, 1979; Thapa, 1980). According to Morton (1987), the seed kernel, which makes up 50% of the whole seed, contains 1% saponin and 0.08% of a bitter compound, sapotinin. Morton considers that abdominal pain and vomiting are likely if more than six seeds are consumed.

17.4

Preharvest factors affecting fruit quality

Fruit harvested later than optimum time usually soften very rapidly and become very difficult to handle. Fruit harvested earlier than physiological maturity may not soften, contain pockets of coagulated latex that lower the quality of the fruit and are usually low in sweetness and high in astringency when ripe, with a rather unappealing alcoholic aftertaste. Unripe fruit are highly astringent and contain large amounts of leucoanthocyanidins (Mickelbart, 1996).

17.5

Postharvest handling factors affecting quality

17.5.1 Temperature management Optimum storage temperature is 14 °C ± 1 °C and 90–95% relative humidity according to Kader (2009) and Yahia (2004). Under these conditions sapodilla fruit can be kept for 2–4 weeks (Yahia, 2004). Lower temperatures can cause chilling injury which lowers fruit quality, producing poor flavor, shriveling, wrinkling, dark-brown spots on the peel and failure to ripen (Broughton and Wong, 1979; Salunkhe and Desai, 1984; Morton, 1987; Yahia, 2004). Therefore, temperatures from 15 to 20 °C are suggested to be used if longer periods of storage are required (Morton, 1987). Short-term holding of fruit for less than 10 hours at 4 °C before storage at 20 °C was reported to extend the storage life of the fruit for up to 24 days with satisfactory quality (Broughton and Wong, 1979). 17.5.2 Physical damage Fruit harvested after the optimum stage of maturity very quickly becomes soft and more prone to physical damage. Therefore it is very important to identify optimum harvesting indices and harvest the fruit at the ideal stage (Yahia, 2004). 17.5.3 Water loss High temperatures increase fruit water loss (Yahia, 2004), and low temperatures (4 °C) cause chilling injury, which can result in shriveling and wrinkling (Morton, 1987; Yahia, 2004).

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17.5.4 Atmosphere Storage life of sapodilla is extended by the use of modified atmospheres and removal of ethylene (Broughton and Wong, 1979; Yahia, 1998). Storage of sapodilla under high CO2 concentrations (but less than 20%), and low ethylene concentrations prolonged the storage life of the fruits (Brown and Wong, 1987). Shelf life at room temperature increased from 13 to 18 days when 5% CO2 was added to the atmosphere, to 21 days when 10% CO2 was added, and to 29 days when 20% CO2 was added. However, the latter fruit failed to ripen. A concentration of 20% CO2 is found to be deleterious. ‘Kalipatti’ fruit treated with 6% Waxol or 250 or 500 ppm Bavistin, or hot water (50 °C for 10 min), and wrapped in 150 gauge polyethylene film with 1% ventilation, ripened later than those of the control, but fungal rot was high (Bojappa and Reddy, 1990). Fruit treated with 6% wax emulsion and packed in 200-guage polyethylene covers containing ethylene and CO2 absorbents were reported having a shelf life of 45 days at 12 °C, 10 days later than the control (Chundawat, 1991). ‘Jantuang’ fruit were stored in modified atmosphere packaging (MAP) for four weeks at 10 °C or for three weeks at 15 °C, one week longer than fruit without MAP (Mohamed et al., 1996).

17.6

Physiological disorders

17.6.1 Chilling injury Sapodilla fruit is highly susceptible to chilling injury (CI) (Yahia, 2004). Symptoms include poor taste and flavor, dark-brown spots on the peel, failure to ripen, and increased deterioration after storage at higher temperatures. Storage of fruit at temperature of 6–10 °C causes irreversible damage and produces fruit with poor taste and flavor (Broughton and Wong, 1979; Salunkhe and Desai, 1984). CI also occurred in fruit stored for 21 days at 10 °C. However, fruit which have been waxed with a fatty acid sucrose ester (using a dip containing 5–10 g L−1 ‘sempefresh’ or 250 g L−1 ‘sta-fresh’) were reported to be kept for 40 days at 10 °C (Yahia, 2004). Kader (2009) reports chilling injury after exposure to temperatures lower than 5 °C for more than ten days.

17.7

Pathological disorders

Some of the factors that contribute to the development of postharvest diseases in sapodilla fruit are their high moisture and nutrient content. If the fruit on the lower branches of the tree come into contact with water in areas with high temperatures and relative humidity, symptoms of fruit rot may appear as a result of Phytophthora palmivora (Butler) infection (Balasubramanian et al., 1988). Some other common disorders include sour rot (Geotrichum candidum), Cladosporum rot (Cladosporum oxysporium), and blue mold rot (Penicillium italicum) (Mickelbart, 1996). Other species of Pestalotiopsis and Phomopsis can also cause fruit rot. Some species of bacteria are associated with fruit latex (Pathak and Bhat, 1952). Kader (2009)

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reported that anthracnose caused by Colletotrichum gloeosporioides can be a serious problem in areas with high relative humidity. Bakar and Abdul-Karim (1994) reported benlate (methyl-N-1-butylcarbomoyl) as a good control for fungal and bacterial pathogens in sapodilla fruit.

17.8

Insect pests and their control

Some of the most important pests that infest sapodilla fruit are the Mediterranean fruit fly (Ceratitis capitata) and the Mexican fruit fly (Anastrepha ludens). Larvae of Trypetidae, which infest the ripe fruit, can be a major problem in some areas (Orwa et al., 2009). Another insect known to attack the sapodilla fruit is Nephopteryx engraphella Rag. (Kute and Shete, 1995). Leaf miner and stem borer do not constitute a major problem in sapodilla fruits (Balasubramanian et al., 1988; Yahia, 2004).

17.9

Postharvest handling practices

17.9.1 Harvest operations Ladders and baskets may be used during harvest and the peduncle is cut with a knife or scissors. Selection can be based on size and maturity of the fruits. Any fruit presenting deterioration or mechanical injury are discarded (Polania, 1986; Yahia, 2004). 17.9.2 Packinghouse practices The fruit is commonly cell packed in fiberboard or wood flats, 25–49 counts, 4.5 kg capacity (McGregor, 1987). Fruit weight should not exceed 20 kg per box to avoid injuries (Polania, 1986). 17.9.3 Control of ripening and senescence Both wax coating and 2,4-dichloro-phenoxy acetic acid (2,4-D) have been shown to retard the ripening process in sapodilla fruit, while 2-chloroethyl phosphonic acid (ethrel) (Ingle et al., 1982; Suryanarayana and Goud, 1984) and ethylene (Sastry, 1970) greatly accelerate ripening. Polyethylene bags can also reduce weight loss in sapodilla fruit by about 50% (Kumbhar and Desai, 1986). Reduction of ethylene production and thus delaying of ripening has been reached by applying GA3 (300 ppm), kinetin (100 ppm) or silver nitrate (40 ppm) for 20 minutes. The treatment also stimulated a reduction in catalase and pectin methyl esterase activities (Gautam and Chundwat, 1990). Gibberellic acid extends the shelf life of sapodilla fruit, delays rotting, and reduces fruit softness and fruit skin shrinkage (Kumbhar and Desai, 1986). Exposure of mature sapodilla fruit to 100 ppm ethylene for 24 hours at 20 °C speeds up their ripening (Kader, 2009). Treatments with either 100 ppm 2,4-D, 500

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to 1000 ppm malic hydrazide or 25 ppm 2,4,5-T have been shown to slow down the ripening of sapodilla fruit (Lakshminarayana et al., 1967; Lakshminarayana and Subramanyam, 1966). Exposure of sapodilla fruit to gamma irradiation at 0.1 KGy extended their storage life by 3–5 days at 26.7 °C and 15 days at 10 °C without any negative effect on ascorbic acid (Salunkhe and Desai, 1984). Morais et al. (2008) treated sapodilla fruit with 1-MCP (an ethylene antagonist) at 300 nL L−1 for 12 hours followed by a storage period under a modified atmosphere at 25 °C for 23 days. They found a significant slowdown of fruit softening of sapodilla fruit for 11 days. 17.9.4 Recommended storage and shipping conditions The shelf life of sapodilla fruit depends on the storage conditions (relative humidity (RH), temperature, and atmosphere), the respiration rate, cultivar and ripeness stage (Yahia, 2004). These variables may be manipulated in order to extend the storage period. Singh et al. (1963) and Singh (1969) claimed that firm fruit can be kept at 3–5 °C and 85–90% RH for up to eight weeks, but if the fruit are already ripe, a temperature of 2–3 °C will keep them for six weeks, but this may cause chilling injury. Kader (2009) suggests a temperature of 14 °C ± 1 °C and 90–95% RH at which the fruit can be stored for 2–4 weeks. Levels of 5–10% CO2 delay ripening as well as the removal of ethylene from the storage environment (Yahia, 1998). Higher CO2 concentrations may damage the appearance and taste of the fruits and thus are not recommended (Broughton and Wong, 1979; Yahia, 1998). The use of perforated plastic bags or box liners for packing sapodilla fruit can help reduce water loss at relative humidities lower than 90–95% (Kader, 2009). Polyethylene bags with permanganate silica gel, an ethylene absorbent, were effective in extending the storage period by 10–12 days at room temperature or 12 °C (Banik et al., 1988).

17.10

Processing

As mentioned previously, sapodilla fruit are generally eaten fresh as a dessert. Some people use the skin, which is not eaten, as a ‘shell’ in which to serve a dessert, since it remains firm enough. In some areas, the juice is boiled and preserved as syrup or the flesh used to make jam (Morton, 1987). Ripe sapodillas have been successfully dried after pretreatment with a 60% sugar solution. Osmotic dehydration for five hours gave a product with acceptable quality for two months (Morton, 1987). Dried sapodilla fruit is consumed in India and sterilization of canned sapodilla slices has been achieved by using a combination of heat and radiation. After removing the fruit peel, sapodillas were sliced and canned with sucrose syrup. Treatment at 70 °C and 10 min and irradiation with 4 × 105 rads at room temperature produced an acceptable product (Dharkar et al., 1966).

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Sapodilla fruit were also processed into a powder and added to traditional Indian recipes. The flavor, aroma and natural color of sapodillas were conserved after processing and added to milk shakes, coconut burfi and banana shikarani (Devadattam et al., 2005).

17.11

Conclusions

Sapodilla is a climacteric fruit that requires careful handling after harvest in order to maintain quality, extend shelf life and allow transport to markets outside the area of production. If this can be achieved, sapodillas, together with other tropical fruits, could potentially become known in other areas. The use of controlled/ modified atmospheres and other methods of preservation become important when dealing with highly perishable produce such as sapodilla fruit. Storage temperature is another key factor in conserving sapodillas, since these fruit are chilling sensitive and special care must be taken when cold storage is used. Finally, the presence of fruit at different stages of development on the tree makes it difficult to determine the optimum harvesting time, and therefore it is necessary to develop appropriate maturity indices that would facilitate the identification of fruit ready to be harvested. This would increase homogeneity of fruit quality.

17.12

References

Abdul-Karim MNB, Tarmizi SA and Bakar AA (1987), The physio-chemical changes in ciku (Achras sapota L.) of Jantung variety, Pertanika, 10(3), 277–282. Bakar FA and Abdul-Karim MNB (1994), Chemical treatments for microbial control on sapota, ASEAN Food J, 9(1), 42–43. Balasubramanian P, Ponnuswami V and Irulappan I (1988), A note on susceptibility of sapota varieties and hybrids to leaf spot disease (Phaeophleospora indica Chinnappa), South Indian Hort, 36(1–2), 72–73. Banik D, Dhua RS, Ghosh SK and Sen SK (1988), Studies on extension of storage life of sapota (Achras sapota L.), Indian Journal of Horticulture, 45, 2141–2248. Bojappa, KKM and Reddy TV (1990), Postharvest treatments to extend the shelf life of sapota fruit, Acta Horticulturae, 269, 391 (Abstract). Broughton WJ and Wong HC (1979), Storage conditions and ripening of chiku fruits Achras sapota L., Scientia Hort, 10, 377–385. Brown BI and Wong LS (1987), Postharvest changes in respiration, ethylene production, firmness and ripe fruit quality of sapodilla fruit [Manilkara zapota (L.) Van Royen] of different maturities, Singapore J Pri Ind, 15(2), 109–121. Chadha KL (1992), Strategy for optimization of productivity and utilization of sapota [Manilkara achras (Mill.) Forberg.], Indian J Hort, 49(1), 1–17. Chundawat BS (1991), Postharvest handling and marketing of sapota fruits, National Seminar on Optimization of Production and Utilization of Sapot, October 8, Navsari, Gujarat, India. Das RC and Mahapatra SK (1976), Effect of growth substances and fungicidal wax emulsion on ripening of sapota, Prog Hort, 8(3), 75–80. Devadattam DSK, Ganjyal GM and Hanna MA (2005), Processing of Sapota (sapodilla): powdering, Journal of Food Technology, 3(3), 326–330.

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Dharkar SD, Savagaon KA, Kumta US, Sreenivasan A (1966), Development of a radiation process for some Indian fruits: mangoes and sapodillas, Journal of Food Science, 68(2), 517–520. García Gómez GA (1988), ‘Sapotoceas: cultivos promisorios’, Seminario Agronomía, Universidad Nacional de Colombia, Facultad de Agronomía, Medellín. Gautam SK and Chundawat BS (1990), Postharvest changes in sapota cv. ‘Kalipatti’: I – Effect of various postharvest treatments on biochemical changes, Indian J Hort, 46(3), 310–315. Ingle GS, Khedkar DM and Dabhade RS (1982), Ripening studies in sapota fruit, Indian Food Packer, 36, 72–77. Joshi GD and Paralkar PS (1991), Effect of ripening media and storage behavior of sapota fruits, National Seminar on Optimization of Productivity and Utilization of Sapota, organized by the Horticultural Society of India at Guajarat Agricultural University, India, October 8, p. 33. Joshi GD and Sawant VS (1991), Influence of harvesting techniques, grading and wrapping on storage behavior of sapota fruits. National Seminar on Optimization of Productivity and Utilization of Sapota, organized by the Horticultural Society of India at Guajarat Agricultural University, India, October 8, p. 32. Kader AA (2009), Sapotes (sapodilla and mamey sapote): ‘Recommendations for maintaining postharvest quality’, Department of Plant Sciences, University of California, Davis, CA. Available from: http://postharvest.ucdavis.edu/Produce/ProduceFacts/Fruit/ sapotes.shtml (accessed 15 January 2010). Kumbhar SS and Desai UT (1986), Studies on the shelf-life of sapota fruits, J Maharashtra Agr. Univ, 11(2), 184–186. Kute LS and Shete MB (1995), ‘Sapota (sapodilla)’, in Salunkhe DK and Kadam SS, Handbook of Fruit Science and Technology Production, Composition, Storage and Processing, Marcel Dekker, Inc., New York, pp. 475–484. Lakshminarayana S (1980), ‘Sapodilla and prickly fruit’, in Nagy S and Shaw P E, Tropical and Subtropical Fruits, AVI Publishing, Westport, Connecticut, p. 415. Lakshminarayana S and Rivera MA (1979), Proximate characteristics and composition of sapodilla fruits grown in Mexico, Proceedings of the Florida State Horticultural Society, 92, 303–305. Lakshminarayana S and Subramanyam H (1966), Physical, chemical and physiological changes in sapota fruit [Achras sapota Linn. (Sapotaceae)] during development and ripening, J Food Sci Tech, 3, 151–154. Lakshminarayana S and Subramanyam H (1967), Effects of preharvest spray of maleic hydrazide and isopropyl N-phenyl carbamate on sapota, J Food Sci Tech, 4(2), 70–73. Lakshminarayana S, Subramanyam H and Surendranath V (1967), Preharvest spray of growth regulators on the size, composition and storage behavior of sapota (Achras sapota L.), J Food Sci Tech, 4, 66–69. McGregor BM (1987), Tropical Products Transport Handbook, United States Department of Agriculture, Office of Transportation, Agric. Handbook No. 688. Mickelbart MV (1996), ‘Sapodilla: a potential crop for subtropical climates’, in Janick J, Progress in New Crops, ASHS Press, Alexandria, VA, pp. 439–446. Mohamed S, Taufik B and Karim MNA (1996), Effects of modified atmosphere packaging on the physiological characteristics of ciku (Arcas sapota L.) at various storage temperatures, J Sci Food Agric, 70, 231–240. Morais PLD, Miranda MRA, Lima LCO, Alves JD, Alves RE and Silva JD (2008), Cell biochemistry of sapodilla (Manilkara sapota) submitted to 1-metrylcyclopropene, Brazilian Journal of Plant Physiology, 20(2), 85–94. Morton J (1987), ‘Sapodilla’, in Morton JF, Fruits of Warm Climates, Miami, FL, pp. 393–398. Orwa C, Mutua A, Kindt R, Jamnadass R and Anthony S (2009), ‘Agroforestree Database: a tree reference and selection guide version 4.0’, Available from http://www. worldagroforestry.org/sites/treedbs/treedatabases.asp (accessed 14 January 2010).

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Paralkar PS (1985), ‘Studies on physic-chemical changes in sapota (Manilkara archas (Mill) Forsberg) cv. Kalipatti fruits during growth, development and storage.’ MSc (Agri) thesis submitted to the Konkan Krishi Vidyapeeth, Dapoli, Ratnagiri, Maharashtra State, India. Pathak S and Bhat JV (1952), Studies on the microrganisms associated with Achras sapota, J Univ Bombay, 20(5), 14–18. Pathak S and Bhat JV (1953), The carbohydrate metabolism of Acras sapota fruit, J Univ Bombay, 21(5), 11–16, Section A. Polania Trujillo H (1986), Recomendación para el cultivo del níspero, ESSO Agrícola, 33(2), 16–18. Purseglove J W (1968), Tropical Crops: Dicotyledons, Longman Group, London, 647 pp. Rao DVR and Chundawat BS (1988), Ripening changes in sapota cv. Kalipatti at ambient temperature, Indian Journal of Plant Physiology, 31, 205–208. Roy SK and Joshi GD (1997), ‘Sapota’, in Mitra S, Postharvest Physiology and Storage of Tropical and Subtropical Fruits, CAB International, Wallingford, UK, 387–394. Salunkhe DK and Desai BB (1984), Postharvest Biology of Fruits, Volume II. CRC Press Inc, Boca Raton, Florida. Sastry MV (1966a), Biochemical studies on the physiology of sapota, Part I, Physical changes, Indian Food Packer 20, 11–16. Sastry MV (1966b), Biochemical studies on the physiology of sapota, Part II, Major chemicals, Indian Food Packer 20, 16–20. Sastry M V (1970), Biochemical studies in the physiology of sapota, Part IV – Ripening and storage studies, Indian Food Packer, 24, 24–26. Sawant VS (1989), ‘Studies on postharvest handling and preservation of sapota (Manilkara archas (Mill) Forsberg) cv. Kalipatti fruits during growth, development and storage’. MSc (Agri) thesis submitted to the Konkan Krishi Vidyapeeth, Dapoli, Ratnagiri, Maharashtra State, India. Selvaraj Y and Pal DK (1984), Changes in chemical composition and enzyme activity of the sapodilla (Manilkara zapota L.) cultivars during development and ripening, Journal of Horticultural Science, 59, 275–281. Shanmugavelu K, Srinivasan G and Rao VNM (1971), Influence of etherel (2-chloroethyle phosphonic acid) on ripening of sapota (Achras zapota L.), Hortic Adv, 8, 33–36. Shende UB (1993), ‘Studies on some aspects of postharvest handling and processing of sapora (Manilkara archas (Mill) Forsberg) cv. Kalipatti’. MSc (Agri) thesis submitted to the Konkan Krishi Vidyapeeth, Dapoli, Ratnagiri, Maharashtra State, India. Singh R (1969), Fruits, National Books Trust, India, pp. 120–123. Singh S, Krishnamurthi S and Katyal SL (1963), Fruit Culture in India, ICAR, New Delhi, pp. 192–198. Sulladmath UV and Reddy NMA (1990), ‘Sapota’, in Bose T K and Mitra S K, Fruits: Tropical and Subtropical, Naya Prokash, Calcutta, pp. 565–591. Sulladmath VV, Rao MM and Advani MR (1979), Studies on the pattern of growth of development of ‘Kalipatti’ sapota [Manilkara achras (Mill.) Forsberg] fruit, J Maharashtra Agr Univ, 4(1), 55–60. Sundararajan S and Madhava Rao VN (1967), Studies on fruit development and fruit quality in some varieties of sapota (Achras zapota L.), South Indian Hort, Suryanarayana V and Goud V (1984), Effects of post ethrel treatment on ripening of sapota fruits, The Andrha Agricultural Journal, 31, 308–311. Thapa MJ (1980), ‘Some studies on the osmotic dehydration of sapota’, Dissertation for the MSc (Food Tech) submitted to the University of Mysore, Karnataka, India. Yahia E M (1998), Modified/controlled atmospheres for tropical fruits, Horticultural Reviews, 22, 123–183. Yahia EM (2004), ‘Sapodilla and related fruits’, in U.S. Dept. Agric. Handbook #66 (http:// www.ba.ars.usda.gov/hb66/index.html).

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(a)

(b)

Plate XXXI

(Chapter 16) Mature (a) and immature (b) Rakam.

(a) (b)

(c)

Plate XXXII

(Chapter 17) Sapodilla tree and fruit.

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18 Soursop (Annona muricata L.) M. A. Coêlho de Lima and R. E. Alves, Brazilian Agricultural Research Corporation (EMBRAPA), Brazil

Abstract: Soursop is a very perishable fruit. At room temperature, it has a shelf life limited to five days when it has been harvested at physiological maturity. Research into this fruit has been limited to date but its attractive flavor favors its commercialization in different regions. Identification of the correct harvest time and the use of postharvest technologies such as refrigeration, coatings and modified atmospheres, etc., can extend the shelf life of soursop fruit. The impact of orchard management on fruit quality is also considered. Key words: annonaceae, maturation, postharvest conservation, quality.

18.1

Introduction

Soursop fruit is an exotic commodity in most markets, therefore the quantity harvested comprises only a small percentage of total world fruit production. Cultivation is restricted to a few countries where consumption is more widespread. However, the distinctive and characteristic flavor of soursop gives it the potential to conquer new markets. This is dependent, though, on the development and employment of efficient handling and postharvest conservation technologies: without these, sale of the fruit is limited to regions near the areas of cultivation. In most of the producing countries even the traditional markets for fresh soursop are not supplied with the required regularity due to the fruit’s high perishability and short postharvest conservation period. Both have been responsible for the high rates of loss of soursop fruit. Notwithstanding the postharvest conservation issues, there has been very little research into soursop fruit to date. The studies have generally characterized the maturation of the fruit through changes in peel color and the levels of sugars, organic acids and phenolic compounds found in the pulp (Paull et al., 1983; Aziz and Yusof, 1994). In addition, studies carried out by Lima et al. (2006) present

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information on the main changes related to the softening of soursop fruit due to physical, chemical and biochemical factors during postharvest ripening at room temperature. In order to elucidate the metabolism of soursop fruit, more information than is currently available is required for further studies on conservation techniques suitable to the quality standards of different markets. Regarding postharvest technologies, some studies are at present being carried out and include the use of cooling, modified atmosphere packaging (MAP), coatings and ethylene inhibitors. 18.1.1 Origin, botany, morphology and structure Soursop (Annona muricata L.) is a species natural to the tropical Americas, most commonly found on the Caribbean islands (Zayas, 1966). It belongs to the Annonaceae family and like other fruit of the genus Annona is a syncarp formed by the coalescence of pistils and receptacles in a large pulpy structure. It is, therefore, a compound fruit formed by a cluster of berries, whose individual carpel components remain in the peel during the entire development in the form of spurs or pulpy spines, which are curved and short (Bueso, 1980; Worrell et al., 1994). Each unit resulting from the fertilization of an ovary is called a fruitlet. Irregular (i.e. atypical) fruits may appear (Bueso, 1980), due to fertilization and fruiting failure. Such fertilization issues are mostly due to phenomena such as heterostyly (Ramos, 1999) and protogynous dichogamy (Worrell et al., 1994; Ramos, 1999). However, in commercial plantations where hand pollination is a regular procedure, the fruits are ovoid or cordate, measuring 15 to 30 cm in length and 10 to 20 cm in width, with an average weight of 4.5 kg. The peel is thin and dark green in color (see Plate XXXIII(A) in the colour section between pages 238 and 239). The mesocarp contains seeds of shiny dark brown color, which measure about 2 cm in length and 1 cm in width. The pulp, which consists of fibrous, juicy segments or buds (the fruitlet) around an oblong receptacle, is white (Fig. 18.1) and has an acid taste and characteristic flavor (Zayas, 1966; Bueso, 1980; Falcão et al., 1982). When the fruit is ripe, the fruitlets separate easily from the total mass. 18.1.2 Worldwide importance The world production of soursop fruit is concentrated in a few South American countries, mainly Venezuela, Brazil and Colombia. In Venezuela, the main producer of the fruit in South America, the states with largest production are Zulia, Mérida and Trujillo (Ministerio del Trabajo y Seguridad Social, 1995). However, up-to-date official statistics on production and commercialization of the fruit are not available even in these states (Lima et al., 2002b). In Colombia, fresh soursop fruit is said to be available throughout the year. The country is a large consumer of the fruit, even importing it from Venezuela in the form of frozen pulp. Beside the South American countries, soursop occupies a prominent position in the fruit markets of Central America and the Caribbean, and it also stands out on the Asian continent (Universidade Federal de Uberlândia, 2010). In Central

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Fig. 18.1

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Pulp aspect of soursop fruit. Photo: Maria Auxiliadora Coêlho de Lima.

America, Mexico is an important producer and consumer of soursop fruit. The country exports the fruit regularly throughout the year and has recorded an increase in yearly mean values in the market for the fresh fruit over the last five years (Panorámica, 2010). In general terms, one of the main problems with the commercialization of soursop fruit is the transport, which is done by truck and without proper packaging, resulting in elevated losses when the product reaches the retail market (Calzavara and Muller, 1987; Moura, 1988). Although in Brazil soursop fruit has been mentioned in literature since the beginning of the 20th century (Correa, 1984), its commercial importance for the domestic and export markets is still very low, and the interest in exploring it commercially is quite recent (Calzavara and Muller, 1987). In Brazil, soursop production is concentrated in the north and northeast, from where the fruit is distributed to other regions of the country. The largest product of commercial production of soursop is the frozen pulp, which supplies the juice and ice cream industries. Over the last few years, the area of Brazilian land used for soursop

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cultivation has been reduced. The main reason for this is the increase in production costs, due to the large incidence of pests such as stem borer and fruit borer. On the other hand, even though secure and objective statistical data may not be available, the demand for soursop pulp is growing in the Brazilian as well as in the European market. Regarding the external market, there is a demand for soursop pulp both in the Middle East and in Europe (Germany and Spain) (Secretaria de Agricultura do Estado da Bahia, 2010). However, the exportation of pulp and other soursop fruit products has been restricted to a few countries, such as Mexico, Puerto Rico, Venezuela and Costa Rica. For years, soursop pulp has been served in Mexican restaurants in New York and other big cities in the United States, soursop pulp concentrates have been commercialized in Venezuela, while nectar is sold in several countries. In Costa Rica, soursop pulp and frozen fruit concentrates have been traditionally sold for several years (Morton, 1987). 18.1.3 Culinary uses, nutritional value and health benefits Soursop fruit is suitable for processing because of its high sugar content and delicate flavor (George, 1984; Mororó et al., 1997). However, there are limitations on the industrial processing of soursop fruit. Soursop fruit is sold as fresh or frozen pulp, strained soursop juice, and frozen concentrates, which have been preserved as various juice blends, ice creams, sherbets, nectars, syrups, shakes, jams, jellies, preserves, yoghurts and ice creams (Bueso, 1980; Morton, 1987; Umme et al., 1999; Gratao et al., 2007). It is also a raw material for powders, fruit bars and flakes (Umme et al., 2001). It can be made into a fruit jelly with the addition of gelatin or used in the preparation of beverages, sherbets, ice creams and syrups (Bueso, 1980; Badrie and Schauss, 2009). The immature fruits with soft seeds have been cooked as vegetables. Seeds can be roasted or fried (GetJamaica.Com, 2008). The white edible pulp of soursop fruit contains 80–85% water, 1% protein, 18% carbohydrate, 0.70–3.43% titratable acidity and 13.5–19% soluble solids, with about 1.0% fiber content and vitamins B1, B2, and C (Wenkam and Miller, 1965; Paul et al., 1983; Castro et al., 1984; Rice et al., 1991; Filgueiras et al., 2002; Onimawo, 2002; Lima et al., 2003a, 2003b, 2004; Lako et al., 2007). The reducing sugars, glucose and fructose, were 81.9–93.6% of the total sugar content. Using gas-liquid chromatography, the fructose, D-glucose and sucrose contents of soursop pulp were found to be 1.80, 2.27 and 6.57% respectively, giving a total sugar content of 10.48% (Chan Junior and Lee, 1975). According to Filgueiras et al. (2002), the medium pulp yield is approximately 80%. Eleven free amino acids were identified using paper chromatography and four other unidentified ninhydrin-positive components were detected. The most abundant free amino acids were proline and γ-aminobutyric acid (Ventura and Hollanda-Lima, 1961). Other amino acids detected, in order of the amount present, were glutamic acid, aspartic acid, serine glycine, alanine, citrulline, cysteine (or cystine), arginine and lysine (Paull, 1998). Kuskoski et al. (2006) examined the total polyphenol index and the antioxidant activity of soursop pulp, finding values of 84.3 ± 5.8 mg.100 g−1 and 2.88 ± 0.2 μmol

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Trolox equivalent.g−1 fresh matter after 30 minutes. Lako et al. (2007) evaluated fresh fruit and found values of 72 mg.100 g−1 Trolox equivalent for the total antioxidant capacity, and 42 mg.100 g−1 equivalent in gallic acid for the total polyphenol content, supplying an estimate of losses occurring during processing. The authors also characterized the content of some flavonols in soursop fruit. They observed a myricetin content of 3 mg.100 g−1, less than 1 mg.100 g−1 of fisetin, 2 mg.100 g−1 of morin, 2 mg.100 g−1 of quercetin, 2 mg.100 g−1 of kaempferol and less than 1 mg.100 g−1 of isorhamnetin. The quantification of these compounds helps to determine which particular properties of soursop fruit are instrumental in preventing certain diseases related to the presence of free radicals in the organism. For example, A. muricata is an abundant fruit tree that yields acetogenins. Some of these acetogenins, including bullatacin, have the potency of taxol against L1210 murine leukemia. They work by inhibiting adenosine triphosphate (ATP) production (Badrie and Schauss, 2009).

18.2

Fruit growth and ripening

Understanding the postharvest physiology of soursop fruit is necessary for the establishment of handling procedures and the recognition of ideal packaging conditions. It is also useful when selecting materials and techniques to protect the fruit from external factors which may accelerate deterioration. When studying postharvest physiology, it is assumed that physiological changes which occur after harvest are affected by agricultural practices and environmental conditions during cultivation, as well as by the fruit’s own metabolism during its growth, development and maturation. 18.2.1 Fruit growth, development and maturation According to Worrell et al. (1994) and Livera and Guerra (1996), the fruit’s growth pattern is of the double sigmoid type, presenting three characteristic stages. The initial stage of rapid growth begins immediately after the end of the quiescence (the period of rest after fertilization of the blossom, which is characterized by the darkening of the upper part of the carpel). At the end of this stage, the soursop fruit has already reached half of its final size and shoulders have begun to develop around the point of pedicel attachment. The following stage (lag phase) is characterized by relatively slow growth and precedes the final stage of rapid growth. During the latter the fruit reaches maturity and its maximum size (Worrell et al., 1994). Under Brazilian climate conditions, soursop fruit reaches complete maturity between four and six months after pollination, depending on the time of year (São-José, 1997). In the northeast of Brazil, studies have shown that the fruit reaches its physiological maturity around 90 days after the beginning of the quiescence period (Mosca, 1996). Maturation constitutes the final stage of fruit development, during which the cells reach their maximum size and characteristic composition (Kays, 1997). For soursop

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fruit, the main changes associated with maturation are: greater separation between and loss of firmness of the spurs; loss of firmness of the fruit surface, which is noticeable to the touch. The divisions between the loculi protrude, showing the fruitlets; and the seeds turn a shining dark brown color. For most of the phenotypes, the shine of the peel also increases and its color changes from dark green to a lighter tonality, as shown in Plate XXXIII(B) in the colour section (Zayas, 1966; Worrell et al., 1994; Borrero et al., 1995; Livera and Guerra, 1996; São-José, 1997; Salgado et al., 1998; Filgueiras et al., 2002). However, the time from fruit formation to physiological maturity, which is taken as a secure indication for harvesting for certain crops, is not an appropriate one for soursop fruit (Borrero et al., 1995; Livera and Guerra, 1996). The duration of the second growth stage can differ, resulting in variations in the maturation stages between fruits of the same age (Livera and Guerra, 1996). A series of mostly independent changes characteristically occur during ripening, which includes the final stages of maturation and the beginning of the senescence. Emphasis can be placed on those which result in alteration of flavor, color and firmness (Kays, 1997; Wills et al., 2007). In soursop fruit, the modifications related to fruit ripening occur over a very short period (Paull, 1982; Aziz and Yusof, 1994; Mosca et al., 1997), reflecting an elevated metabolic activity. Studies carried out by Paull (1982) and Lima et al. (2003a) show that fruits which are harvested at physiological maturity and kept at room temperature ripen within five days. Until the soursop fruit is completely ripe, it goes through changes, for example in its respiratory activity, ethylene production, contents of total soluble solids, sugars and starch, in volatile compounds and in total titratable acidity (Paull, 1982, 1990; Paull et al., 1983; Bruinsma and Paull, 1984; Castro et al., 1984; Aziz and Yusof, 1994; Worrell et al., 1994; Borrero et al., 1995; Mosca et al., 1997). 18.2.2 Respiration, ethylene production and ripening Fruits of the family Annonaceae, such as soursop, are classified as climacteric for presenting an increase in their respiratory activity and ethylene production during maturation. These fruits ripen after harvest (Alves et al., 1997). However, the respiratory activity of soursop fruit during ripening is different to that of most other climacteric species. Biale and Barcus (1970) characterized soursop fruit as having a diffuse climacteric pattern with more than one peak. The same was observed for other species of the genus Annona and was attributed to the fact that the fruit is formed by many aggregate ovaries. The development and further ripening of each fruitlet seemed, therefore, to be variable within the pulp of the organ as a whole. Other authors have developed research on the respiratory activity of soursop fruit (Paull, 1982, 1990; Paull et al., 1983; Bruinsma and Paull, 1984; Worrell et al., 1994; Lima et al., 2003b). Most of these studies were carried out on the intact fruit. However, Bruinsma and Paull (1984) studied the respiratory activity in both intact fruits and soursop tissue discs. The authors observed that the diffuse climacteric pattern occurred in the discs as well. Given this fact, they concluded that the initial

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respiratory increase was caused by the elevation in mitochondrial respiration due to an increase in the supply of induced carboxylate substrates, probably induced by the separation of the fruit from the tree. This contradicts the assumption that the existence of two respiratory peaks reflects the changes in tissues that are in different physiological stages (Biale and Barcus, 1970; Paull, 1982). When researching the respiratory behavior of ‘Morada’ soursop fruit, Lima et al. (2003b) observed that CO2 production was stable at about 70 mg CO2.kg−1.h−1 until the second day after harvesting at physiological maturity (Fig. 18.2). From the second day a rapid increase began, resulting in the first respiratory peak and corresponding to a production of 197.60 mg CO2.kg−1.h−1. Other authors reported the occurrence of the first respiratory peak from the second to the fourth day after harvesting, with values varying from 50 to 170 mg CO2.kg−1.h−1 (Biale and Barcus, 1970; Paull, 1982; Bruinsma and Paull, 1984; Worrell et al., 1994). After the first climacteric peak, few variations in the respiratory activity of soursop fruit occurred, characterizing a lag phase (Worrell et al., 1994; Lima et al., 2003b). At the end of this phase, the next respiratory increase resulted in the climacteric peak itself, which was observed between the fourth and the fifth day after harvesting and reached 298.82 mg CO2.kg−1.h−1 in the study by Lima et al. (2003b). The occurrence of this peak could be observed from the fourth to the sixth day after harvesting, with values ranging from 130 to 305 mg CO2.kg−1.h−1 (Biale and Barcus, 1970; Paull, 1982; Bruinsma and Paull, 1984; Worrell et al., 1994). Differences in the respiratory rates verified in both peaks can be attributed to the maturation phases used in each study, as well as the genetic material, the methods employed, and the conditions that the fruits were submitted to, especially temperature.

Fig. 18.2 Respiratory behavior and ethylene production of ‘Morada’ soursop fruit harvested at physiological maturity and stored under room temperature. Source: Lima et al. (2003b).

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Typical characteristics of ripening such as changes in color, firmness and development of flavor and aroma are associated with the climacterium (Biale and Barcus, 1970). However, some of these depend on the production of the phytohormone ethylene (Jeffrey et al., 1984; Ayub et al., 1996). Ethylene production starts with methionine which, through successive reactions, forms S-Adenosyl methionine and 1-aminocyclopropane-1-carboxilic acid (ACC). Under the action of ACC oxidase the latter produces ethylene (C2H4), CO2 and cyanide (Dean and Mattoo, 1991; Kende, 1993; Kays, 1997). The synthesized ethylene connects to sites in the cell membranes that have characteristic receptors. They are, therefore, saturable, present a high affinity and specificity for ethylene, can suffer denaturation and are liable to competitive inhibition by structurally similar molecules (Paliyath and Droillard, 1992). From this viewpoint, some work has been carried out with the purpose of delaying the ripening or the senescence of some organs. Studies of this nature brought about the identification of the gene ETR1 which codifies for a protein that is a receptor of ethylene (Bleecker and Schaller, 1996). In climacteric fruits, the increase in ethylene production during ripening may occur before, during or after the climateric peak. In those fruits the biosynthesis of ethylene is called autocatalytic (Tucker, 1993). Experiment results have shown that the ethylene production in soursop fruit is not detectable until two days after harvesting (Bruinsma and Paull, 1984). Lima et al. (2003b) started to detect ethylene production on the third day after harvesting, on the occasion of the first respiratory peak (Fig. 18.2). From that point on, the synthesis increases until reaching the ethylene peak, which is followed by a decrease (Paull, 1982; Bruinsma and Paull, 1984; Worrell et al., 1994). Values from 40 to 350 μL.kg−1.h−1 have been observed for this peak (Paull, 1982; Bruinsma and Paull, 1984; Worrell et al., 1994; Lima et al., 2003b). In the studies carried out by Lima et al. (2003b), the ethylene peak occurred on the fourth day, matching with the respiratory increase which results in the climacteric peak. This result reinforces the idea that the climacteric increase is a response to ethylene (Dean and Matoo, 1991). The recognition of the moment at which the changes in the respiratory activity and the ethylene production in Annona species occur allows a close estimate of the expected shelf life for these fruits, as these events are associated to a series of other changes that result in the best quality for consumption. Bruinsma and Paull (1984) and Worrell et al. (1994) reported changes in the development of the flavor, the darkening of the peel and the softening of the soursop pulp during the autocatalytic ethylene production.

18.3

Maturity and quality components and indices

The beginning of the maturation is marked by several physiological events, whose importance and intensity vary according to the fruit. For soursop fruit, the rapid ripening is marked by an intense metabolic activity, which is responsible for abrupt changes, most of which are scientifically little known until now.

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Due to the existing association of some of these physiological responses with quality components that define the consumer acceptance of the product, they can be used as maturity indexes, supporting the decision about the right time for harvesting or the best moment for consumption. 18.3.1 Dry matter The percentage of dry matter in fresh soursop pulp is about 13.6 according to Leterme et al. (2006). This value is proximate to the one informed by Paull (1982) for the pre-climacteric phase. The author presented decreasing fruit dry matter values from the pre-climacterium on, so that on the occasion of the climacteric peak the percentage was 4.0. 18.3.2 Color and pigments Although not all fruits change their color during ripening, it is one of the characteristics that are mostly associated with the harvest point and maturity for consumption (Tucker, 1993). The period, the velocity and the intensity of change vary according to the species and between cultivars of a same species (Kays, 1997). The most representative changes occur on the level of chlorophyll degradation. Although the exact mechanism of this degradation has not been fully understood yet, it is presumed that the chlorophyll molecule is solubilized from the thylakoid membranes of the chloroplast to the stroma, where it is oxidized (Tucker, 1993). Concomitant to the chlorophyll degradation there might be a synthesis of other pigments in some fruits (Tucker, 1993; Kays, 1997; Wills et al., 2007). For soursop fruit, the changes in peel color are due to chlorophyll degradation. Worrell et al. (1994) report variations in the intensity of the peel color from the development on until the physiological maturity. On the occasion of the ripening of the fruits, Paull (1982), Aziz and Yusof (1994) and Lima et al. (2003b) observed that the peel color turned to a lighter green. On the other hand, Lima et al. (2003a) did not find significant variation in the chlorophyll level during the postharvest maturation of ‘Crioula’ soursop fruit. When senescence approaches, a browning can be noted that tends to be general (Paull, 1982). Regarding the pulp color, the ripening of the soursop fruit does not imply in noteworthy changes, as it is determined only by brightness (Lima et al., 2003a, b). Considering that changes in the fruit color can coincide or not with the development of other characteristics associated with ripening, generally they must not be seen as secure means to evaluate maturation (Kays, 1997). 18.3.3 Soluble solids and sugars The soluble solids content, defined as the percentage of solids dissolved in the juice extracted from the pulp, has been used as a maturity indicator for several

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fruits and is constituted mostly by sugars. During maturation there is an increase in the soluble solids and sugar rates. This increase is attributed mainly to the hydrolysis of reserve carbohydrates which were accumulated during the growth of the fruit on the tree, resulting in the production of soluble sugars (Tucker, 1993; Kays, 1997; Wills et al., 2007). Soluble sugar content of many fruits is about 5 to 10% but can vary considerably according to the cultivar, the soil type and the climatic conditions during the period of plant life. Moreover, significant variation in the sugar content of climacteric fruits may occur during the period between the harvest and the ideal consumption point (Whiting, 1970). According to Borrero et al. (1995), the soluble solids content of soursop fruit increases during the different development stages until reaching 7.0 °Brix when the fruit is physiologically mature. The characteristic flavor, as well as the aroma, is achieved during storage (Borrero et al., 1995), when the soluble sugar rate increases while there is a climacteric increase (Paull, 1982). However, Lima et al. (2003b) point out that a significant accumulation of soluble solids in soursop fruit happens on the occasion of the first respiratory peak. Among the sugars that are present in the fruit pulp, the most important are glucose, fructose and sucrose. The disaccharide sucrose is the main non-reducing sugar, while glucose and fructose constitute the main reducing sugars. In soursop fruit, a characteristic increase in reducing sugar contents occurs during maturation (Lima et al., 2003a). For non-reducing sugars, the available studies have presented differing responses. According to Chan Junior and Lee (1975), sucrose represents 62% of soluble sugars, while glucose and fructose total 22% and 17%, respectively. Aziz and Yusof (1994), however, obtained lower levels of sucrose than the ones of glucose and fructose, from the initial stages of fruit growth until ripening. During the postharvest maturation, as Lima et al. (2003a) have informed, the nonreducing sugar contents keep practically unaltered in ‘Crioula’ soursop fruit. It is likely that the enzymes acid invertase and sucrose synthase, mainly the former, hydrolyze the sucrose preventing it from accumulation (Ohyama et al., 1995). The proportion between the different types of sugar is an important quality attribute since they differ from each other in sweetness. Sucrose, for instance, has a higher sweetness level than glucose, whereas for both this level is lower than it is in fructose (Pangborn, 1963). Therefore, fruits with fructose contents higher than any other sugar contents are consequently sweeter. 18.3.4 Titratable acidity and pH The changes in acidity are also important in the development of the characteristic flavor of fruit. Although several organic acids are found, generally only one or two accumulate in the same type of fruit (Kays, 1997). For most fruits, the organic acid content diminishes with ripening due to the use of the Krebs cycle, during the respiratory process, and in the synthesis reaction of new compounds (Kays, 1997). Nonetheless, for soursop fruit (Paull, 1982;

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Paull et al., 1983; Bruinsma and Paull, 1984; Aziz and Yusof, 1994; Lima et al., 2003a, 2003b) and for other annonaceae, like atemoya (Wills et al., 1984) and cherimoya (Muñoz et al., 1997), an increase in the contents of the referred acids has been verified during ripening. In soursop fruit, titratable acidity increases slowly during the growth process (Borrero et al., 1995) and the beginning of maturation (Aziz and Yusof, 1994). Along the maturation, however, the increase gets more accentuated (Paull et al., 1983; Lima et al., 2003a, 2003b). Of all the acids found, malic acid is the one that most accumulates while the fruit ripens. Paull et al. (1983) verified a seven-fold increase in the content of this acid, while the citric acid content just tripled. Therefore it is the increase of malic acid that contributes significantly to the acid flavor of the fruit, according to Paull (1982). Studies carried out by Lima et al. (2003b) point out that the period of greatest increase in titratable acidity in ‘Morada’ soursop fruit coincides with the respiratory increase and the first CO2 peak. This finding suggests that the increase might be a consequence of the glycolysis induced by the harvest, with intense glucose oxidation and starch hydrolysis, as has been suggested by Bruinsma and Paull (1984). According to Livera and Guerra (1995), the increase in organic acids in soursop fruit may be associated with three possible causes: the catabolism of starch and cell wall carbohydrates, which also supply substrates for the synthesis of sugars and volatile compounds; the transformation of acid salts in free forms; and the low utilization of organic acids in respiration. It is likely that the latter is the main cause and that the others are of minor importance, since other fruit that do also have high starch content at the time of harvest present a decrease in titratable acidity after being harvested (Lima et al., 2003a). As a consequence of the changes in titratable acidity, the pH is concomitantly modified. During the development of the soursop fruit, the pH slowly decreases from 5.6 to 5.4. However, when the ripening process initiates, the pH drops abruptly to values around 3.6–3.7 (Aziz and Yusof, 1994; Lima et al., 2003a). 18.3.5 Phenolic compounds Studies on soursop indicate that there is a reduction in the phenolic contents during maturation (Paull, 1982; Aziz and Yusof, 1994; Oliveira et al., 1994), but also that these quantitative alterations are little significant (Lima et al., 2003a). Nevertheless, there might be considerable changes among some types of predominant phenolics. The composition of phenolic compounds is determined by genetic and environmental factors, but can be modified by oxidative reactions during storage and processing. The two most important processes involve the antioxidant activity of phenols and the oxidative browning (Robards et al., 1999). Some fruit are especially prone to browning, including soursop fruit (Oliveira et al., 1994; Borrero et al., 1995), and so their sensorial properties and nutritional value are affected (Mayer and Harel, 1979).

