Vegetable Oils in Food Technology: Composition, Properties and Uses

Vegetable Oils in Food Technology Composition, Properties and Uses Second Edition Edited by Frank D. Gunstone A John W...

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Vegetable Oils in Food Technology Composition, Properties and Uses Second Edition Edited by

Frank D. Gunstone

A John Wiley & Sons, Ltd., Publication

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This edition first published 2011 © 2011 by Blackwell Publishing Ltd. Blackwell Publishing was acquired by John Wiley & Sons in February 2007. Blackwell’s publishing program has been merged with Wiley’s global Scientific, Technical and Medical business to form Wiley-Blackwell. Registered Office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial Offices 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 2121 State Avenue, Ames, Iowa 50014-8300, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell. The right of the authors to be identified as the authors of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Vegetable oils in food technology : composition, properties and uses / edited by Frank D. Gunstone. – 2nd ed. p. cm. Includes bibliographical references and index. ISBN 978-1-4443-3268-1 (hardcover : alk. paper) 1. Vegetable oils. 2. Food industry and trade. I. Gunstone, Frank D. TP680.V44 2011 664′.3–dc22 2010041148 A catalogue record for this book is available from the British Library. This book is published in the following electronic formats: ePDF 9781444339901; Wiley Online Library 9781444339925; ePub 9781444339918 Set in 10/12pt Times by SPi Publisher Services, Pondicherry, India

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2011

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Contents

Preface to the First Edition Preface to the Second Edition Contributors List of Abbreviations 1 Production and Trade of Vegetable Oils Frank D. Gunstone 1.1 Extraction, refining and processing 1.2 Vegetable oils: Production, consumption and trade 1.2.1 Nine vegetable oils 1.2.2 Palm oil 1.2.3 Soybean oil 1.2.4 Rapeseed/canola oil 1.2.5 Sunflowerseed oil 1.2.6 Groundnut (peanut) oil 1.2.7 Cottonseed oil 1.2.8 Coconut oil 1.2.9 Palmkernel oil 1.2.10 Olive oil 1.2.11 Corn oil 1.2.12 Sesame oil 1.2.13 Linseed oil 1.3 Some topical issues 1.3.1 Imports into China and India 1.3.2 Trade in oilseeds and in vegetable oils 1.3.3 Food and non-food use of vegetable oils 1.3.4 Prices 1.3.5 The food–fuel debate 1.3.6 Predictions for future supply and demand 1.3.7 Sustainability 1.3.8 Genetic modification References 2 Palm Oil Siew Wai Lin 2.1 Introduction 2.2 Composition and properties of palm oil and fractions

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2.2.1 Palm oil 2.2.2 Palm olein 2.2.3 Palm stearin 2.3 Physical characteristics of palm oil products 2.3.1 Palm oil 2.3.2 Palm olein 2.3.3 Palm stearin 2.4 Minor components of palm oil products 2.4.1 Carotenes 2.4.2 Tocopherols and tocotrienols (tocols) 2.4.3 Sterols, squalene and other hydrocarbons 2.5 Food applications of palm oil products 2.5.1 Cooking/frying oil 2.5.2 Margarines 2.5.3 Shortenings 2.5.4 Vanaspati 2.5.5 Cocoa butter equivalents (CBE) 2.5.6 Other uses 2.6 Nutritional aspects of palm oil 2.7 Sustainable palm oil 2.8 Conclusions References 3 Soybean Oil Tong Wang 3.1 Introduction 3.2 Composition of soybean and soybean oil 3.2.1 Seed composition 3.2.2 Oil composition 3.2.3 Fatty acid composition 3.2.4 Minor components 3.3 Recovery and refining of soybean oil 3.3.1 Oil extraction 3.3.2 Oil refining 3.3.3 Modified non-alkaline refining 3.3.4 Co-products from oil refining 3.3.5 Fatty acid esters of glycidol and 3-monochloro-1,2-propanediol as processing contaminants 3.4 Oil composition modification by processing and biotechnology 3.4.1 Hydrogenation 3.4.2 Interesterification 3.4.3 Crystallization and fractionation 3.4.4 Traditional plant breeding and genetic modification 3.4.5 Oxidative and sensory properties of low-linolenic acid soybean oil to replace trans frying oil 3.5 Physical properties of soybean oil 3.5.1 Polymorphism

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3.5.2 Density 3.5.3 Viscosity 3.5.4 Refractive index 3.5.5 Specific heat 3.5.6 Melting point 3.5.7 Heat of combustion 3.5.8 Smoke, flash, and fire points 3.5.9 Solubility 3.5.10 Plasticity and spreadability 3.5.11 Electrical resistivity 3.6 Oxidation evaluation of soybean oil 3.7 Nutritional properties of soybean oil 3.8 Food uses of soybean oil 3.8.1 Cooking and salad oils 3.8.2 Margarine and shortening 3.8.3 Mayonnaise and salad dressing References 4 Canola/Rapeseed Oil Roman Przybylski 4.1 Introduction 4.2 Composition 4.2.1 Nature of edible oils and fats 4.2.2 Fatty acid composition of canola oil 4.2.3 Minor fatty acids 4.2.4 Triacylglycerols 4.2.5 Polar lipids 4.2.6 Tocopherols 4.2.7 Sterols 4.2.8 Pigments 4.2.9 Trace elements 4.2.10 Commercial crude oil, refined, and deodorized oil 4.2.11 Oxidative stability 4.3 Physical and chemical properties 4.3.1 Relative density 4.3.2 Viscosity 4.3.3 Smoke and flash point 4.3.4 Cold test 4.3.5 Crismer value 4.3.6 Saponification number 4.3.7 Iodine value 4.3.8 Melting characteristics, polymorphism, and crystal properties 4.4 Major food uses 4.4.1 Standard canola/rapeseed oil 4.4.2 High-erucic acid rapeseed (HEAR) oil 4.5 Conclusion and outlook References

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88 88 89 89 90 90 90 91 91 91 92 93 95 95 96 97 98 107 107 108 108 109 110 111 113 115 116 118 119 119 120 121 121 122 122 122 122 122 123 123 123 123 132 133 133

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5 Sunflower Oil Maria A. Grompone 5.1 Introduction 5.2 Sunflower oil from different types of seed 5.2.1 Regular sunflower seeds 5.2.2 Commercial sunflower oil types 5.2.3 Composition of commercially available sunflower oil types 5.2.4 Other sunflower seed types to be commercialised 5.3 Physical and chemical properties 5.3.1 Relative density 5.3.2 Viscosity 5.3.3 Refractive index 5.3.4 Smoke point, flash point and fire point 5.3.5 Other physical properties 5.4 Melting properties and thermal behaviour 5.4.1 Melting properties of regular sunflower oil 5.4.2 Thermal behaviour of different sunflower oil types 5.5 Extraction and processing of sunflower oil 5.5.1 Preparation of sunflower seeds for extraction 5.5.2 Sunflower oil extraction 5.5.3 Processing of crude sunflower oil 5.6 Modified properties of sunflower oil 5.6.1 Hydrogenation of regular sunflower oil 5.6.2 Interesterification of sunflower oil 5.7 Oxidative stability of commercial sunflower oils 5.7.1 Inherent stability of different commercial sunflower oil types 5.7.2 Shelf-life of sunflower oil 5.7.3 Accelerated ageing of sunflower oil 5.7.4 Stabilisation of sunflower oil by added antioxidants 5.8 Food uses of different sunflower oil types 5.8.1 Use of regular sunflower oil as salad oil and cooking oil 5.8.2 Margarine and shortening 5.9 Frying use of commercial sunflower oil types 5.9.1 Frying use of regular sunflower oil 5.9.2 Frying use of high-oleic sunflower oil 5.9.3 Frying use of mid-oleic sunflower oil 5.9.4 Frying use of sunflower oils with a high content of saturated fatty acids Acknowledgement References 6 The Lauric (Coconut and Palm Kernel) Oils Ibrahim Nuzul Amri 6.1 Introduction 6.2 Coconut oil 6.2.1 Coconut palm

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6.2.2 Coconut oil 6.2.3 Composition 6.2.4 Properties 6.2.5 Trade specifications 6.3 Palm kernel oil 6.3.1 Palm kernel oil 6.3.2 Composition 6.3.3 Properties 6.3.4 Trade specifications 6.4 Processing 6.4.1 Fractionation 6.4.2 Hydrogenation 6.4.3 Interesterification 6.5 Food uses 6.5.1 Frying 6.5.2 Margarine 6.5.3 Medium-chain triacylglycerols 6.5.4 Speciality fats: Cocoa butter substitutes 6.5.5 Filling creams 6.5.6 Non-dairy creamer 6.5.7 Non-dairy whipping cream 6.5.8 Non-dairy cheese 6.5.9 Filled milk 6.5.10 Ice cream 6.5.11 Toffees and caramels 6.6 Health aspects References 7 Cottonseed Oil Michael K. Dowd 7.1 7.2 7.3 7.4

Introduction History Seed composition Oil composition 7.4.1 Triacylglycerol fatty acids 7.4.2 Other oil components 7.4.3 Gossypol 7.5 Chemical and physical properties of cottonseed oil 7.6 Processing 7.6.1 Seed preparation 7.6.2 Oil extraction 7.6.3 Oil finishing 7.6.4 Additional processing 7.7 Cottonseed oil uses 7.8 Co-product uses References

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170 171 175 177 178 178 179 183 185 185 185 187 188 190 190 190 191 192 192 192 193 193 193 193 194 194 194 199 199 200 203 204 205 208 211 213 216 216 217 218 219 219 220 221

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8 Groundnut (Peanut) Oil Lisa L. Dean, Jack P. Davis, and Timothy H. Sanders 8.1 Peanut production, history, and oil extraction 8.2 Oil uses 8.2.1 Frying and food 8.2.2 Feed 8.3 Composition of groundnut oil 8.3.1 Oil in seed 8.3.2 Fatty acids 8.3.3 High-oleic peanut oil 8.3.4 Triacylglycerol structure 8.3.5 Phospholipids 8.3.6 Sterols 8.3.7 Antioxidants 8.4 Chemical and physical characteristics of groundnut oil 8.4.1 General 8.4.2 Color 8.4.3 Density and viscosity 8.4.4 Melting point/crystallization 8.4.5 Free fatty acid (FFA) 8.4.6 Iodine value (IV) 8.4.7 Peroxide value 8.4.8 Acetyl value 8.4.9 Heat of fusion 8.4.10 Unsaponifiable material 8.5 Health issues 8.5.1 Cardiovascular disease and diabetes 8.5.2 Weight control 8.5.3 Allergy Note References 9 Olive Oil Dimitrios Boskou 9.1 Introduction 9.2 Extraction of olive oil from olives 9.2.1 Pressure 9.2.2 Centrifugation (three-phase system) 9.2.3 Two-phase decanters 9.2.4 Percolation (selective filtration) 9.2.5 Processing aids 9.2.6 Extraction of pomace oil (olive residue oil) 9.3 Olive oil composition 9.3.1 Fatty acids and triacylglycerols 9.3.2 Mono- and di-acylglycerols 9.3.3 Other constituents

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Contents

9.4

Effect of processing olives on the composition of virgin olive oils 9.4.1 Aroma compounds 9.4.2 Polyphenols 9.4.3 Other minor constituents 9.5 Refining and modification 9.5.1 Olive oil and olive pomace oil refining 9.5.2 Refining and minor constituents 9.6 Hardening and interesterification 9.7 Quality, genuineness and regulations 9.7.1 Olive oil 9.7.2 Analysis and authentication 9.8 Consumption and culinary applications 9.8.1 Olive oil in frying References 10 Corn Oil Robert A. Moreau 10.1 Composition of corn oil 10.1.1 Introduction: The corn oil industry 10.1.2 Common corn oil refining steps and effects on oil composition 10.1.3 The composition of crude corn oils – comparison of corn germ oil, corn kernel oil, and corn fiber oil 10.1.4 Fatty acid composition of corn triacylglycerols 10.1.5 Triacylglycerol molecular species 10.1.6 Unsaponifiables and phytosterols 10.1.7 Tocopherols and tocotrienols 10.1.8 Carotenoids 10.1.9 Trans fatty acids 10.2 Properties of corn oil 10.2.1 Chemical and physical properties 10.2.2 Stability 10.2.3 Nutritional properties 10.3 Major food uses of corn oil 10.3.1 Cooking/salad oil 10.3.2 Margarines and spreads 10.4 Conclusions References 11 Minor and Speciality Oils S. Prakash Kochhar 11.1 Introduction 11.2 Sesame seed oil 11.2.1 World seed production 11.2.2 Lipid composition 11.2.3 Seed processing and oil refining

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11.2.4 Sesame antioxidants and oil stability 11.2.5 Health-promoting effects 11.3 Rice bran oil 11.3.1 Production of bran and oil extraction 11.3.2 Oil refining and high-value by-products 11.3.3 Lipid composition and food uses 11.3.4 Potential health benefits and future trends 11.4 Flaxseed (linseed and linola) oil 11.4.1 Flax production and oil composition 11.4.2 Edible uses of flaxseed and its oil 11.4.3 Linola oil 11.5 Safflower oil 11.6 Argan kernel oil 11.7 Avocado oil 11.8 Camelina seed oil 11.9 Grape seed oil 11.10 Pumpkin seed oil 11.11 Sea buckthorn oil 11.12 Cocoa butter and CBE 11.12.1 Cocoa butter 11.12.2 Illipe butter (Borneo tallow) 11.12.3 Kokum butter 11.12.4 Sal fat 11.12.5 Shea butter 11.12.6 Mango kernel fat 11.13 Oils containing γ-linolenic acid (GLA) and stearidonic acid (SDA) 11.13.1 Evening primrose oil 11.13.2 Borage oil 11.13.3 Blackcurrant seed oil 11.13.4 Stearidonic acid oils 11.13.5 Nutritional and health benefits of GLA and SDA oils 11.14 Tree nut oils 11.14.1 Brazil nut kernel oil 11.14.2 Hazel nut oil 11.14.3 Macadamia nut oil 11.14.4 Walnut oil 11.14.5 Health benefits of nuts and nut lipids References

297 298 299 299 301 303 305 306 306 308 309 309 313 315 315 317 319 320 321 321 322 322 322 323 324 324 324 325 326 326 327 327 328 328 329 331 331 331

Useful Websites

343

Index

347

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Preface to the First Edition

Our dietary intake comprises three macronutrients (protein, carbohydrate and lipid) and a large but unknown number of micronutrients (vitamins, minerals, antioxidants etc.). Good health rests, in part, on an adequate and balanced supply of these components. This book is concerned with the major sources of lipids and the micronutrients that they contain. Supplies and consumption of oils and fats are generally described in terms of seventeen commodity oils, four of which are of animal origin and the remainder of which are derived from plants. This selection of oils does not include cocoa butter, with an annual production of around 1.7 million tonnes, which is used almost entirely for the purpose of making chocolate. Nor does it include oils consumed in the form of nuts. The production and trade data that are available and are detailed in the first chapter relate to crops either grown and harvested for the oils that they contain (e.g. rape and sunflower oils) or crops that contain oils as significant by-products (e.g. cottonseed and corn oils). Annual production and consumption of oils and fats is about 119 million tonnes and rising steadily at a rate of 2–6 million tonnes per year. This is required to meet the demand, which also grows at around this rate, partly as a consequence of increasing population but more because of increasing income, especially in developing countries. Around 14% of current oil and fat production is used as starting material for the oleochemical industry and around 6% is used as animal feed (and indirectly therefore as human food). The remaining 80% is used for human food – as spreads, frying oil, salad oils, cooking fat etc. These facts provide the framework for this book. After the first chapter on production and trade, there follow ten chapters covering thirteen oils. The four dominant oils are discussed first: soybean, palm, rape/canola and sunflower. These are followed by chapters on two lauric oils (coconut and palmkernel), cottonseed oil, groundnut (peanut) oil, olive oil, corn oil and three minor but interesting oils (sesame, rice bran and flaxseed). The authors – from Europe, Asia and North America – were invited to cover the following topics: the native oils in their original form and in modified forms resulting from partial hydrogenation, fractionation or interesterification, and related oils produced by conventional seed breeding and/or genetic modification. For each of these, information is provided on component triacylglycerols, fatty acids, minor components (phospholipids, sterols, tocols, carotenoids etc.) and their major food uses. The book will serve as a rich source of data on these oils and the important minor components that they contain. It should therefore be of special value to food producers requiring up-to-date information on their raw materials, which will probably already have been processed, at least in part. The editor thanks the authors for their efforts to convert his concept into a reality and for their patience and willing cooperation, and he acknowledges the generous help and advice that he has received from the publisher, Dr Graeme MacKintosh and his colleagues. Frank D. Gunstone

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Preface to the Second Edition

It is nine years since the first edition of this book was published. The success of this led to the idea that we should produce a second, updated and extended edition. Each revised chapter has new information that has been published since 2002 and the final chapter has been extended to cover the more important minor seed oils. As in the first edition, there is an emphasis on data for both the major and minor components present in each oil. Significant changes in the last nine years have been the development of seeds producing oils with a different fatty acid composition based on current nutritional views. For example, there are more high-oleic varieties of several oils. Current views on the nutritional properties of trans acids and the requirement in some countries to report these on food labels have had an influence on avoiding partial hydrogenation and finding alternative ways of producing oils and fats with the required nutritional and physical properties. In the years between 2001/02 and 2008/09, production of the nine major vegetable oils rose 42% from 93 to 132 million tonnes. In this period there was an increased use for nonfood purposes and consequent pressure on the supplies required to meet the food needs of a population growing in number and in disposable income. While many of the chapters have been revised by the original authors, new authors were found for three of the chapters. I am indebted to all the authors for their efforts and for their patience with the editor. I also acknowledge the assistance provided by David McDade and his colleagues at Wiley-Blackwell. Frank D. Gunstone

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Contributors

Dr Dimitrios Boskou Laboratory of Food Chemistry and Technology School of Chemistry Aristotle University of Thessaloniki University Campus, Thessaloniki 54124 Greece Dr Jack P. Davis United States Department of Agriculture Agricultural Research Service Market Quality and Handling Research Unit Box 7624, North Carolina State University Raleigh, NC 27695-7624 USA Dr Lisa L. Dean United States Department of Agriculture Agricultural Research Service Market Quality and Handling Research Unit Box 7624, North Carolina State University Raleigh, NC 27695-7624 USA Dr Michael K. Dowd USDA ARS SRRC 1100 Robert E Lee Blvd New Orleans, LA 70124-4305 USA Professor Maria A. Grompone Av General Flores 2124 Montevideo 11800 Uruguay

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Professor Frank D. Gunstone 3 Dempster Court St Andrews Fife KY16 9EU Scotland Dr Ibrahim Nuzul Amri Malaysian Palm Oil Board 6 Persiaran Institusi 43000 Kajang, Selangor Malaysia Dr S. Prakash Kochhar SPK Consultancy Services 14 Holmemoor Drive Sonning Reading RG4 6TE UK Dr Siew Wai Lin Malaysian Palm Oil Board 6 Persiaran Institusi, 43000 Kajang, Selangor Malaysia Dr Robert A. Moreau Eastern Regional Research Center, United States Department of Agriculture, Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, Pennsylvania USA Professor Roman Przybylski University of Lethbridge Department of Chemistry and Biochemistry Lethbridge, Alberta Canada T1K 3M4

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Contributors

Dr Timothy H. Sanders United States Department of Agriculture Agricultural Research Service Market Quality and Handling Research Unit Box 7624, North Carolina State University Raleigh, NC 27695-7624 USA

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Professor Tong Wang Department of Food Science and Human Nutrition 2312 Food Sciences Building Iowa State University Ames, Iowa 50011-1061 USA

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List of Abbreviations

ABTS ALA AMF AOCS AOM AP B BCO BF BfR BHA BHT BNO BO CAE CAN cp CB CBE CBI CBR CHD CLA CLnA CO CPKO CPO CVD DAF DAG DGDG DHA DMPS DNA DOBI DPPH DSC EDTA

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2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) alpha-linolenic acid (18:3n-3, all cis) anhydrous milk fat American Oil Chemists’ Society active oxygen method ascorbyl palmitate behenic acid blackcurrant oil butterfat Federal Institute for Risk Assessment butylated hydroxyanisole butylated hydroxytoluene Brazil nut oil borage oil caffeic acid equivalent canola oil Centipoise cocoa butter cocoa butter equivalent cocoa butter improver coca butter replacement cardiovascular heart disease or coronary heart disease conjugated linoleic acid conjugated linolenic acid (18:3) coconut oil crude palm kernel oil crude palm oil cardiovascular disease days after flowering diacylglycerol(s) digalactosyl diglyceride docosahexenoic acid dimethylpolysiloxane deoxyribonucleic acid deterioration of bleachability index 1,1-diphenyl-2-picrylhydrazyl differential scanning calorimetery ethylenediaminetetraacetic acid

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List of Abbreviations

EPA EPO EU EU-27 FA FAC FAO FAS FDA FFA FFB FHSBO GC GE GG GHG GLA GLC GLCO GM HDL HEAR HLaCO HNO HO HOCO HOLLCO HOLLSOY HOSO HOSUN HP HL HP HO HPKS HPLC HPO HPOo HS HL HS HO HS HP HSCO HYDCO HYDSOY ICCA IEPO IOOC ISO IV L

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eicosapentaenoic acid; or Environmental Protection Agency evening primrose oil European Union 27 countries of the European Union fatty acid fatty acid composition Food and Agriculture Organisation Foreign Agricultural Service Food and Drug Administration (US) free fatty acids fresh fruit bunch fully hydrogenated soybean oil gas chromatography glycidol fatty acid esters galactosyl glycerol greenhouse gas(es) gamma-linolenic acid (18:3n-6, all cis) gas liquid chromatography gamma linolenic canola oil genetically modified or genetic modification high-density lipoprotein(s) high-erucic rapeseed oil high-lauric canola oil hazelnut oil high-oleic oil high-oleic canola oil high-oleic low-linolenic canola oil high-oleic low-linolenic soybean oil high-oleic sunflower oil high oleic sunflower oil high-palmitic/high-linoleic sunflower oil high-palmitic/high-oleic sunflower oil hydrogenated palm kernel stearin high-performance liquid chromatography hydrogenated palm oil hydrogenated palm olein high-stearic/high-linoleic sunflower oil high-stearic/high-oleic sunflower oil high-stearic/high-palmitic sunflower oil high-stearic canola oil hydrogenated canola oil hydrogenated soybean oil Interstate Cottonseed Crushers Association interesterified palm oil International Olive Oil Council International Standard Organisation iodine value linoleic acid

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List of Abbreviations

LCA LCPUFA LDL LEAR LFRA LLCO Ln LPC LPE M&I MAG MCF-7 MCFA MCPD MEOMA MGDG MNO MO MOSUN MPOB MPP MT mt MUFA NCPA NCVT NESHAP NSA NMR ND nr O O/L OOO OSI P PA PBSY PC PCR PDG PDI PDO PE PET PFAD PG PHSBO

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life-cycle analysis long-chain polyunsaturated fatty acids low-density lipoprotein low-erucic rapeseed oil Leatherhead Food Research Association (UK) low-linolenic canola oil linolenic acid lysophosphatidylcholines lysophosphatidylethanolamines moisture and impurities monoacylglycerol(s) human breast cancer cell line medium-chain fatty acid 3-monochloro-1,2-propanediol Malayan Edible Oil Manufacturers’ Association monogalactosyl diglycerol macadamia nut oil mid-oleic oil medium-oleic sunflower oil Malaysian Palm Oil Board dipalmitoyl myristoyl glycerol metric ton (tonne, 1000 Kg) million tonnes monounsaturated fatty acids National Cottonseed Products Association National Cotton Variety Trials National Emission Standards for Hazardous Air Pollutants National Sunflower Association (US) nuclear magnetic resonance non detectable not recorded oleic acid ratio of oleic acid to linoleic acid oleic-oleic-oleic triacylglycerol (triolein) oxidative stability index palmitic phosphatidic acids prime bleachable summer yellow (grade of cottonseed oil) phosphatidylcholines polymerase chain reaction palm diacylglycerols protein dispersibility index Protected Designations of Origin phosphatidylethanolamines polyethylene terephthalate palm fatty acid distillate phosphatidylglycerols; or propyl gallate partially hydrogenated soybean oil

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List of Abbreviations

PI PKO PKOo PKS PL PMF PO POME POO POo POP POs ppm PPP PPSt PS PV RBD RI RNAi RSO S SBDD SBO SCPA SDA SEP SFI SfMF SFO SG SMP snsn-1, sn-2 and sn-3 SOO SOS SPC SPI SSS St StOO StOSt SUS SUU SV TAG TBARS

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phosphatidylinositols palm kernel oil palm kernel olein palm kernel stearin phospholipids palm mid-fraction palm oil palm oil mill effluent dioleo palmitoyl glycerol (includes OPO isomer) palm olein dipalmitoyl oleoyl glycerol (includes PPO isomer) palm stearin parts per million (mg/kg) tripalmitoyl glycerol (triplamitin) dipalmitoyl stearoyl glycerol phosphatidylserines peroxide value refined, bleached and deodorised refractive index RNA interference (genetic technique used to interrupt the normal translation of mRNA molecules) rapeseed oil stearic; or saturated (type of fatty acid) soybean deodorizer distillate soybean oil Society of Cotton Products Analysts stearidonic acid (18:4n-3, all-cis) sequential extraction process solid fat index soft milkfat fraction sunflower oil esterified phytosterol glycoside; or specific gravity slip melting point stereospecific or regiospecific numbering positions of the glycerol backbone stearic-oleic-oleic triacylglycerol stearic-oleic-stearic triacylglycerol soy protein concentrates soy protein isolate trisaturated acyglycerols or trisaturates stearic acid stearic-oleic-oleic triacylglycerol stearic-oleic-stearic triacylglycerol disaturated monounsaturated acylglycerols diunsaturated monosaturated acylglycerols saponification value triacylglycerol(s) thiobarbituric acid-reactive substances

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List of Abbreviations

TBHQ TIU TRF tr U US USDA USDA–NASS VCO WHO WNO wt

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tertiary-butylhydroquinone trypsin inhibitor unit tocotrienol rich fraction trace unsaturated (type of fatty acid) unsaponifiable matter United States Department of Agriculture United State Department of Agriculture – National Agricultural Statistics Service virgin coconut oil World Health Organisation walnut oil weight

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1

Production and Trade of Vegetable Oils

Frank D. Gunstone

1.1 EXTRACTION, REFINING AND PROCESSING Most vegetable oils are obtained from beans or seeds, which generally furnish two valuable commodities: a fatty oil and a protein-rich meal. Seed extraction is achieved by pressing and/or by extraction with hexane. Oils such as palm and olive, on the other hand, are pressed out of the soft fruit (endosperm). Seeds give oils in differing proportions. Using USDA figures for 2008/09, world average oil yields are: soybean (18%), rapeseed (39%), sunflower (41%), groundnut (32%), cottonseed (14%), coconut (62%) and palmkernel (44%). In addition, yields from palm fruit (45–50%), olive (25–30%) and corn (about 5%) are as indicated. The relatively low yield of oil from soybeans is compensated for by the value of the highquality protein meal (79%) accompanying the oil. Some oils, such as virgin olive oil, are used without further treatment other than filtering, but most are refined in some measure before use. The refining processes remove undesirable materials (phospholipids, monoacylglycerols, diacylglycerols, free acids, colour and pigments, oxidised materials, flavour components, trace metals, sulphur compounds and pollutants), but may also remove valuable minor components, including antioxidants and vitamins such as carotenes and tocopherols. The refining processes must therefore be designed to maximise the removal of undesirable components and minimise the removal of the valuable minor components. Some of the latter are recovered from side streams of the refining process to give commercial products such as phospholipids, free acids, tocopherols, carotenes, sterols and squalene. Because of changes that occur during refining, it is important to know whether compositional data refer to crude or refined oil. Details of the levels of these in the various seed oils are given in appropriate chapters in this volume. Extraction processes have been described by Fils (2000), De Greyt and Kellens (2000) and, more recently, Dijkstra and Segers (2007). Hamm (2001) has discussed the major differences in extraction and refining procedures in Europe and North America as a consequence of the size of the industrial plant and of the differing oilseeds to be handled. With only a limited number of oils and fats available on a commercial scale, it is not surprising that on their own these are sometimes inadequate to meet the physical, chemical and nutritional properties required for use in food products. Over a century or more, lipid technologists have designed procedures for overcoming the limitation of having only a restricted range of natural products. In particular, they have sought to modify fatty acid and Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Vegetable Oils in Food Technology Table 1.1 Methods of changing fatty acid and triacylglycerol composition to modify physical, chemical and nutritional properties. Technological solutions Blending Distillation Fractionation Hydrogenation Interesterification with chemical catalysts Interesterification with specific lipases Enzymatic enhancement Biological solutions Domestication of wild crops Oils modified by conventional seed breeding Oils modified by (intra-species) genetic engineering Lipids from micro-organisms or other unconventional sources Source: Gunstone (2006).

triacylglycerol composition, knowing that such changes influence the important properties of food fats. These have been classified (Gunstone 2006) into technological and biological procedures such as those listed in Table 1.1. The procedures most relevant to this book are fractionation, hydrogenation and modification of fatty acid composition by conventional seed breeding or genetic engineering. Details are given in some of the following chapters. As an example, the usefulness of palm oil and palmkernel oil is greatly extended by fractionation. Hydrogenation may be applied in three ways. A very light hydrogenation (brush hydrogenation) applied to soybean oil or rapeseed oil will halve the level of linolenic acid and thereby increase oxidative stability (shelf-life). More extensive, but still partial, hydrogenation is applied to unsaturated liquid oils to produce semisolid fats that can be used as margarines and spreads. Through this process the levels of polyunsaturated fatty acids are markedly reduced, saturated acid content rises slightly, and there is a large rise in the levels of monounsaturated acids, much of it with trans configuration. The trans acids have higher melting points than their cis isomers, thereby contributing to the desired increase in solid acids. However, trans acids are now accepted as having undesirable nutritional properties and the food industry has revised procedures to limit their level. In some countries the level of trans acids has to be reported on the packaging and this increases the pressure to minimise the levels of these acids (Wilson 2009). Complete hydrogenation gives a product with virtually no unsaturated acids and therefore no trans acids. This is hardstock that can be blended with unsaturated oil, often before interesterification. In the following chapters examples are cited of where fatty acid composition has been modified by biological methods, both traditional and modern. Well-known examples include low-erucic acid rapeseed oil (canola oil), high-oleic sunflower oil and low-linolenic soybean oil, but attempts to develop oils with modified fatty acid composition and/or a changed composition of minor products such as tocopherols are being pursued actively in many countries. Some of these have been described (Gunstone 2007b; Watkins 2009) and others are cited in the following chapters of this book. Perhaps the most exciting of these are the attempts to produce long-chain polyunsaturated fatty acids such as eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) in a field crop (Napier 2006). Following their introduction into commercial agriculture in 1996, genetically modified (GM) crops are now grown in many countries. Nevertheless, opposition to such crops

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remains in Europe and elsewhere and GM-free products are in demand (Section 1.3.8). This restriction also applies to minor products and it has sometimes been difficult to obtain GM-free lecithin (phospholipid), which comes mainly from soybean oil (Gunstone 2008c).

1.2 1.2.1

VEGETABLE OILS: PRODUCTION, CONSUMPTION AND TRADE Nine vegetable oils

Oils and fats are produced from animal and vegetable sources, with the former group declining in market share though not in production tonnage. Tallow, lard and butter still occupy the fifth, sixth and seventh positions after the four dominant vegetable oils (palm, soybean, rapeseed and sunflower seed). During the twentieth century the contribution of animal fats fell from 50% to 20% and in 2009 it was less than 16%, showing that vegetable fats have become increasingly dominant (Table 1.2). Statistical information about production, consumption and trade in oils and fats comes from two major sources. Oil World ISTA Mielke of Hamburg, Germany, is a market analyst producing weekly, monthly, annual and occasional reports on 10 oilseeds, 17 oils and fats (13 vegetable and 4 animal) and 10 oil meals. This valuable information has to be purchased. In contrast, information from the USDA is available free online and is updated each month (search for ‘USDA-FAS oilseeds’ in Google or any other search engine). However, this latter source does not include animal fats and covers only seven oilseeds (copra, which is the source of coconut oil, cottonseed, palmkernel, groundnut, rapeseed, soybean and sunflower seed), nine oils (from these seven oilseeds and from palm and olive) and eight oilmeals (from the seven oilseeds and from fish). The four additional vegetable oils covered by Oil World are corn, sesame, linseed and castor oils. These two sources of information show good but not perfect agreement. It is not easy for those who produce these reports to collect all the necessary data and figures continue to be subject to revision over several years. Figures in this chapter will come primarily from the USDA source and only occasionally from Oil World. This makes it easier for readers to consult the website themselves for up-to-date information. The nine vegetable oils can be classified in several ways. One categorisation recognises four major oils (palm, soybean, rapeseed and sunflower), two lauric oils (coconut and palmkernel, with a very different fatty acid composition from the other commodity oils) and the remaining oils (cottonseed, groundnut and olive). It is also useful to distinguish between oils and fats obtained from tree crops (coconut, palm and olive) and those from annual seed/bean crops, and also to recognise those that are

Table 1.2 Average annual production of total oils and fats and of animal fats (million tonnes and % of total) during the twentieth century. Years Oils and fats (17) Animal fats (mt) Animal fats (%)

1909/13

1936/39

1958/62

1976/80

1986/90

1996/2000

13.1 6.5 50

20.2 8.5 42

29.8 11.8 40

52.6 17.2 33

75.7 19.8 26

105.1 21.3 20

Source: Based on Mielke (2002) for 17 commodity oils and Hatje (1989).

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by-products. These are important factors in understanding the dynamics of production and trade. Trees have to be planted and mature, usually for many years, before they produce an economic crop. Yields from tree crops are influenced by climatic changes from season to season and by inputs such as fertiliser, pesticides, herbicides and irrigation, although crops will continue for many years (25–35 years for palm, around 100 years for olive). Annual crops (soybean, rapeseed, sunflower etc.), on the other hand, depend on planting decisions that farmers make each year based on agricultural and economic factors. These decisions result in changes in supply from year to year. For vegetable oils that are by-products, decisions on annual production depend on factors other than oil production. For example, cotton is grown according to the demand for fibre and not for cottonseed oil. Corn is not grown primarily for its oil and peanuts are grown as much for consumption as nuts as for oil production. It is also worthy of note that crushing soybeans produces two components – soybean oil (18%) and soybean meal (79%) – both of which are valuable commercial products. At different times the oil or the meal is in greater demand. Annual crops are produced at harvest time, which comes late in the calendar year in the northern hemisphere and early in the calendar year in the southern hemisphere. However, equatorial tree crops such as palm and coconut are harvested throughout the year, though there is some seasonal variation in quantity. Production data are often reported in harvest years such as 2008/09. These relate to 2008 harvests in the northern hemisphere and 2009 harvests in the southern hemisphere.

Table 1.3 Population (millions), production, exports, imports and total consumption (million tonnes) of seven oilseeds and nine vegetable oils in selected countries in 2008/09. Pop

World** China EU-27 India USA Indonesia Brazil Malaysia Pakistan Russia Japan Mexico Argentina Turkey Egypt

6829 1323 497 1198 315 230 194 27 181 141 127 110 40 75 83

Oilseeds*

Oils§

Prod

Exp†

Imp

Prod

Exp†

Imp

Consump

395.3 57.8

94.4 1.2

92.9 44.1 17.8

55.1

33.7 89.2

35.8

131.8 16.0 15.4 6.8 9.6 22.7

54.3 9.8 8.7 8.8 3.2

129.3 24.6 22.6 14.7 11.2 6.0 5.1 4.6 3.4 3.0 2.1 2.0 1.8 1.7 1.6

1.4 59.5

19.4

1.5 16.6 2.0 16.8

7.7

5.8

30.1

1.3 2.2

5.8 4.9 35.7

6.3 1.7 1.2

0.8 1.5

Source: USDA, December 2009. Notes: * Oilseeds are copra, cottonseed, palmkernel, peanut (groundnut), rapeseed, soybean and sunflowerseed. Oils also include palm and olive. ** The countries selected are the largest consumers of vegetable oils. § These figures cover oil extracted from both indigenous and imported seeds. † Canada (population 34 million) exported 10.0 million tonnes of seed and 1.6 million tonnes of oil. Ukraine (population 46 million) exported 3.7 million tonnes of seed and 2.2 million tonnes of oil.

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In discussing trade in oilseeds and oils in geographical terms, it is useful to recognise four types of countries/regions. These are discussed below and illustrated in Table 1.3. Population figures are in millions and relate to 2009. ●

●

●

●

Countries with small populations that produce large amounts of oilseeds/oils and are large exporters of these commodities. Examples are Australia (population 21 million), Malaysia (27 million), Canada (34 million), Argentina (40 million) and Ukraine (46 million). Countries with large populations that produce large amounts of oilseeds/oils and fats to feed their own populations but are still significant exporters. Examples are the USA (315 million), Indonesia (230 million) and Brazil (194 million). Countries with very large populations that are major importers despite local production. China (1323 million), India (1198 million) and other highly populated countries in Asia belong to this category. The Indian subcontinent of India, Pakistan (181 million), Bangladesh (162 million) and Sri Lanka (20 million) is a very large importer of vegetable oils. Finally there are countries/regions that are essentially traders. They produce, consume, import and export these commodities. The 27 countries of the European Union (EU-27) form the biggest example, but Hong Kong and Singapore are also significant traders by virtue of their geographical closeness to the world’s largest importer (China) and exporters (Indonesia and Malaysia).

Tables 1.4 and 1.5 show the annual production of nine vegetable oils between 1995/96 and 2008/09 (14 years). Total production of the nine oils rose from 71 to 133 million tonnes Table 1.4 Production (million tonnes) of nine vegetable oils during the period 1995/96 to 2008/09.

1995/96 1996/97 1997/98 1998/99 1999/2000 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09 Increase 1995/96 to 2001/02 Increase 2002/03 to 2008/09

9 oils

Palm

Soya

Rape

Sun

5 oils*

71.2 73.8 75.2 80.3 86.0 89.8 92.7 96.1 102.8 111.7 118.7 121.5 127.8 131.8

16.2 17.6 16.9 19.2 21.8 24.3 25.3 27.6 30.0 33.5 35.8 37.2 40.9 42.4

20.3 20.4 22.4 24.4 24.5 26.7 28.9 30.6 30.2 32.6 34.6 36.4 37.5 35.7

11.1 10.5 11.4 11.8 14.0 13.3 13.1 12.2 14.1 15.7 17.3 17.0 18.3 20.4

9.1 8.6 8.5 9.3 9.3 8.2 7.4 8.1 9.2 9.2 10.6 10.6 9.7 11.8

14.5 16.7 16.0 15.6 16.4 17.3 18.0 17.6 19.3 20.7 20.4 20.3 21.4 21.5

21.5

9.1

8.6

2.0

–1.7

3.5

35.7

14.8

5.1

8.2

3.7

3.9

Source: USDA, December 2009. Note: * Coconut, cottonseed, olive, palmkernel and peanut (groundnut) oils.

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Vegetable Oils in Food Technology Table 1.5 Four major vegetable oils as a percentage of vegetable oil production (9 oils) in the period 1995/96 to 2008/09. Oil Palm Soybean Rapeseed Sunflower seed Total

1995/96

2000/01

2005/06

2008/09

22.8 28.5 15.6 12.8 79.7

27.1 29.7 14.8 9.1 80.7

30.2 29.1 14.6 8.9 82.8

32.2 27.1 15.5 9.0 83.8

Note: Figures derived from Table 1.4.

Table 1.6 Production of 7 oilseeds, 9 oils and 8 oil meals (million tonnes) during the five-year period 2004/05 to 2008/09.

7 oilseeds* Crush Crush (%) 9 oils** 8 meals§

2004/05

2005/06

2006/07

2007/08

2008/09

381.5 302.8 79.4 111.5 207.0

391.4 318.8 81.4 118.7 216.5

404.2 328.4 81.2 121.5 224.3

391.8 338.3 86.3 127.8 230.9

385.3 338.2 87.8 131.8 228.5

Source: USDA, December 2009. Notes: * Copra, cotton, groundnut, palmkernel, rape, soy and sunflower. ** The 7 plus palm oil and olive oil. § The 7 plus fish meal (around 5 million tonnes).

(86%). Increases in palm (167%), soya (76%), rape (82%), sunflower (25%) and the remaining five oils (49%) were at the levels indicated in parentheses. The four oils increasingly dominate vegetable oil production at a total proportion exceeding 80% and rising. Annual production of nine vegetable oils in 2008/09 was expected to be about 133 million tonnes. Given an average price of around $800 per tonne, this gives a total value of over $1000–1100 billion for the year’s vegetable oil production. In Tables 1.6, 1.7 and 1.8 attention is focused on the five years 2004/05 to 2008/09 to show the most recent trends. Oils and fats come from oilseeds, fruits and from animal sources and Table 1.6 gives figures for seven oilseeds. Most of the seed is crushed to produce oil and meal, but some is held back as seed for planting and some is used directly for animal feed or human food. The proportion of these varies slightly from year to year, depending on the relative amounts of the various oilseeds with their different levels of oil. The term ‘consumption’ needs explanation. Applied to a country/region for a particular year, it is the sum of local production and imports minus exports and allowance for changes in stocks for the year in question. It applies to consumption for all purposes, including human food, animal feed, industrial consumption and waste, and cannot be equated with dietary intake. The term ‘human consumption’ in these tables refers to the consumption of nine vegetable oils and does not allow for other sources of dietary fat such as animal fats, fat from meat and nuts and so on. Consumption of these vegetable oils (for all purposes) per person is expressed in kg/year and is available on a global basis (as in Table 1.8) or for

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Table 1.7 Production (million tonnes) of 9 individual vegetable oils during the five-year period 2004/05 to 2008/09.

Total Palm Soybean Rapeseed Sunflower Groundnut Palmkernel Cottonseed Coconut Olive

2004/05

2005/06

2006/07

2007/08

2008/09

111.47 33.53 32.60 15.72 9.18 5.08 4.15 4.78 3.46 2.96

118.72 35.83 34.62 17.30 10.60 4.97 4.40 4.90 3.47 2.66

121.50 37.23 36.36 17.01 10.61 4.51 4.48 5.13 3.26 2.91

127.82 40.94 37.55 18.31 9.67 4.90 4.90 5.22 3.49 2.84

131.81 42.40 35.72 20.38 11.83 5.00 5.13 4.84 3.55 2.97

Source: USDA, December 2009. Notes: Vegetable oils listed in decreasing order of production in 2008/09. Forecast for 2009/10: total (137.3), palm (45.1), soybean (37.7) and sunflower (11.4).

Table 1.8 Production, consumption, exports and imports (million tonnes) of 9 vegetable oils during the five-year period 2004/05 to 2008/09.

Production Consumption Per person (kg/y) Exports Imports Population (billion)

2004/05

2005/06

2006/07

2007/08

2008/09

111.5 107.9 16.8 42.4 40.5 6.44

118.7 115.5 17.7 47.6 44.7 6.51

121.5 120.9 18.4 49.0 48.0 6.59

127.8 125.4 18.8 53.5 50.5 6.67

131.8 129.3 19.2 53.1 54.3 6.75

Source: USDA, December 2009.

individual countries/regions. This figure has shown a steady rise over many years. In the years between 2004/05 and 2008/09, it rose 15% from 16.8 to 19.3 kg/year. These are average values and vary considerably between countries. Values are much above this average in Europe and North America and below it in many African and Asian countries. Exports and imports are virtually the same and correspond to almost 40% of total production. The balance is used in the country where it is produced. There is also a trade in oilseeds, particularly of soybeans from North and South America to China and elsewhere (Sections 1.3.1 and 1.3.2). In Tables 1.9, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16 and 1.17, attention is directed to the production, consumption and imports/exports of the vegetable oils described in the other chapters of this book. Each table shows the major countries/regions involved. The figures in the following text apply to the year 2008/09. They vary slightly from year to year, but the major trends are unlikely to change very quickly. Readers can use the USDAFAS website to get up-to-date information. Some major points from each table are discussed here, and readers can derive further information through careful study of the tables and the appropriate chapters for each vegetable oil.

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Table 1.9 Palm oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09. Total*

Major countries/regions

Production Consumption Total

42.40

Indonesia 19.5, Malaysia 17.3, Thailand 12, Nigeria 0.8, Colombia 0.7

41.65

India 6.5, China 5.6, Indonesia 4.9, EU-27 4.6, Malaysia 2.6, Pakistan 2.2, Nigeria 1.2, USA 1.0, Thailand 0.9, Bangladesh 0.7, Egypt 0.7

Food Industrial Other Exports Imports

32.61 8.31 0.73 34.23 34.07

Malaysia 16.0, Indonesia 14.6 India 6.9, China 6.1, EU-27 4.9, Pakistan 2.2, USA 1.0, Bangladesh 0.7

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 23.38 (production), 23.20 (consumption), 16.75 (exports) and 16.64 (imports) million tonnes. These numbers indicate increases of 81%, 80%, 104% and 105% respectively.

1.2.2

Palm oil

Palm oil has long been the oil traded (imported/exported) in the greatest quantity (31 million tonnes). It is now also the oil produced in the greatest amount (43 million tonnes) and continues its steady growth. Figures in Table 1.9 show that in the 14 years between 1995/96 and 2008/09 palm oil production increased by 2.7-fold. Production and exports of this oil are dominated by two South East Asian countries. In 2008/09 Indonesia was responsible for 46% and 47% of global palm oil production and exports respectively; for Malaysia these figures were 41% and 45% respectively. Other countries in this region and in Africa and South America are trying to develop oil palm plantations, often with the assistance of Malaysian capital and Malaysian expertise, although the volumes produced remain small. The minor palm oil-producing countries include (in declining order) Thailand, Nigeria, Colombia, Ecuador and Papua New Guinea, with production levels between 1.4 and 0.4 million tonnes. Palm oil is consumed in many countries and it has been important in meeting the rapidly growing demand for vegetable oils in developing countries, with their increasing populations and increasing personal income. The main importers are now India (20% of total palm oil exports), China (18%) and EU-27 (14%). The Indian subcontinent (India, Pakistan and Bangladesh) accounts for 30% of total imports. USDA numbers (Figure 1.1) show that an increasing proportion of palm oil is being used for non-food purposes, including biodiesel production. Between 1995/96 and 2001/02 3–4 million tonnes of palm oil was used for non-food purposes. By 2008/09 this had risen to almost 10 million tonnes (Table 1.9). This change pre-dates large-scale production of biodiesel from palm oil and probably reflects the increasing use of palm oil in the oleochemical industry as an alternative to tallow, following the growth of the oleochemical industry in Malaysia.

1.2.3

Soybean oil

Soybean oil (Table 1.10) is the oil produced in the second largest amount after palm oil. In addition to the trade in soybean oil, there is a strong trade in beans. Although there is some closure of the gap between palm and soybean oil, if exported beans are considered in terms

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Palm oil

50 45

Million tonnes

40 35 Total Food Non-food

30 25 20 15 10 5

/0 9 20

08

/0 7 06

/0 5 20

04 20

02

/0 3

/0 1 20

00 20

/9 9 98 19

19

96

/9 7

0

Year Figure 1.1 Consumption of palm oil (million tonnes) from 1996/97 to 2008/09 divided between food and non-food uses. Source: USDA, December 2009. Note: Non-food uses include animal feed, oleochemicals and biodiesel.

Table 1.10 Soybean oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Exports Imports

Total*

Major countries/regions

35.71 35.68 9.01 8.87

USA 8.50, China 7.31, Argentina 6.12, Brazil 6.02, EU-27 2.31, India 1.34 China 9.49, USA 7.43, Brazil 4.27, EU-27 2.80, India 2.33, Argentina 1.40 Argentina 4.67, Brazil 1.91, USA 0.99 China 2.49, India 1.06, EU-27 0.82

Source: USDA, December 2009. Notes: There is also significant trade in soybeans. * Figures in the first edition of this book (2000/01) were 26.66 (production), 26.65 (consumption), 7.45 (exports) and 7.44 (imports) million tonnes. These numbers indicate increases of 34%, 34%, 21% and 19% respectively.

of their oil equivalent, palm oil trade still exceeds that of soybean oil. There is no comparable trade in palm fruits, since these must be extracted as soon possible after harvesting and as close as possible to the place of harvesting. The major producers of soybean oil are the USA, Brazil, Argentina, China (local beans augmented with imports) and EU-27 (using mainly imported beans). Soybean is consumed in every country for which details are available. Consumption is greatest in the producing countries, with six countries/regions each exceeding one million tonnes. These are China (27% of world consumption), USA (21%), Brazil (12%), EU-27 (8%), India (6%) and Argentina (4%). Argentina is now the largest exporter of soybean oil

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(4.7 million tonnes, 52% of total soybean oil exports). Many countries import soybean oil, with China (28% of world imports) being dominant in 2008/09. The USDA does not provide figures for the industrial use of soybean oil, but the Soy Stats website reports that in 2008 in the USA 1.55 million tonnes (18% of the total of 8.43 million tonnes) was used for industrial purposes. This included 2612 million litres of biodiesel (equivalent to 2.3 million tonnes of source material, which is mainly but not entirely soybean oil). Figures for 2006 and 2007 biodiesel production were 946 and 1713 million litres respectively. It seems likely that a smaller proportion of soybean oil is used for industrial purposes in other countries, though there is now a considerable and growing production of biodiesel in Argentina and Brazil. For 2009 this figure is over 1 million tonnes in each country, produced mainly, but not entirely, from soybean oil (see Table 1.21). Most (85–90%) of the soybeans grown in the USA are now obtained from GM seeds and non-GM soybean oil is only available from identity-preserved beans. Sourcing non-GM lecithin from non-GM beans has provided some challenges. Soybean oil from Argentina and from Brazil also comes mainly and increasingly from GM seeds (ISAAA, Soy Stats and Soya Tech websites). Those countries that are concerned about vegetable oils from GM seeds are worried not only about the supply of soybean oil but also of the minor products (lecithin, tocopherols, sterols) from this source.

1.2.4

Rapeseed/canola oil

Rapeseed/canola oil (Table 1.11) now occupies the third position in rank order of production of oils and fats after palm and soybean oils (Table 1.4). EU-27, China and India dominate production and consumption of this oil, and Canada, with its relatively small population (34 million), is an important grower and exporter of seed. Since the first edition of this book there has been a marked change in the non-food use of this oil, related particularly to its use in Europe as the dominant source of biodiesel (Table 1.21). The plot in Figure 1.2 shows a change starting in 2003/04. In the period up to 2002/03 non-food consumption of rapeseed oil was about 1 million tonnes (0.9–1.3, 5–10% of total production). Over the last six years non-food consumption has risen to 6 million tonnes (now around 30%), while food consumption has also risen but only from 13 to 14 tonnes

Table 1.11 Rapeseed oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Total Food Non-food Exports Imports

Total*

Major countries/regions

20.38

EU-27 8.42, China 4.70, India 2.06, Canada 1.78, Japan 0.88

19.92 13.97 5.95 2.37 2.44

EU-27 8.54, China 4.85, India 2.05, Japan 0.92, Canada 0.35

Canada 1.53 EU-27 0.45, China 0.45

Source: USDA, December 2009. Notes: There is also significant trade in seed. * Figures in the first edition of this book (2000/01) were 14.15 (production), 14.28 (consumption), 1.65 (exports) and 1.64 (imports) million tonnes. These numbers indicate increases of 44%, 39%, 44% and 49% respectively.

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Rapeseed oil 25.00

Million tonnes

20.00

Total Food Non-food

15.00 10.00 5.00

/0 9 08

/0 7

20

06 20

04

/0 5

/0 3 20

02

20

00

/0 1

/9 9 20

98

19

19

96

/9 7

0.00

Year Figure 1.2 Consumption of rapeseed oil (million tonnes) from 1996/97 to 2008/09 divided between food and non-food uses. Source: USDA, December 2009. Note: Non-food uses include animal feed, oleochemicals and biodiesel.

Table 1.12 Sunflower oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Exports Imports

Total*

Major countries/regions

11.83 10.83 4.59 4.04

Russia 2.56, Ukraine 2.63, EU-27 2.33, Argentina 1.52, Turkey 0.51 EU-27 3.19, Russia 1.92, Turkey 0.79, Argentina 0.38, Ukraine 0.36, Ukraine 2.10, Argentina 1.10, Russia 0.80 EU-27 1.05, Turkey 0.43

Source: USDA, December 2009. Notes: There is also trade in seeds. * Figures in the first edition of this book (2000/01) were 8.87 (production), 9.17 (consumption), 2.37 (exports) and 2.39 (imports) million tonnes. These numbers indicate increases of 33%, 18%, 94% and 69% respectively.

(Table 1.19). It appears that most of the additional production of rapeseed oil in the last six years has gone into non-food uses.

1.2.5

Sunflowerseed oil

Sunflowerseed oil (Table 1.12) is the last member of the group of four major vegetable oils. It maintains its share at about 9% of total vegetable oils, although it has achieved variable levels over recent years (Tables 1.4 and 1.5). It is available in forms that vary markedly in fatty acid composition (see Chapter 5), but these are taken together in the data presented here. Production is mainly in the area covered by Russia, Ukraine, Turkey and adjoining countries in Europe. It is also grown in Argentina.

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12

Vegetable Oils in Food Technology Table 1.13 Groundnut oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Exports Imports

Total*

Major countries/regions

5.00 4.86 0.19 0.16

China 2.17, India 1.54 China 2.18, India 1.42 EU-27 0.10, USA 0.02

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 4.86 (production) and 4.87 (consumption) million tonnes. These numbers indicate increases of only 4% and 0% respectively.

Table 1.14 Cottonseed oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Exports Imports

Total*

Major countries/regions

4.83 4.79 0.19 0.07

China 1.60, India 1.03, USA 0.30 China 1.59, India 1.04 USA 0.22 USA 0.09

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 3.89 (production) and 3.94 (consumption) million tonnes. These numbers indicate increases of 24% and 22% respectively.

1.2.6

Groundnut (peanut) oil

Only about 46% of groundnuts are crushed, most of the balance being consumed as nuts. There is very little trade in the oil. It is produced and used mainly in China and India, which together account for around 74% of both total production and consumption (Table 1.13). Minor quantities of the oil are produced and used in African countries.

1.2.7

Cottonseed oil

Cottonseed oil (Table 1.14) is another oil traded only to a small extent. China is the major producer and consumer (almost one third of the total), with India, the USA, the former Soviet Union, Pakistan, Brazil and Turkey producing lower levels. This crop is grown for its fibre, with the seed oil as a by-product.

1.2.8

Coconut oil

Coconut oil (Table 1.15) has had a very uneven record in terms of its production as a consequence of climatic and political instability in the countries where it is produced. Production at 3–4 million tonnes is mainly in the Philippines, Indonesia and India. The Philippines and Indonesia are major exporters, while the EU-27 and the USA are major importers. Coconut

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Production and Trade of Vegetable Oils

13

Table 1.15 Coconut oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Total Food Industrial Exports Imports

Total*

Major countries/regions

3.55

Philippines, Indonesia, India

3.37 1.82 1.51 1.66 1.61

EU-27, USA, India, Philippines

Philippines, Indonesia EU-27, USA, Malaysia

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 3.43 (production), 3.30 (consumption), 2.05 (exports) and 2.09 (imports) million tonnes. These numbers indicate increases of only 3% and 2% for production and consumption respectively. Imports and exports have declined. In contrast, the other lauric oil (palmkernel) has risen steadily along with palm oil production and now exceeds coconut oil.

Table 1.16 Palmkernel oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09.

Production Consumption Exports Imports

Total*

Major countries/regions

5.13 5.28 2.18 2.42

Malaysia, Indonesia Malaysia, EU-27, China, USA Indonesia, Malaysia EU-27, USA, Malaysia

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 2.89 (production), 2.81 (consumption), 1.43 (exports) and 1.42 (imports) million tonnes. These numbers indicate increases of 78%, 88%, 52% and 70% respectively and parallel the changes for palm oil.

is an important lauric oil used about equally by the food and oleochemical industries. It competes with palmkernel oil as the other major lauric oil.

1.2.9

Palmkernel oil

Palmkernel oil (Table 1.16) is produced along with palm oil from the oil palm and has shared in the rapid growth of the latter commodity. Production levels now exceed those of coconut oil. Malaysia and Indonesia are major producing countries, with the EU-27 and USA being major importing countries/regions. As with coconut oil, consumption is divided roughly equally between food and non-food uses.

1.2.10 Olive oil Olive oil (Table 1.17), produced at a level of around 3 million tonnes, has a long history going back to biblical times. It is produced and consumed in several Mediterranean countries. Small quantities are produced in Australia and New Zealand and in California. It is sold as a premium oil with strong marketing and is a component of the healthy Mediterranean lifestyle.

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14

Vegetable Oils in Food Technology Table 1.17 Olive oil: Major countries/regions involved in production, consumption and trade (million tonnes) in 2008/09. Total* Production Consumption Exports Imports

2.97 2.95 0.68 0.59

Major countries/regions EU-27 2.25, Turkey 0.17 EU-27 2.06, USA 0.27, Turkey 0.12 EU-27 0.41 USA 0.28, EU-27 0.15

Source: USDA, December 2009. Note: * Figures in the first edition of this book (2000/01) were 2.56 (production), 2,70 (consumption), 0.55 (exports) and 0.55 (imports) million tonnes. These numbers indicate increases of only 16%, 9%, 24% and 7% respectively.

1.2.11 Corn oil Corn oil is not included in the USDA figures. It was produced at levels around 2.4 million tonnes in 2008/09. In 2000/01 this figure was 2.0 million tonnes. About half of this comes from the USA, with China being the second largest producer. Imports and exports total about 0.7 million tonnes, with the USA the largest exporter and Turkey and Saudi Arabia the largest importers.

1.2.12 Sesame oil Sesame oil is not included in the USDA figures. It was produced at levels around 0.85 million tonnes in 2008/09. In 2000/01 this figure was 0.78 million tonnes. Production is mainly in China, Myanmar (Burma) and India and the oil is consumed mainly in the same three countries. There is only a limited trade in both oilseeds and oil.

1.2.13 Linseed oil Linseed oil is not included in the USDA figures. The seed (2–3 million tonnes) is grown mainly in Canada, China and India. Canada remains the largest grower, although production has declined in recent years. The oil (around 0.7 million tonnes) is produced mainly in the EU-27, China and the USA, using seed imported from Canada where necessary. There is very little trade in the oil.

1.3 1.3.1

SOME TOPICAL ISSUES Imports into China and India

The demand for vegetable oils and animal protein has increased steadily over many years, through increases in population but more through increases in income and in urbanisation. The increase in animal protein leads to a rising demand for seed meal, sourced mainly from oilseeds in general and from soybean in particular. Table 1.18 shows the increased consumption in China and in India in the past five years. Although both of these highly populated countries are significant producers of oilseeds, local production is insufficient to meet the growing indigenous demand. In China the gap has been met in part by extraction of imported

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Production and Trade of Vegetable Oils

15

Table 1.18 Consumption and imports (million tonnes) for China and India during the five-year period 2004/05 to 2008/09. 2004/05 China (population Oilseeds Production Imports Crush seeds

2005/06

2006/07

2007/08

2008/09

in 2009 1.32 billion) 58.35 26.12 60.54

56.80 29.00 64.97

55.23 29.70 65.28

53.35 38.64 68.47

57.80 44.14 72.88

13.81 6.69 20.53

14.76 6.96 21.51

14.27 8.50 22.56

14.69 8.76 23.34

16.02 9.77 24.65

India (population in 2009 1.20 billion) Oilseeds Production 29.40 30.70 Crush seeds 23.57 25.10

29.92 24.62

33.95 27.56

33.70 26.44

Vegetable oils Production Imports Consumption

6.43 5.44 11.91

7.01 5.91 12.96

6.80 8.79 14.73

Vegetable oils Production Imports Consumption

6.47 5.68 11.56

6.85 4.86 12.11

Source: USDA. Note: In 2008/09 world consumption of vegetable oils was 129 million tonnes and imports of oilseeds and of vegetable oils were 93 and 54 million tonnes respectively.

soybeans and rapeseed, providing both oil and meal, but the country still needs to import about one third of its vegetable oil consumption as palm and soybean oils (Tables 1.8 and 1.9). India imports increasing amounts of palm oil to meet its shortfall between consumption and local production (Table 1.9).

1.3.2

Trade in oilseeds and in vegetable oils

This book is devoted to vegetable oils and in this chapter information on the production, consumption and trade (imports and exports) is presented and discussed. For palm, olive and corn oils, these data give a good picture of the situation, but for oils extracted from seeds the picture is incomplete. There is considerable trade in oilseeds as well as in extracted oils. While it is not appropriate to give a full picture of oilseed movements here, trade in vegetable oils cannot be fully understood without attention to trade in oilseeds (Gunstone 2010a).

1.3.3

Food and non-food use of vegetable oils

This book is concerned with the source and composition of vegetable oils used in the food industry, but it must not be forgotten that a small but increasing share of vegetable oils is used in the oleochemical industry. Those most used for this purpose are the two lauric oils (coconut and palmkernel), palm (especially palm stearin) and linseed, along with castor oil (and tallow), although most vegetable oils find some oleochemical use. This includes the relatively new demand for biodiesel, which is usually the methyl esters of a readily available oil. This will be soybean (or tallow) in the USA and in South

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16

Vegetable Oils in Food Technology

Table 1.19 Total consumption and non-food use (million tonnes) of selected vegetable oils in 1999/2000 and 2008/09. Total consumption

1999/2000 2008/09

Non-food use*

Veg. oils**

Palm

Rape

Laurics§

Other†

Veg. oils**

Palm

Rape

Laurics§

Other†

82.7 129.3

20.5 41.6

13.7 19.9

5.6 8.7

42.9 59.1

8.1 26.1

3.1 9.0

0.7 6.0

2.8 4.3

1.5 6.8

Source: Based on USDA, December 2009. See also Gunstone 2009. Notes: * Non-food uses include oils fed to animals, those used in the traditional oleochemical industries, and those now used to produce biodiesel. The figures for non-food use are obtained by subtracting food consumption from total consumption. Figures for food use can be recovered from those provided in the table. ** Vegetable oils are the total for 9 oils. In addition to those listed in the table they include cottonseed, groundnut (peanut), olive, soybean and sunflower. § The lauric oils are coconut oil and palmkernel oil. In the absence of other information it is assumed that equal quantities of the lauric oils are used in food and non-food products. † The figures for ‘other’ are calculated from the remaining figures. The non-food figures for ‘other’ will relate mainly to soybean oil, as there is only a limited non-food use of cottonseed, groundnut (peanut), olive and sunflower oils.

America, rapeseed oil in Europe, palm oil in Malaysia and Indonesia, coconut in the Philippines and waste frying oil in Japan and elsewhere. Data given in Table 1.19 show how the non-food use of nine major vegetable oils has doubled from around 10% in the 1990s to around 20% in 2008/09. The USDA does not provide figures for the industrial use of soybean oil but the Soy Stats web site (accessed November 2010) reports that in 2009 in the USA 1 million tonnes (13% of the total of 7.41 million tonnes) was used for industrial purposes. This included 2063 million litres of biodiesel (equivalent to 1.8 million tonnes of source material, which is not entirely soybean oil). Figures for 2006, 2007 and 2008 biodiesel production were 848, 1893 and 2618 million litres respectively. It seems likely that a smaller proportion of soybean oil is used for industrial purposes in other countries, though there is now a considerable and growing production of biodiesel in Argentina and Brazil. For 2009 this figure is over 1 million tonnes in each country, produced mainly, but not entirely, from soybean oil (see also Table 1.21).

1.3.4

Prices

In the 10-year period 1998/99 to 2007/08, the average price of palm ($478/tonne in Malaysia) and of soya ($597), canola ($662), sunflower ($707) and coconut oil ($632) in Rotterdam, were as indicated in parentheses. As these figures show, palm oil is usually the cheapest and sunflower the most expensive of these vegetable oils. At the beginning of this period soybean oil and canola were comparable in price, but the demand for rapeseed oil for biodiesel has pushed the price of this oil above that of soybean oil. Average prices of these five oils for each year, plotted in Figure 1.3, show how the prices follow each other from year to year but with marked changes in price levels during the 12-year period covered in the graph. Palm oil, for example, ranged in price from $235/tonne in 2000/01 to $1058 in 2007/08. These changes are even more marked using monthly rather than annual figures. During 2007/08, palm ($1291 in March), soya ($1537 in June), canola ($1577 in June), sunflower ($2045 in June) and coconut ($1824 in May) had peak prices at the level and month shown in parentheses. It is apparent from Figure 1.3 that over the 12 years prices have fallen, risen, stayed level, risen sharply and then fallen back to the previously high values reached two years earlier. This price information comes from USDA

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Production and Trade of Vegetable Oils

17

Vegetable oil prices

1800 1600

US dollars/tonne

1400 1200

Palm Mal Soya Rott

1000

Canola Rott 800

Sun Rott

600

Coco Rott

400 200

2008/09

2007/08

2006/07

2004/05

2005/06

2003/04

2002/03

2001/02

2000/01

1999/00

1998/99

0

Year Figure 1.3 Prices of selected vegetable oils (US$/tonne) in Rotterdam or Malaysia during the 11 years 1998/99 to 2008/09. Source: USDA, December 2009.

figures of March and December 2009. Readers who want more recent information should go to the newest USDA-FAS figures. Rising prices are a consequence of the mismatch between supply and demand, which are themselves influenced by the following factors: ●

●

●

●

Gunstone_c01.indd 17

Growing food demand from a rising population with increasing wealth has been estimated at 4–5 million tonnes extra each year. Because of the world recession demand may have been at the lower end of this range in 2009. Demand for biodiesel, increasing at around 3 million tonnes per year, is mainly sourced from rapeseed oil and soybean oil, but not all of it comes from the major vegetable oils. Palm biodiesel is expected to become more important in the future and there are also other sources that are outside the usual listings of commodity oils, such as used frying oils, oils from new vegetable sources such as jatropha, and algal oil. There has been a great deal of investigation of these last two sources, but the final product is only now beginning to appear in small quantities. Eventually these will relieve the pressure on food oils. Furthermore, the availability of biodiesel will be affected by extremely high or low prices for mineral oil and for vegetable oils (see Table 1.21). The growing demands for food and biodiesel at about 7–8 million tonnes (with provisos set out above) are to be compared with annual increases in production in recent years of 4–9 million tonnes. Production levels in 2008/09 were expected to be 133 million tonnes for the nine major vegetable oils and a further 24 million tonnes for four animal fats. There has been an increase in the cost of agricultural production (fertilisers and pesticides are more expensive) and of storage and transport, all resulting from the considerable rise in the price of oil.

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18 ●

●

Vegetable Oils in Food Technology

Oilseed yields have fallen through poor climatic conditions in many parts of the world. For example, in recent years there have been droughts in Europe, Australia, Indonesia, Ukraine, south west Russia and China. Whenever there are substantial increases in prices, speculators interfere in the market, pushing up prices and making profits for themselves.

All this suggests that biodiesel production is only one of several factors driving prices upwards. Not everyone regards high vegetable oil prices as an unmitigated disaster, however. The commodity analyst Dorab Mistry of Godrej International in India spoke in support of high vegetable oil prices in 2007 (Mistry, 2007). Talking perhaps from an Indian viewpoint, he reminded his hearers that agricultural commodities have declined in real terms during the last 50 years and that as a consequence young people do not want to follow their parents into farming, so agriculture fails in the scramble for talent. He argued that higher prices for agricultural commodities are the fastest way to end rural poverty and have the highest multiplier effect for job creation and economic expansion in the economy. Low prices keep farmers poor, but higher growth in rural communities translates into higher growth for the economy as a whole and benefits everyone. He claimed that high prices for cereals and oilseeds are related to rapidly rising demand in the developing world at the same time as climatic conditions have reduced supplies in several parts of the world through recent droughts. Demand for biofuel is a further factor, although it is not the only reason for present high prices. At the time of writing the position is confused and the outlook uncertain. The price of mineral oil fell from its peak level in July 2008 of almost US$150 a barrel to levels between 30% and 40% of the maximum by the end of 2008, but then rose to around US$70. This volatility in price makes planning and development of future supplies very difficult. Vegetable oil prices have also dropped from the exceedingly high levels of the 2007/08 harvest year, but it is not clear at what levels these will settle (Figure 1.3). The demand for biofuels comes mainly from the developed world for environmental and political reasons, while the effect of high prices is felt most by the poor of Asia and Africa. Some of the poorer producing countries have introduced export tariffs on vegetable oils to keep sufficient supplies to feed their own people. Others, such as India, have decreed that biodiesel cannot be made from food-quality oils and fats. Presumably this restriction has been extended to the use of land that can grow food crops. This has led to the development of non-food crops such as jatropha and pongamnia, though the effects of these changes are not yet significant. The consequence of the below-peak prices is not clear. Accessibility by the poor for food use may increase, but the reduced cost also makes biodiesel production more viable. Furthermore, the changing price of mineral oil has an effect on biodiesel demand, though it has to be remembered that this last is often related to national mandate rather than to economic viability. The fall in income in the developed and the developing world during 2008 and later years is likely to reduce demand for vegetable oils, but it is too early to assess the level of this. Changing prices for vegetable oils can be considered over various time scales. In line with other agricultural commodities there has been a general decline in prices over 50 or more years of around 3% a year, so that prices have halved in real terms each 20–25 years. However, in the more recent past there have been violent fluctuations in both directions. For example, the very low prices being registered at the turn of the century were in marked contrast to the very high prices obtained more recently, though these have been falling since mid-2008 (Figure 1.3).

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1.3.5

19

The food–fuel debate

Two issues have come together to produce the food–fuel debate for oils and fats. One is the rise in prices for these commodities in recent years (Section 1.3.4) and the consequence of this, particularly for the poorer members of the world community. The other is the growing competition for commodities that can be used for food or fuels. This debate is related to supply and demand for both food and non-food purposes (Table 1.19). In this section the following topics will be discussed: ● ● ● ● ● ●

population changes; growing demand for food purposes; growing demand for non-food purposes, particularly biodiesel; increasing supply; reasons for changing prices; food vs fuel.

According to Evans (1998) the world population grew to one billion by 1825 and then passed through 2 billion (1927), 3 billion (1960), 4 billion (1975), 5 billion (1986) and 6 billion (1999). This means that those now in their 80s have seen the population treble in their lifetime and those approaching 50 have seen it double. It is expected that by 2050 the population will be around 9.4 billion, but that it will probably not increase much beyond that figure. To feed that number of people, Evans indicates that two problems have to be solved: we need to develop the global capacity to feed another 3 billion people and also to eliminate poverty and provide the health and education that would allow the poor to obtain food. Evans argues that agricultural science and technology should be able to address the first problem through six activities: (i) increase the area of land under cultivation; (ii) increase the crop yield per hectare of cultivation; (iii) increase the number of crops per hectare per year; (iv) displace lower-yielding crops by higher-yielding ones; (v) reduce post-harvest losses; and (vi) reduce the use of crops as feed for animals. All this has to be achieved without impoverishment of the soil and without excessive demand on water supplies. On the basis of the figures in Table 1.20, the population at present is increasing by about 800 000 each year and this raises the demand for oils and fats by about 1.3 million tonnes merely to maintain present consumption levels (Gunstone 2008a, b). However, not only is the population increasing in number. There is increasing wealth and increasing urbanisation, both of which raise the food demand for oils and fats and for meat (and therefore for seed meal required for animal feed). It is more difficult to estimate demand arising from these factors. In the 1980s the market analysts at Oil World considered that demand from increasing income was twice as large as that from increasing numbers, but the author of this chapter considers that in the light of rapid changes in China and India and other developing countries, this factor is probably closer to three (Gunstone 2008b). This suggests an increasing demand for food purposes of about 5 million tonnes each year. Since around the 1980s it has been accepted that 17 commodity oils and fats are used for human food, animal feed (in addition to seeds used directly as animal feed) and for the oleochemical industry (producing soap and other surface-active compounds, glycerol and for use in paints and so on) in a ratio of approximately 80:6:14. With the new demand for biodiesel this is more likely to be 74:6:20 today and figures of 68:6:26 have been suggested for 2020 (Gunstone 2007a). These changing ratios indicate that a lower

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20

Vegetable Oils in Food Technology Table 1.20 Oil and fat production, population and average use (for all purposes) since 1976. Year

Production

Population

Average

million tonnes

billions

kg/person/yr

Five-year averages 1976–80 52.7 1981–85 63.1 1986–90 75.7 1991–95 86.8 1996–2000 105.1

4.28 4.66 5.08 5.50 5.90

12.3 13.5 14.9 15.8 17.8

Individual years 2000 114.7 2001 117.6 2002 120.5 2003 124.8 2004 132.4 2005 141.1 2006 150.0 2007 154.1 2008 159.7

6.07 6.15 6.22 6.30 6.43 6.51 6.59 6.67 6.75

18.8 19.1 19.3 19.8 20.6 21.7 22.8 23.1 23.7

Sources: Mielke (2002, 2004, 2009).

proportion of oils and fats will be available for human food, but not a lower amount because of the increasing supply (see below). There is no doubt that things are changing at the margin. Gunstone (2007a) compared data for two seven-year periods, 1993/94 to 1999/2000 and 1999/2000 to 2006/07, in respect of the nine major vegetable oils. In the first seven-year period an increase of 21.2 million tonnes was split between greater food use (19.7 million tonnes) and non-food use (up 1.5 million tonnes). In the more recent seven-year period an increase of 39.2 million tonnes was split between these two categories at levels of 24.5 and 14.7 million tonnes. There has clearly between a shift towards non-food use. This is mainly apparent in palm oil (non-food use up 6.9 million tonnes) and rapeseed oil (up 4.2 million tonnes), as shown in Figures 1.1 and 1.2. Similar figures for other years are given in Table 1.19. In considering these ratios it has to be noted that different figures are obtained when considering only nine vegetable oils from those when the animal fats and some minor vegetable oils are included (17 oils and fats). Demand for biodiesel can be assessed at three levels: that required by national mandates at specified dates in the future, that indicated by the size and number of biodiesel plants being commissioned, and that reported as production levels. The last is the most realistic figure, although it is not easy to locate. The Freedonia group has published a report on world fuel demand and some interesting figures from it are cited in a recent issue of INFORM (Anon 2008). World biodiesel demand in 2001, 2006, 2011 and 2016 is given as 1.1, 6.0, 23.6 and 37.5 million tonnes respectively, suggesting annual increases of around 3.5 and 2.8 million tonnes in the five-year periods 2007–11 and 2012–16 respectively. However, part of this demand lies outside the normal range of commodity oils and does not compete with food sources. More recent production figures are given in Table 1.21. Oil and fat supplies increased steadily through the twentieth century. Between 1909 and 1913 supply averaged 13.1 million tonnes, increasing to 20.2 million tonnes in the period

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Production and Trade of Vegetable Oils Table 1.21

EU-27 USA Argentina Brazil Other Total

21

Biodiesel production (million tonnes) from 2006 with estimates for 2010. 2006

2007

2008

2009

2010

Major oil source

4.9 1.1 0 0.1 1.0 7.1

5.9 1.7 0.3 0.4 1.3 9.5

7.5 2.7 0.7 1.0 2.4 14.3

8.4 1.8 1.2 1.4 3.1 15.9

9.5 2.1 1.6 2.0 4.0 19.2

Rapeseed Soybean Soybean Soybean

Source: Gunstone (2010b). Notes: Other countries producing biodiesel include Columbia, Thailand and Malaysia. Animal fats are used to produce 1.0 million tonnes of biodiesel and there is some production of biodiesel from waste fat. Argentina exports most of its biodiesel to EU-27.

Table 1.22 Production of 9 vegetable oils (million tonnes) in the 14-year period 1995/96 to 2008/09. 1995/96 Total (9 oils) Palm Soya Rape Sun Other (5 oils)*

71.2 16.2 20.3 11.1 9.1 14.5

2008/09

Increase (mt)

131.8 42.4 35.7 20.4 11.8 21.5

Increase (%)

60.6 26.2 15.4 9.3 2.7 7.0

85 162 76 84 30 48

Source: USDA, December 2009. Note: * Cottonseed, peanut, olive, coconut and palmkernel oils.

1936–39 and to 29.8 million tonnes in 1956–62 (Hatje 1989; Gunstone 2002; Table 1.2). These figures can be compared with the more recent levels detailed in Table 1.20. Increase in production is larger than the rise in population, so that consumption for all purposes has increased over the last 30 years, as shown in Table 1.20. Annual production between 1960 and 2000 increased by a factor of four and doubled in the 20 years between 1985 and 2005. It remains to be seen whether future increases will be enough to meet the growing food and non-food demand. Traditionally agricultural products have met demands for food, feed and fibre (the three fs). Now another ‘f’ is being added – fuel. As indicated earlier in this chapter, growth in production levels is related mainly to increased production of palm, soy and rapeseed oils.

1.3.6

Predictions for future supply and demand

Production of the nine vegetable oils increased by 60.6 million tonnes (86%) in the 14 years between 1994/95 and 2008/09, with annual increases ranging between 1.4 and 8.9 million tonnes (Table 1.22 and 1.23). Closer examination of the figures shows a marked difference between the first six years, in which the increase was 21.6 million tonnes, and the second six

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Vegetable Oils in Food Technology

Table 1.23 Increases in levels of production of palm, soy, rape and sun oils (million tonnes) in the six-year periods 1994/95 to 2001/02 and 2002/03 to 2008/09.

1995/96 to 2001/02 2002/03 to 2008/09

9 oils

Palm

Soy

Rape

Sun

5 oils

21.6 35.7

9.1 14.8

8.6 5.1

2.0 8.2

–1.6 3.7

3.5 3.9

Source: USDA, December 2009.

Production

45 40

Million tonnes

35 30 Palm

25

Soya

20

Rape

15

Sun

10 5

9 /0 08 20

/0 06 20

04

/0

7

5

3 20

20

02

/0

1 00

/0

9 20

/9 98 19

19

96

/9

7

0

Year Figure 1.4 Production (million tonnes) of palm, soya, rape, and sun oils in the 14 years 1995/96 to 2008/09. Source: USDA, December 2009.

years, with an increase of 35.7 million tonnes perhaps reflecting the increased demand for food and for biodiesel in the last few years. Similar results are shown for selected oils in Table 1.22 and 1.23 and Figure 1.4. The nine vegetable oils increased by 4.3 million tonnes each year.

1.3.7

Sustainability

The concept of sustainability for palm oil and soybean oil arises from concerns by customers in Europe and North America that increased supplies of these two oils for food and fuel should be produced in a sustainable way that does not damage the environment. The first concern was to stop the destruction of tropical rain forests, particularly in South East Asia and Brazil, but the concept has been widened to include other aspects of responsible agriculture, such as the health, housing and education of local people involved in the industry.

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Production and Trade of Vegetable Oils

23

In the case of palm oil, plantation owners strive to meet agreed criteria over a period of time and independent auditors confirm that the required standards have been met for the production of an agreed quantity of palm oil. The owners then receive a certificate for each tonne of oil produced under these conditions and the certificates are sold to concerned buyers at a negotiated price. In one system the sustainable oil is not kept separate from commodity oil and this greatly simplifies the whole operation. In return for his efforts, the supplier has saleable certificates and the purchaser of these can advertise to his customers that a percentage of his purchases represent sustainable palm oil. Marketing of the certificates between trader and purchaser is carried out on the internet with a minimum of effort. Discussions on what is required of a sustainable oil plantation have been going on for some time and it has taken some years for wide-ranging standards to be achieved. The first supplies of sustainable palm oil and their associated certificates were first traded towards the end of 2008, but it is hoped that once started the system will grow rapidly. Appropriate negotiations over soybean oil are also under way.

1.3.8

Genetic modification

The first commercial oilseeds from genetically modified plants appeared in 1996 and have developed since then in terms of the range of crops themselves, the countries in which they are grown and the modified traits present in the GM plants. This has a consequence for the oilseeds, for oils and meals derived from them, and for downstream products such as phospholipids and vitamins. The first genetically modified crops were mainly of benefit to the grower in respect of weed control and pest control. A second generation has modified constituents such as changed fatty acid composition or enhanced vitamin levels. In the oil and fat field the most important GM crops are soybean, rape, cotton and maize (ISAAA website). The area under cultivation by GM crops has increased every year since 1996 and in 2007 reached 114 million hectares. According to ISAAA, ‘the first dozen years of biotech crops have delivered substantial economic and environmental benefits to farmers in both industrial countries and developing countries where millions of farmers have also benefited from social and humanitarian benefits which have contributed to the alleviation of their poverty’. This view is not universally accepted and in Europe in particular there has been a strong reluctance to accept these products and the benefits claimed for them. Biotech crops are now grown in 23 countries, with 8 growing more than 1 million hectares each (USA, Argentina, Brazil, Canada, India, China, Paraguay and South Africa). So much GM soybean is grown in North and in some parts of South America that non-GM soybeans are only available as an identity-preserved (IP) product. There is some evidence that European objection is weakening to GM products in animal feed if not in human food. Reference is made in Chapters 3 and 4 to GM soybeans and rapeseeds with modified fatty acid composition (see also Watkins 2009). These products are considered to be nutritionally or technically superior to the traditional non-modified oils. Considerable effort is being made to develop plants containing long-chain PUFA (especially EPA and DHA) in their seed oils. This has been achieved in the greenhouse/laboratory and is being transferred to the field (Napier 2006). Progress has also been made in developing plants that produce stearidonic acid (18:3 n-3) (Harris et al. 2008) Such material is required to meet the growing demand for nutritionally important acids that are at present only available in fish and fish oils or produced from selected micro-organisms. It will be interesting to see the European reaction to such GM products when they are generally available.

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Genetic modification is also being used to increase yields and harvestable area by increasing resistance to high and low temperatures and for growth in salty and arid soils.

REFERENCES Anon (2008) World demand for biodiesel still rising, INFORM, 19, 324. De Greyt, W. and Kellens, K. (2000) Refining practice, in Edible Oil Processing (eds W. Hamm and R.J. Hamilton), Sheffield Academic Press, Sheffield, pp. 79–128. Dijkstra, A.J. and Segers, J.C. (2007) Production and refining of oils and fats, in The Lipid Handbook, 3rd edn (eds F.D. Gunstone, J.L. Harwood and A.J. Dijkstra), CRC Press, Boca Raton, pp. 143–262. Evans, L.T. (1998) Feeding the Ten Billion: Plants and Population Growth, Cambridge University Press, Cambridge. Fils, J.-M. (2000) The production of oils, in Edible Oil Processing (eds W. Hamm and R. J. Hamilton), Sheffield Academic Press, Sheffield, pp. 47–78. Gunstone, F.D. (2002) Production and trade of vegetable oils, in Vegetable Oils in Food Technology: Composition, Production and Uses (ed. F.D. Gunstone), Blackwell Publishing Ltd., Oxford, pp. 15–16. Gunstone. F.D. (2006) Introduction: Modifying lipids – why and how? In Modifying Lipids for Use in Food (ed. F.D. Gunstone), Woodhead Publishing, Cambridge, pp. 1–8. Gunstone, F.D. (2007a) Update on food and nonfood uses of oils and fats, INFORM, 18, 573–574. Gunstone, F.D. (2007b) Major oils from plant sources, in The Lipid Handbook, 3rd edn (eds F.D. Gunstone, J.L. Harwood and A.J. Dijkstra), CRC Press, Boca Raton, pp. 38–69. Gunstone, F.D. (2008a) Oil and fat supply and demand for the rest of this decade, INFORM, 19, 215–218. Gunstone, F.D. (2008b) Oil and fat forecast. Can we increase supplies? INFORM, 19, 655–656. Gunstone, F.D. (2008c) Phospholipid Technology and Applications, The Oily Press, Bridgwater. Gunstone, F.D. (2009) Non-food uses of vegetable oils, Lipid Technology, 21, 164. Gunstone, F.D. (2010a) Trends in oilseeds and vegetable oils, Lipid Technology, 22, 24. Gunstone, F.D. (2010b) Biodiesel in market report, Lipid Technology, 22, 48. Hamm, W. (2001) Regional differences in edible oil processing procedures. 1. Seed crushing and extraction, oil movements, and degumming. 2. Refining, oil modification, and formulation, Lipid Technology, 13, 81–84, 105–109. Harris, W.S., Lemke, S.L., Hansen, S.N. et al. (2008) Stearidonic acid-enriched soybean oil increased the omega-3 index, an emerging cardiovascular riskmarker, Lipids, 43, 805–811. Hatje, G. (1989) World importance of oil crops and their products, in Oil Crops of the World: Their Breeding and Utilisation (eds G. Robbelen, R.K. Downey and A. Ashri) McGraw-Hill, New York, p. 7. Mielke, T. (ed.) (2002) The Revised Oil World 2020, ISTA Mielke, Hamburg. Mielke, T. (ed.) (2004) Oil World Annual 2004, ISTA Mielke, Hamburg. Mielke, T. (ed.) (2009) Oil World Annual 2009, ISTA Mielke, Hamburg. Mistry, D.E. (2007) Fundamental approach to price forecasting, paper presented at Globoil India, 23 September, available at http://www.seaofindia.com/articles.html, accessed October 2010. Napier, J.A. (2006) The production of n-3 long-chain polyunsaturated fatty acids in transgenic plants, European Journal of Lipid Science and Technology, 108, 965–972. Watkins, C. (2009) Oilseeds of the future. Parts 1–3, INFORM, 20, 276–279, 342–344, 408–410. Wilson, M. (2009) Trans free in America, Oils and Fats International, 25(4), 31–32.

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2

Palm Oil

Siew Wai Lin

2.1

INTRODUCTION

The oil palm (Elaeis guineensis jacquin) originated from South Africa. It was introduced to East Asia as an ornamental plant in the Bogor Botanical Garden in Java, Indonesia in 1848. The descendants spread to different parts of the world as the Deli dura and were utilised for dura × pisera (D × P) seed production. This is the main cultivated oil palm material grown in Malaysia and Indonesia. The Malaysian Palm Oil Board (MPOB), formerly known as PORIM, has the largest collection of oil palm germplasm in the world. The present planting material is mainly dura × pisera (tenera). Commercial plantings in Malaysia have been based on this D × P material as it gives the highest oil yield per bunch (22.5–25.5%). Another species of oil palm, Elaeis oleifera, originates from Central and South America. Its oil is more unsaturated, but the oil-tobunch ratio is extremely low, making it uneconomical to plant on a commercial scale. The oil palm is the most efficient oil-producing plant, with about 3.6–3.7 tonnes/ha/y of palm oil and an additional of 0.42 tonnes/ha of palm kernel oil (Gunstone 2007; Murphy 2007). The yields could be increased further with improved estate and plantation management as well as high-yielding palms. The palm bears fruit that can be harvested in the second to third year of planting in the field, and continues for about 25 to 30 years. Two types of oil are obtained from the oil palm fruit: palm oil from the mesocarp and palm kernel oil from the kernel inside the nut. Fruit bunches are harvested regularly throughout the year, following harvesting standards set by the plantations. Bunches are then transported to the palm oil mills where crude oil and palm kernels are produced by mechanical and physical extraction processes. Oil quality is maintained by careful harvesting of fruits at the optimum stage of ripeness, minimal handling of fruits during transportation, and proper processing conditions during oil extraction.

2.2 2.2.1

COMPOSITION AND PROPERTIES OF PALM OIL AND FRACTIONS Palm oil

Palm oil has a balanced fatty acid composition in which the level of saturated fatty acids is almost equal to that of the unsaturated fatty acids (Table 2.1). Palmitic acid (44–45%) and oleic acid (39–40%) are the major component acids along with linoleic acid (10–11%), Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Table 2.1

Fatty acid and triacylglycerol composition of palm oil. Malaysian (1981)*

Malaysian (1990)**

Brazilian (1993)§

Mean

Range (215 samples)

Mean

Range (244 samples)

Mean

Range (73 samples)

Fatty acids % by wt 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0

0.2 1.1 44.0 0.1 4.5 39.2 10.1 0.4 0.4

0.1–1.0 0.9–1.5 41.8–46.8 0.1–0.3 4.2–5.1 37.3–40.8 9.1–11.0 0–0.6 0–0.7

0.2 1.1 44.1 0.2 4.4 39.0 10.6 0.3 0.2

0.1–0.4 1.0–1.4 40.9–47.5 0–0.4 3.8–4.8 36.4–41.2 9.2–11.6 0–0.6 0–0.4

0.2 0.8 39.0 0.03 5.0 43.2 11.5 0.4 0.01

Tr–2.6 Tr–1.3 31.9–57.3 Tr–0.4 2.1–6.4 33.8–47.5 6.4–14.8 Tr–0.7 Tr–0.3

Triacylglycerols by carbon number C46 C48 C50 C52 C54 C56

0.8 7.4 42.6 40.5 8.8 ND

0.4–1.2 4.7–10.8 40.0–45.2 38.2–43.8 6.4–11.4 ND

1.2 8.1 39.9 38.8 11.4 0.6

0.7–2.0 4.7–9.7 38.9–41.6 37.1–41.1 10.3–12.1 0.5–0.8

Iodine Value SMP (°C)

53.3 36.0

51.0–55.3 32.3–39.0

52.1 36.7

50.1–54.9 33.0–39.0

NA NA NA NA NA NA 58.0 NA

50.3–62.9 NA

Sources: * Tan et al. (1981); ** Siew et al. (1990); § Tavares and Barberio (1995). Key: ND = not detectable NA = not available SMP = slip melting point

although only a trace amount of linolenic acid is present. The low level of linoleic acid and the virtual absence of linolenic acid make the oil relatively stable to oxidative deterioration. Malaysian palm oil has a narrow compositional range, as indicated from several surveys carried out between 1977 and 1997. The earliest surveys for crude palm oil were recorded by Chin and co-workers (1982) on 215 samples and for both crude and refined oils by Tan and Oh (1981a). King and Sibley (1984) carried out a survey on oils collected from different geographical locations (Malaysia, Ivory Coast, Nigeria, Papua New Guinea, the Solomon Islands and Sumatra). In terms of fatty acid composition, iodine value (IV) and slip melting point (SMP), there are generally no major differences between the oils obtained from the different locations. The iodine values range from 50 to 55. Brazilian palm oil appears to be more unsaturated, containing an average of 43.2% oleic and 11.5% linoleic acids with an IV of 58 (Table 2.1). Iodine values range from 50 to 63 (Tavares and Barberio 1995). Elias and Pantzaris (1997) considered that the oils reported by Travares and Barberio were rather unusual in the wide range for palmitic acid (32–57%) and oleic acid (34–47%) and concluded that the oil in the survey consisted of ‘mixtures of oil of Elaies oleifera with various proportions of stearin’. This would account for the high levels of palmitic acid noted at the maximum end of the range (57.3%) and relates to the fact that the authors had already rejected 26 out of 99 samples as being adulterated.

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Palm Oil

Table 2.2

Fatty acid composition of palm oil from E. guineensis, E. oleifera and their hybrid.

Fatty acids (wt %)

12:0 14:0 16:0 16:1 18:0 18:1 18:2 Others Iodine value

27

E.guineensis (Eg)

0.3 1.2 44.3 – 4.3 39.3 10.0 0.6 55.0

E. oleifera (Eo)

Eg × Eo

Mean

Range

Mean

Range

– 0.2 18.7 1.6 0.9 56.1 21.1 1.0 85.0

– 0.1–0.3 14.4–23.0 NA 0.6–1.8 55.8–64.0 16.2–22.5 NA NA

– 0.5 32.2 0.2 3.2 51.8 10.8 0.9 67.5

– 0.1–0.5 22.4–44.7 NA 1.6–4.9 36.9–60.1 8.8–16.8 NA NA

Sources: Rajanaidu et al. (1985, 2000). Key: NA = not available

It is of interest to mention here that oils from the Elaeis oleifera (South American palm) have oleic acid content as high as 55–64% and linoleic acid content from 16–23% (Rajanaidu et al. 1985). Elaeis oleifera, also known as Elaeis melanococca, can be easily hybridised with Elaeis guineensis, producing oil with characteristics that are between those of the parent oils (Table 2.2). Composition of the oil from the Nigerian population of E. guineensis shows a much larger variation than the commercial oils from planted material. Palmitic acid ranges from 27% to 55%, oleic acid from 28% to 56% and linoleic acid from 6.5% to 18%. These materials provide oil palm breeders with genetic material for developing palms with specifications such as high oleic acid, carotenes or tocopherols. The TAG profile of palm oil has been characterised by carbon number using gas chromatography (Table 2.1). The TAG of palm oil consists of C46 to C56 molecules in a near normal distribution, the major TAGs being C50 and C52. The carbon number represents the number of carbon atoms in the three acyl chains and excludes the glycerol carbon atoms. A more detailed profile of the TAGs is seen in Table 2.3. Palm oil has high contents of disaturated (POP and PPO) and monosaturated (POO and OPO) TAGs. The fatty acids at the sn-2 position of the TAGs are mainly unsaturated (oleic) (Ong and Goh 2002). The polymorphic behaviour of a fat is determined to a large extent by the fatty acids within the TAGs. Fats that are composed of fatty acids predominantly of a single chain length are most likely to be stable in the β form (De Man 1992). Palm oil, containing C16 and C18 acids in most of its glycerol esters, is highly stable in the β′ form. The appreciable amounts of disaturated (POP and PPO) and monosaturated TAGs (POO, OPO and PLO) are apparent as high-melting and low-melting fractions in the differential scanning calorimetry (DSC) thermograms. Three sub-endo peaks observed between 3 °C and 8 °C are linked to the presence of monounsaturates, SUS and diunsaturates, SUU glycerol esters (Braipson-Danthine and Gibon 2007). The two main endo peaks are associated with glycerol esters, which are easily separated into palm olein and palm stearin. Figure 2.1 shows the products obtained from multiple fractionation of palm oil. A wide range of fractions with different properties to suit the requirements of the food industry is available through dry fractionation.

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0.2–0.9 1.3–3.4 0.2–1.0 1.3–2.3 9.0–11.2 6.5–11.0 3.3–6.6 20.5–26.2 27.1–31.0 0.7–7.2 1.0–3.6 4.6–5.9 0.1–1.8 0.1–1.4 3.0–7.6

Range

0.05 2.8 0.6 2.3 11.8 9.9 4.5 26.8 26.6 ND 3.3 4.7 0.07 0.16 5.3

Mean

0.5–0.6 2.3–3.2 0.5–0.7 1.7–2.6 10.9–13.0 9.6–10.2 4.2–5.2 25.1–29.0 23.4–29.4 ND 3.0–3.9 3.9–5.2 0.1–0.3 0.2–0.6 4.7–6.1

Range (n=12)

Palm olein (IV<60)**

Sources: * Tan et al. (1997); ** Siew and Chong (1998); § Siew, unpublished. Key: ND = not detectable Note: Symbols such as PLO refer to all the triacylglycerols with these three acyl chains.

0.5 2.5 0.6 1.7 9.9 9.5 4.3 22.8 29.0 5.4 2.5 5.1 1.0 0.5 4.9

Mean

Palm oil*

Triacylglycerol (TAG) composition of palm oil products.

OLL PLL MLP OLO PLO PLP OOO POO POP PPP SOO POS PPS SOS Diacylglycerols (wt %)

TAG (wt %)

Table 2.3

0.7 3.4 0.7 2.6 13.6 9.8 5.1 30.2 19.1 ND 4.2 3.6 0.2 0.4 6.4

Mean

0.6–0.8 3.2–3.7 0.6–0.8 2.2–3.0 12.9–14.9 9.0–10.2 4.6–6.1 28.4–32.5 16.1–20.7 ND 3.4–6.9 2.9–4.8 0.1–0.3 0.2–0.5 5.6–6.9

Range (n=7)

Palm olein (IV 60–64)**

0.8 3.7 0.6 3.0 15.4 8.4 6.1 34.5 12.8 ND 4.5 2.5 0.2 0.2 7.1

Mean

0.7–0.8 3.3–4.1 0.6–0.7 2.3–3.3 15.0–17.3 7.9–9.7 5.0–6.8 33.4–35.7 9.0–17.0 ND 3.9–6.3 1.9–3.5 0.1–0.3 0.1–0.4 6.2–8.6

Range (n=5)

Palm olein (IV 65–67)**

0.3 1.8 0.4 1.3 7.1 8.3 2.3 16.7 29.8 18.6 – 4.8 3.6 0.6 4.5

Stearin IV 38.0§

0.5 2.3 0.5 1.7 8.4 9.4 2.7 18.4 30.9 12.5 – 5.4 2.7 0.6 4.0

Stearin IV 45.8§

0.1 0.4 – 0.2 1.7 3.5 3.8 5.0 13.6 59.6 – 2.4 8.0 – 1.1

Stearin IV 11§

Palm Oil

29

Super stearin IV 17–21

Hard stearin IV 32–36 Soft stearin IV 40–42 Palm oil

Hard PMF

IV 51–53 IV 32–36 Soft PMF IV 42–48 Olein

Recycling

‘Oleins’

IV 57–59 Super olein IV 60–66 Top olein IV 70–72 Figure 2.1 Dry multiple fractionation of palm oil. The fraction designated hard stearin is more commonly named stearin or palm stearin. Source: Adapted from Deffense (1995), with permission.

2.2.2

Palm olein

Palm oil, semi-solid at ambient temperature (25–30 °C), may be fractionated into a liquid fraction (olein) and a solid fraction (stearin). The olein contains higher levels of oleic (39– 45%) and linoleic (10–13%) acids compared to palm oil (Table 2.4). Palm olein remains clear at an ambient temperature of 25 °C. Further fractionation of the olein produces more unsaturated fractions, often called super-olein or double fractionated olein. These have higher levels of oleic and linoleic acids, ranging from 43–49% and 10–15% respectively, resulting in IVs of 60–67 (Tang et al. 1995), and have lower cloud points of about 2–5 °C. In contrast, oleins with IV less than 60 have cloud points of 6–10 °C. As the iodine value increases, the cloud point decreases, though not linearly. A cloud point of below 0 °C can only be obtained with an olein of IV above 70. The palmitic acid content should be below 35%, and preferably below 31%, for palm olein to remain clear at 10 °C. Fractions with iodine values above 70 and cloud points of −4 °C (Deffense 1995) are described as top-oleins. This olein can satisfy the cold test for a salad oil where the oil must remain clear after 5.5 hours at 0 °C. The clarity of single- and double-fractionated palm oleins has been thorougly discussed by Nor Aini and Hanirah (1996, 1997).

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Table 2.4 Fatty acid and triacylglycerol composition of palm olein (adapted from Deffense, 1995, with permission). Palm olein (IV <60)*

Fatty acid composition (wt. %) 12:0 14:0 16:0 18:0 18:1 18:2 18:3 20:0 Iodine value Slip melting point (°C) Triacylglycerols by carbon number (wt %) C44 C46 C48 C50 C52 C54 C56

Super olein (IV >60)**

Top olein (IV 70–72)§

Mean

Range (n = 12)

Mean

Range (n = 32)

n=1

0.3 1.1 40.9 4.2 41.5 11.6 0.4 0.4 56.8 21.5

0.2–0.4 0.9–1.2 36.8–43.2 3.7–4.8 39.8–44.6 10.4–12.9 0.1–0.6 0.3–0.5 55.6–61.9 19.2–23.6

0.3 1.0 35.4 3.8 45.1 13.4 0.3 0.3 61.9 15.1

0.2–0.4 0.9–1.1 30.1–37.1 3.2–4.3 43.2–49.2 10.7–15.0 0.2–0.6 0.0–0.4 60.1–67.5 12.9–16.6

– 1.0 28.8 2.5 52.0 14.6 0.4 0.2 70–72 NA

0.1 0.8 3.3 39.5 42.7 12.8 0.7

0.0–0.5 0.4–1.4 2.4–3.9 37.9–40.9 41.9–43.7 11.8–13.5 0.5–1.1

ND 0.2 1.9 30.8 53.4 13.6 0.2

ND 0.1–0.2 1.7–2.6 23.0–34.2 50.2–59.6 11.6–15.9 0.1–0.4

NA NA NA NA NA NA NA

Sources: * Siew et al. (1990); ** Tang et al. (1995); § Deffense (1995). Key: ND = not detectable NA = not available

The differences in TAG composition between olein with IV not exceeding 60 and those above 60 are detailed in Table 2.3. The major differences are for levels of PLO (mean values of 11.8% and 13.6% respectively), POO (26.8% and 30.2%) and POP (26.6% and 19.1%). Put another way, SUU glycerol esters rise from 44.7 to 51.4% and SUS glycerol esters fall from 42.0 to 33.6%. (S and U represent saturated and unsaturated acyl groups). The ratio of POP/POO influences the crystallisation of palm oil, as shown in Table 2.5. Saturated TAGs such as PPP, MPP and PPSt act as seeds in crystallisation (Mohd Zaki et al. 1997). Other crystallisation inducers are diacylglycerols such as dipalmitoylglycerol. Siew and Ng (1996a, b) found a high concentration of 1,3-dipalmitoylglycerol in crystals of palm olein obtained after tempering the olein through an alternating temperature cycle of 28 °C and 10 °C. It is notable that diacylglycerols are preferentially distributed into the olein phase during fractionation and that higher concentrations of diacylglycerols are found in more unsaturated oleins. The content of unsaturated acids in superolein is about 59%, compared to only 53% in the single-fractionated olein. At 5 °C, solid fat contents of superolein of IV 62 and above are around 5%, while oleins of IV 59–61 have solids between 30 and 50% (Tang et al. 1995). To remain clear at lower temperatures the IV of olein has to be 62 and above.

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Palm Oil

Table 2.5

31

Nucleation behaviour of palm oleins.

IV of olein

POP/POO ratio

Nucleation test (11 °C)

59.3 ± 3.0 61.4 ± 2.9 63.6 ± 2.8

0.89 ± 0.24 0.83 ± 0.22 0.56 ± 0.20

<1 hr 1–6 hrs >6 hrs

Source: Siew and Ng (1996a, b).

Table 2.6

Fatty acid and triacylglycerol composition of palm stearin and palm mid-fraction. Stearin* n = 150

Soft stearin* n=1

Palm mid-fraction** n = 39

Fatty acid composition (wt %) 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0

0.1–0.6 1.1–1.9 47.2–73.8 0.05–0.2 4.4–5.6 15.6–37.0 3.2–9.8 0.1–0.6 0.1–0.6

0.1 1.1 49.3 0.1 4.9 34.8 9.0 0.2 0.4

0–0.3 0.8–1.4 41.4–55.5 – 4.7–6.7 32.0–41.2 3.6–11.5 0–0.2 0–0.6

Iodine value

21.6–49.4

46.7

34.5–54.8

SMP (°C)

44.5–56.2

47.7

24.3–44.9

Triacylglycerols by carbon number (wt %) C46 C48 C50 C52 C54 C56

0.5–3.3 12.2–55.8 33.6–49.8 5.1–37.3 TR–8.4 ND

1.2 15.3 42.7 33.4 7.4 ND

0–1.6 1.4–11.3 45.5–73.9 19.4–42.0 1.7–8.5 0–0.9

Sources: * Tan et al. (1981); ** Tan and Oh (1981b). Key: ND = not detectable TR = trace SMP = slip melting point

2.2.3

Palm stearin

Palm stearin, the harder fraction of palm oil, contains more saturated fatty acids and TAGs. The comprehensive survey of fractionated products of palm oil (Tan and Oh 1981b) indicated a wider compositional range for stearin, in contrast to olein (Table 2.6). This wide IV range (21–49) is reflected in the slip melting points (44–56 °C). The palmitic acid content of the stearins varies from 47% to 74%, while oleic acid ranges from 15% to 37%. The authors, who found that the distribution was rather skewed, did not compute the mean values. A later survey (Siew et al. 1990) found palmitic acid in the range of 49% to 68% and

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Mean

Range

Mean

46.1–60.8 33.4–50.8 21.6–31.3 12.1–20.7 6.1–14.3 3.5–11.7 0.0–8.3

38.3 19.9 5.7 2.1

23.9–45.5 10.7–25.9 0–9.0 0–4.3

17.5 0.9

0–26.3 0–9.0

1.4631–1.4641 (at 30 °C) 0.9042–0.9054 (at 30 °C)

Range

32

Super olein**

Sources: * Siew et al. (1992, 1993); ** Tang et al. (1995); § Tan and Oh (1981a, b); † Deffense (1995). Key: NA = not available

53.7 39.1 26.1 16.3 10.5 7.9 4.6

Solid fat content by nuclear magnetic resonance

Temperature (°C) 10 15 20 25 30 35 40 45 50 55

Mean

238

Palm olein*

1.4544–1.4550 1.4589 1.4589–1.4592 1.4634 (at 50 °C) (at 40 °C) 0.8896–0.8910 0.8972 0.8969–0.8977 0.9046 (at 50 °C) (at 40 °C)

Range

244

Palm oil*

76.0 68.9 60.2 50.6 40.4 34.3 28.1 22.4 12.5 0.6

49.5–84.1 37.2–79.0 25.2–71.2 15.8–63.5 11.2–55.0 7.2–46.6 6.1–38.0 0–32.2 0–21.3 0–9.1

10 15 20 25 30 35 40

75.0 64.0 45.0 11.0

NA

NA

52.7–90.6 40.0–85.0 10.3–73.1 0–24.9 0–20.2 0–15.3 0–7.8

NA

Soft

95.0 93.0 90.0 78.0 47.0 6.0

NA

NA

Hard

Palm mid-fraction†

NA

Range

39

Palm midfraction§

Mean

1.4493 1.4482–1.4501 NA (at 60 °C) 0.8822 0.8813–0.8844 NA (at 60 °C)

Range

205

Palm stearin*

Mean

Physical properties of palm oil and its fractions (adapted from Deffense, 1995, with permission).

Refractive 1.455 index Apparent density 0.8899 (g/ml)

No. of samples

Table 2.7

Palm Oil

33

oleic acid between 24% and 34%. Samples in the 1981 survey were from dry, detergent and solvent processes, while samples from the later survey were generally dry, fractionated types. Due to the higher cost of operations, detergent and solvent fractionations are no longer popular processes. A much harder stearin is also available with 79% palmitic acid. This stearin has a tripalmitoyl glycerol (PPP) content of 60% and is used as hard stock for soft margarines as well as in infant fat formulas. Advances in crystalliser design, cooling programmes and filtration technology have enabled a wider range of stearins to be produced. Another stearin, produced from a second fractionation of the olein, is called palm mid-fraction (Figure 2.1). This oil contains high C50 (POP) TAG (Table 2.6) and is utilised in the manufacture of a cocoa butter equivalent. Tan et al. (1981a, b) characterised palm mid-fractions and proposed the following specifications: ratio of C50/C48+C54 of 4 minimum, C52 TAGs content 43% maximum, IV of 32–55 and slip melting point of 23–40 °C. The IV and slip melting point ranges, though representative of mid-fractions, were too wide to represent goodquality palm mid-fractions. The SUS (87%) and SSS (4.2%) molecules are much higher in hard PMF compared to the softer PMF (1.4–1.6% SSS and 65.6–71.9% SUS) (BraipsonDanthine and Gibson 2007). Palm mid-fraction is often refractionated with solvent to further enrich the POP esters. Dry fractionation processes are also currently available that can produce high-quality palm mid-fractions (Tan 2001). The use of high-pressure membrane filtration has helped to improve the quality of palm mid-fractions. Products of IV around 33–35, which previously were only available through solvent fractionation, can now be produced through dry fractionation.

2.3 2.3.1

PHYSICAL CHARACTERISTICS OF PALM OIL PRODUCTS Palm oil

Palm oil is semi-solid at room temperature (28 °C), the melting point range being from 32–40 °C. The slip melting point, commonly adopted for measuring this parameter, is affected by the content of free fatty acids and diacylglycerols and crude oils have slightly higher slip melting point than refined oils. The solid fat content of a fat determines its applications and usage. In palm stearin solids are detectable from 10 °C up to 50 °C (Table 2.7). At 10 °C the solid content amounted to about 50%, reducing to half of this value at 20 °C. The variation observed between samples arises from differences in fatty acid and TAG compositions as well as in the levels of diacylglycerol in the oil. Siew and Ng (1999) observed that 10% of added diacylglycerol reduces the solids content by 20%. The melting and crystallisation characteristics of the oil can be followed using the DSC technique (Braipson-Danthine and Gibon 2007). Both the melting and cooling thermograms show two main endotherms/exotherms representative of the high and low melting fractions of the oil. From these thermograms, it is clear that palm oil is an excellent oil for fractionation. Suitable cooling programmes produce oleins and stearins of different composition to suit market requirements. The fact that palm oil crystallises in the β′ form helps in the fractionation and filtration process as large crystals are formed, enabling ease of filtration. Other physical characteristics such as refractive index and apparent density of the oil are as given in Table 2.7.

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Table 2.8

Cold stability of palm olein at 5–20 °C.

Iodine value

Single-fractionated palm olein 56

Cloud point (°C) Temperature (°C) 5 10 15 20

58

62

Double-fractionated palm olein 60

62

65

67

8.3

6.3

3.5

4.5

4.0

2.0

1.5

<3 hr <3 hr <3 hr >5 hr <1 d

<3 hr <3 hr <3 hr >5 hr <1 d

<3 hr >5 hr <1 d >1 d >20 d

<3 hr <3 hr <1 d <1 d

<3 hr 1d <4 d <4 d

<5 hr <2 d <7 d >60 d

<5 hr 1d <5 d >60 d

Sources: Nor Aini and Hanirah (1996, 1997). Key: hr = hour d = day Note: The times indicate how long the oil remains clear at each temperature.

2.3.2

Palm olein

Palm olein is the liquid fraction of palm oil and is clear at a room temperature of 25 °C. Its clarity depends on IV, TAG composition and diacylglycerol content. Table 2.8 shows the cold stability of palm olein in relation to its IV (Nor Aini et al. 1993). The clarity of the olein can be significantly affected by the diacylglycerol content, as shown in Table 2.9. Diacylglycerols derived from palm oil affect the cold stability of palm olein. While dipalmitoyl glycerol causes rapid crystallisation of the olein, other diacylglycerols such as palmitoyl oleoyl glycerol (PO) and dioleoyl glycerol (OO) do not significantly affect the cold stability (Siew and Ng 1996b). The physical characteristics of palm olein are closely related to its chemical composition. Solid fat contents are low, 37% at 10 °C for normal olein and only 17% for super oleins (Table 2.7). At 25 °C, most oleins are completely liquid. According to Tang et al. (1995), superoleins fall into two categories: those with IV below 61.5 have higher solids of 40–52% at 2.5 °C and 31–42% at 5 °C, while oleins with IVs exceeding 61.5 have a much lower solid fat content of 0.5–17% at 2.5 °C and 0–16% at 5 °C. Thus improved cold stability can be expected with such higher-IV oils.

2.3.3

Palm stearin

Palm stearin, the more saturated fraction of palm oil, is more variable in composition and thus in physical characteristics. The wide range in solid fat content (Table 2.7) is consistent with the wide range in IV for this fraction. The variation in composition allows food manufacturers a wide choice of materials for their formulations. In fact, many product formulations require some solid fat to provide the solids required at a certain temperature range. Palm stearin fits the role of providing the required solids by correct blending with unsaturated vegetable oils. The crystallisation and melting behaviour of palm stearin depend on the composition. Figures 2.2 and 2.3 show the behaviour of different palm stearins. PMF shows crystallisation exotherms, which overlap into several peaks, while its melting thermogram shows a main endotherm with a shoulder, finally melting at 31 °C. The two other stearins of IV 35

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Table 2.9

35

Effect of added diacylglycerols (DAG) on the crystallisation of palm olein at 5 °C.

Percentage of DAG

Olein IV 58.1* 0.0 0.5 1.0 1.5 2.0 2.5 5.0 7.5 10.0 Olein IV 62.8** 0.0 0.5 1.0 1.5 2.0 2.5 5.0 7.5 10.0

Crystallisation time (min) PDG§

1,2-PP

1,3-PP

3.9 1.9 1.9 1.9 1.9 1.9 1.4 1.4 1.4

3.9 1.7 0.8 0.7 0.7 0.6

3.9 1.2 0.8 RT† RT RT

35.0 36.0 33.5 17.5 12.5 9.0 2.0 1.3 1.3

35.0 8.5 2.1 1.4 1.4 1.4

35.0 1.9 RT RT RT RT

1,2-PO

1,3-PO

1,2- OO

1,3- OO

3.9 2.5 2.6 2.8 3.0 3.0

3.9 2.5 2.3 2.3 2.3 2.0

3.9 2.7 2.7 3.0 3.0 3.0

3.9 2.3 2.3 2.4 2.8 3.3

35.0 37.5 37.5 37.5 40.5 45.0

35.0 38.0 38.0 38.5 42.0 45.0

35.0 29.5 29.5 29.5 29.5 29.5

35.0 29.5 29.5 29.5 29.5 29.5

Source: Siew and Ng (1996a, b). Notes: * LSD (P<0.05) 0.7 (5 replicates). ** LSD (P<0.05)1.31(5 replicates). § PDG refers to diacylglycerols extracted from palm oil. † RT, crystallise at room temperature (28 °C).

and 44 have different melting and crystallisation profiles, although both still have considerable proportions of the more unsaturated TAGs. The pattern of polymorphic transformations in both stearins is generally quite similar in nature. For the stearin of IV 35, an additional higher melting fraction is observed that results in the oil melting at 55 °C. In contrast, the hard stearin (IV 12) shows only one exotherm and one endotherm in their crystallisation and melting thermograms, indicating that the lowermelting fractions have been removed during fractionation. It is obvious from the figures that the melting and crystallisation behaviours of palm stearins vary greatly. An understanding of the properties and behaviour of different stearins is needed to allow full exploitation of its usage and application in food products.