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18.3.6 Firmness Soursop fruit firmness is abruptly reduced in a few days after harvesting, as shown in Fig. 18.3 (Lima et al., 2003b). According to the authors, the most important changes coincide with the first respiratory increase and the peak in ethylene liberation. On the other hand, Worrell et al. (1994) considered that the softening of soursop fruit started with the ethylene production and that, at the peak, all parts of the fruit would be soft already. The loss of firmness of soursop fruit, similar to other fruits, must be accompanied by a decrease in starch contents, an increase in the solubility of pectin, and a loss of cell wall galactose (Aziz and Yusof, 1994; Lima et al., 2003b).

Fig. 18.3

Pulp firmness of ‘Morada’ soursop fruit harvested at physiological maturity and stored under room temperature. Source: Lima et al. (2003b).

18.3.7 Starch content Soursop fruit is a typical example of a fruit with high starch content (Paull, 1982, 1990; Paull et al., 1983; Castro et al., 1984; Aziz and Yusof, 1994; Lima et al., 2006; Nwokocha and Williams, 2009). Nevertheless, it is a highly perishable fruit (Paull, 1982; Mosca et al., 1997; Lima et al., 2003a, 2003b), which, when mature, keeps only approximately 15% of the starch content that had been accumulated until the physiological maturity (Lima et al., 2006). Along with ripening, starch is converted to soluble sugars (Paull, 1982, 1990; Paull et al., 1983; Castro et al., 1984) and organic acids (Paull, 1982; Castro et al., 1984), reducing the firmness (Aziz and Yusof, 1994). The characteristics of the starch granules of soursop fruit may respond for many of the textural attributes of the fruit. Nwokocha and Williams (2009) informed that

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the shape of the granules is spherical, truncated and irregular. The granules have 60% starch content and the gelatinization temperature is 65.7–75.3°C. 18.3.8 Pectic substances Aziz and Yusof (1994) and Lima et al. (2006) registered a decrease in the total pectin content as well as in the soluble fraction of sodium hydroxide during ripening of soursop fruit. This variance coincided with the reduction in pulp firmness. The fractions that are soluble and water-insoluble (protopectin) have different levels of esterification and neutral sugar content. The non-soluble one, besides its high level of esterification, has neutral sugars both in the lateral chains and in the main one (Goldberg et al., 1986), assuring the tissue firmness. This fraction produces soluble pectin after the hydrolysis (Esteban et al., 1993). Generally, these alterations in the pectin content are associated with enzymatic degradation. However, the structural conformation of the molecule that is united, at least partially, by non-covalent interactions reinforces the possibility of nonenzymatic degradation, influenced by an apoplastic pH, by the levels of inorganic ions in the cell wall, by non-enzymatic proteins, by the porosity of the cell wall and by structural barriers (Huber et al., 2001). According to McCollum et al. (1989), the apparently more important changes in the content of pectic substances are qualitative. They involve, for instance, differences in the proportions of cell wall sugars, like rhamnose, xylose, uronides and uronic acids, between the stages of development and maturation (MartinCabrejas et al., 1994; Huysamer et al., 1997). Therefore, it has to be pointed out that the modifications in the cell wall polysaccharides of ripening fruit may derive from both the degradation and synthesis of polymers. Besides that, other mechanisms may be involved, as for instance: alterations in the cell wall pH, affecting the enzymatic activity; distribution of organic acids and inorganic ions; removal of lateral galacturonan chains; the calcium metabolism, as this ion normally binds to polygalacturonic acids, forming a structure known as egg box (Seymour and Gross, 1996). 18.3.9 Hydrolytic and oxidative enzymes activities The ripening involves an intense metabolic activity in a period that, as has been pointed out above, can be quite short for some fruit, like soursop fruit. During this phase, quantitative and qualitative transformations can be verified in the normal set of enzymes that respond for a large part to the changes in flavor, pigmentation and softening (Kays, 1997). Others have their importance associated with the appearance of the fruit. This applies for some oxidases involved in tissue browning (Mayer and Harel, 1979, 1981, 1991). During ripening, degradative changes in the cell walls are associated with the synthesis and/or activation of enzymes (Kays, 1997). Mainly, they are hydrolases whose action occurs at the same time that other biochemical and physiological activities are triggered (John and Dey, 1986; Wakabayashi, 2000).

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The content of hydrolytic enzymes increases as a consequence of the changes in the synthesis and/or degradation rates and not as a result of the activation of a precursor molecule which was synthesized during the early stages of the development. It is considered that in the course of time an unstable product of gene expression (protein) becomes stable. For enzymes, which normally act in the cell wall or in the vacuole, this stability would be a consequence of a transport or transformation mechanism of primary products of gene translation (Brady, 1987). It is improbable that one single enzyme is responsible for the changes in firmness. It is more likely that a complex interaction of enzymes is involved, including the ones that degrade starch (Tucker, 1993). Pectin methylesterase and polygalacturonase Aziz and Yusof (1994) only reported that there is activity of the PME enzyme in soursop fruit. However, Lima et al. (2006) quantified the activity, pointing out considerable increases over short periods of time, so that in the mature fruit the PME presented an activity that was twenty-three times larger than it was in the fruit at physiological maturity. Some studies have been carried out with the purpose to purify and characterize PME in soursop fruit, which is present in two isoforms (Arbaisah et al., 1996, 1997a, 1997b). Generally, it has been suggested that the function of the PME is to promote the desesterification of the galaturonanas in order to allow the action of the PGs (Giovane et al., 1990; Kays, 1997). The PGs are pectolytic enzymes identified as endo-PGs (E.C. 3.2.1.15) and exo-PGs (E.C. 3.2.1.67). The endo-PG catalyzes the random hydrolytic break of the α-(1–4) bonds of the galacturonanas. The exo-PG, on the other hand, hydrolyzes the terminal galacturonosil residues of the non-reducing extremities of the molecule, liberating galacturonic acid (John and Dey, 1986; Seymour and Gross, 1996; Kays, 1997). The activity of PG has been observed in several fruits (Abu-Sarra and AbuGoukh, 1992; Ketsa and Daengkanit, 1999), where an increase during softening can be verified, possibly triggered by the ethylene production. The enzyme promotes the degradation of the middle lamella of the parenchyma cells, thus resulting in softening. Also, it may be involved in the autocatalytic liberation of uronic acids during the growth of certain fruits (Gallego and Zarra, 1998), in the degradation of solubilized pectic polymers during ripening (Redgwell et al., 1992), and in the depolymerization of polyuronides (Yoshioka et al., 1992). In soursop fruit, Aziz and Yusof (1994) reported a sudden increase in the PG activity on the occasion of the climacterium. Lima et al. (2006) observed that, after the increase, the reduction in the activity of this enzyme coincides with a sudden drop in the pectin content and with a higher solubility of the pectins, indicating that the greatest part of the PG substrates was immediately used at the moment of maximum activity. α- and β-galactosidases Lima et al. (2006) observed that the activities of the α-GALs extracted from the cytosol and from the cell wall of soursop fruit occurred from the second day after

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harvesting. The activity of the cytosol α-GAL in particular reached its highest value on the third day, followed by a 60% decrease. As to the activity of the αGAL extracted from the cell wall, it was lower and decreased from the second day after harvesting, so that it represented continuously smaller proportions of the total α-GAL activity, suggesting that it might be of secondary importance in the softening of soursop fruit. In its turn, β-GAL removes galactosil residues from the non-reducing ends of cell wall polymers. Its role in ripening is not yet quite clear, but some studies have emphasized its importance in softening (Burns, 1990; Ali et al., 1995; Seymour and Gross, 1996; Gallego and Zarra; 1998). Ali et al. (1995) point it out as a key enzyme in pectin modification, and perhaps it complements the action of PG. Ranwala et al. (1992) associate it with the modification of pectic polymers and hemicellulosic components. On the other hand, in some fruit, the β-GAL is not likely to be involved in softening (Ketsa and Daengkanit, 1999). In soursop fruit, the activity of β-GAL from cytosol is higher than the one of β-GAL from the cell wall, although it decreases during ripening, indicating that the enzyme may be exported to the cell wall (Lima et al., 2006). The activity of the enzyme extracted from the cell wall increases during the first four days after harvesting and represents the highest proportion in the total β-GAL activity during the ripening of soursop fruit. The mechanisms that are responsible for the liberation of galactosil residues are relevant not only due to the modification they promote in the cell wall, but also because of their role in the modulation of the galactose levels, which seemingly are important to the ripening process as a whole (Seymour and Gross, 1996). Considering that soursop fruit undergoes progressive softening as it ripens, the enzymes that are likely to contribute more directly to the process are PME, PG and cell wall β-GAL. The importance of the latter two has to be pointed out, given that the intensity in which the softening occurs diminishes in the course of time. Therefore, it is expected that the activity of the involved enzymes be reduced as the process evolves. In a first moment, the PG acts in a more effective way. However, the precocious drop of activity suggests that β-GAL from the cell wall characterizes better this transformation (Lima et al., 2006). Amylase Paull et al. (1983) determined the activity of amylase prior to the climacterium and in the mature soursop fruit, observing an increase of almost eighteen times from one stage to the other. Lima et al. (2006) emphasized the increase in amylase activity from the harvest until the fourth day, when starch contents equivalent to 25% of the initial were reached, the enzymatic activity stabilized. The response is coherent with the high starch breakdown rate in the fruit. Polyphenol oxidase (PPO) and peroxidase (POD) The activity of the PPO changes considerably during the development, ripening and storage of the fruit (Mayer and Harel, 1981). According to Silva (2000), the activity is highest during the development. Results obtained by Oliveira et al. (1994) confirm

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this tendency for soursop fruit. Nevertheless, Lima et al. (2003a) observed an increase during the first four days after harvesting. These differences may be associated with the methods of extraction and quantification, as in the study by Oliveira et al. (1994) the specific activity of the enzyme was represented (based on the protein content), while Lima et al. (2003a) represented the total activity. Carbonaro and Mattera (2001) emphasized that the PPO activity is influenced by the cropping conditions. Moreover, the increase in activity of this enzyme, as well as the appearance of isoenzymes, is due to the de novo synthesis (Mayer and Harel, 1979). The enzymatic browning of fruit may be avoided by inactivating the PPO, using ascorbic acid, SO2 or heating (Badrie and Schass, 2009), or by reducing the quinones to phenols through reducing agents (Awad, 1993). The PODs, in their turn, play a limited role in enzymatic browning as they depend on the availability of hydrogen peroxide (Robards et al., 1999). However, the phenolic substrates can be oxidized in the presence of small quantities of hydrogen peroxide, and several compounds are susceptible to oxidation by these enzymes (Robinson, 1991). The activity of POD in soursop fruit is still high right after harvesting, but turns severely reduced in the period from the second to the fourth day (Lima et al., 2003a). Moreover, in contrast to many fruits, the activity of the POD is higher than the one of PPO, in these periods of great increments. 18.3.10 Aroma compounds The production of volatile compounds in soursop fruit is parallel to the one of ethylene, reaching the highest level five days after harvesting, on the same occasion that the highest sugar and acid levels can be verified (Paull et al., 1983), as well as the maximum sensorial preference. After the peak there is a drop in production of the main aroma compounds and volatiles appear to which the strange odor of the overripe fruit is imputed (Paull et al., 1983). The same tendency is observed in relation to sugars and organic acids. The prevailing compounds identified in soursop aroma after solid phase microextraction (SPME) were a-unsaturated methyl ester of the type R-CH5CHCOOCH3 (rethyl, butyl, hexyl) as methyl crotonate (rethyl), methyl 2-hexenoate (rbutyl), and methyl 2-octenoate (rhexyl) as well as aliphatic esters of butyric and caproic acids (Augusto et al., 2000). Using gas chromatography/spectroscopic (GC/FID and GC/MS), esters of aliphatic acids were dominant odor compounds (approximately 51%), with 2-hexenoic acid ethyl ester (8.6%), 2-octenoic acid methyl ester (5.4%) and 2-butenoic acid methyl ester (2.4%) in essential oil extracted from soursop pulp (Jirovetz et al., 1998). In addition, mono-and sesquiterpenes such as β-caryophyllene (12.7%), 1,8-cineole (9.9%), linalool (7.8%), α-terpineol (2.8%), linalyl propionate (2.8%), linalyl propionate (2.2%) and calarene (2.2%) are highly concentrated in the essential oil. The major volatiles identified by simultaneous distillation/solvent extraction and GC/MS analysis were methyl 3-phenyl-2-propenoate, hexadecanoic acid, methyl (E)-2hexenoate, and methyl 2-hydroxy-4-methyl valerate (Pino et al., 2001).

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(Z)-3Hexen-1-ol was the main volatile present in mature green fruit, while Me (E)-2-hexenoate, Me (E)-2-butenoate, Me butanoate, and Me hexanoate were the four main volatiles present in ripe fruit. The main compounds in the essential oil of the fresh soursop pulp were responsible for the esters of aliphatic acids dominated (~51%) with 2-hexenoic acid methyl ester (23.9%), 2-hexenoic acid ethyl ester (8.6%), 2-octenoic acid methyl ester (5.4%), and 2-butenoic acid methyl ester (2.4%) (Jirovetz et al., 1998).

18.4

Preharvest factors affecting fruit quality

Fruit quality depends mostly on cultural practices. Besides, there is a great variation in fruit size and quality among plants, due to seed propagation. For this reason vegetative propagation is recommended, as it represents an efficient way to obtain highly productive plants and high quality fruits (Filgueiras et al., 2002). According to the authors, the main factors that affect the soursop fruit quality are: genetics; environmental conditions (climate, cropping conditions, insolation, irrigation and proper plant nutrition, agrochemicals); proper pollination; harvest methods; and condition and physiological age of the fruit at harvest. In Brazil, for example, production problems have included low fruit set due to poor pollination and adverse climatic conditions and the attack of several devastating pests and diseases. The most important pests are the fruit borer, Cerconota anonella Sepp, the seed borer, Bephratelloides maculicollis Bondar, the stem borer, Cratosomus spp., the ‘irapua’ bee Triogona spinips, the leafminer, Prinomerus anonicola Bondar, and some species of Membracidae, Coccidae, Diaspididae, and Aphididae (Braga Sobrinho et al., 1998). The main pest of the soursop fruit in the West Indies is the mealy bug (Maconellicoccus hirsutus). Soursop fruit is subject to attack by soursop fruit flies, and red spiders are a problem in dry climates (Badrie and Schauss, 2009). The most serious diseases in soursop fruit are caused by fungi, which assume an important character in the phases of blooming, fructification and post-harvest. The ones which stand out are anthracnose, caused by Colletotrichum gloeosporioides Penz., brown rot (Rhizopus stolonifer Soc.) and bark rot, caused by Lasiodiplodia theobromae (Pat), which rapidly invades the flesh, becoming brown and corky, but can be associated to Phomopsis sp. and Colletotrichum sp. Black canker caused by Phomopsis anonacearum occurs in the wet season, purple spots occurring at or near the distal end. As the lesions enlarge, the surface becomes hard and cracked (Filgueiras et al., 2002; Badrie and Schauss, 2009). Both the pests and the diseases that attack soursop and their fruits damage the quality in different intensities. In some cases, the damage is restricted to the skin and does not affect the taste or pulp integrity. When the appearance is affected, there is a commercial depreciation regarding the fresh fruit market but the fruit can still be destined to the industry. On the other hand, more severe damage can

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prevent the fruit commercialization, on any market, once they affect fruit appearance, composition, and even result in fermentation.

18.5

Postharvest handling factors affecting quality

As it is a very perishable fruit, soursop fruit requires care in handling, from harvest to consumption, and in transit which is decisive to its conservation. The importance of this care is only the greater because of the scarcity of information on storage techniques that provide fruit quality support over the longest possible period. The quality of a fruit can be understood as absence of defects or degree of excellence, involving sensorial, nutritional, as well as food safety aspects (Shewfelt, 1999). In the case of soursop fruit, according to Borrero et al. (1995), good quality is achieved when harvest occurs at the correct maturity stage. If harvested immature, soursop fruit present an irregular maturation, which seriously compromises its quality. When harvested ripe, they do not resist prolonged storage and losses occur. Alterations in quality occur, for fruit in general, mainly as a result of physiological changes (Shewfelt, 1999). Several other factors are involved in quality, such as pulp browning. The phenomenon may be of enzymatic nature or not, but in both cases it results from melanin formation. The main differential is the fact that the non-enzymatic browning requires external heat, while the enzymatic one may occur at room temperature (Silva, 2000). The main postharvest problems were due to deficient field practices and lack of knowledge on the fruit quality parameters by fruit growers. Also, inappropriate handling during the commercialization process increases the loss (Badrie and Schauss, 2009). To reduce these problems, appropriate storage and handling techniques are essential. The use of techniques which delay ripening might prolong the conservation period of soursop fruit, preserving the quality characteristics that are peculiar to the fruit. 18.5.1 Temperature management The importance of maintaining ideal packaging conditions for the fruit guarantees maximum quality preservation. For fruit with a reduced shelf life, as soursop fruit, storage at appropriate temperatures widen the possibility of commercialization on new markets, even though it may not be possible to achieve the improvement that has been made in extending the conservation period of other fruits (Maciel et al., 1994; Livera and Guerra, 1995; Mosca, 1996; Silva et al., 2001; Lima et al., 2003b, 2006). The desirable situation corresponds to cooling the fruit, in the shortest possible time, to a temperature that reduces its metabolic activity without causing chilling injury, and to the maintenance of the cold storage chain during all stages of commercialization. The interruption of cold storage, apart from accelerating fruit metabolism, allows the condensation of vapor around the fruit, turning its surface vulnerable to infection by microorganisms present in the storage environment. The

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problem becomes more serious when soursop fruit is ripe, because it develops an opening around the stalk and the peel ruptures easily when touched or in contact with too rigid and coarse surfaces. Even temperature variations due to cooling system faults, or negligence in entering and exiting cargo to and from the cold chamber, reduce the desired storage period and the shelf life of soursop fruit. 18.5.2 Physical damage Care in handling and transport reduces or even avoids the occurrence of injuries. In soursop fruit, physical damage due to fall, vibration, friction or compression results in a dark coloration of the peel. This alteration in color depreciates the fruit (Zayas, 1966) and may accelerate the maturation and facilitate the infection by microorganisms, depending on the intensity. Moreover, inappropriate handling increases weight loss, which may significantly affect textural quality during the postharvest period (Kays, 1997). 18.5.3 Water loss After harvesting, alterations in fruit weight are mainly due to water loss. A weight loss of merely 5% may cause withering and shriveling in many perishable products (Wills et al., 2007). Nevertheless, water losses that result in a weight loss percentage of 4.6 (Lima et al., 2003b) or 5.1, as shown in Fig. 18.4, and up to 11.8 (Mosca et al., 1997) did not result in shriveling or other visible signs of withering in soursop fruit. The spurs, however, became flaccid more rapidly and turned dark.

Fig. 18.4 Weight loss of ‘Crioula’ soursop fruit harvested at physiological maturity and stored under room temperature. Source: Adapted from Lima et al. (2003a).

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18.5.4 Atmosphere The lack of scientific information and the peculiarities of soursop fruit limit the availability of efficient techniques which might allow its quality preservation for a period of time that would be considered minimum for many other fruits. Therefore, there are no defined conditions to ensure the viability of storage under controlled atmosphere, for instance. Likewise, even though the quick and high response to ethylene might justify an intervention with substances that absorb or inhibit this gas, there is no commercial application. Some studies have experimentally tested the application of the ethylene inhibitor 1-methyl cyclopropane (1-MCP) in soursop fruit (Lima et al., 2002a, 2004). Some more detailed information considers the use of coatings and modified atmosphere packaging (Guerra et al., 1995; Silva et al., 2001; Lima et al., 2004).

18.6

Physiological disorders

Physiological disorders that affect soursop fruit during its growth, development and maturation phases have not been recognized. There are only records of the possibilities of chilling and heat injury occurrence from harvest on, under specific packaging conditions that might expose them to the causes of these disturbances. 18.6.1 Chilling injury Although the inferior limit for the normal metabolism is the tissue’s freezing point, some species show symptoms of chilling injury even in temperatures above that point (Luchsinger, 1999; Wills et al., 2007). The symptoms of chilling injury in soursop fruit are skin darkening, failure to ripen, pulp discoloration, poor flavor and aroma, maintenance or increase of pulp firmness, internal breakdown, loss of ripening capability, senescence acceleration, increase in rot, etc. (Maciel et al., 1994; Salgado et al., 1998; Badrie and Schauss, 2009). The occurrence of this damage depends on the species, the cultivar, the maturity stage and the cropping conditions (Luchsinger, 1999). In soursop fruit, chilling injuries at 12 °C were reported by Maciel et al. (1994), Mosca (1996) and Salgado et al. (1998). Filgueiras et al. (2002) have mentioned temperatures below 15 °C as resulting in the appearance of chilling injury symptoms, which are more evident in physiologically mature fruits. 18.6.2 Heat injury Heat injuries are caused by the exposure to very high temperatures (above 27 °C), which can result in internal breakdown. The transformations that occur during fruit ripening can be modified by the excessive heat, with consequences to the appearance, sugar content, acidity and aroma. This kind of disorder is prevented by avoiding any unnecessary exposure of the fruits to heat, keeping them always

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in the shade while they are in the orchard, lowering the field heat as quickly as possible and controlling the storage temperature (Filgueiras et al., 2002).

18.7

Pathological disorders

As mentioned before, the main pathological disorders that attack soursop fruit are caused by fungi. They occur in the phases of blooming, fructification and postharvest. The most important are anthracnose, brown rot and bark rot, which rapidly invades the flesh, becoming brown and corky, but can be associated with Phomopsis sp. and Colletotrichum sp. Black canker occurs in the wet season as purple spots occurring at or near the distal end. These lesions enlarge and the surface becomes hard and cracked (Filgueiras et al., 2002; Badrie and Schauss, 2009).

18.8

Postharvest handling practices

The limited knowledge of the fruit physiology and the restricted market have not yet allowed the adoption of more sophisticated postharvest procedures or techniques for soursop fruit. Thus there is a need for special care during harvest, when occasional damage may affect and reduce its shelf life. 18.8.1 Harvest operations In the soursop orchard, the fruits do not ripen at the same time. Therefore, it is necessary to visit it frequently in order to identify fruits which have reached harvest point. The harvest should be done manually with disinfected pruning scissors with curved, sharp blades and rounded, blunt tips, in order not to damage the fruit (see Plate XXXIV in the colour section). The cut should leave a peduncle of 1.0 cm approximately. Considering the large size of the fruit it is recommended that the soursop fruit be carefully held in one hand, while the scissors are used with the other. Harvest should be done in the first hours of the day, avoiding the hot periods, which could heat the fruit and result in the browning of the spurs when touched. Once harvested, the fruit should be put in boxes covered with soft and flexible material with the stalk facing downwards and slightly inclined, and kept protected from the sun, rain and dust until taken to the packinghouse. It is also advisable to protect the fruits with paper or other soft material to avoid friction between fruits in the same harvest box. When more than one layer of fruits is used in the same box they should be separated by a sponge (Alves et al., 2002). The care already mentioned should be maintained during the transport to the packinghouse, preventing for instance excessively full boxes which may cause fruit damage while piling them into the vehicle.

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18.8.2 Packinghouse practices The postharvest operations for soursop fruit destined to the fresh fruit market include washing, drying, grading and sizing, packaging, pre-cooling and storage, as described next (Alves et al., 2002).

•

• •

•

•

Washing: in the packinghouse, the fruits should be washed with chlorinated water (100–200 mg.L−1 of free chlorine) so as to remove dirt, microorganisms and superficial residues. To achieve efficiency in this procedure, it is necessary to change the water periodically and pay special attention to temperature and pH, factors that determine the efficiency of the chlorine. After washing, the fruits must be dried before initiating the following stages. Grading and sizing: the selection is manual, eliminating immature, very ripe, or deformed fruits and as well those with stains or mechanical injuries. The fruits which are good for commercialization are classified according to the weight. Packing: in this stage occurs the most serious negligence with the quality of the soursop fruit, which in most of the cases is commercialized without any protection. Technically, it is recommended that individual fruits are wrapped in paper bags or polyethylene nets and arranged in cardboard boxes suitable for soursop fruit sizes. Pre-cooling: when cold storage is used, it is necessary that, prior to the storage in the cold chamber, fruits are rapidly cooled down, in specific tunnels, so that within a short period of time (4–6 hours) the pulp reaches the recommended storage temperature of 15 °C. The operation is carried out in tunnels that also keep the relative humidity in levels that are favorable to the fruit (85–95%, preferentially at 90%). When pre-cooling is accomplished, fruits will be kept in the cold chamber until the moment of distribution. Refrigerated storage: the cold chamber must keep the temperature and relative humidity at the ideal levels in which fruits were received after pre-cooling. From then on, cold chain must be maintained, as a requirement for the soursop fruits reaching their longest possible shelf life.

18.8.3 Control of ripening and senescence Few studies have been carried out on the use of MA for soursop fruit. Guerra et al. (1995) and Maciel et al. (1994) have tested, respectively, the use of sugar ester and fatty acid pellicles and polyethylene films involving the packing boxes of soursop fruit stored at 16 °C. However, fruits did not ripen normally. Promising results were obtained by Silva et al. (2001), when using flexible polyethylene films in individual soursop fruit packing on polystyrene trays, stored at 12 °C and at 14 °C. Fruits stored at 12 °C under MA sustained a good quality for up to 22 days. The fruit ripening may be delayed through the use of inhibitors of ethylene production and action (Abdi et al., 1998). Among these, we can highlight the cyclopropenes: antagonist gases to ethylene, which compete with this hormone

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for the binding sites in the membrane receptors. Among the three cyclepropene compounds (cyclepropene, 1-MCP and 3,3-dimethyl cyclopropene) that act as ethylene-action inhibitors, the second has concentrated most of the studies, due to its activity and stability (Sisler and Serek, 1997). Its application to soursop fruit is only experimental and requires further studies. Lima et al. (2002a, 2004) observed some delay in ripening due to the application of 1-MCP to soursop fruit stored at room temperature or under cooling, but the duration is short, when compared to what is observed for other fruits. 18.8.4 Recommended storage and shipping conditions The ideal storage conditions correspond to those where the products can be stored for the longest possible time, without considerable loss of their quality attributes, like flavor, aroma, firmness, color and humidity content. Among the available conservation methods, cooling is the most used and efficient for the storage of fruits and vegetables (Chitarra and Chitarra, 2005). Some studies carried out with soursop fruit reported that at temperatures of 22–23 °C, the fruits ripened in up to six days (Maciel et al., 1994; Mosca, 1996; Lima et al., 2003b). Raising the temperature to 26 °C, the shelf life was only five days (Lima et al., 2006). On the other hand, on reducing the temperature to 21 °C, Livera and Guerra (1995) observed that the fruits reached consumption conditions in up to seven days. When the storage temperature was 15 °C, Mosca (1996) concluded that the time needed for ripening increased to nine days. In lower temperatures, like 12 °C and 14 °C, Silva et al. (2001) observed that the fruit was already improper for commercialization on the sixth day. In general, storage time depends on the respiratory activity of the product, on susceptibility to humidity loss and on pathogen resistance (Wills et al., 2007). The latter two depend on the environmental relative humidity. High humidity levels favor the development of microorganisms and low ones foster physiological disorders and uneven maturation, besides the loss of turgescence. Associated with cooling, the application of wax based on polyethylene emulsion, containing also fumaric resins, preservative and water, reduces the soursop fruit mass loss and delays the increase in soluble solids content and firmness loss during soursop fruit cold storage at 15 °C and 86% RH (Lima et al., 2004, 2010). The delay in firmness loss, specifically, occurs in the period of the greatest biochemical changes in soursop fruit, along with, for example, the increase in the activity of β-galactosidase and the first CO2 peak. The mentioned effects were obtained through the application of 200 nL.L−1 of 1-MCP for 12 hours (Lima et al., 2010). This ethylene inhibitor was responsible for the delay of the respiratory peak and the limited ethylene production in soursop fruit. When sprayed in association with wax, the effects of keeping the amylase activity stable and reducing the PG activity were added. In both cases, the commercial appearance of the fruits was preserved for eleven days, at 15 °C. However, the spraying of wax allowed a lower weight loss for 15 days of evaluation and an acceptable consumption appearance for 13 days.

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18.9

Conclusions

The intense metabolic activity of soursop fruit during maturation results in a very short period of postharvest conservation. In general, the changes are abrupt and some of them are related to the climacteric peak. Recently, some of those changes, including enzymatic activity, have been studied, detailing responses that can contribute to define more efficient techniques, procedures and methods of postharvest conservation for soursop fruit. However, just a few researchers are dealing with this fruit and there are many unknown physiological and technological aspects. Even the correct identification of the physiological maturity is not easy or secure in some genetic materials. The relatively distinct respiratory metabolism of soursop fruit require biochemical studies to find the key steps that stimulate the events related to organic acids accumulation, firmness loss and starch breakdown, for example. Pulp browning is another event that has importance when the fruit is destined to the industry. Likewise, techniques of molecular biology could be useful to increase the knowledge about soursop fruit metabolism. Then, there is a great opportunity to explore scientifically the soursop fruit behavior in remarkable phases, especially after the harvest on physiological maturity. Careful handling during harvest and postharvest operations, besides an adequate adoption of cultural practices, including phytosanitary control are needed. The latter is a critical point in some producing regions where pest control is difficult. Then, efforts are necessary to propose an efficient integrated management of pests and diseases, contributing to the fruit quality. Regarding postharvest technologies, the improvement on adopted techniques and the recommendation of others depend on getting an established knowledge about the physiology and biochemistry of the fruit.

18.10

References

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Lima M A C de, Alves R E and Filgueiras H A C (2003a), ‘Avaliação da qualidade e da suscetibilidade ao escurecimento oxidativo de graviola (Annona muricata L.) durante a maturação pós-colheita’, Proc Interamer Soc Trop Hort, 46, 23–26. Lima M A C de, Alves R E, Filgueiras H A C and Enéas-Filho J (2003b), ‘Comportamento respiratório e qualidade pós-colheita de graviola (Annona muricata L.) “Morada” sob temperatura ambiente’, Rev Bras Frut, 25, 49–52. Lima M A C de, Alves R E, Filgueiras H A C and Lima J R G (2004), ‘Uso de cera e 1-metilciclopropeno na conservação refrigerado de graviola (Annona muricata L.)’, Rev Bras Frutic, 26, 433–437. Lima M A C de, Alves R E and Filgueiras H A C (2006), ‘Mudanças relacionadas ao amaciamento da graviola durante a maturação pós-colheita’, Pesq Agropec Bras, 41, 1107–1713. Lima M A C de, Alves, R E and Filgueiras H A C (2010), ‘Comportamento respiratório e amaciamento de graviola (Annona muricata L.) após tratamentos pós-colheita com cera e 1-metilciclopropeno’, Ciênc Agrotec, 34, 155–162. Livera A V S and Guerra N B (1996), ‘Desenvolvimento físico da graviola’, Rev Bras Frutic, 18, 225–233. Livera A V S and Guerra N B (1995), ‘Determinação da maturidade comercial da graviola (Annona muricata L.) através de um disco de coleta’, in XIV Congresso Brasileiro de Fruticultura, Resumos . . ., 603–604. Luchsinger L E (1999), ‘Problemas de oscurecimiento interno en frutas por efecto de tratamientos postcosecha’, in Alves R E and Veloz C S, Exigências quarentenárias para exportação de frutas tropicais e subtropicais, Fortaleza, Embrapa – CNPAT/CYTED/ CONACYT, 183–190. Maciel M I S, Guerra N B and Tavares M O C (1994), ‘Ensaio preliminar sobre a conservação da graviola (Annona muricata L.)’, Bol Soc Bras Ciênc Tecn Alim, 28, 64–68. Martin-Cabrejas M A, Waldron K W, Selvendran R R, Parker M L and Moates G K (1994) ‘Ripening-related changes in the cell wall of Spanish pear (Pyrus communis)’, Physiol Plant, 91, 671–679. Mayer A M and Harel E (1979), ‘Polyphenol oxidases in plants’, Phytochem, 18, 193–215. Mayer A M and Harel E (1981), ‘Polyphenol oxidades in fruits – changes during ripening’, in Friend J and Rhodes M J C, Recent advances in the biochemistry of fruits and vegetables, London, Academic Press, pp. 161–180. Mayer A M and Harel E (1991), ‘Phenoloxidases and their significance in fruit and vegetables’, in Fox P F, Food Enzimology, London, Elsevier Applied Science, v1, 373–398. McCollum T G, Huber D J and Cantliffe D J (1989), ‘Modification of polyuronides and hemicelluloses during muskmelon fruit softening’, Physiol Plant, 76, 303–308. Ministerio del Trabajo y Seguridad Social (1995), ‘Curso Manejo Postcosecha de Guanábana (Annona muricata L.)’, Colombia, SENA. Mororó R C, Freire E S and Sacramento C K (1997), ‘Processamento de graviola parfa obtenção de polpa’, in Vilas-Boas A R S I, Morais, O M J and Rebouças T N H, Anonáceas: produção e mercado (pinha, graviola, atemóia e cherimólia), Vitória da Conquista, Universidade Estadual do Sudoeste da Bahia, 263–274. Morton J F (1987), ‘Soursop’, in Morton J F, Fruits of Warm Climates, Greensboro, Media Incorporated, pp. 75–80. Mosca, J L (1996), ‘Estudos de maturação e práticas pós-colheita para conservação de frutos de anonáceas in natura’, Fortaleza, EMBRAPA-CNPAT. (Report). Mosca J L, Alves R E, Filgueiras, H A C and Oliveira J F de (1997), ‘Determination of harvest index for soursop fruits (Annona muricata L.)’, in I Congreso Internacional de Anonaceas, Memorias . . ., Chapingo, Universidad Autónoma Chapingo, 315–322. Moura J V de (1988), ‘A cultura da graviola em áreas irrigadas: uma nova opção’, Fortaleza, DNOCS.

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Silva S M, Martins L P, Santos J G dos S and Alves R E (2001), ‘Conservação pós-colheita de frutos de graviola (Annona muricata L.) sob atmosfera modificada’, Rev Iberoam Tecn Postc, 4, 6–12. Sisler E C and Serek M (1997), ‘Inhibitors of ethylene responses in plants at the receptor level: recent developments’, Physiol Plant, 100, 577–582. Tucker G A (1993), ‘Introduction’, in Seymour G B, Taylor J E and Tucker G. A, Biochemistry of Fruit Ripening, London, Champman & Hall, pp. 1–51. Umme A, Bambang S, Salmah Y and Jamilah B (2001), ‘Effect of pasteurization on sensory quality of natural soursop puree under different storage conditions’, Food Chem, 75, 293–301. Umme A, Salmah Y, Jamilah B and Asbi B A (1999), ‘Microbial and enzymatic changes in natural soursop puree during storage’, Food Chem, 65, 315–322. Universidade Federal de Uberlândia. 2010. Anonáceas. Available from: http://www. fruticultura.iciag.ufu.br/anonaceas.htm#Mercado (accessed 20 January 2010). Ventura M M and Hollanda-Lima I (1961). ‘Ornithine cycle amino acids and other free amino acids in fruits Annona squamosa L. and Annona muricata L’, Phyton, 17, 39–47. Wakabayashi K (2001), ‘Changes in cell wall polysaccharides during fruit ripening’, J Plant Res, 113, 231–237. Wenkman N S and Miller C D (1965), ‘Composition of Hawaii fruit’, Hawaii: Hawaii Agriculture Experimental Station, University of Hawaii Bulletin. Whiting G C (1970), ‘Sugars’, in Hulme A C, The Biochemistry of Fruits and their Products, New York, Academic Press London, v1, 1–31. Wills R B H, Mcglasson W B, Graham D and Joyce D C (2007), Postharvest: An Introduction to the Physiology and Handling of Fruit, Vegetables and Ornamentals, Wallingford, New South Wales University Press. Worrell D B, Carrington C M S and Huber D J (1994). ‘Growth, maturation and ripening of soursop (Annona muricata L.) fruit’, Scient Hortic, 57, 7–15. Yoshioka H, Aoba K and Kashimura Y (1992), ‘Molecular weight and degree of methoxylation in cell wall polyuronide during softening in pear and apple fruit’, J Amer Soc Hortic Sci, 117, 600–606. Zayas J C (1966), ‘Las frutas anonaceas’, Havana, Ediciones Fruticolas.

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(a)

(b)

Plate XXXIII

(Chapter 18) Soursop fruit at physiological maturity (a) and ripe (b). Photos: Maria Auxiliadora Coêlho de Lima.

Plate XXXIV

(Chapter 18) Soursop fruit at harvest time. Photo: Maria Auxiliadora Coêlho de Lima.

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19 Star apple (Chrysophyllum cainito L.) E. M. Yahia and F. Gutierrez-Orozco, Autonomous University of Queretaro, Mexico

Abstract: Star apple is a non climacteric fruit, with high antioxidant capacity and high nutritional and health potential. However, this fruit is only commercially produced on a very limited scale in a few regions. Extensive research is still needed on diverse aspects of postharvest physiology, biochemistry and technology. This chapter discusses the currently available information on the postharvest handling of this fruit. Key words: Chrysophyllum cainito, star apple, postharvest, nutrition, health, quality, processing, storage.

19.1

Introduction

Although star apple (Chrysophyllum cainito L.) fruit are very tasty, their commercial importance is lower than that of other fruits from the same family (Sapotaceae). Mainly consumed fresh, star apple fruit has a great potential in international markets due to its flavor and appearance which make it very suitable for inclusion in salads as an exotic fruit. The fruit has been found to contain antioxidants in a recent study which increases opinion of its nutritional value.

19.1.1 Origin, botany, morphology and structure From the Sapotaceae family, the star apple (Chrysophyllum cainito L.), also called caimito, goldenleaf tree, sweetsop, or anon, is believed to be native to Central America, although others consider that it may be indigenous to the West Indies. It is well distributed at low and medium altitudes from the south of Mexico to northern Argentina and Peru. In the United States, it grows well only in the warmest locations in southern Florida. The star apple is an evergreen tree that grows up to 15 m with a short trunk of diameter 60 cm. The crown is dense, broad and the bark exudates white gummy latex. Star apple tree is propagated through

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seeds but this can also be done through grafting (Alvarez et al., 2004). The leaves are elliptic to oblong and are glossy above and coated with silky hair beneath that is golden in color. The flowers are clustered in the leaf axils and range from a green-yellow color to purple and white. Star apple is an apple size fruit (see Plate XLII in the colour section between pages 238 and 239), commonly round, sometimes ovate, heart-shaped or conical, with a smooth and waxy skin. A star shape appears in its cross section. The fruit is characterized by its soft flesh that is yellowish green in color, with a mild sweet flavor. The pulp is white or creamy white, with numerous small, shiny, dark brown seeds embedded in it (Morton, 1987; Orwa et al., 2009). 19.1.2 Worldwide importance Star apple is commercially grown in Australia and Mexico (Morton, 1987). It is of minor commercial importance in the United States as compared to other Sapotaceae fruits despite its tasty flavor: only six acres, approximately, of commercially grown and harvested star apple exist in Florida. The price for a dozen star apple fruits was between one and a half and three dollars during production peak and fifteen dollars outside this period (Alia-Tejacal et al., 2005). 19.1.3 Culinary uses The fruit can be eaten fresh or chilled to improve the flavor. It is cut in half and the flesh is spooned out, discarding the seed cells and core. The skin is not edible and should be discarded. In the same way, special care must be taken to not let the skin latex come in contact with the flesh. In Jamaica, the frozen flesh is mixed with other frozen fruit and served as a salad. Fresh pulp can be mixed with sour orange juice or prepared into preserves. In other areas, a decoction can be prepared from the flesh, while others prepare an emulsion from the seed kernels. The nutritional value of star apple fruit is presented in Table 19.1. The flesh of star apple is very sweet with glucose being the main sugar (Heredia et al., 1998). The seeds have been reported to contain 1.2% of the bitter, cyanogenic glycoside, lucumin (Morton, 1987). Several polyphenolic compounds with antioxidant activity have recently been characterized in star apple fruit. For instance Luo et al. (2002) identified catechin, epicatechin, gallocatechin, epigallocatechin, quercetin, quercetrin, isoquercitrin, myricitrin and gallic acid in the fruit. The following phenolic compounds were identified by Fujuki et al. (2010): chlorogenic, syringic, ferulic, benzoic, p-coumaric, vanilic, caffeic, gallic, and protocatechuic acids. This might support the finding that extracts of star apple showed high antioxidant capacity (Luo et al., 2002; Einbond et al., 2004). Epicatechin was found as the main polyphenol present in the fruit while quercetin had the highest antioxidant activity (Luo et al., 2002). In addition, cyanidin-3-O-β-glucopyranoside, an anthocyanin with antioxidant properties was identified in the fruit (Einbond et al., 2004).

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Postharvest biology and technology of tropical and subtropical fruits Table 19.1 Nutrient value of star apple fruit (100 g of fruit) Constituent

Approximate value

Water content Calories Protein Carbohydrates Total sugars Fiber Ash Calcium Phosphorus Iron Carotene Thiamin Riboflavin Niacin Ascorbic acid Tryptophan Methionine Lysine Total volatiles Total phenols

78.4–85.7 % 67.2 0.72–2.33 g 14.65 g 8.45–10.39 g 0.55–3.30 g 0.35–0.72 g 7.4–17.3 mg 15.9–22.0 mg 0.30–0.68 mg 0.004–0.039 mg 0.018–0.08 mg 0.013–0.04 mg 0.935–1.340 mg 3.0–15.2 mg 4 mg 2 mg 22 mg 0.154 mg 217.0–387.1 mg

Source: Morton (1987); Pino et al. (2002); Alvarez et al. (2006), Parker et al. (2010).

Differences may exist between cultivated and wild trees of star apple regarding acidity, pH, total soluble phenols, and sugar concentration. Total soluble phenols content has been reported in the range of 217.0 to 387.1 mg 100 g−1, depending on whether the fruit is from wild or cultivated trees, respectively (Parker et al., 2010). Analysis of volatile components of star apple have revealed 104 compounds, from which (E)-2-hexenal, 1-hexanol, limonene, linalool, α-copaene and hexadecanoic acid were found to be the major constituents. Altogether, these compounds contribute to the pleasant flavor of the star apple fruit (Pino et al., 2002). Ripe fruit of star apple are eaten to alleviate inflammation of the respiratory tract, and used as a treatment for diabetes and to ease angina. Unripe fruit are consumed to cure intestinal problems but if taken in excess can cause constipation. Decoctions of the leaves are used as a treatment for cancer and as a pectoral (Morton, 1987; Orwa et al., 2009). Seeds are taken as a powder and in other areas as a tonic and stimulant, to stop diarrhea, bleeding or gonorrhea. The latex is used as a vermifuge (Morton, 1987). An aqueous decoction of star apple leaves are used to treat diabetes. In a recent study with rabbits, this aqueous decoction was found to have hypoglycemic activity when used at doses greater than 10 g L−1 although toxic effects were present at a dose of 30 g L−1. These effects were attributed to the alkaloids, sterols and triterpens found in the plant (Koffi et al.,

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2009). Another study showed that extracts of star apple leaves were able to inhibit E. coli in vitro (Medina et al., 2001).

19.2

Fruit development and postharvest physiology

19.2.1 Fruit growth, development and maturation Growth of star apple fruit follows a sigmoidal system (Santamaria Herreria, 2004). Fruit must mature on the tree before they can be harvested and maturation takes about 180 days (Pino et al., 2002). Total soluble solids content in ripe fruit can reach up to 11.7 °Brix with an average value of 10.1 °Brix and ranges of pH in ripe fruit are from 5.42 to 6.18. At maturity, 60% of the fruit weight corresponds to the skin, 37% to the pulp and 3% to the seeds. The majority of the fruit found in Morelos, a central state in Mexico, present dark purple skin color, although green fruit may also be found. Thus, great variation exists in color parameters of star apple fruit (Table 19.2), although apparently dark purple colored fruit are preferred, at least in this area of Mexico (Alvarez et al., 2006). Table 19.2 Color parameters in ripe fruits of star apple Color parameter

Mean value ± Standard deviation

Lightness Hue Chroma

29.2 ± 8.8 56.1 ± 30.7 8.6 ± 7.0

Source: Alvarez et al. (2006).

19.2.2 Respiration, ethylene production and ripening The star apple is a non-climacteric fruit (Yahia, 2004) and respiration rate at 20 °C is about 25–50 mg CO2 kg−1 hr−1. Heat evolution of the fruit is 1600 to 4400 BTU ton−1 day−1 equivalent to a respiration rate of 7–20 mg CO2 kg−1 day−1 at 3–6 °C. Ethylene production at 20 °C is 10–100 nL kg−1 hr−1 (Pratt and Mendoza, 1980).

19.3

Maturity and quality components and indices

Because not all fruit on a tree mature at the same time, it is difficult to establish a maturity index. Fruit harvested before they are fully ripe will have a poor, gummy, texture and an astringent taste in addition to presenting sticky latex which makes the fruit inedible (OFI-CATIE, 2010). Fruit can be picked when the base of the fruit is still green for easier transporting and to reduce physical damage (Sagarpa, 2010). Fully mature fruit present dull skin and are soft to the touch (Morton, 1987). In addition, a pale to dark purple color of the skin is seen in mature fruits.

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19.4

Postharvest biology and technology of tropical and subtropical fruits

Preharvest factors affecting fruit quality

Conditions during fruit growth will affect the composition of the fruit. For instance, differences have been found in total sugars, acidity, pH, and soluble phenols, between wild and cultivated trees of star apples. Higher sugar concentration, less acidity and lower phenolic content was found in fruits of cultivated trees of star apple when compared to wild trees (Parker et al., 2010). This could be due to the effects on domestication and selection of the cultivated trees.

19.5

Postharvest handling factors affecting quality

19.5.1 Temperature management Star apple fruits can be maintained at 3–6 °C for a few weeks (OFI-CATIE, 2010). 19.5.2 Physical damage Since the fruit needs to ripen on the tree, sometimes mature fruit fall to the ground and are then picked up, which commonly causes mechanical damage. 19.5.3 Water loss The fruit is very susceptible to water loss. Therefore the use of high relative humidity (90%) can help reduce water loss during storage and shipping of star apple (OFI-CATIE, 2010).

19.6

Physiological disorders

The fruit is slightly sensitive to chilling injury.

19.7

Pathological disorders

Pestalotia and Diplodia, which cause stem-end decay, are an important problem in the Philippines. Other important disorders attacking the leaves include Phomopsis sp., Phyllosticta sp., and Cephaleuros virescens (Morton, 1987).

19.8

Insect pests and their control

Sometimes, larvae of small insects such as the anona seed borer infect young fruit and emerge when the fruit ripens. Other insects include the twig borer, carpenter moth, mealy bugs, scales and fruit flies. Dacus dorsalis, a fruit fly, constitutes a serious problem since it makes the fruit inedible. Ripe fruit on the tree may be eaten by birds, bats or squirrels (Morton, 1987; Orwa et al., 2009).

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397

Postharvest handling practices

19.9.1 Harvest operations Fruit are usually harvested from late winter to early spring. An adult tree may produce up to 60 kg of fruit. Star apple fruit are hand-picked by cutting the stem (Morton, 1987).

19.9.2 Packinghouse practices The fruit is tray packed in fiberboard boxes of 4.5 kg capacity (McGregor, 1987). Precooling can be done by hydrocooling or forced-air cooling.

19.9.3 Control of ripening and senescence The fruit does not seem to respond appreciably to treatment with ethylene, propylene or ethephon at 1000 ppm (Pratt and Mendoza, 1980).

19.9.4 Recommended storage and shipping conditions In order to maintain a good quality, fruit must be kept at 3–6 °C and 90% RH. Under these conditions fruit present a shelf life of three weeks (Morton, 1987; Yahia, 2004), and can benefit further from an adequate modified atmosphere system (Yahia, 1998).

19.10

Processing

Star apple fruit are mainly consumed as fresh, however, sometimes the pulp can be preserved in jellies. The seed kernels may be used to prepare a drink to imitate milk of almonds, nougats and other confectionary products. Frozen pulp of star apple may be used to make ice cream and sherbets (Morton, 1987).

19.11

Conclusions

Star apple is a non climacteric fruit and is considered exotic. It has a very pleasant flavor and nice appearance because of its star shape when cut in half. Elaboration of processed products from star apple fruit is limited and the fruit is mainly consumed as fresh. Although a tropical fruit, star apple fruit are somewhat resistant to chilling injury and therefore low temperatures can be used to extend their postharvest life. Ethylene application has not shown significant effects. Several polyphenolic compounds with antioxidant activities have been found in the fruit which increase the nutritional value.

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19.12

References

Alia-Tejacal I, Colinas-Leon M T, Celis-Velasquez R, Lopez-Martinez V, Acosta-Duran C, et al. (2005), ‘Poscosecha durante el almacenamiento de caimito (Crisophyllum cainito L)’, Investigacion Agropecuaria, 2, 7–13. Alvarez B R J, Graterol C, Quintero I, Zambrano J, Materano W, Maffei M (2004), ‘Evaluacion de algunos métodos y practicas de propagación en caimito Crisophyllum cainito L. I. sexual’, Rev Fac Agron, 21(Supl. 1), 47–53. Alvarez V J E, Tejacal A I, Lopez Martinez V, Acosta Duran C M, Andrade Rodriguez M, et al. (2006), ‘Caracterizacion de frutos de caimito (Crysophyllum cainito L.) en el estado de Morelos’, Revista Chapingo, Serie Horticultura, 12 (2), 217–221. Einbond L S, Reynertson K A, Luo X D, Basileb M J, Kennelya E J (2004), ‘Anthocyanin antioxidants from edible fruits’, Food Chem, 84, 23–28. Fujuki T S, Tonin F G, Tavares M F M (2010), ‘Optimization of a method for determination of phenolic acids in exotic fruits by capillary electrophoresis’, Journal of Pharmaceutical and Biomedical Analysis, 51, 430–438. Heredia J B, Siller J H, Baez M A, Araiza E, Portillo T, et al. (1998), ‘Changes in the quality and content of carbohydrates in tropical and subtropical fruits at the supermarket level’, Proceedings of the Interamerican Society for Tropical Agriculture, 41, 104–109. Koffi N, Ernest A K, Marie-Solange T, Beigre K, Noel A G (2009), ‘Effects of aqueous extract of Chrysophyllum cainito leaves on the glycaemia of diabetic rabbits’, African Journal of Pharmacy and Pharmacology, 3(10), 501–506. Luo X D, Basile M J and Kenelly E J (2002), ‘Polyphenolic antioxidants from the fruits of Chrysophyllum cainito L. (star apple)’, J Agric Food Chem, 50, 1379–1382. McGregor B M (1987), Tropical Products Transport Handbook. United States Department of Agriculture, Office of Transportation, Agric. Handbook No. 688. Medina N P, Viernes J D, Gundran R S (2001), ‘Evaluation of some medicinal plants against Escherichia coli’, Philippine Journal of Veterinary Medicine, 38 (1), 9–14. Morton J (1987), ‘Star Apple’, in Morton J, Fruits of Warm Climates, Miami, FL, pp. 408–410. OFI-CATIE (2010), Crysophyllum cainito. Available from http://herbaria.plants.ox.ac.uk/ adc/downloads/capitulos_especies_y_anexos/chrysophyllum_cainito.pdf (accessed 20 May 2010). Orwa C, Mutua A, Kindt R, Jamnadass R and Anthony S (2009), Agroforestree Database: a tree reference and selection guide version 4.0. Available from http://www. worldagroforestry.org/sites/treedbs/treedatabases.asp (accessed 25 January 2010). Parker I M, Lopez I, Petersen J J, Anaya N, Cubilla-Rios L, Potter D (2010), ‘Domestication syndrome in caimito (Crysophyllum cainito L.): fruit and seed characteristics’, Economic Botany, 64 (2), 161–175. Pino J, Marbot R, Rosado A (2002), ‘Volatile compounds of star apple (Crysophyllum cainito L.) from Cuba’, Flavour Fragr J, 17, 401–403. Pratt H K, Mendoza D B Jr (1980), ‘Fruit development and ripening of the star apple (Chrysophyllum cainito L.)’, HortScience, 15(6), 721–722. Sagarpa (2010), Caimito. Available from http://w4.siap.sagarpa.gob.mx/AppEstado/ Monografias/Frutales/Caimito.html (accessed 6 July 2010). Santamaria Herreria C F (2004), Estudio de la biologia floral del caimito (Crysophyllum cainito L.) en el Zamorano, Honduras. Tesis de Licenciatura, El Zamorano. 25 pp. Yahia EM (1998), ‘Modified and controlled atmospheres for tropical fruits’, Horticultural Reviews, 23, 123–183. Yahia E M (2004), ‘Sapodilla and related fruits’, in United States Department of Agriculture, Agric. Handbook No. 66 Available from http://www.ba.ars.usda.gov/hb66/index.html (accessed 2 July 2010).

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(a)

Plate XLII

(b)

(Chapter 19) (a) Star apple fruit on the tree and (b) exterior and interior of the star apple fruit.

(a)

(b)

(c)

Plate XLIII (Chapter 24) (a) White sapote tree, (b) white sapote fruit, (c) interior and exterior of white sapote fruit.

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20 Sugar apple (Annona squamosa L.) and atemoya (A. cherimola Mill. × A. squamosa L.) C. Wongs-Aree, King Mongkut’s University of Technology Thonburi (KMUTT), Thailand and S. Noichinda, King Mongkut’s University of Technology North Bangkok (KMUTNB), Thailand

Abstract: Sugar apple (Annona squamosa Linn.) and the hybrid, atemoya (A. cherimola Mill. × A. squamosa Linn.) are aggregate fruit with climacteric patterns of respiration and ethylene production during fruit ripening. Their flesh is sweet and pleasant flavoured containing high contents of carbohydrates and vitamin C. Fruit ripen very quickly at ambient temperatures within several days after maturation. Fruit softening, splitting and cracking are the major postharvest problems. When fruit reach the ethylene peak, activities of some cell wall hydrolase enzymes dramatically increase. Recommended storage temperatures are above 13 °C, and lower temperatures cause chilling injury. An atmosphere with 3–5% O2 + 5–10% CO2 has been recommended for sugar apple and atemoya storage. Alternatively, modified atmosphere packaging and 1-MCP treatments are promising techniques to extend storage life and maintain quality of sugar apple. However, improper concentrations of 1-MCP and/or high CO2 can induce physiological disorders. Key words: Annona squamosa Linn., sugar apple, custard apple, sweetsop, atemoya.

20.1

Introduction

20.1.1 Origin, botany, morphology and structure The family Annonaceae belongs to the order Magnoliales of the Angiosperms in the plant kingdom. It includes approximately 50 genera, of which only three, Annona, Rollinia, and Asimina, produce edible fruits (Rasai et al., 1995). Of the Annona species, almost 100 are represented in the American continent including various fleshy fruits, some of which are commercially cultivated (Phillips and Campbell, 1994). In this chapter sugar apple (Annona squamosa Linn.),

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alternatively also called custard apple or sweetsop, and the hybrid atemoya (A. cherimola Mill. × A. squamosa Linn.) are reviewed. The plants share genetic material and requirements for environmental conditions and management as they both originate from Central and Latin America. Sugar apple Sugar apple is a heart-shaped, rounded fruit (Fig. 20.1(b), (d)) with sweet, custardlike, consistent flesh (hence its alternative names custard apple or sweetsop) and a pleasant flavour. The fruit is formed from the fused developing pistils of a perfect flower (Fig. 20.1(a), (c)). As the flowers contain many stamens and carpels, an aggregate of berries with a lot of seeds is produced. The fruit, which has a scaly or lumpy skin, is 5–10 cm in diameter and 70–230 g in weight (Wanichkul, 2009b). In Thailand, sugar apples are divided into two main groups: ‘Fai’ and ‘Nang’ types (Fig. 20.2). ‘Fai’, a local Thai type, contains a lot of seeds. The flesh turns very soft soon after the onset of ripening and the fruit carpels are quickly split out during ripening (Fig. 20.3(a)). Two cultivars of ‘Fai’ type are named ‘Green Fai’ (see Plate XXXV(A) in the colour section between pages 238 and 239) and

Fig. 20.1

Structure of leaf, flower (a), fruit (b) of sugar apple. Floral and fruit structures (c, d) showing multiple ovaries on a single flower.

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Fig. 20.2

401

Sorting diagram of sugar apples cultivated in Thailand.

Fig. 20.3 Morphological characteristics of ‘Fai’ (a), ‘Nang’ (b) sugar apple fruits when ripe.

‘Purple Fai’ (pinkish flesh) (see Plate XXXV(B) in the colour section) based on their peel colours. The ‘Nang’ type, which spread to Thailand from neighbouring Vietnam, has pulp that takes on a custard-like consistency during ripening and the carpels in the fruit remain stuck together (Fig. 20.3(b)). Three cultivars of the ‘Nang’ type are ‘Green Nang’ (see Plate XXXV(C) in the colour section), ‘Purple Nang’ (see Plate XXXV(D) in the colour section), and ‘Golden Nang’ (see Plate XXXV(E) in the colour section). Furthermore, another selected variety is seedless (see Plate XXXV(F) in the colour section) producing small fruit. Various cultivated sugar apples in some other countries across the world are shown in Table 20.1. In Florida, USA, the fruit of ‘Seedless’ sugar apple, apparently identical to ‘Cuban Seedless’ and ‘Brazilian Seedless’ cultivars, splits when it matures on the tree and its quality is slightly lower than normal. The ‘Purple’ cultivar from Cuba has an attractive appearance with purple skin and pinkish flesh, but inferior internal quality (Phillips and Campbell, 1994). Atemoya Atemoya is a hybrid of the sugar apple and the cherimoya. Its genotype and phenotype are a mixture of those of its parents and many atemoya hybrid cultivars

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Postharvest biology and technology of tropical and subtropical fruits Table 20.1 Some cultivated sugar apples in some countries Country

Cultivars

Egypt India Thailand

Beni Mazar, Abd El Razik Red Sugar, Mammoth, Balangar, Kakarlaoahad ‘Fai’ type: Green, Purple ‘Nang’ type: Green, Purple, Golden Thai Lessard, Kampong Mauve, Purple or Red, Cuban Seedless, Brazilian Seedless Nabo, Na Dai

USA Vietnam

Source: Modified from Wanichkul (2009a).

have been produced by conventional breeding programmes. Fruit production of many atemoya cultivars is usually derived from cross-fertilization because the complete stigmas develop at a different time to when the pollen is shed. Abnormal shapes of developing fruit, mainly caused by incomplete pollination, are effectively improved by hand pollination (Campbell and Phillips, 1994). Atemoya fruit has a conical to ovate shape with weight range of 200–800 g, and fruit can vary in its external appearance depending on the different parents (Nakasone and Paull, 1998). Most atemoyas obtain some favourable characteristics from the cherimoya including heart-shaped or symmetrical fruit, large fruit size with few seeds and exquisite aroma volatiles. Some cultivars, however, also acquire less favourable attributes such as fruit splitting or skin blackening. Peel colour varies from medium green to light green or greenish yellow at maturity, depending on the cultivar, while pulp, a custard-like consistency, is white and sweet with pleasing flavour when ripe. The average atemoya has a few seeds per fruit but fruits comprising many seeds are larger and more symmetrical (Campbell and Phillips, 1994). Among atemoya cultivars, ‘African Pride’ and ‘Gefner’ are the most well known. ‘African Pride’ naturally produces few fruit and the fruit often develop various disorders such as internal woodiness and skin blackening during ripening. ‘Gefner’, however, bred in Israel, has satisfactory fruit production and fruit quality without hand pollination. ‘Page’, a cultivar from the USA, also has good fruit production but the fruit usually split on the tree at maturation (Campbell and Phillips, 1994). Other atemoya hybrids in some countries are shown in Table 20.2. ‘African Pride’ fruit produced in Thailand have bigger fruit and fewer seeds than the local sugar apples, but the fruit can split on- and off-tree. A promising cultivar discovered from local breeding programmes, named ‘Pet Pakchong’ (or ‘Petch Pakchong’) (see Plate XXXV(H) in the colour section) produces big fruit of consistent shape with bright yellow peel. Fruit are heart-shaped with an average weight of 440 g. They have smooth areole, thin peel and few seeds. The fruit does not split when ripening, the carpels fuse together in a similar way to those in the ‘Nang’ sugar apple, which is one of the parents, and the fruit sweetness is up to 20 °Brix (Wanichkul, 2009a).

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Sugar apple (Annona squamosa L.) and atemoya Table 20.2

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Some cultivated atemoyas in some countries

Country

Cultivars

Australia

African Pride, Pink’s Mammoth, Hillary White, Nielsen, Island Gem, Maroochy Gold Cherimata, Finny Gefner, Kabri, Malalai Pet Pakchong, Golden Flesh Bradley, Keller, Page, Priestly, Stremer, Caves

Egypt Israel Thailand USA

Source: Modified from Wanichkul (2009a).

Table 20.3 Jan

Feb 1.

Cycles of sugar apple production in Thailand Mar

Apr

May Jun

Pruning Flowering and management 2.

Jul

Aug

Sep

Oct

Nov

Dec

Normal production Harvesting time

Normal and off season production

Pruning Flowering and management Harvesting Pruning Flowering and management time

Harvesting time

3. Alternative production for no irrigation area Pruning

Flowering and management

Harvesting time

20.1.2 Worldwide importance and economic value Tropical regions such as Brazil, Mexico, India, Philippines, Taiwan and Thailand are the important production areas for sugar apples while Australia and the USA are the main atemoya production areas. Thailand can generally produce and supply sugar apple and atemoya fruits for about 6–7 months between June and December, but normal seasonal production is between June and August (Table 20.3). Most production comes from the north-eastern area of Thailand and some from the western region. Sugar apple fruit are seasonally harvested between September and October in Taiwan, while in Florida, fruit matures from late June to October, but a small second crop matures in December and January. However, since the flowering behaviour is practically forced by pruning techniques and irrigation control, sugar apple and atemoya can be programmed to be produced all year round. Sugar apple and atemoya, being minor tropical fruits, are exported in small volumes in the world market. In general, most fruit in the producing countries are supplied to domestic markets. Consequently, this may cause lack of interest in postharvest research in some countries. Most countries which import both sugar apples and atemoyas are in Asia. These include Hong Kong, Singapore, Brunei, China and Japan. Some European countries such as France, Germany and the Netherlands are also importers (Sanewski et al., 1989; Wanichkul, 2009b). In Brazil, the area of sugar apple production had dramatically increased by the end of the 20th century. This growth was due to the increasing demand for sugar

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apple in the north-eastern Brazilian market. The development of agroindustry of fresh fruits has encouraged expansion of cultivated areas in the Americas (Anon, 2002b). In the world market, demand for sugar apples and atemoya have, however, failed to increase. Different reasons for this have been proposed. For example, although the sugar apple was introduced to the Australian market approximately 70 years ago, its rapid expansion has just occurred over the last 20 years and approximately 40% of Australians have never tried a sugar apple (Swinbourne, 2007). In Asia, sugar apple is one of Taiwan’s ‘Top 10’ fruits but, in Thailand and Southeast Asian countries, the volumes of export have not been increased due principally to its short postharvest life. Some physiological disorders such as fruit cracking, splitting, and blackening as well as difficulty of eating fruit containing a lot of seeds are additional factors for export failure. Furthermore, consumers of sugar apple are limited in some groups because of inconsistent fruit quality, quick ripening (within a few days after harvest), and lack of proper advertisement or promotion in many countries. According to a commercial survey, consumers are largely unaware of varietal differences but the more common and less expensive varieties are more in demand. In term of fruit quality, consumers desire fruit with minimum seeds, more consistent flavour and better external shape and appearance, and without disorders such as woodiness or skin blackening (Nissen et al., 2002). Information also needs to be developed for display in retail markets informing consumers how to consume, store, and use sugar apples and atemoyas in some food dishes, and informing them of their nutritional values (Swinbourne, 2007). 20.1.3 Culinary uses, nutritional value and health benefits Sugar apple flesh is delicious, smooth and creamy and contains high levels of sugars, antioxidants and vitamin C, and some minerals such as magnesium and potassium. Due to the high carbohydrate and sugar levels, people who are controlling their weight must consider carefully the amount of sugar apple dishes they consume. The amount of amylose present in starch isolated from sugar apple and soursop (A. muricata) fruits is very similar. The sugar apple starch has higher swelling power and solubility compared to soursop starch (Nwokocha and Williams, 2009). In general, sugar apple flesh contains glucose : fructose : sucrose as 5.8 : 4.5 : 0.8 g 100 g−1 FW (Preungvate, 1982), high quantities of ascorbic acid (70.8 mg 100 g−1 FW) (Iqbal et al., 2006) and little vitamin E (0.1 mg 100 g−1 edible portion) (Charoensiri et al., 2009). ‘Brown’ sugar apple fruit contains an ascorbic acid content of 21.3 mg 100 g−1 FW while ‘Green’ fruit contains 6.8 mg 100 g−1 FW (Yan et al., 2006). Sugar apple flesh contains some phenolic compounds including catechin, chlorogenic acid, eugenol and gallic acid (Wu et al., 1997). During ripening, phenolic compounds are slightly higher in ‘Nang’ sugar apple (0.63–0.65 mg gallic acid ml−1) than in ‘Fai’ fruit (0.58–0.65 mg gallic acid ml−1) (Noichinda et al., 2010b). The content of anthocyanins increases during ripening, anthocyanins being one of the pigments responsible for the pulp colour of ‘Purple’ sugar apple, an outstanding variety grown in Mexico (Bolívar-Fernández et al., 2009). ‘Purple’ sugar apples contain phenolic compounds at levels 3–4 times

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higher than in ‘Pet Pakchong’ atemoya (green peel). The antioxidant capacities tested by the 1,1-diphenyl-2-picryl hydrazyl (DPPH) method in flesh of ‘Purple Fai’, ‘Purple Nang’ and ‘Pet pakchong’ atemoya were 86.73, 66.37, and 16.81%, respectively (Noichinda et al., 2009b). Furthermore, antioxidant capacity tested by the Ferric reducing antioxidant power (FRAP) method in ‘Brown’ sugar apple fruit is 0.62 mg GAE g−1 while it is 0.58 mg GAE g−1 for ‘Green’ cultivar (Yan et al., 2006). A large number of chemical compounds, including flavonoids, alkaloids and acetogenins were found in Annona seeds and many other parts of the plants. There have been reports studying the potential use of extracts for controlling insects, pests, and human diseases (Chungsamarnyart et al., 1992; Morita et al., 2000; Chuakul and Sornthornchareonon, 2003; Rao et al., 2005; Yang et al., 2008). Flavonoids and alkaloids from the plant extracts have shown insecticidal and antibacterial properties, and have been used for treatments of medical conditions, such as skin disease, inflammation of the eye, and intestinal worms. Acetogenins are thought to have anti-HIV and anti-cancer effects. A wide variety of potential products have been developed and are available for cancer treatments (Anon., 2002b) or as anti-inflammatories (Yang et al., 2008).

20.2

Fruit development and postharvest physiology

20.2.1 Fruit growth, development, and maturation The growth and development of ‘Pet Pakchong’ atemoya fruit grown in northeastern Thailand is described as an example. Floral development of ‘Pet Pakchong’ requires 33 days from floral initiation to anthesis or 48 days after branch pruning whereas the period from beginning of anthesis to full bloom is one day only. The stigma are receptive at the beginning of anthesis and unreceptive one hour after anthesis while the pollen shed take places between 2.00 and 4.00 pm on the first day of anthesis (Thongteera et al., 2007a). Fruit grows and develops for 4–5 months until entering the maturation phase. Fruit development follows a double sigmoidal curve. During the first three weeks after fruit set, fruit size increases slowly but increases rapidly afterward. Growth proceeds slowly between week 9 and 11, and thereafter fruit size increases rapidly until week 18 (Fig. 20.4). Seeds become mature with the colour changing to brown at week 14 whereas the pulp changes from light green to white colour at week 15. Soluble solids (SS) and titratable acidity (TA) contents, and ratio of SS:TA of the pulp continuously increase as the fruit develops (Thongteera et al., 2006a). 20.2.2

Respiration, ethylene production, and ripening

Respiration and ethylene production Both sugar apple and atemoya fruits exhibit climacteric patterns in which maximal CO2 production occurs after harvest. Respiration of ‘Fai’, ‘Nang’ sugar apple and

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Fig. 20.4

Means of fruit weight ({) and specific gravity (×) of ‘Pet Pakchong’ atemoya after fruit setting (redrawn from Thongteera et al., 2006a).

‘African Pride’ atemoya collected at commercial maturity for the domestic market reach climacteric peaks on days 3 and 4 respectively after harvest at 25 °C. Ethylene production peaks of ‘Fai’ and ‘Nang’ fruits are simultaneous with respiratory climacteric peaks, but the ‘African Pride’ peak is two days after the climacteric peak. All fruits release aroma volatiles while reaching the climactic peaks. ‘African Pride’ generally shows fruit cracking around the peduncle a day after the climacteric peak (Fig. 20.5). During ripening, ‘Nang’ and ‘African Pride’ rind can be peeled out easily. All three ripe fruit contain soluble solids (SS) contents in the range 25 to 26.5% and SS/TA (soluble solids/titratable acidity) ratios of 223.4, 114.9 and 100.3 in ‘Fai’, ‘Nang’ and ‘African Pride’ fruits, respectively (Kasiolarn, 1991). The fruit starts softening quickly when the ethylene production rate is at its maximum, but ethylene evolution rates are quite low at <1.5 μL kg−1 h−1 at ambient temperature (Tsay and Wu, 1990; Kasiolarn, 1991). While sugar apples have high respiration velocities at the climacteric maximum >200 mg CO2 kg−1 h−1, ethylene production is lower than 1.0 μL kg−1 h−1 (Kasiolarn, 1991; BolívarFernández et al., 2009). Interestingly, in contrast to sugar apples, atemoya fruit produces ethylene in abundance – up to 100 to 300 μL kg−1 h−1 at room temperature (Brown et al., 1988; Kasiolarn, 1991). Fruit softening There are few differences in taste and flavour between ripe and over-ripe sugar apple fruit. Although fruit firmness is not a critical concern for eating quality, it is important for adequate fruit transportation and distribution. Furthermore, some varieties split or crack easily during ripening. Flesh firmness of ‘Fai’ sugar apple

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Fig. 20.5 Respiration (solid lines) and ethylene production (dashed lines) rates of ‘Nang’ ({), ‘Fai’ (Δ) sugar apple, and ‘African Pride’ (×) atemoya fruits at the commercial maturities stored at 25 °C (redrawn from Kasiolarn, 1991). Dashed vertical arrow indicates the adjusted point of y-axis for ethylene production rate. S indicates fruit softening while A and C indicate aroma released and fruit cracking, respectively.

rapidly decreases from 6.4 to 0.5 Newtons two days after harvest at ambient temperature. As the fruit ripens, the peel becomes easy to remove from the carpel and the carpels separate from each other. However, even though the pulp of ‘Green Nang’ becomes soft and creamy when fruit firmness declines from 8.9 to 0.5 Newtons in the two days following harvest, the fruit carpels stay bound to each other (Noichinda et al., 2010a). Some enzymes associated with cell wall degradation have been investigated to comprehend the biological processes of softening in sugar apples. Sugar apple fruit grown in Yucatán, México, harvested at physiological maturity and stored at 26 ± 2 °C and 60–70% relative humidity for four days showed accelerated softening and a decrease in pH. Increasing pectin methyleaterase (PME) and polygalacturonase (PG) activities are directly related to a decrease in the firmness and deformation of the fruit (Bolívar-Fernández et al., 2009). Furthermore, Wu and Tsay (1998) reported that activities of PME, PG and β-galactosidase in

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‘Tsulin’ sugar apple harvested at the full mature stage increased quickly and reached a maximum in 3–4 days when stored at 26 °C, but this increase was delayed by several days at 21 °C. In the case of Thai sugar apples, PME activity of ‘Fai’ (fruitlet splitting variety) moderately increases from the first day after harvest but that of ‘Nang’ (fruitlet gelling variety) remains stable all the time at room temperature (25 °C). In ‘Fai’, activity of Exo-PG slightly increases and reaches a peak on day 3, which is followed by a sharp increase in Endo-PG activity. Interestingly, pectatelyase (PL) plays an significant role in the softening process of ‘Fai’. Its activity rapidly increases at a high rate and reaches its maximum on day 2 after harvest (Noichinda et al., 2010a). Further evidence of cell wall softening enzymes needs to be obtained for greater understanding and clarification of the ripening phenomenon in different cultivars of sugar apples and atemoyas. Aroma volatiles Sugar apple flesh comprises terpenes such as α-pinene, β-pinene, linalool, germacrene-D and spathulenol; esters such as butylbutanoate and methyllinolenate; along with benzyl alcohol and two oxygenated sesquiterpenes as the major volatiles when extracted with dichloromethane and n-pentane (1:1) (Shashirekha et al., 2008). Most atemoyas produce a better odour than sugar apples, a trait inherited from the cherimoya. The major components identified in the head space (HS) of flesh homogenate of Annona atemoya grown in South Queensland (Australia) using tenax trapping followed by thermal desorption and by simultaneous distillation extraction (SDE)/GC-MS are esters including methyl and ethyl butanoate and methyl hexanoate (Bartley, 1987) while the major ester components in ‘Pet Pakchong’ atemoya analyzed using HS/Solid Phase Micro Extraction (SPME)/GC-MS technique are methyl ester derivatives (Fig. 20.6). Pino and Rosado (1999) reported that 53 compounds were identified by simultaneous steam distillation-solvent extraction (SDSE) and analysed by GC/ MS. The major compounds in the volatiles were α-pinene, β-pinene, limonene, bornyl acetate and germacrene D. This is consistent with the report on ‘African Pride’ that the volatiles separated by SDSE are mono or sesquiterpenes with α and β pinene, germacrene D, and bicyclogermacrene being the major components. There is no marked change in the composition of the volatiles during ripening (Wyllie et al., 1987).

20.3

Maturity

Sugar apple and atemoya fruit production can be managed at any time of the year due to behaviours of the plant growth and development. Flower buds will develop on any pruned branch that is under drought stress for 5–6 weeks. Fruit can be harvested within four months after flowering. Sugar apple and atemoya fruit harvested at the immature stage will not ripen satisfactorily. The fruit is mature when it has grown to maximum size and changed colour from medium green to

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Fig. 20.6 Volatile chromatogram of ripe ‘Pet Pakchong’ atemoya flesh monitored using head space-SPME/GC-MS.

lighter green or yellowish green. Thai famers usually use their experience to judge when to harvest sugar apple. They have learned to harvest the fruit when they notice the areoles swelling and the fruit grooves expanding. When maturity is reached, sugar apple carpellary segments and the groove-like areas between carpellary segments turn pale green to yellow. The physiological maturity stage, at which point the fruit is harvested, is between 110–120 days after anthesis (DAA). Sugar apple fruit reach their best edible quality at the beginning of the post-climacteric phase. From this point they have a postharvest shelf life at 26 ± 2 °C and 60–70% relative humidity of no longer than four days (BolívarFernández et al., 2009). Levels of both ascorbic acid and glucose in sugar apple increase to a maximum at the climacteric, but decrease as the fruit become over ripe (Broughton and Guat, 1979). ‘Pet Pakchong’ atemoya are harvested at about 111–129 DAA (16–18 weeks). The fruit is ready to harvest when the peel colour turns to yellowish-green (YG 144D-YG 150D) and the groove colour around the fruit carpel (areole) turns from white to cream. The fruit density at maturation should be less than 0.94 (Fig. 20.4). For heat unit determination, the mature-green stage of ‘Pet Pakchong’ contains about 1623.3–1967.4 degree days (Thongteera et al., 2007b). Mature atemoya fruit can ripen to good eating quality after removal from the tree, but some atemoya fruit split and their skins darken during ripening. These postharvest problems can be reduced by harvesting the fruit soon after maturation. Many atemoya fruit split as they mature on the tree, especially during the rainy season.

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This reinforces the fact that the fruit should be collected a few days before reaching full maturity (Campbell and Phillips, 1994).

20.4

Preharvest factors affecting fruit quality

20.4.1 Fruit setting and timing of harvest The productivity of some sugar apples is reduced with natural pollination due to failure of fruit setting. Although spraying blooming flowers with 250 ppm 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5TP) spectacularly improves initial fruit setting, 100% of the fruit drop at a premature stage. Artificial hand pollination of sugar apple and atemoya dramatically increases normal fruit shape, fruit setting and development (Anon., 2002a). Thus artificial hand pollination should form part of a ‘good agricultural practice’ programme to improve the yield of existing cultivars. Harvest timing is important for post-harvest quality. Harvesting ‘African Pride’ fruit one and two weeks before commercial maturity effectively reduced fruit cracking, while fruit harvested three weeks prior to maturity did not show fruit cracking. However, the younger fruit lost more weight during ripening and contained lower levels of soluble solids, SS/TA and vitamin C (Kasiolarn, 1991). ‘Pet Pakchong’ atemoya harvested at 90 and 95 DAA ripen normally and have the longest shelf life, while fruit harvested at 110 DAA have the shortest storage life, but the ripe fruit have a very good taste. All fruit harvested at different maturities produce the ethylene peak before the respiration climacteric peak (Oumsomniang, 2005). ‘Pet Pakchong’ fruit harvested at 111–120 DAA ripen and acquire good quality when incubated at ambient conditions for six days, while fruit harvested at 123–129 DAA need only four days. During ripening, the peel colour changes rapidly from light green to black and becomes unaccepted within two days (Thongteera et al., 2006b). 20.4.2 Gibberellic acid application Fruit cracking or splitting on and off the tree is one of the main problems postharvest for sugar apples and atemoya. Kosiyachinda and Kasiolarn (1989) reported that gibberellic acid (GA3) treatment preharvest reduced postharvest cracking of ‘African Pride’ atemoya. Fruit sprayed with GA3 at 50 and 100 ppm twice at 7 and 14 days before harvest exhibited less fruit cracking when stored at 25 °C. Furthermore, GA3-sprayed fruit treated with calcium carbide (CaC2) to hasten ripening exhibited no cracking during ripening. 20.4.3 Fruit bagging The practice of bagging atemoya and sugar apple fruit while they are still on the tree was studied in Brazil. The use of a milky-coloured plastic bag reduced infestation with the fruit borer Cerconota anonella in atemoya fruits. However, non-bagged sugar apple fruit (control) showed better shelf life and higher firmness. Weight, length, fruit diameters, and the content of total soluble solids in the pulp were not affected by bagging (Pereira et al., 2009). The effects of fruit bagging

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on the quality of ‘Pet Pakchong’ atemoya was also reported in Thailand. The dimensions (both length and width) of bagged fruit were larger. Peel brightness increased at seven days after bagging. Non-bagged fruit reached maturity on day 116 after fruit setting while bagged fruit did only after 112 days (Monkong et al., 2010). The effect of colour of bag materials on fruit quality was also investigated. Bagged fruit were brighter than non-bagged fruit. Fruits bagged in yellow bags had the highest brightness (Monkong et al., 2009).

20.5

Postharvest handling factors affecting quality

20.5.1 Temperature management Sugar apple fruit become soft and ready-to-eat within several days at ambient temperature (24–32 °C) (Chunprasert et al., 2006; Bolívar-Fernández et al., 2009) Low temperature storage is essential to extend the shelf life postharvest. The lower the temperature, the longer the storage life is extended. However, since they are tropical fruits, temperatures used for storage of sugar apples and atemoyas should be above 13 °C, principally to avoid chilling injury. Chilling injury is discussed in more detail in section 20.6.1. Sugar apple loses more of its fresh weight when stored at higher storage temperatures of ≥16 °C with 85–90% relative humidity (RH). Fruit starch content gradually decreases while, in contrast, glucose, fructose, and sucrose increase rapidly at higher temperatures (Wu et al., 1999). Abscisic acid content of fruit decrease in fruit stored at high temperatures (Tsay and Wu, 1990). 20.5.2 Physical damage Due to their thin peel and protruding areoles, sugar apple and atemoya fruit are very susceptible to mechanical damage. Furthermore, during maturation, carpel segments will become swollen and in some varieties, the fruitlets split and crack. Gentle handling is required throughout the postharvest chain. Sugar apple and atemoya fruits typically lose less than 10% of their weight during postharvest periods at room temperature (25 °C), and cracked fruit loses more weight than intact fruit. Intact ‘African Pride’ loses 8.53% while ‘Fai’ and ‘Nang’ fruits lose 6.09% and 6.49% of their weight when stored at 25 °C for a week (Kasiolarn, 1991). Moreover, smaller fruit lose more weight than larger ones during storage (Kasiolarn, 1991). 20.5.3 Atmospheric conditions Storage atmosphere conditions can affect quality and physiological changes in the stored fruit. The gaseous proportions recommended for storage of sugar apple and atemoya are 3–5% O2 and 5–10% CO2 (Broughton and Guat, 1979; Kader, 2001; Cantwell, 2002). However, too high a level of CO2 inside the package induces peel blackening of sugar apple (Chunprasert et al., 2006). On the one hand, ripening of sugar apple can be enhanced by removal of CO2 and addition of O2 to the storage atmosphere. On the other, it can be delayed by the addition of CO2 or removal of

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O2. Fruit under low relative humidity ripen faster than those stored under highhumidity conditions (Broughton and Guat, 1979). See further on page 417.

20.6

Physiological disorders

20.6.1 Chilling injury (CI) As tropical fruits, sugar apples and atemoyas are very sensitive to low temperature storage, symptoms of chilling injury include skin darkening and loss of aroma and flavour. At 10 °C, stored sugar apple fruit will become hard and less sweet, show surface blackening and have a messy pulp (Vishnu Prasanna et al., 2000). Broughton and Guat (1979) suggested that storage temperatures below 15 °C cause chilling injury in sugar apple. However, in some studies fruit have been stored at 13 °C without showing CI symptoms (Kasiolarn, 1991; Campbell and Phillips, 1994; Chunprasert et al., 2006). Figure 20.7 shows that the respiration rate of ‘African pride’ atemoya fruit was about 40–150 mg CO2 kg−1 h−1 at 15 °C while it was only 20–52 mg CO2 kg−1 h−1 at 5 °C. At this lower temperature the fruit failed to exhibit a climacteric pattern during storage (i.e. the fruit did not ripen). Some areas of the peel surface turned from green to brown (a symptom of CI) after

Fig. 20.7 Respiration (solid lines) and ethylene production (dashed lines) rate of ‘African Pride’ atemoya fruit stored at 5 (Δ), 10 (×), and 15 °C ({). S indicates fruit softening while CI indicates chilling injury (redrawn from Kasiolarn, 1991).

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storage at 5 °C for 10 days. Ethylene production remained at the low rate of about 0.2–0.4 μL kg−1 h−1 and slightly increased after CI had developed for two days. 20.6.2 Other physiological disorders Skin blackening after harvest is a major disorder in Annona fruit, such as ‘green’ sugar apple and ‘African Pride’ atemoya (Fig. 20.8(a)). Annona fruit peel turns brown quickly at room temperature even when the fruit has not been bruised. Bolívar-Fernández et al. (2009) found that the activity of polyphenol oxidase (PPO), the main enzyme causing blackening, was higher at the beginning of the sugar apple’s post-climacteric phase. Furthermore, high CO2 levels (>20%) during long storage durations cause peel darkening, for example when fruit is stored in a high CO2 atmosphere inside thick polyethylene (PE) bags (Fig. 20.8(c), (d)). Long storage duration in MAP can also cause the flesh colour to change from white to pink (Chunprasert et al., 2006). As already mentioned, some atemoya cultivars such as ‘African Pride’ and ‘Page’ tend to crack during ripening or fruit maturation on the tree and many sugar apple fruits maturing during the rainy season are lost due to splitting (Fig. 20.8(b)). Sugar apple fruits respire at high levels and therefore storage in modified atmosphere can be beneficial to reduce physiological disorders and control ripening.

Fig. 20.8 Postharvest fruit blackening (a) and on tree fruit cracking (b) of ‘African Pride’ atemoya. ‘Green Nang’ sugar apple fruit kept in 6 μM PE bag for 15 days at 13 °C (c); ‘Green Nang’ sugar apple fruit kept in 15 μM PE bag for 15 days at 13 °C (d).