2.4

MINOR COMPONENTS OF PALM OIL PRODUCTS

Crude palm oil is rich in minor components such as carotenoids, tocopherols, tocotrienols, sterols, phospholipids, triterpene alcohols, squalene, aliphatic alcohols and aliphatic hydrocarbons (Goh et al. 1985). The major components of interest are the carotenes, tocopherols, tocotrienols, sterols and squalene (Figure 2.4 and Table 2.10). Carotenes and tocopherols are antioxidants and stabilise the oil against oxidation. During refining, the bleaching and

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17.6

21.9 60.7

PMF

Heat flow, W/g

31.3

Stearin IV 11 15.2

–4.7

8.4 4.1 5.4

43.7

63.2

22.6 41.0 52.2

Stearin IV 45

–4.3

30.6

13.7 0.9 6.9

42.5 25.5

3.6 47.0 55.5

Stearin IV 35 15.4 –30.0

–10.0

10.0

30.0

50.0

70.0

Temperature (8C) Figure 2.2 Melting thermogram of palm stearin. Sample was cooled to –30 °C, at 40 °C/min, held for 10 mins and heated to 80 °C at 5 °C/min. Source: Siew, unpublished data.

steam-deodorisation processes remove partially some of these valuable components. The amounts retained in the refined oils depend on the conditions of refining.

2.4.1

Carotenes

The dark reddish-orange colour of oil palm fruit is due to its high concentration of carotenoids and anthocynanins. Crude palm oil, extracted commercially by sterilisation and pressing, contains 400–1000 ppm of carotenoids. This variation results from process conditions, species of oil palm and level of oxidation. The carotenoids in palm oil are mainly α- and β-carotene with lower levels of phytoene, phytofluene, cis β-carotene, cis α-carotene, δ-carotene, γ-carotene, ζ-carotene, neurosporene, β-zeacarotene, α-zeacarotene and lycopene (Table 2.11) (Yap et al. 1991; Jalani et al. 1997).

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Palm Oil

37

PMF 2.4 11.2 12.7 6.5 8.0

Heat flow, W/g

Stearin IV 11

Stearin IV 45

8.9

–6.8

20.2 4.8

36.8 8.4

–6.6

Stearin IV 35

3.5

29.3 –30.0

–10.0

10.0

30.0

50.0

70.0

Temperature (8C) Figure 2.3 Crystallisation thermogram of palm stearins of different IV. Sample was melted to 80 °C and cooled to –30 °C at 5 °C/min. Source: Siew, unpublished data.

The carotenoid profiles of crude olein and stearin are similar to that of the crude oil. All three contain neurosporene, α-, β-, γ-carotenes and lycopene, with α-carotene and β-carotene as major components. The crude oil obtained from the tenera variety of Elaeis guineensis has a carotene content of 500–700 ppm (Table 2.11), while that of Elaeis oleifera is about 4600 ppm. The carotene content of hybrid palms, produced from the cross of the two species, lies between those values. Second-pressed oils (Table 2.12), obtained by double pressing of palm fruits, have a much higher concentration of carotenoids (1800–2400 ppm) (Choo 1994, 1995). Physically refined oils show no trace of the carotenoids. These are either absorbed onto the bleaching earths or destroyed during thermal treatment. Carotenes preferentially concentrate in the more unsaturated olein fraction, leaving little in the stearin fraction. This has important consequences for the oxidative stability of these two fractions, with the unsaturated olein being more stable than the more saturated stearin.

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38

β-Carotene (C40H56) Other carotenes vary in the nature of the (cyclic) end groups R HO

5 78

R

O R

Tocopherols and tocotrienols Tocopherols have a saturated C16 side chain, tocotrienols have double bonds at the three positions indicated by the arrows. R = H or CH3 α = 5,7,8-trimethyltocol, β = 5,8-dimethyltocol, γ = 7,8-dimethyltocol, δ = 8-methyltocol. HO O a-tocomonoenol

Squalene (C30H50) O MeO

H

MeO O

10

Ubiquinone (C59H90O4) Figure 2.4 Minor components present in palm oil products.

Crude palm oil has been consumed in some countries as a source of vitamin A. To retain these carotenes in the oil, either molecular distillation (Ooi et al. 1992) or chemical neutralisation followed by modified refining is currently used to produce a nutritionally valuable red palm oil. This red oil is currently available as a cooking oil or health supplement. In crude palm oil, the carotene content provides an indication of quality, as shown by the use of DOBI, an index for determining the bleachability of palm oil (Swoboda 1982). Oils from a particular oil palm species will have carotene values within a narrow range and any

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Palm Oil

Table 2.10

39

Minor components of crude and refined palm oil.

Minor components Carotenoids (Jacobsberg 1974) Tocopherols and tocotrienols (Abdul Gapor et al. 1981) Sterols (Rossell et al. 1983) (Siew 1990) Ubiquinone (Hazura et al. 1996) Squalene (Goh and Gee 1984) (Abdul Gapor and Hazrina 2000) Phospholipids (Goh et al. 1982) Triterpene alcohols (Itoh et al. 1973a) Methyl sterols (Itoh et al. 1973b) Aliphatic alcohols (Jacobsberg 1974)

Crude oil (ppm)

Refined oil (ppm)

500–700 600–1000

ND 350–630

326–527 210–620 10–80 200–500 421–979 5–130 40–80 40–80 100–200

NA 70–316 10–70 NA 184–791 NA NA NA NA

Key: ND = not detectable NA = not available

Table 2.11

Composition of carotenoids in palm oil, given as % of total carotenoids.

Type Phytoene Cis β-carotene Phytofluene β-carotene α-carotene Cis-a-carotene ζ-carotene γ⋅-carotene δ-carotene Neurosporene β-Zeacarotene α-Zeacarotene Lycopene Total (ppm)

E.guineesis (Eg)

E.oleifera (Eo)

Eg × Eo hybrid

1.27 0.68 0.06 56.02 35.06 2.49 0.69 0.33 0.83 0.29 0.74 0.23 1.30

1.12 0.48 trace 54.08 40.38 2.30 0.36 0.08 0.09 0.04 0.57 0.43 0.07

1.83 0.38 trace 60.53 32.78 1.37 1.13 0.23 0.24 0.23 1.03 0.35 0.05

500–700

4300–4600

1250–1800

Sources: Jalani et al. (1997); Yap et al. (1991).

Table 2.12

Carotene content in palm oil fractions.

Type of oil

ppm

Crude palm oil (E.guineesis, tenera) Crude palm olein Crude palm stearin Residual oil from fibre Second-pressed oil

500–700 600–760 380–540 4000–6000 1800–2400

Source: Choo (1995).

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Red lovibond units

14 12 10 8 6 4 2 0 0

1

2

3

4

Deterioration of bleachability index (DOBI) Figure 2.5 Correlation between DOBI and colour of refined oils. Source: Siew, unpublished data.

dramatic lowering of carotene is due to degradation of the oil. Good-quality oils not only have high carotene values, but also low secondary oxidation characteristics, as measured by absorption at 269 nm. The DOBI value, which is the ratio of the absorbance at 446 nm (measurement of carotene) to 269 nm (measurement of oxidation), is well correlated to the colour remaining in the refined palm oil (Figure 2.5). Oils with low DOBI values, due to low carotenes and high secondary oxidation values, are difficult to refine. Palm carotenoids provide a source of pro-vitamin A and its orange-red colour is useful as a natural pigment for food preparations, margarines, biscuits and confectionery. Besides providing a source of vitamin, palm carotenoids have better bioactivity and protective effect against diseases than β-carotene alone (Stahl and Sies 2005).

2.4.2

Tocopherols and tocotrienols (tocols)

Crude palm oil, besides being rich in pro-vitamin A, has a high content of vitamin E, present as tocopherols and tocotrienols (Abdul Gapor 1990; Abdul Gapor et al. 1988), of which 70% are tocotrienols (Hashimoto et al. 1980). (See Figure 2.4, Table 2.13 and Table 2.14.) A new ‘vitamin E’ (α-tocomonoenol) was detected and identified by Matsumoto et al. (1995) and further examined during physical refining (Puah et al. 2007). The new vitamin E compound is probably a biosynthetic intermediate in the reduction of α-tocotrienol to α-tocopherol. Crude palm olein has a higher content of tocopherols and tocotrienols than palm oil. Refined oils retain up to 70% of the tocols, depending on the conditions of refining. Most loss occurs at deodorisation and consequently palm fatty acid distillate (PFAD) has as much as 5–10 times the level in crude oil. PFAD is a valuable source of raw material for recovery of the physiologically active tocols. This product is known loosely as ‘palm vitamin E’, though strictly vitamin E is α-tocopherol. There is considerable interest in the nutritional and physiological properties of the tocols in palm oil, particularly the tocotrienols. Table 2.14 shows the composition of tocopherols and tocotrienols in palm oils of different oil palm materials. Most is in the form of γ-tocotrienols, in contrast to that of other vegetable oils where α- tocopherol (vitamin E) predominates. According to Abdul Gapor (1990) the order of antioxidant activities of tocotrienols was γ-tocotrienol > δ-tocotrienol > α-tocotrienol. γ-Tocotrienol has twice the antioxidant effect of α-tocotrienol.

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Palm Oil

41

Table 2.13 Tocol content (total tocopherols and tocotrienols) in palm oil products. Type of oil

Total ppm

Crude palm oil* Refined palm oil* Crude palm olein* Refined palm olein* Crude palm stearin* Refined palm stearin* Palm oil fatty acid distillate** Palm olein fatty acid distillate** Palm stearin fatty acid distillate**

708–1141 378–890 880–1129 559–902 426–552 348–381 744–8192 1018–7172 162–2408

Sources: * Abdul Gapor (1990); ** Abdul Gapor et al. (1988).

Table 2.14 Composition of tocopherols and tocotrienols (% of total) in palm oils and fatty acid distillate. Type of material

a-tocopherol

a-tocotrienol

g-tocotrienol

Crude palm oil* E. guineesis (Eg) E.oleifera (Eo) Eg × Eo Palm fatty acid distillate**

21 15 19 21

23 27 28 16

45 54 42 39

d-tocotrienol 11 4 11 24

Total ppm

600–1000 700–1500 600–1600 744–8192

Sources: * Jalani et al. (1997); ** Abdul Gapor et al. (1988).

Tocotrienols have become a focus of research in recent years because of new findings showing their high efficacy in protecting against heart-related diseases (Serbinova et al. 1993), including lowering of cholesterols (Quereshi et al. 1991), and against certain cancers. The tumour-protective effect of tocotrienols from palm oil was demonstrated by Komiyama and Yamoka (1993), Nesaretnam et al. (1995), Guthrie et al. (1997), Nesaretnam (2008) and others. The mechanisms were fourfold, being anti-angiogenesis (preventing blood vessel growth and thus the growth and proliferation of cancer cells), anti-proliferation, apoptosis induction and improved immunology. α-Tocotrienol, γ-tocotrienol and δ-tocotrienol have emerged as the more potent forms of vitamin E for health and disease prevention (Sen et al. 2007; Nesaretnam et al. 2007). Readers are recommended to check the latest literature for new work in this emerging science of tocotrienols.

2.4.3

Sterols, squalene and other hydrocarbons

Another major component group of the unsaponifiable fraction of palm oil are the phytosterols. The common phytosterols found in palm oil products are sitosterol, stigmasterol campesterol and cholesterol. Crude palm oil contains 210–620 ppm of phytosterols (Table 2.15) (Siew 1990). Fractionation and refining change the content and composition of the phytosterols in the oil and its fractions. Again, palm fatty acid distillate is a good source of phytosterols, having 1500–20 000 ppm with an average of 6500 ppm (Abdul Gapor et al. 1988). In the extraction of palm tocotrienols, the process involves a purification step that results in a concentrate high in the phytosterols. Fernandes and Cabral (2007) provide a good review of the recovery methods for phytosterols.

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Table 2.15

Sterol content and composition of palm oil products. Cholesterol Campesterol Stigmasterol b-Sitosterol ppm ppm ppm ppm

Type of oil

Crude palm oil* Crude palm oil** Refined palm oil* Crude palm olein* Refined palm olein* Palm stearin§ Palm fatty acid distillate†

2.7–13

46.4–150

7–13

90–151

1.2–5.5

15.3–65.4

6.2–7.5

26.3–65.7 44–66

Others¶ ppm

Total sterols ppm

120–369.5

2–21

210–620

218–370

2–18

326–527

8.5–36.9

45–198

0–10.5

70–316

56.7–103.8

29.9–51.0

149–253

24.6–28.1

270–440

2.1–2.4

25.6–30.4

12.4–23.3

67.7–11.4

0–1.2

2.7–4.9 11

20.6–24.2 23

11.4–11.8 14

56.7–58.4 52

2.9–6.0 –

Sources: * Siew 1990; ** Rossell et al. 1983; § Downes 1982; as percentage of total sterols). Note: ¶ Mixture of Δ5-Avenasterol, Δ7-Stigmastenol, Δ7-Avenasterol.

†

109–170 389–481 1536–19 811

Abdul. Gapor et al. 1988 (composition is expressed

The C30 hydrocarbon squalene (Figure 2.4) is present at about 200–500 ppm in crude palm oil; sesquiterpene (C15) and diterpene (C20) hydrocarbons are present at lower levels. Abdul Gapor and Hazrina (2000) reported squalene as high as 979 ppm in some crude oils and 791 ppm in refined oils. These levels are generally higher than those of other vegetable oils, with the exception of olive oil. Palm fatty distillate has 5000–8000 ppm of squalene. Crude palm oil also has 10–80 ppm of ubiquinone 10 (Figure 2.4) (Hazura et al. 1996).

2.5

FOOD APPLICATIONS OF PALM OIL PRODUCTS

Palm oil is the vegetable oil produced and traded in the largest amounts and detailed figures are given in Chapter 1. Statistics from USDA-FAS reports show that in 2000/01 over 80% of palm oil produced was used as food. However, the figures dropped to 75% in 2006/07, due to increasing usage as a biofuel (Gunstone 2007). A large variety of possible product formulations can be made from either palm oil or its fractions, sometimes in combination with palm kernel oil/fractions or with other vegetable oils. With very little polyunsaturated acids palm oil is oxidatively stable. Being naturally semi-solid in nature, there is little necessity for hydrogenation.

2.5.1

Cooking/frying oil

Palm olein is much utilised as a cooking oil in homes and in industrial outlets. Palm oil and its fractions are accepted as frying oils for food products such as snack chips, crackers, cookies, pastries, doughnuts, fries and instant noodles. A comprehensive review of palm oil products in frying applications has been documented by Berger (2007). Frying, being a thermal process carried out in air, generally results in a rapid deterioration of the oil. The oxidative stability of palm oil, olein and stearin (Table 2.16) is a major advantage of these oils. Palm olein has the longest induction period: 44 hours at 100 °C. Blending less stable

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Palm Oil

Table 2.16

43

Induction period and cloud point of oils and blends with palm olein.

Oils and blends

Induction period at 100 °C (hours)

Cloud point (°C)

51.7 44.0 55.8 11.1 – 15.0 21.0 9.0 12.0 11.8 – 11.5 16.0 8.0 7.0 16.0 19.0 6 7

– 9.6 – −3.0 5.0 1.9 2.0 −9.5 −1.9 −10.0 −10.0 −5.0 0.0 – 0.3 −9.0 −2.2 −9.5 −2.3

Refined palm oil* Refined palm olein Refined palm stearin* Cottonseed Cottonseed/palm olein Groundnut Groundnut/palm olein Maize Maize/palm olein Olive Olive/palm olein Rapeseed Rapeseed/palm olein Sesame Sesame/palm olein Soybean Soybean/palm olein Sunflowerseed Sunflowerseed/palm olein Source: Teah (1988). Note: * Palm olein was added at 30% in each blend.

vegetable oils with palm olein improves their stability (Teah 1988; Razali and Badri 1993). The improvements are seen in the reduced levels of primary and secondary oxidation products, fatty acids, volatiles and polymers. The cloud points of palm olein with unsaturated oil blends are also improved (Table 2.16). The free fatty acid content is one of the parameters used for evaluating the quality of frying oils. During frying, there is a lower formation of free acids when palm olein is used or blended with other vegetable oils (Teah 1988). Besides this, the polymer content is lower and so less change in viscosity is observed. Most polyunsaturated oils have to be hydrogenated for use as frying oils, to reduce high polymer formation and consequent viscosity increase during frying. This leads to the undesirable presence of trans acids in the frying oil. An alternative approach to this problem is to blend oils. Zalewski et al. (1999) showed that palm olein (IV 62) and rapeseed oil (50:50) or a ternary mixture of palm olein (IV 56), palm stearin (IV 48) and rapeseed oil (40:40:20) produced fewer polar compounds than pure rapeseed oil. Lower anisidine values also indicate that oil stability is better with a higher level of palm oil products. Palm olein blends with rapeseed oil allow for good sensory quality of chips during six months of storage. Palm olein and sunflower blends have proven to be very successful, as there appears to be a synergistic effect on the stability (Van Twisk and Du Plessis 1997; De Marco et al. 2007) and on the formation of polymeric compounds (Figure 2.6) (Razali and Badri 1993). Due to changing consumer demand for healthy foods, the use of high-oleic oils in frying has grown significantly. Palm olein, especially double-fractionated palm olein, fits Appelqvist’s (1997) criteria for ‘a healthy frying oil’ in having low saturated and polyunsaturated, high monounsaturated and no trans acids. A comparison of potato chips fried in olein with that of high-oleic sunflower oil showed comparable properties

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Vegetable Oils in Food Technology 9 Day 0

Day 5

Polymer compounds (%)

8 7 6 5 4 3 2 1 0 PO

POo

PHSBO

SBO

Figure 2.6 Polymer content of some frying oils. Source: Razali and Badri (1993). Key: PHSBO = partially hydrogenated soybean oil PO = palm oil POo = palm olein SBO = soybean oil

after 16 weeks of storage of the chips (Razali et al. 1999). Matthaus (2007) also indicated that palm oil and palm olein have similar frying performances compared with other high-stability oils. In another evaluation of standard-grade palm olein with specialquality palm olein as frying oils (Azmil and Razali 2008), both oils were equally good. However, as special-quality palm olein is more expensive, it is only recommended for specialty products requiring a longer shelf-life.

2.5.2

Margarines

It is a legal requirement that margarine contain at least 80% fat. Many products are now available with lower levels of fat and these should be designated as spreads rather than as margarines. However, in this account of margarines the term ‘margarine’ is used to include the reduced-fat spreads. Margarine is a product containing 80% fat blended with water, and containing vitamins and other ingredients. It was initially developed to replace dairy butter and now appears in a variety of types, which include regular, whipped, soft-tub, liquid, diet, low-calorie, bakery, speciality and so on. Today’s margarines incorporate nutritional as well as functional properties and cater for the requirements of different consumers. The properties of margarines depend on the characteristics of the oil, which is the major ingredient of the product. The solid fat content of the oil at different temperatures is an indicator of the crystallisation properties of the finished product. Palm oil and its fractions are suitable for margarine production, as shown by Teah et al. (1994), Mohd Suria Affandi et al. (1996), Noor Lida and Mohd Suria Affandi (1997) and Nor Aini and Mohd Suria (2000). Figure 2.7 shows the solid fat contents of margarines

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45

70 POo/POs/RSO (40/10/50)

Solid fat content (%)

60

IE POs/PKO (75/25)

50

POo/POs/SBO (20/50/30) PO/POs (10/90)

40 30 20 10 0 10

15

20

25

30

35

40

Temperature (8C) Figure 2.7 Solid fat contents of margarines using palm oil products in their formulations. Source: Noor Lida and Mohd Suria (1995). Key: IE POs = interesterified palm stearin PKO = palmkernel oil PO = palm oil POo = palm olein SBO = soybean oil

formulated with mixtures of palm oil and/or palm kernel oil with other vegetable oils. Tub, packet, industrial/bakery and pastry margarines can all be formulated to contain some palm oil and/or its fractions. Domestic margarines in (tropical) Malaysia are formulated with palm oil/palm olein or palm kernel oil with liquid oil. For table margarines, as much as 50% of palm oil can be used in the fat blend, while for palm olein, up to 60% can be used. Palm stearin, with its high PPP content, is an excellent hard stock for margarines made from liquid oils (Ghosh and Bhattacharyya 1997). There are several advantages to using palm stearin as a component for interesterification with liquid oils to yield a good hard stock, such as availability of oil, cheap raw material and removing the need for hydrogenation. The adverse nutritional effects of trans acids produced during hydrogenation have been well established. By interesterification of ternary or binary blends, it is possible to obtain suitable formulations that are free of trans fatty acids (Noor Lida 2007). Many suitable blends can be tailor-made to suit the requirements of consumers of different countries, using the indigenous oils of those countries along with palm oil and/or its fractions. Interesterified palm stearin (60%) and palm kernel olein (40%) result in a product with suitable properties for margarines (Table 2.17) (Teah et al. 1994). With a wide range of palm stearins available, it is possible to make many combinations for stick and soft margarines (Petrauskaite et al. 1998). A palm-based pourable margarine has been formulated by Miskandar and Mohd Suria Affandi (1998). Palm oil is suited for industrial margarines, having 23% solids at 20 °C. Palm stearins may also be included in the formulations, as shown by Teah et al. (1994) (Table 2.17). Puff pastry margarines based on palm stearin and palm oil or with palm kernel olein or soyabean oil have been reported (Teah et al. 1982). The basic requirements for puff pastry margarines

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Table 2.17

Solid fat content (SFC) for several trans-free margarines from palm oil.

Blend

PS:PKOo

IE (PS:PKOo)

IE (POo:PKO)

IE (PS:PKOo:SFO)

PS:SBO

Composition

70:30

60:40

70:30

60:20:20

80:20

Slip melting point °C

45.5

34.3

33.3

38.5

43.3

SFC (%) wideline NMR 10 °C 15 °C 20 °C 25 °C 30 °C 35 °C 40 °C

56.3 42.2 29.8 20.9 16.3 11.1 10.7

31.8 23.3 15.6 10.8 6.3 2.4 –

NA 34.6 22.7 NA 7.8 –

33.7 24.6 18.9 NA 7.1 –

69.1 57.8 46.3 33.6 23.9 17.7 8.3

Source: Teah et al. (1994). Key: IE POs = interesterified palm stearin NA = not available PKO = palmkernel oil PO = palm oil POo = palm olein SBO = soybean oil

are the most demanding with regard to crystallisation. The features of a roll-in margarine are plasticity and firmness. Palm, palm stearin and also the hydrogenated products tend to be β′ stable (Yap et al. 1989a), providing the right crystal polymorph for smooth texture in margarines. This interesting feature of the fat is utilised in the production of margarines using liquid oils. Soft margarines based on hydrogenated palm olein and liquid oils such as canola and sunflower can incorporate a high proportion of the liquid oil while still retaining the β′ form required (Table 2.18) (De Man et al. 1993). Palm oil mixed with hydrogenated canola oil can delay the formation of β crystals in β-prone hydrogenated canola oil (D’Souza et al. 1991; Yap et al. 1989b). The stick margarines that had β′ form had a palmitic acid content of approximately 20%. Addition of 10–12% of palm stearin or hydrogenated palm oil to liquid oils is sufficient to stabilise the product in the β′ crystal form. It appears that when the higher melting fraction of a fat is comprised of TAG that are stable in the β′ form, the entire fat will then crystallise in that form (De Man et al. 1992). Thus it is useful to add small amounts of palm products, especially hard palm stearin, into margarines and shortening formulations. Approaches to remove trans fats from the food supply in industrialised and developing countries include the use of palm, palm kernel stearin and canola oils or fully hydrogenated vegetable oils mixed with liquid oils (Abbe et al. 2009). Structured lipids for formulating trans-free margarines with low atherogenicity and desirable texture involve the combination of canola oil, palm stearin and palm kernel oil (Kim et al. 2008). As the crystallisation behaviour of the new oil formulations differs from the trans fat formulations, a change in processing conditions is required. Miskandar et al. (2002a, b) discussed the conditions suitable for processing margarines containing palm oil products, and concluded that good model margarines could be obtained with appropriate processing conditions, such as maintaining an emulsion temperature of 10 °C above the slip melting point of the fat, flow rates of 30 kg h−1

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Table 2.18 β′ Polymorphic stability of liquid oils blended with palm olein hydrogenated to different IV (Hyd. iolein). Drop point (°C)

SFC at 10 °C

Polymorphic form after four cycles

Hyd. olein : sunflower oil IV 42.8 30 : 70 IV 37.9 30 : 70 IV 32.0 30 : 70

36.5 41.4 44.0

20 23.7 25.5

β′ β′ β′

Hyd. olein : canola oil IV 42.8 40 : 60 IV 37.9 30 : 70 IV 32.0 20 : 80

35.8 33.0 30.2

26.4 19.6 12.8

β′ β′ β′

Source: De Man et al. (1993).

Solid fat content (%)

100 80 60 40 20 0 5

10

15

20

25

30

35

40

45

50

55

Temperature (8C) PO

POo

POs

PMF

POs(hard)

Figure 2.8 Solid fat content of palm oil products. Source: Siew, unpublished. Key: PMF = palm mid-fraction PO = palm oil POo = palm olein POs = palm stearin

(Miskandar et al. 2004), supercooling temperature of 15–20 °C (Miskandar et al. 2002a, b) and pin worker speed of 200 rpm.

2.5.3

Shortenings

Shortening, which was the term used to described the function performed by naturally occurring solid fats such as lard and butter in baked foods, is now generally applied to fat products that can affect the emulsification, lubricity, structure, aeration, flavour and heat transfer of prepared foods. Palm oil, a semi-solid fat, is highly suited for this purpose and its tendency to form β′ crystals is an advantage, as such crystals provide better aeration in batters than do β forms. Unlike margarines, shortenings are entirely oils and fats (100%). Some may have small amount of emulsifiers added. Figure 2.8 shows the solid content of palm oil

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Source: Nor Aini et al. (1995). Key: AMF = anhydrous milk fat HPO = hydrogenated palm oil IEPO = interesterified palm oil POs = palm stearin StMF = low-melting milk fat fractions

38.3 37.3 41.4 40.3 38.4 35.7 33.8 42.6 43.7 42.9

± ± ± ± ± ± ± ± ± ±

0.4 0.1 0.1 0.3 0.1 0.2 0.3 0.7 0.2 0.6

Slip melting point (°C)

β′ β′ β′ β′ β′ β>>>β′ β>>β′ β′>β β′ β′

Polymorphic form

Characteristics of shortenings from palm oil products.

PO PO:AMF 60:40 HPO HPO:AMF 80:20 HPO:AMF 60:40 IEPO IEPO:AMF 80:20 POs:AMF 40:60 POs:SfMF 60:40 POs:SfMF 40:60

Shortening

Table 2.19

250 60 1120 880 640 190 180 400 410 370

Yield value

15

good consistency very soft very firm slightly firm good consistency slightly soft slightly soft good consistency good consistency good consistency

Consistency

300 70 1370 990 690 220 190 550 1010 710

Yield value

Days of storage 60

good consistency very soft very firm slightly firm good consistency slightly soft slightly soft good consistency very firm slightly firm

Consistency

Palm Oil Table 2.20

49

Blends (%) for reduced fat spreads.

Palm oil Palm olein Sunflower oil Palm kernel olein

For tubs

For blocks

50 to 25 0 to 75 50 to 25 0

80 to 75 0 10 to 25 10 to 0

Source: Adapted from Berger and Nor Aini (2005).

products that can be incorporated with other oils to be used as shortenings. Blends of soft stearin with palm oil give products with the solid content required of a shortening. Shortenings made from palm oil products have been studied extensively (Nor Aini and Miskandar 2007; Berger and Nor Aini 2005; Nor Aini et al. 1995). Softer shortenings are made from palm oil (PO), hydrogenated palm oil (HPO), palm stearin (POs), anhydrous milk fat (AMF) or butterfat (BF) and low-melting milk fat fractions (Table 2.19). These shortenings display crystalline structures in the β′ polymorphic form. The yield values of these shortenings vary from 60–1120 g/cm2 on day 15 to 70–1370 g/cm2 on day 60. Shortenings based on hydrogenated palm oil are harder, but the plasticity and spreadability can be improved by the addition of AMF. Interesterification helps to improve the creaming performances of the shortenings, as post-hardening problems, which may be observed in palm-based shortenings, are eliminated. Krawczyk et al. (1996), in reviewing the technology of low-fat spreads, reiterated the claim that whipped products required 20–25% solid fat crystals, as these determine creaming power and help to stabilise water droplets in the mixture. Again, large β crystals are not desirable, as they result in coarse and grainy structures. A suitable formulation for low-fat spreads utilising palm in the mixture is shown in Table 2.20. A high palmitic content was also reported to be good for the aeration of fat/sugar mixtures (Nor Aini et al., 1989). Blends of palm stearin (20–40%) with palm oil make good pastries for pies, tarts and curry puffs (Nor Aini 1992). Blending helps extend the range of application of oils and fats, as most oils and fats may have inherent limitations in their physical properties.

2.5.4

Vanaspati

Vanaspati is an all-purpose fat widely used in Middle Eastern countries and the Indo-Pakistan subcontinent. It is a substitute of ghee made from butter fat. Hydrogenated products have been accepted as suitable oils for the vanaspati industry. The texture of the product varies with different consumers. In India and Pakistan, graininess is a required criterion. Pakistani consumers prefer grainy crystals among liquid oil, unlike the Indian counterparts who prefer their vanaspati to be grainy, yet dry and crumbly. The product melts at 37–39 °C, which is a property of palm oil. Palm oil at ambient temperatures has a semi-solid texture similar to that of vanaspati, and the granular consistency can be obtained through interesterification and hydrogenation (Kheiri and Oh 1983) (Table 2.21). Trans-free vanaspati can be formulated using palm stearin with other oils (Table 2.22) (Nor Aini et al. 1997, 2002). Interesterification allows more palm stearin to be incorporated into the formula. Other trans-free formulations are obtained with ternary blends of palm oil/ palm stearin/palm olein or palm oil/palm stearin/palmkernel olein (Nor Aini et al. 1999) (Table 2.23). These products have characteristics similar to those of hydrogenated vanaspati. Formulations for vanaspati may be varied to suit the requirements of different consumers.

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Table 2.21

Binary blends of refined palm oil (PO) and hydrogenated palm olein (HPOo).

Composition (%)

Solid fat content (%)

Melting point

PO

HPOo

20 °C

25 °C

30 °C

35 °C

37 °C

40 °C

100 90 80 70 60 50 40 30

0 10 20 30 40 50 60 70

28.9 30.8 36.1 40.2 45.0 47.9 51.0 55.6

19.8 20.8 24.1 27.3 30.7 34.3 37.3 40.4

11.1 13.0 15.1 18.0 19.5 22.6 28.7 27.2

9.0 7.3 9.5 11.3 12.6 14.7 15.5 17.9

–

5.9 3.6 3.4 4.7 5.1 5.7 7.9 8.2

5.2 6.5 7.8 9.3 10.4 11.2 13.1

°C 37.4 38.7 39.5 39.8 40.5 41.3 41.4 41.9

Source: Kheiri and Oh (1983). Key: HPOo = hydrogenated palm olein PO = palm oil

Table 2.22 Physical characteristics of vanaspati based on blends of palm stearin (POs) with other oils before and after interesterification. Sample

Blends before interesterification Melting point (°C)

Appearance

Consistency

Interesterified blends Melting point (°C)

POs:SBO 40:60

41.5

Wet, granular

Soft

35.9

60:40

45.5

Slightly firm

41.5

80:20

47.7

Slightly dry, granular Dry, granular

Firm

45.6

POs:RSO 40:60

43.6

Wet, granular

Soft

38.7

60:40

45.9

Slightly firm

43.4

80:20

48.5

Slightly dry, granular Dry, granular

Firm

45.6

POs:SFO

43.8

Wet, granular

Soft

34.3

40:60

45.3

Dry, granular

Slightly firm

39.3

60:40 80:20

48.6 39.0

Dry, granular Dry, granular

Firm Slightly firm

45.4 38.5

Appearance

Consistency

Wet, oily, granular Wet, oily, granular Wet, oily, granular

Very soft Very soft Soft

Wet, oily, smooth Wet, granular

Very soft

Wet, oily, granular Wet, oily, granular Wet, oily, granular Oily, granular Granular

Soft

Soft

Very soft Very soft Soft Soft

Source: Nor Aini et al. (1997). Key: POs = palm stearin RSO = rapeseend oil SBO = soybean oil SFO = sunflower oil

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Table 2.23 Characteristics of vanaspati containing palm oil, palm stearin, palm olein and palm kernel olein. Sample formulation

PO:POs:POo 80:5:15 PO:POs:POo 80:10:10 PO:POs:POo 60:20:20 PO:POs:POo 40:30:30 PO:POs:PKOo 80:5:15 PO:POs:PKOo 80:10:10 PO:POs:PKOo 60:20:20 PO:POs:PKOo 40:30:30 Commercial sample of vanaspati

Slip melting point (°C)

Softening point (°C)

Dropping point (°C)

37.2

37.7

38.9

39.2

42.2

41.2

42.3

41.9

45.6

46.8

43.2

47.0

38.0

39.0

39.7

41.2

40.9

41.9

47.3

45.6

44.8

48.3

46.5

44.9

38.5

42.6

42.7

Source: Nor Aini et al. (1999). Key: PKOo = palm kernel olein PO = palm oil POo = palm olein POs = palm stearin

Incorporation of more or less palm oil products in the formulation generally affects the melting point property, which is a limitation for certain countries.

2.5.5

Cocoa butter equivalents (CBE)

These are fats rich in symmetrical disaturated TAG (SUS) that behave like cocoa butter in all respects and are able to mix in all proportions with cocoa butter. The desirable characteristics of cocoa butter are due to the SUS TAG, which provide a suitable melting point and solid fat content, resulting in rapid melt in the mouth and cooling sensations. Palm mid-fraction (PMF), which has a high content of POP, is easily formulated with other SUS fats for chocolate products (Berger 1981). About 70–80% PMF with 20–30% shea or sal stearin, or 60–65% PMF with 20–30% shea or sal stearin and 15%–20% illipe, are suitable for plain chocolate and for milk chocolate with 15% milk fat. The compatibility of cocoa butter (CB) and CBE is affected by the addition of milk fat and its fractions into the product (Sabariah et al. 1998). Eutectic interactions between anhydrous milk fat (AMF), CBE and CB were noticeable due to the different polymorphism encountered in these fats. Cocoa butter-like fats can also be formulated with interesterified oils. Blends suitable for butter-cream fillings in biscuits may be formulated from palm stearin/palm kernel olein (25:75) or palm stearin/palm kernel olein/palm kernel oil (25:37.5:37.5) (Noor Lida et al. 1997).

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2.5.6

Other uses

Palm oil is used in snack foods, biscuits, ice creams, salad dressings, mayonnaise and so on. Fat plays a key role in all these food items and the formulation using palm oil products replaces some of the oils used traditionally. Oil suitable for ice cream should be partly solid at 5 °C and −5 °C, substantially liquid at 37 °C, and have good ‘melt’ feel characteristics. Palm oil with a similar solid fat content profile to butterfat has suitable characteristics for ice-cream formulations. Palm kernel oil is also much used in ice-cream products. Salad oils, dressings and mayonnaise are used for mixing vegetables, meat and other ingredients. Mayonnaise contains vegetable oils, acidifying agents and egg yolk. The stability of the oil in the emulsion is important. Salad dressing contains oil, egg yolk, acidifying agents and other ingredients. The oils used in these products are usually polyunsaturated. Blends of palm olein with polyunsaturated oils provide better oxidative stability and keepability than the polyunsaturated oils alone. Red palm olein, containing high levels of carotenoids, makes a good salad dressing, but is reddish in colour.

2.6

NUTRITIONAL ASPECTS OF PALM OIL

Palm oil is frequently categorised as a saturated fat even though it contains equal proportions of saturated (mainly palmitic acid) and unsaturated acids (mainly oleic acid). Since historically saturated fats have been linked to cardiac diseases, palm oil and many palm oil fractions have been considered unhealthy fats. However, paradoxically, saturated fatty acids constitute half of the acids in membrane phospholipids and a third of acids in trialyglycerols in healthy humans (Lands 2008). In his extensive review, Lands has not been able to find a plausible mechanism for linking saturated fats with ill health, except that of epidemiological interpretation. In fact, recent studies of women followed over a period of 20 years showed that saturated fat intake did not statistically predict cardiac diseases, when adjusted for nondietary and dietary risk factors (Oh et al. 2005). In recent years, nutritional research has shown that coronary risk is influenced by the ratio of total cholesterol to HDL cholesterol and the ratio of LDL to HDL cholesterol. Diets enriched in saturated fats also increased the HDL cholesterol, while increasing the LDL cholesterol. This suggests that palm oil and palm olein as a natural fat/oil with only 50% and less than 40%, respectively, of saturation should not be of any harm to human health. Furthermore, in most cases palm oil products are not utilised on their own, but are used as blends in different formulations with other unsaturated oils. There are other research findings that have indicated that the overall saturation of the fat may not be the sole critical factor affecting cardiac diseases, but that the type of saturated fatty acids and the position of the fatty acids in the triacylglycerol is of importance (Zock et al. 1994; Kritchevsky et al. 2000). Animal studies have shown that altering the stereospecific distribution of certain fatty acids on dietary triacylglycerols can impact the artherogenic potential (Hunter 2001). The review indicated that artherogenicity increased when levels of palmitic acid in the sn-2 position increased. Palm oil and palm olein, which have mainly unsaturated fatty acids of oleic and linoleic in the sn-2 position of the triacylglycerol, could be the reason why these oils do not generally exhibit cholesterol-raising effects. The difference in palmitic content at the sn-2 position of palm oil compared to other vegetable oils may not be enough for producing a high cholesterol effect. In another study by Forsythe et al. (2007), palmitic acid in

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53

the sn-2 position resulted in slightly lower fasting total cholesterol than diets with palmitic acid in the sn-1,3 positions. Some studies have found that palm olein compared with other highly monounsaturated oils such as olive oil in the diet resulted in similar total and LDL cholesterol levels (Choudhury et al. 1995; Ng et al. 1992). In addition to its fatty acid composition, palm oil has minor components that have nutritive and health-enhancing properties. Suffice to say, a commonsense approach of utilising all natural oils in small doses should be ideal for good nutrition.

2.7

SUSTAINABLE PALM OIL

Palm oil represents about 30% of the world production of vegetable oils and fats. If this 30% of the world’s requirement for oils is taken out of the equation, it would have to come from the other oils and fats. However, it is noted that palm oil is the highest-yielding oil crop (3.66 tonnes/ha/year), compared to 0.36 tonnes/ha/year, 0.6 tonnes/ha/year and 0.46 tonnes/ha/ year for soy, rapeseed and sunflower oil, respectively. While only 9.2 million hectares of land area are needed to produce the 30% share of global oils and fats output that is from palm oil, 92.5 million hectares of land would be needed if the same output were to come from soybean oil (Yusof 2009). In addition to this, sustainable practices such as pest management via biological controls, zero-waste strategies, soil management, biomass as fertilisers and bio-product utilisation have been put in place for many years (Yusof 2007). The palm oil industry has generated income for many in the developing countries who otherwise would have been in poverty. In Malaysia, for example, the government’s model of providing plots of land to smallholders to grow oil palm has assisted farmers in rural areas to grow oil palm instead of other agricultural crops. In this way, farmers’ incomes have improved tremendously. The oil-palm plantation is like a forest, providing a green canopy, which effectively absorbs carbon dioxide from the environment. In a study by Vijaya et al. (2008) on the environmental performance of the oil-milling process using the LCA approach, the gate-to-gate system boundary that was defined from fresh fruit bunch received to oil in storage tank showed two main parameters as causing potential impact on the environment. These are palm oil mill effluent (POME) and boiler ash. When biogas from POME is harvested and used as energy in the mill, the adverse effect from POME is removed and POME becomes a saving to the environment. The boiler ash, which contains minerals and traces of metals, contributes to the eco-toxicity impact if not handled properly. Dalgaard (2009) provided a calculation of GHG emission of 3.18 tCO2e per tonne NBD palm oil produced, while rapeseed showed values of 3.37–3.14 tCO2e per tonne. The average Malaysian figure is further improved to 2.32 when biogas is harnessed for electricity. The industry takes further steps to ensure sustainability by reducing greenhouse gases and effluent discharge, and creating wildlife sanctuaries within plantations wherever possible.

2.8

CONCLUSIONS

The unique feature of palm oil is its balanced range of saturated and unsaturated fatty acids, which allow the oil to be easily fractionated into products containing more saturated or more unsaturated TAG. The extended range in the composition and properties of palm oil and its

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fractions allows many food product formulations to be made incorporating the most suitable fractions. Blending and interesterification are the main processes used to produce oils with properties suitable for margarine, shortening, vanaspati, frying oils and so on. The advantages of using palm-oil products include cheap raw material, good availability and low cost of processing, since hydrogenation is not necessary. The high oxidative stability of the oil is in part due to the fatty acid composition, but also to the carotenoids and tocotrienols present. Processing technologies can protect natural pigments, tocopherols and tocotrienols in the refined oils, producing products with suitable specifications required by customers. Future research should lead to the production of oils with a higher oleic acid content and a higher content of carotenoids and tocotrienols, suitable for the health-conscious market. Nutritional research, focusing on the lipid metabolism and the beneficial effects of vitamin E and β-carotene, has helped to enhance the recognition of palm oil as a healthy oil.

REFERENCES Abbe, M.R.L., Stender, S., Skeaff, C.M., Ghafoorunissa and Travella, M. (2009) Approaches to removing trans fats from the food supply in industrialized and developing countries. European Journal of Clinical Nutrition, 63, S50–S67. Abdul Gapor, M.T. (1990) Content of vitamin E in palm oil and its antioxidant activity, Palm Oil Developments, 12, 25–27. Abdul Gapor, M.T. and Hazrina, A.R. (2000) Squalene in oils and fats, Palm Oil Developments, 32, 36–40. Abdul Gapor, M.T., Berger, K.G., Hashimoto, T., Tanabe, K., Mamuro, H. and Yamoka, M. (1981) Effects of processing on the content and composition of tocopherols and tocotrienols in palm oil, in Proceedings of International Conference on Palm Oil Product Technology in the Eighties, PORIM/ISP, Kuala Lumpur, pp. 145–156. Abdul Gapor, M.T., Kato, A. and Ong, A.S.H. (1988) Studies on vitamin E and other useful compounds in PFAD and oil palm leaflets, in Proceedings of the 1987 International Oil Palm/Palm Oil Conferences, Progress and Prospects, Kuala Lumpur, pp. 124–128. Appelqvist, L.A. (1997) Healthy frying oils, in New Developments of Industrial Frying (ed. S.P. Kochar), P.J. Barnes, Bridgwater, pp. 91–117. Azmil, H.A.T. and Razali, I. (2008) Comparison of the frying stability of standard palm olein and special quality palm olein, Journal of the American Oil Chemists’ Society, 85, 245–251. Berger, K.G. (1981) Food uses of palm oil. PORIM Occasional Paper, 2, 1–27, Kuala Lumpur: Malaysian Palm Oil Board. Berger, K.G. (2007) The use of palm oil in frying, http://www.malaysiapalmoil.org/publications/pdf/palmoil-in-fryin. Berger, K.G. and Nor Aini, I. (2005) Formulation of zero trans acid shortenings and margarines and other food fats with products of the oil palm, Journal of the American Oil Chemists’ Society, 82, 775–782. Braipson-Danthine, S and Gibon, V. (2007) Comparative analysis of triacylglycerol composition, melting properties and polymorphic behaviour of palm oil and fractions, European Journal of Lipid Science Technology, 109, 359–372. Chin, A.H.G, Oh, F.C.H. and Siew, W.L. (1982) Identity characteristics of Malaysian palm oil, Mardi Research Bulletin, 10, 80–104. Choo, Y.M. (1994) Palm oil carotenoids, in Food and Nutrition Bulletin, 15, United Nations University, Tokyo. Choo, Y.M. (1995) Carotenoids in palm oil, Palm Oil Developments, 22, 1–6. Choudhury, D., Tan, L. and Truswell, A.S. (1995) Comparison of palm olein and olive oil: Effects on plasma lipids and vitamin E in young adults, American Journal of Clinical Nutrition, 61, 1043–1051. D’Souza, V., de Man, L. and de Man, J.M. (1991) Chemical and physical properties of the high melting glyceride fractions of commercial margarines, Journal of the American Oil Chemists’ Society, 68, 153–162. Dalgaard, R. (2009) LCA of Malaysian palm oil – improvement options and comparison with European rapeseed, paper presented at Conference on Harmonizing Palm Oil’s Life Cycle Assessment for GHG Savings, 18–20 Oct., Kuala Lumpur.

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De Man, J.M. (1992) X-ray diffraction spectroscopy in the study of fat polymorphism, Food Research International, 25, 471–476. De Man, L., D’Souza, V., De Man, J.M. and Blackman, B. (1992) Polymorphic stability of some shortenings as influenced by the fatty acid and glyceride composition of the solid phase, Journal of the American Oil Chemists’ Society, 69, 3, 246–250. De Man, L., Xu, Y.J., Chen, S.H. and De Man, J.M. (1993) Polymorphic stability of hydrogenated palm oleins in dilutions with unhydrogenated liquid oils, Journal of the American Oil Chemists’ Society, 70, 431–433. De Marco, E., Savarese, M., Parisini, C., Battimo, I., Salvatore, F. and Sacchi, R. (2007) Frying performance of a sunflower/palm oil blend in comparison with pure palm oil, European Journal of Lipid Science Technology, 109, 237–246. Deffense, E. (1995) Dry fractionation: Trends in products and applications, Lipid Technology, 7(2), 34–38. Downes, M.J. (1982) Determination of sterol composition of crude vegetable oils. Part II. Palm oil and palm oil products, Leatherhead Food Research Association Technical Circular, 781, 4–5. Elias, B.A. and Pantzaris, T.P. (1997) Authenticity of palm oil – assessment of a Brazilian survey, Palm Oil Technical Bulletin, 3(2), 8–9. Fernandes, P. and Cabral, J.M.S. (2007) Phytosterols: Applications and recovery methods, Bioresource Technology, 98, 2335–2350. Forsythe, C.E., French, M.A., Goh, Y.K. and Clandinin, M.T. (2007) Cholesterolemic influence of palmitic acid in the sn-1,3 v. the sn-2 position with high or low dietary linoleic acid in healthy men, British Journal of Nutrition, 98, 337–344. Goh, S.H. and Gee, P.T. (1984) Unreported constituents from E. guineensis. In Proceedings of the PRIOCHEM Asia 1984 Chemical Conference (eds. M.M. Singh and L.S. Eng), Malaysian Institute of Chemistry, Kuala Lumpur, pp. 507–515. Goh, S.H, Choo, Y.M. and Ong, A.S.H. (1985) Minor components of palm oil, Journal of the American Oil Chemists’ Society, 62, 237–240. Goh, S.H., Khor, H.T. and Gee, P.T. (1982) Phospholipids of palm oil (E. guineensis), Journal of American Oil Chemists’ Society, 59, 296–299. Ghosh, S. and Bhattacharyya, D. (1997) Utilization of high-melting palm stearin in lipase-catalyzed interesterification with liquid oils, Journal of the American Oil Chemists’ Society, 74(5), 589–592. Gunstone, F. (2007) Market update: Palm oil, INFORM, 18(12), 835–836. Guthrie, N., Gapor, A., Chambers, A.F. and Carroll, K.K. (1997) Palm oil tocotrienols and plant flavanoids act synergistically with tamoxifen in inhibiting proliferation and growth of oestrogen receptor negative MDA-MB-435 and positive MCF-7 human breast cancer cells, Asia Pacific Journal of Clinical Nutrition, 6, 41–45. Hashimoto, T., Kato, A., Tanabe, K. et al. (1980) Studies on tocopherols and tocotrienols in Malaysian palm oil (I), in Proceedings of International Symposium of the Advanced Industrial Utilisation of the Tropical Plants, 1–4 September, Tsukuba, Japan, International Research and Development Cooperation Division, Ministry of International Trade and Industry, Tokyo. Hazura, A.H., Choo, Y.M., Goh, S.H. and Khor, H.T. (1996) The ubiquinones of palm oil, in Nutrition Lipids Health and Disease (eds A.S.H. Ong, E. Nike and L. Packer), AOCS Press, Urbana, IL, pp. 122–128. Hunter, J.E. (2001) Studies on effects of dietary fatty acids as related to their position on triglycerides, Lipids, 36, 655–688. Itoh, T., Tamura, T. and Matsumoto, T. (1973a) Methyl sterol compositions of 19 vegetable oils, Journal of the American Oil Chemists’ Society, 50, 300–303. Itoh, T., Tamura, T. and Matsumoto, T. (1973b) Sterol compositions of 19 vegetable oils, Journal of the American Oil Chemists’ Society, 50, 122–125. Jacobsberg, B. (1974) Palm oil characteristics and quality, in Proceedings of the 1st Mardi Workshop on Oil Palm Technology (eds. O.S. Chai and A. Awalludin), Malaysian Agriculture Research and Development Institute (MARDI), Kuala Lumpur, pp. 48–68. Jalani, B.S., Cheah, S.C., Rajanaidu, N. and Darus, A. (1997) Improvement of oil palm through breeding and biotechnology, Journal of the American Oil Chemists’ Society, 47, 1451–1455. Kheiri, M.S.A. and Oh, F.C.H. (1983) Formulation of vegetable ghee/vanaspati, in Proceedings of Palm Oil Product in the Eighties (eds E. Pusparajah, and M. Rajanaidu), Incorporated Society of Planters, Kuala Lumpur, pp. 449–474. Kim, B.H., Lumor, S.E. and Akoh, C.C. (2008) Trans free margarines prepared with canolaoil/palm stearin/ palm kernel oil-based structured lipids, Journal of Agriculture and Food Chemistry, 56, 8195–8205.

Gunstone_c02.indd 55

1/25/2011 6:39:13 PM

56

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King, B. and Sibley, I. (1984) Authenticity of edible oils and fats. Part II: Palm oil and palm fractions, The British Food Manufacturing Industries Research Association Report, 462, 1–36. Komiyama, K. and Yamoka, M. (1993) Anti tumour activity of tocotrienols, in Vitamin E in Health and Disease (eds L. Packer and J. Fuchs), Marcel Dekker, New York, pp. 529–532. Krawczyk, G.R., Bulliga, G.S., Bertrand, D.T. and Humphreys, W.M. (1996) Reviewing the technology of low fat spreads, INFORM, 7(6), 635–639. Kritchevsky, D., Tepper S.A., Chen S.C., Meijer G.W. and Krauss R.M. (2000) Cholesterol vehicle in experimental atherosclerosis. 23. Effects of specific synthetic triglycerides, Lipids, 35, 6, 621–625. Lands, B. (2008) A critique of paradoxes in current advice on dietary lipids, Progress in Lipid Research, 47, 77–106. Matsumoto, A., Takahashi, S. Nakano, K. and Kajima, S. (1995) Identification of a new form of vitamin E in vegetable oil, Journal of the Japan Oil Chemists’ Society, 44, 593–597. Matthaus, B. (2007) Use of palm oil for frying in comparison with other high stability oils, European Journal of Lipid Science Technology, 109(4), 400–409. Miskandar, M.S. and Mohd Suria Affandi, Y. (1998) Palm oil pourable margarine, PORIM Information Series, 70, 1–4, PORIM, Kuala Lumpur. Miskandar, M.S., Che Man, Y.B., Yusoff, M.S.A. and Abdul Rahman, R. (2002a) Effect of emulsion temperature on physical properties of palm oil based margarine, Journal of the American Oil Chemists’ Society, 79(12), 1163–1168. Miskandar, M.S., Che Man, Y.B., Yusoff, M.S.A. and Abdul Rahman, R. (2002b) Effect of scraped surface tube cooler temperatures on the physical properties of palm oil margarine, Journal of the American Oil Chemists’ Society, 79(9), 931–936. Miskandar, M.S., Che Man, Y.B., Yusoff, M.S.A. and Abdul Rahman, R. (2004) Effect of flow rates on the storage properties of palm oil-based margarine, Journal of Food Lipids, 11(1), 1–13. Mohd Suria Affandi, Y., Noor Lida Habi, M.D., Kamal Azmi, K. and Rozi, M.P. (1996) Trans free margarine formulation, PORIM Information Series, 55, 1–2, PORIM, Kuala Lumpur. Mohd Zaki, S., Nik Meriam, S. and Sivaruby, K. (1997) Triacylglycerols responsible for the onset of nucleation during clouding of palm olein, Journal of the American Oil Chemists’ Society, 74, 1553–1558. Murphy, D.J. (2007) Future prospects for oil palm in the 21st century: Biological and related challenges, European Journal of Lipid Science Technology, 109, 296–306. Nesaretnam, K., Wong, W. Y. and Mohd Basri, W. (2007) Tocotrienols and cancer: Beyond antioxidant activity, European Journal of Lipid Science Technology, 109(4), 445–452. Nesaretnam, K. (2008) Multitargeted therapy of cancer by tocotrienols, Cancer Letters, 269, 388–395. Nesaretnam, K., Guthrie, N., Chambers, A.F. and Carroll, K.K. (1995) Effect of tocotrienols on the growth of human breast cancer cell line in culture, Lipids, 30, 1139–1143. Ng, T.K., Hayes, K.C., Dewitt, G.F. et al. (1992) Dietary palmitic and oleic acids exert similar effects on serum cholesterol and lipoprotein profiles in normocholesterolemic men and women, Journal of the American College of Nutrition, 11, 383–390. Noor Lida, H.M.D. (2007) Effect of chemical interesterification on triacylglycerol and solid fat contents of palm stearin, sunflower oil and palm kernel olein blends, European Journal of Lipid Science Technology, 109, 147–156. Noor Lida, H.M.D. and Mohd Suria, A.Y. (1995) Trans-free formulations: A short review, Palm Oil Developments, 22, 33–37, Kuala Lumpur: Malaysian Palm Oil Board. Noor Lida, H.M.D., Mohd Suria Affandi, Y. and Razali, I. (1997) Trans free acids free food formulation based on palm oil and its products: A review, PORIM Occasional Paper, 36, pp. 1–21, PORIM, Kuala Lumpur. Nor Aini, I. (1992) A variety of bakery products can be made with palm oil based shortening, PORIM Information Series, 9, 1–4, PORIM, Kuala Lumpur. Nor Aini, I. and Hanirah, H. (1996) Clarity of single and double fractionated palm oleins, Elaeis, 8(2), 104–113. Nor Aini, I. and Hanirah, H. (1997) Resistance to crystallisation of single and fractionated palm olein, in Oils and Fats in Food Applications (ed. K.G. Berger), P.J. Barnes, Bridgewater, pp. 1–7. Nor Aini, I. and Miskandar, M.S. (2007) Utilisation of palm oil products in shortenings and margarines, European Journal of Lipid Science Technology, 109, 422–432. Nor Aini, I. and Mohd Suria, A.Y. (2000) Food uses of palm and palm kernel oil, in Advances in Oil Palm Research, Vol II (eds B. Yusof, B.S. Jalani and K.W. Chan), Malaysian Palm Oil Board, Kuala Lumpur, pp. 968–1026.

Gunstone_c02.indd 56

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Nor Aini, I., Berger, K.G. and Ong, A.S.H. (1989) Evaluations of shortenings based on various palm oil products, Journal of the Science of Food and Agriculture, 46, 481–493. Nor Aini, I., Che Maimon, C.H., Hanirah, H., Zawiah, S. and Che Man, Y.B. (1999) Trans free vanaspati containing ternary blends of palm oil-palm stearin-palm olein and palm oil-palm stearin-palm kernel olein, Journal of the American Oil Chemists’ Society, 76(5), 643–648. Nor Aini, I., Embong, M.S., Aminah, A., Md Ali, R. and Che Maimon, C.H. (1995) Physical characteristics of shortenings based on modified palm oil, milkfat and low melting milkfat fractions, Fat Science Technology, 97(7/8), 253–260. Nor Aini, I., Ismail, R., Noor Lida, H.M.D., Miskandar, M.S. and Radzuan, J. (2002) Blending of palm oil and palm oil products with other oils and fats for food applications, Oil Palm Bulletin, 24, 6–15. Nor Aini, I., Lina, L., Yusoff, M.S.A. and Arif Simeh, M. (1997) Palm oil-based trans free vanaspati, Proceedings of the 1997 PORIM Technology Transfer Seminar, PORIM, Kuala Lumpur, pp. 28–39. Nor Aini, I., Yusof, B., Hanirah, H. and Rosilah, B. (1993) Effect of some additives on resistance to crystallisation of palm olein, Elaeis, 5(1), 47–64. Oh, K., Hu, F.B., Manson, J.E., Stampfer, M.J. and Willet, W.C. (2005) Dietary fat intake and risk of coronary heart disease in women: 20 years of follow-up of the nurses’ health study, American Journal of Epidemiology, 161, 672–679. Ong, A.S.H. and Goh, S.H. (2002) Palm oil: A healthful and cost effective dietary compound, Food and Nutrition Bulletin, 23(1), 11–22, United Nations University, Tokyo. Ooi, C.K., Choo, Y.M. and Ong, A.S.H. (1992) Refining of edible oil, Australian Patent 632272. Petrauskaite, V., Greyt, W. de, Kellens, M. and Huyghebaert, A. (1998) Physical and chemical properties of trans-free fats produced by chemical interesterification of vegetable oil blends, Journal of the American Oil Chemists’ Society, 75, 489–493. Puah, C.W., Choo, Y.M., Ma, A.N. and Chuah, C.H. (2007) The effect of physical refining on vitamin E (tocopherol, tocotrienol and tocomonoenol), American Journal of Applied Sciences, 4(6), 374–377. Quereshi, A.A., Quereshi, N., Wright, J.J.K. et al. (1991) Lowering of serum cholesterol in hypercholesterolemic humans by tocotrienols (palm vitae), American Journal of Clinical Nutrition, 53, 1021S–1026S. Rajanaidu, N., Kushari, A., Rafii, M. et al., (2000) Oil palm breeding and genetic resources, in Advances in Oil Palm Research, Vol 1 (eds B. Yusof, B.S. Jalani, and K.W. Chan), Malaysian Palm Oil Board, Kuala Lumpur, pp. 171–224. Rajanaidu, N., Rao, V. and Tan, B.K. (1985) Analysis of fatty acids composition in E. guineensis, E. Oleifera, their hybrids and its implications in breeding, in Oil Composition in Oil Palm, Malaysian Palm Oil Board, Kuala Lumpur, pp. 81–94. Razali, I. and Badri, M. (1993) Oil absorption, polymer, and polar compounds formation during deep fat frying of french fries in vegetable oils, in Proceedings of the 1993 PORIM International Congress, Update and Vision (ed. Y. Basiron), PORIM, Kuala Lumpur, pp. 80–89. Razali, I., Fauziah, A. and Noriani, S. (1999) Quality of potato chips fried in palm olein and high oleic oil sunflower oil during batch frying, in Proceedings of 1999 PORIM International Palm Oil Congress, (eds. A.N. Ma, M.C. Chow, C.L. Chong et al.), PORIM, Kuala Lumpur, pp. 237–246. Rossell, J.B., King, B. and Downs, M.J. (1983) Detection of adulteration, Journal of the American Oil Chemists’ Society, 60, 333–339. Sabariah, S., Md Ali, A.R. and Chong, C.L. (1998) Physical properties of Malaysian cocoa butter as affected by addition of milkfat and cocoa butter equivalent, International Journal of Food Science and Nutrition, 49, 211–218. Sen, C.K., Khanna, S., Rink, C. and Roy, S. (2007) Tocotrienols: The emerging face of natural vitamin E, Vitamins and Hormones, 76, 203–261. Serbinova, E.A., Tsuchiya, M., Goth, S., Kagan, V.E. and Packer, L. (1993) Antioxidant action of α-tocopherol and α-tocotrienol in membranes, in Vitamin E in Health and Disease (eds. L. Packer and L. Fuchs), Marcel Dekker, New York, pp. 235–243. Siew, W.L. (1990) Palm oil sterols, in Palm Oil Developments, Malaysian Palm Oil Board, Kuala Lumpur, pp. 18–19. Siew, W.L. and Chong, C.L. (1998) Phase transition of crystals in palm olein, PORIM Report, PO(283), Malaysian Palm Oil Board, Kuala Lumpur, pp. 1–71. Siew, W.L. and Ng, W.L. (1996a) Characterisation of crystals in palm olein, Journal of the Science of Food and Agriculture, 70, 212–216. Siew, W.L. and Ng, W.L. (1996b) Effect of diglycerides on the crystallisation of palm oleins, Journal of the Science of Food and Agriculture, 71, 496–500.

Gunstone_c02.indd 57

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Siew, W.L. and Ng, W.L. (1999) Diglycerides in palm oil products: Composition and effects in oil properties, in Physical Properties of Fats, Oils and Emulsifiers (ed. N. Widlak), AOCS Press, Urbana, IL, pp. 129–139. Siew, W.L., Chong, C.L., Tan, Y.A., Fairuzah, S. and Yassin, M. (1990) Identity characteristics of processed palm oils for export, PORIM Report, PO(169)90, Malaysian Palm Oil Board, Kuala Lumpur, pp. 1–17. Siew, W. L., Chong, C.L., Tan, Y.A.,Tang, T.S. and Oh, C.H. (1992) Identity characterisitcs of Malaysian palm oil products, Elaeis, 4, 79–85. Siew, W. L., Tang, T.S., Oh, C.H., Chong, C.L. and Tan, Y.A. (1993) Identity characteristics of Malaysian palm oil products: Fatty acid and triglyceride compositions and solid fat contents, Elaeis, 5, 38–45. Stahl, W. and Sies, H. (2005) Bioactivity and protective effects of natural carotenoid, Biochemica Biophysica Acta, 1740, 101–107. Swoboda, P.A.T. (1982) Bleachability and the DOBi, PORIM Bulletin, 5, 28–38, PORIM, Kuala Lumpur. Tan, B.K. (2001) Recent advances in modification techniques for specialty fats, paper presented at the PORIM International Palm Oil Conference on Cutting Edge Technologies for Sustained Competitiveness, 20–22 August, Kuala Lumpur. Tan, B.K. and Oh, F.C.H. (1981a) Malaysian palm oil chemical and physical characteristics, PORIM Technology, 3, 1–5, PORIM, Kuala Lumpur. Tan, B.K. and Oh, F.C.H. (1981b) Oleins and stearins from Malaysian palm oil: Chemical and physical characteristics, PORIM Technology, 4, 1–6, PORUM, Kuala Lumpur. Tan, B.K, Oh, F.C.H, Ong, S.H. and Berger, K.G. (1981) Characteristics of Malaysian palm mid fractions, PORIM Report, PO(34), 81, 1–18, PORIM, Kuala Lumpur. Tan, Y.A., Ainie, K., Siew, W.L., Mohtar, Y. and Chong, C.L. (1997) Crude palm oil survey, Report on Project CT 351/97. Viva Report No 089/99(7), Malaysian Palm Oil Board, Kuala Lumpur, pp. 1–69. Tang, T.S, Chong, C.L., Yusoff, M.S.A. and Abdul Gapor, M.T. (1995) Characteristics of superolein from the fractionation of palm oil, PORIM Technology, 17, 1–9, PORIM, Kuala Lumpur. Tavares, M. and Barberio, J.C. (1995) Fatty acid composition of Brazilian palm oil, in Proceedings of the PORIM International Palm Oil Congress: Update and vision in chemistry and technology, PORIM, Kuala Lumpur, pp. 328–332. Teah, Y.K. (1988) Improvements in the frying quality of vegetable oils by blending with palm olein, in Palm Oil Developments, Malaysian Palm Oil Board, Kuala Lumpur, pp. 1–4. Teah, Y.K., Kheiri, M.S.A., Karimah, A. and Berger, K.G. (1982) Margarine formulation: A survey of commercial margarine products of tropical and temperate countries, PORIM Interim Report for Project No EU-2, Malaysian Palm Oil Board, Kuala Lumpur, pp. 1–63. Teah, Y.K., Noriani, S. and Hamirin, K. (1994) Interesterification – a useful means of processing palm oil products for use in table margarine, PORIM Information Series, 23, PORIM, Kuala Lumpur. Van Twisk, P. and Du Plessis, L.M. (1997) Industrial frying oil – basic aspects, PORIM Technical Bulletin, 3(1), 2–5, PORIM, Kuala Lumpur. Vijaya, S., Ma, A.N., Choo, Y.M. and Nik Meriam, N.S. (2008) Environmental performance of the milling process of Malaysian palm oil using the Life Cycle Assessment approach, American Journal of Environmental Sciences 4(4), 310–315. Yap, P.H., de Man. J.M. and de Man, L. (1989a) Polymorphism of palm oil and palm oil products, Journal of the American Oil Chemists’ Society, 66, 693–697. Yap, P.H., de Man, J.M. and de Man, L. (1989b) Polymorphic stability of hydrogenated canola oil as affected by addition of palm oil, Journal of the American Oil Chemists’ Society, 66, 1784–1791. Yap, S.C., Choo, Y.M., Ong, A.S.H. and Goh, S.H. (1991) Quantitative analysis of carotenes in the oil from different palm species, Elaeis, 3, 369–378. Yusof, B. (2007) Palm oil production through sustainable plantation, European Journal of Lipid Science Technology, 109(4), 289–295. Yusof, B. (2009) Symposium on Sustainable Development, London, May 18, http://www.mpoc.org.my. Zalewski, S., Hoffmann, M., Berger, S. and Swiderski, F. (1999) Rapeseed–palm oil blends allow for good quality and stability of deep fried potato products, in Proceedings of 1999 PORIM International Palm Oil Congress, Emerging Technologies and Opportunities in the next Millennium (eds. A.N. Ma, M.C. Chow, C.L. Chong et al.), Malaysian Palm Oil Board, Kuala Lumpur, pp. 224–236. Zock, P.L., de Vries, J.H. and Katan, M.B. (1994) Impact of myristic acid versus palmitic acid on serum lipid and lipoprotein levels in healthy women and men, Arteriosclerosis, Thrombosis, and Vascular Biology, 14(4), 567–575.

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Soybean Oil

Tong Wang

3.1

INTRODUCTION

Soybean is the dominant oilseed produced in the world, because of its favorable agronomic characteristics, its high-quality protein, and its valuable edible oil. It contributes about 47% of all oilseeds produced worldwide in 2008/09 (Figure 3.1). The US ranks first in soybean oil production (8.5 million tonnes), followed by China, Argentina, Brazil, EU-27, and India (7.3, 6.1, 6.0, 2.3, and 1.3 million tonnes, respectively, as seen in Chapter 1). The production of soybean and soybean oil is driven by the need for soy protein meal, which is used extensively in commercial feeds for poultry, swine, and cattle. Soybean oil accounted for about 80% of total edible oil consumption in the US (USDA-NASS) in 2008 because of its availability and its many desirable characteristics, including compositional and functional properties. Soybean oil was the predominant vegetable oil produced in the world until 2003/04, but is now surpassed by palm oil, as shown in Figure 3.1.

3.2 3.2.1

COMPOSITION OF SOYBEAN AND SOYBEAN OIL Seed composition

Mature soybeans are oval shaped and their sizes are variety dependent. The seed consists of three major parts: seed coat or hull, cotyledon, and germ or hypocotyls. These structural components have the approximate composition shown in Table 3.1.

3.2.2

Oil composition

Crude oil recovered by solvent extraction or mechanical pressing contains various classes of lipids. It consists primarily of neutral lipids, which include tri-, di-, and mono-acylglycerols, free fatty acids, and polar lipids such as phospholipids. It also contains a minor amount of unsaponifiable matter that includes phytosterols, tocopherols, and hydrocarbons such as squalene. Trace metals are found in soybean oil in ppm concentration. When the oil is refined, concentrations of minor constituents are reduced. The typical composition of crude and refined soybean oil is shown in Table 3.2. Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Production, million tonnes

45

Soybean Rapeseed/Canola

40

Sunflower 5 Other oils

35 30 25 20 15 10 5 0

9 7 7 5 6 2 8 9 6 1 8 4 0 3 –9 6–9 7–9 8–9 9–0 0–0 1–0 2–0 3–0 4–0 5–0 6–0 7–0 8–0 9 0 9 0 0 0 0 0 0 9 0 9 0

95

Year Figure 3.1 Production of five major vegetable oils (million tonnes) worldwide for the period of 1995/96 to 2008/09 (adapted from Chapter 1). The 5 other oils include coconut, cottonseed, olive, palmkernel, and peanut (groundnut) oil.

Table 3.1 Chemical composition (wt %) of soybean and its components (dry weight basis). Components

Yield

Protein

Oil

Ash

Carbohydrate

Whole seed Cotyledon Hull Hypocotyl

100.0 90.3 7.3 2.4

40.3 42.8 8.8 40.8

21.0 22.8 1.0 11.4

4.9 5.0 4.3 4.4

33.9 29.4 85.9 43.4

Source: Perkins (1995a).

Table 3.2

Average composition for crude and refined soybean oil.

Components

Crude oil

Refined oil

Triacylglycerols (%) Phospholipids (%) Unsaponifiable matter (%) Phytosterols Tocopherols Hydrocarbons Free fatty acids (%) Trace metals (ppm) Iron Copper

95–97 1.5–2.5 1.6 0.33 0.15–0.21 0.014 0.3–0.7

>99 0.003–0.045 0.3 0.13 0.11–0.18 0.01 <0.05

1–3 0.03–0.05

0.1–0.3 0.02–0.06

Source: Adapted from Pryde (1980a).

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Table 3.3

61

Average fatty acid composition (wt %) of oils from soybean and other oilseeds.

Fatty acid Lauric Myristic Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Arachidic Gadoleic Eicosadienoic Behenic Lignoceric

12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 20:2 22:0 24:0

Soybean

Canola

Cottonseed

Sunflower

Peanut

– 0.1 11.0 0.1 4.0 23.4 53.2 7.8 0.3 – – 0.1 –

– – 3.9 0.2 1.9 64.1 18.7 9.2 0.6 1.0 – 0.2 0.2

– 0.9 24.7 0.7 2.3 17.6 53.3 0.3 0.1 – – – –

0.5 0.2 6.8 0.1 4.7 18.6 68.2 0.5 0.4 – – – –

– 0.1 11.6 0.2 3.1 46.5 31.4 – 1.5 1.4 0.1 3.0 1.0

Source: Adapted fro, Orthoefer (1996).

3.2.3

Fatty acid composition

Typical fatty acid (FA) composition of commodity soybean oil, in comparison with the other major vegetable oils, is shown in Table 3.3. Soybean oil has a relatively high content of linoleic and linolenic acid. These are both essential FA for humans and therefore of dietary importance, but they are also the cause of the oxidative instability of this oil. Processing techniques, such as hydrogenation and lipid modification through traditional plant breeding or genetic transformation, have been used to modify the FA composition to improve its oxidative or functional properties. The recent consumer demand for low-trans and no-trans oil has resulted in new soybeans with modified FA composition, as described later in this chapter. Triacylglycerols (TAG) are the primary neutral lipids in soybean oil. Due to the high concentration of unsaturated FA in natural soybean oil, nearly all the TAG molecules contain at least two unsaturated FAs, and di- and tri-saturates are essentially absent. In natural oils and fats, the FA are not usually randomly distributed among the three hydroxyl groups of glycerol, but are associated in particular patterns. Several theories of regiospecific distribution exist (Litchfield 1972), but the 1,3-random, 2-random theory is the most widely accepted. The stereospecific distribution of fatty acyl groups in soybean oils with a wide range of composition was studied by Harp and Hammond (1998), and some deviation from the previously established distribution model was found. In soybeans with typical FA composition, palmitic and stearic acids were associated more with the sn-1 position than with the sn-3 position, as shown in Table 3.4. When, however, the percentage of saturated acids increased, their accumulation at the sn-3 position was greater than at the sn-1 position. Linoleic acid showed a strong preference for the sn-2 position, but oleic acid was distributed relatively equally among the three positions. Linolenic acid had greater enrichment at the sn-2, followed by the sn-1 and sn-3 positions. To calculate the percentage of a particular molecular species present (e.g. ABC) in the oil, the equation %ABC = (% A at sn-1) × (% B at sn-2) × (% C at sn-3) × (10–4) can be used (Litchfield 1972).

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Table 3.4 Fatty acid composition (mole %) and stereospecific distribution of neutral and polar lipids of a commodity soybean. 16:0

18:0

18:1

18:2

18:3

sn-1 sn-2 sn-3

11.5 19.5 2.8 13.0

4.3 7.6 1.1 5.1

25.4 22.0 22.7 31.7

52.0 43.1 66.3 44.8

6.9 7.9 7.1 5.4

sn-1 sn-2

15.1 29.6 2.4

4.5 7.5 0.7

11.5 10.0 12.5

61.3 46.6 75.4

7.6 6.4 9.1

sn-1 sn-2

22.1 44.2 3.1

3.4 5.5 1.0

9.4 6.9 11.1

56.8 38.1 76.6

8.6 5.4 8.4

sn-1 sn-2

33.0 66.3 9.1

9.1 14.6 2.8

7.7 6.4 7.5

43.2 11.2 70.4

7.0 1.6 10.2

TAG

PC

PE

PI

Key: PC = phosphatidylcholines PE = phosphatidylethanolamines PI = phosphatidylinositols TAG = triacylglycerols

The regiospecific distribution of the fatty acyl groups may have a significant influence on the oxidative stability of the soybean oil. It was suggested that a high concentration of unsaturated FA at the sn-2 position stabilizes the oil against oxidation (Raghuveer and Hammond 1967; Lau et al. 1982) compared with structures having unsaturated FAs on the sn-1 and sn-3 positions. It was believed that TAG structure affected stability by altering the accessibility of the substrate to free radical attack. Konishi and co-workers (1995) also observed that normal soybean oil randomly interesterified with stearate was far less stable than when stearate was placed selectively on the sn-1 and sn-3 positions. However, Neff and List (1999) found that randomization of soybean oil TAG improved the oxidative stability compared to the natural soybean oil. More recent work by Wang and co-workers showed that randomized corn oil TAG oxidized much faster than natural oil, but after purification with alumina, they oxidized at the same rate (Wang et al. 2005). They have shown that this effect could not be attributed to the difference in total tocopherols in the randomized and natural oils. Polar material recovered from the alumina treatment was fractionated by TLC, and a pro-oxidant effect was found in the fractions containing MAG and DAG (mono- and di-acylglycerols). However, MAG and DAG, although mild pro-oxidants, could not account for the pro-oxidant effect generated by randomization. The pro-oxidant effect of randomized oil disappeared when EDTA or citric acid was added in sufficient amounts, and this pro-oxidant effect was increased by the incorporation of additional copper or iron ions at a concentration that did not catalyze oxidation of the purified oil. Although the identity of the pro-oxidant is still unknown, the authors have confirmed that it is produced during randomization. These findings should apply to both corn and soybean oils. A further investigation on the chemical nature and properties of the pro-oxidant produced during randomization should have a significant impact on the current practice of producing trans-free fat by

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interesterification, and methods of purification and removal of such processing contaminants. The relationship between TAG structure and its oxidative stability and how the regiospecific distribution affects the initiation, propagation, and termination of the lipid autoxidation still needs to be better understood.

3.2.4

Minor components

3.2.4.1

Phospholipids (PL)

PL are the major polar lipids in crude soybean oil. They are the primary components of cell membranes and play important roles in cell biological functions. The three major classes of PL in soybeans are phosphatidylcholines (PC), phosphatidylethanolamines (PE), and phosphatidylinositols (PI), present in the relative proportions of 55.3, 26.3, and 18.4%, respectively (Wang et al. 1997). Wang and co-workers (1997) and Wang and Hammond (1999) studied class composition, stereospecific distribution, and molecular species composition of PL in normal soybeans and in beans with genetically modified FA composition. It was shown (Table 3.4) that PI had higher palmitate and stearate percentages than did PC and PE, that PC had the lowest palmitate percentage, and that PE had the lowest stearate percentage. Stereospecific analysis indicated that saturated FA were concentrated at the sn-1 position, and the unsaturated FA preferred the sn-2 position of the PL molecules. 3.2.4.2

Sphingolipids

Sphingolipids are ubiquitous constituents of the cell membrane and are highly bioactive. The hydrolyzed products of sphingolipids are used by cells to regulate growth, differentiation, and apoptosis. There is evidence that sphingolipids inhibit colon carcinogenesis in experimental animals at a human diet-equivalent concentration. They may reduce colon cancer risk in humans (Vesper et al. 1999) and inhibit skin cancer development (Merrill and Schmelz 2001). Soybeans are a relatively rich source of sphingolipids (Vesper et al. 1999) and ceramides and cerebrosides are the primary sphingolipid classes (Ohnishi and Fujino 1982). Little was known about how sphingolipid content varies with soybean variety, maturity, and processing until the systematic work presented by Wang and co-workers (2006) and Guiterrez and Wang (2004). In their work, soybean seeds of three cultivars were harvested at five-day intervals from 28 days after flowering (DAF) to 68 DAF (mature seed), and sphingolipid and PL concentrations were found to decrease significantly during seed development. Averaged across cultivars, ceramide content on a dry-weight basis decreased from 51.4 nmol/g at 28 DAF to 22.2 nmol/g at 68 DAF, whereas cerebroside content decreased from 522.8 nmol/g at 28 DAF to 135.8 nmol/g at 68 DAF. PL percentage of the total lipid decreased from 9.1% at 28 DAF to 3.5% at 68 DAF. The effect of processing on sphingolipid content was also studied (Guiterrez and Wang 2004). Whole soybean was processed into full-fat flakes from which crude oil was extracted. Crude oil was refined by conventional methods, and defatted soy flakes were further processed into alcohol-washed and acid-washed soy protein concentrates (SPC) and soy protein isolate (SPI) by laboratory-scale methods that simulate industrial practices. It was found that cerebroside mostly remained with the defatted soy flakes (91%) rather than with the oil (9%) after oil extraction. Only 52%, 42%, and 26% of cerebroside from defatted soy flakes was recovered in the acid-washed SPC, alcohol-washed SPC, and

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Table 3.5

Sterol content (mg/100 g) of soybean oils.

Reference source

Sterol

Crude

Refined

b-Sitosterol Campesterol Stigmasterol D5-Avenasterol D7-Stigmasterol D7-Avenasterol

183 68 64 5 5 2

123 47 47 1 1 <0.5

Total

327

221

Weihrauch and Gardner (1978)

Vlahakis and Hazebroek (2000)

Table 3.6

b-Sitosterol Campesterol Stigmasterol

125–236 62–131 47–77

Total

235–405

Tocopherol content of crude soybean and wheatgerm oils. Mechanically pressed soybean oil

Total tocopherol, ppm a-Tocopherol, % b-Tocopherol, % g-Tocopherol, % d-Tocopherol, %

1257 9.3 1.2 62.8 26.7

Solvent extracted soybean oil 1370 10.5 1.2 63.5 25.0

Solvent extracted wheatgerm oil 2682 67.8 32.2 – –

SPI products, respectively. The minor quantity of cerebroside in the crude oil was almost completely removed by water degumming. 3.2.4.3

Unsaponifiable matter

The unsaponifiable matter (1.6%) in soybean oil includes several compounds, such as phytosterols (0.33%) and tocopherols (0.15–0.21%), both of which have important commercial value (Sipos and Szuhaj 1996a). Phytosterols, FA esters of phytosterols, and sterol glycosides are present in very low concentrations in soybean oil and are further reduced during refining. The composition of phytosterols in crude and refined soybean oils is shown in Table 3.5. Soybean germ oil, recovered from hypocotyl-enriched raw material, is a rich source of phytosterols (Ozawa et al. 2001), containing four times as much as does soybean oil. It may be an effective cholesterol-lowering functional oil (Sato et al. 2001). Tocopherols are minor components of most vegetable oils and are natural antioxidants with various degrees of effectiveness. There are at least four types of tocopherols in soybean oil. The γ-tocopherol is the major tocopherol, with the δ, α, and β compounds present in decreasing quantities (Table 3.6). Modification of soybean oil by plant breeding and molecular genetics can change the tocopherol content and composition, as discussed later in the chapter.

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Soybean genotype and growing environment have a significant effect not only on FA composition but also on the levels of health-enhancing minor compounds in the seed, as shown in eight soybean genotypes grown in three environments in Maryland (Whent et al. 2009). Phytosterol content in soybeans is affected by many factors. For example, in GM (genetically modified) soybeans with altered oil composition, the total sterol content increased when the growing temperature increased and the composition also changed (Vlahakis and Hazebroek 2000). For commodity soybeans planted in the Midwest, the planting locations also significantly affected the total phytosterol content, although no single parameter was responsible for the changes. In addition, no significant correlations occurred between either the sterol and tocopherol contents, or the sterol and FA unsaturation levels (Vlahakis and Hazebroek 2000). In two Japanese cultivars tested in different planting locations in Japan, sterol concentration tended to be greater in seeds harvested in warmer areas without the composition change, and there was no significant correlation between concentrations of tocopherols and phytosterols (Yamaya et al. 2007).

3.3 3.3.1

RECOVERY AND REFINING OF SOYBEAN OIL Oil extraction

The two common processes for soybean oil extraction are solvent extraction and mechanical pressing, but in the US less than 1% of soybeans is processed by mechanical means. Solvent extraction with hexane is the standard practice in today’s modern processing facilities, and its use has been reviewed by Johnson (2008). There are three major steps in solvent extraction: seed preparation, oil extraction, and desolventizing of the oil and meal. Conventional seed preparation includes drying, cleaning, cracking, optional dehulling or decortication, conditioning, and flaking of the seeds. The option of expanding after flaking is used to improve oil extraction, percolation, and solvent drainage, and is accompanied by a doubling of the throughput. In another variation in seed preparation (hot dehulling), hulls are removed from the split seeds by alternate slow and rapid heating before cracking and flaking. Hot dehulling is more energy efficient than conventional dehulling. The Alcon process (Penk 1986) is a flake-heating treatment aimed to improve the degumming efficiency of the crude oil. A very low-level PL in degummed oil can be achieved and the oil can then be physically refined. However, in the US the majority of soybean oil is chemically refined. Solvent (hexane) extraction of soybeans is a diffusion process achieved by immersing the solid in solvent or by percolating solvent through a bed of solids. Rotary (deep-bed), horizontal belt, and continuous-loop extractors are used for soybeans (Woerfel 1995). Solvent is recovered from the mixture of solvent and extracted oil (miscella) by a double-effect evaporator and steam stripping and from flake by a desolventizer-toaster, and is recycled. Solvent extraction in vegetable oil production has been recognized by the US Environmental Protection Agency (EPA) as a major hazardous air pollutant and National Emission Standards for Hazardous Air Pollutants (NESHAP) for oil extraction were established (Federal Register). In the 1970s, US extraction plants had typically 1 gallon solvent loss/ton of soybean seed (2.8 kg hexane/tonne) as standard. The new regulation is 0.2 gallon/ton (0.56 kg hexane/tonne). The design and operation of extractor, evaporator, and desolventizer-toaster thus become very important. The two major mechanical processes for soybeans are continuous screw pressing with prior extensive heating of the seeds and extrusion expelling (Nelson et al. 1987).

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Table 3.7 Quality comparison of oils and meals obtained by solvent-extracted, extruded-expelled, and screw-pressed soybeans.* Solvent extraction Oil PV, meq/kg FFA, % Phosphorus, ppm AOM stability, h Tocopherols, ppm Color, red Meal Oil,** % Protein,** % Fiber,** % Urease, DpH KOH solubility, % PDI Rumen bypass, % Hunter color ‘L’ Hunter color ‘a’ Trypsin inhibitor activity mg/g TIU/g

0.96 0.31 277 39.8 1365 11.1 1.2 48.8 3.7 0.04 89.1 44.5 36.0 69.1 2.0 5.46 5275

Extrusion expelling b ab b a a b b a b a a a b a b

Screw pressing

1.73 0.21 75 23.9 1257 10.2

a b c b b b

1.76 0.33 463 36.2 1217 17.5

a a a a b a

7.2 42.5 5.4 0.07 88.1 18.1 37.6 65.8 0.4

a b a a a b b a c

6.3 43.2 5.9 0.03 61.6 10.6 48.1 51.5 4.8

a b a a b c a b a

5.52 12254

0.30 2000

Source: Adapted from Wang and Johnson (2001a). Notes: * The values of each row with different letters are significantly different at 5%. ** Percentages are based on 12% moisture content. Key: PDI = protein dispersibility index TIU = trypsin inhibitor unit

Extrusion-expelling technology is used to process identity-preserved seeds for niche market soybean oil and protein products (Wang and Johnson 2001a). The advantages of small tonnage requirement (easy switchover for various types of seeds, no flammable solvent used, low initial capital investment, and unique products) have made this processing technology very appealing for many soybean growers and processors. Quality comparisons of crude oils and meals obtained by solvent and mechanical extraction are presented in Table 3.7. Although mechanical pressing of soybeans accounts for only a very small percentage of soybean processing, it is used by many farm cooperatives or family-owned on-farm operations in the US, primarily to produce protein meals for use as animal feed. Oilseed aqueous processing has been gaining in popularity as an environmentally friendly and green alternative to hexane extraction. A group at Iowa State University has been using mechanical and enzymatic means to recover oil from optimized laboratory-scale and pilot plant-scale processing (Nobrega de Moura et al. 2008; Nobrega de Moura and Johnson 2009; Jung et al. 2009). The dehulled and extruded soybean flake is mixed with water and protease is then added to destabilize the oil-in-water emulsion. Centrifugation recovers the cream fraction that contains the oil and the skim fraction has the soluble protein. The precipitate contains the fiber and some insoluble proteins. The cream is then further enzyme

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treated and centrifuged to remove the oil. Oil obtained by this means is low in PL and free fatty acids (FFA). The essential step in this processing is the enzymatic degradation of the cell walls and emulsion particles to release the oil. Enzymes can increase the oil recovery from 60% to 82% (Lamsal and Johnson 2007). Figure 3.2 shows the main steps of the aqueous process and also the integrated biorefinery system with corn ethanol fermentation. The principal advantages of this integrated system are the full utilization of water or liquid fraction from the aqueous soybean fractionation and the improved nutritional value of the corn fermentation by-product; that is, the dry distillers’ grain having increased protein content from the soybean steam. An aqueous procedure to fractionate the intact oleosomes from soybeans to produce oil without the use of organic solvents was also investigated at Iowa State University (Kapchie et al. 2008). Commercial enzyme mixtures containing cellulase and pectinase were used and up to 85% oil was recovered in the oleosomes. Oil extracted as such is expected to have different characteristics and the oleosin protein may have unique applications as well.

3.3.2

Oil refining

The non-TAG portion of soybean oil includes PL, FFA, chlorophyll pigment, oxidation products, and other unsaponifiable components such as tocopherols, sterols, and hydrocarbons. Some of these minor components negatively affect oil quality, while some may play a positive role in nutrition and function. The goal of refining is therefore to remove the undesirable components and, at the same time, to maximize retention of the beneficial components. 3.3.2.1

Degumming

Degumming is a process for removing PL (gums) from crude soybean oil, to improve its physical stability and to facilitate further refining. The water degumming procedure is simple, but its efficacy is influenced by the quality of crude oil. PL can exist in hydratable form that can be readily removed after addition of water, or in non-hydratable form that cannot be removed by this procedure. The non-hydratable PL (NHP) are probably calcium and magnesium salts of phosphatidic acids, resulting from enzymatic hydrolysis of the PL. This degradation results from seed damage during storage and handling or from improper seed preparation. List and co-workers (1992) showed that four interrelated factors promote NHP formation: (i) moisture content of beans or flakes; (ii) phospholipase D activity; (iii) heat applied to beans or flakes prior to and during extraction; and (iv) disruption of the cellular structure by cracking and/or flaking. These results suggest that NHP formation can be minimized by control of the moisture of beans and/or flakes entering the extraction process, by inactivation of phospholipase D enzyme, and by optimizing the temperature during the conditioning of cracked beans or flakes. Normal-quality soybean oil from conventional solvent extraction has about 90% hydratable PL and 10% NHP. Phosphoric acid or citric acid can be used as an aid for more complete removal of NHP, but its presence in the gum will reduce its quality due to darkening. Total PL in crude soybean oils ranges from 1.1–3.2%. The quantity of PL in the crude oil depends on the extraction method, particularly seed preparation before solvent extraction. Use of an expander or Alcon process will increase total PL content in the crude oil and increase the proportion of PC in the gum (Kock 1983). Degumming can be achieved in batch or continuous fashion. In batch degumming, soft water at the same percentage as total PL is added to heated (70 °C) oil and mixed thoroughly

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Ethanol or Industrial Chemicals

Distilling/ Separating

Figure 3.2 Flow chart of soybean aqueous processing integrated with corn fermentation. Source: Iowa State University, Center for Crops Utilization Research.

Adhesives, Food or Feed (swine, poultry, fish)

Spray Drying

Fermenting

Saccharifying

Pretreating

Membrane Filtering

Glycerol Enhanced Feed

Enzyme

2nd Skim

Demulsifying

Insoluble Fiber

Galactosidase Treating

Drying

Free Oil

Biodiesel

Methanol

Edible Oil

EAEP of Soybeans

Transesterifying

Enzyme

Biomaterials

Cream

Hulls

Centrifuging

Enzyme-assisted Aqueous Extracting

Extruding

Flaking

Aspirating

Cracking

Soybeans

Skim

Water

Liquid Feed Jet Protein Concentrate Cooking (baby pigs and calves)

Oil to Ethanol Enhanced TransDDGS Feed esterificication (swine, poultry, fish)

Fermenting and Other Dry-grind Ethanol Operations

Saccharifying (Including galactosidase)

Grinding

Corn

Existing Dry-grind Ethanol Plant

Soybean Oil

69

for 30–60 min, followed by settling or centrifuging. In continuous water degumming, heated oil is mixed with water by an in-line proportioning and mixing system and the mixture is held in a retention vessel for 15–30 min before centrifugation. A well-degummed soybean oil should contain less than 50 ppm of phosphorus, well below the 200 ppm level specified in the National Oilseed Processors’ Association trading rules for crude degummed soybean oil. A commonly used calculation to convert phosphorus concentration to that of phospholipids is to apply a multiplication factor of 30. Degumming, prior to physical refining of soybean oil, requires a more complete removal of the PL to prevent darkening during FA distillation, and several modified degumming methods have been described (Seger and van de Sande 1990; Dijkstra 1992). Recently, polymeric ultrafiltration membranes have been used for degumming crude soybean oil. This is based on the mechanism that in non-polar media such as hexane, PL molecules tend to form reverse micelles with an average molecular size of 20 000 Da, compared to the much smaller TAG molecules with 800 Da that are dissolved in the hexane. In the membrane-separation process, the TAG and hexane mixture – that is, miscella – is ultrafiltered by using appropriate membranes and PL are left behind. This technology is simple, less energy intensive, with no chemical addition and no wastewater generation. Pagliero and co-workers (2001) showed that membranes were suitable for removing PL from the miscella. When surfactant-aided membrane degumming was applied to crude soybean oil, the degummed oil contained 20–58 ppm of phosphorus (Subramanian et al. 1999). Soybean miscella was ultrafiltered by using ceramic membrane of zirconium oxide with a molecular weight cut-off of 20 KDa, and the results showed that more than 95% of PL was removed during this treatment (Wang et al. 2006). Degumming of soybean oil miscella was also performed by ultrafiltration using a multichannel ceramic membrane with response surface methodology for process optimization (Ribeiro et al. 2008). The phosphorous concentration in the degummed oil was 2.2 ppm, indicating a 99.7% removal, and the highest permeate flux was obtained at 2 bar pressure. Sensory differences in flavor attributes evaluated by consumers for soybean oil degummed by ceramic ultrafiltration vs. traditionally RBD (refined, bleached, and deodorized) oil were reported (Soares et al. 2004), and these two oils did not show significant differences. Supercritical CO2 extraction (List et al. 1993) and ultrasonic degumming (Moulton and Mounts 1990) were also successfully used to reduce the gum content of soybean oil. Enzymatic degumming of vegetable oil is a relatively new process. In general, a phospholipase converts PL into lyso-PL, which is more water dispersible and can be more easily removed by water and centrifugation. The main advantages of enzymatic degumming are better oil yield, mild reaction conditions, high specificity of the enzymes, and low phosphorus and iron in the degummed oil. A review by Muench (2005) describes degumming processes using phospholipase A1, commercially available as Novozymes Lecitase Ultra, and with the addition of citric acid for oils from soybean, rapeseed, and sunflower. Citric acid was found helpful in enzymatic degumming with Lecitase Ultra (Yang et al. 2005). Soybean oil was enzyme degummed with phospholipase A1 (Pan et al. 2008), and the feasibility and optimization study showed the optimum conditions as enzyme dosage of 4%, at temperature of 49–52 °C and pH of 4.9–5.2, water content of 2–2.5%, and mixing speed of 125 rpm. The residual phosphorus content decreased to less than 10 ppm. The Lecitase Ultra has proven to be a suitable phospholipase used for soybean oil degumming. The enzymatic degumming of soybean oil has been carried out at a capacity of 400 tons/day at pH 4.8–5.1 by applying microbial phospholipase A1 from Thermomyces lanuginosus and Fusarium oxysporum (Yang et al. 2008). Oil with a phosphorous content less than 10 ppm was obtained and the gum separation was easy. Phospholipase C was also used to form DAG for modified

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degumming (Meng and Wen 2006). In such a process the diffusion rate was the restriction step of hydrolysis and certain optimum processing conditions were established. 3.3.2.2

Neutralization

Neutralization is also described as deacidification or caustic refining. It is achieved by treating the soybean oil with aqueous alkaline solution (generally sodium hydroxide) to neutralize the FFA in a batch or continuous system. The soap formed in the reaction also adsorbs natural pigments, unhydrated gum, and mucilaginous substances contained in the oil. Settling or centrifugation is used to remove the soap. More details on soybean oil neutralization are discussed by Erickson (1995a). 3.3.2.3

Bleaching

Bleaching is a process designed not only to remove the pigment (chlorophyll) but, more importantly, to break down peroxides (primary oxidation products) into lower molecular weight carbonyl compounds that can be subsequently removed by deodorization. In soybean oil refining, color reduction occurs at each step of the degumming, neutralization, bleaching, hydrogenation, and deodorization processes. Nevertheless, the most significant reduction of chlorophyll, which is involved in photosensitized oxidation of soybean oil, is in the bleaching step. Acid-activated bleaching clay is most effective in adsorbing chlorophyll and decomposing peroxides. Low levels of phosphorus (5–10 ppm P) and soap (10–30 ppm) in the neutralized oil are required to maximize the bleaching effect. The desired bleaching end point is zero peroxide, so the amount of bleaching earth should be adjusted to the quality of oil to be bleached. Earth dosage ranges from 0.3–0.6% for typical soybean oil. Successful bleaching can be achieved by atmospheric batch bleaching, vacuum batch bleaching, or continuous vacuum bleaching at temperatures between 100 °C and 120 °C for 20–30 min. More details of soybean oil bleaching are described by Erickson (1995b). 3.3.2.4

Deodorization

Deodorization, usually the last step in oil refining, is a steam-stripping process in which good-quality steam (1–3% of oil), generated from deaerated and properly treated feed water, is injected into soybean oil under high temperature (252–266 °C) and high vacuum (<6mmHg). Under these conditions peroxides are decomposed and the FFA and odorous compounds are vaporized. Heat bleaching is achieved by holding the oil for 15–60 min at high temperature to ensure considerable decomposition of carotenoid pigments. During the deodorization process many desirable reactions are taking place, but there are also some undesirable reactions such as lipid hydrolysis, polymerization, and isomerization. Therefore, the deodorization temperature must be carefully controlled to achieve optimum-quality finished soybean oil. Kemeny and co-workers (2001) studied the kinetics of the formation of trans linoleic acid and trans linolenic acid in vegetable oils during deodorization at temperatures of 204–230 °C for 2–86 h. Applying the established model, the trans FA level of refined oils can be predicted for given deodorization conditions. The conditions to meet increasingly strict consumer demands concerning the trans isomer content can be calculated and the deodorizer design can be modified and optimized. There are three types of deodorization operations. The batch process is the least common, due to its low efficiency and inconsistent product quality. Semi-continuous and

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Soybean Oil Table 3.8

71

Effect of processing steps on quality of soybean oil.

Crude Degummed Refined Bleached Deodorized

Phosphorus (ppm)

Iron (ppm)

Free fatty acid (%)

Peroxide value (meq/kg)

Tocopherol (ppm)

510 120 5 1 1

2.9 0.8 0.6 0.3 0.3

0.74 0.36 0.02 0.03 0.02

2.4 10.5 8.8 16.5 0.0

1670 1579 1546 1467 1138

Source: Adapted from Jung et al. (1989).

Table 3.9 Effect of processing on content of tocopherols, sterols, and squalene in soybean oil. Processing step

Crude Degummed Neutralized Bleached Deodorized

Tocopherols

Sterols

Squalene

ppm

% Loss

ppm

% Loss

ppm

% Loss

1132 1116 997 863 726

– 1.4 11.9 23.8 35.9

3870 3730 3010 3050 2620

– 3.6 22.2 21.2 32.3

143 142 140 137 89

– 0.7 2.1 4.2 37.8

Source: Adapted from Ramamurthi et al. (1998).

continuous deodorizers have improved processing efficiency. There are several configurations of the continuous deodorizer, including the single-shell cylindrical vessel type, the vertically stacked tray type, and the thin-film packed column type. This last provides excellent FA stripping with minimum use of steam, but it achieves neither desired heat bleaching nor effective deodorization due to the relatively short retention time. A retention vessel has to be used after the column distillation (De Greyt and Kellens 2000). Changes in oil quality during refining of soybean oil (Jung et al. 1989) are shown in Table 3.8. A study of oxidative stability of soybean oil at different stages of refining indicated that crude oil was the most stable and highly purified oil the least stable (Kwon et al. 1984). Ferrari et al. (1996) and Ramamurthi and co-workers (1998) studied changes in the composition of minor components during refining, with the results shown in Table 3.9. To purify a heat-sensitive oil, an adsorbent column of silica gel was hydrated and used for deodorization and deacidification of degummed and bleached soybean oil (Nasirullah 2002). Oil was then sequentially eluted with solvents of increasing polarity. Earlier fractions showed good sensory properties and this may be a suitable means for small amounts of highly oxidizable and valuable oil.

3.3.3

Modified non-alkaline refining

Alternative techniques of vegetable oil refining have been developed. Simple refining methods were explored to process extruded-expelled soybean oils with various FA compositions (Wang and Johnson 2001b, c). Such oils can be easily water-degummed to low phosphorus

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– – 2–3 – max 1 trace max 1.5 10–15

4–7 5–8 – 2–3 max 1 max 1 max 1.5 35–40

Sources: * Wendel (1995); ** Schneider (2008).

65–70 9–13 – – – 2–4 2–4

Egg*

10–15 9–12 8–10 1–2 2–3 1–2 1–2

Soybean*

Composition of commercial lecithins, wt %.

Phosphatidylcholine Phosphatidylethanolamine Phosphatidylinositol Phosphatidylserine Phosphatidic acid Lysophosphatidylcholine Lysophosphatidylethanolamine Total lysophospholipids Phytoglycolipids Other phosphorus-containing lipids Sphingomyelin Carbohydrate Free fatty acids Mono- and di-acylglycerols Water Triacylglycerols Others

Compounds

Table 3.10

19

19

25 22 15

Rapeseed**

1

3

25 11 19

Sunflowerseed**

5

30 3 16 1 9

Corn**

4

29

27 30 2 7 1

Milk**

2

2 1

86 6 2

Salmon roe**

Soybean Oil

73

levels. FFA were reduced to 0.04% by adsorption with Magnesol, a commercial magnesium silicate product. This material also adsorbed primary and secondary lipid oxidation products. A final mild steam deodorization produced good-quality soybean oil. This adsorption refining procedure is much milder than conventional refining, as indicated by the low formation of primary and secondary lipid oxidation products and reduced loss of tocopherol. Sodium silicate was also used as a mild neutralizing agent to refine specialty oils (Hernandez 2001). Its agglomerating property allowed the removal of the soap by filtration, and its low alkalinity minimized saponification of neutral oil and loss of minor nutrients.

3.3.4

Co-products from oil refining

3.3.4.1

Lecithin

Soybean is the predominant source of lecithin for pharmaceutical and food purposes because of its availability and outstanding functionality. The composition of crude soy lecithin as compared to others is shown in Table 3.10. It contains a large amount of neutral oil, and crude lecithin is usually deoiled to improve its functionality. This separation is based on the solubility difference of neutral and polar lipids in acetone. PL are precipitated from the acetone solution and separated. Alcohol fractionation of deoiled lecithin provides alcohol-soluble and alcohol-insoluble fractions enriched with PC and PI respectively. The PC-enriched fraction is an excellent oilin-water emulsifier. The PI-enriched fraction is a good water-in-oil emulsifier often used in the chocolate industry to increase the viscosity of the mass, therefore reducing the need for cocoa butter. The typical composition of these further fractionated lecithin products is shown in Table 3.11. Lecithin recovered from solvent-extracted and mechanically pressed soybean oils have different PL class compositions (Wu and Wang 2001). The percentage of PC was considerably higher in lecithin recovered from extruded-expelled oil than from solventextracted oil. Supercritical CO2 extraction has been used to extract PC from deoiled soybean lecithin selectively (Teberikler et al. 2001). The effects of temperature, pressure, and amount of ethanol on PC extraction were examined and optimum conditions described to yield a highpurity product. Soybean lecithins can be chemically altered to modify their emulsifying properties and to improve their dispersibility in aqueous systems. PL may be hydrolyzed by acid, base, or enzyme (phospholipase A) to achieve better hydrophilic and emulsification properties. Hydroxylation of lecithin improves its oil-in-water emulsification property and water dispersibility. Acetylation (of PE) creates improved fluid, emulsification, and water dispersion (van Nieuwenhuyzen and Tomas 2008; Schneider 2008). The utilization of soybean lecithins is reviewed by Schneider (1986, 2008). Table 3.12 summarizes the most common applications in the food, feed, cosmetic, and pharmaceutical industries. The food industry relies on lecithin in bakery, beverage, and confectionery product development because of its functionalities. There has been a recent dramatic increase in interest in lecithin from the nutritional industry, which has led to the development of new processes and new raw materials, such as membrane deoiling, and lecithin from egg, milk, marine, and brain sources (Schneider 2008). Many nutritional and clinical trials have shown the effects of PL in the prevention or treatment of certain disease conditions. However, the present challenges in the soybean

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Table 3.11

Typical composition (%) of commercially refined lecithin products. Lecithin, oil free

Phosphatidylcholines Phosphatidylethanolamines Phosphatidylinositols and glycolipids Neutral oil Others Emulsion type favored

Lecithin, alcohol soluble

Lecithin, alcohol insoluble

29 29 32

60 30 2

4 29 55

3 7 w/o or o/w

4 4 o/w

4 8 w/o

Source: Adapted from Brekke (1980).

Table 3.12

Uses and functions of soybean lecithins.

Product

Function

Food Instant food Baked goods Chocolate Margarine Dietetics

Wetting and dispersing agent; emulsifier Modification of baking properties; emulsifier; antioxidant Viscosity reduction; antioxidant Emulsifier; antispattering agent; antioxidant Nutritional supplement

Feedstuffs and technical Calf milk replacer Insecticides Paints Magnetic tapes Leather Textile

Wetting and dispersing agent; emulsifier Emulsifier; dispersing agent; active substance Dispersing agent; stabilizer Dispersing agent; emulsifier Softening agent; oil penetrant Softening; lubricant

Cosmetics Hair care Skin care

Foam stabilizer; emollient Emulsifier; emollient, refatting, wetting agent

Pharmaceuticals Parental nutrition Suppositories Creams, lotions

Emulsifier Softening agent; carrier Emulsifier; penetration improver

Sources: Adapted from Schneider (1986, 2008).

lecithin industry are genetic modification (GM) and novel food issues related to lecithin sourcing and processing in European countries. All new food ingredients from new processes that have not been in use prior to the 1997 Novel Food Regulation have to go through a costly approval procedure. Pure molecular PL should be similar to the fully refined soybean oil, not containing any DNA material. However, the inevitable contamination of lecithin with soy protein makes lecithin from GM soybeans a seemingly important safety or regulatory issue. Since even highly

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Table 3.13

75

Composition (wt %) of deodorizer distillate from various oils.

% Unsaponifiable Total tocopherol a-Tocopherol Total sterol Stigmasterol

Soybean

Sunflower

Cotton

Rapeseed

33.0 11.1 0.9 18.0 4.4

39.0 9.3 5.7 18.0 2.9

42.0 11.4 6.3 20.0 0.3

35.0 8.2 1.4 14.8 1.8

Source: Adapted from Winters (1990).

processed GM-derived food products are covered by the new European legislation, a great effort has been devoted to the application of analytical tests to these products. A GM-lecithin detection method in margarines has been developed (Gryson et al. 2003), and GM soybean components could be monitored during processing. A PCR (polymerase chain reaction)-based screening assay and a biosensor-based approach were used to detect transgenes in Roundup Ready soybeans, including crushed seeds, crude flour, protein flour, crude oil, degummed oil, and lecithin (Bogani et al. 2009). The amplification of marker fragments with a maximal length of 500 bp was successfully achieved both in raw material (seeds or flour) and in partially and highly processed materials, such as crude and degummed oil and fluid lecithin. The detection of GM soybeans in processed soy foods was also successfully performed with realtime PCR using intercalator SYBR Green I (Miyazaki and Tamura 2007). The relationship between GM and soybean allergenicity should also be noted. Soybean is a birch pollen-related allergenic food, and the threshold dose in soy-allergic individuals ranges from 10 mg to 50 g of soybean, which is more than one order of magnitude higher than in peanut allergy (Ballmer-Weber and Vieths 2008). The potential allergenicity of newly introduced proteins in GM soybeans has been studied and it was shown that there were no differences in IgE-antigen binding by immunoblotting between GM and the corresponding non-GM soybean samples, so no known allergen was found (Kim et al. 2006). 3.3.4.2

Deodorizer distillate

Soybean deodorizer distillate (SBDD) is the material collected from the steam distillation of soybean oil. It is a mixture of FFAs (particularly during physical refining), tocopherols, phytosterols and their esters, hydrocarbons, and secondary lipid oxidation products. The quality and composition of SBDD depend on feedstock oil composition and on processing conditions. Tocopherols and sterols are valuable components that can be further separated from the distillate and used in the nutrition-supplement and pharmaceutical industries (Pickard et al. 1996), therefore SBDD from chemically refined oil has a high economic value. The total tocopherol concentration in fully refined soybean can be reduced to 800– 1100 ppm without significant change in tocopherol composition (Jung et al. 1989). Chemical refining promotes a more significant reduction than physical refining and the higher temperatures and longer deodorization times typically cause greater tocopherol loss. Table 3.13 shows the composition of deodorizer distillates from soybean oil and other vegetable oils. Soybean tocopherols are the major natural fat-soluble antioxidants and vitamin E. The human body has a strong preference for the absorption of natural d-a-tocopherol. Synthetic vitamin E is less active because it is a mixture of eight different stereoisomers (Clark and

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Frandsen 1998). Tocopherols, present in oil or fractionated from the SBDD and then added to oil as antioxidants or health supplements, act as a free radical-quenching primary antioxidant. The tocopherol analogs vary in their antioxidant activities and the relative biopotency. For example, a-tocopherol had the highest relative in vivo antioxidant activity, followed in order by b-, g-, and d- analogs, because the a-form is best absorbed, whereas under in vitro conditions the results were different (Kamal-Eldin and Appelqvist 1996). When tested in linoleic acid and linoleic acid methyl ester at 37 °C and 47 °C, g-tocopherol was more effective than a-tocopherol (Gottstein and Grosch 1990). Tocopherol stability and antioxidant activity were tested in corn oil heated at 70 °C, and the order of the antioxidant activity was g->d->b->a-tocopherol (Chow and Draper 1974). In general, when tested in oils, fats, and lipoproteins, the order of the antioxidant activity is in the opposite direction from that obtained with in vivo studies. For soybean oil to have the best oxidative stability, the tocopherols need to be at optimal concentrations, and such values were found to be 100, 250, and 500 ppm for a-, g-, and d-tocopherol, respectively, when tested individually in the dark at 55 °C (Jung and Min 1990). Similarly, at temperatures ranging from 40 °C to 60 °C in the dark, optimal concentrations for a- and g-tocopherols were about 100 and 300 ppm; however, d-tocopherol did not exhibit an optimum concentration under these conditions (Evans et al. 2002). At high concentration, these compounds can act as pro-oxidants, especially in the presence of other oxidation-promoting compounds, such as peroxides or metals (Kamal-Eldin and Appelqvist 1996). Warner (2005) used tocopherol-stripped soybean and sunflower oils to test tocopherols in the typical composition occurring naturally in these oils. At 60 °C in the dark, soybean and sunflower oils with typical soybean tocopherol composition (low a- and high g- and d-) had better oxidative stabilities than did those with the typical sunflower tocopherol composition (high a- and low g- and d-). However, when tested under light at 30 °C, oils with high a-tocopherol (sunflower composition) were more stable than oils with high g- and d- (soybean composition), possibly due to a higher capacity of the a-analog in slowing singlet oxygen-mediated photo-oxidation (Warner 2005). Up to 30% of phytosterols can be removed from the crude soybean oil during refining, and the neutralization step typically causes the most loss (about 20% of the total). These compounds in the SBDD are typically free sterols, because sterol esters are not as volatile. Phytosterols naturally present in vegetable oils or added for health promotion may be degraded, especially during high-temperature and long-duration frying. A study by Winkler and co-workers (2007) showed that phytosterol loss ranged between 4% and 6% in continuous frying systems with various types of oils; in batch frying, the loss ranged from 1% to 15%. Such phytosterol loss in both frying systems was unrelated either to the FA composition of the oil or the extent of degradation of the oil. Phytosterols are used as raw materials for over 75% of the world’s steroid production. The more recent application of phytosterol and phytostanol and their FA esters in margarine and table spreads is related to the cholesterol-lowering effect of these compounds (Law 2000; Normen et al. 2000). Hollingsworth (2001) and Hicks and Moreau (2001) reviewed the recent development of functional foods containing phytosterols. Besides the cholesterollowering effect of phytosterols, soy phytosterols are used as nutracosmeceuticals (Carmelo and Francesco 2008), because the absorption and distribution bring them from the plasma to the skin, where they play an important role in the constitution of skin-surface lipids. The skin’s uppermost thin layer, the stratum corneum, plays a crucial role in protecting the body against unwanted influences from the environment. Topical application of soybean sterols had positive results on the repair of damaged skin (Carmelo and Francesco 2008) in a model

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system. For food uses, a water-dispersible plant phytosterols powder can be prepared using emulsifiers, thickeners, homogenization, and spray-drying (Auriou 2003). Preparation of high-purity tocopherols and phytosterols from SBDD involves a series of physical and chemical processing steps, such as molecular distillation, adduct formation, liquid–liquid extraction, supercritical fluid extraction, saponification, and chromatography (Ramamurthi et al. 1998). Extraction of tocopherols from SBDD by urea inclusion and saponification resulted in a high recovery of tocopherols (Wu et al. 2001). To improve the separation of sterols and tocopherols, Shimada and co-workers (2000) used a lipase to esterify sterols with FFA. The sterol esters and tocopherols are then better separated from one another by molecular distillation. Chang and co-workers (2000) used supercritical fluid CO2 extraction to recover tocopherols and sterols from SBDD. An isolation process for sterols and tocopherols is also reported in a patent (Sumner et al. 1995), in which treatment of the distillate with methanol converts FA esters into FA methyl esters, which can then be removed by a stripping operation. Separation of sterols and tocopherols was subsequently carried out by molecular distillation. 3.3.4.3

Soapstock

Soap is recovered after alkaline neutralization of the crude or degummed soybean oil. The neutralizate consists of water, FFA, neutral oil, PL, unsaponifiable matter, proteins, and mucilaginous substances. Its composition depends on seed quality, oil extraction and refining conditions, and efficiencies. Soapstock is the lowest-priced by-product from oil processing and is generated at a rate of about 6% of the volume of crude oil refined (Golbitz 2000), amounting to as much as 1.8 billion pounds (0.9 million tonnes) in the US annually. The majority of the soap or the acidulated soap is used as feed. Soybean oil can also be refined using caustic potash (KOH) and acidulated with sulfuric acid, followed by neutralization with ammonia rather than NaOH. In this way the potassium and ammonium salts in the wastes can be used as fertilizer (Daniels 1989). Soybean oil methyl esters can also be produced from soapstock for biodiesel application (Stern et al. 1986; Basu and Norris 1996; Haas and Scott 1996; Haas et al. 2000).