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20.7

Postharvest biology and technology of tropical and subtropical fruits

Diseases, insect pests and their control

Most postharvest diseases are usually latent infections. Anthracnose caused by Colletotrichum gloeosporioides is the major concern among all the Anonna diseases affecting atemoya and sugar apple production. C. gloeosporioides can infect flowers, leaves, and fruit of the sugar apple, causing various manifestations disorders such as blossom blight, fruit russeting, fruit rot and mummified fruit (McMillan, 1986). Infected young fruit will rot and mummify on the tree (Fig. 20.9(a)). When the fungus invades mature fruit, the resultant lesion is small with a shallow area of hardened tissues (Mossler and Crane, 2002). In Southeast Asia, Botryodiplodia theobromae Pat. causes disease in sugar apple which can also manifest as mummified fruit or the postharvest disease stem end rot. Sugar apple fruits are susceptible to fungal attack at temperatures above 25 °C (Broughton and Guat, 1979). Postharvest pathologies of atemoyas including anthracnose, Phomopsis rot and Rhizopus have been recorded (Sanewski, 1988). Copper is primarily used in an attempt to manage anthracnose. Copper has long been used as a fungicide and can be applied in multiple forms (copper hydroxide, copper sulfate, etc.). Fungicides registered in Florida for use on atemoya and sugar apple include azoxystrobin, copper hydroxide/sulfate, mefenoxam, hydrogen dioxide, Bacillus subtilis, phosphoric acid, sulfur, and Trichoderma harzianum (Mossler and Crane, 2002). As an alternative, the Australian sugar apple industry has considered the use of rootstock techniques for

Fig. 20.9

Fruit appearance of beginning of mummified fruit (a); mealy bug infestation (b), (c); mature fruit after removal of mealy bug (d).

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plant adaptation to disease and environmental stresses. ‘Nang’ sugar apple, a Thai local variety, meets the criteria for a disease-resistant dwarfing rootstock and is suitable for Australian growing conditions (Sloper, 2007). Developing fruit are usually attacked by mealy bug (Pseudococcus sp.) at the groove area (Fig. 20.9(b), (c)) causing lesion scrap between the grooves after harvest (Fig. 20.9(d)). Annona seed borer (Bephratelloides cubensis), an important pest, affects fruit at all stages of fruit development. It develops in the seeds of young fruit and emerges as an adult in the mature fruit, boring and ruining the fruit at this stage. Fungi often attack the infested fruit causing further infections which lead to mummification of the fruit (Phillips and Campbell, 1994). Atemoya is less susceptible to rust than cherimoya but is susceptible to attack by the same insects and many of the fruit that mature during the rainy season split before attaining full maturity. Sugar apples and other Annona spp. may require a combination of preharvest and post-harvest treatments to prevent infestation with insects. Primary Industries and Resources in South Australia recommends that sugar apple, as a fruit fly host material, should be fumigated with methyl bromide at 15 °C–20.9 °C at a rate of 40 g m−3 for 2 hrs; or 21 °C–25.9 °C at 32 g m−3 for 2 hrs; or 26 °C–31.9 °C at 24 g m−3 for 2 hrs. Packaging of fumigated fruit must allow for penetration and subsequent aeration of the methyl bromide (Anon, 2006). However, due to the forthcoming legal prohibition of the use of methyl bromide in many importing countries in the near future, other safe chemicals, heat treatments or gamma irradiation need to be investigated as replacements.

20.8

Postharvest handling practices

20.8.1 Harvest operations and packinghouse practices Major production of sugar apples and atemoyas in Thailand is located in the Northeastern region. Plant flowering can be controlled by branch pruning (Fig. 20.10(a)). Developing sugar apples are covered with paper bags (Fig. 20.10(b)) to protect them from some insects. Fruit at physiological maturity (16–18 weeks) are harvested by cutting the stem close to the fruit using sharp scissors. Harvested fruit are immediately transferred to a packinghouse (Fig. 20.10(c)). For distant markets, the fruit are harvested 2–3 weeks prior to ripening. After removal of bags, forced air from an air pump is used to clean up the fruit, removing insects attached at the fruit groove. Fruit are then graded according to size and shape, with heart-shape fruit most preferable for ‘Pet Pakchong’ atemoya (Fig. 20.10(d)). After wrapping with a foam net (Fig. 20.10(e)) to prevent the fruit from mechanical damage, fruit are packed in bulk containers for distribution. Local containers both for retail (Fig. 20.10(f)) and bulk containers (Fig. 20.10(g)) are usually made from bamboo sheet. For export, fruit are packed in a single layer 4–5 kg or 9 kg fibreboard boxes with foam sleeves or paper wrapping. Domestic distribution is usually operated by a small open-air truck (Fig. 20.10(h)) while fruit for export is transported by a refrigeration truck.

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Fig. 20.10 Sugar apple supplements in Thailand: branch pruning technique for sugar apple flowering (a); bagging of ‘Pet Pakchong’ fruit (b), assembling at a packinghouse (c), grading of fruit shapes (d), packing with un-bumping foam net (e); packing in traditional bamboo baskets (f ); packing in bulk bamboo baskets (g); local transportation of sugar apple (h).

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Thailand’s domestic standards divide sugar apple into four groups: 1 2 3 4

Extra large size (average weight of 350 g); Large size (average: 300 g); Medium size (average: 250 g); Small size (average: 160 g) (Nonta, 2009).

For European markets, sugar apples and atemoyas are graded according to their size, with the corresponding maximum permissible variation within the package (vp) in grams according to the standard FFV-47 released by the United Nations/ Economic and Social Council (UN/ECE, 2002). The minimum weight for sugar apples and atemoyas is 100 g and weight ranges are as follows: from 100–225 g (vp: 75 g), 225–425 g (vp: 100 g), 425–825 g (vp: 200 g), and >825 g (vp: 300 g).

20.8.2

Control of ripening and senescence

Modified atmosphere (MA) Modified atmosphere storage has been used to extend the storage life of many perishable crops including sugar apple and atemoya. However, storing fruit in an improper atmosphere may result in some disorders. Some studies on MA storage of sugar apple and cherimoya are described below. Coating ‘Nang’ sugar apple with 0.5 and 1.0% chitosan or individually wrapping the fruit with linear low density polyethylene (LLDPE) did not delay fruit softening when the fruit was stored at 13 °C and 95% RH. Modified atmosphere packaging (MAP) with 6 μM and 15 μM PE bags, though, reduced weight loss and maintained skin and pulp colour. Fruit kept in 6 μM PE bags had a storage life of at least 18 days whereas after day 12, fruit kept in 15 μM PE bags showed skin darkening (Fig. 20.8(c, d)) after removal from the bags due to the high CO2 inside (Chunprasert et al., 2006). Fully mature and freshly harvested sugar apple (Annona squamosa L.) stored in fibreboard boxes had a shelf life of four days at ambient (27 ± 2 °C) and eight days in cool storage conditions (15 ± 2 °C). The post-harvest combination of coating with 6% waxol + 0.1% carbendazim and forced-air precooling (at 10 °C) extended shelf life up to 14 days under cool storage (Kamble and Chavan, 2005). There were reports of the synergistic effects of ethylene absorbents and MAP when used in combination to extend storage life. Sugar apple placed in PE bags containing KMnO4 had a storage life of nine days while untreated fruit could be stored for five days (Babu et al., 1990). Sugar apple packed in 0.1 mm thick polyvinylchloride (PVC) film plus KMnO4 absorbent and stored at 16 °C with 90–100% RH delayed fruit ripening (Chaves et al., 2007). MAP by individual packing in PVC film and placing the fruit in polyester trays wrapped in PVC film did not influence the skin colour of ‘Gefner’ atemoya, but it preserved pulp brightness and reduced weight loss compared to non-packed fruit. Silva et al. (2009) found that MAP and storage at low temperature effectively preserved atemoya and maintained the fruit’s appearance after 15 days of storage. Atemoya cv. ‘PR3’ fruit individually sealed in copolymer (PD-955) and

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low-density polyethylene (LDPE) bags were stored for 21 days at 15 °C or 25 °C and then were unwrapped and maintained at 25 °C for ripening. Weight loss in the packaged atemoyas was lower than in the control (non-wrapped fruit). Fruit sealed in LDPE did not ripen, probably due to development of an injurious atmosphere inside the package. Atemoyas packaged in PD-955 film stored at 15 °C had a shelf life of 17 days compared to the 13 days of the control fruit (Yamashita et al., 2002). Negative physical and chemical changes and deterioration in eating quality was delayed in ‘Pet Pakchong’ fruit wrapped with PVC film and stored at 14 °C. However, the PVC film wrapping caused abnormal ripening. Unwrapped fruit stored at 14 °C had the longest shelf life (12 days) while fruit stored at room temperature had the shortest shelf life (three days) (Oumsomniang, 2005). 1-Methylcyclopropene (1-MCP) 1-MCP is used for extension of postharvest life in many types of fresh produce, in particular climacteric or ethylene-sensitive produce. It inhibits ethylene responses by competitively binding to ethylene receptor in plant cells. 1-MCP is not only practical as vapour fumigation, but it can also be used in small volumes, making the treatment safe from the point of view of human health. It is mostly used as a pretreatment before long periods of storage. Sugar apples treated with 810 ppb 1-MCP for 12 hours at 25 °C and then stored at 25 °C for four days were firmer than the control. Both sugar apples treated with 1-MCP at 30 or 90 ppb and the control fruit ripened faster than fruit treated with 1-MCP at higher concentrations (Benassi et al., 2003). ‘African Pride’ atemoya fruit were fumigated with 25 ppb 1-MCP for 14 hours at 20 °C, treated with 100 ppb ethylene for 24 hours, then ripened at 20 °C. Fruit treated with ethylene alone generally ripened 50% faster than untreated fruit, while 1-MCP treatment alone increased the number of days to ripening by 3.4 (58%). Applying 1-MCP to the fruit prior to ethylene prevented accelerated ripening, so that the ripening time was similar to fruit treated with 1-MCP alone. However, 1-MCP treatment was associated with slightly higher severity of external blemishes in atemoya and slightly higher rotting severity in atemoya, compared to non-treated control (Hofman et al., 2001). Thus, additional precautions may be necessary to reduce disease severity associated with 1-MCP treatment. ‘Fai’, ‘Nang’ sugar apples and ‘Pet Pakchong’ atemoya were fumigated with 500 ppb 1-MCP to study fruit ripening behaviour (Noichinda et al., 2009a). Climacteric peaks at 25 °C were dramatically reduced in 1-MCP treated ‘Nang’ and ‘Pet Pakchong’ (Fig. 20.11(a)) while ethylene production peaks were slightly decreased and delayed following all 1-MCP treatments (Fig. 20.11(b)). The ripening and softening of 1-MCP treated fruit was postponed for 2–3 days (Fig. 20.12). Calcium carbide (CaC2) After harvest most sugar apples and atemoyas in Thailand are traditionally allowed to ripen naturally during transport to the consumer, usually for several days at ambient temperature. The traditional way to hasten fruit ripening is the application of CaC2 which releases acetylene (C2H2) gas to induce fruit ripening.

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Fig. 20.11 Respiration (a) and ethylene production (b) rates of non-treated (solid lines) and 500 ppb 1-MCP-treated fruit (dashed lines) of ‘Nang’ ({), ‘Fai’ (Δ), and ‘Pet Pakchong’ (×) at 25 °C.

Using CaC2 to hasten ripening effectively reduced fruit cracking and fruit weight loss during ripening in ‘African Pride’, but did not affect soluble solids, SS/TA, and vitamin C contents (Kosiyachinda and Kasiolarn, 1989; Kasiolarn, 1991). Flavonoid levels of CaC2-treated sugar apple fruits in ‘Fai’ and ‘Nang’ varieties were slightly lower than those of naturally ripened ones. As far as antioxidant activity abilities were concerned, ferrous ion chelating in both ripened groups was quite low (0.01–0.02%), whereas DPPH free radical scavenging ability, in contrast, was high at 83–92% (Noichinda et al., 2010b). Chemicals Some chemicals, such as plant growth regulators, have been applied to improve postharvest quality of sugar apples. Salicylic acid (SA) is an endogenous hormone that mediates in plant defence against pathogens. It has been reported to reduce decay and extend storage life of various fruits. Treating sugar apple with SA increased activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), decreased lipoxygenase (LOX) activity and correspondingly lowered malondialdehyde (MDA) contents in treated fruit, compared to the control. SS, total soluble sugars, softness and decay rate were significantly lowered in treated fruit, and fruit ripening was achieved after ten days of storage (Mo et al., 2008). SA has positive effects in maintaining membrane integrity and in delaying fruit ripening process.

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Fig. 20.12 Fruit firmness of non-treated (solid lines) and 500 ppb 1-MCP-treated fruit (dashed lines) of ‘Nang’ ({), ‘Fai’ (Δ), and ‘Pet Pakchong’ (×) at 25 °C.

Furthermore, several regulating substances were used to investigate their role in the respiratory climacteric and ripening of sugar apple fruit. Dipping sugar apple fruit in a solution of indole acetic acid (IAA) at concentrations between 10−4 and 10−2 M accelerated ripening (Broughton and Guat, 1979). 1-Aminocyclopropene1-carboxylic acid (ACC) and IAA enhanced the softening and electrolyte leakage of treated-fruit. Respiration of IAA-treated fruit was enhanced. In contrast, aminoethoxyvinylglycine (AVG) and 2, 4-dinitrophenol (DNP) delayed softening. Cycloheximide (CHI), which inhibits de novo synthesis of the cell proteins, caused the fruit to remain harder than the untreated fruit (Tsay and Hong, 1988). 20.8.3 Recommended storage and shipping conditions Mature sugar apple and atemoya fruits can be stored at temperatures above 13 °C to facilitate shipment to distant markets. Lower temperatures cause chilling injury

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with subsequent shrivelling and abnormal ripening (Kasiolarn, 1991; Campbell and Phillips, 1994). Pre-cooling of sugar apples by room- or forced-air cooling at 10 to 13 °C and maintaining controlled atmosphere (CA) conditions at 3–5% O2 + 5–10% CO2 can result in a storage life of four weeks (Kader, 2001; Cantwell, 2002). On the other hand, others have recommended storing sugar apple at temperatures between 15 and 20 °C (Broughton and Guat, 1979; Vishnu Prasanna et al., 2000) and with low O2 and ethylene tensions coupled with 10% CO2 and a relative humidity of 85%–90% in the storage atmosphere (Broughton and Guat, 1979).

20.9

Processing

20.9.1 Fresh-cut processing As atemoya are bigger than sugar apples and contain fewer seeds, they can be used to make fresh-cut products, before they become too soft. However, quick flesh browning is a major concern. Fresh atemoya pulp treated with 0.4–0.5% ascorbic acid and stored in MAP consisting of a 65 μM LLDPE/nylon/ LLDPE five-layer co-extruded bag at 0 °C for four weeks retained the desired creamy colour during storage and after exposure to ambient conditions for three hours. Sensory and microbiological properties of the ascorbic acid-treated atemoya pulp were acceptable throughout the storage period of four weeks (Gamage et al., 1997). 20.9.2 Other processing practices In Thailand, sugar apples are rarely processed. They are mostly consumed fresh as a dessert and are considered to be of poor quality and of little commercial importance. However, the pulp is sweet and has an excellent flavour that can be processed into many products including ice cream, sweet desserts, nectar, jelly, jam, conserves, sherbet, syrup, tarts, juice and fermented drinks (wine/liquors) (Ojha et al., 2005; Wanichkul, 2009b). Heat is commonly used to preserve processed products, but care should be taken with respect to its effect on quality, especially flavour. The flavour spectrums of sweet and flavoured pulp from mature ripe fruit of sugar apple heated to 55 °C (critical temperature) and 85 °C (pasteurization temperature) for 20 minutes each, and spray dried with skim and whole milk powders and stored for 12 months, did not differ from those in the fresh pulp. However, heating fresh pulp has the tendency to increase flavour production. Both heat treatments significantly increased the quantities of aroma compounds in the isoprenoid group such as α-pinene, β-pinene, linalool, spathulenol, cineole, limonene, α-copaene, α-farnecene and δ-cadenene, while germacrene, α-cubebene, caryophyllene were found in the 55 °C treatment and aromadendrene, ε-cadenene were found in the 85 °C heated pulp (Shashirekha et al., 2008). Freezing is an alternative method to preserve the quality of fresh produce for long storage durations. Individually quick frozen (IQF) vacuum packaged and

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non-vacuum packaged sugar apples were stored at −18 °C for 12 months. Little discolouration was observed in vacuum packaged fruit, whereas serious discolouration was found in the non-vacuum packaged control. The main phenolic compounds, catechin, chlorogenic acid, eugenol and gallic acid, were higher in the pulp packaged under a vacuum. The discolouration of the pericarp of frozen sugar apple is thought to be O2-involved browning (Wu et al., 1997).

20.10

Conclusions

Sugar apples (Annona squamosa Linn.) and the hybrid atemoyas (A. cherimola Mill. × A. squamosa Linn.) are tropical aggregate fruits with attractive appearance due to their protruding areoles. Sugar apples and atemoya contain high levels of sugars and vitamin C. While fruit softening and fruitlet separation during ripening are the main concern for some sugar apple varieties, fruit cracking and skin blackening are concerns for atemoyas. Fruit softening behaviour during ripening separates sugar apples into two groups: fruit carpel splitting and fruit carpel gelling. Enzymes associated with cell wall degradation need to be investigated to understand their participation in the softening processes. Storage temperatures above 13 °C are ideal and lower temperatures cause chilling injury. Controlled and modified atmosphere storage could effectively extend the storage life, with the optimum atmosphere being 3–5% O2 + 5–10% CO2. 1-MCP fumigation is a practical and promising technique to maintain quality of sugar apple. Sugar apple and atemoya plants can be programmed to produce fruit throughout the year by branch pruning techniques. However, due to their short postharvest shelf life and probably also due to quality problems such as fruit splitting, pulpy flesh and skin blackening and the fact that they contain multiple seeds due to their biological morphology, sugar apples are only a minor fresh commodity in international markets. Research is on-going in the areas listed above and, although there have been some promising results, further research is still needed. Fundamental research using molecular biology to understand and to control ripening is needed. Proper breeding programmes are required to satisfy consumer preferences. New cultivars are needed, with a lower calorie content but with high antioxidant levels. Qualities admired by consumers include a minimum number of seeds, firm fruit, lack of woodiness, consistent flavour, improved external shape and appearance, and lack of skin blackening. Breeding programmes and other research efforts should aim to produce fruit with these properties.

20.11 Acknowledgements We most appreciate Assoc. Prof. Dr Kavit Wanichkul and Mr Ruangsak Komkhuntod, official staff from Kasetsart University, Thailand, for providing us with both informative data and materials of sugar apple and atemoya.

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Plate XXXV (Chapter 20) Appearances of ripe sugar apples cultivated in Thailand: ‘Green Fai’ (a), ‘Purple Fai’ (b), ‘Green Nang’ (c), ‘Purple Nang’ (d), ‘Golden Nang’ (e), ‘Seedless’ (f), ‘Golden Flesh’: atemoya (g) and ‘Pet Pakchong’: atemoya (h).

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21 Tamarillo (Solanum betaceum (Cav.)) W. C. Schotsmans, Institute of Agricultural Research and Technology, Spain, A. East, Massey University, New Zealand and A. Woolf, The New Zealand Institute for Plant & Food Research Limited, New Zealand

Abstract: The tamarillo is a subtropical non-climacteric fruit that produces fruit throughout the year, with fruit production peaking in late summer or autumn. The fruit has an attractive deep red skin and flesh, and a distinctive somewhat acidic flavour. Tamarillos are optimally stored at 3 to 4.5 °C, and 90–95% relative humidity. Lower temperatures will increase the risk of chilling injury. As the fruit mature, the colour changes from green to purple, red, amber and gold, while firmness and titratable acidity decline and the juice yield, soluble solids content (mainly sugars) and pH increase. Stem and calyx quality are important factors from a commercial marketing perspective although they do not affect flavour. Key words: Solanum betaceae, Cyphomandra, tamarillo, tree tomato, tomate de árbol, anthocyanins, stem quality.

21.1

Introduction

21.1.1 Origin, botany, morphology and structure The tamarillo (Solanum betacea, previously known as Cyphomandra betaceae) belongs to the plant family Solanaceae, genus Solanum (Bohs, 1995). The fruit are egg-shaped berries, with attractive, glossy, purple-red to golden yellow skins and orange-red to cream-yellow succulent flesh surrounding the seed locules (see Plate XXXVI in the colour section between pages 238 and 239). Other names commonly used are tree tomato, ‘tomate de palo’, and ‘tomate de árbol’. The name tamarillo was developed in New Zealand as recently as 1970 (Morton, 1987). The exact origin of tamarillo is at present unknown (Popenoe et al., 1989), but it can be found in the Andean regions of Peru, Chile, Ecuador and Bolivia (Morton, 1987) and is categorised in the same Solanaceae family as tomato, eggplant and capsicum (Sale and Pringle, 1999). The plant has spread to Central

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America and the West Indies and New Zealand (Slack, 1976). In the wild, the fruit are generally small, splotchy and yellow or pale red in colour (Popenoe et al., 1989). The large purple-red strains currently found in commercial plantings were developed by nurserymen in New Zealand around 1920, from the then existing yellow and purple strains (Sale and Pringle, 1999) that were introduced by D. Hay & Sons in 1891 (Morton, 1987). The plant is a small, fast-growing and brittle tree, with shallow roots. It grows to a height of 3–5.5 m with a single upright trunk that branches into a few lateral branches (Morton, 1987; Popenoe et al., 1989) which bear the flowers and fruit. The evergreen leaves are large (17 to 30 cm long, 12 to 19 cm wide), shiny, hairy, with prominent veins, and a pungent musky odour. The tree reaches maturity three years after planting and is commercially productive for seven to eight years (Clark and Richardson, 2002). Tamarillo has a modular growth pattern, with each module consisting of three to four leaves with a terminal inflorescence. The inflorescence has a compound structure of up to 50 pale pink or lavender flowers distributed alternately (Lewis and Considine, 1999a). The flowers have five pointed lobes, five yellow stamens and green-purple calyx (Morton, 1987) and open sequentially at two- to three-day intervals, with individual flowers closing at night and reopening each day for up to five days (Lewis and Considine, 1999a). Flowering is continual but usually peaks in late summer or autumn. Tamarillo flowers are self-pollinating but require wind or an insect pollinator to transfer the pollen. The fruit take around 21 to 26 weeks to mature from flowering and since flowering is continual, fruit are also formed year round, with a peak in late autumn and winter (April to November in New Zealand) (Sale and Pringle, 1999). Fruit do not mature simultaneously and several harvests are necessary (Morton, 1987; Popenoe et al., 1989). The fruit is egg-shaped, 4–10 cm long and 3–5 cm wide; it is pointed at both ends and has a long stalk that is left attached for marketing. The skin is smooth, thin and yellow or orange to deep red or almost purple, sometimes with dark, longitudinal stripes. The flesh has the same variation in colour as the skin, ranging from yellow to deep red, or purple. The skin is tough and has an unpleasant flavour. The fruit has a firm texture and numerous thin, nearly flat, circular, large, hard and distinctly bitter seeds in two lengthwise compartments (Morton, 1987). The pulp surrounding the seeds is soft, juicy, subacid to sweet and flavourful, whereas the outer layer of flesh is slightly firm, succulent and bland. In the outmost layers of the flesh, small, hard, irregular, ‘stones’, containing large amounts of sodium and calcium, can appear (Popenoe et al., 1989). Tamarillo is a subtropical fruit and flourishes in regions where temperatures in the growing season are between 16 and 22 °C (Popenoe et al., 1989), while frost (−2.2 °C) will kill all but the larger branches (Morton, 1987). There are no altitude limitations, as they can be found at 1100–2300 m at the equator and near sea level in New Zealand (Popenoe et al., 1989). Fertile, light, well drained soils are needed (Morton, 1987; Popenoe et al., 1989), with good drainage and irrigation, since the trees cannot tolerate drought nor standing water.

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21.1.2 Worldwide importance and economic value The tamarillo is cultivated extensively in most of South America but is mainly used for local consumption and often in a processed form; it is not promoted, resulting in lower quality fruit unsuitable for export. In Ecuador, 3000 ha produce 25 000 tonnes that are consumed within the country at a rate of approximately 1.5 kg/ capita/year (Ojeda et al., 2009). In Colombia about 120 000 tonnes of tamarillo are produced per year on 6500 ha of which the majority is locally consumed (Márquez et al., 2007), but 500 tonnes were exported in 2008 to The Netherlands, France, Canada, Germany and Spain, representing a value of circa €870 000 (Legiscomex, 2008). Infrequent reports indicate the presence of the plant in Kenya (Mwithiga et al., 2007), Uganda (Stangeland et al., 2009), Malaysia (Tee and Lim, 1991), Taiwan (Tseng et al., 2008) and Cuba (Tejeda and Cortes, 1997). Thanks to selection efforts and the development of shipping and storage techniques, tamarillo has been successfully grown in New Zealand (Janet, 2005). Commercial production is located in the north of the North Island, with about 175 growers producing 740 tonnes of fruit on 194 ha, representing a value of circa €700 000 in domestic sales and €550 000 in export sales in 2008 (Aitken and Hewett, 2008). The main export markets for tamarillo from New Zealand are the USA (mainly California), Australia, Hong Kong, Japan, Singapore, and the Pacific Islands. Tamarillo is exported fresh, packed in a cardboard box with each fruit sitting in an individual cup within a tray covered by a polyliner. 21.1.3 Cultivars and genetic variability Although named cultivars seem to exist only in New Zealand, two to four types of tamarillo are distinguished according to their skin colour: purple-red (often divided into purple and red) and yellow (often divided into amber and gold) (Popenoe et al., 1989; Sale and Pringle, 1999; Prohens and Nuez, 2000). Growers often relate the yellowish green leaf colour to the production of yellowish fruit and the purple-green foliage with the production of orangey-red fruit. In New Zealand, the red cultivar ‘Red Beau’ was the standard cultivar but it has significantly declined because of virus sensitivity, being replaced by varieties like ‘Ted’s Red’ and ‘Laird’s Large’. Other named red cultivars include: ‘Oratia’, ‘Red Delight’, ‘Kerikeri Red’, ‘Andy’s Sweet Red’, ‘Red Beauty’, ‘Red Chief’ and ‘Seccombe Red’ (Sale and Pringle, 1999). In the yellow strains, ‘Bold Gold’ is one of the most common cultivars (Sale, 2006) with other named cultivars being ‘Goldmine’, ‘Amberlea Gold’ and ‘Kaitaia Yellow’. The most serious disease affecting tamarillo in New Zealand is tamarillo mosaic potyvirus (TaMV), which results in production of blotchy, streaked unattractive fruit, limiting the production of export grade fruit. Therefore, great effort is going into the development of resistant cultivars (Cohen et al., 2000). 21.1.4 Culinary uses, nutritional value and health benefits The fruit is eaten raw or cooked and can be used as a vegetable like tomato but is also often used in desserts. The skin is always removed, being bitter.

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The red strain is preferred for fresh consumption because of its stronger, more acid flavour. Yellow fruit have a milder flavour and are preferred for canning. The nutritional characteristics (see Table 21.1) of yellow and purple-red cultivars are all within the same range, although significant differences are found between cultivars (Boyes and Strübi, 1997). The main difference between the yellow and purple-red cultivars can be found in the anthocyanin content, which is considerably higher in the purple-red cultivars (Vasco et al., 2008). Tamarillos are low in fat and carbohydrate, low in sodium, and rich in iron, potassium and

Table 21.1 Nutritional characteristics of tamarillo from New Zealand, Ecuador, Spain, Colombia and Uganda. Ranges are presented Parameter

Purple red Min

Diameter (cm) 4.6 Length (cm) 5.5 pH 3.5 Soluble solids content (°Brix) 9.4 Titratable acidity (%) 0.76 Moisture (%) 87 Proteins (%) 2.2 Fat (%) 0.08 Glucose (%) 0.454 Fructose (%) 0.615 Sucrose (%) 0.604 Citric acid (%) 0.77 Malic acid (%) 0.05 Ash (%) 0.69 0.2 Sodium (mg 100 g−1 FW) 238 Potassium (mg 100 g−1 FW) 7.3 Calcium (mg 100 g−1 FW) 14 Magnesium (mg 100 g−1 FW) 0.35 Iron (mg 100 g−1 FW) 14 Vitamin C (mg 100 g−1 FW) 1.31 Antioxidant activity FRAP (mmol 100 g−1 FW) 4.2 Antioxidant activity (μmol TROLOX g−1 FW) 81 Total phenolic content (mg GAE 100 g−1 DM) 163 Anthocyanins (mg 100 g−1 DM) 94.4 Hydroxycinnamic acids (mg 100 g−1 DM) β-carotene (mg g−1 FW) 5.1

Yellow Max

Min

7 8 3.6 13.6 1.71 92 2.2 0.6 1.4 1.412 2.5 2.7 0.53 1.26 8.9 524 26 25.4 0.9 42 1.96 10.3 187 167 96.2 5.2

3.9 5 5.6 7 3.2 3.5 9.3 12.3 1.48 4 86 88 2.4 2.5 0.05 0.72 0.5 1.7 0.7 1.6 1.125 2.979 1.02 2.5 0.07 0.32 0.7 0.82 0.06 4.96 311 440 10.4 25 16 22.5 0.22 0.6 14 33.15 2.6 81 ND 59.44 3.4

Max

6.8 125 ND 60.36 4.6

ND= not detected; where FW = fresh weight: DM = dry matter; FRAP = ferric reducing antioxidant power; GAE = gallic acid equivalents; TROLOX = 6-hydroxy-2,5,7,8-tetramethylchroman-2carboxylic acid Sources: Dawes and Callaghan (1970), Romero-Rodriguez et al. (1994), Boyes and Strübi (1997), Manzano (2005), Leterme et al. (2006), Vasco et al. (2008; 2009), Mertz et al. (2009b) and Stangeland et al. (2009).

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vitamin C (see Table 21.1), and they contribute significantly to the daily intake of vitamins A, B6 and E (Lister et al., 2005). They have a high antioxidant activity, comparable to that of mango (Stangeland et al., 2009), mainly due to the high vitamin C content but low total soluble phenolic content (< 200 mg gallic acid equivalent (GAE) 100 g−1 fresh weight (FW)), and low antiradical efficiency against the 1,1-diphenyl-2-picrylhydrazyl (DPPH•) free radical (Vasco et al., 2008). A full mineral analysis of the fruit is provided by Leterme et al. (2006) and characterisation of the combination of sugars and acids is provided by Heatherbell et al. (1975). The fruit is generally eaten by scooping the flesh from cut halves. Tamarillos can be used in any meal the same way tomatoes would be used: they are poached, fried, grilled, baked, added to stews or casseroles. They are also used to make compote, chutneys, and curries or to add taste or a decorative touch to salads or cheese platters. In Colombia, Ecuador and Sumatra, the fresh fruit are eaten less often, but they are frequently juiced or blended with water and sugar to make a fruit drink. In Ecuadorian folk medicine, the fruit, and more specifically the peel, is considered to be a cholesterol-lowering food and is used as an antimicrobial/ anti-inflammatory treatment for sore throats and inflamed gums (Vasco et al., 2009). An Argentinean community uses the boiled roots of the plant as a treatment for hepatic disorders (Hilgert, 2001).

21.2

Preharvest factors affecting fruit quality

21.2.1 Flowering and pollination In tamarillo, vegetative growth, flower production and fruit set continue over an extended period throughout the warmer months (Clark and Richardson, 2002). Flowering is continual but usually peaks in late summer or autumn, thus leading to an extended harvest period (generally three months for a given cultivar). Tamarillo flowers are self-pollinating but need wind or an insect vector to transfer the pollen. Both honey bees and bumble bees visit tamarillo flowers in New Zealand, but the effective pollination period is only three days, and pollination and fertilisation are essential for fruit development as flowers will drop prematurely if they are not pollinated. Because up to 50 flowers can be found in an inflorescence and flowers open sequentially at two- to three-day intervals, individual inflorescences have open flowers for up to 60 days, and flower buds, flowers and fruitlets can be present simultaneously in an individual inflorescence (Lewis and Considine, 1999a). Only 12% of the flowers set fruit and only 3% develop into mature fruit, and this was not improved if hand pollination was added to the natural pollination. In general, the probability of fruit set decreases with the amount of fruit that has already set in an inflorescence (Lewis and Considine, 1999b). Because of the high level of flower and fruit abscission, yield is very low (Lewis and Considine, 1999b), and a high producing orchard can yield 15 tonnes per ha, which is much lower than, for instance, apples and oranges, which can yield 70 tonnes per ha (Richardson and Patterson, 1993).

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21.2.2 Fruit growth, development and maturation Tamarillo has a double sigmoidal growth curve, with initial slow fruit growth from 20 to 45 days after anthesis (DAA), followed by an accelerated growth phase from 45 to 95 DAA, during which most of the dry matter is accumulated (Ordóñez et al., 2005). After this, growth slows down again. The fruit changes colour at about 60 DAA and soluble solids content (SSC) is maximal around 90 DAA (the red-ripe stage for red fruit), as is the reducing sugar content, with hexoses making up the main part (Ordóñez et al., 2005). Sucrose is not accumulated in tamarillo fruit. The malic acid content is low throughout maturation, whereas the citric acid content increases rapidly during the initial stage of growth, reaching a peak value around 60 DAA (Heatherbell et al., 1982). Starch accumulation is maximal (15.1 mmol kg−1) just before the fruit changes colour (55 DAA) and minimal (2.7 mmol kg−1) at fruit maturity (95 DAA) (Ordóñez et al., 2005). Interestingly, unlike tomatoes, starch accumulation is not correlated with fruit growth or SSC. The best indicator of fruit maturity for red tamarillo is the skin colour, as immature fruit are green, mature fruit are purple, and ripe fruit turn a deep red. With the exception of ‘Bold Gold’, which converts directly from green to yellow, yellow cultivars change from green to red to yellow (Sale and Pringle, 1999). Changes in colour start at the apex, with the flesh around the calyx being the last to change colour. The fruit continues to develop the red colour after harvest, with an increase in SSC and a decrease in titratable acidity (TA) (El-Zeftawi et al., 1988). The anthocyanin concentration in the flesh increases rapidly (up to 1.4 mg g−1 FW) during the early stages of fruit growth, while the anthocyanin concentration in the skin stays low (< 0.1 mg g−1 FW). This accounts for the unpleasant taste of immature tamarillo. As tamarillos mature, the anthocyanin content of the pulp substantially decreases and the content in the skin increases (Heatherbell et al., 1982). If tamarillo fruit are harvested immature, they will have a shorter shelf life, shrivel quickly during storage, and not develop the full red colour (Pratt and Reid, 1976; Sale and Pringle, 1999). Pectins decrease during fruit growth from 1% to 0.75% (Heatherbell et al., 1982). Firmness, juice content and SSC can provide useful complementary information (El-Zeftawi et al., 1988) for assessment of fruit maturity. As with many other fruits, the aroma and typical flavour are the last to develop. In total, 49 aroma and flavour components have been identified, the majority being non-terpenoid alcohols and esters and more specifically, methyl hexanoate, (E)-hex-2-enal, (Z)-hex-3-en-1-ol, eugenol, 4-allyl-2,6-dimethoxyphenol (Torrado et al., 1995), (Z)-3-hexenol, ethyl butyrate (14.8%), methyl butyrate and methyl hexanoate (Wong and Wong, 1997).

21.3

Postharvest physiology and quality

21.3.1 Respiration and ethylene production Tamarillo is a non-climacteric fruit with little respiration and ethylene production after harvest, resulting in a relatively long shelf life (Pratt and Reid, 1976; Sale

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and Pringle, 1999). The respiration rate of tamarillo (0.19–0.25 μmol CO2 kg−1s−1 at 4 °C) slowly decreases after harvest, while the ethylene production (< 0.001 nmol kg−1s−1 at 4 °C) remains low (Pongjaruvat, 2008). Both respiration rate and ethylene production increase at the onset of fruit senescence (Pratt and Reid, 1976), and during shelf life at 20 °C (Pongjaruvat, 2008). 21.3.2 Ripening, quality components and indices As the fruit ripens, its skin develops a full red (or yellow or orange) colour, firmness decreases and the stem changes in colour from green to yellow and eventually detaches. The colour development of red tamarillo fruit is commercially used to assess fruit maturity in New Zealand (Sale and Pringle, 1999). The fruit is considered to be at optimum maturity for harvest and marketing when it is purple, as the red colour will continue to develop after harvest (El-Zeftawi et al., 1988) unless the fruit is harvested when it is still too immature (Pratt and Reid, 1976). In orange tamarillos, redness (a*), yellowness (b*) and lightness (L*) of the skin all increased with ripening (Márquez et al., 2007), whereas in ripe New Zealand ‘Mulligan Red’ red tamarillos (see Fig. 21.1), a*, b*, and C* all decreased while L* remained stable (Pongjaruvat, 2008). In contrast, in Kenyan tamarillos, redness (a*) of the skin increased as yellowness (b*) and lightness (L*) decreased; and the latter correlated well with a decrease in lightness of the pulp and an increase in the SSC of the juice (Mwithiga et al., 2007). Firmness (puncture, compression) decreased as tamarillos ripened (Márquez et al., 2007; Mwithiga et al., 2007; Pongjaruvat, 2008), and firmness (puncture) could be used to predict the internal fruit quality, as its decrease corresponds to an

Fig. 21.1 Changes in colour parameters of tamarillo fruit during storage at 4 °C without shelf life (—), and with three days of shelf life at 20 °C (---) (adapted from Pongjaruvat, (2008)).

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increase in juice yield (Mwithiga et al., 2007). This decrease can probably be related to the increase of soluble pectins during maturation, while pectic acid and protopectins decrease (Heatherbell et al., 1982). The SSC of tamarillo fruit increases during ripening to 10–12 °Brix (El-Zeftawi et al., 1988; Márquez et al., 2007; Mwithiga et al., 2007), pH increases from 3.2–3.7 to 3.4–4.7 (Márquez et al., 2007; Mwithiga et al., 2007) and TA slightly declines (Manzano and Diaz, 2002; Márquez et al., 2007). These changes result in an increase in the SSC/TA ratio (Pongjaruvat, 2008) and thus a higher sensory flavour rating (El-Zeftawi et al., 1988). As the fruit ripens, the stem changes in colour from green (see Plate XXXVIIE in the colour section) to yellow (see Plate XXXVIIF in the colour section) because of accelerated water loss and chlorophyll degradation, and eventually detaches (Pongjaruvat, 2008).

21.4

Postharvest handling factors affecting quality

21.4.1 Handling and grading Because flower production and fruit set continue over an extended period, not all the fruit on a tree mature at the same time, and multiple harvests are needed. Tamarillo fruit are harvested by hand and packed with the stems attached. The healthy and intact green stems of tamarillo fruit influence consumer and marketing perception and are required to satisfy export standards (Sale and Pringle, 1999). Grading of fruit is generally done based on size, and misshapen and blemished fruit are removed. Fruit are generally packed into plastic pocket packs and placed inside polyethylene-lined single layer trays. Polyliners are essential to prevent excessive weight loss and fruit shrivelling during long-term storage, because they ensure a higher relative humidity (RH) surrounding the fruit. However, this is accompanied by a higher likelihood of fruit rots. 21.4.2 Temperature Cooling tamarillo fruit below 7 °C will slow softening, weight loss, TA reduction and colour change (Espina and Lizana, 1991; Manzano and Diaz, 2002; Pongjaruvat, 2008); however, the optimal temperature is lower, at 3 to 4.5 °C (Harman and Patterson, 1984). Temperatures below this optimal (e.g. 0–2 °C) will increase the risk of chilling injury (CI) and will cause more discolouration of the calyx and stem, while fungal decay occurs on the stem and calyx if stored above 4.5 °C (Espina and Lizana, 1991). Storage at 4 °C slows fruit metabolism, and the deterioration of the stem through a marked decrease in moisture loss and chlorophyll degradation and prevention of an increase in polyphenoloxydase activity (Pongjaruvat, 2008). The maximum storage duration will of course depend on a range of preand postharvest factors, but a storage duration of six weeks should be achieved relatively easily using optimum temperature management. Storage for up to nine weeks is possible, and the maximum generally limited by expression of

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post-storage rots, these being significantly influenced by orchard factors (Woolf and Jackman, unpublished data).

21.4.3 Relative humidity A RH between 90% and 95% is optimal for tamarillo (Harman and Patterson, 1984). Lower RH, such as when tamarillo fruit are stored in open trays (23 °C, 65% RH), will result in considerable loss of moisture (12% in 14 days) and hence a decrease in marketable weight (Márquez et al., 2007). Using polyliners in the trays and thus increasing RH will reduce weight loss to 0.3–0.5% (in 14 days) when stored at 4 °C and will retain firmness (compression) better (Pongjaruvat, 2008).

21.4.4 Ethylene Applying ethylene will accelerate fruit ripening through a stimulation of respiration, a decrease in firmness, development of red skin colour and yellow flesh colour, and an increase in the ratio of SSC to TA (Pratt and Reid, 1976; Prohens et al., 1996).

21.4.5 Modified and controlled atmosphere Little information is available regarding modified atmosphere packaging (MAP) of tamarillo. MAP (3–4 kPa O2 and 4–7 kPa CO2) delayed the development of stem yellowing, but did not improve fruit quality, and increased stem blackening and ‘bleeding’ (diffusing red pigment) in the locule (Pongjaruvat, 2008).

21.4.6 Special treatments Submersion in a citric acid solution was effective in slowing down the SSC increase and TA decrease and increasing the shelf life (30 °C and 80% RH) of fruit from six to ten days (Moreno-Álvarez et al., 2007).