3.3.5

Fatty acid esters of glycidol and 3-monochloro-1, 2-propanediol as processing contaminants

Soybean oil and its processed products may contain certain contaminants that are generated by refining and further chemical processing. Glycidol (2,3-epoxypropanol) is a compound that contains both epoxide and alcohol functional groups, so it is bifunctional and active in various in vitro or in vivo reactions. Two earlier Russian studies (Ivanov et al. 1980; Mel’nikova and Klyachkina 1979) showed that the acute oral LD50 of glycidol for mice was 431 mg/kg. A toxicological study showed that when glycidol was administered by gavage to mice in 37.5 to 600 mg/kg, the animals in the highest dosage group died by day 4 of the study (Irwin 1990). Glycidol fatty acid esters are process contaminants found in vegetable oils, probably formed during high-temperature deodorization. Although there is no validated quantification method or toxicological data on glycidol esters, the free form is considered to be probably carcinogenic to humans by the International Agency for Research on Cancer of the World Health Organization. However, there is no information about the fate of glycidol esters in the human digestive tract.

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The Federal Institute for Risk Assessment (BfR), a scientific agency of the Federal Republic of Germany, recently reported the detection of glycidol fatty acid esters (GE), and this triggered a study on developing analytical methodology to quantify these compounds accurately. One method, using double solid-phase extractions and LC-MS measurements (Masukawa et al. 2010), was used to determine trace levels of GE such as glycidol palmitic, stearic, oleic, linoleic, and linolenic acid esters. Three samples of commercial edible oils sold in Japan were collected and analyzed and GE were present in all samples tested. Surprisingly, the GE in the single diacylglycerol oil was much higher (269 ppm) than that in the two triacylglycerol oils (22.3 and 5.7 ppm). The German BfR agency recommended in 2009 that infant formula manufacturers need to reduce the level of glycidol fatty acid esters in infant formula, because animal studies suggest that free (unbound) glycidol is carcinogenic. BfR noted that there is no toxicological evidence suggesting that bound (esterified) glycidol is a health risk. Nonetheless, it made a worst-case risk assessment assuming that all glycidol esters are metabolized into free glycidol. This action by BfR prompted Japan’s Food Safety Commission to take action regarding glycidol esters in August 2009. Japan’s Kao Corp has temporarily suspended shipments of its diacylglycerol products, including cooking oil, salad dressings, and mayonnaise, because of the presence within them of high levels of glycidol fatty acid esters. The suspension will continue until the amounts of glycidol esters contained in these products can be lowered to levels found in common cooking oils. Another compound with a similar structure, 3-monochloro-1,2-propanediol (3-MCPD), is a known food-processing contaminant with a maximum tolerable daily intake of 2 mg/kg body weight, as recommended by the European Scientific Committee on Food (Masukawa et al. 2010). It is detected in various types of processed food, and it has been reported that some edible oils contain relatively high levels of 3-MCPD and/or 3-MCPD fatty acid esters. 3-MCPD-esters can be formed when fats or fat-containing foods containing salt or other sources of chloride ion are exposed to high temperatures during manufacturing processes. Recently it has been shown that other substances, such as glycidol in oil and fats, can be converted into 3-MCPD. In 2007, the German official food control and animal health laboratory reported significant amounts of 3-MCPD fatty acid esters in refined edible oils and fats, as well as in foods containing refined fat such as infant formula, the amount ranging from 0.5 to 10 ppm (AOCS website). The heath risk posed by MCPD esters is also ambiguous. Tolerable daily intake for 3-MCPD of 2 mg/kg body weight was used for the assessment of 3-MCPD esters; however, toxicological studies were not available to demonstrate the fate of the esters in the human system. In late 2009, numerous news reports were released on the American Oil Chemists’ Society’s (AOCS) website, regarding the presence of 3-MCPD esters found in all refined vegetable oils and fats. The Malaysian Palm Oil Board has proposed research strategies to further develop analytical methods to understand the mechanisms of the formation of 3-MCPD esters and glycidol esters at different refining conditions, and to conduct toxicological studies with other research institutions. The vegetable oil industry is working on mitigation, and food safety bodies such as the US Food and Drug Administration and the European Food Safety Authority have called for more research before setting any regulatory limits on these esters in food products. AOCS has formed an Expert Panel for Process Contaminants. The panel will focus on the accurate measurement of fatty acid esters of 3-MCPD and glycidol, and technical communication and information dissemination.

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3.4

79

OIL COMPOSITION MODIFICATION BY PROCESSING AND BIOTECHNOLOGY

To extend its food applications, soybean oil is often modified by chemical or genetic means. The primary objective of these changes is to improve its physical, chemical, and functional properties.

3.4.1

Hydrogenation

The high degree of unsaturation of soybean oil, and particularly the significant level of linolenic acid, limits its food application because of its low oxidative stability. Partial hydrogenation is used to increase the melting temperature and, at the same time, to improve the oxidative stability of soybean oil. When oil is treated with hydrogen gas in the presence of a catalyst (nickel) under appropriate agitation and temperature conditions, it becomes a semi-solid or plastic fat, suitable for many food applications. Selectivity is the term used to describe the relative reaction rates of the FA from the more unsaturated to the more saturated forms. Perfect selectivity provides sequential elimination of unsaturated acids as follows: Linolenic→Linoleic→Oleic→Stearic Generally, selectivity increases with temperature and catalyst concentration and decreases with hydrogen pressure and agitation rate (Erickson and Erickson 1995). The effect of pressure on the hydrogenation selectivity of soybean oil was reported by List and co-workers (2000). They showed that the linoleate-containing TAGs were reduced at a much faster rate than the linolenate-containing triacylglycerols under their experimental conditions. Pressure had a significant effect on the course of hydrogenation. At higher pressures (500 psi) the reaction is truly nonselective, whereas at 50 psi the reaction becomes selective. More comprehensive reviews of reaction and formulation can be found in Erickson and Erickson (1995), Hastert (1996), and Kellens (2000). During hydrogenation various side-reactions occur, some of which have a strong impact on the physical and nutritional properties of the products. Double-bond isomerization and trans-FA formation are the most important side-reactions. The trans double bond is a thermodynamically more stable configuration than its cis counterpart, and it is produced in significant quantity during partial hydrogenation. The trans FA have a much higher melting point than their cis isomers, therefore fat products with considerable trans FA will have elevated melting points, which is desirable in shortening and margarine applications. However, the recently established link between trans fat consumption and ill health has prompted research to minimize double-bond isomerization during partial hydrogenation. Low-trans hydrogenation can be achieved by modifying hydrogenation process conditions and by applying alternative low-trans heterogeneous catalysts (Beers 2007). Typically the hydrogenation process is carried out in a batch autoclave with H2 at 0.5–2 bars (about 8–30 psi) and at temperatures of 140–200 °C in the presence of a heterogeneous nickelcontaining catalyst. Under this condition, up to 45% trans isomers may be formed. Since the isomerization reaction is strongly influenced by temperature, lowering the temperature can significantly lower trans isomer formation, as shown in Figure 3.3.

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Composition (%)

14 12 Trans-isomer formation (wt%) Saturate formation (%) Linolenic acid (%)

10 8 6 4 2 0

0

50

100

150

200

Temperature (8C)

Figure 3.3 Effect of temperature on the performance of a nickel catalyst in the hydrogenation of soybean oil to an iodine value of 105 at 2–4 bars (30–60 psi) of hydrogen pressure. Source: Reproduced from Beers (2007) with the permission of Wiley-VCH Verlag.

As the figure shows, by lowering the temperature to 40–60 °C it is possible to reduce trans to 6%. Unfortunately, reducing trans formation by lowering the temperature also increases the saturate formation, indicating less selectivity. Increasing H2 pressure leads to higher H2 concentration on the catalyst surface, therefore decreasing trans formation. However, to reduce trans to lower than 10%, more than 60 bars (about 900 psi) of H2 is needed, and this is not practical with the current infrastructure in the industry. Increasing mixing speed will improve H2 transport from the oil media to the catalyst surface, thus reducing trans formation (Beers 2007). Another means of reducing trans is by using precious metals as a catalyst. Palladium (Pd) and platinum (Pt) are effective and highly selective catalysts. Figure 3.4 shows trans FA formation in soybean oil with platinum as a superior option. By modifying the Pt with nitrogen compounds, it is possible to produce an oil with low trans and low saturate. It must be remembered that due to the low trans formation, the melting property will be different, therefore a higher degree of hydrogenation may be needed to produce a material with desirable melting and textural properties. Currently, the cost of Pt is a significant factor in industrial processing.

3.4.2

Interesterification

Transesterification is a term used to describe reactions in which FA esters react with FFA (acidolysis), alcohols (alcoholysis), or other FA esters (interesterification). In food applications, interesterification often refers to the reaction between different oils or fats (esters), with their fatty acyl groups rearranging among the molecules. Interesterification can be conveniently achieved by an alkali methoxide-catalyzed reaction at mild temperatures (20–100 °C). Microbial lipases are also widely used as biocatalysts in enzymatic interesterification. In contrast to the chemical process, the enzymatic process can be more selective if an enzyme with positional specificity is used, and it is

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Additional trans-isomer formation (%)

50 45 40 Ni (60–140°C) 35

Ni (175–200°C)

30

Pd

25

Pt Pt modified

20 15 10 5 0 0

5

10

15

20

25

Additional saturates (%) Figure 3.4 Selectivity of various catalysts in the hydrogenation of soybean oil to an iodine value of 70. Source: Reproduced from Beers (2007) with the permission of Wiley-VCH Verlag.

usually slower and more sensitive to the reaction conditions. New developments in lipasecatalyzed interesterification have resulted in industrial applications of this process (Hoy and Xu 2001). The reaction can be performed in batch form with the enzyme immobilized, or in continuous form where the enzyme is immobilized in the packed bed. Nevertheless, the high cost of the enzyme restricts its wide adoption, and it may be economically feasible only with very high-value applications. Most interesterification reactions are still performed with a chemical catalyst. One modification of typical interesterification reactions is directed interesterification, in which the reaction is conducted at a relatively low temperature. Under these conditions the more saturated TAG molecules crystallize and equilibrium is continuously reestablished in the liquid phase. A product with desired functional properties can be obtained with appropriate reaction conditions. Randomization is a special form of interesterification in which acyl groups of a single oil or fat rearrange, resulting in a change from the natural distribution, ultimately to a completely random pattern. The chemical and physical properties change as a consequence of this acyl group redistribution. For example, the oxidative stability of soybean and corn oils decreased three to four times by randomization (Fatemi and Hammond 1980; Lau et al. 1982) and the crystallization behavior of natural lard changed from the b to the b′ form (Lutton et al. 1962). Zero trans fats can be made from soybean oil by interesterifying the fully hydrogenated and the unmodified oil, either by a random chemical reaction or an enzymatic reaction. The base-catalyzed reaction is essentially a randomization of fatty acyl groups on the glycerol molecules and it is usually done at 120–150 °C under vacuum and with sodium methoxide as the catalyst (0.2–0.4%) for 0.5–1 hr. However, enzyme-catalyzed reactions are often confined to the sn-1 and sn-3 positions. The enzymatic reaction between the fully saturated hardstock and liquid oil may be problematic due to the melting temperature of the hardstock being much above the enzyme’s optimum temperature.

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Table 3.14 Example of combined hydrogenation, interesterification, and fractionation to produce lowtrans fat from soybean oil. Iodine value Soybean oil (SBO) feedstock Fully hydrogenated SBO (FHSBO) Blending of SBO and FHSBO (60:40) Random interesterification of SBO and FHSBO (60:40) Fractionation of the interesterified oil Soft fraction Hard fraction

Melting point (°C)

Solid fat content (%, at °C) 10

20

30

40

134 1 81

−7 71 63

0 95 44

– 94 42

– 94 39

– 93 35

81

53

38

33

20

11

91 63

24 58

25 60

1 58

0 45

0 32

Source: Adapted from Kellens (2000).

Various methods of laboratory scale, pilot plant processing, and batch reaction of producing trans-free fat were described by Erickson (1995c). List and co-workers (1977) pioneered the development of a zero-trans margarine by interesterifying 80% RBD soybean oil with 20% fully hydrogenated RBD soybean oil. The resulting product has a SFI (solid fat index) comparable to conventional products. In a more recent study, margarines prepared from interesterified soybean oil–soybean trisaturate blends (80:20) were compared with a product made from hydrogenated soybean oil (List et al. 1995). Penetration, yield values, and water/ oil-off data (the tendency of a margarine emulsion to break down physically) were determined. These products tended to crystallize slowly after passing through a rotator and this resulted in a product that was somewhat harder than desirable. However, the addition of 20% soybean oil to the interesterified oil yielded a softer product. Table 3.14 presents a typical example of the combined use of hydrogenation, interesterification, and fractionation to produce low-trans fats with physical properties comparable to partially hydrogenated soybean oil with a high trans content. Soybean oils with elevated levels of saturated FA (by genetic modification) can be randomized to produce margarines with desirable physical properties. Kok and co-workers (1999) randomized a soybean oil containing 23.3% palmitic acid and 20.0% stearic acid to produce a trans-free margarine. The randomized oil had a slip melting point of 34.5 °C (compared with 9.5 °C in the non-randomized oil), and increased melting and crystallization temperatures. A 50:50 blend of the randomized oil and regular soybean oil was used to make margarine, and compared with commercial soft-tub margarine. The maximal penetration force of this blended margarine was about 2.3 times greater, the hardness about 2.6 times greater, and the adhesiveness about 1.5 times greater. There were small but statistically significant differences in the sensory properties of spreadability, graininess, and waxiness between the commercial and blended margarines at 4.5 °C. These results suggest a potential use for the modified high-stearic soybean oil in margarine products. A similar study of zero-trans margarine from soybean oils with modified FA composition was conducted by List and co-workers (2001). A soft margarine was prepared from interesterified soybean oil with elevated stearic acid content (16–21%). The product had penetrations of 75–92 mm, indicating a harder product than that obtained with hydrogenated soybean oil. The margarines showed spreadability values of >6 compared with the 3–5

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found for commercial samples. Mouth-melt data and the oil-off test indicated that the interesterified products were comparable to commercial products. Other vegetable oils, such as palm and cottonseed oils, or fully hydrogenated hardstocks can be blended with genetically modified soybean oils to improve their plastic range (List et al. 1996).

3.4.3

Crystallization and fractionation

Fractionation or winterization is a process in which the more saturated molecular species in the oil are crystallized or solidified during low-temperature treatment and subsequently removed; cold storage stability is thereby increased. When partially hydrogenated soybean oil is fractionated, the more saturated molecular species are removed to leave a clear oil that meets the requirements of a salad oil and a high-stability liquid oil. When interesterifying liquid oil and hardstock for producing trans-free margarines and shortenings, the full randomization reaction will produce some trisaturated molecules that have a high melting point and have to be removed by fractionation to improve melting profiles, textural properties, and mouth feel. Hydrogenation and fractionation are used in soybean oil processing to produce domestic hard butter for cocoa butter substitute and highstability (chemical and physical) liquid oil. The trisaturate species in the interesterified fat can be removed by selecting a proper temperature and accurate control and maintenance of the selected temperature. The efficiency of solid and liquid separation is significantly affected by the method of cooling, which determines the size and form of the crystals. Rapid cooling produces many small crystals with poor filtration properties. Slow cooling leads to stable b and b′ crystals, which can be separated from the liquid by filtration. Fractionation can be done without solvent (i.e. winterization) or with solvent (in acetone at 1:3–5 fat to solvent ratio) for improved filtration and purity of the solid fraction.

3.4.4

Traditional plant breeding and genetic modification

Conventional or traditional breeding of soybeans includes selective breeding by crossing among selected populations and mutagenesis through chemicals or irradiation. Genetic modification implies transfer of a gene from one species to another (transgenic). The drivers for these seed modifications are nutrition, functionality, and agronomics (Gunstone and Pollard 2001). Soybean oil composition is modified to increase its oxidative stability (low linolenate, high oleate), to modify its physical properties (high saturates), and to improve its nutritional properties (low saturates and high linolenate). In addition to changes in oil composition, soybean is also modified to improve its agronomic performance, in areas such as disease resistance, herbicide resistance, and yield. GM soybeans accounted for over 50% of 2007 world soybean production, with the percentage of GM in particular countries being 85 in the US, 95 in Argentina, and 64 in Brazil. Modified soybean oils have been developed and some have been commercialized, as shown in Table 3.15. The high-oleic acid oil (>80%) has a low linolenic acid content (2%) and lower total saturated content (9%). According to Wolf and Knowlton (1999), this type of oil has significantly improved oxidative stability. A mid-oleic acid oil (55%) was developed at North Carolina State University (Wilson 1999), and this oil was predicted to be the soybean variety of the future because of its expected improved shelf-life and flavor quality when used as salad oil. Many more variety of soybeans, such as the various types of reduced-linolenic acid soybeans, have been developed in recent years to replace the partially

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Table 3.15

Soybeans with modified fatty acid composition.

Type

Commodity Low saturates High palmitic High stearic

High palmitic and stearic Low linolenic

Ultra-low linolenic Mid oleic and low linolenic High oleic Stearidonic

Composition, %

Reference

16:0

18:0

18:1

18:2

18:3

11 3 4 25 23 9 11 8 24 22 10 15 10 10 10 9 9 6 9 11

4 1 3 4 5 26 21 30 19 18 5 6 5 6 5 6 4 3 3 4

23 31 28 16 21 18 63 23 9 9 41 32 26 26 28 52 51 86 79 20

54 57 61 44 47 39 1 37 38 41 41 45 56 57 55 31 34 2 3 24

8 9 3 10 4 8 3 3 10 10 2 2 3 1 1 1 1 2 6 10

18:4

20

Liu (1999) Reske et al. (1997) Neff and List (1999) Shen et al. (1997) Neff and List (1999) Knowlton et al. (1999) DiRienzo et al. (2008) Neff and List (1999) Wilson (1999) Fehr et al. (1992) Fehr et al. (1992) Gerde et al. (2007) Gerde et al. (2007) Warner and Fehr (2008) Warner and Fehr (2008) Baumgartner et al. (in press) Liu (1999) Wilson (1999) Harris et al. (2008)

hydrogenated soybean oil for frying. The currently recognized new variety of the future is the mid-oleic and low-linolenic acid soybean. More detailed discussion regarding lowlinolenicacid soybean oils is presented in Section 3.4.5. Oils from soybeans developed to contain changed levels of palmitic and linolenic acid were evaluated for oxidative stability (Shen et al. 1997). Generally, oils with higher saturated FA content or lower polyunsaturated FA content showed higher oxidative stability (Miller and White 1988; White and Miller 1988; Liu and White 1992a, b). Soybean oils with elevated levels of saturated FA may not need hydrogenation, thus reducing processing costs, and they may be used to make the zero-trans margarine and shortenings as discussed earlier. Liu (1999) presented earlier information on soybean oil modification and discussed hurdles in the commercialization of these oil products. Wilkes (2008) also discussed the current status and future direction of modified soybean oil. Minor components in soybean oil are altered along with FA modification. Changes in total tocopherols and their composition in soybean have been reported (Wang and Johnson 2001b; Dolde et al. 1999; Almonor et al. 1998). A multivariate study of the correlation between tocopherol content and FA composition in vegetable oil showed a positive correlation between polyunsaturated FA and tocopherols (Kamal-Eldin and Andersson 1997). According to Abidi and co-workers (1999), genetic modification of canola resulted in changed total tocopherols and greater variation in the concentration of a- and g-tocopherols than in d-tocopherol. When soybean palmitate content was reduced from the normal level in seeds with similar genetic backgrounds, the mean total tocopherol of the reduced palmitate lines was 15% greater than in the normal palmitate lines, and the line with the greatest total tocopherol in each population contained reduced palmitate (Scherder et al. 2006). Even

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though the mean seed yield of the reduced palmitate lines was 5.5% lower than the normal palmitate lines, the significant genetic variation among lines of each type would permit the selection of reduced palmitate lines with good agronomic traits. McCord and co-workers (2004) reported that the tocopherol content of 20 soybean lines with reduced linolenate (1%) was 6.0% less than that in 20 lines with normal linolenate (7%) (all lines with similar genetic background). The significant variation for total tocopherol among the lines of each type should make it possible to develop cultivars with 1% linolenate that have an acceptable content of total tocopherol. The tocopherol content of 20 soybean lines with mid-oleate and 1% linolenate content compared to 20 lines with conventional oleate and 1% linolenate content was not significantly different (1789 vs. 1782 ppm), but the individual tocopherol proportions were changed (Baumgartner et al. 2010). Change of tocopherol with FA modification also affects frying quality. A study by Normand and co-workers (2003) showed that the low-linolenic acid soybean oil has a higher rate of forming total polar compounds than regular soy oil during 72 hr of frying. This was explained, in part, by a lowered level of tocopherols. The composition of tocopherols has been modified by overexpressing the methyl transferase gene to change the tocopherol composition in Arabidopsis thaliana (Shintani and DellaPenna 1998), and a significant tocopherol increase or change in tocopherol composition in soybeans may also be achieved by molecular genetics if there is a strong market need. Phytosterol composition was also markedly affected by genetic modification. Brassicasterol, campesterol, and β-sitosterol levels were consistently lowered in one genotype and increased brassicasterol content was observed in another variety (Abidi et al. 1999). Phytosterol change with FA modification is not as clearly understood as for tocopherols. The study of the genetic modification of FA on the content and composition of minor bioactive components of oil showed that soybeans with elevated palmitic and stearic acids had a lower tocopherol content and that β-sitosterol varied greatly with FA modification (Mounts et al. 1996). The effect of plant growth temperature and FA composition on tocopherols and phytosterols suggested that linolenic acid and total tocopherol have a positive correlation (Dolde et al. 1999), and that total phytosterol increases with elevation in temperature and tocopherols (Vlahakis and Hazebroek 2000). Phospholipid FA composition, altered at the same time as oil modification in soybeans, may have a significant consequence on seed viability and seedling growth. Wang and coworkers (1997) examined the FA composition and stereospecific distribution of fatty acyl groups of three individual PL classes (PC, PE, and PI) in 25 genetically modified soybeans, and found that PL FA composition changed particularly for palmitic, stearic, and linolenic acids. Thermal transitions of the neutral and polar lipids of soybeans with elevated saturated FA were also investigated by Wang and co-workers (2001a, 2001b), who established that the melting temperature of both classes of lipid was increased. Occasional poor germination and field performance of these seeds may be attributed to the modification in their PL composition and consequent changes in the physical properties of their membranes.

3.4.5

Oxidative and sensory properties of low-linolenic acid soybean oil to replace trans frying oil

Since the US FDA set a mandatory labeling requirement for trans FA, effective January 2006, foods have been reformulated to reduce or eliminate trans fat. Oil modification by low-trans hydrogenation or by the interesterification reaction is one approach and plant FA modification is another, especially with the development of low-linolenic acid soybeans in

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the US, where soybean oil is the main food oil. A variety of soybean oils have been obtained by plant breeding and genetic modification, with improved oxidative stability and functional characteristics for use as alternatives to partially hydrogenated fats for frying applications. The low-linolenic (∼3%), ultra-low-linolenic (∼1%), and mid-oleic with low-linolenic acid soybeans have been produced by Pioneer Hi-bred (a division of DuPont), Monsanto, and researchers at Iowa State University (marketed by Asoyia) (Wilkes 2008). These are produced through conventional breeding using marker-assisted selection. Many of the lowlinolenate soybeans are commercialized in the US (up to 1.8 million acres planted since 2006) and the mid-oleate and low-linolenate (53% oleate, 32% linolate, and 1% linolenate) developed at Iowa State University were planted on about 2000 acres in 2009 for commercial oil product evaluation (personal communication from Professor Walter Fehr at Iowa State University). Pioneer is to launch a GM high-oleic soybean oil (80% oleate, 2% linoleate, and 3% linolenate) pending regulatory approval. The mid-oleic with ultra-low-linolenic acid soybean oil was studied for its frying stability and the storage stability of food fried in it. The results showed that this oil is similar to the partially hydrogenated soybean oil after 55 hr of frying, and had much better performance than the regular soybean oil (Warner and Fehr 2008). Therefore, such a modified oil is an alternative to the conventional trans-containing frying oil. Another study on low-linolenate oil’s frying stability shows that the ultra-low-linolenate (1.5%) and low-linolenate (2.6%) oils generated lower percentages of polar materials than did the control (regular oil with 5.3% linolenate), and gave about 30% increase in frying time. A sensory evaluation indicated that the oil with 1.5% linolenate tended to perform better than the oil with 2.6% linolenate oil (Warner and Gupta 2003). It was also shown that a further reduction of linolenate to 0.8% from 2% further improved flavor quality and the oxidative stability of the oil and fried foods. However, it is interesting to note that both linoleic and linolenic acid may play an important role in flavor generation during frying. Warner and Gupta (2005) studied flavors developed in chips fried in a high-oleic soybean oil containing only 2% linolenic acid and 1.3% linoleic acid. Su and co-workers (2003a) also found that during storage at both 21 °C and 32 °C, soybean oil with ultra-low linolenate (1.0%) generally had greater oxidative stability than did oil with 2.2% linolenate. However, the 1.0% linolenate oil initially had significantly greater PV and poorer (lower) sensory scores for overall flavor quality than the 2.2% linolenate oil, although the differences disappeared with storage. In using the interesting Chernoff faces sensory evaluation approach, Su and co-workers (2003b) found that the ultra-low-linolenate oil may not have significant advantages over the low-linolenate oil, and that the addition of TBHQ did not prevent the off-flavor development during 21 °C and 32 °C storage. A lowlinolenate soybean oil was also compared with partially hydrogenated soybean oil (control) in 180 °C pan-frying application for polymer formation (Soheili et al. 2002). The lowlinolenate oil developed 20% polymer twice as quickly as the control. Other quality parameters also indicated that the control was more stable than the low-linolenate oil. The impact of using low-linolenate oil on n-3 FA intake was also studied. The highstearate (19% and 30%), low-linolenate (3%) soybeans developed by traditional breeding and serving as a substitute for the partially hydrogenated soybean oil were evaluated for the impact of this substitution on FA intake in the US (DiRienzo et al. 2008). Several food systems were used and the results showed that the use of such oils could increase stearic acid intake to about 4–5% energy, compared to a baseline intake of stearic acid of 3% energy. Mean intakes of trans FA could decrease from 2.5% to 0.9% energy, and the mean intake of linolenate changed from 0.4% to 0.5% energy for such substitution. An earlier study by the same group (DiRienzo et al. 2006) showed that when low-linolenic acid soybean oil was substituted for hydrogenated soybean oil to reduce the intake of trans FA, there was a 45%

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decrease in intake of trans FA. However, there was no further decrease in intake of linolenic acid because the partially hydrogenated oil is already low in this acid. 3.4.5.1

New commercial soybean oils on the horizon

For frying purposes, an oil with a mid-oleic acid level of 55–60%, a low-linolenic acid level of <3%, or an ultra-low-linolenic acid level of 1% and a low saturated FA of <7%, would be highly desirable as a multi-purpose oil. Monsanto expects to have such a soybean oil after 2011. Similar soybean lines are also being developed at Iowa State University. Screwpressed soybean oils with 1.5% and 2.6% linolenate, and physically refined, together with a commodity-type soybean oil processed in the same manner, have been examined during commercial-like frying of French fries. The American Heart Association recommends 500 mg and 1 g per day of EPA plus DHA for those without coronary heart disease and those with such a condition, respectively. In order to increase EPA and DHA consumption, more feasible and sustainable sources than the deep-sea fish are needed. Stearidonic acid (18:4 n-3) soybeans have been developed through genetic modification by Monsanto to meet this need. This stearidonic acid is produced by inserting Δ6 and Δ15 desaturases into the soybeans. This acid is the first intermediate in the metabolism of linolenate to long-chain n-3 FAs and this desaturation step is rate limiting in humans. Soybean oil containing about 20% stearidonic acid from GM soybeans was developed by Monsanto (Harris et al. 2008), with the purpose of improving the enrichment of tissue EPA (20:5n-3) and/or DHA (22:6n-3). The oil was studied for its effects on blood lipid profile and erythrocyte EPA plus DHA levels when feeding overweight, healthy humans with EPA or with soybean oil containing stearidonic acid. Compared to the control, the mean omega-3 index levels increased by 19.5% in the stearidonic acid group and 25.4% in the EPA group. It seems that this new soybean type may be a viable plant-based ‘marine’ oil for cardioprotective n-3 FAs. Monsanto’s stearidonic acid soybean oil was given GRAS status by the US FDA in 2009. γ-Linolenic acid (GLA) was also introduced into soybeans by the transgenic means of introducing Δ6 desaturase by Agrobacterium-mediated gene transfer (Clemente et al. 2002). For this research, 14 lines of transformants have been identified to contain both GLA and stearidonic acid in the seed-storage lipids. Plant-breeding research has also focused on developing soybeans with decreased palmitate and linolenate (4% for both) (Cherrak et al. 2003). Yield and oil content were not affected by these two acid modifications and they also showed moderately high heritabilities, therefore further crossing with elite lines can be expected to produce commercial lines. In addition, soybean oils with reduced palmitate, stearate, and linolenate were developed to lower total saturated FA and increase stability by traditional line crossing and selection (Streit et al. 2001). Both Monsanto and Pioneer are developing soybeans with high stearate for food use and are expected to release commercial lines in 2–4 years (Wilkes 2008).

3.5 3.5.1

PHYSICAL PROPERTIES OF SOYBEAN OIL Polymorphism

Oils and fats go through a series of increasingly organized crystal phases on cooling. This multiple form of crystallization (polymorphism) is an important characteristic of fats and oils because it greatly influences the textural and functional properties of fats and fat-based products.

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The three commonly observed fat crystal forms are the α, β′, and β forms. The β′ form, with small and needle-like crystals, creates smooth and fine-grained structures and is the most desired form in shortening and margarine applications. Oil composition plays an important role in crystal formation. Unmodified soybean oil has a tendency to form β-crystals, but the hydrogenated soybean oil can be crystallized in the β′ form. Controlled crystallization (under defined conditions of temperature, time, and mixing) and tempering is used to manipulate or stabilize the crystal forms for achieving the desired functional properties.

3.5.2

Density

Most of the information concerning the physical properties of soybean and other vegetable oils was reported many years ago. However, there are recent developments in establishing mathematical models to predict changes in physical properties with FA composition and temperature. For vegetable oils, it has been shown that density decreases linearly with increase in temperature (Formo 1979): r = b + mT where r is the density, T is the temperature, and b and m are constants. These constants are different for different oils. A widely used method for density prediction of vegetable oils was developed by Lund and discussed by Halvorsen and co-workers (1993). The Lund relationship is: sg (15 °C) = 0.8475 + 0.00030 SV + 0.00014 IV where sg is the specific gravity of vegetable oil at 15 °C, SV is the saponification value, and IV is the iodine value of the oil. This equation can be used for a wide variety of oils. For further details, readers are directed to the paper by Halvorsen and co-workers (1993). A generalized method of density estimation, which was also developed by Rodenbush and coworkers (1999), was designed to predict oil viscosity, thereby relating two key physical properties.

3.5.3

Viscosity

The effect of temperature on the viscosity of various vegetable oils and FA was investigated by Noureddini and co-workers (1992). The relationship was expressed as ln m = A + B/(T + C) in which μ is viscosity in centipoises, A, B, and C are constants and T is temperature in Kelvin. For each oil and FA, there is a set of constants that can be used to predict how temperature affects the viscosity of individual oils. The viscosity of fatty systems was also predicted by Rabelo and co-workers (2000) using the same temperature–viscosity relationship. The set of A, B, and C values for each fatty compound class was then correlated with the number of carbon atoms and double bonds, and rather complicated relationships were established.

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Wang and Briggs (2002) studied the viscosity of soybean oils with modified FA composition. The viscosity was expressed as m = A e(Ea/RT) in which R is the universal gas constant, T is temperature in Kelvin and Ea is the energy of activation. The concept of effective carbon number was used to describe acyl chain length and degree of unsaturation, and was correlated with viscosity and Ea. Linear relationships were established, which indicate that the more the saturation or the longer the fatty acyl chains, the more viscous the oil and the faster the viscosity will change with temperature. Geller and Goodrum (2000) reported that the viscosity of pure and saturated TAG of 6:0 to 18:0 correlated with the carbon number in a second-order polynomial fashion.

3.5.4

Refractive index

The refractive index (RI) is a parameter that relates to molecular weight, FA chain length, degree of unsaturation, and degree of conjugation. A mathematical relationship between RI and IV has been described by Perkins (1995b) as nD25 = 1.45765 + 0.0001164 IV The reverse relationship can be used to calculate the iodine value of crude soybean oil when the RI is known. RI was shown to increase by 0.000385 for each degree rise in temperature.

3.5.5

Specific heat

The specific heat (Cp, in J/g K) of vegetable oil is influenced by temperature (Formo 1979), as described in the equation Cp = 1.9330 + 0.0026 T The liquid specific heat capacity for FA, TAG, and vegetable oils was estimated based on their FA composition (Morad et al. 2000). A Rowlinson–Bondi equation was used to estimate the specific heat (Cp) of pure FA. The liquid specific heat capacities of oils were estimated by using mixture properties corresponding to the FA composition and a correction factor, which accounts for the TAG form. The Rowlinson–Bondi equation used is as follows: (Cp − Cp0)/R = 1.45 + 0.45 (1 − Tr)−1 + 0.25 w[17.11 + 25.2 (1 − Tr)1/3 Tr−1+ 1.742 (1 − Tr)−1] where Cp is the liquid specific heat capacity, Cp0 is the ideal gas specific heat capacity, R is the universal gas constant, Tr is the reduced temperature, and w is the acentric factor. Cp0 is calculated using the method of Rihani and Doraiswamy (1965): Cp0 = Σ a + T Σ b + T2 Σ c + T3 Σ d

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The constants a, b, c, and d for various chemical groups were used to calculate the ideal gas capacity of pure FA. The reduced temperature is calculated as Tr = T/Tc (critical temperature). For a vegetable oil with xi being the molar fraction of an FA that has Cp0i, Cp0 (mix) = Σ xi Cp0i A correction factor was used to correct the difference between calculated and experimental values, as derived from Morad’s study. For MW > 850, Correction factor (F) = −0.2836 – 0.0005 (MW – 850) Cp (estimated for oil) = Cp (calculated for mixed fatty acid) + F The accuracy of Morad’s estimation method was determined to be ± 5%. This model was used by Wang and Briggs (2002) to estimate the Cp of soybean oils with a modified FA composition at various temperatures. All oils had the same slope of 0.0024, but the constant ranged from 1.7992 to 1.8583, compared with a slope of 0.0026 and a constant of 1.9330 from Formo’s equation.

3.5.6

Melting point

The melting points of TAG are related to the FA present. For an FA, its melting point depends on the chain length and the number and position of double bonds. It increases with increasing chain length and decreases with increasing cis unsaturation. The trans form has a significantly higher melting point than its cis isomer. Polymorphism is an important factor affecting melting point. The melting points of FA and their TAG of soybean oil are presented in Table 3.16.

3.5.7

Heat of combustion

A general equation linking the heat of combustion of vegetable oils to IV and SV (i.e., average FA composition) has been developed by Bertram (Perkins 1995b): −DHc (cal/g) = 11 380 − IV − 9.158 SV Therefore, the higher the degree of saturation and the longer the fatty acyl groups, the higher the energy content of the oil.

3.5.8

Smoke, flash, and fire points

These parameters are related to the FFA content of oils because they have a higher vapor pressure than the TAG. The smoke point is the temperature at which smoke is first seen. The flash point is the temperature at which the volatiles are produced in amounts that ignite but do not support a flame. The fire point is the temperature at which the volatiles are produced in a quantity that will support a flame. These temperatures are lower for oils with a higher FFA content or with short-chain acids.

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Soybean Oil Table 3.16

Melting point of fatty acids and triacylglycerols of soybean oil.

Fatty acid Name

Melting point, °C

Palmitic Stearic

62.9 69.6

Oleic

16.3

Elaidic Linoleic Linolenic

91

Triacylglycerol Composition*

43.7 −6.5 −12.8

PPP SSS SPP PSP SPS OOO POP SOS POO SOO EEE LLL LnLnLn

Melting Point, °C b Form

b′ Form

65.5 73.0 62.5 68.0 68.0 5.5 35.2 41.6 19.0 23.5 42.0 −13.1 −24.2

56.0 65.0 59.5 65.0 64.0 −12.0 30.4 37.6 – – 37.0 – –

Source: Adapted from Sipos and Szuhaj (1996a). Note: * These symbols represent the acyl groups of the TAG molecule: P = palmitic, S = stearic, O = oleic, L = linoleic, Ln = linolenic, E = elaidic acid.

3.5.9

Solubility

Soybean oil is miscible with many non-polar organic solvents. The solubility characteristics of vegetable oils in various solvents can be estimated from their dielectric constants or solubility parameters (Sipos and Szuhaj 1996b). Anhydrous or aqueous ethanol is not a good solvent for soybean oil at an ambient temperature. Solubility increases with temperature until the critical solution temperature is reached, at which point the oil and ethanol become miscible. The solubility of oxygen in soybean oil contributes to the oxidative stability of the oil. It varies from 1.3 to 3.2 mL/100 mL in refined and crude oils. The solubility of water in soybean oil is about 0.071% at −1 °C and 0.141% at 32 °C (Perkins 1995b).

3.5.10 Plasticity and spreadability The most important functionality of a solidified oil and fat is its plasticity, consistency, or spreadability. A shortening or margarine product may appear to be in a homogeneous solid state, but it consists of a discrete solid (crystal particles) dispersed in a liquid (oil) phase. The essential conditions for plasticity are a proper proportion of the solid and liquid phase, and the solid particles have to be very fine so that the mass is held together by internal cohesive forces. SFI and SFC measurements may be used to describe plasticity and spreadability.

3.5.11 Electrical resistivity Certain industrial applications of soybean oil, such as printing ink, require high electrical resistivity to maintain the sharpness of the image. There is limited information on the electrical properties of oil, and most deal with its dielectric properties. Resistivity is the

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Table 3.17 Representative values for selected physical properties of soybean oil. Property

Value

Specific gravity, 25 °C Refractive index, nD25 Specific refraction, rD20 Viscosity, centipoises at 25 °C Solidification point, °C Specific heat, cal/g at 19.7 °C Heat of combustion, cal/g Smoke point, °C Flash point, °C Fire point, °C

0.9175* 1.4728** 0.3054 50.09* −10 to −16 0.458 9478§ 234 328 363

Source: Adapted from Pryde (1980b). Notes: * IV = 132.6. ** IV = 130.2. § IV = 131.6.

resistance to current passing through the material and factors such as temperature, applied voltage, and charging time will affect the value. Polar minor components, including FFA, PL, monoacylglycerols, tocopherols, phytosterols, β-carotene, peroxides, and water, all decrease the resistivity of purified soybean oil (Tekin and Hammond 1998) and of soybean oil methyl esters (Tekin and Hammond 2000). Selected physical properties of soybean oil are summarized in Table 3.17.

3.6

OXIDATION EVALUATION OF SOYBEAN OIL

Normal soybean oil is a polyunsaturated or linoleic type of oil that is highly susceptible to lipid autoxidation. The rate of lipid oxidation depends primarily on the FA composition, and only secondarily on the regiospecific distribution of the fatty acyl groups, as described earlier. The mechanism of lipid oxidation and lipid hydroperoxide breakdown is discussed thoroughly by Frankel (2005). The oxidative instability limits soybean oil in certain applications. Nevertheless, hydrogenated and other means of composition modification (along with its availability) have made soybean oil the second most widely used of all vegetable oils. The analytical methods frequently used to quantify the oxidation of soybean oil include sensory evaluation, which provides information most closely associated with the quality of food lipids. For example, the ‘fishy’ and ‘grassy’ taste produced in linolenic acid-containing oils such as soybean oil occurs at very low levels of oxidation that may only be detected by sensory analyses. The limitations of the sensory method are its poor reproducibility and its high cost for panelists and facilities, so the recommended approach is to use more reproducible chemical or instrumental methods to complement or support the sensory analyses (Frankel 2005). Commonly used methods are peroxide value (PV) and its change during oil storage at mildly elevated temperatures (<60 °C). PV is obtained by standard iodometric titration or the more sensitive ferric thiocyanate reaction and spectrophotometric quantification. The rate by which PV increases with time is used as a measure of oxidative stability and is determined as the slope of the natural logarithm of PV vs. time.

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The temperature at which the accelerated oxidation is carried out is important, because the mechanisms of oxidation and peroxide decomposition are different at different temperatures. To realistically predict the oxidative stability of food lipids, the test conditions should be as close as possible to those under which the lipid is stored. The automated systems for oxidative stability determination, such as the Rancimat or OSI (oxidative stability index) method, are criticized as being unreliable because of the high temperature (about 100 °C) that is typically applied (Frankel 2005), but are nevertheless widely employed. Others have reported a good correlation between OSI hours and sensory evaluation (Coppin and Pike 2001), so OSI appears to be an acceptable accelerated method for measuring the oxidative stability of light-exposed soybean oil that varies in metal catalyst content. Conjugated diene peroxides produced from the linoleic acid in soybean oil can be determined quantitatively by their strong absorption at 234 nm. This is a sensitive method, but it can only apply to the undegraded peroxides. For secondary oxidation product quantification, carbonyl compounds can be measured by the Anisidine Value (Frankel 2005), by Thiobarbituric Acid Reactive Substances (TBARS) that indicate levels of malonaldehyde, which is a decomposition product from internal lipid hydroperoxides of FA with more than three double bonds, and by GC that quantifies the volatile compounds from the lipid hydroperoxide degradation. Different sample collection methods can be used for GC sample preparation, such as static and dynamic headspace or direct injection (Frankel 1985). Lee and co-workers (1995) developed a dynamic headspace procedure for isolating and analyzing the volatiles from oxidized soybean oil, and equations were derived from theoretical considerations that allowed the actual concentration of each flavor component to be calculated.

3.7

NUTRITIONAL PROPERTIES OF SOYBEAN OIL

Soybean oil is the dominant edible oil in the US. According to the 2010 Soystats, 87% of all soybean oil produced in the US in 2009 was used in foods and 13% was used in non-food applications. Out of the total oil used in food, 28% was used for cooking and frying, 6% for spreads, and 66% as cooking and salad oil. Ten years earlier these values were 97% of total for food use, and out of the total, 37%, 13%, and 49% were used in shortening, margarine, and cooking and salad oil, respectively. Based on the dietary assessment data (collected in 2005 by the Food Surveys Research Group), soybean oil accounts for about 12% of calories in the average American diet. Therefore, the contribution of soybean oil to human health is important. Commodity soybean oil is composed of 61% polyunsaturated FA, 25% monounsaturated FA, and 15% saturated FA. The essential FA linoleic (18:2 n-6) and α-linolenic (18:3 n-3) acids account for 89% and 11% of the total essential FA from this source. The n-6 acid content in soybean oil is slightly lower than that in corn and sunflower oils, but it is more than double that in canola oil. Soybean and canola are the only two common plant oils that have a considerable amount of n-3 linolenic acid. Edible oils and fats are in general well absorbed by humans. The absorption efficiency is affected by the melting point of the fats, the positional distribution of the fatty acyl groups on the glycerol, and the presence of calcium and magnesium ions. In general, highly saturated and long-chain high-melting fats are less absorbed than the lower-melting fats. FA on the sn-2 position is typically better absorbed, and a high concentration of divalent ions forms insoluble soaps with saturated FA, reducing their absorption. The current US dietary guidelines recommend that diets contain less than 30% calories from fat, comprising less than 10% from saturated fat, 10–15% from monounsaturated acid,

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and 10% from polyunsaturated acids. The primary concerns with FA consumption relate to two chronic diseases: coronary heart disease (CHD) and cancer. Research has shown that high levels of dietary saturated FA are related to increased CHD and that dietary modification can lower plasma cholesterol. Consequent changes in cholesterol level can be predicted by the relationship (Hegsted et al. 1993): D cholesterol = 2.10 (D saturates) − 1.16 (Δ⋅ polyunsaturates) + 0.06 (D dietary cholesterol) The physiological effects of vegetable oils are based on their FA composition. Soybean oil is a linoleic-type oil, and the high n-6 to n-3 ratio causes concerns about inflammation and its associated chronic diseases, such as cardiovascular disease and type II diabetes. However, the direct association is still not clearly shown. It is known that bioconversion of the absorbed linolenic acid to EPA and more particularly DHA in humans is very low, and this may contribute to the inconsistency of the clinical trial results versus experiments conducted in isolated and much simpler systems. It is believed that the amount of total fat consumed, rather than the specific type of fat, is positively associated with cancer risk (Dupont et al. 1990). However, animal studies suggested that linoleic acid promotes carcinogenesis under special circumstances (Sundram et al. 1989; Dupont et al. 1990), and that linolenic acid has a potential anticarcinogenic effect (Fritsche and Johnson 1988). The amount of fat and its unsaturation significantly influence the normal immune response and the expression of inflammatory diseases (Connor 2000). Some of the recent studies on the effect of saturated fat, mono- and polyunsaturated oils, and carbohydrate on chronic disease or risk factors have shown that there are significant interactions among the various macronutrients. Carbohydrate may influence how fats and oils are metabolized and exert their negative physiological functions. A pooled analysis of 11 major cohort studies shows that for a total of 344 696 individuals, when 5% of saturated fat energy was replaced by polyunsaturated oil, there was about a 12% reduction in CHD risk; when the same amount of saturated fat was replaced by carbohydrate and monounsaturated oil, the CHD risk increased by about 7% and 19%, respectively (Jakobsen et al. 2009). In the same study, when the dietary carbohydrate was replaced by monounsaturated oil, there was about a 10% increase in CHD risk. However, when the carbohydrate was replaced by saturated fat and polyunsaturated oil, there was about an 8% and 20% reduction in CHD risk, respectively. Another meta-analysis of 60 randomized controlled trials (Mensink et al. 2003) shows that when poly- and monounsaturated oil and saturated fat were used to replace carbohydrate at up to a 5% calorie level, there were significant and moderate reductions and a significant increase in LDL cholesterol, respectively. At the same time, there were the least, intermediate, and the most increases in HDL cholesterol, respectively for these three substitutions. Therefore, for the most important total cholesterol to HDL cholesterol ratio, both poly- and monounsaturated oil reduced the ratio, and the saturated fat only slightly increased the ratio. These results, as summarized in Table 3.18, indicate that saturated fats may not be as bad as was previously believed, and that carbohydrate may play a much more critical role in FA metabolism and cardiovascular health than has been recognized. The deleterious effect of trans FA on health has been clearly demonstrated. The physical property of the trans FAs (i.e., straighter hydrocarbon chain and higher melting point compared with their cis counterparts) may contribute to their biological effect. The absorption of trans and cis FAs is similar (Emken 1984), but trans isomers are metabolized differently from the cis isomers, in that they are more rapidly oxidized (Emken et al. 1989). Study of the cholesterol-raising effect of trans FAs has shown that they increased total cholesterol

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Effect on health of replacing diet with other macronutrients at 5% calorie level. CHD risk

Jakobsen et al. (2009)

Mensink et al. (2003)

Saturated fat replaced by: Polyunsaturate Carbohydrate Monounsaturate

12% ↓ 7% ↑ 19% ↑

Carbohydrate replaced by: Polyunsaturate Monounsaturate Saturate

20% ↓ 10% ↑ 8% ↓

Carbohydrate replaced by: Polyunsaturate Monounsaturate Saturate

LDL

HDL

Total:HDL ratio

↓↓ ↓ ↑↑

↑ ↑↑ ↑↑↑

↓ ↓ slight increase

and LDL cholesterol and lowered HDL cholesterol compared with the cis isomers (Judd et al. 1994). Soybean oil composition modification and developing new hydrogenation catalysts, as discussed in earlier sections, are examples of efforts devoted to replacing trans fats with more healthful and functional food oils and fats.

3.8

FOOD USES OF SOYBEAN OIL

According to the 2009 Soya and Oilseed Bluebook, 83% of all soybean oil produced in the US in 2006/07 was used in foods and 17% was used in non-food applications. Out of the total oil used in food, 35% was used for shortening production, 6% for margarine, and 58% as cooking and salad oil. Ten years earlier these values were 97% of the total for food use, and, out of the total, 37%, 13%, and 49% were used in shortening, margarine, and cooking and salad oil, respectively. Warner (2008) also reported similar soybean oil utilization data for 2005; that is, soybean oil used as shortening, margarine, and cooking/salad oil at 45%, 5%, and 48%, respectively. The general decrease in use in margarine and increase in use in cooking and salad oil may reflect the desire to reduce the intake of trans acids as well as the use of reduced fat spreads.

3.8.1

Cooking and salad oils

Oil can be used for cooking either in its natural state or after processing, depending on custom and nutritional beliefs. In most parts of the world, cooking oil is processed or refined to a bland taste. In addition to its common household uses, the use of cooking oil in deep-fat frying is very important on both a domestic and a commercial scale. Salad oil is a refined or sometimes fractionated liquid vegetable oil, remaining liquid at 4.4 °C. An important distinction between salad and cooking oils is the difference in their oxidative and thermal stability (Krishnamurthy and Witte 1996). Cooking oil needs to be more stable than salad oil at higher temperatures, such as deep-fat frying. Fully refined soybean oil can be directly used as salad oil, whereas other oils, such as sunflower and corn oils, have to be dewaxed

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before they can meet the criteria of a salad oil. Because soybean oil contains a relatively high amount of the polyunsaturated and unstable linolenic acid, it is usually partially hydrogenated to produce salad or cooking oils. However, soybean oil is also used without hydrogenation in the preparation of salad dressings. Synthetic antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxy toluene (BHT), propyl gallate (PG), ascorbyl palmitate, and tertiary-butyl hydroquinone (TBHQ), have been used in cooking oils. Natural antioxidants derived from sage, rosemary, and green tea are increasingly used to meet the consumer’s preference for natural food ingredients (Chen et al. 1992). New nutrition-oriented salad and cooking oils are being developed. LoSatSoy is a lowsaturated acid oil developed at Iowa State University and marketed commercially as a salad and cooking oil. It has half of the saturated FA compared with commercial soybean oil; therefore, it is believed to have a nutritional benefit. Low-linolenic acid soybean oil has improved oxidative stability in salad and cooking oil applications. Stearidonic acid soybean oil was developed as a ‘land marine’ oil that can be used as salad oil. Many types of soybean oils have been developed recently as frying oil substitutes to replace the partially hydrogenated soybean oil, and these have been discussed in Section 3.4.4 on oil modification. These stable oils can also be used as salad and cooking oils. A unique vegetable oil, diacylglycerol (DAG) oil, developed and successfully marketed in Japan by Kao Corp, is produced from soybean oil by an Archer Daniels Midland Co. (ADM)–Kao LLC joint venture. This oil is metabolized differently from other oils in that it is not stored as body fat but immediately burned as energy (Soni et al. 2001). It lowered the magnitude of the increase in serum and chylomicron TAG levels as compared with TAG in a single-administration study in humans, and is considered to reduce postprandial hypertriglyceridemia (Matsuo and Tokimitsu 2001). DAG has a similar caloric value and absorption rate to TAG, but resynthesis to TAG in the small intestine epithelial cells is different when DAG or TAG is ingested. DAG is considered effective in preventing obesity and, possibly, in moderating lifestyle-related diseases. Serum profiles and anthropometric parameters (body weight, body mass index, waist circumference and thickness) were obviously improved in free-living subjects by consuming DAG as cooking oil (Yasukawa and Yasunaga 2001). The effect of dietary DAG oil on postprandial lipid metabolism, as evaluated by Matsuo (2008a), showed that substituting DAG oil for TAG oil can be effective in terms of managing excess adiposity in free-living subjects, because there was a body-weight reduction of about 0.90 kg (1.2%) compared with that of the TAG group after a 12-month diet substitution. DAG has received GRAS status from the US FDA, and it is expected that its future application in various food products will improve the health of the general public. More recent reviews discussing scientific and practical information regarding the nutritional properties, clinical efficacy, safety, manufacturing, and application technologies of DAG oil are presented by Yasukawa and Katsurgi (2008) and Matsuo (2008b). The current issue of a processing contaminant is discussed in Section 3.3.5.

3.8.2

Margarine and shortening

Margarine was first produced in 1869 by a French chemist to meet the butter shortage during the Industrial Revolution. The traditional form of the product is stick margarine. Other forms, including spreadable, polyunsaturated, and low-fat margarines, have been developed to satisfy the demands of convenience and nutrition. A significant recent trend is away from margarine (80% fat, as defined by the FDA’s Standard of Identity) to spreads with less fat

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(75% to less than 5%). This trend has accelerated to a point where there are now very few full-fat margarine products available in the US (Chrysam 1996). The most important functional properties of margarines and spreads are spreadability, oiliness, and melting behavior. These properties relate to fat level and the type and stability of the emulsion. Spreadability can be predicted by SFI and penetration measurement. Oiloff refers to the phenomenon when fat crystals no longer form a stable network to trap the liquid oil. Consistency and emulsion stability depend on the amount and type of crystallized fat. During rapid cooling, the most unstable α form; crystals form, but these quickly transform to the β′ form, which is relatively stable and consists of a very fine crystal network capable of immobilizing a large quantity of oil. These β′ crystals may also transform into the most stable β form, which has a coarse and sandy texture and from which liquid (oil) may be expelled. Quick melting at body temperature and the consequent cooling sensation are the desired qualities and they are related to the melting profile of the fat as well as emulsion formation (Chrysam 1996). Most table spreads in the US are formulated with soybean oil. Palm oil, lauric fat, and even partially hydrogenated marine oils frequently accompany sunflower or other unsaturated oil in Europe, though there is now very little use of hydrogenated fish oil. Blending of unmodified oils with oils hydrogenated to various degrees allows the production of margarines with the desirable texture. The greater the number of base stocks available, the greater is the flexibility to produce a wide range of products and the higher the tolerance to processing conditions. A study of procedures for designing suitable margarine from various stocks was conducted by Cho and co-workers (1993). Other ingredients used in margarines are dairy products, emulsifiers, preservatives, flavors, vitamins, and colors. The processing of margarine includes emulsification, chilling, working, resting, and packaging (Chrysam 1996). The ingredients are emulsified before being fed into a swept-surface heat exchanger. The mass emerging from the cooling tubes is a partially solidified mass and it is further crystallized in the working unit. The texture of the product is further modified in the resting tube before the margarine is packaged. Shortening contains 100% fat of vegetable or animal source and is used in frying, cooking, baking, and other confectionery items. It can be in plastic and semi-solid or pourable fluid form, or in encapsulated powder, pellet, or flake form. It is produced by formulating a blend, solidifying and plasticizing this, and finally packaging and tempering. The β′ form crystals are preferred for both margarine and shortening products. A large number of minute air bubbles incorporated in the shortening improve the leavening of baked foods. A more in-depth discussion of the science and technology of shortening has been presented by Metzroth (1996).

3.8.3

Mayonnaise and salad dressing

The official definition (FDA Standard of Identity) describes mayonnaise as a semi-solid food prepared from vegetable oil (no less than 65%), egg yolk, and vinegar. Most mayonnaise in the US contains 75–82% oil and is usually soybean oil. Other salad oils (including partially hydrogenated soybean oil) that have undergone winterization can also be used in mayonnaise. The production of mayonnaise is partly an art due to the difficulty of producing the o/w emulsion, in which the dispersed phase is seven times greater than the continuous phase. Egg solids and processing conditions play critical roles in mayonnaise quality. Salad dressings were developed as an alternative to mayonnaise. The Standard of Identity requires that salad dressing contain not less than 30% vegetable oil, vinegar, and not less

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than 4% egg yolk, and that it is thickened by starch. The oils used in salad dressing are selected using the same criteria as for mayonnaise. The quality of mayonnaise and salad dressing is determined by the physical and oxidative stability of its lipid components. Phase separation may be caused by emulsion breakdown due to mechanical shock, agitation, or extreme temperatures. Oxidation of vegetable oil and egg lipid is another form of degradation of mayonnaise or salad dressing. Because the quality of the oil plays a major role in the flavor stability of these products, only the bestquality oil should be used in product formulation. Another class of dressing is pourable as opposed to spoonable products (mayonnaise and Kraft’s Miracle Whip). The standard for this type of product is undefined, except for French dressing (Krishnamurthy and Witte 1996). Pourable dressing can be in two different finished forms, one phase or two phases, depending on whether the product is homogenized. The oil used in these products is predominantly soybean oil in the US. Canada and Europe may use different oils for such products, depending on the availability of vegetable oil in that specific region.

REFERENCES Abidi, S.L., List, G.R. and Rennick, K.A. (1999) Effect of genetic modification on the distribution of minor constituents in canola oil, Journal of the American Oil Chemists’ Society, 76, 463–467. Almonor, G.O., Fenner, G.P. and Wilson, R.F. (1998) Temperature effect on tocopherol composition in soybeans with genetically improved quality, Journal of the American Oil Chemists’ Society, 75, 591– 596. Auriou, N. (2003) Water-dispersible encapsulated sterols/Preparation of a water-dispersible powder comprises phytosterolsm, US Patent Application Publication US 2003165572 A1 20030904. Ballmer-Weber, B.K. and Vieths, S. (2008) Soy allergy in perspective, Current Opinion in Allergy and Clinical Immunology, 8, 270–275. Basu, H.N. and Norris, M.E. (1996) Process for production of esters for use as a diesel fuel substitute using a non-alkaline catalyst, US Patent 5,525,126. Baumgartner, R.M., Fehr, W.R., Wang, T. and Wang. G. (2010) Tocopherol content of soybean lines with mid-oleate and 1%-linolenate, Crop Science, 50, 770–774. Beers, A.E.W. (2007) Low trans hydrogenation of edible oils, Lipid Technology, 19, 56–58. Bogani, P., Minunni, M., Spiriti, M.M. et al. (2009) Transgenes monitoring in an industrial soybean processing chain by DNA-based conventional approaches and biosensors, Food Chemistry, 113, 658–664. Brekke, O.L. (1980) Oil degumming and soybean lecithin, in Handbook of Soy Oil Processing and Utilization (eds D.R. Erickson, E.H. Pryde, O.L.Brekke, T.L. Mounts and R.A. Falb), AOCS Press, Champaign, IL, pp. 71–88. Carmelo, P. and Francesco, B. (2008) In vivo spectrophotometric evaluation of skin barrier recovery after topical application of soybean phytosterols, Journal of Cosmetic Science, 59, 217–224. Chang, C.J., Chang, Y., Lee, H., Lin, J. and Yang, P. (2000) Supercritical carbon dioxide extraction of highvalue substances from soybean oil deodorizer distillate, Industrial and Engineering Chemistry Research, 39, 4521–4525. Chen, Q., Shi, H. and Ho, C. (1992) Effect of rosemary extract and major constituents on lipid oxidation and soybean lipoxygenase activity, Journal of the American Oil Chemists’ Society, 69, 999–1002. Cherrak, C.M., Pantalone, V.R., Meyer, E.J. et al. (2003) Low-palmitic, low-linolenic soybean development, Journal of the American Oil Chemists’ Society, 80, 539–543. Cho, F., deMan, J.M. and Allen, O.B. (1993) Application of simplex-centroid design for the formulation of partially interesterified canola/palm blends, Journal of Food Lipids, 1, 25–52. Chow, C.K. and Draper, H.H. (1974) Oxidative stability and antioxidant activity of the tocopherols in corn and soybean oils, International Journal of Vitamin and Nutrition Research, 44, 396–403. Chrysam, M.M. (1996) Margarines and spreads, in Bailey’s Industrial Oil and Fat Products, Vol 3: Edible Oil and Fat Products: Products and Application Technology, 5th edn (ed Y.H. Hui), John Wiley & Sons, Inc., New York, pp. 65–114.

Gunstone_c03.indd 98

1/21/2011 6:07:27 PM

Soybean Oil

99

Clark, J.P. and Frandsen, S.S. (1998) Phytochemicals from vegetable oil deodorizer distillate, in Proceedings of the World Conference on Oilseed Edible Oils Processing (eds S.S. Koseoglu, K.C. Rhee and R.F. Wilson) AOCS Press, Champaign, IL., pp. 135–138. Clemente, T., Xing, A., Ye, X. et al. (2002) Production of gamma linolenic acid in seeds of transgenic soybean, in Plant Biotechnology 2002 and Beyond, Proceedings of the IAPTC&B Congress (ed I. K.Vasil), Orlando, FL, June 23–28, pp. 421–424. Connor, W.E. (2000) Importance of n-3 fatty acids in health and disease, American Journal of Clinical Nutrition, 71, 171S–175S. Coppin, E.A. and Pike, O.A. (2001) Oil stability index correlated with sensory determination of oxidative stability in light-exposed soybean oil, Journal of the American Oil Chemists’ Society, 78, 13–18. Daniels, R.S. (1989) Fertilizer process, Canadian Patent 1,256,449. De Greyt, W. and Kellens, M. (2000) Refining practices, in Edible Oil Processing (eds W. Hamm and R.J. Hamilton), Sheffield Academic Press, Sheffield, pp. 79–128. Dijkstra, A.J. (1992) Degumming, refining, washing and drying fats and oils, in Proceedings of the World Conference on Oilseed Technology and Utilization (ed. T.A. Applewhite), AOCS Press, Champaign, IL, pp. 138–151. DiRienzo, M.A., Astwood, J.D., Petersen, B.J. and Smith, K.M. (2008) Effect of substitution of high stearic low linolenic acid soybean oil for hydrogenated soybean oil on fatty acid intake, Lipids, 43, 451–456. DiRienzo, M.A., Lemke, S.L., Petersen, B.J. and Smith, K.M. (2006) Effect of substitution of low linolenic acid soybean oil for hydrogenated soybean oil on fatty acid intake, Lipids, 41, 149–157. Dolde, D., Vlahakis, C. and Hazebroek, J. (1999) Tocopherols in breeding lines and effects of planting location, fatty acid composition, and temperature during development, Journal of the American Oil Chemists’ Society, 76, 349–355. Dupont, J., White, P.J., Carpenter, M.P. et al. (1990) Food uses and health effects of corn oils, Journal of the American College of Nutrition, 9, 438–470. Emken, E.A. (1984) Nutrition and biochemistry of trans and positional fatty acid isomers in hydrogenated oils, Annual Review of Nutrition, 4, 339–376. Emken, E.A., Adlof, R.O., Rohwedder, W.K. and Gulley, R.M. (1989) Incorporation of trans-8- and cis-8octadecenoic acid isomers in human plasma and lipoprotein lipids, Lipids, 24, 61–69. Erickson, D.R. (1995a) Neutralization, in Practical Handbook of Soybean Processing and Utilization (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 184–202. Erickson, D.R. (1995b) Bleaching/adsorption treatment, in Practical Handbook of Soybean Processing and Utilization (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 203–217. Erickson, M.D. (1995c) Interesterification, in Practical Handbook of Soybean Processing and Utilization (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 277–296. Erickson, D.R. and Erickson, M.D. (1995) Hydrogenation and base stock formulation procedures, in Practical Handbook of Soybean Processing and Utilization (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 218–238. Evans, J.C., Kodali, D.R. and Addis, P.B. (2002) Optimal tocopherol concentrations to inhibit soybean oil oxidation, Journal of the American Oil Chemists’ Society, 79, 47–51. Fatemi, S.H. and Hammond, E.G. (1980) Analysis of oleate, linoleate, and linolenate hydroperoxides in oxidized ester mixtures, Lipids, 15, 379–385. Fehr, W.R., Welke, G.A., Hammond, E.G., Duvick, D.N. and Cianzio, S.R. (1992) Inheritance of reduced linolenic acid content in soybean genotypes A16 and A17, Crop Science, 32, 903–906. Ferrari, R.A., Schulte, E., Esteves, W., Bruhl, L. and Mukherjee, K.D. (1996) Minor constituents of vegetable oils during industrial processing, Journal of the American Oil Chemists’ Society, 73, 587–592. Formo, M.W. (1979) Physical properties of fats and fatty acids, in Bailey’s Industrial Oil and Fat Products, vol. 1 (ed. D. Swern), 4th edn, John Wiley & Sons, Inc., New York, pp. 177–232. Frankel, E.N. (1985) Chemistry of autoxidation: Mechanism, products and flavor significance, in Flavor Chemistry of Fats and Oils (eds D.B. Min and T.H. Smouse), AOCS Press, Champaign, IL, pp. 1–37. Frankel, E.N. (2005) Lipid Oxidation, 2nd edn, Oily Press, Bridgwater. Frische, K.L. and Johnson, P.V. (1988) Reduced growth and matastasis of a transplantable syngeneic mammary tumor (410.4) by dietary alpha-linolenic acid, Journal of the American Oil Chemists’ Society, 65, 509. Geller, D.P. and Goodrum, J.W. (2000) Rheology of vegetable analogs and triglycerides, Journal of the American Oil Chemists’ Society, 77, 111–114. Gerde, J., Hardy, C., Fehr, W. and White, P.J. (2007) Frying performance of no-trans, low-linolenic acid soybean oils, Journal of the American Oil Chemists’ Society, 84, 557–563.

Gunstone_c03.indd 99

1/21/2011 6:07:28 PM

100

Vegetable Oils in Food Technology

Golbitz, P. (2000) Soya & Oilseed Blue Book, Soyatech, Bar Harbor, ME. Gottstein, T. and Grosch, W. (1990) Model study of different antioxidant properties of a- and g-tocopherol in fats, Fat Science Technology, 92, 139–144. Gryson, N., Messens, K. and Dewettinck, K. (2003) Detection of soy DNA in margarines, Mededelingen – Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen, 68, 473–476. Guiterrez, E. and Wang, T. (2004) Effect of processing on sphingolipid content in soybean products, Journal of the American Oil Chemists’ Society, 81, 971–977. Gunstone, F.D. and Pollard, M.R. (2001) Vegetable oils with fatty acid composition changed by plant breeding or by genetic modification, in Structured and Modified Lipids (ed. F.D. Gunstone), Marcel Dekker, New York, pp. 155–184. Haas, M.J. and Scott, K.M. (1996) Combined nonenzymatic-enzymatic method for the synthesis of simple alkyl fatty acid esters from soapstock, Journal of the American Oil Chemists’ Society, 73, 1393–1401. Haas, M.J., Bloomer, S. and Scott, K. (2000) Simple, high-efficiency synthesis of fatty acid methyl esters from soapstock, Journal of the American Oil Chemists’ Society, 77, 373–379. Halvorsen, J.D., Mammel, W.C. Jr. and Clements, L.D. (1993) Density estimation of fatty acids and vegetable oils based on their fatty acid composition, Journal of the American Oil Chemists’ Society, 70, 875–880. Harp, T.K. and Hammond, E.G. (1998) Stereospecific analysis of soybean triacylglycerols, Lipids, 33, 209–216. Harris, W.S., Lemke, S.L., Hansen, S.N. et al. (2008) Stearidonic acid-enriched soybean oil increased the omega-3 index, an emerging cardiovascular risk marker, Lipids, 43, 805–811. Hastert, R.C. (1996) Hydrogenation, in Bailey’s Industrial Oil and Fat Products, Vol 4: Edible Oil and Fat Products: Processing Technology (ed. Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 213–300. Hegsted, D.M., Ausman, L.M., Johnson, L.A. and Dallal, G.E. (1993) Dietary fat and serum lipids: An evaluation of the experimental data, American Journal of Clinical Nutrition, 57, 875–883. Hernandez, E. (2001) Latest developments in refining by adsorption and filtration of specialty oils with soluble silicates, in Abstracts: 92nd AOCS Annual Meetings and Expo, S98. Hicks, K.B. and Moreau, R.A. (2001) Phytosterols and phytostanols: Functional food cholesterol busters, Food Technology, 55, 63–67. Hollingsworth, P. (2001) Margarine: The over-the-top functional food, Food Technology, 55, 59–62. Hoy, C. and Xu, X. (2001) Structured triacylglycerols, in Structured and Modified Lipids (ed. F.D. Gunstone), Marcel Dekker, New York, pp. 209–239. Irwin, R. (1990) Toxicology and carcinogenesis studies of glycidol in F344/N rats and B6C3F1 mice (gavage studies). Report NTP-TR-374, NIH/PUB-90-2829; Order No. PB90-259094, National Toxicology Program, Research Triangle Park, NC. Ivanov, N.G., Mel’nikova, L.V., Klyachkina, A.M. and Germanova, A.L. (1980) Study of the toxicity, hazard, and harmful effects of glycidol on animals, Gigiena Truda i Professional’nye Zabolevaniya, 3, 42–43. Jakobsen, M.U., O’Reilly, E.J., Heitmann, B.L. et al. (2009) Major types of dietary fat and risk of coronary heart disease: A pooled analysis of 11 cohort studies, American Journal of Clinical Nutrition, 89, 1425–1432. Johnson, L.A. (2008) Oil recovery from soybeans, in Soybeans, Chemistry, Production, Processing, and Utilization (ed. L.A. Johnson, P.J. White and R. Galloway), AOCS Press, Urbana, IL, pp. 331–375. Judd, J.T., Clevidence, B.A., Muesing, R.A. et al. (1994) Dietary trans fatty acids: Effects on plasma lipids and lipoproteins of healthy men and women, American Journal of Clinical Nutrition, 59, 861–868. Jung, M.Y. and Min, D.B. (1990) Effects of a-, g-, and d-tocopherols on oxidative stability of soybean oil, Journal of Food Science, 55, 1464–1465. Jung, M.Y., Yoon, S.H. and Min, D.B. (1989) Effect of processing steps on the contents of minor compounds and oxidation of soybean oil, Journal of the American Oil Chemists’ Society, 66, 118–120. Jung, S., Maurer, D. and Johnson, L.A. (2009) Factors affecting emulsion stability and quality of oil recovered from enzyme-assisted aqueous extraction of soybeans, Bioresource Technology, 100, 5340–5347. Kamal-Eldin, A. and Andersson, R. (1997) A multivariate study of the correlation between tocopherol content and fatty acid composition in vegetable oils, Journal of the American Oil Chemists’ Society, 74, 375–380. Kamal-Eldin, A. and Appelqvist L.A. (1996) The chemistry and antioxidant properties of tocopherols and tocotrienols, Lipids, 31, 671–701.

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Soybean Oil

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Kapchie, V., Wei, D., Hauck, C. and Murphy, P.A. (2008) Enzyme-assisted aqueous extraction of oleosomes from soybeans (Glycine max), Journal of Agricultural Food Chemisty, 56, 1766–1771. Kellens, M. (2000) Oil modification processes, in Edible Oil Processing (eds W. Hamm and R.J. Hamilton), Sheffield Academic Press, Sheffield, pp. 129–173. Kemeny, Z., Recseg, K., Henon, G., Kovari, K. and Zwobada, F. (2001) Deodorization of vegetable oils: Prediction of trans polyunsaturated fatty acid content, Journal of the American Oil Chemists’ Society, 78, 973–979. Kim, J., Lieu, H., Kim, T. et al. (2006) Assessment of the potential allergenicity of genetically modified soybeans and soy-based products, Food Science and Biotechnology, 15, 954–958. Knowlton, S., Kostows, C.M. and Kelly, E.F. (1999) Functional performance of genetically modified high stearate soybean oils, 90th American Oil Chemists’ Society Meeting Abstract, Orlando, FL, S30. Kock, M. (1983) Oilseed pretreatment in connection with physical refining, Journal of the American Oil Chemists’ Society, 60, 198–202. Kok, L.L., Fehr, W.R., Hammond, E.G. and White, P.J. (1999) Trans-free margarine from highly saturated soybean oil, Journal of the American Oil Chemists’ Society, 76, 1175–1181. Konishi, H., Neff, W.E. and Mounts, T.L. (1995) Oxidative stability of soybean oil products obtained by regioselective chemical interesterification, Journal of the American Oil Chemists’ Society, 72, 1393–1398. Krishnamurthy, R.G. and Witte, V.C. (1996) Cooking oils, salad oils, and oil-based dressings, in Bailey’s Industrial Oil and Fat Products, Vol 3: Edible Oil and Fat Products: Products and Application Technology (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 193–223. Kwon, T.W., Snyder, H.E. and Brown, H.G. (1984) Oxidative stability of soybean oil at different stages of refining, Journal of the American Oil Chemists’ Society, 61, 1843–1846. Lamsal, B.P. and Johnson, L.A. (2007) Separating oil from aqueous extraction fraction of soybeans. J. Am. Oil Chem. Soc. 85, 785–792. Lau, F.Y., Hammond, E.G. and Ross, P.F. (1982) Effect of randomization on the oxidation of corn oil, Journal of the American Oil Chemists’ Society, 59, 407–411. Law, M.R. (2000) Plant sterol and stanol margarines and health, Western Journal of Medicine, 173, 43–47. Lee, I., Fatemi, S.H., Hammond, E.G. and White, P.J. (1995) Quantitation of flavor volatiles in oxidized soybean oil by dynamic headspace analysis, Journal of the American Oil Chemists’ Society, 72, 539–546. List, G.R., Emken, E.A., Kwolek, W.F., Simpson, T.D. and Dutton, H.J. (1977) ‘Zero trans’ margarines: Preparation, structure, and properties of interesterified soybean oil-soy trisaturate blends, Journal of the American Oil Chemists’ Society, 54, 408–413. List, G.R., King, J.W., Johnson, J.H., Warner, K. and Mounts, T.L. (1993) Supercritical CO2 degumming and physical refining of soybean oil, Journal of the American Oil Chemists’ Society, 70, 473–476. List, G.R., Mounts, T.L. and Lanser, A.C. (1992) Factors promoting the formation of nonhydratable soybean phosphatides, Journal of the American Oil Chemists’ Society, 69, 443–446. List, G.R., Mounts, T.L., Orthoefer, F. and Neff, W.E. (1996) Potential margarine oils from genetically modified soybeans, Journal of the American Oil Chemists’ Society, 73, 729–732. List, G.R., Neff, W.E., Holliday, R.L., King, J.W. and Holser, R. (2000) Hydrogenation of soybean oil triglycerides: Effect of pressure on selectivity, Journal of the American Oil Chemists’ Society, 77, 311–314. List, G.R., Pelloso, T., Orthoefer, F., Chrysam, M. and Mounts, T.L. (1995) Preparation and properties of zero trans soybean oil margarines, Journal of the American Oil Chemists’ Society, 72, 383–384. List, G.R., Pelloso, T., Orthoefer, F., Warner, K. and Neff, W.E. (2001) Soft margarines from high stearic acid soybean oils, Journal of the American Oil Chemists’ Society, 78, 103–104. Litchfield, C. (ed.) (1972) Distribution of fatty acids in natural triglyceride mixtures, in Analysis of Triglycerides (ed. C. Litchfield), Academic Press, New York, pp. 233–264. Liu, H. and White, P.J. (1992a) Oxidative stability of soybean oils with altered fatty acid composition, Journal of the American Oil Chemists’ Society, 69, 528–532. Liu, H. and White, P.J. (1992b) High temperature stability of soybean oils with altered fatty acid composition, Journal of the American Oil Chemists’ Society, 69, 533–537. Liu, K. (1999) Soy oil modification: Products and applications, INFORM, 10, 868–878. Lutton, E.S., Mallery, M.F. and Burgers, J. (1962) Interesterification of lard, Journal of the American Oil Chemists’ Society, 39, 233–235. Masukawa, Y. Shiro, H., Nakamura, S. et al. (2010) A new analytical method for the quantification of glycidol fatty acid esters in edible oils, Journal of Oleo Science, 59, 81–88.

Gunstone_c03.indd 101

1/21/2011 6:07:28 PM

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Matsuo, N. (2008a) Health benefits of dietary diacylglycerol in practical use, in Focus on Omega-3 (ed. W.E.M. Lands), AOCS Press, Urbana, IL, pp. 229a–242a. Matsuo, N. (2008b) Nutritional characteristics of diacylglycerol oil and its health benefits, in Focus on Omega-3 (ed. W.E.M. Lands), AOCS Press, Urbana, IL, pp. 685–698. Matsuo, N. and Tokimitsu, I. (2001) Metabolic characteristics of diacylglycerol, INFORM, 12, 1098–1102. McCord, K.L., Fehr, W.R., Wang, T. et al. (2004) Tocopherol content of soybean lines with reduced linolenate in the seed oil, Crop Science, 44, 772-–76. Mel’nikova, L.V. and Klyachkina, A.M. (1979) Study of glycidol toxicity and the direction of its harmful action on an organism, Toksikologiya Novykh Promyshlennykh Khimicheskikh Veshchestv, 15, 97–101, 145–150. Meng, Q. and Wen, Q. (2006) Improving refining yield of crude oil by using phospholipase C to hydrolyze soybean gums, Zhongguo Youzhi, 31, 36–38. Mensink, R.P., Zock, P.L., Kester, A.D.M. and Katan, K.B. (2003) Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: A metaanalysis of 60 controlled trials, American Journal of Clinical Nutrition, 77, 1146–1155. Merrill, A.H. Jr. and Schmelz, E. (2001) Sphingolipids: Metabolism-based inhibitors of carcinogenesis produced by animals, plants, and other organisms, in Handbook of Nutraceuticals and Functional Foods (ed. R.C. Wildman), CRC Press, New York, pp. 377–392. Metzroth, D.J. (1996) Shortening: Science and technology, in Bailey’s Industrial Oil and Fat Products, Vol 3: Edible Oil and Fat Products: Products and Application Technology (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 115–160. Miller, L.A. and White, P.J. (1988) High temperature stabilities of low-linolenate, high-stearate and common soybean oils, Journal of the American Oil Chemists’ Society, 65, 1324–1326. Miyazaki, H. and Tamura, Y. (2007) A study of quantitative detection method of genetically modified soybean in soy processed foods, Nagoya-shi Eisei Kenkyushoho, 53, 11–16. Morad, N.A., Mustafa Kamal, A.A., Panau, F. and Yew, T.W. (2000) Lipid specific heat capacity estimation for fatty acids, triacylglycerols, and vegetable oils based on their fatty acid composition, Journal of the American Oil Chemists’ Society, 77, 1001–1005. Moulton, K.J. and Mounts, T.L. (1990) Continuous ultrasonic degumming of crude soybean oil, Journal of the American Oil Chemists’ Society, 67, 33–38. Mounts, T.L., Abidi, S.L. and Rennick, K.A. (1996) Effect of genetic modification on the content and composition of bioactive constituents in soybean oil, Journal of the American Oil Chemists’ Society, 73, 581–586. Muench, E.W. (2005) Enzymatic degumming processes for oils from soybean, rapeseed and sunflower, Lipid Technology, 17, 155–159. Nasirullah, R.G. (2002) A unistep deodorization and deacidification technique for physical refining of heat sensitive vegetable oils, Journal of the Oil Technologists’ Association of India, 34, 57–62. Neff, W.E. and List, G.R. (1999) Oxidative stability of natural and randomized high-palmitic and highstearic-acid oils from genetically modified soybean varieties, Journal of the American Oil Chemists’ Society, 76, 825–831. Nelson, A.I., Wijeratne, W.B., Yeh, S.W., Wei, T.M. and Wei, L.S. (1987) Dry extrusion as an aid to mechanical expelling of oil from soybeans, Journal of the American Oil Chemists’ Society, 64, 1341–1347. Nobrega de Moura, J.M.L, Campbell, K., Mahfuz, A. et al. (2008) Enzyme-assisted aqueous extraction of soybeans and cream de-emulsification, Journal of the American Oil Chemists’ Society, 85, 985–995. Nobrega de Moura, J.M.L. and Johnson, L.A. (2009) Two-stage countercurrent enzyme-assisted aqueous extraction of oil and protein from soybeans, Journal of the American Oil Chemists’ Society, 86, 283– 289. Normand, L., Eskin, N.A.M. and Przybylski, R. (2003) Comparison of the frying stability of regular and low-linolenic acid soybean oils, Journal of Food Lipids, 10, 81–90. Normen, L., Dutta, P., Lia, A. and Andersson, H. (2000) Soy sterol esters and b-sitostanol ester as inhibitors of cholesterol absorption in human small bowel, American Journal of Clinical Nutrition, 71, 908–913. Noureddini, H., Teoh, B.C. and Clements, L.D. (1992) Viscosities of vegetable oils and fatty acids, Journal of the American Oil Chemists’ Society, 69, 1189–1191. Ohnishi, M. and Fujino, Y. (1982) Sphingolipids in immature and mature soybeans, Lipids, 17, 803–810. Orthoefer, F.T. (1996) Vegetable oils, in Bailey’s Industrial Oil and Fat Products, Vol 1: Edible Oil and Fat Products: General Applications (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 19–44.

Gunstone_c03.indd 102

1/21/2011 6:07:28 PM

Soybean Oil

103

Ozawa, Y., Sato, H., Nakatani, A. et al. (2001) Chemical composition of soybean oil extracted from hypocotyl-enriched soybean raw material and its cholesterol lowering effects in rats, Journal of Oleo Science, 50, 217–223. Pagliero, C., Ochoa, N., Marchese, J. and Mattea, M. (2001) Degumming of crude soybean oil by ultrafiltration using polymeric membranes, Journal of the American Oil Chemists’ Society, 78, 793–796. Pan, M., Chai, Y. and Du, P. (2008) Enzyme catalyzed degumming of soybean oil by a phospholipase A1, Shipin Gongye Keji, 29, 219–222. Penk, G. (1986) Practical experience with the Alcon Process, in Proceedings of the World Conference on Emerging Technologies in the Fats and Oil Industry (ed A.R. Baldwin), AOCS Press, Champaign, IL, pp. 38–45. Perkins, E.G. (1995a) Composition of soybeans and soybean products, in Practical Handbook of Soybean Processing and Utilization (ed D.R. Erickson), AOCS Press, Champaign, IL, pp. 9–28. Perkins, E.G. (1995b) Physical properties of soybeans, in Practical Handbook of Soybean Processing and Utilization (ed D.R. Erickson), AOCS Press, Champaign, IL, pp. 29–38. Pickard, M.D., Jones, T.J. and Tyler, R.T. (1996) By-products utilization, in Bailey’s Industrial Oil and Fat Products, Vol 4: Edible Oil and Fat Products: Processing Technology (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 603–630. Pryde, E.H. (1980a) Composition of soybean oil, in Handbook of Soy Oil Processing and Utilization (eds D.R. Erickson, E.H. Pryde, O.L.Brekke, T.L. Mounts and R.A. Falb), AOCS Press, Champaign, IL, pp. 13–31. Pryde, E.H. (1980b) Physical properties of soybean oil, in Handbook of Soy Oil Processing and Utilization (eds D.R. Erickson, E.H. Pryde, O.L. Brekke, T.L. Mounts and R.A. Falb), AOCS Press, Champaign, IL, pp. 33–47. Rabelo, J., Batista, E., Cavaleri, F.W. and Meirelles, A.J.A. (2000) Viscosity prediction for fatty systems, Journal of the American Oil Chemists’ Society, 77, 1255–1261. Raghuveer, K.G. and Hammond, E.G. (1967) The influence of glyceride structure on the rate of autoxidation, Journal of the American Oil Chemists’ Society, 44, 239–243. Ramamurthi, S., McCurdy, A.R. and Tyler, R.T. (1998) Deodorizer distillate: A valuable byproduct, in Proceedings of the World Conference on Oilseed Edible Oils Processing, Vol. 1 (eds S.S. Koseoglu, K.C. Rhee and R.F. Wilson), AOCS Press, Champaign, IL, pp. 130–134. Reske, J., Siebrecht, A. and Hazebroek, J. (1997) Triacylglycerol composition and structure in genetically modified sunflower and soybean oils, Journal of the American Oil Chemists’ Society, 74, 989–998. Ribeiro, A.P.B., Bei, N., Goncalves, L.A.G., Petrus, J.C.C. and Viotto, L.A. (2008) The optimisation of soybean oil degumming on a pilot plant scale using a ceramic membrane, Journal of Food Engineering, 87, 514–521. Rihani, D.N. and Doraiswamy, L.K. (1965) Estimation of heat capacity of organic compounds from group contributions, Industrial and Engineering Chemistry Fundamentals, 4, 17–21. Rodenbush, C.M., Hsieh, F.H. and Viswanath, D.S. (1999) Density and viscosity of vegetable oils, Journal of the American Oil Chemists’ Society, 76, 1415–1419. Sato, H., Ito, K., Sakai, K. et al. (2001) Effects of soybean-germ oil on reducing serum cholesterol level, Journal of Oleo Science, 50, 649–656. Scherder, C.W., Fehr, W.R., Welke, G.A. and Wang, T. (2006) Tocopherol content and agronomic performance of soybean lines with reduced palmitate, Crop Science, 46, 1286–1290. Schneider, M. (1986) Phospholipids, in Proceedings of the World Conference on Emerging Technologies in the Fats and Oils Industry (ed. A.R. Baldwin), AOCS Press, Champaign, IL, pp. 160–164. Schneider, M. (2008) Lecithin: Major sources, composition and processing, in Phospholipid Technology and Applications (ed. F.D. Gunstone), Lipid Library 22, Oily Press, Bridgwater, pp. 21–40. Seger, J.C. and van de Sande, R.L.K.M. (1990) Degumming – theory and practice, in World Conference Proceedings Edible Fats and Oils Processing: Basic Principles and Modern Practices (ed D.R. Erickson), AOCS Press, Champaign, IL, pp. 88–93. Shen, N., Fehr, W., Johnson, L. and White, P. (1997) Oxidative stabilities of soybeans with elevated palmitate and reduced linolenate contents, Journal of the American Oil Chemists’ Society, 74, 299–302. Shimada, Y., Nakai, S., Suenaga, M. et al. (2000) Facile purification of tocopherols from soybean oil deodorizer distillate in high yield using lipase, Journal of the American Oil Chemists’ Society, 77, 1009–1013. Shintani, D.S. and DellaPenna, D. (1998) Elevating the vitamin E content of plants through metabolic engineering, Science, 282, 2098–2100.

Gunstone_c03.indd 103

1/21/2011 6:07:28 PM

104

Vegetable Oils in Food Technology

Sipos, E.F. and Szuhaj, B.F. (1996a) Lecithins, in Bailey’s Industrial Oil and Fat Products, Vol 1: Edible Oil and Fat Products: General Applications (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 311–396. Sipos, E.F. and Szuhaj, B.F. (1996b) Soybean oil, in Bailey’s Industrial Oil and Fat Products, Vol 2: Edible Oil and Fat Products: Oils and Oilseeds (ed Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 497–602. Soares, M., Ribeiro, A., Goncalves, L., Fernades, G.B. and Bolini, H.M.A. (2004) Sensory acceptance of soybean oil deodorized and degummed by ultrafiltration, Boletim do Centro de Pesquisa e Processamento de Alimentos, 22, 283–294. Soheili, K.C., Artz, W.E. and Tippayawat, P. (2002) Pan-heating of low-linolenic acid and partially hydrogenated soybean oils, Journal of the American Oil Chemists’ Society, 79, 287–290. Soni, M.G., Kimura, H. and Burdock, G.A. (2001) Chronic study of diacylglycerol oil in rats, Food Chemisty and Toxicology, 39, 317–329. Stern, R., Hillion, G., Gateau, P. and Guibet, J.C. (1986) Preparation of methyl and ethyl esters from crude vegetable oils and soap stock, Proceedings: World Conference on Emerging Technologies in the Fats and Oils Industry (ed A.R. Baldwin), AOCS Press, Champaign, IL, pp. 420–422. Streit, L.G., Fehr, W.R., Welke, G.A., Hammond, E.G. and Cianzio, S.R. (2001) Family and line selection for reduced palmitate, saturates, and linolenate of soybean, Crop Science, 41, 63–67. Su, C., Gupta, M. and White, P. (2003a) Oxidative and flavor stabilities of soybean oils with low- and ultralow-linolenic acid composition, Journal of the American Oil Chemists’ Society, 80, 171–176. Su, C., Gupta, M. and White, P. (2003b) Multivariate sensory characteristics of low and ultra-low linolenic soybean oils displayed as faces, Journal of the American Oil Chemists’ Society, 80, 1231–1235. Subramanian, S., Nakajima, M., Yasui, A. et al. (1999) Evaluation of surfactant-aided degumming of vegetable oils by membrane technology, Journal of the American Oil Chemists’ Society, 76, 1247–1253. Sumner, C.E. Jr., Barnicki, S.D. and Dolfi, M.D. (1995) Process for the production of sterol and tocopherol concentrates, US Patent 5424457. Sundram, K., Khor, H.T., Ong, A.S.H. and Pathmanathan, R. (1989) Effect of dietary palm oils on mammary carcinogenesis in female rats induced by 7,12-dimethylbenz(a)anthracene, Cancer Research, 49, 1447– 1451. Teberikler, L., Koseoglu, S. and Akgerman, A. (2001) Selective extraction of phosphatidylcholine from lecithin by supercritical carbon dioxide/ethanol mixture, Journal of the American Oil Chemists’ Society, 78, 115–119. Tekin, A. and Hammond, E.G. (1998) Factors affecting the electrical resistivity of soybean oil, Journal of the American Oil Chemists’ Society, 75, 737–740. Tekin, A. and Hammond, E.G. (2000) Factors affecting the electrical resistivity of soybean oil methyl ester, Journal of the American Oil Chemists’ Society, 77, 281–283. USDA-NASS Agricultural Statistics, http://www.nass.usda.gov, accessed October 2010. van Nieuwenhuyzen, W. and Tomas, M.C. (2008) Update on vegetable lecithin and phospholipid technologies, European Journal of Lipid Science Technology, 110, 472–486 Vesper, H, Schmelz, E.M., Nikolova-Karakashian, M.N. et al. (1999) Sphigolipids in food and the emerging importance of sphingolipids to nutrition, Journal of Nutrition, 129, 1239–1250. Vlahakis, C. and Hazebroek, J. (2000) Phytosterol accumulation in canola, sunflower, and soybean oils: Effect of genetics, planting location, and temperature, Journal of the American Oil Chemists’ Society, 77, 49–53. Wang, L., Wang, T. and Fehr, W.R. (2006) Effect of seed development stage on sphingolipid and phospholipid contents in soybean seeds, Journal of Agricultural Food Chemistry, 54, 7812–7816. Wang, T, and Briggs. J.L. (2002) Rheological and thermal properties of soybean oils with modified FA compositions, Journal of the American Oil Chemists’ Society, 79, 831–836. Wang, T. and Hammond, E.G. (1999) Fractionation of soybean phospholipids by high-performance liquid chromatography with an evaporative light scattering detector, Journal of the American Oil Chemists’ Society, 76, 1313–1321. Wang, T. and Johnson, L.A. (2001a) Survey of soybean oil and meal qualities produced by different processes, Journal of the American Oil Chemists’ Society, 78, 311–318. Wang, T. and Johnson, L.A. (2001b) Natural refining of extruded-expelled soybean oils having various fatty acid compositions, Journal of the American Oil Chemists’ Society, 78, 461–466. Wang, T. and Johnson, L.A. (2001c) Refining normal and genetically enhanced soybean oils obtained by various extraction methods, Journal of the American Oil Chemists’ Society, 78, 809–815.

Gunstone_c03.indd 104

1/21/2011 6:07:28 PM

Soybean Oil

105

Wang, T., Hammond, E.G. and Fehr, W.R. (1997) Phospholipid fatty acid composition and stereospecific distribution of soybeans with a wide range of fatty acid compositions, Journal of the American Oil Chemists’ Society, 74, 1587–1594. Wang, T., Hammond, E.G. and Fehr, W.R. (2001a) Neutral and polar lipid phase transition of soybeans with altered saturated fatty acid contents, Journal of the American Oil Chemists’ Society, 78, 1139–1144. Wang, T., Harp, T., Hammond, E.G., Burris, J.S. and Fehr, W.R. (2001) Seed physiological performance of soybeans with altered fatty acid contents, Seed Science Research, 11, 93–97. Wang, T., Jiang, Y. and Hammond, E.G. (2005) Effect of randomization on the oxidative stability of corn oil, Journal of the American Oil Chemists’ Society, 82, 111–117. Wang, W., Ma, C. and Wan, D. (2006) Research of membrane degumming process in miscella, Zhongguo Liangyou Xuebao, 21, 284–287. Warner, K. (2005) Effects on the flavor and oxidative stability of stripped soybean and sunflower oils with added pure tocopherols, Journal of Agricultural Food Chemistry, 53, 9906–9910. Warner, K. (2008) Food uses for soybean oil and alternatives to trans fatty acids in foods, in Soybeans, Chemistry, Production, Processing, and Utilization (ed. L.A. Johnson, P.J. White and R. Galloway), AOCS Press, Urbana, IL, pp. 483–498. Warner, K. and Fehr, W. (2008) Mid-oleic/ultra low linolenic acid soybean oil: A healthful new alternative to hydrogenated oil for frying, Journal of the American Oil Chemists’ Society, 85, 945–951. Warner, K. and Gupta, M. (2003) Frying quality and stability of low- and ultra-low-linolenic acid soybean oils, Journal of the American Oil Chemists’ Society, 80, 275–280. Warner, K. and Gupta, M. (2005) Potato chip quality and frying oil stability of high oleic acid soybean oil, Journal of Food Science, 70, S395–S400. Weihrauch, J.L. and Gardner, J.M. (1978) Sterol content of foods of plant origin, Journal of the American Dietetic Association, 73, 39–47. Wendel, A. (1995) Lecithin, in Kirk-Othmer Encyclopedia of Chemical Technology, Vol 15 (ed. M. HoweGrant), 4th edn, John Wiley & Sons, Inc., New York, pp. 192–210. Whent, M., Hao, J., Slavin, M. et al. (2009) Effect of genotype, environment, and their interaction on chemical composition and antioxidant properties of low-linolenic soybeans grown in Maryland, Journal of Agricultural Food Chemistry, 57, 10163–10174. White, P.J. and Miller, L.A. (1988) Oxidative stabilities of low-linolenate, high-stearate and common soybean oils, Journal of the American Oil Chemists’ Society, 65, 1334–1338. Wilkes, R.S. (2008) Low linolenic soybeans and beyond, Lipid Technology, 20, 277–279. Wilson, R.F. (1999) Alternatives to genetically modified soybean – the Better Bean Initiative, Lipid Technology, 10, 107–110. Winkler, J. K., Warner, K. and Glynn, M.T. (2007) Effect of deep-fat frying on phytosterol content in oils with differing fatty acid composition, Journal of the American Oil Chemists’ Society, 84, 1023–1030. Winters, R.L. (1990) Deodorizer distillate, in Proceedings: World Conference Edible Fats and Oils Processing, Basic Principles and Modern Practices (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 402–405. Woerfel, J.B. (1995) Extraction, in Practical Handbook of Soybean Processing and Utilization (ed. D.R. Erickson), AOCS Press, Champaign, IL, pp. 65–92. Wolf, F.R. and Knowlton, S. (1999) Edible applications of high oleic soybean oil, 90th American Oil Chemists’ Society Meeting Abstract, S24. Wu, H., Weng, X., Qiu, O. and Li, L. (2001) Extraction of tocopherol from soybean oil deodorizer, Shanghai Daxue Xuebao-Ziran Kexueban, 7, 331–333. Wu, Y. and Wang, T. (2001) Phospholipid class and fatty acid compositions of modified soybeans, 92nd AOCS Annual Meeting and Expo, INFORM Supplement, S97. Yamaya, A., Endo, Y., Fujimoto, K. and Kitamura, K. (2007) Effects of genetic variability and planting location on the phytosterol content and composition in soybean seeds, Food Chemistry, 102, 1071–1075. Yang, B., Wang, Y. and Yang, J. (2005) Effects of acid treatment on enzymatic degumming of soybean oil, Zhongguo Youzhi, 30, 40–42. Yang, B., Zhou, R., Yang, J., Wang, Y. and Wang, W. (2008) Insight into the enzymatic degumming process of soybean oil, Journal of the American Oil Chemists’ Society, 85, 421–425. Yasukawa, T. and Katsurgi, Y. (2008) Diacylglycerols, in Diacylglycerol Oil (ed. Y. Katsuragi), 2nd edn, AOCS Press, Champaign, IL, pp. 1–16. Yasukawa, T. and Yasunaga, K. (2001) Nutritional functions of dietary diacylglycerols, Journal of Oleo Science, 50, 427–432.

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4

Canola/Rapeseed Oil

Roman Przybylski

4.1

INTRODUCTION

In the past two decades, production of Brassica oilseeds has become third only to palm and soybeans as a source of vegetable oil (see Chapter 1). Canola oil (low-erucic acid and low- glucosinolate rapeseed oil) is now held by some to be the best nutritional edible oil available. This oil was developed after significant improvement and modification of the original high-erucic acid rapeseed oil (HEAR). The level of erucic acid has been reduced to below 2%, and in many currently produced canola oils is below 1% of the total fatty acids. Additionally, the level of glucosinolates in the seed has been lowered to a level below 30 μmol/g, resulting in better-quality meal. In this chapter, the origin, composition, properties, and utilization of both canola and HEAR oils for food purposes are discussed. Oilseed rape species used to produce canola oil and meal are from the Brassica genus in the Cruciferae family. They were first cultivated in India almost 4000 years ago. Large-scale planting of rape oilseed was first reported in Europe in the thirteenth century. The Brassica species probably evolved from the same common ancestor as wild mustard (Sinapis), radish (Raphanus), and arugula (Eruca). Early rapeseed cultivars had high levels of erucic acid in the oil and high levels of glucosinolates in the meal. The presence of these components was considered to be a health concern. The high levels of erucic acid were blamed for producing fatty deposits in the heart, skeletal muscles, and adrenals of rodents as well as impairing growth. Plant-breeding programs were initiated in Canada, and in 1959 a rapeseed line (Liho) containing low levels of erucic acid was identified. A program of backcrossing and selection was conducted to transfer the low-erucic acid trait into agronomically adapted cultivars. This led to the first low-erucic acid cultivar of B. napus (Oro) in 1968 and the first low-erucic acid B. rapa cultivar (Span) in 1971. Because of health concerns associated with high levels of erucic acid, by 1974 over 95% of the rapeseed grown in Canada was from low-erucic acid varieties. Glucosinolates were also considered detrimental in rapeseed meal fed to poultry, swine, and ruminants. Their hydrolyzed products, isothiocyanates and other sulfur-containing compounds, interfere with the uptake of iodine by the thyroid gland, contribute to liver disease, and reduce growth and weight gain in animals. Consequently, plant breeders realized that if rapeseed meal were to be used in animal feed, the glucosinolate content should be reduced. A Polish line with a low-glucosinolate trait (Bronowski) was identified by Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Krzymanski in the late 1950s. Breeding efforts to introduce this trait into low-erucic acid lines, led by Baldur Stefansson at the University of Manitoba, resulted in the release of the world’s first low-erucic, low-glucosinolate cultivar of B. napus, often called the doublezero rapeseed. This was followed in 1977 by the release of the first low-erucic, lowglucosinolate cultivar of B. rapa (Candle) by Keith Downey of the National Research Council of Canada in Saskatoon. Approximately 80% of all Canadian rapeseed acreage in 1980 contained the double-zero cultivars. The detailed history of the development of canola is described in a booklet entitled ‘The Story of Rapeseed in Western Canada’ (Saskatchewan Wheat Pool 1974). The name ‘canola’ was registered by the Western Canadian Oilseed Crushers in 1978 and subsequently transferred to the Canola Council of Canada in 1980. The name included cultivars containing less than 5% erucic acid in the oil and less than 3 mg/g aliphatic glucosinolates in the meal. In 1986 the definition of canola was amended to B. napus, and B. rapa lines with less than 2% erucic acid in the oil and less than 30 μmol/g glucosinolates in the air-dried, oil-free meal and canola oil was added to the GRAS list of food products in the US. It proved to be more difficult to introduce the low-erucic acid trait into European rapeseed lines because they were primarily of the winter type. This extended the time required to produce each generation, and crosses between spring low-erucic acid rapeseed (LEAR) cultivars and winter lines resulted in undesirable segregates. Nevertheless, the development of European LEAR varieties was accomplished within 15 years. European acreage of rapeseed declined during the 1970s as a result of health concerns. In 1977 the low-erucic acid trait was made mandatory in Europe. Initially the new LEAR cultivars produced lower yields and lower oil content compared to the traditional rapeseed cultivars. Subsequent plant breeding overcame these problems, with European production of LEAR increasing substantially by 1984. The other rapeseed-growing areas of the world, notably India and China, did not take part in the development and conversion to canola-type rapeseed, and HEAR still predominates in these areas. Canola oil produced in Canada and the United States is now produced from genetically modified seeds of Brassica napus and Brassica rapa (campestris). However, high-oleic, low-linolenic canola oil designed to replace trans-containing frying fats is not a genetically modified variety, developed by classical breeding by Dow AgroSciences. Change in the labeling regulations in the United States and Canada and health concerns related to the negative effect of trans fats adjusted the direction of vegetable oils processing, development, and utilization. Current canola/rapeseed-breeding programs are focusing on the development of oils with characteristics to meet the specifications of particular application. The main focuses in the development of new oils are the nutritional properties and advances in functional oils containing specific nutraceuticals.

4.2 4.2.1

COMPOSITION Nature of edible oils and fats

Edible oils and fats are composed primarily of triacylglycerols, usually present at 94–99% of the total lipid amounts (Mag 1990). The typical composition of canola, rapeseed, and soybean oils is presented in Table 4.1.

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Table 4.1

109

Constituents of canola, rapeseed, and soybean oils.

Component Triacylglycerols (%) Phospholipids (%) Crude oil Water degummed Acid degummed Free fatty acids (%) Unsaponifiables (%) Tocopherols (ppm) Chlorophylls (ppm) Sulfur (ppm)

Canola

Rapeseed

Soybean

94.4–99.1

91.8–99.0

93.0–99.2

up to 2.5 up to 0.6 up to 0.1 0.4–1.2 0.5–1.2 700–1200 5–50 3–25

up to 3.5 up to 0.8 – 0.5–1.8 0.5–1.2 700–1000 5–55 5–35

up to 4.0 up to 0.4 up to 0.2 0.3–1.0 0.5–1.6 1700–2200 Trace Nil

Source: Adapted from Mag (1990) and Ying et al. (1989).

4.2.2

Fatty acid composition of canola oil

The stigma of the erucic acid (22:1 n-9) in rapeseed oil has lingered, despite firm evidence that this fatty acid is more of a threat to rats than to humans. It is sufficient to say that the discovery of the chain-shortening metabolic pathway reducing erucic acid to oleic acid by peroxisome enzymes was a fundamental breakthrough in the understanding of fatty acid metabolism in the past few decades. Once in the oleic acid form, the erucic acid residue is as readily catabolized by mitochondria as are palmitic and other fatty acids (Ackman 1990). The decrease in the level of erucic acid in rapeseed oil resulted in a marked increase in C18 acids and they make up around 95% of all fatty acids present in canola oil (Table 4.2). Plant breeders have also developed canola oil with the linolenic acid content reduced to 2% (Scarth and Tang 2006) (Table 4.2). The storage stability of this oil showed improvement compared to regular canola oil (Przybylski et al. 1993b). The frying performance of this oil was improved along with better storage stability of the French fries and potato chips fried in it (Petukhov et al. 1999; Warner and Mounts 1993). Canola has been further genetically modified to produce oil with an oleic acid content raised from 60% to 85% (Abidi et al. 1999), but field production of this oil showed that the very high content of oleic acid was hard to reproduce. High-oleic acid canola oil resembles the composition of olive oil more closely than that of regular canola oil. Warner and Mounts (1993) found that up to 2% of linolenic acid is required in frying oils to form the positive characteristic flavor in fried foods. This is due to the formation of oxidation products from linolenic acid, which are the main factors in the formation of the fried food flavor. Recently, canola oil with a high content of lauric acid (31%) was developed to be used in confectionery coatings, coffee whiteners, whipped toppings, and center-filling fats (Table 4.2). Further, canola oil with an elevated level of stearic acid is available to be used as a replacement for hydrogenated fats in bread and bakery markets (Vecchio 1996). Canola oil containing approximately 10% of palmitic acid for improved crystallization properties has been developed. Canola oil for the health food market containing up to 40% of γ-linolenic acid is also available, however not in commercial amounts (Tso et al. 2001).

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Table 4.2 Comparison of major fatty acids in regular and modified canola and soybean oils (w/w %). Fatty acid

HEAR

LLCO

– – 0.1 3.6 1.5 0.6 0.3 0.2

– – – 4.0 1.0 1.0 0.8 0.3

Saturated 16:1 18:1 20:1 22:1

6.3 0.2 61.6 1.4 0.2

MUFA 18:2n-6 18:3n-3 18:3n-6 PUFA

10:0 12:0 14:0 16:0 18:0 20:0 22:0 24:0

Canola

HOCO*

HlaCO*

– – 0.1 3.9 1.3 0.6 0.4 0.3

– – 0.1 3.4 2.5 0.7 0.2 0.1

0.1 31.3 4.2 3.3 1.1 0.3 0.2 0.2

7.1 0.3 14.8 10.0 45.1

6.6 0.2 61.4 1.5 0.1

7.0 0.1 81.3 1.5 0.1

62.4 21.7 9.6 –

69.7 14.1 9.1 1.0

63.1 28.1 2.1 –

31.3

23.2

30.2

GLCO

HSCO*

HOLLCO**

SOY

– – 0.1 4.2 3.7 1.0 0.5 0.2

– – 0.1 3.6 27.5 1.2 0.4 0.2

– – – 3.7 1.7 0.6 0.4 0.2

– – 0.1 10.8 4.0 – – –

40.7 0.2 35.1 0.8 0.2

9.9 0.2 24.4 0.8 0.1

33.0 0.2 33.5 0.3 0.1

6.6 0.2 70.4 1.4 0.1

14.9 0.3 23.8 0.2 –

83.0 6.5 4.1 –

36.3 14.6 8.4 –

25.5 26.1 1.3 37.2

34.1 18.4 13.7 –

72.3 17.9 1.8 –

24.3 53.3 7.6 –

10.6

23.0

64.6

32.1

19.7

60.8

Source: Adapted from Ackman (1990); Vecchio (1996); Tso et al. (2001). Notes: * Neff et al. (1994, 1997); ** Results from Przybylski’s lab. Key: LLCO = low linolenic acid canola oil GLCO = canola oil with gamma linolenic acid HOCO = high oleic acid canola oil HOLLCO = high oleic low linolenic canola frying oil HSCO = canola oil with high content of stearic acid LTCO = canola oil with high content of lauric acid MUFA = monounsaturated fatty acids PUFA = polyunsaturated fatty acids SUN = sunflower oil

4.2.3

Minor fatty acids

Most of the minor fatty acids present in canola/rapeseed oil differ from the usual common fatty acids in the location of the double bond and a few other minor fatty acids with unusual structural features were identified. Many of the minor fatty acids in canola/rapeseed oils belong to the n-7 series of monoenic fatty acids, rather than the more common n-9 isomers. Rapeseed/canola oils contain unusual quantities of n-7 fatty acids (Ackman 1990). A similar series of minor fatty acids was found in B. rapa variety Candle. These are usually present at levels below 0.1%, though the 16:1 n-7 acid attains 0.3% (Ratnayake and Daun 2004). Conjugated 18:2 fatty acids have also been found in canola oils (Koba et al. 2007). Some of these acids are artefacts of refining and deodorization, although some were also observed as natural components in several oil seeds. The refining process itself is a source of artefact fatty acids due to the isomerization of one or more of the cis double bonds of PUFA. Small amounts of geometrical isomers of linoleic (9t,12t-18:2; 9c,12t -18:2 and 9t,12c-18:2) and α-linolenic acids (9t,12c,15t-18:3; 9c,12c,15t-l8:3; 9c,12t,15c-18:3 and 9t,12c,15c-18:3) are present in processed canola/

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111

rapeseed oils (Cmolik et al. 2007). These trans isomers were found in all processed vegetable oils that contain linoleic and linolenic acids and may account for 1% or more of the parent acids (Lambelet et al. 2003; Wolff 1993). The trend in the development of canola oil for the nutraceutical market implemented conjugated linoleic acid into acylglycerides of this oil; this fatty acid was produced by the plant (Koba et al. 2007). Canola oil is the only known edible oil containing one or more fatty acids with a sulfur atom as the integral part of the molecule. The structure of the proposed molecule of this fatty acid suggests the possibility of the formation or presence of many isomers (Wijesundera and Ackman 1988). In the sediment from industrial winterization, long-chain saturated minor fatty acids and alcohols with 26 to 32 carbon atoms have been found in waxes and triacylglycerols (Przybylski et al. 1993a). Most of these compounds are extracted from the seed coat and can initiate sediment formation in canola oil (Hu et al. 1994).

4.2.4

Triacylglycerols

Triacylglycerols (TAG) are the most abundant lipid class found in canola oil. The combination of fatty acids on the glycerol moiety leads to a mixture of triacylglycerols, with the number of possible combinations equal to the cubic involution of the fatty acid number. The TAG molecular species profile represents a key to understanding the physical characteristics of the oil and also is a unique means of identification, which has been used in various instances (Lee et al. 2008). The position of fatty acids on the glycerol molecule was originally found for HEAR oil to be based on saturation. Long-chain acids (C20–C24) and saturated fatty acids are placed in the sn-1 and sn-3 positions by enzyme-controlled acylation, while unsaturated C18 acids, especially linoleic and linolenic, are incorporated in the sn-2 position (Kallio and Currie 1993). Jaky and Kurnik (1981) investigated the concentration of linoleic acid in the sn-1,3 and sn-2 positions. They found that in HEAR oil at least 95% of the linoleic acid was concentrated in the sn-2 position, whereas in canola oil only 54% was there. The composition of the triacylglycerols in modified canola oils is presented in Table 4.3. As can easily be predicted, in canola oils containing elevated amounts of oleic acid, triolein is the most abundant. In regular canola oil five triacylglycerols were detected, in decreasing order triolein, linoleo-diolein, linoleno-diolein, dilinoleo-olein, and linoleno-linoleo-olein. Modified canola/rapeseed oils containing elevated amounts of specific fatty acids encompass triacylglycerols where these fatty acids are the main components and distributed accordingly to the rules described in this section (Table 4.3). The increased amounts of linoleic acid in canola oil replaced the erucic acid in the sn-1,3 position. Surprisingly, Kallio and Currie (1993) found that triacylglycerols with acyl carbon number 54 and two double bonds (ACN 54:2) consisted of triacylglycerol where stearic acid was present predominantly in the sn-2 position when analyzed in turnip oil (Brassica campestris). Triacylglycerols with saturated acids in this position usually have a higher melting point, poor solubility, and can cause problems with digestibility. Additionally, high-melting triacylglycerols can stimulate/initiate sediment formation and affect the clarity of the oil (Liu et al. 1993). Neff and colleagues (Neff et al. 1994, 1997; Byrdwell and Neff 1996), using HPLC combined with FID and MS, examined the TAG composition of a number of genetically modified low α-linolenic, high stearic, and high lauric acid canola lines (Table 4.4). These lines were developed with the aim of providing oils with improved storage stability,

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Table 4.3 TG LnLnLn LnLnL LnLL LnLnO LnLnP LLL LnLO LnLP LnLnS LnLS LLO LnOO LLP LnOP LnPP LOO LLS LnOS LOP PLP OOO LOS POO LnSS SLP POP PPP SOO SLS SOP PPS SPS SOS PSS SSS Unidentified

Composition of major triacylglycerols of regular and modified canola oils (%). HLaCO

HSCO

HOCO

Canola

HOLLCO

TG

HLaCO

0.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.1 0 0 0 0 3.3 0 0.7 0 0 0 0 0 0 0 0 0 0 0.5 0 6.1

0 0.3 0.2 1.0 0.2 1.0 1.5 2.6 0.8 2.3 2.2 5.7 1.0 0.2 0.1 5.9 2.9 11.1 1.0 1.0 6.2 11.9 1.9 9.1 0 0.4 0.1 9.7 9.3 1.4 0.7 0 6.1 0.6 0.2 1.4

0 0.5 0.3 0.1 0 0.2 1.5 0.5 0 0 1.1 8.6 0.8 1.1 0 12.7 0.4 0 2.2 0.2 45.5 1.0 7.7 0 0.4 0.3 2.8 5 0.4 0.3 0.6 0.8 3.2 0.6 0.1 1.1

0.2 0.6 1.4 1.7 0.2 1.3 7.6 0.9 0 0 8.4 10.4 1.4 2.1 0 22.3 0.3 0 5.7 0.3 22.4 1.6 4.6 0 0.2 0.2 0.1 2.6 0.4 0.1 0.5 0.2 0 0 0.1 2.2

0 0.1 0.5 0.4 0.1 0.9 3.2 0.6 0 0 7.4 5.5 1.2 0.8 0 21.8 0.4 0 4.8 0.2 31.3 1.8 6.8 0 0.3 0.3 2.3 4.0 0.2 0.2 1.3 0.6 0 0 0.4 2.6

LaLnLn LaLaLn LaLLn LaLaL LaOLn LaML+LaPLn LaLaO LaOL LaMO LaOO LaPO LaSO MOO

0.1 7.4 2.3 14.2 4.0 2.0 27.4 6.6 5.6 11.2 3.6 1.4 1.3

Source: Adapted from Neff et al. (1994, 1997). Note: Oils abbreviations as in Table 4.2. Key: L = linoleic La = lauric Ln = linolenic M = myristic O = oleic P = palmitic S = stearic TG = triacylglycerols

better fry life and stability in food products, reducing the contribution of linoleic and α-linolenic acids, and increasing the contribution of oleic and saturated fatty acids. The triacylglycerol composition showed considerable variation (Table 4.4). For regular canola oil, triacylglycerols LnLO, LnOO, LOO, LOP, and OOO (Ln = linolenic; L = linoleic;

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Table 4.4 Fatty acid

Regiospecific distribution of fatty acids at glycerol for regular and modified canola oils. Fatty acids in sn-2 position (%)

HLaCO HSCO HOCO Canola 12:0 14:0 16:0 18:0 20:0 22:0 24:0 16:1 18:1 20:1 24:1 18:2 18:3

113

2.0 0.2 0.6 0.9 – – – 0.1 54.5 – – 27.7 14.0

– – 0.4 1.0 – – – 0.2 42.8 – – 34.7 21.0

– 0.2 0.4 0.9 – – – 0.1 81.2 – – 10.7 6.5

– – – – – – – 0 50.2 – – 36.2 13.6

Fatty acids in sn-1,3 positions (%)

HOLLCO HLaCO HSCO HOCO Canola HOLLCO – – 0.2 0.3 – – – 0.1 66.0 – – 28.5 4.9

46.0 6.2 4.7 1.2 0.5 0.3 – 0.3 25.4 1.1 – 8.1 6.2

– 0.1 5.2 40.7 3.0 0.6 0.2 0.2 28.9 0.5 0.4 10.2 10.1

– 0.1 4.6 3.3 1.1 0.3 – 0.1 81.4 2.3 – 4.4 2.9

– 0.3 5.8 3.4 1.1 0.4 0.5 0.2 64.9 1.8 – 15.5 6.5

– – 4.9 3.1 1.1 0.6 0.5 0.2 71.7 1.8 – 13.6 2.5

Source: Adapted from Neff et al. (1994, 1997). Note: Canola oils abbreviations as in Table 4.2.