21.5

Crop losses

21.5.1

Physiological disorders

Chilling injury Tamarillos are sensitive to CI at temperatures lower than 3 °C. CI symptoms include scald (brown discolouration), surface pitting, and increased susceptibility to decay (Harman and Patterson, 1984; Espina and Lizana, 1991). Deterioration of the fruit stem and calyx As mentioned previously, deterioration of the fruit stem and calyx is a problem in tamarillo, since a healthy fruit calyx (see Plate XXXVIIA in the colour section)

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and stem (see Plate XXXVIIE in the colour section) are requirements for export, and factors that are considered by importers and wholesalers, despite it being purely an aesthetic problem that does not affect the fruit flesh quality or taste. Calyx lifting (see Plate XXXVIIC in the colour section) and blackening (see Plate XXXVIID in the colour section) show up after 28 days of storage at 4 °C and increase rapidly during subsequent shelf life, whereas stem yellowing (see Plate XXXVIIF in the colour section) and blackening (see Plate XXXVIIG in the colour section) are already obvious from 14 days onwards. Physical damage and fast loss of moisture after harvest are the main reasons for these stem and calyx problems (Sale and Pringle, 1999). Physical abrasion, such as occurs during brushing during packing, can also promote browning and blackening. Additionally, the colour changes of the stem from green to yellow have been associated with accelerated chlorophyll degradation (Pongjaruvat, 2008), and stem blackening with increased polyphenol oxidase activity (Sale and Pringle, 1999; Pongjaruvat, 2008). Several treatments, such as the application of wax to the stem and MAP to reduce water loss, have been tested to reduce stem browning, with little success. Eugenol, an antibacterial additive, has been shown to delay stem dehydration browning in cherry (Serrano et al., 2005) and table grape (Valverde et al., 2005; Valero et al., 2006), keeping their stems healthy, but when tried in MAP for tamarillo it did not show the same beneficial effect (Pongjaruvat, 2008). Other Colour leaching from the locules into the pericarp can occur, making the pericarp more red. The circumstances in which this happens have not been determined, but adverse atmospheric conditions seem to be one of the elicitors. 21.5.2 Pathological disorders Fungal infections due to field contamination dramatically reduce storage life of tamarillo fruit and these have not been successfully prevented by preharvest treatments (Sale and Pringle, 1999). The common fungal attacks are bitter rots, as circular and brown-black spots caused by Glomerella cingulata, Colletotrichum acutatum, C. gleosporoides, Phoma exigua, or Diaporthe phaseolorum (Hampton et al., 1983; Blank et al., 1987; Sale and Pringle, 1999; Manning and Woolf, unpublished data), and stem-end rots, as a soft brown rot occurring around the base of the stem caused by Botrytis (Sutton and Strachan, 1971) and possibly Phomopsis (Manning and Woolf, unpublished data). Application of captafol and benomyl field sprays in combination with a prochloraz and imazalil postharvest dip has been shown to improve fruit storability (Blank et al., 1987). The use of irradiation successfully inhibited the stem-end rots during storage, but this method caused tamarillo fruit tissue to be sensitive to low temperature injury, resulting in tissue breakdown and discolouration during cold storage (Sutton and Strachan, 1971). Hot water dips (50 °C for 8 min) directly after harvest successfully remove latent infections but

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can cause damage to the stem and the wax layer of the skin, which can result in higher levels of weight loss and susceptibility to invasion of secondary fungi (Yearsley et al., 1987). The commercial application of hot water dips is difficult, as tamarillo do not float (Hampton et al., 1983). When complementing these heat treatments with a postharvest fungicide dip (such as imazalil) and waxing, fruit can be stored for eight weeks at 3.5 °C followed by seven days at 20 °C (Yearsley et al., 1987). Although the hot water dip reduces fungal rots, it cannot prevent stem discolouration. Tamarillos produce a broad-spectrum invertase inhibitory protein that has antifungal and antibacterial activity and is involved in the plant defence mechanism (Ordóñez et al., 2000; 2006). 21.5.3 Insect pests and their control Tamarillos are generally regarded as pest-resistant, although they can be attacked by green aphids and fruit flies; and greenhouse thrips can cause damage to small fruit, which results in scaring (Rheinlander and colleagues, unpublished data). Aphids need to be controlled well, especially since they often spread viruses. Good orchard hygiene, pruning and weed control are the main techniques used to avoid aphid infection. Fruit fly can present a problem when exporting to countries with quarantine restrictions, but can be controlled using dimethoate or fenthion dipping or flood spraying, or using methyl bromide fumigation; but none of these is accepted in organic production.

21.6

Processing

Tamarillo fruit process extremely well. They can be frozen or canned and can be used for a range of products including jams, pulps, purees, chutneys, and juices. There is considerable potential for combining with milk products such as yogurts. The yellow cultivars are especially preferred for processing because of their average size, good flavour and because they contain fewer anthocyanins. The last factor is important to prevent reaction with the metal of the cans, which can cause blue discolouration of the product (Portela, 1999). More recently, tamarillo wine was produced in Venezuela with chemical and organoleptic characteristics similar to those of wine made from grapes (Alvarez et al., 2007). Processing is best carried out after removing the skin layer and the seeds because of the bitter nature of these components (Belén-Camacho et al., 2004). Extraction of carotenoids and anthocyanins from this material may be useful as a source of natural food colourants (Bobbio et al., 1983) or as functional food ingredients. Duran and Moreno-Alvarez (2000) optimised solvent mixtures and application to enable high carotenoid extraction from the pericarp. Belén-Camacho et al. (2004) characterised the oil content of both red and yellow cultivar seeds in order to assess their potential as raw material for a unique oil product manufacture. Thermal processing, such as pasteurisation, is often used to preserve fruit products. Thermal treatment of yellow tamarillo nectar can result in reduced

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vitamin C and carotenoid content of the final product in comparison with that of fresh nectar (Mertz et al., 2009a). Extraction of the effective broad-spectrum invertase inhibitory protein produced by the fruit may also be a useful resource as a natural biocide for reduction of postharvest losses in horticultural products (Ordóñez et al., 2006). Tamarillo and its processed products (in the form of juice and pomace) are considered good sources of antioxidants that could be used to make nutraceutical or functional-food products (Ordóñez et al., 2010).

21.7

Conclusions

The tamarillo is a subtropical fruit from the Solanaceae family, originating probably from the Andes. Different types of tamarillo are distinguished according to their skin colour, ranging from red to yellow, but no major differences in physiology have been noted besides the presence of anthocyanins in the red types and the absence of them in the yellow types. Tamarillo has an extended flowering and fruiting period, with a peak in fruit production in late autumn and winter. It is a non-climacteric fruit with little respiration and ethylene production after harvest, but ethylene can be used to accelerate fruit ripening. Tamarillos are optimally stored at 3 to 4.5 °C, and 90–95% RH, and lower temperatures will increase the risk of chilling injury. As fruit mature, their skin colour changes, and the juice yield, SSC, pH and SSC/TA ratio increase and firmness and TA decline. Stem and calyx quality are important factors and these also represent the main quality problem and the main challenge for the future. Tamarillo fruit adapt very well to processing and can be used as a vegetable in a manner similar to tomato, but are also often used in sweet preparations.

21.8

References

Aitken A G and Hewett E W (2008), FreshFacts: New Zealand Horticulture 2008. Auckland, HortResearch – The Horticulture & Food Research Institute of New Zealand Ltd. Alvarez R A, Manzano J E, Materano W and Valera A (2007), ‘Caracterización química y organoléptica de vino artesanal de tomate de arbol Cyphomandra betaceae (Cav.) Sendth’, Proc Interamerican Soc Tropic Hortic, 51, 163–166. Belén-Camacho D R, Sánchez E D, Garcia D, Moreno-Álvarez M J and Linares O (2004), ‘Características fisicoquímicas y composición en ácidos grasos del aceite extraído de semillas de tomate de árbol (Cyphomandra betacea Sendt) variedades roja y amarilla’, Grasas Aceites, 55, 428–433. Blank R H, Dance H M, Hampton R E, Olson M H and Holland P T (1987), ‘Tamarillo (Cyphomandra betacea): effect of field-applied fungicides and post-harvest fungicide dips on storage rots of fruit’, N Z J Exp Agric, 15, 191–198. Bobbio F O, Bobbio P A and Rodriguez-Amaya D B (1983), ‘Anthocyanins of the Brazilian fruit Cyphomandra betacea’, Food Chem, 12, 189–195. Bohs L (1995), ‘Transfer of Cyphomandra (Solanaceae) and its species to Solanum’, Taxon, 44, 583–587. Boyes S and Strübi P (1997), ‘Organic acid and sugar composition of three New Zealand grown tamarillo varieties (Solanum betaceum (Cav.))’, N Z J Crop Hortic Sci, 25, 79–83.

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Clark C J and Richardson A C (2002), ‘Biomass and mineral nutrient partitioning in a developing tamarillo (Cyphomandra betacea) crop’, Sci Hortic, 94, 41–51. Cohen D, van den Brink R C, MacDiarmid R M, Beck D L and Forster R L S (2000), ‘Resistance to tamarillo mosaic virus in transgenic tamarillos and expression of the transgenes in F1 progeny’, Proc XXV Internat Hortic Congress, Pt 11, 43–49. Dawes S N and Callaghan M E (1970), ‘Composition of New Zealand fruit. 1. Tamarillo’, N Z J Sci, 13, 447–451. Durán M G and Moreno-Álvarez M J (2000), ‘Evaluación de algunas mezclas de solventes en la extracción de carotenoides del pericarpio de tamarillo (Cyphomandra betacea Sendt)’, Cienc Tecnol Alim, 31, 34–38. El-Zeftawi B M, Brohier L, Dooley L, Goubran F H, Holmes R and Scott B (1988), ‘Some maturity indices for tamarillo and pepino fruits’, J Hortic Sci, 63, 163–169. Espina S and Lizana L A (1991), ‘Comportamiento de tamarillo (Cyphomandra betacea (Cav.) Sendtner) en almacenaje refrigerado’, Proc Interamerican Soc Tropic Hortic, 35, 285–290. Hampton R E, Blank R H, Dance H M and Olson M H (1983), ‘Tamarillo storage rot problems’, Proc 36th N Z Weed Pest Control Conf., 121–124. Harman J E and Patterson K J (1984), Kiwifruit, tamarillos and feijoas maturity and storage effects on keeping and eating quality, Wellington, New Zealand, Agrilink Horticultural produce and practice No. 103. Heatherbell D A, Reid M S and Wrolstad R E (1982), ‘The tamarillo-chemical composition during growth and maturation’, N Z J Sci, 25, 239–243. Heatherbell D A, Surawski J R and Withy L M (1975), ‘Identification and quantitative analysis of sugars and non-volatile acids in tamarillo fruit (Cyphomandra betacea)’, Confructa, 20, 17–22. Hilgert N I (2001), ‘Plants used in home medicine in the Zenta River basin, Northwest Argentina’, J Ethnopharmacol, 76, 11–34. Janet S (2005), Tariff and Trade Barriers. Wellington, New Zealand Horticulture Export Authority. Legiscomex (2008), ‘Frutas exóticas en Colombia/Inteligencia de mercados’, www. legiscomex.com/BancoMedios/Documentos%20PDF/est_col_frutas_exot_6.pdf [accessed May 2011]. Leterme P, Buldgen A, Estrada F and Londoño A M (2006), ‘Mineral content of tropical fruits and unconventional foods of the Andes and the rain forest of Colombia’, Food Chem, 95, 644–652. Lewis D H and Considine J A (1999a), ‘Pollination and fruit set in the tamarillo (Cyphomandra betacea (Cav.) Sendt.) 1. Floral biology’, N Z J Crop Hortic Sci, 27, 101–112. Lewis D H and Considine J A (1999b), ‘Pollination and fruit set in the tamarillo (Cyphomandra betacea (Cav.) Sendt.) 2. Patterns of flowering and fruit set’, N Z J Crop Hortic Sci, 27, 113–123. Lister C E, Morrison S C, Kerkhofs N S and Wright K M (2005), ‘The nutritional composition and health benefits of New Zealand tamarillos’, Crop & Food Research Confidential Report No. 1281. Manzano J E (2005), ‘Caracterización de frutos de tomate de arbol (Cyphomandra betaceae Cav. Sendtn.) y sus relativos en zonas montañosas de Venezuela’, Proc Interamerican Soc Tropic Hortic, 48, 149–151. Manzano J E and Diaz J G (2002), ‘Características de calidad en frutos almacenados de tomate de arbol [Cyphomandra betaceae (Cav.) Sendtn.]’, Proc Interamerican Soc Tropic Hortic, 46, 68–69. Márquez C J, Otero C M E and Cortés M R (2007), ‘Cambios fisiológicos, texturales, fisicoquímicos y microestructurales del tomate de árbol (Cyphomandra betacea S.) en poscosecha’, Vitae, 14, 9–16. Mertz C, Brat P, Caris-Veyrat C and Gunata Z (2009a), ‘Characterization and thermal lability of carotenoids and vitamin C of tamarillo fruit (Solanum betaceum Cav.)’, Food Chem, 119, 653–659.

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Mertz C, Gancel A L, Gunata Z, Alter P, Dhuique-Mayer C, et al. (2009b), ‘Phenolic compounds, carotenoids and antioxidant activity of three tropical fruits’, J Food Compos Anal, 22, 381–387. Moreno-Álvarez M J, Pinto M G, García Pantaleón D and Belén-Camacho D R (2007), ‘Efecto del ácido cítrico sobre la madurez del tomate de árbol’, Rev Facultad Agron (LUZ), 24, 321–342. Morton J (1987), Tree Tomato, Fruits of Warm Climates, Miami, Florida: Morton, Julie F. Mwithiga G, Mukolwe M I, Shitanda D and Karanja P N (2007), ‘Evaluation of the effect of ripening on the sensory quality and properties of tamarillo (Cyphomandra betaceae) fruits’, J Food Eng, 79, 117–123. Ojeda A M, Bermeo S P, Bastidas A R and Muñoz C (2009), ‘Produccion y comercializacion de tamarillo (Cyphomandra betacea Sent), para el mercado internacional’, Escuela Superior Politécnica del Litoral, Quito, Ecuador. Ordóñez R M, Cardozo M L, Zampini I C and Isla M I (2010), ‘Evaluation of antioxidant activity and genotoxicity of alcoholic and aqueous beverages and pomace derived from ripe fruits of Cyphomandra betacea Sendt.’, J Agric Food Chem, 58, 331–337. Ordóñez R M, Isla M I, Vattuone M A and Sampietro A R (2000), ‘Invertase proteinaceous inhibitor of Cyphomandra betacea Sendt fruits’, J Enz Inhib Med Chem, 15, 583–596. Ordóñez R M, Ordóñez A A L, Sayago J E, Nieva Moreno M I and Isla M I (2006), ‘Antimicrobial activity of glycosidase inhibitory protein isolated from Cyphomandra betacea Sendt. fruit’, Peptides, 27, 1187–1191. Ordóñez R M, Vattuone M A and Isla M I (2005), ‘Changes in carbohydrate content and related enzyme activity during Cyphomandra betacea (Cav.) Sendtn. fruit maturation’, Postharvest Biol Technol, 35, 293–301. Pongjaruvat W (2008), Effect of Modified Atmosphere on Storage Life of Purple Passion Fruit and Red Tamarillo, Palmerston North, New Zealand, Massey University. Popenoe H L, King S R, León J, Kalinowski L S and Vietmeyer N D (1989), Lost Crops of the Incas: Little-known Plants of the Andes with Promise for Worldwide Cultivation, Washington, D.C., The National Academy Press. Portela S I (1999), ‘Fisiología y manejo de poscosecha del tamarillo (Cyphomandra betacea)’, Av Hortic, 4, 40–50. Pratt H K and Reid M S (1976), ‘The tamarillo: fruit growth and maturation, ripening, respiration, and the role of ethylene’, J Sci Food Agric, 27, 399–404. Prohens J and Nuez F (2000), ‘The tamarillo (Cyphomandra betacea): A review of a promising small fruit crop’, Small Fruits Review, 1, 43–68. Prohens J, Ruiz J J and Nuez F (1996), ‘Advancing the tamarillo harvest by induced postharvest ripening’, HortScience, 31, 109–111. Richardson A and Patterson K (1993), ‘Tamarillo growth and management’, Orchardist, 66, 33–35. Romero-Rodriguez M A, Vazquez-Oderiz M L, Lopez-Hernandez J and Simal-Lozano J (1994), ‘Composition of babaco, feijoa, passion-fruit and tamarillo produced in Galicia (NW Spain)’, Food Chem, 49, 251–255. Sale P (2006), ‘Some interesting developments and the odd hiccup in the 2006 tamarillo season’, Orchardist, 79, 52–55. Sale P and Pringle G (1999), The Tamarillo Handbook: A Guide for New Zealand Growers and Handlers, Kerikeri, New Zealand, New Zealand Tamarillo Growers Association Inc. Serrano M, Martínez-Romero D, Castillo S, Guillén F and Valero D (2005), ‘The use of natural antifungal compounds improves the beneficial effect of MAP in sweet cherry storage’, Inn Food Sci Emerg Technol, 6, 115–123. Slack J M (1976), ‘Growing tamarillos’, Agric Gazette, 86, 2–4. Stangeland T, Remberg S F and Lye K A (2009), ‘Total antioxidant activity in 35 Ugandan fruits and vegetables’, Food Chem, 113, 85–91. Sutton H C and Strachan G (1971), ‘An attempt to control Botrytis rot in tamarillos (Cyphomandra betacea (Cav). Sendt) by electron irradiation’, N Z J Sci, 14, 1097–1106.

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Tee E S and Lim C L (1991), ‘Carotenoid composition and content of Malaysian vegetables and fruits by the AOAC and HPLC methods’, Food Chem, 41, 309–339. Tejeda T and Cortes S (1997), ‘Phenological behaviour of tree tomato (Cyphomandra betacea (Cav.) Sendt), in Cuba, during initial stages of establishment’, Cultivos tropicales, 18, 43–46. Torrado A, Suárez M, Duque C, Krajewski D, Neugebauer W and Schreier P (1995), ‘Volatile constituents from tamarillo (Cyphomandra betacea Sendtn.) fruit’, Flavour Fragr J, 10, 349–354. Tseng Y H, Liou C Y, Liu S C and Ou C H (2008), ‘Cyphomandra betacea (Cav.) Sendt. (Solanaceae), a newly naturalized plant in Taiwan’, Quarterly Journal of Chinese Forestry, 41, 425–429. Valero D, Valverde J M, Martínez-Romero D, Guillén F, Castillo S and Serrano M (2006), ‘The combination of modified atmosphere packaging with eugenol or thymol to maintain quality, safety and functional properties of table grapes’, Postharvest Biol Technol, 41, 317–327. Valverde J M, Guillén F, Martínez-Romero D, Castillo S, Serrano M and Valero D (2005), ‘Improvement of table grapes quality and safety by the combination of modified atmosphere packaging (MAP) and eugenol, menthol, or thymol’, J Agric Food Chem, 53, 7458–7464. Vasco C, Avila J, Ruales J, Svanberg U and Kamal-Eldin A (2009), ‘Physical and chemical characteristics of golden-yellow and purple-red varieties of tamarillo fruit (Solanum betaceum Cav.)’, Int J Food Sci Nutr, 60, 278–288. Vasco C, Ruales J and Kamal-Eldin A (2008), ‘Total phenolic compounds and antioxidant capacities of major fruits from Ecuador’, Food Chem, 111, 816–823. Wong K C and Wong S N (1997), ‘Volatile constituents of Cyphomandra betacea Sendtn. fruit’, J Essential Oil Res, 9, 357–359. Yearsley C W, McGrath H J W and Dale J R (1987), ‘Red tamarillos (Cyphomandra betacea): post-harvest control of fungal decay with hot water and imazalil dips’, N Z J Exp Agric, 15, 223–228.

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Plate XXXVI

(Chapter 21) Tamarillo fruit.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

Plate XXXVII (Chapter 21) Healthy tamarillo calyx (a, b), calyx lifting (c) and blackening (d). Healthy stem (e), stem yellowing (f ), stem blackening (g) (pictures courtesy of The New Zealand Institute for Plant & Food Research Limited).

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22 Tamarind (Tamarindus indica L.) E. M. Yahia, Autonomous University of Queretaro, Mexico and N. K.-E. Salih, Agricultural Research Corporation, Sudan

Abstract: Tamarindus indica L., commonly known as tamarind, is a multipurpose long-lived tree best known for its fruit. It is indigenous to tropical Africa and exotic to Asia and Central America. India and Thailand are the major tamarind world producers, generating 300 000 and 140 000 tons annually, respectively. There are two main types of tamarind: sour (the most common) and sweet (mostly comes from Thailand). Tamarind can be eaten fresh (ripe or unripe) and it can be consumed processed into different products. In addition to the use of tamarind fruit in food it has many uses in the pharmacological industry and folk medicine. The ripe tamarind pods are susceptible to different pest and diseases, especially when grown in a big plantation. This chapter will describe the nutritional importance and the postharvest handling of tamarind. Key words: Tamarindus indica, postharvest, handling, nutrition, storage, processing.

22.1

Introduction

22.1.1 Origin, botany, morphology and structure Tamarindus indica L. (syns. T. occidentalis Gaertn, T. officinalis Hook, T. umbrosa Salisb) belongs to the family leguminaceae (syns. Fabaceae) and subfamily Caesalpinaceae. The genus Tamarindus is monotypic, i.e. it contains a single species. Commonly, Tamarindus indica is known as tamarind (the trade and English name). In Spanish and Portuguese, it is called tamarindo; in French, tamarinier, tamarinde; in Dutch and German, tamarinde; in Italian, tamarindizio; in Hindi, it is known as tamarind, tamrulhindi and it has other local names as well (e.g. ambli, imli, chinch, etc.). In the eighteenth century, Linnaeus gave it the name Tamarindus indica, inspired by the Arabic name tamar-ul-Hind, meaning date of India. Tamarind is widespread throughout the tropics and subtropics and grows in more than 50 countries in Africa, Asia and Central America. It most probably

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originated in tropical Africa (Coates-Palgrave, 1988), although there is a common belief that tamarind is native to India (Morton, 1987) where it is believed to have been introduced thousands of years ago (Hort, 1916), and to have reached Central America in the seventeenth century with the Spanish and Portuguese (Patino, 1969). According to Salim et al. (1998) in Africa tamarind is native to Burkina Faso, the Central African Republic, Chad, Eritrea, Ethiopia, Gambia, Guinea, Guinea-Bissau, Kenya, Madagascar, Mali, Mozambique, Niger, Nigeria, Senegal, Sudan, Tanzania, Uganda and Zimbabwe and exotic to Mauritania, Togo, Cote d’Ivoire, Egypt, Libya, Ghana, Zambia and Liberia. Also, tamarind is exotic to Australia, Asia (Afghanistan, China, Bangladesh, India, Indonesia, Iran, Laos, Malaysia, Nepal, Pakistan, Philippines, Myanmar, Sri Lanka, Thailand, Papua New Guinea, Cambodia, Vietnam and Brunei) and the Americas (Brazil, Colombia, Cuba, Dominican Republic, Guatemala, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Puerto Rico and southern United States of America). It is widely used in Mexico (see Plate XXXVIII in the colour section between pages 238 and 239), especially in the preparation of drinks (tamarind water, tamarind juices) and desserts. Tamarind is an evergreen or semi-evergreen bushy tree that has a dense foliage crown. It is a slow growing tree; the annual growth rate of seedlings is about 60 cm and the juvenile stage takes between four and five years, but trees can reach up to 200 years of age. The tamarind tree can reach a maximum height of up to 20–30 m, with bole 1–2 m and trunk diameter 1.5–2 m (Jambulingam and Fernandes, 1986; Stross, 1995). Leaves are bright green in color, alternate and compound with 10–18 pairs of leaflets (see Plate XXXIXA in the colour section). Leaflets are 1.2–3.2 × 0.3–1.1 cm in size, petiolate, and rounded at the apex. Flowers are bisexual, 2.5 cm wide, five-petalled, borne in small racemes, and yellow with orange or red streaks. Buds are pink with 4 sepals and 5 petals. The fruit is a curved or straight pod with rounded ends, 12 to 15 cm in length, covered with a hard brown exterior shell. Fruit pulp is brown or reddish-brown when mature and the fruit pod contains between 1 and 12 flat and glossy brown seeds. Tamarind pulp, seeds and shell are about 55%, 34%, and 11%, respectively, of the tamarind fruit (Rao and Srivastava, 1974). The seed is made up of the seed coat or testa (20–30%) and the kernel or endosperm (70–80%). The shell is light greenish or scruffy brown in color (see Plate XXXIXB in the colour section). The shell is scaly and irregularly constricted between seeds; it is also brittle and easily broken when pressed. The pulp is soft and thick (Coronel, 1991; Purseglove, 1987). The seeds are 1.6 cm long, very hard, shiny, smooth and reddish or purplish brown in color with irregular shape and are joined to each other with tough fibers (Purseglove, 1987). Tamarind pods usually contain 1–12 seeds but the Indian pods contain 6–12 seeds, and are usually longer than the African and South American pods. There are two main types of tamarind: sour (the most common) and sweet (which mostly comes from Thailand). The tamarind tree has the capability to withstand long periods of drought because of its deep tap rooting and extensive lateral rooting system, and also the ability to grow in poor soils because of their nitrogen fixing property (Felker, 1981; Felker and Clark, 1980).

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22.1.2 Worldwide importance and economic value Tamarind is economically valuable and multi-purpose insofar as almost every part of the tree has a use, but the tree is best known for its fruit and the marketability of tamarind fruit has increased consistently over the years. The tamarind major production area is in Asia, where India is considered the major producer with a production of 300 thousand tons annually (El-Siddig et al., 2006) (Tables 22.1 and 22.2). According to the spices board of India, the production area was 58 624 ha in 2006–2007 and the export was 10 200 tons. The potential for Indian export in the past 5 years shows a good market for tamarind, especially in the Gulf Countries and Europe (Kumar and Bhattacharya, 2008). Thailand is the second major producer of tamarind, with 140 thousand tons produced in 1995 (Yaacob and Subhadrabandhu, 1995), and the export amounted to about 7000 tons in 1999. Sri Lanka exported 6903 tons of tamarind in 1997. Other Asian countries produce and export tamarind but on a much smaller scale compared to India and Thailand. In the Americas, Costa Rica produces about 220 tons of tamarind annually and is considered quite a large producer. The annual production of tamarind amounts to 37 tons in Mexico and 23 tons in Puerto Rico (Bueso, 1980). The Asian tamarind is mainly exported to Asian countries, Europe and North America, while the Table 22.1 Area (hectares), production and export (tons) and values (Rs. millions) of tamarind from India Year

Area

Production

Export

Values

2002–03 2003–04 2004–05 2005–06 2006–07 2007–08 2008–09

61 958 60 629 61 624 61 084 58 624 – –

178 974 183 871 194 032 192 186 190 073 – –

– –

– – 1833.98 3078.20 3000.00 3100.00 4105.00

5 944 14 101 10 200 11 250 11 500

Source: Spices Board India, Ministry of Commerce and Industry, Gov. of India. http://www.indianspices.com/

Table 22.2 Quantities (tons) and values (RS. millions) of different commodities of tamarind exported from India Commodity

Dried Fresh Flour meal Seeds

Quantity

Value

2000–01

2001–02

2000–01

2001–02

7071.14 2278.59 572.08 2997.39

4594.58 1434.15 817.97 887.38

151.782 33.932 11.348 47.131

109.667 23.988 15.528 19.322

Source: Spices Board India, Ministry of Commerce and Industry, Gov. of India. http://www.indianspices.com/

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American tamarind is mainly exported to North America and Europe. In most of the producing countries, tamarind does not grow on a commercial scale, and fruits are collected from the wild and home gardens. Although widespread in Africa, no African country cultivates tamarind on a commercial scale and almost all of the produce is consumed locally. Similarly, most of the tamarind produced in India and Thailand is also consumed locally. The sour tamarind is the most widespread; it comprises 95% of the total world production. Thailand is the largest producer of sweet tamarind, being 30% of its crop. 22.1.3 Culinary uses, nutritional value and health benefits Tamarind fruit pulp has many uses in domestic and industrial food and medicine and is considered the most valuable part of the tree. In most tamarind-producing countries, rural households dry tamarind pods in the sun, separate pulp from the fibers, seeds and shells, and compress and pack pulp in palm leaf mats, baskets, corn husks, jute bags, earthenware pots or plastic bags. The fruit pulp is a common ingredient in curries, sauces, and certain beverages. Ripe tamarind pulp, especially the sweet tamarind, is often eaten fresh. Both sour and sweet ripe tamarind pulps are also consumed processed in desserts, pickles, jams, candy, juice, porridge and drinks. Tamarind, especially the unripe pulp, is used as a spice and sauce in many Asian cuisines. In India a pickle made from tamarind pulp is used as seasoning to prepare fish. Also, unripe fruit dipped in salt or wood ash is eaten as a snack. Tamarind juice is very popular in many countries; a refreshing drink is prepared from the pulp water extract mixed with wood ash or sugar. In Eastern Africa, porridge is prepared from pulp juice cooked with sorghum or maize. Sometimes the pulp juice is fermented into an alcoholic beverage. In Burkina Faso, tamarind pulp extract is used to purify drinking water (Bleach et al., 1991). In many Asian countries tamarind balls are made from the pulp mixed with sugar. In Thailand, the pulp is mixed with salt, compressed and packed in plastic bags. In East India, the pulp is covered with salt, rolled into balls, exposed to dew and stored in earthenware jars (Chapman, 1984; Morton, 1987), whereas in Java, the salted pulp is rolled into balls, steamed and sun-dried, then exposed to dew for a week before packing in stone jars. In Sri Lanka, the dried pulp is mixed with salt, packed in clay pots and kept in a dry place; seedless pulp is stored in plastic bags in retail shops (Gunasena, 1997). Tamarind seeds are eaten, roasted or boiled, during off-seasons and food shortages. Roasting the seeds is usually followed by decorticating the testa from the edible kernel. Roasted tamarind seeds can also be used as a substitute for coffee. The seed oil is edible and has many culinary uses. Of the tamarind seed kernel, 46 to 48% consists of a gel-forming substance, known as jellose or polyose, which has many applications in the food industry. Jellose is mainly a polysaccharide and can be used for the preservation, thickening, stabilizing and gelling of food (Gliksman, 1986; Chen et al., 1988; Kawaguchi et al., 1989). Unlike fruit pectin, tamarind seed polysaccharide is characterized by its ability to form gels over a

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wide range of pHs and gelatinizes with sugar concentrates in cold neutral aqueous solutions (Savur, 1948). Also, tamarind polysaccharides are heat resistant and are not affected by long boiling periods, while fruit pectin degrades to one-third of its original value after one hour of boiling. Tamarind kernel powder (TKP) is a more effective gelling agent when combined with other gums (Yin and Lewis, 1981). Protein concentrates have also been made from tamarind kernel powder (Rao and Subramanian, 1984) and can be used to prepare jelly, and fortified bread and biscuits (Bhattacharya, 1990; Bhattacharya et al., 1994). The shelf life of fish can be extended by using TKP as a film forming gum (Shetty et al., 1996). Tamarind fruit pulp is a good source of minerals and a rich source of riboflavin, thiamin, and niacin, but it is poor in vitamins A and C (Table 22.3). Shankaracharya (1998) found that the whole tamarind seed contains 13% crude protein, 6.7% crude fiber, 4.8% crude fat and 5.62% tannins. Also, the seed contains good phytic acid, pentose, mannose, and glucose as principal soluble sugars (Ishola et al., 1990) as well as valuable amino acids (Shankaracharya, 1998; Bhattacharya et al., 1994). Bhattacharya et al. (1994) showed that tamarind seed is rich in glutamic acid, aspartic acid, glycine, and leucine, but deficient in sulphur-containing amino acids. The edible seed kernel was reported to be rich in phosphorus, potassium, and magnesium, but has a calcium content comparable with other cultivated

Table 22.3

Nutrition constituents of tamarind pulp per 100 g

Constituent

Amount per 100 g

Energy Moisture Protein Fat Fiber Carbohydrates Invert sugars (70% glucose; 30% fructose) Ash Calcium Phosphorus Iron Sodium Potassium Vitamin A Thiamine Riboflavin Niacin Ascorbic acid Tartaric acid

115–216 calories 28.2–52 g 2.40–3.10 g 0.1 g 5.6 g 51.5–67.4 g 30–41 g 2.9–3.3 g 35–170 mg 54–160 mg 1.3–10.9 mg 24 mg 116–375 mg 15 I.U. 0.16 mg 0.07 mg 0.6–0.7 mg 0.7–3.0 mg 8–23.8 mg

Data derived from: Morton (1987); Khairunnuur et al. (2009); Khanzada et al. (2008)

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Mineral content of tamarind pulp, seed, kernel, and testa

Mineral mg100 g−1

Pulp

Seed

Kernel

Testa

Calcium Phosphorus Magnesium Potassium Sodium Copper Iron Zinc Nickel Manganese

81.0–466.0 86.0–190.0 72.0 62.0–570.0 3.0–76.7 21.8 1.3–10.9 1.1 0.5 –

9.3–786.0 68.4–165.0 17.5–118.3 272.8–610.0 19.2–28.8 1.6–19.0 6.5 2.8 – 0.90

1200.0 – 180.0 1020.0 210.0 – 80.0 100.0 – –

100.0 – 120.0 240.0 240.0 – 80.0 120.0 – –

Data derived and adapted from: Gunasena and Hughes (2000), Khanzada et al. (2008); Khairunnuur et al. (2009)

legumes (Table 22.4) (Bhattacharya et al., 1994; Khairunnuur et al., 2009). The seed is also rich in palmitic (14–20%), oleic (15–27%) and linoleic (36–49%) fatty acids (Andriamanantena et al., 1983; Khairunnuur et al., 2009). Tamarind fruits are known for their medicinal properties and have been used as herbal medicine in tamarind-producing countries (Jayaweera, 1981). Tamarind pulp is used to treat conditions such as intestinal ailments and skin infections which the pulp juice is used as a gargle to treat sore throats. Tamarind pulp also has uses as an anti-inflammatory (Rimbau et al., 1999) and has anti-bacterial, anti-fungal and molluscicidal properties as well (Imbabi et al., 1992). Tamarind pulp extract is used to cure malaria fever, alleviate sunstroke and as a digestive agent, and in the pharmaceutical industry, tamarind pulp is a common ingredient in cardiac and blood sugar reducing medicines. Tamarind seeds are considered a famine food, rich in protein. After removing the testa, which contains tannin and other anti-nutritional factors, they are consumed to prevent undesirable effects such as depression, constipation, and diarrhea (Rao and Srivastava, 1974; Khairunnuur et al., 2009). The seed was reported to have anti-diabetic effects (Rama Rao, 1975; Maiti et al., 2004) and to treat dysentery, ulcers and bladder stones (Rama Rao, 1975). Seeds have also shown anti-oxidant activity (Osawa et al., 1994; Luengthanaphol et al., 2004; Khairunnuur et al., 2009). Shimohiro (1995) reported that the quality of food was improved by adding the polysaccharide hydroxylates or xyloglucan oligosaccharides of tamarind seeds, which are known to have hypolipidemic effects. The tamarind seed coat was reported to be rich in procyanidin, which is known to have an anti-obesity effect (Koichi et al., 1997; Osumu et al., 1997), while a reduced-calorie food can be prepared using the cellulase hydrolysate of a tamarind polysaccharide (Whistler, 1991; Singer, 1994). Patil and Nadagoudar (1997) reported that polysaccharides derived from tamarind kernel powder were found to be suitable substitutes for corn steep liquor in the production of penicillin. The glucosyl transferase inhibitor, extracted from tamarind husks, was found to

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have an anti-dental caries effect (Tamura et al., 1996) and tamarind kernel powder is an ingredient of several cosmetic preparations.

22.2

Fruit growth and ripening

22.2.1 Fruit growth, development and maturation Tamarind fruit goes through growth, maturation and ripening stages before being ready for harvesting. Tamarind pulp shows a change in color during the different developmental stages; in the case of sweet tamarind, the pulp color changes from yellowish green at the half-ripe stage, and to reddish brown at the fully-ripe stage. Also, the pulp shrinks due to loss of moisture and becomes sticky, the immature pods have green and tender shells and the seeds are soft and whitish. As the pods mature, the shell develops into a brown color, the pulp turns sticky and brown or reddish-brown, and the seeds become harder and darker. When fully ripe, the shells become brittle and easily broken. Fruit ripening is characterized by an increase in the total acidity, sugars and alcohol insoluble materials of the pulp (Hernandez-Unzon and Lakshminarayana, 1982b). Total ash, phenolics and pectins increase in the peel but decrease in the pulp. 22.2.2 Respiration, ethylene production and ripening Tamarind fruit is non-climacteric (Yahia, 2004); it produces little or no ethylene and there is no large increase in CO2 production. The maximum CO2 production occurs four weeks after fruit set and gradually declines thereafter (HernandezUnzon and Lakshminarayana, 1982b). The pods reach the ripening stage in 8–10 months after flowering while the fruit is fully ripe when up to half of its original water content is dehydrated. Dehydration begins 203 days after fruit set and may continue to the 245th day (Chaturvedi, 1985). Fruit pods are harvested green for flavoring, and ripe for processing. The fruits of the sweet type are also harvested at two stages, half-ripe and fully-ripe.

22.3

Maturity and quality components and indices

A tamarind tree takes more than seven years to start fruiting and 10–12 years to produce economically appreciable amounts of fruits. Tamarind fruit growth is a typical sigmoid type (Hernandez-Unzon and Lakshminarayana, 1982a). The fully ripened fruits can remain on the tree until the next flowering period without showing any significant deterioration in quality (Rama Rao, 1975); however, they can be subjected to bird and insect attack. The physical separation of the peel from the pulp results from the loss in water content. It is recommended that fruit be harvested when the moisture content is less than 20% to facilitate the separation of the shell from the pulp. Pods from the same tree do not reach maturity at the same time, which makes selective harvesting a necessity.

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Preharvest factors affecting fruit quality

22.4.1 Rainfall The tamarind tree is well adapted to semiarid tropical conditions and grows well with an evenly distributed mean annual rainfall of 500–1500 mm (FAO, 1988; Jama et al., 1989; Hocking, 1993). In areas where annual rainfall is less than 500 mm, the trees are usually located near the water table or along water courses. The minimum annual rainfall which tamarind can tolerate is 250 mm and the maximum is up to 4000 mm in well-drained soil (Duke and Terrell, 1974). Tamarind grows well under wet conditions but does not flower (Allen and Allen, 1981; Morton, 1987) as dry weather is important for flowering and fruiting. It produces more fruit when subjected to a fairly long annual dry period (Allen and Allen, 1981; von Maydell, 1986) as a deep and extensive root system helps the tree to grow in very dry areas and withstand up to six months of drought (Coronel, 1991). This can be observed in the north and south dry zones of Sri Lanka, where there is a prolonged dry season of over 4–6 months. In dry zones the bearing ability of tamarind is comparatively less than those grown in intermediate rainfall areas as a sharp drop in rainfall and air temperature increases the curving of tamarind pods due to the low moisture content. Tamarind is usually evergreen but may shed its leaves in very dry conditions during the hot/dry season (Morton, 1987).

22.4.2 Temperature Tamarind grows within an annual temperature range of 33–37 °C and at a minimum temperature of 9.5–20 °C. Older trees can withstand temperatures as high as 47 °C and as low as −3 °C without serious injury (Verheij and Coronel, 1991). Tamarind may not survive in an altitude higher than 2000 m (Roti-Michelozzi, 1957; Dale and Greenway, 1961; Brenan, 1967; FAO, 1988; Jama et al., 1989), probably because of the low temperature rather than the altitude itself. It is very sensitive to fire and frost and requires protection when small (Troup, 1921; NAS, 1979) and is a light-demanding tree. The strong and pliant branches and deep and extensive root system make the tree wind-resistant (Coronel, 1986) and it is therefore known as the hurricane-resistant tree (NAS, 1979; von Maydell, 1986; von Carlowitz, 1986).

22.4.3 Soil The tamarind tree can grow in a wide range of soils and has no specific soil requirement (Chaturvedi, 1985; Sozolnoki, 1985; Galang, 1955). The tamarind tree has the ability to grow in poor soils because of its nitrogen fixing capability (Felker, 1981; Felker and Clark, 1980) and it can grow on rocky soil too. In India and Thailand, tamarind has been reported to grow on sodic and saline soils and on degraded land as well (Anon, 1991; Nemoto et al., 1987). Old tamarind trees have been found growing close to the sea (NAS, 1979; Pongskul et al., 1988;

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Anon, 1991). Pot experiment results showed that tamarind can grow in soil containing up to 45% exchangeable sodium (Dwivedi et al., 1996). El-Siddig et al. (2004a, 2004b) found a slight delay in emergence, but no effect on seedling growth, with up to 30 mM NaC1 salinity, while Gebauer et al. (2001) reported that tamarind seedlings can tolerate salinity up to 80 mM NaCl. It prefers soils that favor the development of a long tap root (Galang, 1955; Kelly and Cuny, 2000; Rao et al., 2000). Tamarind does not withstand low water-drainage soil (Relwani, 1993; Vogt 1995). The optimum pH is slightly acidic, 5.5–6.8 (FAO, 1988), though it also grows well in alkaline soils (Singh et al., 1997, quoted from Rao et al., 1999). It has been suggested that the association of tamarind with anthills and termite mounds may be due to a preference for slight lime content (Jansen, 1981) and aerated soil (Dalziel, 1937; Eggeling and Dale, 1951; Irvine, 1961; Allen and Allen, 1981).

22.5

Diseases and pests and their control

Tamarind fruits are subject to pests and diseases but are usually very tolerant to pathogens and insects, except in large plantations, because of their low moisture content and high content of acids and sugars. Also, the high phenolic content in the peel makes the fruit highly resistant to attacks from pathogens. Pulp separated from peel has good keeping quality but is subject to various molds in refrigerated storage. There are more than fifty insect pests that have been reported to attack tamarind in India (Joseph and Oommen, 1960; Senguttavan, 2000). These pests attack the tamarind tree at different growth stages; in the nursery as seedlings, and in the field once mature. They also attack different parts of the tree including stem, bark, branches, leaves, flowers and fruits. Fruits are attacked at different stages of ripening before and after harvesting. All these pests and diseases are of different economic importance, causing reduction in fruit production to different extents. In humid climates, fruit are readily attacked by beetles and fungi, and should therefore be harvested before they are fully ripe. The most serious pests of the tamarind are hard scale insects that suck the sap of the buds and flowers and accordingly reduce fruit production (Butani, 1978). The most important of these is the oriental yellow scale insect (Aonidiella orientalis). These scale insects can be controlled by removing the affected parts of the tree at an early stage while serious infestation can be controlled effectively using pesticides such as Diazinon or Carbosulphan at 0.1% solution (Butani, 1979). The mealy-bugs Nipaecoccus viridis and Planococcus lilacinus suck the sap of leaflets, causing defoliation, and may feed on young fruits; Chionaspis acuminata-atricolor and Aspidiotus spp suck the sap of twigs and branches. Mechanical control of mealy bugs can be achieved by removing the infected parts, but when serious infestations take place, chemicals such as Diazinon or Carbosulphan at 1% solution can be sprayed (Butani, 1979). Caterpillars, Thosea aperiens, Thalarsodes quadraria, Stauropus alternus, and Laspeyresia palamedes;

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the black citrus aphid, Toxoptera aurantii; the white fly, Acaudaleyrodes rachispora; thrips, Ramaswamia hiella subnudula, Scirtothrips dorsalis, and Haplothrips ceylonicus; and cow bugs, Oxyrhachis tarandus, Otinotus onerotus, and Laptoentrus obliquis, and other predators attack tamarind leaves or flowers. Other important pests that attack tamarind include fruit borers such as larvae of the cigarette beetle, Lasioderma serricorne, also of Virachola isocrates, Dichocrocis punctiferalis, Tribolium castaneum, Phycita orthoclina, Cryptophlebia (Argyroploca) illepide, Oecadarchis sp., Holocera pulverea, Assara albicostalis, Araecerus suturalis and Aephitobius laevigiatus. The fruit borer Aphomia gularis, the tamarind beetle Pachymerus (Coryoborus) gonogra and the tamarind seed borer Calandra (Sitophilus) linearis attack ripening pods before and after harvest. The rice weevil Sitophilus oryzae, rice moth Corcyra cepholonica, and the fig moth Ephestia cautella infest the fruits during storage. The borer Rhyzopertha dominica infests tamarind seeds during storage. Larvae of the groundnut bruchid beetle are serious pests that attack the fruit and seed in India while Bacterial leaf-spot is caused by Meliola tamarindi. Rots attacking the tree include saprot (Xylaria euglossa) brownish saprot (Polyporus calcuttensis), and white rot (Trametes floccosa). The tamarind tree is also susceptible to nematodes (e.g. Xiphinema citri and Longidorus elongates) that attack the roots of older trees. Other minor pests in India include lac insect and bagworms.

22.6

Postharvest handling factors affecting quality

22.6.1 Temperature management Storage for long periods under poor conditions, such as exposure to extremes of temperature and humidity, causes gradual changes in color from brown or yellowish-brown to black colors (FAO, 1989). Also, high temperatures cause pulp to lose moisture and become sticky and curved. 22.6.2 Water loss Drying the fruits in the sun for 3–4 days is used to remove excess moisture and prevent the growth of molds. However, severe dehydration associated with sharp water loss causes curving of the fruits which are considered of lower quality compared to straight pods (Yahia, 2004). 22.6.3 Physical damage The main problem with fresh sweet tamarind is the damage caused by packaging, which deteriorates the fruit quality and reduces the amount of consumable fruit. Also harvesting the fruits, which is usually done by shaking the branches, might result in fruit damage. A better quality of fruit could be obtained by using scissors to harvest the fruits, especially in the case of the sweet tamarind type.