O = oleic; S = stearic; La = lauric; and P = palmitic) were detected at amounts higher than 5%. In the high stearic oil the same triacylglycerols were observed at varied amounts: LnLO (1–9%), LnOO (2–16%), LOO (5–19%), LOP (1–5%), and OOO (4–23%). Triacylglycerols LLS, LnOS, LOS, LnSS, SLS, and SOS were not abundant in regular canola oil but were detected in oils with the increased stearic acid content (Table 4.4). In canola oil with elevated amounts of lauric acid, the following triacylglycerol species were detected: LaLaO, LaLaL, LaOO, LaOL, and LaMO. These triacylglycerols were not previously reported in canola/rapeseed varieties (Neff et al. 1994, 1997). As shown in Table 4.4, genetically modified canola oils containing α-linolenic and linoleic acids were preferentially attached in the sn-2 position, while saturated fatty acids were at sn-1,3 positions (Neff et al. 1994, 1997). Monounsaturated fatty acids, including oleic acid, were not preferentially placed on the glycerol molecule. Exceptional among monounsaturated fatty acids is the minor fatty acid eicosenoic acid (20:1), which was predominantly present at sn-1,3 positions (Neff et al. 1994, 1997).

4.2.5

Polar lipids

Sosulski and co-workers (1981) examined the phospholipids and glycolipids in several rapeseed cultivars, including a low-erucic acid winter cultivar grown in Poland, and found that phospholipids comprise 3.6% of the oil while glycolipids contributed only 0.9%. A later study by Przybylski and Eskin (1991) reported changes in phospholipids during canola oil processing (Table 4.5). Significant amounts of phosphatidic acid (PA) are formed during processing as a result of the hydrolysis of other phospholipids. This can be explained as the effect of phospholipases and hydrothermal treatment during the conditioning of flaked seeds. Zajic and co-workers (1986) observed an increase in the amount of phospholipids from 0.5% to 15% during conditioning of seed flakes at different parameters. Hydratable phospholipids such as the phosphatidylcholines (PC)

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Table 4.5

Composition of phospholipids in canola oil during processing (%).

Processing level

Phosphorus (mg/kg)

PL (%)

PC

PE

PI

PA

PS

LPE

LPC

GG

DAG

Solvent Expeller Crude Degummed

529.0 242.3 301.2 12.2

1.4 0.6 0.8 0.05

31.2 34.3 17.8 2.8

18.8 16.1 16.6 10.8

19.7 18.7 11.8 28.9

21.6 20.3 43.6 38.4

3.1 4.5 3.8 14.6

0.4 0.2 0.4 0.1

0.4 0.1 0.5 0.2

1.0 0.5 1.4 0.6

1.8 1.9 2.4 1.9

Source: Adapted from Przybylski and Eskin (1991). Key: DAG = diacylglycerols GG = galactosyldiglycerols, sum of mono and di-isomer LPC = lysophosphatidylcholine LPE = lysophosphatidylethanolamine PA = phosphatidic acid PC = phosphatidyl choline PE = phosphatidyl ethanolamine PI = phosphatidyl inositol PL = polar lipids PS = phosphatidyl serine

and phosphatidylethanolamines (PE) assist in the removal of non-hydratable phospholipids. Phosphatidylinositol (PI) and PA are considered to be non-hydratable phospholipids and are usually difficult to remove during degumming. Phosphoric acid is the most effective degumming agent in terms of reducing the levels of lysophosphatidylethanolamine. Use of acids for degumming also removes the majority of iron from the oil. It should be noted that in practice, canola oil phospholipids are reduced to below 0.1% using aqueous solutions of citric acid and water (Mag 1990). Lecithins, crude phospholipids obtained by degumming canola oil using only water, form more stable oil in water emulsions than lecithin obtained from degumming with the acids (Smiles et al. 1989). However, canola/rapeseed lecithins are not used in food applications, but are mainly utilized as an animal feed ingredient. Sosulski and co-workers (1981) and Smiles and co-workers (1988) examined the fatty acid composition of the individual phospholipids in the LEAR variety from winter rapeseed cultivars (Table 4.6). Phosphatidylcholine contained the highest amount of unsaturated fatty acids, mostly oleic and linoleic acids. The other two principal phospholipids were rich in palmitic, linoleic, and linolenic acids. The presence of highly unsaturated fatty acids in phospholipids is important, as these are prone to oxidation and can cause accelerated deterioration of the oil. It was also reported that phospholipids have a tendency to complex heavy metals and that these complexes stabilize catalysts, which can initiate and stimulate oxidation (Smouse 1994). The galactolipids and esterified phytosterol glycosides contain more unsaturated fatty acids, particularly palmitoleic, linoleic, and linolenic acids, than the phospholipids (Table 4.6). It would be interesting to establish how modifications of fatty acid composition in the seed oils affect the fatty acids in the phospholipids. In HEAR higher amounts of erucic acid are reflected in the higher contribution of this acid in the phospholipids, but especially in the galactolipids’ fatty acid composition.

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Table 4.6

115

Fatty acid composition of canola polar lipids (w/w %).

Polar lipid

16:0

16:1

16:3

17:0

18:0

18:1

18:2

18:3

20:1

PC PI PE MGDG DGMG SG

8.7 21.8 17.7 19.1 20.2 17.0

0.8 0.8 1.8 9.9 3.4 5.7

1.2 1.9 2.0 – trace –

– – – – 3.4 0.9

55.8 33.6 47.7 6.7 8.4 8.9

30.9 38.1 27.3 43.3 23.2 47.9

1.9 3.6 2.7 15.9 31.9 14.0

0.2 0.2 0.3 9.5 9.3 6.1

0.5 – 0.5 – – –

Source: Adapted from Sosulski et al. (1981) and Smiles et al. (1988). Key: DGDG = digalactosyldiglycerol MGDG = monogalactosyldiglycerol PC = phosphatidylcholine PE = phosphatidylethanolamine PI = phosphatidylinositol SG = esterified phytosterol glycoside

4.2.6

Tocopherols

The main components of unsaponifiables in vegetable oils are tocopherols and sterols, present in different amounts in vegetable oils. Tocopherols are known to be efficient natural antioxidants. Their amount in the plant is probably related to the content of unsaturated fatty acids. Canola oil contains relatively high levels of tocopherols, however their amount in the finished oil is affected by refining, mainly by the deodorization, which can reduce the amount by 50% (Cmolik et al. 2008). The different tocopherols have different antioxidant activity in vitro and in vivo. In the food system the antioxidant activity of the tocopherol isomers decreases in the order: δ>γ>β>α. However, this order is affected by oxidative degradation conditions and the environment (Kamal-Eldin and Appelqvist 1996). The tocopherols are about 250 times more effective than BHT (Burton and Ingold 1989). Lipid peroxy radicals react with tocopherols several orders of magnitude faster than with other lipids. A single molecule of tocopherol can protect about 103 to 106 molecules of polyunsaturated fatty acids in the living cell. This explains why the ratio of tocopherols to PUFA in the cells is usually 1:500 and still sufficient protection is provided (Patterson 1981). Though less potent than carotenoids, these components are also effective as singlet oxygen quenchers. A single molecule of tocopherol can react with up to 120 molecules of singlet oxygen (Bowry and Stocker 1993). The high potency of tocopherols as antioxidants and quenchers arises from their ability to be transformed from the oxidized form back into the active structure by molecules such as ascorbic acid and glutathione (Tapel 1968). Plastochromanol-8 is a derivative of γ-tocotrienol, which has a longer side chain. This compound was detected at elevated amounts in canola and flax oils and its antioxidative activity was established to be similar to α-tocopherol (Zambiazi 1997). The composition and the ranges of amounts of tocopherols in some common vegetable oils compared to canola oil are summarized in Table 4.7. Crude canola oil contains mostly α- and γ-tocopherol, with the amount of the latter usually twofold higher. The content of tocopherols in refined, bleached, and deodorized (RBD) oils is reduced by processing, mainly by deodorization (Cmolik et al. 2008). The lowest content of tocopherols was found in cold-pressed canola oil. When the temperature of pressing was increased, the amount of

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Table 4.7

Tocopherols content in selected crude vegetable oils (mg/kg). Tocopherol isomers (mg/kg) Alpha

Commodity oils* Canola 100–386 Soybean 9–352 Sunflower 403–935 Corn 23–573 HOSUN 400–1090

Beta

Gamma

Delta

P8

Total

0–140 0–36 0–45 0–356 10–35

189–753 89–2307 0–34 268–2468 37–709

0–22 154–932 0–7 23–75 0–19

10–85 – – – –

430–2680 600–3370 440–1520 330–3720 450–1120

Modified canola** LLCanola 150 HOCanola 226 HOLLCanola 286

– – –

314 202 607

7 3 8

47 42 83

517 473 983

Transgenic canola§ T2 488 T2’ 664 T2” 609 T3 610

– – – –

511 669 522 1010

18 104 20 163

17 16 69 66

1033 1453 1220 1849

Source: Adapted from * Codex Alimentarius (2010); ** Normand et al. (2001); § Raclaru et al. (2006). Note: Transgenic varieties of canola were selected to illustrate different tocopherols content and composition. Key: HOCanola = canola oil with high content of oleic acid LLCanola = canola oil with low content of linolenic acid P8 = plastochromanol-8

tocopherols in the oil doubled. Solvent-extracted oils contain about the same level of tocopherols as hot-pressed oils (Willner 1997). The amount and composition of tocopherol isomers in modified canola oils are affected by the selection process (Raclaru et al. 2006). By the manipulation of specific genes it was possible to increase the amounts of tocopherols in canola oil. Among developed genotypes, it was possible to equalize the amount of α- and γ-tocopherols, with a significant increase in δ-tocopherol contribution (Table 4.7). Developed varieties of canola oil with a lower amount of linolenic acid were usually selected based on fatty acid composition and the tocopherols were often neglected in this process (Table 4.7). Two low-linolenic canola oil varieties offered much less resistance to oxidation than regular canola oil, which was attributed to lower amounts of tocopherols (Normand et al. 2001). HOLL canola was developed with the tocopherols and fatty acid composition in mind, and provided an oil with excellent frying performance (Matthaus 2006).

4.2.7

Sterols

Sterols are present in canola oil as free and esterified sterols in similar amounts (Evershed et al. 1987). The fatty acid composition of the canola esterified sterols fraction is presented in Table 4.8. The fatty acid distribution differs from that of canola oil, in that the sterol esters contained higher levels of palmitic and stearic acids. In canola oil, sitosterol and campesterol are equally distributed in the esterified and free sterol fractions; however, twice the

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Table 4.8 Fatty acid composition of esterified sterols in canola oil. Fatty acid

Contribution (%)

14:0 16:0 18:0 18:1 18:2 18:3 20:0 22:1

Sterol esters

Canola oil

3.1 17.5 18.4 30.9 20.5 7.6 0.8 1.2

0.1 3.6 1.5 60.2 21.6 9.6 0.4 0.2

Source: Adapted from Gordon and Miller (1997).

Table 4.9

Composition and content of major sterols in selected vegetable oils (%).

Sterol Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Avenasterol Δ7-Stigmasterol

HEAR

CAN

LLCO

HOCO

HOLLCO

SOY

SUN

Corn

0.4 13.2 34.4 0.3 47.9 2.1 1.6 2.1

0.1 13.8 27.6 0.5 52.3 1.9 1.1 2.3

0.1 12.2 31.2 0.2 51.3 1.9 1.1 2.1

0.1 10.8 33.9 0.8 48.7 1.8 1.9 2.1

0.1 16.2 28.8 0.1 50.9 2.1 0.8 2.3

0.3 – 18.1 15.2 54.1 2.5 2.0 1.4

0.1 – 7.5 7.5 58.2 4.0 4.0 7.1

0.1 – 17.2 6.3 60.3 10.5 1.1 1.8

Total (g/kg)

8.8

6.9

6.3

7.1

6.9

4.6

4.1

9.7

Esterified (g/kg)

4.5

4.2

4.0

4.4

4.2

5.8

2.1

5.6

Source: Adapted from Ackman (1990), Strocchi (1987), Zambiazi (1997), and Gordon and Miller (1997). Note: For abbreviations see Table 4.2.

amount of brassicasterol was found as free sterols. The total amount of sterols in rapeseed and canola oils ranges from 0.7% to 1.8%. The composition of major sterols in common vegetable oils is presented in Table 4.9. Brassicasterol is a major sterol in rapeseed and canola oils and it is unique to brassica oils, often used to detect adulteration of other oils with rapeseed/canola oils (Ackman 1990). The amount of sterols in finished oil is affected by processing and often about 40% of these components is removed from the oil during deodorization (Rudzinska et al. 2005). Since the structure of phytosterols resembles that of cholesterol, these compounds may be involved in similar oxidative reactions (Rudzinska et al. 2005). Phytosterol oxidation products were found in rapeseed and soybean oils, wheat flour, infant formulas and fried products (Oehrl et al. 2001; Rudzinska et al. 2005; García-Latas et al. 2008). Because of the health concerns associated with cholesterol oxidation products, the potential health risks of phytosterol oxidation products are now receiving serious attention.

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Table 4.10

Chlorophyll pigments in canola oil during processing (mg/kg).

Oil after Expeller Extraction Expeller + extraction Degumming Alkaline refining Bleaching

Chlor a

Pheo a

Pheo b

Pyro a

Pyro b

6.27 1.88 1.79 0.27 0.22 –

4.48 3.31 5.55 7.16 6.27 0.56

1.79 1.34 1.34 1.07 1.12 0.32

5.37 16.57 9.76 9.40 9.13 0.21

0.67 3.13 1.43 1.84 1.79 0.25

Source: Adapted from Suzuki and Nishioka (1993). Key: Chlor a = chlorophyll a Pheo a = pheophytin a Pheo b = pheophytin b Pyro a = pyropheophytin a Pyro b = pyropheophytin b

Phytosterol oxides are mutagenic, a source of free radicals, affect cell viability, stimulate inflammation, cause oxidative changes in the retina, and affect hormonal activity, among other effects (Javitt 2008; Hovenkamp et al. 2008). Oxidized phytosterols affect metabolic processes and cell viability similarly to cholesterol oxides; however, due to the lower absorption rate of these components, higher amounts are required to detect outcome (Ryan et al. 2005).

4.2.8

Pigments

Pigments present in canola cause an undesirable color in the oil. They promote photo-oxidation as well, inhibiting the catalysts used for hydrogenation. Chlorophylls without phytol, such as chlorophyllides and pheophorbides, may have nutritional effects because of their photo-toxicity, which may be followed by photosensitive dermatitis (Endo et al. 1992). A bleaching step is necessary during oil processing to remove chlorophyll, chlorophyll derivatives, and other color bodies. Changes in chlorophylls during canola oil processing are summarized in Table 4.10. During processing chlorophyll completely decomposes to derivatives that are more difficult to remove during bleaching. This necessitates the use of higher amounts of activated bleaching earth to achieve complete removal of all chlorophyll derivatives (Suzuki and Nishioka 1993). The type and content of chlorophylls and their derivatives in the seed are the main factors defining the quality of extracted canola oil, and have an effect on the quality of the processed oil. The composition and content of these pigments are related to the maturity of the seed (Table 4.11). In fully matured seed, the amount of chlorophylls at 4 mg/kg was observed, while in physiologically matured seed, 35 days before full maturity, an amount of 1239 mg/kg was found. At maturity, only chlorophyll a and b were present, while all possible isomers/derivatives were observed at other stages of seed maturation (Table 4.11). In addition to chlorophyll pigments, carotenoids were also found in canola oil. The content of carotenoids in crude canola oil was reported to be at 130 ppm, with 90% xanthophylls and 10% carotenes. During refining and bleaching, the amount of carotenoids is reduced to 10 ppm (Cmolik et al. 2000).

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Table 4.11 (mg/kg).

119

Changes in composition and content of chlorophylls during canola seed maturation

Time to maturity (days) Chlorophylls Chlorophyll a Chlorophyll b Pheophytin a Pheophytin b Pheophorbides a Pyropheophytin Methylpheophorbide Total amount (mg/kg)

35 19.5 22.2 43.1 8.5 2.2 1.2 3.2 1239

27 23.4 22.1 39.8 7.4 1.7 2.3 3.5 906

20 27.2 15.8 40.9 11.3 0.6 2.5 1.8 463

14 58.7 27.3 10.1 2.0 1.5 0.0 0.5 48

6 41.9 54.1 1.1 0.0 0.0 0.0 3.0

0 82.4 17.1 0.0 0.0 0.0 0.0 0.5

8

4

Source: Adapted from Ward et al. (1994).

4.2.9

Trace elements

The Codex Alimentarius standard for edible low-erucic acid rapeseed gives the maximum levels permitted for iron, copper, lead, and arsenic. While these metals are found in other edible oils and are present naturally in the seed, nevertheless further quantities can be introduced during handling and processing. Diosady and co-workers (1983) examined the effect of processing on trace elements in canola oils. It is evident from the data in Table 4.12 that processing reduces the amount of toxic and damaging trace elements, particularly lead, iron, and sulfur. Phosphorus and calcium form salts that are insoluble in the oil and are removed during the degumming process. Sulfur in canola oil is in the form of organic compounds as the decomposition products of glucosinolates. Although these sulfur components occur in trace quantities, they poison the catalysts used for hydrogenation as well as giving a characteristic odor to the oil. Recent developments in analytical methods for sulfur determination have revealed that soybean, sunflower, and even coconut oils also contain sulfur at the level of 2–10 mg/kg. Only Brassica oils contain significant quantities of divalent sulfur components. Crude canola oils may contain 15–35 mg/kg of sulfur, while in RBD canola oils the amount of sulfur compounds is reduced to 9 mg/kg or lower (Wijesundera et al. 1988). Sulfur components may improve the stability of the oil. Some of these components can act as antioxidants and protect the oil from autoxidation by complexing hydroperoxy radicals with the sulfur to form stable compounds. These compounds can also inactivate catalysts involved in oxidative processes, such as metals (Barnard et al. 1958).

4.2.10 Commercial crude oil, refined, and deodorized oil The typical composition of Canadian crude, refined, and deodorized canola oils is presented in Table 4.13. The data for deodorized oil represents the typical quality of oil used as a food ingredient. The values for crude oil compare closely with those of other commercial oils, such as soybean oil, produced according to good processing practice. An exception is the presence of chlorophylls and sulfur compounds, which can be higher in canola oil than in most commodity oils. The parameters for deodorized oil reflect good refining practice and are similar to the data obtained with other deodorized commodity oils processed for food applications.

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Table 4.12

Content of mineral elements in canola oils (mg/kg).

Oil sample

Phosphorus

Crude oil Degummed with Water (WDG) Phosphoric acid (PDG) Bleached WDG PDG Deodorized WDG PDG

Iron

Calcium

Sulfur

Zinc

Lead

1190.0

3.52

296.0

6.5

2.4

0.24

222.0 117.2

1.32 0.63

169.0 34.8

1.2 1.5

2.1 –

– –

0.21 0.19

0.23 0.59

5.6 4.1

– 0.87

– –

– –

0.25 0.22

– –

0.25 0.38

– –

0.07 –

– –

Source: Adapted from Diosady et al. (1983), Elson et al. (1979), and Ying et al. (1989).

Table 4.13 Typical chemical analysis data of crude and refined, bleached, and deodorized (RBD) canola oil. Parameter

Crude oil

RBD

Free fatty acids, % Phosphorus, mg/kg Water degummed Acid-water degummed Chlorophyll, mg/kg Sulfur, mg/kg Iron, mg/kg Copper, mg/kg Nickel, mg/kg Peroxide value, mg/kg Anisidine value Color, Lovibond Moisture, % Flavor

0.3–1.2 300–500 120–200 10–40 4–30 2–15 0.5–1.5 <0.2 – 0.5–3.0 1–3 – <0.3 –

0.03 <2 – – <0.025 <1 <0.2 <0.02 <0.3 0 (freshly deodorized) <2 <1.5 Red/10 Yellow – bland

Source: Adapted from Mag (1990).

4.2.11 Oxidative stability The stability of canola oil is affected by the presence of linolenic acid, chlorophyll and its decomposition products, and other minor components. The latter usually are components with high chemical reactivity, such as trace amounts of fatty acids containing more than three double bonds, often formed during refining and bleaching (Chapman et al. 1994). The presence of 7–11% of linolenic acid in the triacylglycerols of canola oil places it in a similar category to soybean oil with respect to flavor and oxidative stability. The deterioration of flavor as the result of auto- and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. The solubility of oxygen in oil is about 3–5 times greater than in water. The amount of oxygen present in the oil, dissolved during manipulation, is sufficient to oxidize it to a peroxide value of around 10 (Przybylski and Eskin 1988). The rate of oxidation of fats and oils

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Table 4.14

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Some physical properties of canola oil.

Parameter

Relative density (g/cm3; 20 °C/water at 20 °C) Refractive index (nD 40 °C) Crismer value Viscosity (Kinematic at 20 °C, mm2/sec) Cold test (15 hrs at 4 °C) Smoke point (°C) Flash point, open cup (°C) Specific heat (J/g at 20 °C) Saponification number Iodine value

Value Canola

HEAR

0.914–0.917 1.465–1.467 67–70 78.2 Passed 220–230 275–290 1.910–1.916 188–192 110–126

0.907–0.911 1.465–1.469 80–82 84.6 Passed 226–234 278–282 1.900–1.911 168–181 97–108

Key: HEAR = high erucic acid rapeseed oil

is affected by the oxygen partial pressure, access of oxygen, the degree of unsaturation of fatty acids, and the presence of light, heat, antioxidants, and pro-oxidants such as copper, iron, and pigments. The best stability of oil was achieved when the presence of iron and copper was below 0.1 and 0.02 ppm, respectively (Smouse 1994). The degradation of oils and fats due to light exposure is primarily a photo-catalyzed oxidation. During photo-oxidation, singlet oxygen is generated by the transformation of light energy to a sensitizer that activates oxygen. Singlet oxygen is an extremely reactive specie of oxygen, 1500 times more reactive than ground-state oxygen, which reacts with double bonds of unsaturated fatty acids to form peroxides and/or free radicals. Typical photosensitizers are chlorophylls and their decomposition products present in seed and formed during processing, heme compounds, and polycyclic aromatic hydrocarbons (Smouse 1994). It has been found that chlorophyll degradation products are more effective as photosensitizers than chlorophyll itself (Usuki et al. 1984).

4.3

PHYSICAL AND CHEMICAL PROPERTIES

The properties of canola oil are governed by components present in the oil and described by the general parameters for vegetable fats and oils. Selected physical properties for canola oil in comparison to HEAR oil are shown in Table 4.14.

4.3.1

Relative density

Typical values for the specific gravity of canola oil are presented in Table 4.14. Ackman and Eaton (1977) indicated that a different ratio between eicosenoic (20:1) and C18 polyunsaturated fatty acids could be a major factor in changing the relative density of canola oil. Noureddini and co-workers (1992) described the relationship between the temperature and the density of vegetable oils, including canola. As for other liquids, the density for vegetable oils is temperature dependent and decreases in value when the

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temperature increases. The same authors also developed an equation to calculate density from the fatty acids composition.

4.3.2

Viscosity

Viscosity measures relative thickness or resistance of oil to flow. The viscosity of refined, bleached, and deodorized (RBD) canola oil is higher than for soybean oil. Kim et al. (2010) and Fasina and Colley (2008) correlated the viscosity of canola and other vegetable oils with temperature. They also derived an equation to calculate viscosity as related to temperature and fatty acid composition. The viscosity of HEAR oil is significantly higher than that of canola oil.

4.3.3

Smoke and flash point

The smoke point is the temperature at which a fat or oil produces a continuous wisp of smoke. This provides a useful indicator of its suitability for frying and a temperature of 200 °C is often specified as the minimum by regulation (Table 4.14). The flash point defines the temperature at which the decomposition products formed in heated frying oils can be ignited. This temperature usually ranges from 275 °C to 330 °C for different oils and fats (Table 4.14). An increase in the content of unsaturated fatty acids usually causes a decrease in the flash and smoke points (Arens et al. 1977).

4.3.4

Cold test

The cold test measures the resistance of oil to the formation of sediment at 0 °C or 4 °C (Table 4.14). Sediment formation is usually caused by compounds with a high melting point. These are mainly waxes and triacylglycerols with long-chain saturated fatty acids and alcohols (Przybylski et al. 1993a). The formation of haze in canola oil is not common, but may occur occasionally (Mag 1990). Oils produced from seeds grown in dry/drought conditions develop sedimentation more easily, and this may be related to the higher content of longchain saturated fatty acids and alcohols formed as a response to drought stress conditions (Przybylski et al. 1993a).

4.3.5

Crismer value

The Crismer value (CV) measures the miscibility of an oil in a standard solvent mixture, composed of tert-amyl alcohol, ethyl alcohol, and water in volume proportion 5:5:0.27 (Table 4.14). Values are generally characteristic, within a narrow limit, for each kind of oil. This parameter was a specification criterion used for international trade, mostly in Europe; however, it is rarely used today. The miscibility of oil is related to the solubility of the glycerol esters and is affected mainly by the unsaturation and chain length of the constituent fatty acids.

4.3.6

Saponification number

The saponification number is defined as the weight of potassium hydroxide, in milligrams, needed to saponify one gram of fat. This parameter is inversely proportional to the molecular weight of the fat. In other words, the higher the molecular weight, the lower the

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saponification value. Replacement of long-chain fatty acids such as erucic acid in rapeseed oil by C18 fatty acids increases the saponification numbers from 168–181 to 188–192 due to the reduction in molecular weight (Table 4.14).

4.3.7

Iodine value

The iodine value (IV) indicates the degree of unsaturation of a fat or oil. It is defined as the number of grams of iodine absorbed by 100 grams of fat. The higher value for canola oil is due in part to the replacement of erucic acid with unsaturated C18 acids, mainly oleic acid, together with a slight increase in the contribution of linoleic and linolenic acids (Table 4.14). Currently, the iodine value is calculated from fatty acid composition using specific factors for each unsaturated fatty acid (Kyriakidis and Katsiloulis 2000). The calculation of the iodine value provides more accurate data, eliminating the unsaturation present in unsaponifiable compounds.

4.3.8

Melting characteristics, polymorphism, and crystal properties

Canola oil has a homogeneous chain-length fatty acid composition, with 95% being contributed by C18 fatty acids (Ackman 1990). Reducing the erucic acid content has a marked effect on the melting characteristics and the type of crystal formed when the oil is hydrogenated. Hydrogenation of canola oil is used to form products used in the formulation of shortenings and margarines. However, negative health issues related to trans fatty acids caused elimination of this process from fats processing for food use. With an increasing degree of hydrogenation, the fatty acid composition becomes more homogeneous. This results in a tendency to form β-crystals on solidification, which are undesirable in margarine and shortenings. Trans isomers formed in hydrogenation have higher melting points than cis fatty acids and provide greater variety in the fatty acid composition of the hydrogenated oils, which have β′-crystallization tendency, reducing the β-crystallization.

4.4 4.4.1

MAJOR FOOD USES Standard canola/rapeseed oil

Canadian canola oil processors probably have the most experience in managing it as a food ingredient. Canola/LEAR was originally developed and introduced commercially in Canada, and considerable experience in using canola oil in edible applications has been accumulated. Usage of canola oil in Canada has grown from the early years after its introduction to about 76% of the edible vegetable oil consumed in 2009 (Canadian Oilseed Processors’ Association). About 65% of produced oil is exported from Canada and most of it is used as liquid oil. The products in which the liquid oil is used are salad oils and salad dressings, soft and hard margarine formulations, and household and baking shortenings. Changes in labeling regulations have altered completely the formulation of margarines, shortenings and baking margarines, and frying fats. Producers and formulators are required to eliminate hydrogenated fats, the major carrier of trans fatty acids, to be able to utilize the claim ‘zero trans product’.

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4.4.1.1

Cold-pressed canola oils

Cold-pressed or virgin oils are primarily produced from a variety of oilseeds and olives, and have been so as long as mankind has used oils in food preparation and as a component of diet. A new interest in virgin oils beyond olive oil has arisen as part of consumer interest in organic and natural foods. This segment of oils is developing much faster in Europe than in North America. Virgin oils are an important part of the fast-growing organic food market. The return to cold-pressed oils is driven mainly by changes in nutritional trends and consumer perception of natural foods as being more nutritious, less ‘polluted’, and of better quality. Today’s consumers are more educated and are tired of the continuous bombardment of information about health-related problems found in processed foods. Virgin oils offer economic advantages for producers of oilseeds and processors, because these products are higher priced and have higher added value. The production of virgin oils is usually performed in small operations with simple processing involving only pressing and purification by filtration to remove solids. With this simple system processors do not have many options to ‘correct’ the quality of the product produced and are totally dependent on the quality of the processed oilseeds. Germany is probably the most advanced producer of canola-type cold-pressed oil and plenty of research has been done to establish factors affecting the quality of the oilseeds. Canola cold-pressed oil has many problems related to flavor, linked to the maturity and storage conditions of seeds. Canola seed contains 42% of oil, which is the best solvent/carrier for flavor components and is working as a ‘flavor memory’, where whatever happen to the seed will be stored in the form of a ‘specific flavor fingerprint’. These flavor components will be transferred into the oil and affect its quality and perception (Matthaus and Bruhl 2008). The authors concluded that the production of good-quality virgin canola oil is dictated only by the quality of the seeds used for processing. Despite these problems, the canola virgin oil market in some European countries is growing fast. The North American market for canola virgin oil is non-existent, mainly due to the lack of a tradition of using this oil. 4.4.1.2

Salad oil, salad dressings, mayonnaises, and cooking oil uses

Canola oil is a ‘natural’ salad oil, which remains transparent at refrigeration temperatures. Oil isolated directly from the seed does not need ‘winterization’ or fractionation. However, winterization is applied to provide clarity, particularly when dry conditions occur during the growing season, and canola has a tendency to accumulate more long-chain fatty acids in triacylglycerols and waxes (see Section 4.3.4). These compounds usually initiate crystallization over time, particularly at refrigeration temperatures, and create haziness, which leads to appearance problems in the transparent bottles that are normally used. Canadian consumers rarely complain about haziness and winterization is applied for the most demanding markets. These compounds do not present a health hazard and are usually present at too low a concentration to affect emulsion stability when the oil is used in mayonnaise, emulsified salad dressings, and margarines. Canola oil is used alone as a principal ingredient in salad oil blends. Nutritional value and utilization of potential health claims related to canola oil are the main reason for blending, where other oils are used to improve fatty acid composition or add specific nutraceutical components. Enrichment of canola oil with long-chain PUFA such as EPA and DHA is a good example of blends available on the market. Canola oil contributes low amounts of

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saturated fat, useful levels of essential fatty acids such as linoleic and linolenic acid, and nutraceuticals, including tocopherols and sterols. Canola oil is used as cooking oil, for pan frying, and as a household deep-fat frying medium. Industrial frying operations in Canada often use regular canola oil for par-frying of different types of food products; however, it is rarely used in institutional frying. Industrial frying usually has well-controlled frying conditions and a high turnover of oil, which protects the frying medium from extensive oxidation. Conditions are different in institutional frying, where the oil is used as long as possible and often the frying temperature is not properly controlled. We established that frying temperature is the crucial parameter accounting for the oxidative degradation of frying oil (Aladedunye and Przybylski 2009). In all these applications, canola oil gained market share in the 1980s and 1990s in many areas of the world, such as North and South America and many European and Asian countries. The main factors driving popularity are the lowest content of saturated fat among all commodity oils; the high content of oleic acid; the moderate amount of linoleic acid; and the good amount of linolenic acid. All three unsaturated fatty acids when consumed at proper proportions positively affect human blood lipids (Barth 2009). In major commodity oils such as soybean, corn, and sunflower, the contribution of linoleic acid is very high and causes high ratios of n-6 to n-3 fatty acids. It is well recognized that overload with n-6 acids causes imbalance in metabolites, which negatively affects human body metabolism and function (Simopoulos 2008). The lower amounts of PUFA in canola oil (30% vs. 60% for soybean oil) along with the high content of monounsaturates (60% vs. 25% for soybean oil) are the main factors defining good flavor stability, despite the presence of linolenic acid (Table 4.2). Additional minor attributes important in improving canola oil stability are: ●

●

placement of linolenic acid mainly in the sn-2 position in the triacylglycerols, which partially protects this acid from oxidative degradation; sulfur compounds generally perceived as negatively affecting processing, which may act as antioxidants (see Section 4.2).

4.4.1.3

Frying fats

Nutritional quality is the main factor driving the development of a new generation of frying fats, where oxidative stability and the amount of saturated fats are the most important factors. Frying oils are selected by food services applying the following criteria: (i) flavor; (ii) texture; (iii) mouth feel; (iv) stability (i.e., fry-life of the oil/fat); (v) cost; (vi) availability; and (vii) minimizing the content of trans fatty acids (TFA) (Matthaus 2006). Labeling regulations have enforced a change of view on the utilization of hydrogenated oils for frying fats. The negative health effects of trans fats were known for a long time before new labeling regulations were implemented, but the vegetable oil industry resisted placing trans fats as a separate item on food labels. For frying applications, new canola-type oils have been developed to replace transcontaining fats. New canola frying oils still contain the lowest amount of saturated fats, while the main changes are in increasing oleic acid and decreasing linolenic acid content to below 3% (Table 4.2: LLCO, HOCO, HOLLCO). Under controlled conditions, the frying performance of the typical frying shortenings and new trait oils has been compared. The results verified the good frying stability of HOLLCO oil, specifically designed for frying. This oil produced the lowest amount of polar components, the best indicator of frying stability, and performed better than standard hydrogenated

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Polar components (%)

24 21 18 15 12 HOLLCO HYDCO HYDSOY LLCO HOLLSOY

9 6 3 0 0

1

2

3

4

5

6

7

8

9

10

11

Frying time (days) Figure 4.1 Frying performance of trait oils and hydrogenated frying shortenings as measured by the formation of polar components. Note: For fatty acid composition of oils see Table 4.2. Key: HOLLCO = high oleic low linolenic canola HYDCO = pourable hydrogenated canola frying shortening HOLLSOY = high oleic low linolenic soybean HYDSOY = pourable hydrogenated soybean frying shortening LLCO = low linolenic canola oil

frying fats (Figure 4.1). The main disadvantage of hydrogenated frying shortenings is their high content of trans isomers, usually at 20% to 35%, and high amounts in saturated fatty acids, at 10% to 20%. HOLLCO also performed better than other trait oils designed for frying, such as mid-oleic and high-oleic sunflower and palm olein when directly compared (Figure 4.2). The superior frying stability of HOLLCO was confirmed during frying of French fries, where the fried produced have similar sensory quality to the high-oleic sunflower oil (HOSUN) used in Europe as a reference frying oil (Matthaus 2006). The previous oil offers nutritional advantages related to (i) the low content of saturated fat; (ii) the presence of omega-3 fatty acids even at lowered amounts, as this essential fatty acid positively affects human body metabolism; (iii) the absence of trans fatty acids; (iv) high amounts of oleic acid, which is neutral to blood lipids with a tendency to increase the amount of highdensity lipoprotein (HDL); and (v) the fact that even at the lower content of linolenic acid, the ratio of omega-6 to omega-3 at 7.5 is still close to optimal (Barth 2009). The same oil was applied to frying donuts and potato chips. For both products sensory quality and other indicators were comparable to standard frying fats containing trans fatty acids. However, the storage stability of these products was slightly reduced, mainly due to the higher amounts of PUFA. Nevertheless, HOLLCO can be a good alternative to hydrogenated frying fats to reduce or to eliminate trans isomers from fried foods (Matthaus et al.

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25

Polar components (%)

20

15

10 MOSUN HOLLCO HOSUN PALM OLEIN

5

0 0

1

2

3

4

5

6

Frying time (days) Figure 4.2 Frying performance of trait oils as measured by the formation of polar components. Key: HOLLCO = high oleic low linolenic canola HOSUN = high oleic sunflower MOSUN = mid-oleic sunflower PALM OLEIN = palm oil olein fraction

2009). HOLLCO is a trans-free replacement for partially hydrogenated frying fats where resistance to oxidative degradation and extended shelf-life are required. Currently this oil is used in the following applications: snack and grill frying; food service frying; pan sprays; spray oil coatings; bakery shortenings and margarines; nutritional bars; sauces and dressings; and blends with other oils in frying applications. Alternatives to the hydrogenated commodity oils and trait oils discussed above are blends of different oils and fats to provide frying stability and good-quality fried products. These blends often contain HOLLCO as a component (e.g., HOLLCO/corn oil blend), and are mainly prepared to reduce cost. Blended corn oil or cottonseed oil with traditional soybean oil or canola oil can be targeted to attain a linolenic contribution below 3%. Frying tests demonstrated that blends produced good-tasting fried foods and maintained good-quality oil in the fryer. Naturally stable oils are used in blends to eliminate trans fats, but at the same time the amount of saturated fats is elevated to the multiple amounts present in HOLLCO. 4.4.1.4

Soft (tub) margarine

In Canada and many other countries in which margarine is consumed, soft or tub margarine is now predominant. Consumption of hard (stick) margarine has decreased significantly in the past two decades. Furthermore, a significant proportion of soft margarines in many countries does not contain trans isomers and hydrogenated oil. Palm/palmkernel oil-based hard fat blends at 6–10% with a suitable solid fat content profile are used to provide the β′-crystalline structure. The composition of the palm/palmkernel oil-based

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hard fats varies depending on several factors and is very often proprietary to the suppliers, which are primarily based in Malaysia. Interesterification is usually used to produce these blends. Canola oil is used mainly as the liquid oil in trans-free products such as Becel, a soft margarine offered mainly in Europe and Canada for many years. Canola oil is often the preferred liquid oil, because it has the lowest saturated fatty acid content and supplies some linolenic acid, yet has good flavor stability. The oil is also used together with other liquid oils to make up the liquid phase component. In the past, margarine fats/oils were made entirely from canola oil, especially in Canada and Sweden, driven mainly by cost or oil availability. Currently, partially hydrogenated oils are rarely used due to the trans issue and the market perception of hydrogenated ingredients. The required hard stock for margarine formulation is produced by full hydrogenation of canola oil and oils containing high amounts of palmitic acid, such as cottonseed oil or tropical oils. To make oils that will be used in margarine formulation with a low content of solid fats and to eliminate trans isomers, interesterification with trait liquid oil is applied. Changing the fatty acid position in triacylglycerols of hard stock reduces the β-crystallization tendency. All the measures to control β-crystallization and to reduce trans content cost more and label declaration of fully hydrogenated fats used as ingredients is required, giving the product an undesirable connotation. In today’s practice, blending with another hard fat relatively high in palmitic acid to raise the concentration of this acid to at least 8% in the hard fat blend is preferred. To meet this requirement, the oils used are palm at about 15% and fully hydrogenated cottonseed. 4.4.1.5

Hard (stick) margarines

Liquid, fully hydrogenated canola and high-palmitic oils are used to produce stick margarine. The tendency of the fully hydrogenated canola oil to crystallize in β form limits the utilization of this fat as the only ingredient in margarine formulation, because these fats must be used in relatively large amounts, 40–50% in the fat blend, which makes it difficult and costly to control β-crystallization. In situations where the use of canola oil must be maximized, the same approach as outlined for soft margarine must be used. As has already been pointed out, the demand for stick margarine is declining, and the demand for margarine made entirely from canola oil is no longer significant in most countries that are accustomed to the use of canola oil. 4.4.1.6

Shortenings, baking and pastry margarine

Similar to the use of canola oil in making table margarine, liquid canola oil is heavily used to produce shortening, baking, and pastry margarines. Again due to consumer demand, partially hydrogenated fats cannot be used. A similar approach as discussed for margarines is applied: mixtures of fully hydrogenated fats from canola oil and oils with a high content of palmitic acid are used to control crystallization. Interesterification is often applied to make fats with acceptable solid fat content and profile to support particular applications. Liquid canola oil is blended with hard fats such as tallow, palm, and fully hydrogenated soybean, canola, palm, and cottonseed oils (stearins), to meet preferred specifications. Detailed compositions are usually proprietary. For baking applications, shortening, and baking margarine, having the fat component with the β′-crystalline form is especially important for good performance. For this reason, baking shortenings based totally on canola oil are not used.

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Antioxidant usage in canola oil products

Present practice is to avoid the use of synthetic antioxidants in edible oil products as much as possible. This also applies to canola oil products. For many edible oil products, users now specify that chemical additives cannot be used as ingredients. This avoids having to declare on the product label that the product contains a synthetic chemical antioxidant as an additive. Instead, there is an increasing emphasis on preserving the natural antioxidants, mainly tocopherols, present in canola oil, during processing. Tocopherol losses occur primarily during deodorization because of the high temperatures applied. Processors are limiting deodorizing temperatures as much as possible when high tocopherol concentrations are demanded, consistent with achieving good deodorization. It is possible to retain as much as 80% of the original tocopherol content in the deodorized oil. The tocopherols are especially important as antioxidants in frying, because of their low rate of evaporation and of destruction at frying temperatures (Pongracz 1988). The tocopherol content of standard canola oil is given in Table 4.6, together with the tocopherol content of some speciality canola oils and other common vegetable oils. The main tocopherols present in canola oil are α- and γ-tocopherols. It is interesting to note that canola oil is more than twice as high in α-tocopherol (about 270 mg/kg) than soybean oil (about 116 mg/kg). α-Tocopherol is recognized as the tocopherol with the highest vitamin E activity among all tocopherol isomers in humans (National Academy of Sciences 2000). Canola oil is thus a very good source of vitamin E. The synthetic antioxidants that are used, when there are no restrictions on using them, are butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tertiary butylhydroquinone (TBHQ). Added amounts are usually 0.02% (single or combined). This is the maximum allowable amount in Canada and the US, for example. Regulations governing synthetic antioxidant usage differ from country to country. Citric acid is used as a metal chelating agent, usually as monoacylglycerol citrate at 0.01% by itself or along with BHA and BHT. In some countries, the US for example, citric acid can be used as a chelating agent without having to declare it on product labels when it is added to the oil in an aqueous solution in the cooling stage of the deodorization process. Lower amounts of 0.005% are often used. It is good practice to add additives and antioxidants to oil at the cooling stage of the deodorization to ensure proper solubility and distribution. 4.4.1.8

Canola oil use in selected areas of the world

It is interesting to briefly review the use of canola oil in edible applications in the different parts of the world. The US imports large amounts of canola oil from Canada in addition to some domestic production. Currently, about 90% of the canola oil is consumed in liquid form as salad oil and in salad dressings. This is a direct result of the emphasis on consuming oils that are low in saturated fatty acids; canola oil is the lowest in saturated fat among commodity vegetable oils. Canola oil is also being used in blended salad oils to achieve certain fatty acid profiles, as mentioned earlier. The relatively high use of canola oil in the US is remarkable, since none was used before 1983. About 10% of canola oil is used as hydrogenated oil and consumed in the form of shortening. This appears to be mostly as frying fats (also termed frying shortenings in North America) to take advantage of the low concentration of saturated fat and low PUFA, as

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discussed before. Interestingly, small amounts of canola oil, liquid or hydrogenated, are used in margarine formulation. Mexico uses significant amounts of canola oil, predominantly in salad dressings or as a salad or cooking oil. This is mostly from seed imported from Canada and the European Union. Japan uses large amounts of canola oil. It has imported Canadian canola seeds since the introduction of canola in the early 1970s, and has for many years taken about half of the Canadian canola crop. The oil is predominantly used in liquid, non-hydrogenated form as cooking oil and as salad and salad dressing oils, both pure and in blends with other oils. In a new development, it is used as base oil to produce diet cooking and salad oils made up of about 80% diacylglycerols (DAG oil). DAG oil is differently metabolized in the digestive system and is mainly used as an immediate energy source rather than stored as body fat. This DAG oil technology is being introduced in the US (Anonymous 2001b). In China, canola-type rapeseed oil products still contribute a very small proportion of total rapeseed oil production. High-erucic acid rapeseed oil represents the largest portion of edible oil utilized for food applications at present, mainly used as cooking oil, with very little amounts used for margarine or shortening formulations. Efforts are being made to widen the spectrum of edible oil products and to convert from HEAR to canola cultivation. India, like China, does not use significant amounts of canola/rapeseed oil. Instead, mustard seed oil, which is high in erucic acid, similar to HEAR oil, is the most important oil used almost entirely as liquid cooking oil. Among the lower-income segment of the population, and even in the middle class, this oil is not deodorized and is favored for its taste. Undeodorized canola/rapeseed oil cannot compete with mustard seed oil in flavour. Blending of canola oil with mustard oil lowers the content of erucic acid in the mustard oil. Unless taste preferences change and there is greater attention to the health implications of the types of fat in the diet, canola oil will be used only to a limited extent in the foreseeable future. The Middle East is beginning to use canola oil in competition with sunflower and corn oil as salad and salad dressing and mayonnaise oil. In many countries at present margarine and vanaspati are based on hydrogenated soybean and palm oils. Interest in canola oil is based on its nutritional properties, mainly its low saturated and essential fatty acid content. There is considerable potential for using canola trait oil as a vanaspati-like frying fat. Western and Eastern Europe use large amounts of canola oil, with the exception of France. Large amounts of liquid canola oil are used in salad oils, salad dressings, mayonnaise, and table and baking margarines. Canola oil use is driven, in part, by recognition of the positive health effects of its high oleic acid content, along with its low saturated fat, and the fact that European-grown canola seeds are not genetically modified (non-GM) at present, as opposed to oil from imported soybeans. Also, canola salad oil is considered by some to have a better shelf-life than the other, more highly polyunsaturated vegetable oils. This part of Europe is the place where production of virgin canola oil is fast developing, as discussed above. Southern Europe and France use relatively little canola oil. Instead, olive, sunflower, and peanut oils predominate. In the case of France this is somewhat surprising, since this country is a large producer of canola seeds. France uses large amounts of canola oil for biodiesel production. Australia and New Zealand produce canola seed and use the oil in much the same fashion as North America and parts of Europe. South America uses sunflower and soybean oil and increasingly also palm oil. Canola oil is not a factor in food uses.

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Canola/rapeseed oils with modified fatty acid composition

Since the introduction of standard canola, plant breeders have made considerable efforts to develop canola oils with modified fatty acid compositions. The focus was directed t improving oxidative stability, or at controlling crystallization in solid fats by increasing the content of lauric acid, and, more recently, at developing canola oil containing unique fatty acids such as γ-linolenic and stearidonic. This is a list of these developments: ● ● ● ● ● ● ● ● ●

low-linolenic acid canola oil (2% vs. 9%); high-oleic acid canola oil (69–77% vs. 60%); high-oleic low-linolenic canola oil; high-palmitic acid canola oil (10% vs. 4%); high-stearic acid canola oil (30% vs. 2%); lauric acid canola oil (about 33% 12:0); γ-linolenic acid canola oil (up to 37%); canola oil with stearidonic acid and long-chain PUFA; low-saturated canola oil.

The complete fatty acid compositions of some of these oils, namely low-linolenic, higholeic acid, lauric acid, and γ-linolenic acid oils, are given in Table 4.2. Low-linolenic acid canola oil was developed in Canada in the 1980s to improve the oxidative stability of the oil so that light hydrogenation would be unnecessary. The linolenic acid content of this oil is reduced to about 2% compared to 9% in the standard canola oil. This resulted in an increase in linoleic acid from 20% to 27% and an increase in oleic acid from about 58% to above 60%. In Canada and the US, this oil is available in limited quantities and is used entirely for deep frying in place of the lightly hydrogenated standard canola oil. Its main advantage is the much lower trans isomer contents of about 1–3%, formed during deodorization, while the lightly hydrogenated oil contains 20–25%. Widespread use is hampered by its price, which tends to be too high due to the low seed yields of the available varieties. Research on its frying stability and the storage stability of French fries by Warner and Mounts (1993) showed that these properties were improved. Work done by Przybylski et al. (1993b), Zambiazi (1997), and Normand et al. (2001) showed only slight improvement in the frying stability of this oil and the storage stability of fried foods. This unexpected result may be related to the lower content of tocopherols. There are also anecdotal reports from industry that the frying stability of the oil is not sufficiently improved to warrant its higher price. High-oleic acid canola oil is another development pursued in Canada, the US, Sweden, Australia, and elsewhere. As with low-linolenic acid canola oil, the aim was to produce a stable frying oil, which will not need hydrogenation and thus avoid the formation of trans isomers. The oleic acid content in oil from seed developed in Canada is at about 72%, while linoleic acid content is 18% and linolenic acid is reduced to below 3%. Saturated fatty acid content is unchanged from standard canola oil. This oil is the main frying medium today in the US, Canadian, and some Asian markets due to its excellent performance, as discussed above. In Australia, canola oil with 69% oleic acid (Monola) is being offered for frying. In potato frying tests with ten other oils it was rated higher in sensory and chemical tests than the other oils (Anonymous 2000). High-palmitic acid canola oil was initially developed in Sweden. The purpose was to prevent the β-crystallization of hydrogenated canola oil to make it more freely useable for

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margarine and shortenings. The oil contains about 10–12% palmitic acid compared to only 4% in the standard oil. This development has not gained significant commercial use because of the increased use of canola oil in liquid form in a large variety of edible fat products, following concerns about saturated fatty acids, and because of the ready availability of palmitic acid-containing oils for blending to control crystallization problems. High-stearic acid canola oil with 25–30% stearic acid has been developed, but commercialscale production for food uses has not been achieved. High-lauric acid canola oil was developed in the US as a replacement for coconut and palmkernel oils for both food and non-food uses. The oil contains about 35% lauric acid, but up until now it has not found significant commercial use. The main reason for the lack of acceptance is the significantly different fatty acid composition compared to coconut oil and the consequent difference in performance in typical coconut oil applications. Some use was made of the oil in the US as a base stock for trans-free margarine formulations and in Europe as a machine oil additive (Anonymous 2001a), but currently a market amount of seed is no longer produced. All these canola oils with an elevated saturated fatty acid content suffer from common agronomical problems such as low yield and issues with seed development. γ-Linoleic acid canola oil is of interest from a nutraceutical point of view. Early varieties of canola oil contained up to 2% of this fatty acid; however, during the development of new varieties its presence was eliminated. This type of oil is an example of a new generation of nutraceutical oils aiming at the supplement market, with a potential application for nutraceutical food products. Stearidonic and LCPUFA-containing canola oils are under development. These oils are mainly aimed at the nutraceutical market to replace the dwindling fish oils. However, canola oil with stearidonic acid is proposed to be used for the mainstream market to improve consumption of n-3 fatty acids. The advantage of this acid is that it bypasses the metabolic conversion of linolenic into stearidonic acid, which is the slowest in the LCPUFA metabolic pathway. Low-saturated canola oil is the main claim driving the export of canola from Canada; however, to protect this market significant effort is being made to lower the amount of saturates in canola oil. The Canola Council of Canada is stimulating the development of canola oil with an amount of saturated fatty acids at 3.5%, allowing processors in the US to utilize the claim of ‘zero saturates’.

4.4.2

High-erucic acid rapeseed (HEAR) oil

In countries that grow canola, HEAR oil is used only in special food applications, and in several non-food applications. The HEAR oil contains about 45–50% erucic acid, the highest erucic acid rapeseed oil available commercially at present. During hydrogenation erucic acid is transferred to behenic acid, which has a very high melting point. Fully hydrogenated HEAR oil is very effective in holding high amounts of liquid oil in its crystal matrix. The patent literature also mentions the use of fully hydrogenated HEAR oil in interesterification with palm stearin fraction to formulate a zero-trans isomer margarine hard base stock. Plant breeding work to raise the erucic acid content is being done in Canada and elsewhere. Indications are that it is possible to obtain oil containing about 80% of erucic acid and this oil will have its main application as industrial lubricant.

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CONCLUSION AND OUTLOOK

Canola oil has the best fatty acid composition among all commodity oils for health; it amalgamates a low level of saturated fatty acids with a high content of monounsaturated and combines PUFA with right and proper ratio of omega-6 to omega-3. Based on the fatty acid composition and its heart-healthy properties, canola oil has penetrated many markets, particularly the US marketplace dominated by soybean oil. In the US breeding of soybean oil that mimics canola’s fatty acid composition is proceeding at a fast pace. Canola/rapeseed oil contains a large number of unique compounds that can be utilized as nutraceuticals with specific health effects. New developments in canola oil are directed to exploit its unique fatty acids composition and the presence of minor components to provide oils with specific nutritional and application properties. New designer oils, specifically developed with health effects in mind, are offering for producers and processors high value-added products and a healthy alternative for consumers. The future of canola/rapeseed oil is in the merging of a diversity of components present in this oil and applications where an array of components is required. Currently, canola oil is used mainly in food applications, which will continue in the future. However, industrial use of canola, mainly as biofuel, is fast developing in Europe. Very encouraging are developments of canola oil for frying, where high-oleic acid oils offering excellent performance are replacing trans-containing frying fats. Labeling regulations eliminating trans fats are stimulating developments in canola oil to change fatty acids and minor components and develop canola-type oils that will replace baking fats, the main carriers of trans fats in our diet. The possibility of modifying enzyme specificity within canola plants and seeds offers additional tools for creating designer oils, which will provide a more diversified range of fatty acids and unique minor components. A great deal of information is available on the fatty acid composition of canola and rapeseed oils. However, less attention is paid to minor components, which are the source of health nutrients with potentially positive effects and impart oil quality in food applications. Development in oil processing is directed to ‘green processing’ and cold-pressed virgin oils, both of which require more data on minor components to understand their chemistry and transfer into oils.

REFERENCES Abidi, S.L., List, G.R. and Rennick, K.A. (1999) Effect of genetic modification on the distribution of minor constituents in canola oil, Journal of the American Oil Chemists’ Society, 76, 463–467. Ackman, R.G. (1990) Canola fatty acids – an ideal mixture for health, nutrition, and food use, in Canola and Rapeseed. Production, Chemistry, Nutrition and Processing Technology (ed. F. Shahidi), Avi Book, Van Nostrand Reinhold, NewYork, pp. 81–98. Ackman, R.G. and Eaton, C.A. (1977) Specific gravities of rapeseed and Canbra oils, Journal of the American Oil Chemists’ Society, 54, 435–439. Aladedunye, F.A. and Przybylski, R. (2009) Degradation and nutritional quality changes of oil during frying, Journal of the American Oil Chemists’ Society, 86, 149–156. Anonymous (2000) Australians using high-oleic canola oil for frying, INFORM, 11(10), 1061. Anonymous (2001a) High-laurate canola oil sold for use as boiler fuel, INFORM, 12(10), 1019–1020. Anonymous (2001b) Diacylglycerol oil products may be headed for US, INFORM, 12(5), 487. Arens, V.M., Ghur, G. and Waibel, J. (1977) Bestimmung des rauchpunktes zur beurteilung von bratund seidefetten, Fette Seifen Anstrichmittel, 79, 256–261.