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Postharvest handling practices

22.7.1 Harvest operations Pod yield stabilizes at about 15 years and continues for up to 50 or 60 years. Tamarind fruits are mature and ready for harvesting when a hollow and loose sound is produced by finger pressing, as the pulp shrinks with maturity and the shell becomes brittle. Also, the change in testa color might indicate the maturity of the fruit. However, it is not always easy to determine whether the fruits are ready for harvesting, as the testa color only changes slowly as the pods mature. Individual fruits on the same tree also mature at different times, making selective harvesting necessary. Pods are harvested at different stages of ripeness, according to how they are going to be used. Immature green fruits are usually harvested earlier for flavoring. In most countries, the sour tamarind ripe fruits are usually gathered by shaking the branches and collecting the fruits that have fallen; the remainder of the fruit is left to fall naturally when ripe. Sweet tamarind fruits tend to gain higher market prices, and therefore are carefully picked by hand. To avoid damaging the pods and to increase the marketability of both sweet and sour types, harvesting by clipping should be practiced (Coronel, 1991). Pickers should not knock the fruits off the tree with poles, as this will damage developing flowers and leaves. Generally, the fruits are left to ripen on the tree before harvesting, so that the moisture content is reduced to about 20%. If unharvested, the pods may remain hanging on the tree for almost one year after flowering and sometimes until the next flowering period (Chaturvedi, 1985), and eventually will fall naturally. Fruits for immediate processing are often harvested by pulling the pod away from the stalk, which is left with the long, longitudinal fibers attached. Beetles and fungi readily attack ripe fruit in humid climates, and therefore they should be harvested before they are fully ripe.

22.7.2 Packinghouse practices One of the most important operations in a packing line is sorting for maturity, color, shape, size, and defects. The efficiency and effectiveness of sorting govern the quality standard of the packing lines and product (Office of Thai Agricultural Commodity and Food Standard, 2003), which in turn determines the marketability of the product. Manual sorting continues to be the most prevalent method used, although it is costly in terms of labor and time. Also, the lack of trained labor is one of the reasons that manual sorting may become inefficient and cause damage. One of the most practical and successful techniques for nondestructive quality evaluation and sorting of agricultural products is the electro-optical technique, which judges the optical properties of the product (Chen, 1996). This technique, which can be used to detect color uniformity, shape, size, external defects, foreign materials, and disease, has been used for postharvest grading for a wide variety of agricultural products including tamarind. Jarimopas et al. (2008) proposed packaging in a sleeve design, 15 cm in diameter by 20 cm in height, containing a mixture of 5 mm foam balls and sweet tamarind inserted vertically. This packaging

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imparts 15 to 16% of the damage of conventional packaging and costs half the price. 22.7.3 Control of ripening and senescence Tamarind fruit, as a non-climacteric (Yahia, 2004), will not ripen any further after harvest. The flavor, juice, sugars and some other contents remain unchanged. No information is readily available on techniques for controlling tamarind ripening. 22.7.4 Recommended storage and shipping conditions The high soluble solids content to titratable acidity (SSC : TA) and the low water content of tamarind fruit contributes to its long storage-life. Tamarind can be stored with the shell, or as a separated dry pulp, and tightly packaged pods can be stored at 20 °C for several weeks. The pulp of mature tamarind is commonly compressed and packed in palm leaf mats or plastic bags and stored at 20 °C for a significant period when processed into paste. It can be frozen and stored for one year, or refrigerated for up to six months. Under dry conditions the pulp remains good for about one year, after which it becomes almost black. In humid weather, especially, the pulp becomes soft and sticky as pectolytic degradation takes place and moisture is absorbed (Lewis and Neelakantan, 1964a; Anon, 1976). During storage, the dry, dark-brown pulp becomes soft, sticky, and almost black. The pulp can be stored for a longer period after drying or steaming. According to the research findings of CFTRI (Central Food Technological Research Institute, Mysore, India), the pulp could be preserved well for 6–8 months, without any treatment, if it is packed in airtight containers and stored in a cool dry place (Shankaracharya, 1997). The tamarind kernel powder is liable to deterioration during long storage, particularly in a moist environment; thus a dry place in moisture proof containers is preferred, after suitable fumigation. The powder may be mixed with 0.5% of sodium bisulphite before packing to prevent enzymic deterioration (Anon, 1976).

22.8

Processing

22.8.1 Processing of tamarind pulp Fresh-cut processing is not an industrial practice: it is usually carried out on a smaller scale when the fruits are intended to be eaten immediately. Fresh-cut tamarind is processed to make tamarind balls mixed with sugar after removing the shells, seeds and fibers. In Asia, the immature green pods are often eaten dipped in salt as a snack. In the Bahamas the unripe pods are roasted in coal, peeled back and the sizzling pulp is dipped in wood ash and eaten. In processing factories, tamarind pulp is separated from the fiber and seed, then mashed with salt before being packed into bags and if tamarind is intended to be stored for a long period, drying or freezing is required. To preserve tamarind,

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the fruit are shelled, layered with sugar in boxes or pressed into tight balls and covered with cloth and kept in a cool and dry place. For shipment, tamarinds may be shelled, layered with sugar in barrels and covered with boiling syrup. East Indians shell the fruit and sprinkle them lightly with salt as a preservative. In Java, the salted pulp is rolled into balls, steamed and sun-dried, then exposed to dew for a week before being packed in stone jars. In India, the pulp, with or without seeds and fibers, may be mixed with salt (10%), pounded into blocks, wrapped in palm-leaf matting, and packed in burlap sacks for marketing. To store for long periods, the blocks of pulp may be first steamed or sun-dried for several days. During pre-processing, fresh tamarind fruit is subjected to sun-drying or small scale dehydrators are sometimes used. The dry fruit is cracked, the pulp and fibers are separated and the seeds are removed. Pods can be store for several weeks at 20 °C. Also, pulps can be stored for 4–6 months at 10 °C by packing in high density polythene. Mixing with salt can extend the storage period to one year. Tamarind juice is usually prepared by boiling tamarind pulp in water and filtering the juice to remove the pulp before pouring into bottles and sealing. Tamarind concentrate is easily dispersible in water, and can be used for many purposes, such as in ketchups, sauces, soft drinks, dairy products and as a souring agent. It is prepared by soaking the tamarind pulp in water and boiling, separating fine and pulpy matter using a filter, then pressing the residue and mixing this with the extract. The filtered extract is concentrated by evaporating it in a vaccum, filling containers, cooling and sealing, and storing in airtight plastic or glass bottles or cans, in the dark, for over a year. Tamarind is often further processed into drinks and sweets or packaged into more convenient forms for export. In some parts of India, it is made into a jelly by mixing with water and sieving. It is then compressed into moulds and can be cut like cheese when required. 22.8.2 Processing of tamarind seed The hard, brown outer testa has to be completely removed from the kernel to prevent it from causing undesirable effects such as depression, constipation, and gastrointestinal inflammation, so the testa is separated from the kernels by either roasting or soaking the seed in water. Washing the seeds helps to remove the adhering pulp and to float away partially hollow infected seeds. When roasting, the temperature and duration of heating should be controlled to avoid the development of any undesirable characteristics in the isolated gum (Anon, 1976). The parched seed is then fed into a grain cleaner to remove the testa and dirt (Whistler and Barkalow, 1993). Very white tamarind kernel powder can be obtained by hydrating the seeds at room temperature for 24 hours, drying in the shade for 24 hours and then sand roasting at 125–175 °C for 3–8 minutes. Different processing methods to remove the testa were reported by Kumar and Bhattacharya (2008).

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Conclusions

The intrinsic value of raw tamarind can be further enhanced through value addition activities and there is a good market for these processed products both in the domestic as well as in international markets.

22.10

References

Allen ON and Allen EK (1981), The Leguminosae: A Source Book of Characteristics, Uses and Nodulation, Madison, WS, University of Wisconsin Press. Anon (1955), Tamarind seed has many uses. Forest Research Institute. Dehra Dun, India. Indian Farming, 5, 21–24. Anon (1976), Tamarindus. In The Wealth of India (Raw materials series), Vol X: 114–120. Council of Scientific and Industrial Research, New Delhi, India. Bhattacharya S (1990), ‘A study on the processing and utilization of tamarind (Tamarindus indica) kernel for food uses’, PhD thesis, Post Harvest Technology Centre, Indian Institute of Technology, Kharagpur, India. Bhattacharya, S. (1997). ‘Utilisation of tamarind seed kernel in food industry’. In: Proceedings of National Symposium on Tamarindus indica L., Tirupathi, India, pp 162–168. Bhattacharya S, Bal S, Mukherjee RK, and Bhattacharya S (1994), Functional and nutritional properties of tamarind (Tamarindus indica) kernel protein, Food Chemistry, 49, 1–9. Bleach MF, Guillemin F, Baure L and Hartemann P (1991), Preliminary study of antimicrobial activity of traditional plants against E. coli. Zentralblatt hygiene und umweltmedizin, 192(1), 45–56 (English summary). Bueso CE (1980), ‘Soursop, tamarind and chironja’. In: Nagy S and Shaw PE (eds) Tropical and Subtropical Fruits, AVI Pub, Westport CT, pp. 375–406. Butani DK (1978), Insect pests of tamarind and their control, Pesticides, 12(11), 34–41. Butani DK (1979), Insects of Fruits, Periodical Export Agency, Vivek Vihar, Delhi, p. 415. Chaturvedi AN (1985), Firewood farming on the degraded lands of the Gangeticplain, U. P. Forest Bulletin, No.50. Lucknow, India Government of India Press 1, 286. Chen J, Ji YZ and Shujuan HX (1988), Effect of tamarind seed polysaccharide on the storage of pineapple fruits, Zhiwu Shenglixre Tongxun, 4, 30–32. Coates-Palgrave K (1988), Trees of Southern Africa, 10. Tamarindus indica L. C. S. Striuk Publishers, Cape Town, pp. 278–279. El-Siddig K, Gunasena HPM, Prasad BA, Pushpakumara DKNG, Ramana KVR, et al. (2006), Tamarind (Tamarindus indica L.), Southampton Centre for Underutilised Crops, W. Sussex, England. FAO (1988). Fruit Bearing Trees. Technical notes. FAO-SIDA Forestry Paper, 34, 165–167. FAO (1989), Prevention of Post-harvest Losses: Fruits, Vegetables and Root Crops, FAO Training Series No 17/2, Rome. Hasan SK and Ijaz S (1972), Tamarind – A review, Sci Indus Pakistan, 9, 131–137. Hernadez-Unzon HY and Laksminarayana S (1982a), Developmental physiology of tamarind fruit (Tamarindus indica L.), HortScience, 17, 938–940. Hernadez-Unzon HY and Laksminarayana S (1982b), Biochemical changes during development and ripening of tamarind fruit (Tamarindus indica L.), HortScience, 17, 940–942. Hort A (1916), Theophrastus; Enquiry into Plants, Heinemann, London. Imbabi ES and Abu-Al-Futuh IM (1992), Investigation of the molluscicidal activity of Tamarindus indica L., International Journal of Pharmacology, 30(2), 157–160.

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Ishola M, Agbaji B and Agbaji AS (1990), A chemical study of Tamarindus indica (Tsamiya) fruits grown in Nigeria, J Sci Food Agric, 51, 141–143. Jambulingam R and Fernandes ECM (1986), Multipurpose trees and shrubs in Tamilnadu state (India), Agroforestry Systems, 4, 17–32. Jarimopas B, Sirisomboon P, Sothornvit R and Terdwongworakul A (2008), ‘The development of engineering technology to improve the production of tropical fresh produce in the developing countries’. In: Pletney, Vivian N. (ed.), Focus on Food Engineering Research and Development, Nova Science Publishers, Inc., New York. Jayaweera DMA (1981), ‘Medicinal plants (indigenous and exotic) used in Ceylon’, Part 111. Flacourtiaceae-Lytharaceae. A publication of the National Science Council of Sri Lanka, pp. 244–246. Joseph KV and Oommen P (1960), Notes on some insect pests infesting dry tamarind fruits in Kerala State, Indian Journal of Entomology, 22(3), 172–180. Khairunnuur FA, Zulkhairi A, Azrina A, Moklas MAM, Khairullizam S, et al. (2009), Nutritional composition, in vitro antioxidant activity and Artemia salina L. lethality of pulp and seed of Tamarindus indica L. extracts, Mal J Nutr, 15(1), 65–75. Khanzada SK, Shaikh W, Sofia S, Kazi TG, Usmanghani K, et al. (2008), Chemical constituents of Tamarindus indica L. medicinal plant in Sindh, Pak J Bot, 40(6), 2553–2559. Koichi N, Masaaki T and Yukiyoshi T (1997), Antiobesity agent containing procyanidin as the active agent, Chemical Abstract, 127, 126638. Kuwano K, Suzuki J, Oowadani K, Shiratawa M (1995), Xyloglucan for inhibition of fat increase, Japanese Patent, 07, 147, 934. Lefebvre JC (1971), Tamarind – A Review, Fruits, 26, 687–695. Lewis YS and Neelakantan S (1964), The real nature of tamarind anthoxanthin, Curr Sci, 15, 460. Luengthanaphol S, Mongkholkhajornsilp D, Douglas S, Douglas PL, Pengsopa L and Pongamphai S (2004), Extraction of antioxidants from sweet Thai tamarind seed coatpreliminary experiments, J Food Engineering 63, 247–252. Maiti R, Jana D, Das UK and Ghosh D (2004), Antidiabetic effect of aqueous extract of seed of Tamarindus indica in streptozotocin-induced diabetic rats, J Ethnopharmacol, 92(1), 85–91. Marangoni A, Ali I, Kermasha S (1988), Composition and properties of seeds of the true legume Tamarindus indica, J Food Sci, 53, 1452–1455. Morton J (1987), Fruits of Warm Climates, Miami, FL, pp. 115–121. Morton JF (1958), The tamarind, its food, medicinal and industrial uses, Proc Fla State Hort Soc, 79, 355–366. Office of Thai Agricultural Commodity and Food Standard (2003), Thai Agricultural Commodity and Food Standard, No. TACFS 5-2003, Mango. Ministry of Agriculture, pp. 6. Osawa T, Tsuda T, Watanabe M, Ohshima K and Yamamoto A (1994), Antioxidative components isolated from the seeds of tamarind (Tamarindus indica L.), J Agric Food Chem, 42, 2671–2674. Osumu B, Junko S, Mayumi S and Kazuhiko Y (1997), Lipid increase inhibitors containing xyloglucan, Chemical Abstract, 127, 247372. Patino VM (1969), ‘Plantes cultivadas y animales domesticos en America equinoccial. Tomo IV. Plantes introducidas Imprenta Departamental’, Cali, Colombia, 233–235. Rama Rao (1975), Flowering Plants of Travencore, Dehra Dun, India: Bishen Singh Mahendrapal Singh, 484 p. Rao PS (1948), Tamarind seed (jellose pectin) and its jellying properties, J Sci Ind Res, 68, 89–90. Reddy SG, Rao JMS, Achyutaramayya D, Azeemoddin G and Rao TSD (1979), Extraction, characteristics and fatty acid composition of tamarind kernel oil, J Oil Technol Assoc India, 11, 91–93.

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Rimbau V, Cerdan C, Vila R and Iglesias J (1999), Antiinflammatory activity of some extracts from plants used in the traditional medicine of North-African countries, Phytotherapy Research, 13(2), 128–132. Senguttuvan T (2000), Insect pest associated with three semi arid fruits under agroforestry, Insect Environment, 6(2), 78. Shankaracharya NB (1998), ‘Chemical and Technological Aspects of Tamarindus Indica Fruit.’, Proc. Nat. Sym. on Tamarindus indica L, Tirupathi (A.P.), organized by Forest Dept. of A.P., India, 27–28 June, 1997, pp. 226–30. Tsuda T, Fukaya Y, Ohshimo K, Yamamoto A, Kawakishi S and Osawa T (1995a), Antioxidative activity of tamarind extract prepared from the seed coat (Japanese), J Japanese Food Sci Technol (Nippon-Shokuhin-Kogyo- Gakkaishi), 42, 430–435. Tsuda T, Watanabe M, Ohshima K, Yamamoto A, Kawakishi S and Osawa T (1994), Antioxidative components isolated from the seeds of tamarind (Tamarindus indica L.), J Agric Food Chem, 42, 2671–2674. von Maydell HJ (1986), Trees and Shrubs of Sahel. Their Characteristics and Uses, Deutsche Gesellschaft für Technische Zusammenarbeit, Eschborn, Germany. Yaacob O and Subhadrabhandu S (1995), The Production of Economic Fruits in South East Asia, Oxford University Press, 133–142. Yahia EM (2004), ‘Date’, in: U.S. Dept. Agric. Agric. Handbook #66: (http://www.ba.ars. usda.gov/hb66/index.html).

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(a)

(b)

Plate XXXVIII

(Chapter 22) (a) Packaged Tamarind from Mexico; (b) Tamarind in a local market in Mexico.

(a)

(b)

Plate XXXIX

(Chapter 22) (a) Tamarind tree; (b) Tamarind pods.

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23 Wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry) and related species Z.-H Shü, Meiho University, Taiwan, C.-C. Shiesh and H.-L. Lin, National Chung-hsing University, Taiwan

Abstract: The wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry), belongs to Myrtaceae and has been commercially planted in many countries, such as Taiwan, Thailand, Indonesia and Malaysia. There are two major parts in this chapter: the first part introduces the origin, biology and preharvest cultural practices; the second part deals with postharvest handling and storage. The fruit of the wax apple is fragile, non-climacteric with a short shelf life. Water loss is a big problem for wax apple storage so to keep the moisture and decrease the perishing process, modified atmosphere packaging with temperatures between 10 to 12 °C is recommended for the storage of wax apple fruits. Key words: Syzygium samarangense, wax apple, postharvest, handling, storage.

23.1

Introduction

23.1.1

Origin, botany, morphology and structure

Origin and worldwide importance The wax apple (Syzygium samarangense (Blume) Merr. and L.M. Perry; other names are Java apple, wax jambu and water apple), which belongs to the Myrtaceae, is native to the Malaysian Archipelago and to the Andaman and Nicobar islands where the trees grow in coastal rainforests (Morton, 1987). Other species with similar fruits for fresh consumption that are commercially important are the water apple Syzygium aqueum, the rose apple Syzygium jambos, and the Malay apple Syzygium malaccense (Nakasone and Pall, 1988). All these species have spread throughout the tropical areas of the world. The fruit of Syzygium jambos, the rose apple, is relatively round to oval shaped and has the scent of a rose (Morton, 1987).

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The flower and fruit of Syzygium malaccense, the Malay apple, are the most beautiful of those of the four species. The fruit of the water apple (Syzygium aqueum) is very similar to that of the wax apple (Syzygium samarangense), but it is smaller and insipid. The fruit of the wax apple is larger and sweeter (Shü and Paull, 2008; see Plate XL in the colour section between pages 238 and 239) and since it is the most delicious, it has been commercially planted in many countries, such as Taiwan, Thailand, Indonesia and Malaysia (Shü et al., 2008, 2009). Most research focuses on Syzygium samarangense since it is the only species commercially planted on a large scale among the four important freshly consumed species. The introduction of the biology, production and postharvest technology of the present article are thus based primarily on Syzygium samarangense. Biology The tree of the wax apple can grow to a height of 5–15 m depending on environmental conditions (Young, 1951), with flowers appearing in March in south Taiwan and fruits ripening in May under natural conditions. Fruits vary greatly in size, shape and skin color. The fruit size can be as small as about 4.3 cm long and 4.7 cm wide to more than 5.2 cm long and 5 cm wide (bell-shaped) or 7 cm long and 4 cm wide (elongated). Fruit mass ranges from 28 g to 100 g to the jumbo sized of more than 200 g per fruit. Fruit shape ranges from round to bell-shaped, oval or elongated and skin color diverges from white to pale green to dark green, pink to red to deep red. The fruit of wax apple are sweet when eaten fresh or cooked. Therefore they are better for eating than the Malay apple and other species in the same genus. A small percentage of the fruit is used for sauces, jams and jellies. Wax apple trees are tropical and cannot tolerate temperatures below 7 °C, preferring temperatures above 18 °C (Kuo, 1995; Huang et al., 2005). Fruits of wax apples prefer warm temperatures for normal growth and development as low temperatures impede fruit growth and red color development, while high temperatures accelerate fruit growth and ripening but inhibit red color development. The flesh is juicy, fragrant, crisp and sweet. Water content of the fruit is 92.9%, protein 0.35%, carbohydrate 6%, crude fiber 0.46% and ash (minerals) 0.21% (Shü and Paull, 2008). Flowering and fruiting ‘Pink’ is the leading cultivar, representing 85% of the planted areas in Taiwan (Shü et al., 2007; Wang, 2006). Flowers appear in March in south Taiwan and fruits ripen in May under natural conditions (Young, 1951). However, ‘Pink’ blooms and sets fruit almost year-round after flower forcing (Shü et al., 1996; Wang, 1991). As a result, fruits at different growing stages could be found in different orchards, on different trees and even on the same tree. The wax apple is a heavy producer on well-fertilized good soils and can produce more than 200 clusters per tree, with 4–5 fruits in each cluster when mature (see Plate XLI in the colour section). Average fruit weight of the ‘Pink’ variety is about 100 g, however a single fruit of ‘Big Fruit’, mutants of ‘Pink’, weighs from 150 g to more than 200 g (Chiu, 2003).

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Climates and soils Wax apples prefer full sunlight for normal growing and fruiting, although they tolerate shade (Wang, 1991), and the best growing temperature for wax apple is around 25 °C. Temperatures under 8 °C may cause severe damage, both on the fruits and leaves. The wax apple can be grown on very wide range of soils from sandy to clayey and from acid to alkaline. However, for best fruit quality, fertile, wet and slight alkaline soils are preferred. Cultivars The wax apple, being planted commercially, has many cultivars. ‘Pink’ has been the leading cultivar in Taiwan, but other important cultivars in Taiwan are ‘Black King Kong’, ‘Light Red’, ‘Dark Red’, ‘Green’, ‘White’, and ‘Malacca’ (Shü et al., 2007). The major wax apple cultivars in Thailand are ‘Ma Mieaw’, ‘Nam Dokmai’, ‘Gam Hmam’, ‘Kaeg Dam’ and ‘Thub Thim Chan’. There are four cultivars grown in Malaysia, namely, ‘Pale Green’, ‘Dark Red’, ‘Light Red’ and ‘Green’ (Shü et al., 2008). Indonesia has the most abundant varieties, where wax apples are mostly grown as backyard trees covering an area of a couple of villages in a district, also known as ‘centers of production’. The largest centers of production are in Java and Madura Island. The most popular local cultivars are ‘Citra’, ‘Cincalo’, ‘Lilin Merah’, ‘Camplong’, ‘Kaget’, and ‘Semarang Prada’ (Shü et al., 2008). Propagation The wax apple can be propagated using seeding, cutting, grafting or air-layering (the most commonly used method). Most often air-layering is practiced during warm and wet seasons when wax apple trees grow rapidly. The bark, together with the vascular cambium, on two- to three-year-old healthy branches are removed (girdled) first for air-layering practice. The remaining wood (secondary xylem) are covered with wetted sphagnum moss and then covered with a plastic film to keep the moisture. It takes about one month to initiate new roots from the abaxial sides of the barks where girdles were taken. The rooted branches are removed from the mother plants when roots are well developed and brown in color (Wang, 2006). Planting The wax apple trees can be planted from 5 m × 5 m to 7 m × 8 m depending on different management systems. Avoid overcrowding of the trees and branches since this may cause self-shading, extra pest control practices, and branch die-back which reduces yield and produces low-quality fruits (Wang, 2006). Training and pruning Canopy size is important for wax apple tree management and fruit quality. Usually good quality wax apple fruits are located at the lower parts of the canopy, either

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on the big branches or on the truck. Adequate canopy size control is extremely important for keeping fruit quality high since commercial wax apple trees bear fruits two to three times per year (Wang, 2006). Suitable training to keep the tree at medium size (averaging about 3 m high) is important since it saves labor on pruning, bagging, spraying, thinning fruits or harvesting. Besides, shorter trees are more resistant to strong wind damage. For wax apple tree production there are mainly three training systems, namely bald-cut, semi-bald cut and evergreen, with heavy, medium and light pruning practices, respectively, used in Taiwan (Fig. 23.1a, b; Shü et al. 2007; Wang, 2006).

Fig. 23.1

Evergreen (a) and bald-cut (b) training systems (courtesy of Chi-cho Huang).

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Fertilization Adequate fertilization is very important for high yield and quality fruits. The amount of fertilizer to apply varies depending on tree age, size, vigor, yield, soil property and growing stages. Although experience is important, soil and leaf diagnosis are recommended for adequate fertilization (Wang, 2006). Off-season production 1. Advantages Normal flowering and harvesting periods for wax apples are from March to July and from May to September in Taiwan. Both the quality and price of the fruits produced during the normal harvesting periods are not acceptable to many consumers and farmers. Off-season production for wax apples means shifting the harvesting from summer to winter. Fruit quality and price are much more favorable for fruits produced in winter than in summer because winter fruits, due to a longer growing season and fewer pests, are bigger, crispier, sweeter, juicier, seedless and thicker in flesh (Wang, 2006). Nitrogen control, water logging, root pruning, trunk injury and canopy shading are commonly used methods of off-season production. Fruit quality improvement The quality of the wax apple fruit is closely related to the season and growing region. For example, the fruit produced in summer has greater weight and volume, while the fruit produced in winter has more total soluble solids concentration and hardiness (Chen, 2006; Lo, 2008). Wax apple fruits from Linbian have the darkest red color in summer, while fruits from the Liugui and Chaozhou areas in Taiwan have the darkest red color in winter (Chen, 2006). Position on the tree also influences quality of wax apple fruits, with the fruit on the lower trunk being heaver while the upper inner fruits have the reddest color (Shü, 1999). Anthocyanin and total soluble solids concentrations (SSC) were greater in the 20 °C treated discs when a skin disc in vitro culture system was used to study the effects of temperatures on fruit quality of wax apple (Pan and Shü, 2007). Among the 18 combinations, light/20 °C/6% sucrose gave the highest SSC and anthocyanin content, while dark/20 °C/6% sucrose produced the largest diameter (Shü et al., 2001). Sucrose at various concentrations enhanced the red color of the cultured fruit discs (Liaw et al., 1999). Fruit discs from the rapid growth stage to the red stage, i.e. from 4 to 8 weeks after anthesis, had greater anthocyanin induction potential than the other stages when cultured with 6% sucrose (Chang et al., 2003). Wax apple fruits treated with N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU, a synthetic cytokinin) had greater fruit volume, weight and flesh thickness than that of the control (Shü and Yeh, 1998). Manganese sulfate sprays at 1.5% or 2.0% four times at an interval of 14 days for three weeks after petal fall increased anthocyanin concentration (Lee, 2003).

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23.1.2 Worldwide importance The wax apple has been planted as a backyard tree or only consumed either locally or domestically in some areas, but planted on a commercial scale for decades in others. In recent years wax apple fruits have been treated as an international trading commodity, and have been shipped to China, Hong Kong, Singapore, Canada and other foreign markets from Taiwan. Thailand has been sending wax apple fruits to China as well. However, before the perishable problems are solved, there is little potential for wax apple fruits to become a large international trading commodity. 23.1.3 Culinary uses, nutritional value and health benefits Wax apple fruits are primarily consumed fresh. The nutritional value of the fruit is as follows (for every 100 g): calorie 34 Kcal, water 90.6 g, crude protein 0.5 g, crude fat 0.2 g, carbohydrate 8.6 g, crude fiber 0.6 g, dietary fiber 1.0 g, ash 0.2 g, vitamin B1 0.02 mg, vitamin B2 0.03 mg, vitamin B6 0.03 mg, niacin 0.03 mg, vitamin C 6.0 mg, sodium 25 mg, potassium 340 mg, calcium 28 mg, magnesium 13 mg, phosphorus 35 mg, iron 1.5 mg, zinc 0.2 mg (http://www.doh.gov.tw/Food Analysis/). The genus of Syzygium comprises more than 500 species occurring in the tropics and subtropics. Some of the species, such as S. aromaticum, S. cordatum, S. cumini, S. jambolanum, S. jambos and S. samarangense, have been reported to have medical usage, such as diabetes or glucose tolerance impairment (Kelkar and Kaklij, 1996; Nagaraju and Rao, 1989, 1997; Prince et al., 1998; Rao and Rao, 2001; Stanely Mainzen et al., 1998; Teixeira et al., 1997; Thammanna et al., 1994; Toda et al., 2000), as well as inflammation (Chaudhuri et al., 1990; Kim et al., 1998; Muruganandan et al., 2001). They have also been used as anticonvulsant and sedative (De Lima et al., 1998), as antihypertensive (Bhargava et al., 1968), antimicrobial (Djadjo Djipa et al., 2000), against herpes virus (Kurokawa et al., 1998) and as an inhibitor of histamine release (Kim et al., 1998). An anti-inflammatory activity from Syzygium jambos leaf extracts was reported by Slowing et al. (1994a, b). The bark, leaves and roots of Syzygium cordatum are used for tuberculosis, diarrhea, stomach and respiratory complaints management in South Africa (Van Wyk et al., 1997). Syzygium alternifolium seed powder can be used for fevers and skin diseases (Thammanna et al., 1990). The antioxidant property of Syzygium cumini is well known (Prince et al., 1998) and juices of the fruits are stomachic, astringent and diuretic (Nadkarni and Nadkarni, 1976). Syzygium jambos extract has remarkable analgesic effects (Ávila-Peńa, 2007). Four cytotoxic and eight antioxidant compounds identified in the fruits (Simirgiotis et al., 2008) and four flavonoids, showing inhibitory potency on peripheral blood mononuclear cells (PBMC), were isolated from the leaves of Syzygium samarangense (Kuo et al., 2004).

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23.2

Postharvest biology and technology of tropical and subtropical fruits

Fruit development and postharvest physiology

23.2.1 Fruit growth, development and maturation The kinetics of fruit growth of the wax apple indicates single sigmoid curves. The firmness of the fruit decreases at late stages of fruit development while fruit color turns red gradually as the anthocyanin content increases. The chlorophyll concentration increases during early fruit development, then decreases and maintains a constant level until harvest, while total soluble solids of the fruit increase with fruit development. The concentrations of free amino acids and soluble protein of wax apple fruits are at their highest 20 days after full bloom, then diminished abruptly (Shü et al., 1998). 23.2.2 Respiration, ethylene production and ripening Both the fruits of wax apple (Akamine and Gao, 1979; Chiang, 2005; Hwang, 1998) and Malay apple (Basanta, 1998) are non-climacteric fruits. The respiration rate for the wax apple is steady at 65–75 ml CO2.kg−1.hr−1 and without a respiration peak at 25 °C (Liao et al., 1983). The rate reduces or increases when temperatures are reduced or increased, respectively; for example, respiration rate reduces to 15–25 ml CO2 kg−1.hr−1 at 5 °C and in summer increases to 1.5 times that of the respiration rate in winter (Horng, 1988). Wax apple fruits produce low concentration of ethylene (<0.5 μkg−1.hr−1) and increasing external ethylene does not seem to affect fruit physiology (Hwang, 1998). No ethylene was detected for the Malay apple stored at four different temperatures (Basanta, 1998). The shelf life of wax apple fruits is shorter in summer than in winter, and summer fruits are prone to chilling injury (Hwang, 1998).

23.3

Maturity, quality components and indices

Wax apple fruits are harvested when the fruit reaches its full size and skin color breaks from creamy white to a little transparent white or green to pale green or pink to red or red to dark red, depending on the particular cultivars and cultivation techniques. When wax apple fruits are ready to harvest, the calyxes at the blossomend change angle from erected to flat (parallel to the blossom-end surface of the fruit) or even bend down toward the blossom-end pits. This is another index for harvesting some of the wax apple varieties, especially ‘Pink’.

23.4

Physiological disorders

23.4.1 Chilling injury Chilling injuries (CI), occurring either in the field, after harvest or during cold storage is another serious problem for wax apple production, storage and handling in Taiwan since the wax apple is a tropical species. Fruits get CI when stored at either 0 °C for 3 days, 5 °C for 6 days or 10 °C for 11 days (Table 23.1).

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Table 23.1 Changes in a* value of skin color of wax apple after rewarming at 25 °C for three days following storage Storage temperature (°C)

0 5 10 15 20 25

a* value of skin color 3z

6

9

12

15

16.5 ± 5.5y 22.9 ± 2.6 24.9 ± 2.0 22.4 ± 3.1 20.5 ± 5.8 22.5 ± 2.2

8.9 ± 5.3 16.6 ± 4.4 19.6 ± 2.1 20.2 ± 3.3 18.8 ± 2.9 19.5 ± 5.1

6.8 ± 2.3 14.5 ± 4.3 18.1 ± 2.8 18.1 ± 3.0 22.4 ± 3.2 19.4 ± 4.0

5.4 ± 2.2 13.2 ± 3.2 20.2 ± 4.2 19.3 ± 2.6 20.9 ± 3.4 21.2 ± 3.1

7.8 ± 2.0 16.4 ± 3.3 20.9 ± 4.1 20.7 ± 2.4 –x

–

z storage

time – days. ± SE. x Fruits decayed. y Means

Temperatures higher than 10 °C are thus recommended for cold storage of wax apple fruits. Although wax apple fruits are sensitive to CI, different varieties have different susceptibility, and fruits of a particular variety may respond to CI differently at different seasons (Horng, 1988). Fruits produced in summer have less sugars, higher respiration rates and are more susceptible to CI. Either raising relative humidity during storage or using modified atmospheres packaging (MAP) (Table 23.2) reduces CI of wax apple fruits (Horng, 1988). The fruit of wax apple produces large amounts of ethylene when raising storage temperature from lower than 10 °C to above 10 °C. Figure 23.2 shows ethylene production of wax apple fruits during re-warming for 32 hours at 25 °C following storage at 1 °C, 15 °C and 20 °C for 7 days (Chiang, 2005). Very low amounts of

Fig. 23.2 Changes in ethylene production of wax apple fruits during re-warming at 25 °C for 32 hours following storage at 1 °C, 15 °C and 20 °C for seven days (Chiang, 2005).

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ethylene were released for the 15 °C and 20 °C storage treatments. In contrast, ethylene production reached its maximum value of around 7 μl kg−1.hr−1 15 hours after temperature had been raised to 25 °C for the 1 °C storage treatment. Concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) also increased at the same time, however, activities of ACC oxidase decreased following the decrease of storage temperatures and increase of storage time. The mass production of ethylene may have some connection to the discoloration and softening of the skin (Horng, 1988). Needle-sized pitting on fruit skin is the first symptom of CI. These pittings were turned into scald-like discoloration areas on the skin later on (decrease in color and color difference value a* are shown in Table 23.1). The injured areas show rotting and off-flavors when fruits are returned back to ambient temperatures. Several methods to reduce CI are available (Huang and Wang, 2003):

• • • • • • •

Reschedule the flowering and fruiting times to avoid low temperature periods. Balance fruit and leaf ratios since excessive fruit loading decreases tree vigor. Prune adequately so enough sunlight reaches the fruit. Increase tree temperatures by spraying underground water which is warmer than the water above ground. Apply plant growth regulators, such as 50 ppm GA3, 10 ppm GA4+7, or 6-BA10 ppm, at early fruit development stages. Apply 10–15 ppm α-SNA (α-Naphthaleneacetic acid potassium salt) before low temperature comes. Use suitable storage temperatures and/or MAP.

Best quality fruits can be obtained using preharvest in combination with postharvest measures.

23.4.2

Other physiological disorders (to which the commodity is susceptible)

Cracking Fruit cracking is a serious problem for ‘Pink’ wax apple production in Taiwan, as devastating cracking can occur when fruits are mature. Factors affecting the incidence of cracking are season, fruit position on the tree, bagging materials and soil moisture contents (Lai, 2005). The cracking incidence in winter averages 19%, however, the percentage could rise up to 68% in May and June. Lo (2008) has similar results with higher cracking rates for summer crops and lower cracking rates for winter crops. The crack could be 2 to 3 cm long and 0.1 to 0.3 cm deep. The cracking percentage for fruits on the outer positions of the crown is 81%, while fruits located at the inner parts have a cracking rate of 46% (Lai, 2005). Two different potential occasions of cracking occur in ‘Pink’ wax apple fruits. One occurs when the fruit gets mature and there are different hypotheses with regard to the mechanism of this type of cracking:

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Sudden changes in turgor pressure inside the fruit by excessive water uptake. The skin of the fruit gets thinner when the fruit gets mature. Excessive fruit size caused by application of plant growth regulators.

The other occasion causing cracking occurs at any development stage of the fruit when excess low temperatures prevail (below 8 °C). Perforating bagging materials have less cracking incidences than nonperforating materials for fruits hanging on the tree. Also, foliar applications of calcium reduce fruit cracking and incidences of CI.

23.5

Pathological disorders

Wax apple fruits are fragile and thus easy to get bruised or injured before harvesting and during harvesting and handling processes. The injured areas are easily infected, facilitating rot and decay by pathogens such as Phytophothora palmivora, Colletotrichum gloeosporioides, Penicillium digitatum, Fusarium spp., and Mucor spp. Careful protection of fruits from on-the-tree to harvesting, handling and storage is very important to maintain injury-free and pathogen-free fruits (Dennis, 1983). Low temperature storage and MAP can reduce or retard fruit diseases (Table 23.2). Hot water treatments at 49 °C, 52 °C and 55 °C for 3 minutes, 5 minutes and 7 minutes are all effective in reducing and retarding the process of fruit rotting.

23.6

Insect pests and their control

Oriental fruit flies (Bactrocera dorsalis, Hendel) and citrus mealy bugs (Planococcus citri, Risso) are the most harmful insects, and cause great losses in wax apple production. Since Oriental fruit flies are important quarantine insects for international trade, it is thus very important to eradicate this particular insect for export purposes. Bagging of fruit on the tree is an effective measure to protect fruits from fruit flies laying eggs. Cold treatment is not suitable for wax apple fruits since this particular fruit is very sensitive to temperature. It takes more than ten days at 1 °C to eradicate Oriental fruit flies, and wax apple fruits acquire CI in only three days under this temperature (Table 23.1). Hot air treatment at 43 °C for nine hours killed all the artificially inoculated Oriental fruit flies in the fruit, but resulted in scald symptoms on all fruit skin (Chiang, 2005). Controlled atmosphere treatments using 100% nitrogen or 50% nitrogen gas + 50% CO2 for 4 to 6 days at 25 °C may cause fruit rotting and off-flavor (Hwang, 1988). Irradiation using gamma (γ)-ray at 250 Gy or γ-ray at 50 Gy in combination with 1 °C for six days kills all the Oriental fruit flies in the fruit without causing any damage or side effects (Shiesh, unpublished data).

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13.4 ± 4.4

17.6 ± 4.3

15.3 ± 4.0

16.4 ± 5.9

–v

10 °C, 5 days → 25 °C, 3 days

10 °C, 11 days

10 °C, 11 days → 25 °C, 3 days

10 °C, 23 days

10 °C, 23 days → 25 °C, 3 days

–

14.1 ± 5.1

15.9 ± 4.7

16.2 ± 3.3

–

6.5 ± 1.3

7.2 ± 1.7

7.5 ± 1.6

7.0 ± 1.9

7.0 ± 1.8

CK

TSS (°Brix)x

–

6.3 ± 1.6

6.4 ± 1.2

6.5 ± 1.8

6.21 ± 4

7.6 ± 1.6

PE

y Fruits

were stored at 10 °C for 5, 10 and 23 days and then transferred to 25 °C for 3 days. were packaged in 0.03 mm polyethylene bag. x TSS denotes total soluble solids. w Means ± SE. v Fruits decayed.

z Fruits

14.7 ± 5.3

15.0 ± 4.1w

10 °C, 5 days

12.4 ± 5.7

PEy

Skin color (a*)

CK

Treatmentsz

–

7.1 ± 1.3

7.7 ± 1.6

8.3 ± 1.1

4.5 ± 1.4

8.3 ± 0.8

CK

Firmness (lbs)

–

7.3 ± 1.3

7.6 ± 1.8

7.9 ± 2.3

10.9 ± 5.4

11.0 ± 5.0

PE

100

76

84

36

52

36

CK

100

60

52

28

8

8

PE

Decay (%)

0

0

10

12

40

0

CK

0

0

0

0

12

0

PE

Pitting (%)

Table 23.2 Effect of package with polyethylene bag and storage period on the skin color (a*), total soluble solids, firmness, decay, and pitting of wax apple fruit

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23.7

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Postharvest handling practices

23.7.1 Harvest operations The fruits of wax apple are perishable since these fruits have delicate skins outside and plenty of water inside and thus are easy to crack, bruise, rot and perish. The perishable fruits are thus not resistant either to long distance transportation or long term storage. Handlers should wear gloves to avoid scratching the fruits and place them gently in a cloth or any other soft-material bag.

23.7.2

Packinghouse practices

Grading In terms of quality there is a great variation among fruits harvested from different soils, climate conditions and management techniques. Fruit weight equal to or more than 150 g, total soluble solids equal or greater than 12 °Brix, deep red color, no visible damage and cracking on the surface are the minimum standards for high quality wax apple fruits in Taiwan. Packaging Reducing moisture loss, bruising and scarring are the primary consideration for wax apple packaging. Depending on shipping destinations, wrapping materials for individual fruits and packaging materials for the entire box are different. Usually plastic bags are used for preventing water loss from fruits and styrofoam bags or shredded paper for cushioning.

23.7.3

Recommended storage and shipping conditions

Low temperature storage Primarily due to water loss and rotting, wax apple fruits in Taiwan have a shelf life of only three to five days under ambient temperatures after harvesting. Reduced temperatures increase shelf life of wax apple fruits. The recommended storage temperature for ‘Pink’ fruits ranges from 10 to 15 °C. Fruits of ‘Pink’ stored at temperatures lower than 10 °C are susceptible to chilling injury (CI) with discoloration of the fruit skin (Table 23.1), while fruits stored above 15 °C are susceptible to rotting (Hwang, 1998). The shelf life of ‘Pink’ fruits could be extended from three to five days to 10 to 15 days when temperatures are kept between 10 to 15 °C (10 to 12 °C even better). The storage period could be even longer if fruit rotting can be controlled effectively. A shelf life of 20 days was achieved for the Malay apple stored at 5 °C (Basanta, 1998). Modified atmospheres packaging (MAP) Water loss is a big problem for wax apple storage. Fruit skin starts to shrink when water loss increases to more than 2% and the fruits bear no commercial value due to severe pitting on fruit skin caused by severe water loss of more than

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6% (Horng, 1988). Adequate packaging or bagging can reduce water loss problems easily as CI and rotting were reduced when ‘Pink’ fruits were bagged with polyethylene bags (Horng and Peng, 1983). Hwang (1998) reached the same conclusion (Table 23.2). Besides, fruits stored at 10 °C are firmer than that under higher temperatures. These fruits do not soften easily when temperature increases to ambient conditions. Also, polyethylene bagging reduces fruit rotting and skin pitting significantly. MAP is an easy way to improve fruit quality of wax apple fruits. Controlled atmospheres (CA) storage No CA storage research was done for the wax apple. The shelf life of Malay apple fruits was extended to 25 days with satisfactory quality when stored under CA storage at 1% oxygen, 11% or 14% CO2 and 5 °C (Basanta, 1998).

23.8

Conclusions

An extended shelf life and bruising-free postharvest procedure is very much expected and demanded for the fruit of wax apple and related species. However, due to the fragile nature of the fruits it is very difficult to find a breakthrough procedure better than the existing ones for the postharvest handling of fruits of wax apple and related species.

23.9

References

Akamine E K and Gao T (1979) ‘Respiration and ethylene production of fruits of species and cultivars of Psiduim and species of Engenia’, J. Amer. Soc. Hort. Sci., 104, 632–635. Ávila-Peńa D, Peńa N, Quintero L and Suárez-Roca H (2007) ‘Antinociceptive activity of Syzygium jambos leaves extract on rats’, J. Ethnopharmacology, 112, 380–385. Basanta A (1998) The postharvest storage of pomerac (Syzygium malaccense) under refrigerated and controlled atmosphere conditions, MPhil. Thesis, Department of Mechanical Engineering, University of the West Indies, St. Augustine, Trinidad and Tobago. Bhargava U C, Westfall A B and Siehr, D J (1968) ‘Preliminary pharmacology of ellagic acid from Juglans nigra (black walnut)’, Journal of Pharmaceutical Sciences, 57, 1728–1732. Chang Y-J, Chung M-Y, Tseng M-N, Chu C-C and Shü Z-H (2003) ‘Developmental stages affect characteristics of wax apple fruit skin discs cultured with sucrose-with special reference to color’, Scientia Hortic., 98, 397–407. Chaudhuri A K N, Pal S, Gomes A and Bhattacharya A (1990) ‘Antiinflammatory and related actions of Syzygium cumini seed extract’, Phytotherapy Research, 4, 5–10. Chen M-C (2006) Studies on the growth and development of wax apple fruits and postharvest technology, Master thesis of Graduate Institute of Tropical Agriculture, National Pingtung University of Science and Technology, Pingtung, Taiwan (in Chinese). Chiang S (2005) Chilling injury and quality of wax-apple following cold and heat treatment to disinfest Oriental fruit fly, Master thesis of Department of Horticulture, Chung Hsing University, Taichung, Taiwan (in Chinese). Chiu C-C (2003) Comparison on the horticultural characteristics of big-fruited lines of wax apples, MSc Thesis, Research Institute of Tropical Agriculture and International

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Cooperation, National Pingtung University of Science and Technology, Pingtung, Taiwan (in Chinese). De Lima T C M, Klüeger P A, Pereira P A, Macedo-Neto W P, Morato G S and Farias M R (1998) ‘Behavioral effects of crude and semi-purified extracts of Syzygium cumini Linn. skeels’, Phytotherapy Research, 12, 488–493. Dennis C (1983) Postharvest Pathology of Fruits and Vegetables, Food Science and Technology, a series of monographs, Academic Press. Djadjo Djipa C, Delmée M and Quetin-Leclercq J (2000) ‘Antimicrobial activity of bark extracts of Syzygium jambos (l.) Alston (Myrtaceae)’, J. Ethnopharmacology, 71, 307–313. Horng D (1988) Studies on ethylene biosynthesis of chilled wax apple, Ph.D. dissertation of Department of Horticulture, Taiwan University, Taipei, Taiwan (in Chinese). Horng D and Peng C (1983) ‘Studies on package, transportation and storage of wax apple fruits (Syzygium samaragense) (in Chinese)’, Natl. Chung Hsing Univ. Hort. J. 8, 31–39. Huang C-C and Wang D-N (2003) ‘The protection methods of chilling injury for wax apple.’ In: Proceedings of Agricultural Climatic Disasters Survey and Protection Techniques. TARI, Taichung, Taiwan (in Chinese). Huang C-C, Wang D-N and Liou T-D (2005) ‘Reduction and prevention of chilling injury by pruning and covering treatments on wax-apple (Syzgium samarangense Merr. et L.M. Perry)’, Crop, Environ. Bioinformatics, 2, 73–80 (in Chinese). Hwang B-Y (1998) Studies on chilling injury and handling technology of wax apple fruit (Syzgium samaragense Merr. et. Perry) during postharvest, Master thesis of Department of Horticulture, Chung Hsing University, Taichung, Taiwan, (in Chinese). Kelkar S M and Kaklij G S (1996) ‘A simple two-step purification of antidiabetic compounds from Eugenia jambolana fruit-pulp: proteolytic resistance and other properties’, Phytomedicine, 3, 353–359. Kim H M, Lee E H, Hong S H, Song H J, Shin M K, et al. (1998) ‘Effect of Syzygium aromaticum extract on immediate hypersensitivity in rats’, J. Ethnopharmacology, 60, 125–131. Kuo T-C (1995) ‘Effects of meteorological factors on yield and quality of wax apple in winter in Pingtung area (in Chinese)’, Res. Bull. Kaohsiung Dis. Agric. Res. Ext. Sta., 6, 40–48. Kuo Y-C, Yang L-M and Lin L-C (2004) ‘Isolation and inmunomodulatory effects of flavonoids from Syzygium samarangense’, Planta Medica, 70, 1237–1239. Kurokawa M, Hozumi T, Basnet P, Nakano M, Kadota S, et al. (1998) ‘Purification and characterization of Eugeniin as an antiherpesvirus compound from Geum japonicum and Syzygium aromaticum’, Journal of Pharmacology and Experimental Therapeutics, 284, 728–735. Lai R-M (2005) ‘Study on fruit cracking factors of wax apple (in Chinese)’, Res. Bull. Kaohsiung Dis. Agric. Res. Ext. Sta., 16(3), 37–48. Lee M-C (2003) ‘Manganese improves wax apple fruit quality’, Res. Bull. Kaohsiung Dis. Agric. Res. Ext. Sta., 44, 14–15 (in Chinese). Liao M-L, Liu M-S and Yang J-S (1983) ‘Respiration measurement of some important fruit in Taiwan’, Acta. Hort. (ISHS), 138, 227–246. Liaw S-C, Shü Z-H, Lin H-L and Lee K-C (1999) ‘Effects of sugars on anthocyanin biosynthesis in wax apple fruit skin (in Chinese)’, J. Agric. Assoc. China, New Series, 185, 72–80. Lo H-P (2008) Studies on fruit development and splitting of wax apple (Syzygium samarangenes Merr. et Perry), Ph.D. dissertation of Department of Horticulture, Chung Hsing University, Taichung, Taiwan (in Chinese). Morton J F (1987) Fruits of Warm Climates, Julia F. Morton, Miami, FL. Muruganandan S, Srivastava K, Chandra S, Tandan S K, Lal J and Raviprakash V (2001) ‘Anti-inflammatory activity of Syzygium cumini bark’, Fitoterapia, 72, 369–375. Nadkarni K M and Nadkarni A K (1976) Indian Materia Medica, Vol 1. 3rd ed. Mumbai: M/S Popular Prakasan Pvt. Ltd.

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Nagaraju N and Rao K N (1989) ‘Folk medicine for diabetes from Rayalaseema of Andhra Pradesh’, Ancient Science of Life, 9, 31–35. Nagaraju N and Rao K N (1997) ‘Antidiabetic activity of some medicinal plants of Rayalaseema region, India’, 35th world congress on Natural Medicines, Tirupathi, India, AB, 300:107. Nakasone H Y and Pall R E (1988) Tropical Fruits, CAB Intl., U.K, 1988. Pan H-H and Shü Z-H (2007) ‘Temperature affects color and quality characteristics of “Pink” wax apple fruit discs’, Scientia Hortic., 112, 290–296. Prince P S M, Menon V P and Pari L (1998) ‘Hypoglycemic activity of Syzygium cumini seeds: effects on lipid peroxidation in alloxan diabetic rats’, J. Ethnopharmacology, 61, 1–7. Rao B K, and Rao Ch. A (2001) ‘Hypoglycemic and antihyperglycemic activity of Syzygium alternifolium (Wt.) Walp. seed extracts in normal and diabetic rats’, Phytomedicine, 8, 88–93. Shü Z-H (1999) ‘Position on the tree affects fruit quality of Bald-cut wax apples’, J. Appl. Hort., 1, 15–18. Shü Z-H and Paull R E (2008) ‘Syzygium spp. – commercially important species’. The Encyclopedia of Fruits and Nuts, CAB International, Oxfordshire, UK. Shü Z-H and Yeh D-J (1998) ‘N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) affects quality of wax apple fruits (in Chinese)’, J. Natl. Pingtung Univ. Sci. Technol., 7, 265–269. Shü Z-H, Chu C-C, Hwang L-J and Shieh C-S (2001) ‘Light, temperature and sucrose affect color, diameter and soluble solids of disks of wax apple fruit skin’, HortScience, 36, 279–281. Shü Z-H, Liaw S-C, Lin H-L and Lee, K-C (1998) ‘Physical characteristics and organic compositional changes in developing wax apple fruits’, J. Chinese Soc. Hort. Sci., 44, 491–501. Shü Z-H, Lin T-S, Lai J-M, Huang C-C, Wang D-N and Pan H-H (2007) ‘The industry and progress review on the cultivation and physiology of wax apple – with special reference to “Pink” variety’, Asian and Aust. J. Plant Sci. Biotechnol., 1(2), 48–53. Shü Z-H, Meon Z, Tirtawinata R and Thanarut C (2008) ‘Wax apple production in selected tropical Asian countries’, Acta Hort. (ISHS), 773, 161–164. Shü Z-H, Thanarut C and Yang Y-S (2009) ‘A comparison on the wax apple industry between Taiwan and Thailand’. Proceedings of the Symposium on South Taiwan Health Care and Health Industry. Meiho Institute of Technology, Neipu, Pingtung, Taiwan. Shü Z-H, Wang D-N and Sheen T-F (1996) ‘Wax apple as a potential economic crop for the world’. In: Vijaysegaran S, Pauziah M, Mohamed M S and Ahmad Tarmizi S (eds.), Proceedings of the International Conference on Tropical Fruits, vol. I. Malaysian Agr. Res. Dev. Inst., Serdang, Selangor, Malaysia. Simirgiotis M J, Adachi S, To S, Yang H, Reynertson K A, et al. (2008) ‘Cytotoxic chalcones and antioxidants from the fruits of Syzygium samarangense (Wax Jambu)’, Food Chemistry, 10, 813–819. Slowing K, Carretero E and Villar A (1994a) ‘Anti-inflammatory activity of leaf extract of Eugenia jambos in rats’, J. Ethnopharmacology, 43, 9–11. Slowing K, Söllhuber M, Carretero E and Villar A (1994b) ‘Flavonoid glycosides from Eugenia jambos’, Phytochemistry, 37, 255–258. Stanely Mainzen P, Menon V P and Pari L (1998) ‘Hypoglycaemic activity of Syzigium cumini seeds: effect on lipid peroxidation in alloxan diabetic rats’, J. Ethnopharmacology, 61, 1–7. Teixeira C C, Pinto L P, Kessler F H, Knijnik L, Pinto C P, et al. (1997) ‘The effect of Syzygium cumini (L.) skeels on post-prandial blood glucose levels in non-diabetic rats and rats with streptozotocin-induced diabetes mellitus’, J. Ethnopharmacolology, 56, 209–213. Thammanna, Rao KN and Madhavachetty K (1994) Angiospermic Wealth of Tirumala. D.V.L.N. Murthy, T.T. Devasthanams, Tirupathi, India.

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Thammanna, Rao KN and Nagaraju N (1990) Medicinal Plants of Tirumala. M.V.S. Prosad, T.T. Devasthanams, Tirupathi, India. Toda M, Kawabata J and Kasai T (2000) ‘Alpha-glucosidase inhibitors from clove (Syzygium aromaticum)’, Bioscience, Biotechnology and Biochemistry, 64, 294–298. Van Wyk B E, van Oudtshoorn B and Gericke N (1997) Medicinal Plants of South Africa, Briza Publications, Pretoria, pp. 250. Wang D-N (1991) ‘Past, present and future of wax apple production in Taiwan’. In: Yang C-R (ed.) Proceedings of the Symposium Fruit Production, Research and Development in Taiwan, Chia-Yi Agricultural Experiment Station, Taiwan Agricultural Research Institute, Taiwan (in Chinese). Wang D-N (2006) ‘Wax apple’. In: B. Horng et al. (eds) Taiwan Agricultural Encyclopedia, 2nd edition, Taipei, Taiwan (in Chinese). Young J-F (1951) Fruits in Taiwan. Chia-Yi Agricultural Experiment Station, Chia-Yi., Taiwan (in Chinese).

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Plate XL (Chapter 23) Different varieties of wax apple fruits (courtesy of Dr Elhadi Yahia).

Plate XLI

(Chapter 23) A wax apple tree loaded with fruits (some of the fruits are wrapped by paper bags, courtesy of Chi-cho Huang).

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Plate XLII

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(Chapter 19) (a) Star apple fruit on the tree and (b) exterior and interior of the star apple fruit.

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(b)

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Plate XLIII (Chapter 24) (a) White sapote tree, (b) white sapote fruit, (c) interior and exterior of white sapote fruit.

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24 White sapote (Casimiroa edulis Llave & Lex) E. M. Yahia and F. Gutierrez-Orozco, Autonomous University of Queretaro, Mexico

Abstract: White sapote is a climacteric fruit and only slightly susceptible to chilling injury. The fruit is commercially produced and consumed in few countries. Limited information is available on its postharvest physiology and handling, and therefore research is needed on several physiological, biochemical, pathological, and entomological aspects related to this fruit. This chapter discusses some of the information available on the handling of the fruit. Key words: Casimiroa edulis, white sapote, postharvest, quality, nutrition, health, processing, insects.

24.1

Introduction

Contrary to what is sometimes believed, white sapotes are not related to the Sapotaceae family, but actually belong to the Rutaceae family. Although white sapotes are not very popular among consumers they still have great potential for commercialization as an exotic fruit. In addition, the white sapote tree has great adaptability to arid regions which represents a sustainable option in these areas where other species do not grow. However, information on their postharvest biology and technology to establish optimum storage and transport conditions is still very limited. 24.1.1 Origin, botany, morphology and structure White sapote (Casimiroa edulis Llave & Lex), also known as Mexican-apple, casimiroa, zapote blanco, chapote, matasano, cacchique, ceaxmisttea, cochitzapoti, is native to Mexico and Central America. It can be found in central and southern Mexico as a cultivated and wild species and is also grown in Guatemala, El

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Salvador and Costa Rica. Commercially, it is grown in New Zealand and on a small scale in South Africa. It is an evergreen tree that can grow up to 5–20 meters depending on the cultivar and type of soil. It has a dense crown, with glossy and bright green leaves. White sapote flowers are small and green to yellow which make them very attractive to insects like bees or ants. Fruit of white sapote vary from 2 to 15 cm in length with an apple-green color when young to orange-yellow color at maturity. Fruit (see Plate XLIII(A–C) in the colour section between pages 238 and 239) are oval, symmetrical or irregularly shaped with a thin and smooth skin that may be bitter. Its external appearance sometimes resembles that of an apple. Flesh color depends on the variety. Fruit with green skin present white flesh, while fruit with yellow-colored skin present flesh of the same color. The flesh is sweet and presents a gritty texture. Its flavor is similar to that of peach or banana and it may be bitter sometimes. If the fruit is left to become overripe, the flesh becomes pungent and an unpleasant flavor develops (Morton, 1987). 24.1.2 Worldwide importance White sapote adapts to subtropical weather, growing not only in Mexico and the United States, but also in temperate areas of New Zealand, Australia, and Israel. The fruit has recently been introduced in Japan, where it is little known as a fresh crop (Yamamoto et al., 2007). White sapote is also cultivated in Egypt for its fruit (Romero et al., 1983). Interest in commercialization of fresh white sapote in the United States and other countries has increased in recent years, as has interest in its medicinal properties (Campbell and Vallis, 1994). 24.1.3 Culinary uses, nutritional value and health benefits Fruit of white sapote are usually eaten alone or mixed in fruit salads, and can be served with cream and sugar. The pulp can be added to ice cream, milkshakes or made into jam. The nutritional value of white sapote is presented in Table 24.1. White sapote fruit are rich in β-carotene and ascorbic acid. Reducing sugars contribute to 66.2% of the total sugars in pulp which presents about 14.7 °Brix (Osama Samaha, 2002). Antioxidant capacity of white sapote leaf-extracts has been evaluated using the ABTS+ (2,2′-azinobis(3-ethylbenzothiazolone-6-sulfonic acid) free radical assay). Ethanol extracts presented the highest values of antioxidant capacity followed by the ethyl acetate extracts (842 and 712 μM Trolox equivalents g−1 dry weight, respectively). Phenolic compounds isolated from leaves extracts included quercetin and its 3-O-rutinoside, 6-hydroxy 5-methozyflavone, and 5-methosyflavone 6-O-β-D-glucoside (Awaad et al., 2006). It is generally believed that white sapote seeds are toxic to humans if eaten raw. Indeed, its common name ‘matasano’ in Spanish means ‘killing healthy person’. In Mexico and some other countries it is claimed that white sapote fruit helps to relieve pain caused by arthritis and rheumatism. Actually, the meaning of the Nahuatl name for white sapote is ‘sleepy sapote’ or ‘sleep-producing sapote’.

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Nutrient value of white sapote (100 g of fruit)

Constituent

Approximate value

Water content Protein Fat Fiber Ash Calcium Phosphorus Iron Carotene Thiamin Riboflavin Niacin Ascorbic acid

78.3% 0.143 g 0.03 g 0.9 g 0.48 g 9.9 mg 20.4 mg 0.33 mg 5.98 mg 0.042 mg 0.043 mg 0.472 mg 37.75 mg

Source: Morton (1987); Osama Samaha (2002).

There have been reports about the sedative properties of seed, bark and leaf extracts in Mexico where they have been used for a long time for these purposes. All these effects are thought to be due to the presence of the glucoside casimirosine, mainly in seeds but also in the bark and leaves. The blood-pressure lowering properties of white sapote have been confirmed in some studies (Petit-Play et al., 1982) and extracts of the leaves, bark and seeds are used for this purpose. In Mexico, a decoction from the leaves and seeds is used to treat anxiety, insomnia and hypertension (Vidrio and Magos, 1991; Hernandez, 1993; Garzon-de la Mora, 1999). Compounds with cardiovascular activity were identified as histamine derivatives like N,N-dimethylhistamine (Magos et al., 1999). One study performed in mice showed that extracts prepared from white sapote leaves possessed sedative properties along with anxiolytic and anti-depressant activities when given at 6.25, 12.5, and 50 mg kg−1 (Mora et al., 2005). Leaves of Caimiroa edulis showed anxyolitic effects in rats, causing side effect reactions like reduced mobility (Molina-Hernandez et al., 2004). In rats, aqueous extracts of white sapote seed have been shown to present vaso-relaxing activity which was found to be endothelium-dependent (Magos et al., 1995; Muccillo Baisch et al., 2004). Some other compounds such as coumarins, flavonoids and limonoids, among others, have been found in white sapote (Dreyer and Bertelli, 1976; Murphy et al., 1968; Rizvi et al., 1984; Sondheimer et al., 1959). Some of these compounds are known to present diuretic or anti-inflammatory properties (Morton, 1987). A polymethoxylated flavone called zapotin has been isolated from white sapote which induced cellular differentiation, cell death and cell cycle arrest in HL-60 promyelocytic cells (Mata-Greenwood et al., 2001). Zapotin has also shown chemopreventive activity by inhibiting cell growth of the colon cancer cell lines HT-29, SW480, and SW620. In addition, it caused cell cycle arrest as well as an increase in cell apoptosis which may suggest that this compound could be used as a therapeutic agent in colon carcinogenesis (Murillo et al., 2007). Extracts of

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white sapote seeds also showed anti-mutagenic action and inhibited induced preneoplastic lesions in a mouse model (Ito et al., 1998). Isolation of phytochemical compounds in these extracts showed four furocoumarins: phellopterin, isopimpinellin, (R, S)-5-methoxy-8-[(6,7-dihydroxy-3,7-dimethyl-2-octenyl)osy] psoralen, and (R, S)-8-[(6,7-dihydroxy-3,7-dimethyl-2-octenyl)oxy]psoralen; four alkaloids: casimiroin, 4-methoxy-1-methyl-2(1H))-quinolinone, 5-hydrxoxy-1methyl-2-phenyl-4-quinolone, and γ-fagarine; and two flavonoids: zapotin and 5,6,2′-trimethoxyflavone (Ito et al., 1998). Lastly, leaf and stem extracts of white sapote showed fungicidal actions against Rhizopus stolonifer of ciruela fruit (Spondias purpurea L.) during storage (Bautista-Banos et al., 2000).

24.2

Fruit development and postharvest physiology

24.2.1 Fruit growth, development and maturation The growth of white sapote fruit follows a single sigmoidal pattern (Yonemoto et al., 2006) and maturity is reached 6–9 months after blooming. 24.2.2 Respiration, ethylene production and ripening White sapote is a climacteric fruit (Yahia, 2004). Fruit kept at 21 °C and 82% RH had a respiratory peak after 4–5 days (199 mL CO2 kg−1 h−1, 651 μL C2H4 kg−1 h−1) (Lozano et al., 2006). Respiration rate is reduced when fruit is stored at 1 °C and no ethylene production is observed during these conditions (Yonemoto et al., 2002). Total sugar content of harvested fruit kept at 21 °C and 82% relative humidity (RH) did not change during ripening but the level of reducing sugars increased from 6.1 to 7.8%. The ratio °Brix/acidity increased during ripening (from 28.4 to 34.1%) as a consequence of the increased reducing sugars content and decreased acidity (Lozano et al., 2006).

24.3

Maturation and quality components and indices

White sapote fruit should be harvested before ripening (Morton, 1987). The days after pollination could be used as a maturity index: for white sapote cultivar ‘Cuccio’, it takes 212 days after pollination to reach maturity. Another maturity index could be percent dry matter, since this parameter is strongly correlated with total soluble solids. A more convenient and non-destructive maturity index is skin color measured by a colorimeter. In that case, a* value is measured on the sunexposed side while b* is evaluated on the shaded side. Seed color could also be measured to determine maturity (Yonemoto et al., 2006). Skin color and size are used as quality parameters and according to McGregor (1987), good quality fruit are yellow to yellowish-green and are 60–120 mm in diameter. According to Morton (1987), skin color of fully ripe white sapote fruit is usually apple-green to orange-yellow. White sapote fruit (see Plate XLIII(A–C)

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in the colour section) are easily bruised if not handled correctly which produces bitterness of the flesh. Overripe fruit are pungent and have an unpleasant flavor (Morton, 1987). A value of 18% dry matter at maturity of cv. ‘Cuccio’ is reported. In another study, mature fruit were reported to present a pH of about 5.1, 0.34% acidity, total soluble solids content of about 19.9% and about 14.7 °Brix (Osama Samaha, 2002). Volatile compounds responsible for the aroma of white sapote fruits were identified during fruit ripening. They corresponded to 4 esters, 6 alcohols, 1 ketones, 4 aldehydes, and 3 terpenes. The sweet and fruity aroma was found to be originated from ethyl butanoate (El-Mageed, 2007). Some other aromatic compounds with properties to attract fruit flies have been identified in white sapote: myrcene, styrene, 1,2,4-trimethylbenzene, 1,8-cineole, linalool, and β-trans-ocimene (Gonzalez et al., 2006).

24.4

Preharvest factors affecting fruit quality

Temperatures below 3 °C will damage young fruit, affecting the quality of ripe white sapotes (Yonemoto et al., 2004).

24.5

Postharvest handling factors affecting quality

24.5.1 Temperature management Studies on white sapote cv. ‘Yellow’ showed that the respiration peak is reached at day four from harvest and when fruit are held at 35 °C, and at day 6 at 15, 20, 25, and 30 °C. When stored at 10 °C a respiration peak was not evident. Respiration rate was slowed down at 1 °C and there was no ethylene production. Temperatures higher than 30 °C induced skin browning, which was not observed at 10–25 °C. Fruit surface softening was observed at 5 °C. Fruit stored at 1 °C for 10 to 63 days ripened normally after transfer to 25 °C. However, chilling injury was observed in fruit stored for 63 days at 1 °C (Yonemoto et al., 2002). 24.5.2 Physical damage Special care must be taken not to harvest the fruit by pulling it manually since the stem will be severed completely producing fruit bruising and decay later on. Young fruits bruise very easily, developing flesh bitterness, and therefore they must be handled with care (Morton, 1987). Fruit that has been physically damaged will develop browning of the skin and pulp bitterness (Yahia, 2004).

24.6

Physiological disorders

24.6.1 Chilling injury No production of white sapote is seen when ambient temperatures fall below −2.5 °C and as already mentioned, young fruit are severely damaged at 3 °C.

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However, when mature white sapote fruit were exposed for five hours at −2 °C for five days, no damage was observed. Thus, the recommended temperature for cultivation is higher than −2 °C (Yonemoto et al., 2004). As mentioned above, chilling injury was observed in fruits stored at 1 °C for 63 days (Yonemoto et al., 2002). 24.6.2 Other physiological disorders Quarantine treatments have been tested on white sapote in order to kill Anastrepha suspense. Immersion of fruit in water at 43.3 °C for 90 or 120 minutes or at 46 °C for 60 or 90 minutes produced pitting and decay and ripening was abnormal. The level of decay also increased and ripening was affected when white sapote fruit was treated with methyl bromide at 20 to 40 g m3. In addition this produced a reddish hue on the fruit (Hallman, 1993).

24.7

Pathological disorders

Fruit of white sapote present resistance to Phytophthora and Armillaria (Morton, 1987). White sapote is a host of Puccinia thaliae (Sivanesan, 1970). Although not affected by it, white sapote tree is a carrier of psorosis virus disease (El-Tomi et al., 1963).

24.8

Insect pests and their control

Few pests affect white sapote fruit, however, the fruit are highly infested by Anastrepha ludens (Aluja et al., 1987). Some volatile compounds in white sapote have been found to attract A. ludens to baited traps (Gonzalez et al., 2006). Although not a target of the African citru psylla, Trioza erytreae, white sapote has been reported as a host for this pest (Fernandes and Franquinho Aguiar, 2001).

24.9

Postharvest handling practices

24.9.1 Harvest operations The white sapote season starts in late May until August in the Bahamas while in Mexico it goes from June to October (Morton, 1987). In Florida, fruit matures in November or December (Schroeder, 1954). Fruit are harvested by cutting the stem and leaving a small part of the peduncle, which falls once the fruit is fully ripe. When fruit are harvested just before full ripeness, they become soft soon after. Because of that, it is recommended to harvest white sapotes some weeks before ripeness so fruit can develop complete flavor (Morton, 1987).

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24.9.2 Packinghouse practices Some common practices during white sapote packing include grading according to size and wrapping to delay ripening. Fruit are usually packed in wooden boxes with some type of cushioning material to avoid physical damage during holding and shipping (Morton, 1987). 24.9.3 Recommended storage and shipping conditions Maintaining white sapote fruit at 19–21 °C and 85–90% RH prolongs their shelf life for up to 2–3 weeks (McGregor, 1987). The fruit might benefit from an adequate modified atmosphere system (Yahia, 1998).

24.10

Processing

White sapote fruit can be used to make different products such as juice, jam, tart, biscuit, and sherbet (Osama Samaha, 2002).

24.11

Conclusions

White sapote is a climacteric fruit with potential for commercialization due to its organoleptic properties and the fact that it is considered an exotic fruit. However, limited information on the postharvest biochemistry, physiology and technology is available and thus it is difficult to establish the optimum conditions that would preserve quality during extended storage and shipping. White sapote fruit, although mainly consumed fresh, could be used to produce added-value products such as preserves and other products.

24.12

References

Aluja M J, Guillen G, De la Rosa M, Cabrera M, Celedonio H, et al. (1987), ‘Natural host plant survey of the economically important fruit flies (Diptera: Tephritidae) of Chiapas, Mexico’, Fla Entomol, 70, 329–338. Awaad A S, El-Sayed N H, Maitland D J, Mabry T J (2006), ‘Phenolic antioxidants from Casimiroa edulis’, Pharmaceutical Biology, 44 (4), 258–262. Bautista-Banos S, Hernandez-Lopez M, Diaz-Perez J C, Cano-Ochoa C F (2000), ‘Evaluation of the fungicidal properties of plant extracts to reduce Rhizopus stolonifer of “ciruela” fruit (Spondias purpurea L.) during storage’, Postharvest Biology and Technology, 20, 99–106. Campbell R J, Vallis S (1994), ‘The white sapote, public appeal and commercial production in Florida’, Proc Fla State Hort Soc, 107, 342–343. Dreyer D L, Bertelli D J (1976), ‘The structure of zapotin’, Tetraheron, 23, 4607–4612. El-Mageed M A A (2007), ‘Development of volatile compounds of avocado and casimiroa during fruit maturation’, Arab Universities Journal of Agricultural Sciences, 15 (1), 89–100. El-Tomi A, Zidan Z I, Abo-Rehab M (1963), ‘Susceptibility of citrus varieties to psorosis virus disease’, Ann Agric Sci, 8 (1), 389–411.

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Fernandes A, Franquinho Aguiar A M (2001), ‘Development of quarantine pests Toxoptera citricida (Kirkaldy) and Trioza erytreae (Del Guercio) in the Archipelago of Madeira’, boletin de Sanidad Vegetal, Plagas, 27 (1), 51–58. Garzon-de la Mora P, Garcia-Lopez P M, Garcia-Estrada J, Navarro-Ruiz A, VillanuevaMichel T, Villareal-de Puga L M (1999), ‘Casimiroa edulis’ seed extract show anticonvulsive properties in rats’, Journal of Ethnopharmacology, 68, 275–282. Gonzalez R, Toledo J, Cruz-Lopez L, Virgen A, Santiesteban A, Malo E A (2006), ‘A new blend of white sapote fruit volatiles as potential attractant to Anastrepha ludens (Diptera: Tephritidae)’, Ecology and Behavior, 99 (6), 1994–2001. Hallman G Y (1993), ‘Potential quarantine treatments for white sapote infested with Caribbean fruit fly (Diptera: Tephritidae)’, Journal of Economic Entomology, 86 (3), 793–797. Hernandez M M (1993), ‘Contribucion al conocimiento del estudio etnobotanico, quimico y farmacologico de las plantas tranquilizantes en los mercados de Morelia, Michoacan, Mexico’, Tesis Licenciatura. Universidad Michoacana de San Nicolas de Hidalgo, Morelia Michoacan, p. 77. Ito A, Shamon L A, Yu B, Mata-Greenwood E, Lee S K, et al. (1998), ‘Antimutagenic constituents of Casimiroa edulis with potential cancer chemopreventive activity’, J Agric Food Chem, 46, 3509–3516. Lozano GMA, Valle GS, Marroquín AMM, and Ybarra MMC (2006), ‘Comportamiento en poscosecha de frutos de zapote blanco en Texcoco, México’, Revista Fitotecnia Mexicana, 29(2), 129–133. Magos J A, Vidrio H, Enriquez R (1995), ‘Pharmacology of Casimiroa edulis; III. Relaxant and contractile effects in rat aortic rings’, Journal of Ethnopharmacology, 47, 1–8. Magos J A, Vidrio H, Reynolds W F, Enriquez R G (1999), ‘Pharmacology of Casimiroa edulis; IV. Hypotensive effects of compounds isolated from methanolic extracts in rat and guinea pigs’, Journal of Ethnopharmacology, 64, 35–44. Mata-Greenwood E, Ito A, Westenburg H, Cui B, Mehta R G, et al. (2001), ‘Discovery of novel inducers of celular differentiation using HL-60 promyelocytic cells’, Anticancer Res, 21: 1763–1770. McGregor BM (1987), Tropical Products Transport Handbook. United States Department of Agriculture, Office of Transportation, Agric. Handbook No. 688. Molina-Hernandez M, Tellez-Alcantara N P, Perez Garcia J, Olivera Lopez J I, Jaramillo M T (2004), ‘Anxiolytic-like actions of leaves of Casimiroa edulis (Rutaceae) in male Wistar rats’, Journal of Ethnopharmacology, 93, 93–98. Mora S, Diaz-Veliz G, Lungenstrass H, Garcia-Gonzalez M, Coto-Morales T, et al. (2005), ‘Central nervous system activity of the hydroalcoholic extract of Casimiroa edulis in rats and mice’, Journal of Ethnopharmacology, 97, 191–197. Morton J (1987), ‘White sapote,’ in Fruits of Warm Climates, Julia F. Morton, Miami, FL, pp. 191–196. Muccilo Baisch A L, Urban H, Navarro Ruiz A (2004), ‘Endothelium-dependent vasorelaxing activity of aqueous extract of lyophilized seed of Casimiroa edulis (AECe) on rat mesenteric arterial bed’, Journal of Ethnopharmacology, 95, 163–167. Murillo G, Hirschelman W H, Ito A, Moriarty R M, Kinghorm A D, et al. (2007), ‘Zapotin, a phytochemical present in a Mexican fruit, prevents colon carcinogenesis’, Nutrition and Cancer, 57 (1), 28–37. Murphy J W, Toube T, Cross D A (1968), ‘Spectra and stereochemistry. XXIX. The structure of zapoterin’, Tetrahedron, 49, 5153–5156. Osama Samaha R A (2002), ‘Characteristics and utilization of white sapote (Casimiroa edulis L. Lave) fruits’, Alexandria Journal of Agricultural Research, 47 (3), 49–53. Petit-Play G, Rideau M, Chenieuz C J (1982), ‘Etude de oquelquea Rutacees a alcaloides. II. Ruta graveolens: Revue otanique cimique et pharmacologique. (Etue particuliere dea acaloides quanternaires quinoleiques.)’, Plant Med Phytother 16: 55–72. Risvi S H, Kapil R S, Shoeb A (1984), ‘Alkaloids and coumarins of Casimiroa edulis’, Journal of Natural Products, 48 (1), 46.

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Postharvest biology and technology of tropical and subtropical fruits

Romero M L, Escobar L I, Lozoya X, Enriquez R G (1983), ‘High-performance liquid chromatographical study of Casimiroa edulis’, J Chromatogr, 281, 245–251. Schroeder C A (1954), ‘Fruit morphology and anatomy in the white sapote’, Botanical Gazette, 115 (3), 248–254. Sivanesan A (1970), ‘Puccinia thaliae’, IMI Descriptions of Fungi and Bacteria, 27, sheet 267. Sondheimrer F, Meisels A, Kinel F A (1959), ‘Constituents of Casimiroa edulis Llave et Lex. V. Identity of casimirolid and obacunone’, Org Chem, 23, 2413–2416. Vidrio H, Magos G A (1991), ‘Pharmacology of Casimiroa edulis: II. Cardiovascular effects in the anesthetized dog’, Planta Medica, 57, 217–220. Yahia E M (2004), ‘Sapodilla and related fruits’, in United States Department of Agriculture, Agric. Handbook No. 66. Available from http://www.ba.ars.usda.gov/hb66/index.html (accesed on 6 June 2010). Yahia EM (1998), ‘Modified and controlled atmospheres for tropical fruits’, Horticultural Rviews, 22, 123–183. Yamamoto M, Tomita T, Onjo M, Ishihata K, Kubo T, Tominaga S (2007), ‘Genetic diversity of white sapote (Casimiroa edulis La Llave & Lex.)’, Hortscience, 42 (6), 1329–1331. Yonemoto Y, Higuchi H, Kitano Y (2002), ‘Fruit ripening as affected by storage temperature in white sapote (Casimiroa edulis Llave and Lex.)’, Japanese Journal of Tropical Agriculture, 46 (2), 82–87. Yonemoto Y, Inoue H, Majikina M, Okuda H (2004), ‘Critical temperature leading to frost damage in young fruits of white sapote (Casimiroa edulis Llave & Lex.) cv. Florida’, Japanese Journal of Tropical Agriculture, 48 (2), 88–93. Yonemoto Y, Nomura K, Inoue H, Majikina M, Okuda H (2006), ‘Index for harvesting time of white sapote (Casimiroa edulis Llave & Lex.) cv. “Cuccio” ’, Journal of Horticultural Science and Biotechnology, 81 (1), 18–22.

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(a)

Plate XLII

(b)

(Chapter 19) (a) Star apple fruit on the tree and (b) exterior and interior of the star apple fruit.

(a)

(b)

(c)

Plate XLIII (Chapter 24) (a) White sapote tree, (b) white sapote fruit, (c) interior and exterior of white sapote fruit.

© Woodhead Publishing Limited, 2011

Index

α-GAL see α-galactosidases α-galactosidases, 376–7 α-naphthaleneacetic acid, 197 abamectin, 12 abrasion injury, 96 acetaldehyde, 322 acid invertase, 91, 95 aflatoxin, 152, 159, 231, 232 African citru psylla see Trioza erytreae African Pride atemoya, 410 after full bloom (AFB), 65–6 AgroFresh, 186 Akko pomegranate, 301 alcohol insoluble solid (AIS), 198 alizarin, 53 almonds see Prunus amygdalus Batsh Alternaria, 181–2 Alternaria passiflorae, 136 Alternaria spp., 302 ambli see Tamarindus indica L. 1-aminocyclopropane-1-carboxylic acid, 132, 197 Amyelois transitella, 231 amylase, 377 Ananas comosus L. Merr., 194–212 culinary uses and nutritional value, 196 fruit development and postharvest physiology, 196–7 growth, development and maturation, 196–7 respiration and ethylene production, 197 insect pests and their control, 206, 208 origin, morphology and structure, 194–5 morphological structure, 195

pathological disorders, 206, 207 postharvest diseases nature and control, 207 physical and biochemical changes during maturation and ripening, 197–201 acids, 199 ascorbic acid, 199–200 colour, 197–8 mineral, 201 phenolic compounds, 200 protein, 200 starch, 198 sugars, 198–9 texture, 198 volatile compounds, 201 physiological disorders, 204–6 Blackheart, 204–5 common chilling injury, 204 flesh translucence, 205–6 postharvest factors affecting quality, 203–4 atmosphere, 203–4 physical damage, 203 relative humidity, 203 temperature, 203 postharvest handling practices, 208–10 harvesting, 208 harvesting pineapple for processing in Malaysia, plate XIX packaging and transportation, 209–10 packinghouse operations, 208–9 pineapple size classification under CODEX standard, 210

© Woodhead Publishing Limited, 2011

484

Index

recommended storage and shipping conditions, 210 ripening and senescence control, 210 preharvest factors affecting fruit quality, 201–2 climatic condition, 201–2 cultural practices, 202 major volatiles found in pineapple, 202 production on peat soil in Malaysia, plate XVIII soil, 201 processing fresh-cut processing, 211 other processed products, 211 worldwide importance and economic value, 195–6 Anastrepha ludens, 183, 358, 479 Anastrepha suspense, 479 Animal and Plant Health Inspection Service (APHIS), 108, 110 Annona cherimola Mill. × Annona squamosa L., 399–422 control of ripening and senescence, 417–20 1-methylcyclopropene, 418 calcium carbide, 418–19 chemicals, 419–20 fruit firmness, 420 modified atmosphere, 417–18 respiration and ethylene production rates, 419 culinary uses, nutritional value and health benefits, 404–5 diseases, insect pests and their control, 414–15 mummified fruit, 414 fruit development and postharvest physiology, 405–8 growth, development, maturation, 405 maturity, 408–10 origin, botany, morphology and structure, 399–403 cultivated atemoyas in some countries, 403 Golden Flesh atemoya, Plate XXXV(G) Pet Pakchong atemoya, Plate XXXV(H) physiological disorders, 412–13 African Pride atemoya respiration and ethylene production, 412 chilling injury, 412–13 other physiological disorders, 413

postharvest fruit blackening and tree fruit cracking, 413 postharvest handling factors affecting quality, 411–12 atmospheric conditions, 411–12 physical damage, 411 temperature management, 411 postharvest handling practices, 415–21 bagging of Pet Pakchong fruit, 416 harvest operations and packinghouse practices, 415–17 recommended storage and shipping conditions, 420–1 preharvest factors affecting fruit quality, 410–11 fruit bagging, 410–11 fruit setting and timing of harvest, 410 gibberellic acid application, 410 processing, 421–2 fresh-cut processing, 421 other practices, 421–2 respiration, ethylene production, and ripening, 405–8 aroma volatiles, 408 fruit softening, 406–8 means of fruit weight and specific gravity, 406 Nang, Fai and African pride atemoya, 407 respiration and ethylene production, 405–6 volatile chromatogram of ripe Pet Pakchong atemoya, 409 worldwide importance and economic value, 403–4 Annona muricata L., 363–86 culinary uses, nutritional value and health benefits, 366–7 fruit growth and ripening, 367–70 growth, development and maturation, 367–8 Morada soursop respiration and ethylene production, 369 respiration, ethylene production and ripening, 368–70 ripe fruit, Plate XXXIII(B) hydrolytic and oxidative enzymes activities, 375–8 α- and β-galactosidases, 376–7 amylase, 377 pectin methylesterase and polygalacturonase, 376

© Woodhead Publishing Limited, 2011

Index polyphenol oxidase and peroxidase, 377–8 maturity and quality components and indices, 370–9 aroma compounds, 378–9 colour and pigments, 371 dry matter, 371 firmness, 374 pectic substances, 375 phenolic compounds, 373 pulp firmness of Morada soursop, 374 soluble solids and sugars, 371–2 starch content, 374–5 titratable acidity and pH, 372–3 origin, botany, morphology and structure, 364 pulp aspect, 365 soursop at physiological maturity, Plate XXXIII pathological disorders, 383 physiological disorders, 382–3 chilling injury, 382 heat injury, 382–3 postharvest handling factors affecting quality, 380–2 atmosphere, 382 Crioula soursop weight loss, 381 physical damage, 381 temperature management, 380–1 water loss, 381 postharvest handling practices, 383–5 harvest operations, 383 packinghouse practices, 384 recommended storage and shipping conditions, 385 ripening and senescence control, 384–5 soursop fruit at harvest time, Plate XXXIV preharvest factors affecting fruit quality, 379–80 worldwide importance, 364–6 Annona seed borer see Bephratelloides cubensis Annona squamosa L., 399–422 control of ripening and senescence, 417–20 1-methylcyclopropene, 418 calcium carbide, 418–19 chemicals, 419–20 fruit firmness, 420 modified atmosphere, 417–18 respiration and ethylene production rates, 419

485

culinary uses, nutritional value and health benefits, 404–5 diseases, insect pests and their control, 414–15 mummified fruit, 414 fruit development and postharvest physiology, 405–8 fruit growth, development, maturation, 405 maturity, 408–10 origin, botany, morphology and structure, 399–403 cultivated sugar apples in some countries, 402 cultivated sugar apples in Thailand, 401 Golden Nang, Plate XXXV Green Fai, Plate XXXV(A) Green Nang, Plate XXXV(C) morphological characteristics of Fai and Nang, 401 production cycles in Thailand, 403 Purple Fai, Plate XXXV(B) Purple Nang, Plate XXXV(D) seedless, Plate XXXV(F) structures, 400 physiological disorders, 412–13 chilling injury, 412–13 other, 413 postharvest fruit blackening and tree fruit cracking, 413 postharvest handling factors affecting quality, 411–12 atmospheric conditions, 411–12 physical damage, 411 temperature management, 411 postharvest handling practices, 415–21 harvest operations and packinghouse practices, 415–17 recommended storage and shipping conditions, 420–1 sugar apple supplements in Thailand, 416 preharvest factors affecting fruit quality, 410–11 fruit bagging, 410–11 fruit setting and timing of harvest, 410 gibberellic acid application, 410 processing, 421–2 fresh-cut processing, 421 other practices, 421–2 respiration, ethylene production, and ripening, 405–8 aroma volatiles, 408

© Woodhead Publishing Limited, 2011

486

Index

fruit softening, 406–8 Nang and Fai respiration and ethylene production, 407 respiration and ethylene production, 405–6 worldwide importance and economic value, 403–4 anon see Chrysophyllum cainito L. anthocyanin, 277, 292, 319–20 anthracnose, 105, 259, 321, 358 antioxidants, 393 Aonidiella orientalis, 450 apha-mangostin, 4 Aphididae, 379 Aphis gossypii Glover, 137 Aspergillus flavus, 231, 233 Aspergillus parasiticus, 231, 232 Aspergillus spp., 302 asperuloside, 52 Aspidiotus spp., 450 Assaria pomegranate, 293 astringency, 167, 172, 178–80 atemoya see Annona cherimola Mill. × Annona squamosa L. attenuation coefficient, 160 aucubin, 52, 53 auto-catalytic ethylene production, 34 Aweta, 171 β-GAL see β-galactosidases β-galactosidases, 376–7 Bactrocera cucurbitae, 107 Bactrocera dorsalis, 107, 109, 183, 324 Bactrocera oleae, 72 basal rot, 259 benlate, 39, 358 benomyl, 39 benzaldehyde, 322 benzyl isothiocyanates, 95–6 benzylglucosinolates, 95 Bephratelloides cubensis, 415 Bephratelloides maculicollis Bondar, 379 betacyanins, 262, 265, 266 betalains, 261–2 Binjai rambutan, 314, 316 biocontrol agents, 323–4 black canker, 383 ‘black flag,’ 57 black rot, 206 black spots, 181–2, 231 blackheart, 204–5 body mass index (BMI), 227 boron fertilisation, 97–8

Botryodiplodia theobromae, 321 Botryodiplodia theobromae Pat., 414 Botryosphaeria dothidea, 71 Botrytis cinerea, 182–3 Botrytis cinerea Pers.: Fer., 301–2 Brazil, 127 Brazil-cherry see Eugenia uniflora L. bromelain, 200, 211 brown spot, 321 bullet, 135 Byrsonima crassifolia (L.) Kunth, 44–9 culinary uses, nutritional value and health benefits, 45–6 fruit development and postharvest physiology, 46–7 chemical composition of edible portion of fresh fruit, 46 growth, development and maturation, 46–7 growth curve for weight and diameter, 46 respiration, ethylene production and ripening, 47 insect pests and their control, 48 maturity and quality components and indices, 47 origin, botany, morphology and structure, 44–5 nance inflorescences, Plate V nance ripening fruits, Plate VI pathological disorders, 48 physiological disorders, 48 postharvest handling factors affecting quality, 48 postharvest handling practices, 48–9 preharvest factors affecting quality, 47 processing, 49 worldwide importance and economic value, 45 caboxin, 345 CAC/RCP 44–1995, 303 Cactus virus X, 259 caimito see Chrysophyllum cainito L. Calamus zalacca see Salacca zalacca (Gaertner) Voss calcium, 205 calcium carbide, 418–19 California-style black-ripe olives, 65, 72, 74–5, 77–8 canning, 78 curing in dilute brine, 77–8 loading, 77 lye removal, 77

© Woodhead Publishing Limited, 2011

Index lye treatment, 77 spoilage, 78 Calyx cavity, 174 cantaloupe, 35 caprilic acid, 52 caproic acid, 52 carbon dioxide, 70, 242 injury, 71 carbosulfan, 12 Carica papaya L., 86–118 fruit development and postharvest physiology, 90–6 biochemical changes during fruit ripening, 93–6 growth, development and maturation, 90–2 respiration and ethylene production, 92–3 maturity indices, 96 origin, botany, morphology and structure, 86–7 physiological disorders, 103–4 chilling injury, 103–4 soft fruit, 104 postharvest factors affecting fruit quality, 98–103 modified atmosphere packaging effect on ‘Red Lady’ papaya shelf-life, Plate XI physical damage, 99–100 storage atmosphere, 101–3 temperature management, 98–9 water loss, 100–1 postharvest handling practices, 111–14 exogenous application effect of ethylene on fruit ripening in ‘Red Lady’ papaya, Plate XII flow diagram, 112 harvest operations, 111 packinghouse practices, 111–13 recommended storage and shipping, 114 ripening and senescence control, 113–14 postharvest insect-pests and phytosanitary treatments, 107–11 heat treatment, 108–9 irradiation, 109–11 postharvest pathological disorders, 104–7 disease management, 106–7 preharvest factors affecting fruit quality, 96–8

487

processing, 114–16 fresh-cut, 114–16 other processed products, 116 uses, nutritional value and health benefits, 89–90 worldwide importance and economic value, 87–9 cultivars/hybrids grown in the different parts of the world, 89 geographical regions share to the global papaya production, 88 total area and production of the top-ten producing countries (2008), 88 carnauba-based wax, 100 carotenoid, 93, 277–8 Carya illinoiensis (Wangenh.) K. Koch., 143–62 current quality grading system, 152–4 colour, 153 halves and pieces size classification, 153 sizing, 153–4 harvesting, handling and storage, 147–52 early season harvest, 152 getting the nuts off the tree by shaking, Plate XIV immediate nut management, 151 in-shell pecans manual selection, sizing and grading, 150 kernels manual sorting and shells elimination, Plate XV manual collection, 149 mechanised harvest operations in a commercial pecan orchard, 148 nuts in a row ready for pick up, 149 nuts pick up and initial transport, 149–51 packing, 151–2 picking up of nuts and loading for transport to sorting facility, 150 preparation for processing, 151 shelling, 151 sizing and grading, 151 soil preparation, 147 tree shaking, 147–8, 149, 150 wind row formation, 148 in-shell and shelled pecans, 154–5 in-shell nuts, 154 shelled kernels, 154–5 main quality attributes, 155–6 nutritional value, 145–7 composition of the three most consumed nuts (USA), 146

© Woodhead Publishing Limited, 2011

488

Index

origin and distribution, 144 postharvest physiology factors affecting nut quality, 158–60 colour, 158 other disorders of postharvest influence, 160 pests and diseases, 159 rancidity, 158–9 respiration, 158 storage, 159 potential handling improvement, 160–1 processing minimal processing, 161 processed products, 161 production and consumption, 144–5 quality standards, 152–3 chemical, 152 microbiological, 152 physical contaminants, 153 storage, 156–7 appropriate temperature and humidity, 156–7 nut moisture content, 156 packaging materials, 157 Casimiroa edulis Llave & Lex, 474–80 culinary uses, nutritional value and health benefits, 475–7 nutrient value, 476 fruit development and postharvest physiology growth, development and maturation, 477 respiration, ethylene production and ripening, 477 insect pests and their control, 479 maturation and quality components and indices, 477–8 white sapote tree and fruit, Plate XLIII origin, botany, morphology and structure, 474–5 white sapote fruit, Plate XLIII pathological disorders, 479 physiological disorders, 478–9 chilling injury, 478–9 other physiological disorders, 479 postharvest handling factors affecting quality physical damage, 478 temperature management, 478 postharvest handling practices, 479–80 harvest operations, 479 packinghouse practices, 480 recommended storage and shipping conditions, 480

preharvest factors affecting fruit quality, 478 processing, 480 worldwide importance, 475 Castel-Vetrano processing, 75 cayenne-cherry see Eugenia uniflora L. Celebrex, 54 Cephaleuros virescens, 396 Ceratitis capitata, 107, 183, 324, 358 Cerconota anonella, 410 Cerconota anonella Sepp, 379 cereza de Cayena see Eugenia uniflora L. cerise de Cayenne see Eugenia uniflora L. changugu see Byrsonima crassifolia (L.) Kunth cheese fruit see Morinda citrifolia L. chi see Byrsonima crassifolia (L.) Kunth chico see Manilkara achras (Mill) Fosb., syn Achras sapota L. chico zapote see Manilkara achras (Mill) Fosb., syn Achras sapota L. chiku see Manilkara achras (Mill) Fosb., syn Achras sapota L. chilling injury atemoya, 412–13 respiration and ethylene production of African Pride atemoya, 412 fresh olives, 71 mangosteen, 14–17 melon, 38 papaya, 103–4, 114 symptoms, 98–9 passion fruit, 135 persimmon, 180–1, 185 levels range, Plate XVII pineapple, 204 pomegranate, 296–7, 299 rambutan, 319 salak, 344, 346 sapodilla, 357 soursop, 382 star apple, 396 sugar apple, 412–13 tamarillo, 434, 435 wax apple, 464–6 white sapote, 478–9 chinch see Tamarindus indica L. Chionaspis acuminata-atricolor, 450 2-chloroethyl phosphonic acid, 358 3-chlorophenoxyacetic acid (3-CPA), 202 Chrysophyllum cainito L., 392–7 culinary uses, 393–5 nutrient value, 394

© Woodhead Publishing Limited, 2011

Index fruit development and postharvest physiology colour parameters, 395 growth, development and maturation, 395 respiration, ethylene production and ripening, 395 insect pests and their control, 396 maturity and quality components and indices, 395 origin, botany, morphology and structure, 392–3 star apple fruit, Plate XLII pathological disorders, 396 physiological disorders, 396 postharvest handling factors affecting quality physical damage, 396 temperature management, 396 water loss, 396 postharvest handling practices control of ripening and senescence, 397 harvest operations, 397 packinghouse practices, 397 recommended storage and shipping conditions, 397 preharvest factors affecting fruit quality, 396 processing, 397 worldwide importance, 393 ciku see Manilkara achras (Mill) Fosb., syn Achras sapota L. cinnamaldehyde, 322 cinnamylalcohol dehydrogenase (CAD), 17 Cladosporium herbarum, 136 Cladosporium oxysporum, 136 Coccidae, 379 CODEX, 113 Codex Alimentarius (2007), 208 cold chain management, 327 Colletotrichum acutatum, 436 Colletotrichum gloeosporioides, 105, 107, 259, 321, 323, 358, 414, 436 Colletotrichum gloeosporioides Penz., 379 controlled atmosphere, 101, 176–7, 299, 300, 303, 304, 324, 326, 470 controlled temperature short duration (CTSD), 185 coronary heart disease (CHD), 227 craboo see Byrsonima crassifolia (L.) Kunth Cratosomus spp., 379 crazing, 174

489

Criola soursop, 382 Cryovac D-955, 100, 102, 104 cucumber mosaic virus, 136 Cucumis melo L., 31–42 botany, morphology and structure, 31–2 culinary uses, nutritional value and health benefits, 32–3 four major cucurbit crops, 32 fresh-cut processing, 42 fruit development and postharvest physiology, 33–5 climacteric rise in respiration and ethylene production, 34 growth, development and maturation, 33 respiration, ethylene production and ripening, 33–5 insect pests and their control, 39 major groups of melons, 33 maturation and quality components and indices, 35–6 cantaloupe commercial maturity, 35 honeydew commercial maturity, 35–6 packaging pattern of honeydew melons and chilling injury symptoms, Plate III pathological disorders, 39 physiological disorders, 38 chilling injury, 38 other physiological disorders, 38 postharvest handling factors affecting fruit quality, 36–8 atmosphere, 37–8 closed and open seed cavity, Plate IV physical damage, 37 temperature management, 36–7 water loss, 37 postharvest handling practices, 39–41 control of ripening and senescence, 40–1 harvest operations, 39 packinghouse practices, 40 postharvest harvesting and handling of melon fruit, 40 recommended storage and shipping conditions, 41 preharvest factors affecting fruit quality, 36 worldwide importance, 32 Curculio caryae (Horn), 159 curing, 64 curly top virus, 39 cyanidin- 3-glucoside, 8

© Woodhead Publishing Limited, 2011

490

Index

cyanidin-3-sophoroside, 8 Cymbopogon citratus, 136 DAA see days after anthesis Dacus dorsalis, 396 damnacanthal, 52, 53, 54 days after anthesis, 90–1, 131 days after full bloom (DAFB), 173 de novo biosynthesis, 93 Del Monte Corporation, 205 Delayed Light Emission method, 170 Diaporthe phaseolorum, 436 Diaspididae, 379 2,4-dichloro-phenoxy acetic acid, 358 dilly see Manilkara achras (Mill) Fosb., syn Achras sapota L. Diospyros kaki L., 166–87 atmosphere, 176–8 anoxic tolerance, 178 controlled atmosphere storage, 176–7 ethylene, 177–8 modified atmosphere storage, 177 culinary uses, nutritional value and health benefits, 167–8 fruit development and postharvest physiology, 168–70 cell wall metabolism and softening, 170 growth, development and maturation, 168–9 respiration, ethylene production and ripening, 169–70 insect-pests and their control, 183–4 fruit fly, 183–4 other insects, 184 passenger or ‘hitchhiker’ pests, 184 maturity, quality at harvest and phytonutrients, 170–2 maturity and quality at harvest, 170–1 phytonutrients, 171 taste, 172 origin, botany, morphology and structure, 166–7 New Zealand persimmon orchard in late autumn, plate XVI pathological disorders, 181–3 Alternaria, 181–2 Botrytis, 182–3 physiological disorders, 180–1 chilling injury, 180–1 chilling injury levels range in ‘Fuyu’ persimmons, plate XVII skin browning, 181 skin spotting, 181

postharvest handling factors affecting fruit quality, 175–80 astringency removal, 178–80 physical damage, 175 temperature management, 175 water loss, 175–6 weight loss, fruit shrivel and Alternaria decay development on ‘Triumph’ persimmons, 176 postharvest handling practices, 184–6 harvest operations, 184–5 packinghouse practices, 185 recommended storage and shipping conditions, 186 ripening and senescence control, 185–6 preharvest factors affecting postharvest fruit quality, 172–5 Calyx separation, 174 climate and environment, 173–4 minerals – nutrition, 172 plant growth regulators, 172–3 skin cracking/black blotch, 174–5 processing, 186–7 fresh-cut processing, 186–7 other processing practices, 187 worldwide importance and economic value, 167 Diplodia, 396 direct gas chromatography (GLC), 155 Dk-ERS1, 169–70 Dk-ERT2, 169–70 Dk-ETR1, 169–70 dry tank machine, 237 drying pistachio nut, 238–41 dryers characteristics, 239 drying pattern, 238 drying rate, 239 pressure drop, 240 E. costata Cambess. see Eugenia uniflora L. E. Micheli Lam see Eugenia uniflora L. edible film, 241 electron beam irradiation, 160 endo-PG see endo-polygalacturonase endo-polygalacturonase, 376 endogenous brown spots see blackheart English walnuts see Juglans regia L. Enterobacter aerogenes, 76 Escherichia coli, 76, 211 ethephon, 173

© Woodhead Publishing Limited, 2011

Index ethylene, 67, 92–3, 113, 135, 177–8, 197, 358, 435 production, 132 Eugenia uniflora L., 272–84 importance, economic value, culinary uses and health aspects, 273–4 maturity and quality components and composition, 276–8 origin, botany, morphology and structure, 272–3 purple pitanga, Plate XXV red pitanga, Plate XXIV postharvest handling factors affecting quality, 278–9 atmosphere, 279 temperature management, 278 postharvest handling practices, 279–80 harvest operations, 279 ripening and senescence control, 279–80 postharvest physiology, 274–6 purple pitanga maturation changes, 276 red pitanga maturation changes, 275 processing, 280–4 clarified pitanga juice flow sheet, 282 juice processing steps, 281 pitanga juice, 282–4 pitanga pulp, 280–2 pitanga tropical juice or nectar juice flow sheet, 283 exo-PG see exo-polygalacturonase exo-polygalacturonase, 376 Fai sugar apple, 400–1, 404 FAO see Food and Agriculture Organisation fertilisation, 97 fisheye spoilage, 72 flesh translucence, 205–6 Florida-cherry see Eugenia uniflora L. fludioxonil, 302 FMC-819, 100 FMC-820, 100 Food and Agriculture Organisation, 64, 222 forced air dry heat (FADH), 106 freezing, 421–2 fructose, 372 fruit bagging, 410–11 fruit blackening, 413 fruit cracking, 300–1, 410, 413, 466–7 fruit splitting, 410 fruit thinning, 97 fungicides, 321, 345

491

Fusarium monoliforme, 200 Fusarium oxysporum, 259 gamboge, 11, 21 Ganesh pomegranate, 304 Garcinia mangostana L., 1–25 fruit development and postharvest physiology, 4–10 anthocyanin profiles in outer pericarp, 8 changes during growth and development, 4 colour development, 6–10, Plate I fruit harvested at Stage 0, 5 growth, development and maturation, 4–5 respiration, ethylene production and ripening, 5–6 skin colour and total anthocyanin contents, 7 softening, 10 transient activation of mangosteen and Arabidopsis DFR promoter, 9 harvesting practices, 22 maturity and quality components, 10–11 time, quality and sensory evaluation of fruit harvested at Stage 1, 11 nutritional value and health benefits, 3–4 origin, botany, morphology and structure, 1–3 pathological disorders, 21–2 physiological disorders, 14–21 chilling injury, 14–17 firmness and lignin content of pericarp of dark purple mangosteen fruit, 18 gamboge, 21 PAL, CAD and POD activities in the pericarp, 19 pericarp hardening after impact, 17–20 translucent aril, 20–1 postharvest handling factors affecting quality, 12–14 atmosphere and coatings, 14 physical damage, 13 temperature management, 12–13 water loss, 13–14 postharvest operations, 22–3 control of ripening, 22–3 packinghouse practices, 22 storage recommendation, 23 preharvest factors affecting fruit quality, 11–12 fertiliser, 11–12

© Woodhead Publishing Limited, 2011

492

Index

location, 11 pests, 12 thrip-damaged fruit, Plate II processing, 23–5 drying, 24 freeze-dried and other products, 24–5 freezing, 24 fresh-cut, 23 juice, 24 paste, 24 worldwide importance, 3 generally recognised as safe (GRAS), 107 gibberellic acid, 358, 410 Gliocephalotrichum bulbilium, 321 Gliocephalotrichum microchlamydosporum, 321 Glomerella cingulata, 71, 436 glucose, 372 GmMYB, 8–9 GmMYB10, 9 gogu atoni see Morinda citrifolia L. golden cherry see Byrsonima crassifolia (L.) Kunth golden spoon see Byrsonima crassifolia (L.) Kunth goldenleaf tree see Chrysophyllum cainito L. goraka-jambo see Eugenia uniflora L. gouging, 209 gray mold, 301–2 great morinda see Morinda citrifolia L. Greek-style naturally ripe olives, 67, 80 green islands, 99, 112 guazatine, 39 gummosis, 21 heart rot, 302 heat injury, 382–3 heat treatment, 108–9, 421 Hicaznar pomegranate, 301, 304, 305 high temperature forced air (HTFA), 109 hog apple see Morinda citrifolia L. honeydews, 34, 35–6 hot air treatments, 260 hot water treatment, 322 hulling, 235–6 Hunter a value, 170 husk scald, 299 hybrid atemoya see Annona cherimola Mill. × Annona squamosa L. hydrolytic enzymes, 375–8

Hylocereus costaricensis (Web.) Britton & Rose, 249 hybrid, 251 plant and flowers, 255 Hylocereus megalanthus Bauer, 249 Hylocereus monocanthus Bauer, 250 Hylocereus ocamponis (Weing.) Britton & Rose, 250 Hylocereus spp., 247–67 botany, origin and morphology, 248–54 botany and genetic, 248–51 Hylocereus undatus and Hylocereus costaricensis hybrid, 251 Hylocereus undatus fruit, 250 morphology and reproductive biology, 252–4 origin, distribution and ecology, 252 peel and flesh colours, 249 cropping system, 254–5 Hylocereus trigonus in agroforest system, Plate XXIII cultivation techniques, 255–9 harvesting, 258–9 Hylocereus costaricensis plant and flowers, 255 multiplication and planting density, 255–6 nutrition and irrigation, 256–7 pollination, 257–8 practices, 256–7 weed management, 257 diversity, Plate XXII manual pollination, 259 pests and diseases, 259–60 ant damage on fruit, 259 postharvest handling factors affecting quality, 262–3 atmosphere, 263 temperature management, 262–3 water loss, 263 processing, 263–6 quality components and indices, 260–2 fruit pulp main physico-chemical composition, 260 uses and market, 248 Hylocereus undatus (Haw.) Britton & Rose, 250–1 fruit, 250 hybrid, 251 hypobaric storage, 101 imli see Tamarindus indica L. indano see Byrsonima crassifolia (L.) Kunth

© Woodhead Publishing Limited, 2011

Index Indian mulberry see Morinda citrifolia L. internal browning see blackheart International Olive Oil Council, 82 International Plant Protection Convention (IPPC), 110 irapua bee see Triogona spinips irradiation, 109–11 Jitlee rambutan, 314, 316, 327 ethylene production, 315 respiration rates, 315 jo ban see Morinda citrifolia L. Juglans regia L., 144 kernel colour, 155, 158 kernel size, 155 kesengel see Morinda citrifolia L. Lasiodiplodia theobromae (Pat), 379 Lasmenia sp., 321 LDPE see low density polyethylene leaf pruning, 96–7 Lebakbulus rambutan, 316 lignification, 15 lignin-carbohydrate complex (LCC), 17–18 lignins, 15 Listeria monocytogenes, 211 local salak see Salacca glaberescens low density polyethylene, 100 low O2 treatment, 16 Maconellicoccus hirsutus, 379 Macrospis festina, 48 Maharlika rambutan, 327 Maillard reaction, 242, 244 Malase-Yazdi pomegranate, 295 Malay apple see Syzygium malaccense Malaysian Red rambutan, 314, 316, 317, 327 Malaysian salak see Salacca glaberescens Malaysian Yellow rambutan, 314, 317, 327 malic acid, 373 Malwana Special Selection rambutan, 314, 316, 317, 322, 327 mangosteen see Garcinia mangostana L. Manilkara achras (Mill) Fosb., syn Achras sapota L., 351–60 culinary and other uses, nutritional value and health benefits, 352–3 nutrient value, 353 sapodilla fruit, Plate XXXII fruit development and postharvest physiology, 353–4

493

growth, development and maturation, 353–4 respiration, ethylene production and ripening, 354 insect pests and their control, 358 maturity and quality components and indices, 354–6 origin, botany, morphology and structure, 351–2 pathological disorders, 357–8 physiological disorders chilling injury, 357 postharvest handling factors affecting quality, 356–7 atmosphere, 357 physical damage, 356 temperature management, 356 water loss, 356 postharvest handling practices, 358–9 harvest operations, 358 packinghouse practices, 358 recommended storage and shipping conditions, 359 ripening and senescence control, 358–9 preharvest factors affecting fruit quality, 356 processing, 359–60 sapodilla tree and fruit, Plate XXXII worldwide importance and economic value, 352 manual pollination, 257 Hylocereus spp., 258 MAP see modified atmosphere packaging maricao see Byrsonima crassifolia (L.) Kunth maturity index, 276 MD-2, 205 Mediterranean fruit fly see Ceratitis capitata Meloidogynespp, 57 melon see Cucumis melo L. melon fly see Bactrocera cucurbitae Membracidae, 379 mengkudu see Morinda citrifolia L. methiocarb, 12 methyl bromide, 242 1-methylcyclopropene, 23, 93, 205, 418 Mexican fruit fly see Anastrepha ludens milking technique, 73 mites see Tetranychus urticae modified atmosphere, 177 modified atmosphere packaging, 100, 263, 298, 299, 303, 324, 326–7, 417–18, 435, 469–70

© Woodhead Publishing Limited, 2011

494

Index

Mollar de Elche pomegranates, 297, 302, 304 Mollar pomegranate, 293, 295, 296, 300, 304 mona see Morinda citrifolia L. monochrotophos, 12 monoecious, 87 Morada soursop, 369, 373, 374 Morinda citrifolia L., 51–9 chemical composition, 52–3 culinary uses, nutritional value and health benefits, 53–5 anti-cancer properties, 54 anti-inflammatory and other effects, 54–5 anti-microbial effects, 54 safety issue, 55 fruit growth, development and maturation, 55–6 noni fruit physical characteristics, 56 skin colour and firmness during noni fruit maturation and ripening, 56 insect pests and their control, 57 origin, botany, morphology and structure, 51–2 unpicked fruit, Plate VII pathological disorders, 57 postharvest handling practices, 57–8 harvest operations, 57–8 packaged noni fruit, 58 packinghouse practices, 58 recommended storage and shipping conditions, 58 preharvest conditions and postharvest handling factors affecting quality, 56 processing, 59 worldwide importance, 52 picked fruit in a market stall, Plate VIII morindin, 52 morindone, 52, 53 muricí see Byrsonima crassifolia (L.) Kunth Myrtus brasiliana L. see Eugenia uniflora L. Myzus persicae Sulz., 137 nailhead, 71, 76 nance see Byrsonima crassifolia (L.) Kunth nanche see Byrsonima crassifolia (L.) Kunth nanchi see Byrsonima crassifolia (L.) Kunth nanchite see Byrsonima crassifolia (L.) Kunth

nancite see Byrsonima crassifolia (L.) Kunth Nang sugar apple, 401, 404, 415 nasberry see Manilkara achras (Mill) Fosb., syn Achras sapota L. navel orangeworm see Aspergillus parasiticus Nephelium lappaceum L., 312–29 culinary uses, nutritional value and health benefits, 313 fruit development and postharvest physiology, 313–16 ethylene production, 315 growth, development and maturation, 313–14 panicles, Plate XXIX respiration, ethylene production and ripening, 314–16 respiration rates, 315 insect pests and their control, 324–5 quarantine treatments, 325 maturity and quality components and indices, 316–17 compositional changes, 316–17 physical indices, 316 origin, botany, morphology and structure, 312–13 fruit peel with hair-like spinterns and internal edible flesh, Plate XXVIII pathological disorders, 320–4 postharvest pathogens, 321 physiological disorders, 319–20 chilling injury, 319 pericarp browning, 319–20 postharvest disease control measures, 321–4 biocontrol agents, 323–4 chemical control, 321 hot water treatment, 322 integrated treatments, 324 sulphiting agents, 322–3 volatile compounds, 322 postharvest handling factors affecting quality, 317–19 atmosphere, 319 physical damage, 318 temperature management, 318 water loss, 318–19 postharvest handling practices, 325–8 cold-chain management, 327 harvest operations, 325 packinghouse practices, 325–6 recommended storage and shipping conditions, 328

© Woodhead Publishing Limited, 2011

Index preharvest factors affecting fruit quality, 317 processing fresh-cut processing, 328 other practices, 328 ripening and senescence control, 326–7 controlled atmosphere, 326 modified atmosphere packaging, 326–7 worldwide importance and economic value, 313 Nephopteryx engraphella Rag., 358 Nernwong, 339 Nipaecoccus viridis, 450 níspero see Manilkara achras (Mill) Fosb., syn Achras sapota L. non-splitting, 242 noni see Morinda citrifolia L. ‘Noni,’ 53 ‘Noni juice,’ 53, 59 nordamnacanthal, 53 Olea europaea L., 63–84 culinary uses, nutritional value and health benefits, 64–5 fruit development and postharvest physiology, 65–7 growth, development and maturation, 65–6 respiration, ethylene production and ripening, 66–7 respiration rates at different temperatures, 66 grades and standards, 80–3 canned table olives, 81–2 harvest operations, 72–5 bruising and cutting damage produced during mechanical olive harvest, Plate IX canopy contact head harvester in hedgerow olive orchard, 75 hand harvesting, 73 mechanical harvesting, 73–5 trunk shaking harvester in high density hedgerow orchard, Plate X insect pests and their control quarantine issues, 72 maturity, quality components and indices, 67–9 chemical components, 68–9 origin, botany, morphology and structure, 63 packinghouse handling practices, 75–80 California-style black-ripe olives, 77–8

495

Greek-style naturally ripe olives, 80 holding in brine, 76 holding in salt-free solution, 75–6 olives turning colour, 79 Spanish-style pickled green olives, 78–9 stuffed olives, 79–80 pathological disorders, 71–2 physiological disorders carbon dioxide injury, 71 chilling injury, 71 nailhead, 71 postharvest handling factors affecting quality, 70–1 atmosphere, 70–1 temperature management, 70 processing fresh-cut processing, 84 other processing techniques, 84 recommended storage and shipping conditions, 83 trade types qualitative classification, 82–3 first-class, 82 market-class, 83 standard-class, 82–3 worldwide importance and economic value, 63–4 ten largest olive producing countries, 64 olive see Olea europaea L. olive fruit fly see Bactrocera oleae olive oil, 64, 65, 84 Oncideres dejean, 48 ORAC method, 262 oriental fruit fly see Bactrocera dorsalis oriental yellow scale insect see Aonidiella orientalis Orthezia insignis, 48 oxidative enzymes, 375–8 paclobutrazol, 173 pain killer see Morinda citrifolia L. Panoctine, 39 papaya see Carica papaya L. parachlorophenoxyacetic acid (PCPA), 205 paraffin wax, 135 passiflin, 130 Passiflora edulis f. edulis, 125 Passiflora edulis f. flavicarpa, 125 Passiflora edulis Sim., 125–38 crop losses, 135–7 chilling injury, 135 insect pests and their control, 136–7 pathological disorders, 135–6

© Woodhead Publishing Limited, 2011

496

Index

culinary uses, nutritional value and health benefits, 128–30 purple and yellow passion fruit nutritional characteristics, 129 cultivars and genetic variability, 128 origin, botany, morphology and structure, 125–7 postharvest handling factors affecting quality, 133–5 controlled atmosphere storage, 135 ethylene, 135 handling and grading, 133–4 packaging, 134–5 temperature and relative humidity, 134 waxing, 135 postharvest physiology and quality, 132–3 respiration and ethylene production, 132 ripening, quality components and indices, 133 preharvest factors affecting fruit quality, 130–2 flowering and pollination, 130–1 growth, development and maturation, 131 maturity and harvest, 131–2 maturity index/colour scale for purple passion fruit, Plate XIII yellow passion fruit maturity stages, 132 processing, 137–8 worldwide importance and economic value, 127–8 passion fruit see Passiflora edulis Sim. passion fruit woodiness virus (PWV), 136 pasteurisation, 151 pawpaw see Carica papaya L. PCA see pollination constant astringent PCNA see pollination constant non-astringent Peakfresh, 327 Pebax-C, 100, 102 pecan see Carya illinoiensis (Wangenh.) K. Koch. pecan weevil see Curculio caryae (Horn) pectic substances, 375 pectin methylesterase, 376 Penicillium funiculosum, 200 Penicillium spp., 302 peralejo see Byrsonima crassifolia (L.) Kunth peralejo de sabana see Byrsonima crassifolia (L.) Kunth

perdejo see Byrsonima crassifolia (L.) Kunth pericarp browning, 319–20 pericarp hardening, 14–15 after impact, 17–20 peroxidase, 16–17, 200, 377–8 peroxide, 158 persimmon see Diospyros kaki L. Pestalotia, 396 Pestalotiopsis sp., 323 Pet Pakchong atemoya, 405, 410 phenolic compounds, 373 phenylalanine ammonia lyase (PAL), 15–16 Phoma exigua, 436 Phomopsis, 321, 323 Phomopsis anonacearum, 379 Phomopsis sp., 396 phosphine, 242 Phyllosticta sp., 396 Phytophthora morindae, 57 Phytophthora palmivora (Butler) infection, 357 pineapple see Ananas comosus L. Merr. Pineapple Research Institute of Hawaii, 205 pistachio see Pistacia vera L. Pistacia vera L., 218–44 botany, 219–20 kernel, skin, shell and hull, Plate XXI pistachio fruits grape-like clusters on a tree, Plate XX composition, nutritional value and health benefits, 225–7 dried pistachio nuts processing, 242–4 grading, 242 roasting procedures in a continuous nut roaster, 243 salting and roasting, 242–4 split separation from non-split pistachio nuts, 242 drying, 238–41 dryers characteristics, 239 pattern, 238 pressure drop, 240 rate, 239 nuts processing, 234–42 blank pistachio nuts separation, 237 dried nuts storage, 241–2 hulling, 235–6 trash and debris removal, 236–7 washing, 237 Ohadi from Iran and Kerman from USA amino acid profile, 226

© Woodhead Publishing Limited, 2011

Index chemical composition, 225 fatty acid profiles, 226 origin and history, 218–19 physical, mechanical and thermal properties, 227–8, 229–30 Ohadi variety, 229–30 three major perpendicular dimensions, 228 physiological disorders, 228, 231 postharvest handling practices, 232–4 harvest operations, 233 maturity criteria and harvest time, 232–3 postharvest storage, 234 postharvest pathology and mycotoxin contamination, 231–2 processing procedures dried pistachio nut, 236 freshly harvested pistachio nut, 235 uses, 222 varieties, 220–1 Iranian pistachio nut and kernel view, 221 worldwide importance and economic value, 222–4 Global, Iran and United States pistachio production (1970–2007), 223 leading global exporters (2006), 224 top global importers (2006), 224 pitahaya see Hylocereus spp. pitanga see Eugenia uniflora L. pitanga juice, 282–4 pitanga seeds, 278 Planococcus lilacinus, 450 Plinia rubra L. see Eugenia uniflora L. pollination constant astringent, 167 pollination constant non-astringent, 167 pollination variant non-astringent, 167 polychromatic X-ray imaging, 160 polyethylene bags, 358 polyethylene glycol (PEG), 242 polyethylene-paraffin wax, 100 polygalacturonase, 376 polyphenol oxidase, 200, 204–5, 377–8 polyphenols, 355 pomegranate see Punica granatum L. potassium, 205 PPO see polyphenol oxidase pressure drop, 240 Prinomerus anonicola Bondar, 379 pruning, 256 Prunus amygdalus Batsh, 144 Pseudocercospora cladosporioides, 71

497

Pseudococcus sp., 415 Puccinia thaliae, 479 pulp browning, 380 Punica granatum L., 287–307 culinary uses, nutritional value and health benefits, 291–2 fruit development and postharvest physiology, 292–4 growth, development and maturation, 292–3 respiration, ethylene production and ripening, 293–4 maturity and quality components and indices, 294–5 origin, botany, morphology and structure, 287–90 fruits at different sizes, 288 pomegranate arils, 289 pathological disorders, 301–2 physiological disorders, 299–301 chilling injury, 299 chilling injury symptoms, Plate XXVI fruit cracking damage, 300 husks scald symptom, Plate XXVII other physiological disorders, 299–301 sunburn damage, 301 postharvest handling factors affecting quality, 296–9 atmosphere, 298–9 physical damage, 297–8 temperature management, 296–7 water loss, 298 postharvest handling practices, 302–5 harvest operations, 302–3 packinghouse practices, 303 recommended storage and shipping conditions, 304–5 ripening and senescence control, 303–4 preharvest factors affecting fruit quality, 295–6 processing, 305–6 fresh-cut processing, 305–6 juice extraction, 306 worldwide importance and economic value, 290 top producing countries, 290 Puree, 116 purple passion fruit see Passiflora edulis f. edulis purple pitanga, 276 purple sugar apple, 404–5 PVNA see pollination variant non-astringent

© Woodhead Publishing Limited, 2011

498

Index

quarantine treatments, 325 Queen of Tropical Fruit see Garcinia mangostana L. R134 rambutan, 316 R156 rambutan, 316 R167 rambutan, 314, 315 Rakam see Salacca wallichiana Mart rambutan see Nephelium lappaceum L. rancidity, 158–9 red pitanga, 276 relative humidity, 127, 134, 151, 203 residual astringency, 172 RH see relative humidity Rhizopus stolonifer Soc., 379 root-knot disease, 57 rose apple see Syzygium jambos rubiadin, 53 rubiadin-1-methyl ether, 53 S. lucidius O. Berg see Eugenia uniflora L. Sabadilla, 12 Saccharomyces cerevisiae, 265 saffron, 243 Sala see Salacca rumphii Salacca edulis, 335, 342 Salacca glaberescens, 336 Salacca rumphii Wall, 334, 335 Salacca wallichiana Mart, 334, 335 Salacca zalacca (Gaertner) Voss, 334–48 culinary use, nutritional value and health benefits, 339–40 phytonutrients and minerals, 340 fruit development and postharvest physiology respiration and ethylene production during maturation, 341 origin, botany, morphology and structure, 334–8 Malaysian Salak physico-chemical characteristics, 336 sala and rakam, 335 salak clones physico-chemical characteristics, 337 Salak Pondoh and Salak Bali, 335 postharvest factors and physiological disorders affecting quality, 343–4 fruit drop and quality, 344 postharvest handling practices, 345–7 harvesting, cleaning and grading, 345–6 ripening and senescence control, 346 storage, 346–7

postharvest pathology and entomology, 344–5 preharvest factors affecting fruit quality, 343 processing, 347–8 fresh-cut processing, 347 other practices, 347–8 quality components during maturation, 341–3 ascorbic acid content, 343 firmness, 342 firmness, soluble solids concentration and titratable acidity, 342 mature and immature Rakam, Plate XXXI mature and immature salak pondoh, Plate XXX skin and flesh colours, 341 soluble solids concentration and titratable acidity, 342 volatile compounds, 343 worldwide importance and economic value, 338–9 production in Indonesia, 339 production in Thailand, 339 Salacca zalacca var. amboinensis, 335 salak see Salacca zalacca (Gaertner) Voss salak Bali see Salacca zalacca var. amboinensis Salak Bali cv Nangka, 346 salak cv. bongkok, 340 salak cv ‘Suwaru,’ 346 Salak Pondoh see Salacca edulis salicylic acid, 419 sapodilla see Manilkara achras (Mill) Fosb., syn Achras sapota L. sapodilla plum see Manilkara achras (Mill) Fosb., syn Achras sapota L. sapota see Manilkara achras (Mill) Fosb., syn Achras sapota L. sapota plum see Manilkara achras (Mill) Fosb., syn Achras sapota L. Saynampueng, 339 Scholar, 302 Sclerotium rolfsii, 57 scopoletin, 52, 53, 54, 55 Seechompoo rambutan, 314, 317 Seematjan rambutan, 316 Septoria passiflorae, 136 Shani-Yonay pomegranate, 301 shell splitting, 231 Sinclair, 171 skin blackening, 413 skin browning, 317–18

© Woodhead Publishing Limited, 2011

Index SmartFresh, 169, 180, 186 soft X-ray digital imaging, 160 Solanum betaceum (Cav.), 427–38 crop losses, 435–7 insect pests and their control, 437 pathological disorders, 436–7 culinary uses, nutritional value and health benefits, 429–31 nutritional characteristics, 430 cultivars and genetic variability, 429 origin, botany, morphology and structure, 427–8 physiological disorders, 435–6 calyx blackening, Plate XXXVII(D) calyx lifting, Plate XXXVII(C) chilling injury, 435 fruit stem and calyx deterioration, 435–6 healthy stem, Plate XXXVII(E) healthy tamarillo calyx, Plate XXXVII(A) other physiological disorders, 436 stem blackening, Plate XXXVII(G) stem yellowing, Plate XXXVII(F) postharvest handling factors affecting quality, 434–5 ethylene, 435 handling and grading, 434 modified and controlled atmosphere, 435 relative humidity, 435 special treatments, 435 temperature, 434–5 postharvest physiology and quality, 432–4 changes in colour parameters, 433 respiration and ethylene production, 432–3 ripening, quality components and indices, 433–4 preharvest factors affecting fruit quality, 431–2 flowering and pollination, 431 fruit growth, development and maturation, 432 processing, 437–8 worldwide importance and economic value, 429 soluble solids content, 91, 128, 371–2 sooty mold, 57 soursop see Annona muricata L. Spanish-style pickled green olives, 65, 67, 75, 78–9 fermentation, 79

499

lye treatment, 78–9 packing, 79 spinosad, 12 squash mosaic virus, 39 SSC see soluble solids content star apple see Chrysophyllum cainito L. stem-end rot, 321 stem spots, 259 stems necrotic lesions, 259 Stenocalyx Micheli (Lam) O. Berg see Eugenia uniflora L. sucrose, 372 sugar apple see Annona squamosa L. sulfur dioxide, 324 sulphiting agents, 322–3 sunburn, 301 super-fruit, 3 surinam-cherry see Eugenia uniflora L. sweetsop see Chrysophyllum cainito L. Syzygium aqueum, 458, 459 Syzygium jambos, 458–9 Syzygium malaccense, 458, 459 Syzygium samarangense (Blume) Merr. and L.M. Perry, 458–70 culinary uses, nutritional value and health benefits, 463 fruit development and postharvest physiology growth, development and maturation, 464 respiration, ethylene production and ripening, 464 insect pests and their control, 467 maturity, quality components and indices, 464 origin, botany, morphology and structure, 458–63 biology, 459 climates and soils, 460 cultivars, 460 evergreen and bald-cut training systems, 461 fertilisation, 462 flowering and fruiting, 459–60 fruit quality improvement, 462–3 off-season production, 462 origin and worldwide importance, 458–9 planting, 460 propagation, 460 training and pruning, 460–1 varieties, Plate XL wax apple tree with fruits, Plate XLI

© Woodhead Publishing Limited, 2011

500

Index

packinghouse practices grading, 469 packaging, 469 pathological disorders, 467, 468 effect of package with polyethylene bag, 468 physiological disorders, 464–7 changes in ethylene production, 465 changes in skin colour, 465 chilling injury, 464–6 cracking, 466–7 postharvest handling practices, 469–70 harvest operations, 469 recommended storage and shipping conditions, 469–70 controlled atmosphere storage, 470 low temperature storage, 469 modified atmosphere packaging, 469–70 worldwide importance, 463 TA see titratable acidity table olives, 65, 72–3 canned, 81–2 sizes, 81–2 styles, 81 trade types, 81 tamarillo see Solanum betaceum (Cav.) tamarillo mosaic potyvirus (TaMV), 429 tamarind see Tamarindus indica L. tamarinde see Tamarindus indica L. tamarindizio see Tamarindus indica L. tamarindo see Tamarindus indica L. Tamarindus indica L., 442–55 culinary uses, nutritional value and health benefits, 445–8 mineral content, 447 nutrition constituents, 446 diseases and pests and their control, 450–1 fruit growth and ripening growth, development and maturation, 448 respiration, ethylene production and ripening, 448 maturity and quality components and indices, 448 origin, botany, morphology and structure, 442–3 tamarind from Mexico, Plate XXXVIII tamarind pods, Plate XXXIX(B)

tamarind tree, Plate XXXIX(A) postharvest handling factors affecting quality physical damage, 451 temperature management, 451 water loss, 451 postharvest handling practices, 452–3 control of ripening and senescence, 453 harvest operations, 452 packinghouse practices, 452–3 recommended storage and shipping conditions, 453 preharvest factors affecting fruit quality, 449–50 rainfall, 449 soil, 449–50 temperature, 449 processing, 453–4 pulp, 453–4 seed, 454 worldwide importance and economic value, 444–5 area, production, export, and values of tamarind from India, 444 quantities and tonnes of tamarind from India, 444 tamarinier see Tamarindus indica L. tamrulhindi see Tamarindus indica L. tannin, 168, 170, 171, 292, 306 testa colour, 152 Tetranychus urticae, 137 Thai Rakam, 341 Thai Sala, 341, 342, 344 thermal processing, 437–8 thiabendazol, 209, 345 Thielaviopsis paradoxa, 202, 206, 209 thrips, 12 titratable acidity, 95, 131, 372–3 total soluble solids, 208, 260–1 traditional method, 254 translucent aril, 20–1 tree melon see Carica papaya L. Trichoderma harzianum, 323–4 Triogona spinips, 379 Trioza erytreae, 479 Trips spp., 136 Troclosene-Na, 182, 185 Trypetidae, 358 TSS see total soluble solids U.S. Department of Agriculture (USDA), 80, 108, 110

© Woodhead Publishing Limited, 2011

Index vapour heat (VH), 106, 108 variant pollination, 167 Vaseline, 168 Vinipel film wrap, 134 vitamin E, 227 water apple see Syzygium aqueum wax apple see Syzygium samarangense (Blume) Merr. and L.M. Perry weed management, 257 white sapote see Casimiroa edulis Llave & Lex ‘winter’ melons, 34, 36

501

‘Wonderful’ pomegranates, 288, 293–4, 298, 304 woodiness, 135–6 XAD7, 265 xeronine, 52 yellow passion fruit see Passiflora edulis f. flavicarpa Zapatera spoilage, 72 zapote see Manilkara achras (Mill) Fosb., syn Achras sapota L.

© Woodhead Publishing Limited, 2011