Gunstone_c04.indd 133

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Barnard, D., Bateman, L., Cole, E.R. and Cunneen, J.I. (1958) Sulphoxides and thiolsulphinates as inhibitors of autoxidation and other free radical reactions, Journal of the Chemical Industry, 1(19), 918– 919. Barth, C.A. (2009) Nutritional value of rapeseed oil and its high oleic/low linolenic variety – A call for differentiation, European Journal of Lipid Science Technology, 111, 953–956. Bowry, V.W. and Stocker, R. (1993) Tocopherol-mediated peroxidation: The prooxidant effect of vitamin E on the radical initiated oxidation of human low-density lipoprotein, Journal of the American Chemists’ Society, 115, 6029–6044. Burton, G.W. and Ingold, K.U. (1989) Vitamin E as in vitro and in vivo antioxidants, Annals of the New York Academy of Science, 570, 7–22. Byrdwell, W.C. and Neff, W.E. (1996) Analysis of genetically modified canola varieties by atmospheric pressure chemical ionization mass spectrometry and flame ionization, Journal of Liquid Chromatography & Related Technologies, 19, 2203–2225. Canadian Oilseed Processors Association, www.copaonline.net/, accessed March 30, 2010. Chapman, D.M., Pfannkoch, E.A. and Kupper, R.J. (1994) Separation and characterization of pigments from bleached and deodorized canola oil, Journal of the American Oil Chemists’ Society, 71, 401–407. Cmolik, J., Pokorny, J., Reblova, Z. and Svoboda, Z. (2008) Tocpherol retention in physically refined rapeseed oil as a function of deodorization temperature, European Journal of Lipid Science & Technology, 110, 754–759. Cmolik, J., Pokorny, J., Dolezal, M. and Svoboda, Z. (2007) Geometrical isomerization of polyunsaturated fatty acids in physically refined rapeseed oil during plant-scale deodorization, European Journal of Lipid Science & Technology, 109, 656–662. Cmolik, J., Schwarz, W., Svoboda, Z. et al. (2000) Effects of plant-scale alkali refining and physical refining on the quality of rapeseed oil, European Journal of Lipid Science & Technology, 102, 15–22. Codex Alimentarius, FAO Food Satndards, www.codexalimentarius.net, accessed March 25, 2010. Diosady, L.L., Sleggs, P. and Kaji, T. (1983) Degumming of canola oils, in 7th Progress Report Research on Canola Seed, Oil, Meal and Meal Fractions, Publication No. 61, Canola Council of Canada, Alberta, pp. 186–199. Elson, C.M., Hynes, D.L. and MacNeil, D.L. (1979) Trace metal content of rapeseed meals, oils and seeds, Journal of the American Oil Chemists’ Society, 56, 998–1002. Endo, Y., Thorsteinson, C.T. and Daun, J.K. (1992) Characterization of chlorophyll pigments present in canola seed, meal and oil, Journal of the American Oil Chemists’ Society, 69, 564–569. Evershed, R.P., Male,V.L. and Goad, L.J. (1987) Strategy for the analysis of steryl esters from plant and animal tissues, Journal of Chromatography, 400, 187–192. Fasina, O.O. and Colley, Z. (2008) Viscosity and specific heat of vegetable oils as a function of temperature: 35 °C to 180 °C, International Journal of Food Properties, 11, 738–746. García-Latas, G., Cercaci, L., Rodriguez-Estrada, M.T. et al. (2008) Sterol oxidation in ready-to-eat infant foods during storage, Journal of Agricultural Food Chemistry, 56, 469–475. Gordon, M.H. and Miller, L.A.D. (1997) Development of steryl ester analysis for the detection of admixture of vegetable oils, Journal of the American Oil Chemists’ Society, 74, 505–510. Hovenkamp, E., Demonty, I., Plat, J. et al. (2008) Biological effects of oxidized phytosterols: A review of the current knowledge, Progress in Lipid Research, 47, 37–49. Hu, X., Daun, J.K. and Scarth, R. (1994) Proportions of 18:1n-7 and 18:1n-9 fatty acids in canola seedcoat surface and internal lipids, Journal of the American Oil Chemists’ Society, 71, 221–223. Jaky, M. and Kurnik, E. (1981) Distribution of linoleic acid in glycerides with special consideration of the β-position, Fetten-Seifen Anstrichmittel, 82, 267–271. Javitt, N.B. (2008) Oxysterols: Novel biologic roles for the 21st century, Steroids, 73, 149–157. Kallio, H. and Currie, G. (1993) Analysis of low erucic acid turnip rapeseed oil by negative ion chemical ionization tandem mass spectrometry. A method giving information on the fatty acid composition in positions sn-2 and sn-1/3 of triglycerols, Lipids, 28, 207–215. Kamal-Eldin, A. and Appelqvist, L.A. (1996) The chemistry and antioxidant properties of tocopherols and tocotrienols, Lipids, 31, 671–701. Kim, J., Kim, D.N., Lee, S.H., Yoo, S.H., and Lee, S. (2010) Correlation of fatty acid composition of vegetable oils with rheological behaviour and oil uptake, Food Chemistry, 118, 398–402. Koba, K., Imamura, J., Akashoshi, A. et al. (2007) Genetically modified rapeseed oil containing cis-9, trans-11, cis-13-octadecatrienoic acid affects body fat mass and lipid metabolism in mice, Journal of Agricultural Food Chemistry, 55, 3741–3748.

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Canola/Rapeseed Oil

135

Kyriakidis, N.B. and Katsiloulis, T. (2000) Calculation of iodine value from measurements of fatty acid methyl esters of some oils: Comparison with the relevant American Oil Chemists’ Society method, Journal of the American Oil Chemists’ Society, 77, 1235–1238. Lambelet, P., Grandgirard, A., Gregoire, S. et al. (2003) Formation of modified fatty acids and oxysterols during refining of low erucic acid rapeseed oil, Journal of Agricultural Food Chemistry, 51, 4284–4290. Lee, J.H., Akoh, C.C. and K.T. Lee (2008) Physical properties of trans-free bakery shortening produced by lipase catalyzed interesterification, Journal of the American Oil Chemists’ Society, 85, 1–11. Liu, H., Biliaderis, C.G., Przybylski, R. and Eskin, N.A.M. (1993) Phase transitions of canola sediments, Journal of the American Oil Chemists’ Society, 70, 441–448. Mag, T. (1990) Further processing of canola and rapeseed oils, in Canola and Rapeseed. Production,Chemistry, Nutrition and Processing Technology (ed. F. Shahidi), Avi Book, Van Nostrand Reinhold, New York, pp. 251–276. Matthaus, B. (2006) Utilization of high-oleic rapeseed oil for deep-fat frying of French fries compared to other commonly used edible oils, European Journal of Lipid Science Technology, 108, 200–201. Matthaus, B. and Bruhl, L. (2008) Why is it so difficult to produce high-quality virgin rapeseed oil for human consumption? European Journal of Lipid Science Technology, 110, 611–617. Matthaus, B., Haase, N.U. and Unbehend, G. (2009) Chemical and sensory characteristics of products fried in high-oleic, low-linolenic rapeseed oil, Journal of the American Oil Chemists’ Society, 86, 799–808. National Academy of Sciences (2000) Report of the Panel on Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids, Food and Nutrition Board, National Academy Press, Washington, DC. Neff, W.E., Mounts, T.L. and Rinsch, W.M. (1997) Oxidative stability as affected by triacylglycerol composition and structure of purified canola oil triacylglycerols from genetically modified normal and high stearic and lauric acid canola varieties, Lebensmittel-Wissenschaft und-Technologie, 30, 793–799. Neff, W.E., Mounts, T.L., Rinsch, W.M., Konishi, H. and El-Agaimy, M.A. (1994). Oxidative stability of purified canola triacylglycerols with altered fatty acid compositions as affected by triacylglycerol composition and structure, Journal of the American Oil Chemists’ Society, 71, 1101–1109. Normand, L., Eskin, N.A.M. and Przybylski, R. (2001) Effect of tocopherols on the frying stability of regular and modified canola oils, Journal of the American Oil Chemists’ Society, 78, 369–373. Noureddini, H., Teoh, B.C. and Clements, L.D. (1992) Densities of vegetable oils and fatty acids, Journal of the American Oil Chemists’ Society, 69, 1184–1188. Oehrl, L.L., Hansen A.P., Rohrer C.A., Fenner G.P. and Boyd L.C. (2001) Oxidation of phytosterols in a test food system, Journal of the American Oil Chemists’ Society, 78, 1073–1078. Patterson, L.K. (1981) Studies of radiation-induced peroxidation in fatty acid micelles, in Oxygen and OxyRadicals in Chemistry and Biology (eds M.A.J. Rodgers and E.L. Powers), Academic Press, New York, pp. 89–95. Petukhov, I., Malcolmson, L., Przybylski, R. and Armstrong, L. (1999) Frying performance of genetically modified canola oils, Journal of the American Oil Chemists’ Society, 76, 627–632. Pongracz, G. (1988), Hitzestabilitaet der Tocopherol, Fat Science Technology, 90, 249–258. Przybylski, R. and Eskin, N.A.M. (1988) A comparative study on the effectiveness of nitrogen or carbon dioxide flushing in preventing oxidation during the heating of oil, Journal of the American Oil Chemists’ Society, 65, 629–634. Przybylski, R. and Eskin, N.A.M. (1991) Phospholipid composition of canola oils during the early stages of processing as measured by TLC with flame ionization detector, Journal of the American Oil Chemists’ Society, 68, 241–245. Przybylski, R., Biliaderis, C.G. and Eskin, N.A.M. (1993a) Formation and partial characterization of canola oil sediment, Journal of the American Oil Chemists’ Society, 70, 1009–1013. Przybylski, R., Eskin, N.A.M., Malcolmson, J. et al. (1993b) Stability of low linolenic acid canola oil in accelerated storage at 60 °C, Lebensmittel- Wissenschaft und-Technologie, 26, 205–209. Raclaru, M., Gruber, J., Kumar, R. et al. (2006) Increase of the tocochromanols conetent in transgenic Brassica napus seeds by overexpression of key enzymes involved in prenylquinone biosynthesis, Molecular Breeding, 18, 93–107. Ratnayake, W.M.N. and Daun, J.K. (2004) Chemical composition of canola and rapeseed oils, in Rapeseed and Canola Oil: Production, Processing, Properties and Uses (ed. F.D. Gunstone), Blackwell Publishing Ltd., Oxford, pp. 44–47. Ryan, E., Chopra, J., McCarthy, F., Maguire, A.R., and O’Brien, N.M. (2005) Qualitative and quantitative comparison of the cytotoxic and apoptotic potential of phytosterol oxidation products with their corresponding cholesterol oxidation products, British Journal of Nutrition, 94, 443–451.

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Rudzinska, M., Wasowicz, E. and Uchman, W. (2005) Plant sterols in food technology, ACTA Scientiarum Polonorum – Technologia Alimentaria, 4, 147–156. Saskatchewan Wheat Pool (1974) The story of rapeseed in Western Canada, Saskatchewan Wheat Pool, Regina, Saskatchewan. Scarth, R. and Tang, J. (2006) Modification of Brassica oil using conventional and transgenic approaches, Crop Science, 46, 1225–1236. Scarth, R., McVetty, P.B.E., Rimmer, S.R. and Stefansson, B.R. (1988) Stellar low linolenic-high linoleic acid summer rape, Canadian Journal of Plant Science, 68, 509–512. Simopoulos, A.P. (2008) Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: Nutritional implications for chronic diseases, Biomedicine & Pharmacotherapy, 60, 502–507. Smiles, A., Kakuda, Y. and MacDonald, B.E. (1988) Effect of degumming reagents on the recovery and nature of lecithins from crude canola, soybean and sunflower oils, Journal of the American Oil Chemists’ Society, 65, 1151–1155. Smiles, A., Kakuda,Y. and MacDonald, B.E. (1989) Effect of degumming reagents on the composition and emulsifying properties of canola, soybean and sunflower acetone insolubles, Journal of the American Oil Chemists’ Society, 66, 348–352. Smouse, T.H. (1994) Factors affecting oil quality and stability, in Methods to Assess Oil Quality and Stability (eds K.Warner and N.A.M. Eskin), AOCS, Champaign, IL, pp. 12–36. Sosulski, F., Zadernowski, P. and Babuchowski, K. (1981) Composition of polar lipids in rapeseed, Journal of the American Oil Chemists’ Society, 58, 561–568. Strocchi, A. (1987) Vegetable oils and corresponding hydrogenated fats: Comparison of sterols, 4-alphamethyl sterol and 4,4-dimethyl sterol composition, Rivista Italiana Sostanze Grasse, 64, 401–409. Suzuki, K. and Nishioka, A. (1993) Behavior of chlorophyll derivatives in canola oil processing, Journal of the American Oil Chemists’ Society, 70, 837–841. Tapel, A.L. (1968) Vitamin E and free radical peroxidation of lipids, Annals of the New York Academy of Science, 203, 12–28. Tso, P., Ding, S., DeMichele, K. and Huang, Y.-S. (2001) Intestinal absorption of high γ-linolenic acid canola oil in lymph fistula rats, in ©-Linolenic Acid: Recent Advances in Biotechnology and Clinical Applications (eds Y.-S. Huang and V.A. Ziboh), AOCS Press, Champaign, IL, pp. 321–334. Usuki, R., Endo, Y. and Kaneda, T. (1984) Prooxidative activities of chlorophylls and pheophytins on the photo-oxidation of edible oils, Agricultural Biology and Chemistry, 48, 991–994. Vecchio, A.J. (1996) High-laurate canola, INFORM, 7, 230–243. Ward, K., Scarth, R., Daun, J.K. and Thorsteinson, T.C. (1994) Characterization of chlorophyll pigments in ripening canola seed (Brassica napus), Journal of the American Oil Chemists’ Society, 71, 1327–1331. Warner, K. and Mounts, T.L. (1993) Frying stability of soybean and canola oils with modified fatty acid composition, Journal of the American Oil Chemists’ Society, 70, 983–989. Wijesundera, R.C. and Ackman, R.G. (1988) Evidence for the probable presence of sulfur-containing fatty acids as minor constituents in canola oil, Journal of the American Oil Chemists’ Society, 65, 959–963. Wijesundera, R.C., Ackman, R.G., Abraham,V. and DeMan, J.M. (1988) Determination of sulfur contents of vegetable and marine oils by ion chromatography and indirect ultraviolet photometry of their combustion products, Journal of the American Oil Chemists’ Society, 65, 1526–1528. Willner, T., Jeß, U. and Weber, K. (1997) Effect of process parameters on the balance of tocopherols in the production of vegetable oils, Fett/Lipid, 99, 138–147. Wolff, R.L. (1993) Heat-induced geometrical isomerization of α-linolenic acid: Effect of temperature and heating time on the appearance of individual isomers, Journal of the American Oil Chemists’ Society, 70, 425–430. Ying, C.F. and DeMan, J.M. (1989) Sulfur and chlorophyll content of Ontario canola oil, Canadian Institute of Food Science Technology, 22, 222–226. Zambiazi, R.C. (1997) The role of endogenous lipid components on vegetable oil stability, PhD thesis, University of Manitoba. Zajic, J., Bares, M., Volhejn, E. and Cmolik, J. (1986) The influence of conditioning on the phospholipid content of pressure-extracted rapeseed oil, Fette Seifen Anstrichmittel, 88, 67–69.

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5

Sunflower Oil

Maria A. Grompone

5.1

INTRODUCTION

One of the most ancient oleaginous species originating in North America, sunflower (Helianthus annuus L.) belongs to the family Compositae (Asteraceae) and the genus Helianthus. Evidence of sunflower cultivation dates from as early as 3000 bc. It was domesticated in several parts of central and eastern North America even before maize (Autino et al. 1993; Melgarejo 1998). With the return of Spanish explorers, sunflower was introduced into Europe towards the beginning of the sixteenth century. Starting from the Iberian Peninsula, sunflower spread rapidly through France and Italy, and thence northward and eastward. The genus Helianthus, from the Greek helios and anthos, meaning sun and flower, respectively, was named after the large, bright yellow inflorescence of sunflowers, facing the sun along its trajectory across the sky. This is also reflected in the common English name of sunflower, as well as in its Spanish, French and German names: girasol, tournesol and Sonnenblumen. Peter i the Great – Tsar between 1682 and 1725 – took sunflower seeds from the Netherlands to Russia, where the crop spread rapidly and was initially used for ornamental purposes. The development of the sunflower oil-extraction industry in the eighteenth century led to a rapid increase in the cultivated area in Russia, which has since consolidated itself as the world’s largest sunflower oil producer (2.56 million tonnes in 2008/09). The sunflower varieties cultivated today in North America derive from Russian seeds introduced towards the end of the nineteenth century. Also in the nineteenth century, Russian immigrants carrying seeds for human consumption introduced the crop into Argentina, where it was not cultivated intensively until the world economic crisis of 1930 to meet a domestic market demand that until then had been supplied with imported oils. Today, Argentina is among the world’s largest sunflower oil producers. Besides Russia (2.56 million tonnes), other large sunflower oil producers are Ukraine (2.63 million tonnes), EU-27 (2.33 million tonnes), Argentina (1.52 million tonnes) and Turkey (0.51 million tonnes). In 2008/09, the total world production of sunflower oil amounted to 11.83 million tonnes, accounting for 9% of the total world production of vegetable oils (see Tables 1.4 and 1.12). Together with palm, soybean and rapeseed oils, sunflower oil is among the four largest produced vegetable oils in the world.

Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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In Argentina, sunflower oil (1.52 million tonnes) is the second-largest produced vegetable oil, following soybean oil. In 2008/09, sunflower oil accounted for as much as 19.7% of Argentina’s total vegetable oil production of 7.7 million tonnes. In the same period, sunflower oil (2.33 million tonnes) accounted for 15.1% of total vegetable oil production in the EU-27 (15.4 million tonnes; see Tables 1.4 and 1.12). Differences in the consumption of sunflower oil between Argentina and the EU-27 are even greater than those indicated for its production. In Argentina, sunflower oil represents 21.1% of total vegetable oil consumption, amounting to 9.5 kg of sunflower oil per capita per annum. The consumption of sunflower oil in the EU-27 is 6.4 kg per capita per annum.

5.2

SUNFLOWER OIL FROM DIFFERENT TYPES OF SEED

Commonly referred to as ‘regular’, only high-linoleic sunflower oil was known until a few decades ago. As the result of mutagenesis and breeding strategies – as opposed to genetically modified crops – newer sunflower hybrids yielding oils of differing composition are currently available on the market. Similar strategies have been developed for other oilseeds, such as rapeseed, soybean, flax, maize (corn), groundnut (peanut) and safflower.

5.2.1

Regular sunflower seeds

Sunflower is a yearly crop reaching 1–3 metres in height. Its inflorescence consists of a cluster of flowers comprising a capitulum or head. Sunflower crops require 70 days from sowing to flowering. Seeds are ripe at an age of 130 days and may be harvested 10 days later (Bockisch 1998). Sunflowers grow in mild temperate climates, predominantly within the temperature range from 20 °C to 25 °C. They thrive in dry, sunny climates and deep soils capable of supplying abundant water. Sunflower crops have a high tolerance to diurnal temperature fluctuations within the range of 8 °C to 34 °C (Bockisch 1998; Autino et al. 1993). In South America, the most suitable climate conditions for the development of sunflower crops are found in Argentina and Uruguay. Two basic types of sunflower seed are known: (i) oil type; (ii) non-oil type (confectionery and bakery grade, also used as bird feed). Oil-type seeds are relatively small and have a thin shell representing 20–25% of the seed weight. The weight of 1000 oil-type seeds may vary between 30 g and 80 g. The shell may vary in colour from fully black to white, including intermediate striped types (Merrien 1998). The shell is composed primarily of fibrous substances (lignin) and cellulosic materials in nearly equal proportions. Nearly all the oil, protein and carbohydrates of oil-type sunflower seeds are found in the kernel, which represents 70% of the seed weight. The oil content in the kernel may be higher than 55%, representing 40% of the seed weight (Autino et al. 1993; Bokisch 1998). Nolasco et al. (2005) studied variations in the oil content of regular sunflower seeds using 11 traditional hybrids grown in different Argentinean localities and found an oil content varying between 40.7% and 56.5% of the seed weight.

5.2.2

Commercial sunflower oil types

The oil-extraction industry has sought to obtain seeds yielding oil with increased oleic acid content, and much experimental research has focused on the development of high-oleic sunflower seeds. Sunflower seeds with an oleic acid content up to 80–90% were developed by K.I. Soldatov, in Russia, by treatment of ‘normal’ planting seeds with the mutagen dimethyl

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sulphate, followed by breeding programmes. Also in Russia, L.N. Kharachenko studied the ‘normal’ Peredovik cultivar and the Pervenets progeny derived from the former by chemical mutagenic treatment. In America, progenies of the Pervenets cultivar were developed by G.N. Fick in plantations in the United States, Argentina and Chile. High-oleic sunflower seeds were produced commercially in the United States in 1984, and were later distributed worldwide (Keller 1995). The sale price of high-oleic sunflower oil (HOSO) is consistently higher than that of regular sunflower oil. In 1995, the US National Sunflower Association (NSA) promoted a sunflower oil with an intermediate oleic acid content of 65% and a saturated fatty acid content no greater than 10%, the remainder consisting of linoleic acid (Gupta 1998; Kleingartner 2002). In a market now familiar with both regular sunflower oil and HOSO, the mid-oleic seeds were trademarked under the ‘NuSun’ name.

5.2.3

Composition of commercially available sunflower oil types

Like most vegetable oils, sunflower oils are predominantly composed of triacylglycerols (98–99%) and a small proportion of phospholipids. The so-called unsaponifiable matter contains tocopherols, sterols and waxes, among other substances. 5.2.3.1

Fatty acid composition

The composition and properties of vegetable oils provided in the Codex Alimentarius may be used as a worldwide reference. Table 5.1 shows the fatty acid composition of regular, mid-oleic and high-oleic sunflower oils. The three commercial types of sunflower oil differ in their oleic and linoleic acid content, but have a nearly equal content of palmitic and stearic acid. The oleic acid content of HOSO exceeds that in conventional edible oils with high oleic acid content, such as olive oil (Table 5.2). Muratorio et al. (2007) determined the quality parameters of oils derived from certified seeds of regular, mid-oleic and high-oleic cultivars grown in different Argentinean localities. Comparing the values of Argentinean sunflower oil with the ranges approved by the Codex Alimentarius: (i) the 18:1 content of Argentinean regular sunflower oil may be higher and, conversely, the 18:2 content lower, than the respective maximum and minimum values provided in the Codex; (ii) the composition of Argentinean high-oleic sunflower oil falls within the ranges provided by the Codex; (iii) the composition of Argentinean mid-oleic sunflower oil is in agreement with that provided by the Codex, both the 18:1 and 18:2 content varying within narrower ranges than Codex provisions. Since Argentina is one of the world’s largest sunflower oil producers, particularly the largest in the southern hemisphere, the variation ranges provided by the Codex Alimentarius have been questioned in the light of the above studies. Similar results had previously been reported (Muratorio et al. 2003). The composition of high-oleic sunflower oil and that of virgin olive oil are compared in Table 5.3. The International Olive Council provides the same composition ranges for olive oil as the Codex Alimentarius. The oleic acid content of HOSO is similar to that of olive oil, with HOSO having slightly lower content of linoleic and palmitic acids and a slightly higher content of stearic acid. Despite the similarity in nutritional value and oxidative stability (see Section 5.7.1), the two oils are sensorially distinct. Refined HOSO can be compared with extra virgin olive oil, though gourmets worldwide would not compare a refined oil, irrespective of source or type, to the virgin oil. The similarity in fatty acid composition between high-oleic sunflower and olive oils may lead to adulteration or fraud, motivated by the price difference between the two oils and by the difficult detection of such frauds by conventional analytical methods. However, the sterol composition may be used to distinguish these oils (see Section 5.2.3.4).

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Table 5.1 Percentage fatty acid composition of regular, mid-oleic and high-oleic sunflower oils. Fatty acid 16:0 18:1 18:2 20:0 22:0 24:0

Regular

High-oleic

Mid-oleic

5.0–7.6 14.0–39.4 48.3–74.0 0.1–0.5 0.3–1.5 ND–0.5

2.6–5.0 75.0–90.7 2.1–17.0 0.2–0.5 0.5–1.6 ND–0.5

4.0–5.5 43.1–71.8 18.7–45.3 0.2–0.4 0.6–1.1 0.3–0.4

Source: Codex-Stan 210-1999. Key: ND = non-detectable

Table 5.2 Percentage fatty acid composition (oleic, linoleic and palmitic) of different edible vegetable oils. Oil Safflower Cottonseed Sunflower (regular) Soybean Corn Rice bran Peanut Canola Olive Sunflower (high-oleic)

18:1

18:2

16:0

8.4–21.3 14.7–21.7 13–40 17.7–25.1 24.6–42.2 42–48 36.4–67.1 52.0–66.9 55–83 70–87

67.8–83.2 46.7–58.2 40–74 49.8–57.1 39.4–60.4 16–36 14.0–43 16.1–24.8 3.5–21 3–20

5.3–8 21.4–26.4 5–8 9.7–13.3 10.7–16.5 16–28 8.3–14 3.3–6.0 7.5–20 3–5

Source: AOCS (1997).

The composition of mid-oleic sunflower oil differs from that of other edible vegetable oils, as shown in Table 5.4. 5.2.3.2

Triacylglycerol composition

The percentage composition of major triacylglycerols (TAG above 1%) of regular sunflower oil is shown in Figure 5.1. In line with its high linoleic acid content, trilinolein (36.3%) and oleo-dilinolein (29.1%) are the most abundant triacylglycerols of regular sunflower oil, the content of triolein (0.6%) being insignificant. The content of triacylglycerols having at least four double bonds exceeds 80% by weight, leading to an oil with a low solidification point (between −16 °C and −19 °C). Unlike other oils such as groundnut oil, regular sunflower oil does not crystallise when stored in a refrigerator, preserving the integrity of oil-based emulsions used for the manufacture of mayonnaise, among other products. Boukhchina et al. (2003) conducted a stereospecific analysis of the triacylglycerols of regular sunflower oil. Figure 5.2 shows the distribution of each fatty acid among the sn-1, sn-2 and sn-3 positions of the glycerol backbone. The 1,2,3-random hypothesis assumes a pool of fatty acids randomly distributed to all three positions of the glycerol moiety. However, despite the low content of palmitic acid in sunflower oil, it is preferentially distributed to the sn-1,3 positions with slight asymmetry, and is nearly non-existent at the sn-2 position.

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Table 5.3 Percentage fatty acid composition of high-oleic sunflower and virgin olive oils. Fatty acid

High-oleic sunflower

16:0 16:1 18:0 18:1 18:2 22:0

Virgin olive

2.6–5 ND–0.1 2.9–6.2 75–90.7 2.1–17 0.5–1.6

7.5–20 0.3–3.5 0.5–5 55–83 3.5–21 0–0.2

Source: Codex-Stan 210-1999 and Codex-Stan 33-1891 Rev. 2-2003. Key: ND = non-detectable

Table 5.4 Comparison of the fatty acid composition of mid-oleic sunflower oil with rapeseed and peanut oils. Fatty acid 16:0 18:0 18:1 18:2 18:3

MO sunflower

Rapeseed

Peanut

3.5–4.4 2–3.1 71.2–74.5 17.3–20.3 –

2.5–7 0.8–3 51–70 15–30 5–14

8–14 1–4.5 35–69 12–43 –

Source: Codex-Stan 210-1999.

40 35

Percentage

30 25 20 15 10 5 0 SOL

POL

OOL

SLL

PLL

OLL

LLL

Triacylglycerol Figure 5.1 Major triacylglycerol composition, in weight percentage, of regular sunflower oil. Source: Prévot (1987). Key: O = oleic acid L = linoleic acid P = palmitic acid S = stearic acid

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sn-1

FA distribution (%)

50

sn-2

sn-3

40

30

20

10

0 16:0

18:1

18:2

Figure 5.2 Distribution of major fatty acids (16:0, 18:1 and 18:2) of regular sunflower oil among three positions of the glycerol backbone. Source: Boukhchina et al. (2003).

Found in all three positions, 18:2 has a slightly higher occurrence at the sn-2 position, while 18:1 occurs slightly more frequently at sn-3. These results are consistent with previously reported data (Rossell et al. 1983; Álvarez-Ortega et al. 1997). The major fatty acid composition of regular sunflower oil at each of the three positions of the glycerol backbone is shown in Figure 5.3. Both 18:2 and 18:1 are near-randomly distributed to all three positions. The fact that 18:1 has a lower occurrence than 18:2 at every position is in agreement with the lower content of 18:1 in regular sunflower oil. Similar results had been reported in previous stereospecific analyses (Damiani et al. 1997). With an 18:1 content in the range between 75% and 91%, the triacylglycerol composition of HOSO is fairly simple, consisting mainly of triolein. The 18:1 content of HOSO is similar to that of olive oil, but the latter contains a smaller amount of 18:2 and a higher amount of saturated fatty acids (Table 5.3). Differences between the triacylglycerol compositions of the two oils are shown in Figure 5.4. Although the sn-2 position is predominantly occupied by 18:1 in both oils, the distribution of fatty acids at the remaining two positions differs for the two oils (Ruiz-Gutierrez et al. 1998). The fatty acid distribution in the triacylglycerols of HOSO is shown in Figure 5.5. Similar conclusions to those obtained for regular sunflower oil may be drawn – the occurrence of saturated fatty acids exclusively at the sn-1 and sn-3 positions, with the unsaturated fatty acids distributed in nearly equal proportions among all three positions. 5.2.3.3

Phosphoacylglycerols (phospholipids)

The phospholipid content of crude regular sunflower oil varies between 0.5% and 1.2%. Solvent-extracted oils generally have a higher phospholipid content than pressed oils. The phospholipid content of sunflower oil, expressed as phosphorus, is normally 200–400 ppm

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70 16:0

60

18:1

18:2 Composition (%)

50 40 30 20 10 0 sn-1

sn-2

sn-3

Figure 5.3 Major fatty acid composition, in weight percentage, of regular sunflower oil at each of three positions of the glycerol backbone. Source: Boukhchina et al. (2003).

70 60 Triacylglycerols (%)

Olive 50

HOSO

40 30 20 10 0 POO

OOO

OLL

Figure 5.4 Major triacylglycerol composition of high oleic sunflower oil and olive oil. Source: Ruiz-Gutierrez et al. (1998). Key: L = linoleic acid O = oleic acid P = palmitic acid

for the crude oil (Gupta 2002) and below 1 ppm for the refined oil. Phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols and phosphatidic acids are major phospholipids of regular sunflower oil, most of which are hydratable and may be removed from the crude oil by water degumming (see Section 5.5.3.1).

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sn-1 sn-2 sn-3

Percentage

60 50 40 30 20 10 0 16:0

18:0

18:1

18:2

Figure 5.5 Distribution of each major fatty acid (16:0, 18:0, 18:1 and 18:2) of HOSO among three positions of the glycerol backbone. Source: Damiani et al. (1997).

5.2.3.4

Nonglyceride components of sunflower oils

The unsaponifiable matter of a crude sunflower oil amounts to less than 15 g/kg, irrespective of oil type (Prévot 1987; Merrien 1998; Codex Alimentarius). It is composed of sterols (2.4–4.6 g/kg), tocopherols and tocotrienols (0.4–1.5 g/kg) and other minor components. Tocopherols and tocotrienols The Codex Alimentarius provides tocopherol ranges for crude regular, mid-oleic and higholeic sunflower oils, expressed in mg/kg (Table 5.5). Other reported data are consistent with Codex provisions (Abidi 2003). The tocopherol and tocotrienol compositions do not differ substantially for the three sunflower oil types, although mid-oleic sunflower oil may have a lower α-tocopherol content than some varieties of the other types. Disk et al. (2006) reported a near-constant α:β:γ:δ ratio of 94:5:0.5:0.5 for the tocopherols of sunflower oil. Nolasco et al. (2005) studied variations in the tocopherol content of regular sunflower oil using seeds of 11 traditional hybrids cultivated in different Argentinean localities. Their results are consistent with previously reported data (Melgarejo 1998). Figure 5.6 shows the maximum content of major tocopherols and tocotrienols for the four largest produced vegetable oils in the world: palm, soybean, rapeseed and regular sunflower oils. The biological value of tocopherols differs according to the structure of each compound. The relative in vivo Vitamin E activity of tocopherols may be expressed as α>β>γ>δ for the different tocopherols. However, γ-tocopherol has the highest in vitro antioxidant activity in oils. Among the three types of sunflower oil, the regular type has the largest content of α-tocopherol, amounting to 91–97% of the total tocopherol content. However, γ-tocopherol is usually the most abundant in crude vegetable oils, with palm oil being unusual in its greater content of tocotrienols. A high α-tocopherol content enhances the nutritional value of sunflower oil as a vitamin E source, compared with other commercial vegetable oils.

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Table 5.5

145

Tocopherol composition (mg/kg) of crude sunflower oils.

Content (mg/kg) α-tocopherol β-tocopherol γ-tocopherol δ-tocopherol Total

Regular

High-oleic

Mid-oleic

403–935 ND–45 ND–34 ND–7.0 440–1520

400–1090 10–35 3–30 ND–17 450–1120

488–668 19–52 2.3–19 ND–1.6 509–741

Source: Codex-STAN 210-1999. Key: ND = non-detectable

2500

Tocotrienols

2000

Alpha

Content (ppm)

Gamma Delta

1500

1000

500

0 Palm

Soybean

Rapeseed

Sunflower

Figure 5.6 Maximum tocopherol and tocotrienol content of crude palm, soybean, rapeseed and regular sunflower oils. Source: Codex-Stan 210-1999.

Phenolic compounds Phenolic compounds are major natural antioxidants. The phenolic content is usually expressed in terms of caffeic acid equivalents (CAE). The phenolic content of vegetable oils is in the range of 18–99 ppm CAE irrespective of source or type. Caffeic acid and chlorogenic acid (an ester of the former with quinic acid) are the most abundant phenolic compounds in sunflower oil. The phenolic acid profile of sunflower oil consists of p-hydroxybenzoic (1.5 μg/100 g oil), vanillic (6.9 μg/100 g oil), caffeic (4.9 μg/100 g oil), p-coumaric (1.8 μg/100 g oil), ferulic (1.3 μg/100 g oil) and sinapic (1.4 μg/100 g oil) acids, amounting to a total of 17.8 μg/100 g oil (Siger et al. 2008). Sterols Sterols account for most of the unsaponifiable matter of a vegetable oil, the sterol profile being characteristic of each oil type. The total sterol content (ppm) and the percentage content of each sterol type in each of the three sunflower oil types are shown in Table 5.6.

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Table 5.6

Sterol composition (mg/kg) of crude sunflower oils.

Sterol composition

Regular

High-oleic

Mid-oleic

Campesterol (%) Stigmasterol (%) β-sitosterol (%) Δ5-avenasterol (%) Δ7-stigmasterol (%) Δ7-avenasterol (%) Other sterols (%) Total sterols (mg/kg)

6.5–13 6–13 50–70 ND–6.9 6.5–24 3–7.5 ND–5.3 2400–5000

5–13 4.5–13 42–70 1.5–6.9 6.5–24 ND–9 3.5–9.5 1700–5200

9.1–9.6 9–9.3 56–58 4.8–5.3 7.7–7.9 4.3–4.4 5.4–5.8

Source: Codex-STAN 210-1999. Key: ND = non-detectable

The sterol content and composition of the three commercial sunflower oil types do not differ significantly. Most abundant among sunflower oil sterols is β-sitosterol, followed by Δ-7-stigmasterol, which may be used for adulteration testing, since most vegetable oils other than sunflower and safflower oil have low amounts of Δ-7-stigmasterol (less than 7%). The sterol content of sunflower oil has an intermediate value compared with that of other vegetable oils. The highest sterol contents provided by the Codex Alimentarius for vegetable oils are 4800–11 300 ppm for rapeseed oil, 8000–22 100 ppm for maize oil and 4500–19 000 ppm for sesame oil. The sterol composition of virgin olive oil provided by the International Olive Council differs widely from that of high-oleic sunflower oil. Olive oil has a fairly low content of brassicasterol and campesterol, with over 93% of the sterol content composed of β-sitosterol, avenasterol, stigmastadienol, clerosterol and sitostanol. Most of these are non-existent in sunflower oil. The stigmasterol content of olive oil is lower than the content of campesterol, which is lower than 4%. Considering the similarity in the fatty acid (Table 5.3) and triacylglycerol (Figure 5.4) composition of olive and high-oleic sunflower oils, the sterol composition appears a useful tool for detecting adulteration in olive oil. Pigments Carotenoids and chlorophylls are the most abundant lipochromes of vegetable oils. Containing 1–1.5 ppm of carotenoids and 200–500 ppb of chlorophylls, crude sunflower oil is not particularly rich in the former (like palm oil) nor in the latter (like rice bran, rapeseed, olive and avocado oils). The carotenoid and chlorophyll contents of a fully refined oil are considerably lower than those of the crude oil (Gupta 2002). Hence the light amber colour of crude sunflower oil turns to pale yellow on bleaching. Other constituents of the unsaponifiable matter Aliphatic compounds and terpenoids may occur naturally in vegetable oils. Squalene is the most abundant compound of the terpenoid family. Regular sunflower oil has been reported to have a squalene content as low as 0.008–0.019% (Bockisch 1998) or 15–20 mg/100 g oil (Merrien 1998), and an aliphatic alcohol content of 100 mg/100 g oil (Merrien 1998).

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5.2.4

147

Other sunflower seed types to be commercialised

Currently, most genetic research into new types of sunflower oil is aimed at modifying the fatty acid composition by increasing the saturated fatty acid content (palmitic and/or stearic acid) or at increasing the content of natural antioxidants in the oil. 5.2.4.1

Mid-oleic sunflower oil with increased tocopherol content

A choice oil for use as salad dressing, regular sunflower oil is an excellent source of linoleic acid (an essential omega-6 parent fatty acid) and is also rich in α-tocopherol (vitamin E). However, a high content of 18:2 results in inadequate oxidative stability of regular sunflower oil for use in frying (see Sections 5.7 and 5.9). Developed as the result of mutagenesis and breeding for oil composition, high-oleic sunflower oil has a significantly lower 18:2 content than regular sunflower oil, providing an alternative to the use of hydrogenation for improving the oxidative stability of sunflower oil. On the other hand, high-oleic sunflower oil is therefore not an adequate source of the essential omega6 fatty acid 18:2. With an intermediate content of 18:2, mid-oleic sunflower oil has intermediate oxidative stability compared with that of regular and high-oleic sunflower oils. Further research was aimed at increasing the content of natural antioxidants in mid-oleic sunflower oil, in particular the γ- and δ-tocopherol contents, as sunflower oil is already fairly rich in α-tocopherol (Warner et al. 2008). The study led to the development of a mid-oleic hybrid with a tocopherol profile similar to that of crude soybean oil, containing 470 ppm of γ-tocopherol, 100 ppm of δ-tocopherol and 300 ppm of α-tocopherol, therefore rich in vitamin E, while retaining significant amounts of the essential fatty acid 18:2 (Table 5.5). 5.2.4.2

Sunflower oils with a high content of saturated fatty acids

Fats that are solid or semi-solid at room temperature are used in the preparation of many food-industry products. As an alternative to the strongly criticised use of animal fats or partially hydrogenated vegetable oils, vegetable fats with a high content of saturated fatty acids have received considerable interest (Cantisán et al. 2000). Among the saturated fatty acids, stearic acid has a neutral effect on serum lipoprotein cholesterol. A fat with a high stearic acid content and a low palmitic acid content was sought, since palmitic acid is known to be highly atherogenic. New sunflower mutants with increased saturated fatty acid content were developed by conventional mutagenesis and breeding programmes. Osorio et al. (1995) developed the following sunflower mutants: high-stearic CAS-3 (ca. 26% 18:0), mid-stearic CAS-4 and CAS-8, and high-palmitic CAS-5 (ca. 25% 16:0). Fernández-Martínez et al. (1997) implemented a new mutagenesis programme using high-oleic BSD-2-423 and selected (out of 2000 mutant seeds) CAS-12, having a high content of 16:0 (25–30%) and 18:1, and a low content of 18:2 (<5%). Other, high-stearic mutants were also studied (Fernández-Moya et al. 2002, 2005, 2006). Cantisán et al. (2000) studied the composition of CAS-3, CAS-4 and CAS-8, and PérezVich et al. (2000) that of CAS-5. Márquez-Ruiz et al. (1999) studied the fatty acid and triacylglycerol composition of these mutants. Garcés et al. (2009) compared the fatty acid and triacylglycerol composition of regular RHA-274, high-oleic CAS-9, high-stearic/high-oleic CAS-15 (HS HO) and high-stearic/high-linoleic CAS-30 (HS HL).

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Table 5.7 Fatty acid composition (%) of new sunflower lines compared with regular and commercial high-oleic sunflower oils.

High-linoleic oils Regular (commercial) High-stearic I High-stearic II High-palmitic I High-palmitic II High-oleic oils High-oleic I (commercial) High-oleic II High-stearic High-palmitic I High-palmitic II

16:0

16:1

18:0

18:1

18:2

7 6 7 31 32

– – – 5 1

5 24 30 2 13

30 14 16 17 8

58 56 47 45 46

5 5 6 32 29

– – – 6 1

3 4 21 3 9

82 90 69 55 56

9 1 4 4 5

Source: Martínez-Force et al. (2007).

Martínez-Force et al. (2009), Fernández-Moya et al. (2000) and Alvarez-Ortega et al. (1997) reported the stereospecific distribution of fatty acids in the triacylglycerols of mutants with increased saturated fatty acid content. Based on these studies, Instituto de Agricultura Sostenible de Córdoba (Spain), Instituto de la Grasa de Sevilla (Spain) and Advanta Semillas developed new sunflower lines with a high content of saturated fatty acids, as shown in Table 5.7. The high-oleic/high-palmitic line contains mainly triacylglycerols formed by oleic and palmitic acid. As a result, the oil is highly resistant to oxidation, with a twofold higher oxidative stability than that of higholeic sunflower or refined olive oil (Márquez-Ruiz et al. 1999). The HS HO line has a fourfold higher stearic acid content (18%) than the other types, and a threefold higher oleic acid content (69%) than regular sunflower oil, leading to widely different physical properties from those of regular sunflower oil. Dubinsky (2008) reported the triacylglycerol composition of HS HO sunflower oil, consisting of 14% of StOSt, 49% of StOO and 25% of OOO (St = saturated fatty acid; O = oleic acid). Limited amounts of commercial hybrids sown in Argentina were first harvested in March–April 2008. The seeds are traded by Advanta Semillas under the Nutrisun brand name. A sharp increase in production was expected after the commercial release of the seeds in 2009–2010. Starting from Argentina, a staged programme envisages the production of both seed and oil in other major sunflower-producing areas worldwide.

5.3

PHYSICAL AND CHEMICAL PROPERTIES

Table 5.8 shows the major physical and chemical properties of regular, high-oleic and midoleic sunflower oils.

5.3.1

Relative density

Industrial design methods for tank capacity and flow rate (usually expressed in volumetric units) depend strongly on the density of a fat or oil, which varies according to temperature. Unlike the case with regular sunflower oil, there has been little reported on the temperature

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Table 5.8

149

Physical and chemical properties of regular, high-oleic and mid-oleic sunflower oils.

Property

Regular

Relative density (at X °C/water at 20 °C)* Relative density (at 15.5/15.5 °C)** Relative density (at 25/25 °C)** Refractive index (ND)* Refractive index at 25 °C** Saponification number (mg KOH/g oil)* Iodine value (Wijs)* Unsaponifiable matter (g/kg)*

High-oleic

Mid-oleic

0.918–0.923 (X = 20 °C) 0.918–0.923

0.909–0.915 (X = 25 °C) 0.915–0.920

0.914–0.916 (X = 20 °C) –

–

0.912–0.913

–

1.461–1.468 1.472–1.476 188–194

1.467–1.471 (25°C) 1.467–1.469 182–194

1.461–1.471 – 190–191

118–141 ≤15

78–90 ≤15

94–122 ≤15

Sources: * Codex Alimentarius: Standard for Named Vegetable Oils Codex-Stan 210-1999; ** AOCS (1997).

dependence of the density of high- and mid-oleic sunflower oils, as both types are relatively new. Formulae for estimating the density of vegetable oils may be found in the literature (Halvorsen et al. 1993; Rodenbush et al. 1999).

5.3.2

Viscosity

Vegetable oil viscosity is a relevant parameter when pumping is required. Except in extreme conditions of high shear stress, all vegetable oils show full Newtonian behaviour. Vegetable oil viscosity depends on temperature and on fatty acid composition (DeMan 1992). Abramovic and Klofutar (1998) studied the temperature dependence of the dynamic viscosity of several vegetable oils, including refined and unrefined regular sunflower oil. Rodenbush et al. (1999) proposed equations for estimating the viscosity–density relationship for various vegetable oils, including regular sunflower oil.

5.3.3

Refractive index

Refractive index is dependent on unsaturation and may be used as a readily available control parameter in hydrogenation processes.

5.3.4

Smoke point, flash point and fire point

Smoke point, flash point and fire point are relevant parameters in deep-fat frying processes. Smoke point is associated with the content of free fatty acid and of partial glycerides and depends on the oil’s acidity rather than its fatty acid composition. The smoke point of a refined solvent-extracted oil also depends on the amount of residual solvent in the oil after processing. For a fully refined regular sunflower oil of 0.10% acidity, Bockisch (1998) reported a smoke point of 209 °C, a flash point of 316 °C and a fire point of 341 °C. Ali and Hanna (1994) reported the flash point of regular sunflower oil to be 274 °C. The smoke point has been reported to increase with the addition of antioxidants such as BHT, BHA and TBHQ (Yen et al. 1997), providing a possible explanation for the above differences in the reported data.

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5.3.5

Other physical properties

Other physical properties of regular sunflower oil include (Coupland and McClements 1997): ultrasonic velocity (1471.6 m s−1), specific heat content at constant pressure (2.197 J kg−1°C−1) and adiabatic expansion coefficient (6.61 × 10−4°C−1). The heat content of regular sunflower oil was reported to be 39 575 kJ/kg (Ali and Hanna 1994) and 39 486 kJ/kg (Bhattacharyya and Reddy 1994).

5.4 5.4.1

MELTING PROPERTIES AND THERMAL BEHAVIOUR Melting properties of regular sunflower oil

Crude regular sunflower oil is liquid at room temperature. The refined oil is suitable for use as salad oil since it withstands refrigerator temperatures without the appearance of turbidity. Used as a control parameter, the cold test is expressed in terms of the number of hours an oil stored at 0 °C remains clear. The cold test value of refined sunflower oil is not less than the required 5.5 hours (Gupta 2002). The cloud point and pour point values, respectively associated with the appearance of turbidity and with an extremely high viscosity – or the occurrence of gelation – are relevant design parameters when oils are pumped at low temperatures. Bockisch (1998) reported a cloud point of regular sunflower oil of −10 °C (solidification point in the range from −16 °C to −18 °C). However, Ali and Hanna (1994) reported a cloud point of 7.2 °C and a pour point of −15 °C. The apparent inconsistencies in the reported data may be attributed to a difference in the degree of winterisation of the oils.

5.4.2

Thermal behaviour of different sunflower oil types

Thermal behaviour may be studied over a wide temperature range by means of differential scanning calorimetry (DSC). A thermogram shows the amount of energy absorbed by a solid as it melts progressively with increasing temperature. Figure 5.7 is a bar chart showing the solid content of different sunflower oil types in the temperature range from −20 °C to 15 °C, calculated by partial integration of the peak area in the thermogram. The chart shows clear differences in thermal behaviour of the three oil types. Over the range from refrigerator to room temperature (420 °C), HS HO sunflower oil has a higher solid content than the HO type, while regular sunflower oil remains practically free of solids. It is therefore suitable for refrigerator storage and for use as salad oil. Like olive oil, HO sunflower oil crystallises partially in cold ambient conditions and solidifies when stored in a refrigerator. HS HO sunflower oil is semi-solid below 10 °C, and solid below 5 °C.

5.5

EXTRACTION AND PROCESSING OF SUNFLOWER OIL

A detailed description of conventional seed-oil extraction and processing methods, including flowcharts and calculations, among other relevant information, may be found in the general fat and oil literature. Here, reference is made to those aspects relevant to the processing of sunflower oil.

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151

100 90 HO

Solid content (%)

80

HS HO Regular

70 60 50 40 30 20 10 0 –20

–15

–10

–5

0

5

10

15

Temperature (8C)

Figure 5.7 Solid content of regular, HO, and HS HO sunflower oils at temperatures ranging between −20 °C and 15 °C. Source: Grompone and Irigaray, unpublished data.

5.5.1

Preparation of sunflower seeds for extraction

The moisture content of sunflower seeds must be reduced to ca. 8–9% to avoid undesired enzymatic reactions during storage. Sunflower seeds are enclosed by a relatively hard hull, rich in waxes and representing ca. 30% of the seed weight. Seeds are dehulled prior to extraction to avoid the incorporation of a large amount of waxes in the extracted oil. The wax content of an oil extracted from undehulled seed is fivefold higher than that of the oil extracted from the same dehulled seed. However, a small fraction of hull (ca. 10%) is left with the seed to ensure easy percolation during the solvent-extraction process.

5.5.2

Sunflower oil extraction

Sunflower oil is generally extracted in two stages. Initially, a fraction of the oil is mechanically extracted by screw-press expelling. The cake obtained from this pressing stage, containing 15–20% of oil, is later solvent extracted, usually with hexane. Oils obtained by pressing are considered to be of better nutritional quality than those obtained by solvent extraction. However, both fractions are generally blended prior to storage.

5.5.3

Processing of crude sunflower oil

Crude sunflower oil is usually processed through the same conventional refining stages as used for other seed oils. Particular requirements specific to sunflower oil refining are associated with the inclusion of a dewaxing stage and the importance of the degumming stage. The conventional alkali refining process consists of degumming, alkali neutralisation, dewaxing, bleaching and deodorisation stages. Alternatively, a pre-dewaxing stage after neutralisation leads to a reduction in the wax content down to 100–150 ppm. Likewise,

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Phospholipid content (%)

1.2

Minimum Maximum

1 0.8 0.6 0.4 0.2 0 Pressed

Extracted

Degummed

Figure 5.8 Total phospholipid content of two crude regular sunflower oils (hot-pressed and solventextracted) and the degummed oil. Source: Carelli et al. (2002).

a winterisation stage may be included after bleaching for removal of any remaining wax. Physical refining comprises degumming, dewaxing, bleaching and deodorisation stages. While sunflower oil contains carotenoids and xanthophylls in moderate amounts, it does not contain significant amounts of chlorophylls, resulting in ease of bleaching (see Section 5.2.3.4). Nonetheless, in the physical refining of sunflower oil, bleaching is aimed at the removal of phospholipids and metals in addition to coloured materials. 5.5.3.1

Degumming

The phospholipid content of solvent-extracted oils is higher than that of hot-pressed oils; cold-pressed oils do not contain significant amounts of phospholipids. Major sunflower phospholipids are hydratable (see Section 5.2.3.3) and may be removed by water degumming (Brevedan et al. 2000). Figure 5.8 shows ranges of the phospholipid content of crude (hot pressed and solvent extracted) and degummed regular sunflower oil. Carelli et al. (2002) also reported ranges for the content of each phospholipid in each of these oils. More efficient degumming results from acid treatment, with increased hydratability following the addition of phosphoric or citric acid. Non-hydratable phospholipids may also be removed by enzymatic treatment relying on special biochemical reactions, such as the enzyme-catalysed lipolysis of phospholipid molecules (Carelli et al. 2002). 5.5.3.2

Dewaxing

As much as 83% of the wax content of sunflower seeds is found in the hull, 17% in the seedcoat, and traces in the kernel. The concentration of seed-protecting substances (waxes) in the hull is higher for the high-yield seeds than for the traditional seeds. The hull of improved hybrids may contain up to 3–4% of wax, compared with 1% in the hull of traditional seeds, and conventional dewaxing methods have been improved.

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Because both pressing and solvent extraction rely, for easy extraction, on a certain amount of hull remaining in the seed meal, the wax content is considerably higher in oils extracted from improved hybrids than in a regular oil. Crude sunflower oil may contain up to 2000– 3000 ppm of wax, depending on seed variety and means of extraction. The wax precipitate does not affect the nutritional or sensory properties of an oil, yet it is disliked by some consumers. The melting point of sunflower oil wax is ca. 75 °C. Their solubility in the oil is low, leading to the appearance of turbidity in a refined oil as the temperature is reduced. Cold stability is usually assessed by means of the cold test. Oils passing the cold test will remain clear – that is, without the appearance of turbidity – after 5.5 hours’ storage at 0 °C. Bloch (1990) studied the temperature dependence of the solubility of sunflower oil waxes, which was found to increase with temperature from an extremely low value in the order of 0.1 ppm at 0 °C to as much as 12 ppm at 20 °C. Thus, an oil that is clear at room temperature may become turbid if stored in a refrigerator. Notwithstanding the results of the cold test, a wax precipitate may form several days after refining. The time necessary for the appearance of turbidity in a sunflower oil stored at 0 °C depends on its wax content. An oil containing 6 ppm of wax becomes turbid after 10 days, a time span far exceeding that considered by the cold test (Turkulov et al. 1986, 2000). Both the wax content and composition of sunflower oil depend on the method used for extraction (Carelli et al. 2002), the cold-pressed oil being richer in 42-carbon wax esters than the solvent-extracted oil. The extractability of waxes depends significantly on the extraction temperature, particularly for those waxes of carbon number above 42 that have the highest melting points. The wax content also depends on the refining process conditions. The wax composition of a crude oil differs from that of the refined oil, indicating that the profile of the waxes precipitating from an oil during refining differs from that of the waxes remaining in the oil. This explains the apparent inconsistencies among the reported data on the wax composition of sunflower oil (Liu et al. 1996). 5.5.3.3

Physical refining

The success of the physical refining processes depends largely on the pre-treatment of the crude oil, aimed at the efficient removal of phospholipids, among other compounds. Different by-products of sunflower oil processing are obtained in chemical or physical refining. The deodoriser distillate obtained as a by-product of chemical refining may be used as feedstock for the recovery of tocopherols (mainly vitamin E) and sterols. Deodoriser distillate obtained from physical refining also contains free fatty acids, but is not an attractive vitamin E or sterol feedstock. Deodoriser distillate obtained from chemical refining of sunflower oil may contain as much as 5–7% of total tocopherols, compared with only 1–2% contained in the deodoriser distillate from physical refining (Kövári et al. 2000). The following specifications are generally used for neutralised, dewaxed, bleached and deodorised regular sunflower oil: smoke point of 252–254 °C, maximum contents of 1 ppm of phospholipids, 1.5% of unsaponifiables and 0.03 ppm of chlorophyll, and Lovibond colour 2.0 red/20.0 yellow.

5.6

MODIFIED PROPERTIES OF SUNFLOWER OIL

Like other edible vegetable oils, sunflower oil may be chemically modified by hydrogenation or by interesterification with other vegetable and animal fats.

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5.6.1

Hydrogenation of regular sunflower oil

A relatively good oxidative stability of regular sunflower oil results from the insignificant content of linolenic acid (see Section 5.7.1). To increase the stability of vegetable oils having a higher linolenic acid content (e.g. soybean and rapeseed oil), light hydrogenation is required to reduce the level of linolenic acid, while avoiding the formation of significant amounts of trans-isomers. In producer countries, regular sunflower oil is partially hydrogenated for use in the manufacture of shortenings and margarines. The behaviour of sunflower oil in the hydrogenation process is similar to that of soybean oil, and does not require special reaction conditions. Nor does it contain any compounds that may interfere with the hydrogenation reaction, unlike the case with rapeseed oil. However, the use of partially hydrogenated sunflower oil for the manufacture of margarine spreads may lead to the appearance of graininess during storage, resulting from a strong tendency of partially hydrogenated sunflower oil to form β crystals (Section 5.8.2). Topallar et al. (1995) studied the density and viscosity of partially hydrogenated regular sunflower oil (iodine value no greater than 82.4) over the range of 25–50°C. At a given temperature, the viscosity of the partially hydrogenated oil is twice that of the unhydrogenated oil. In the light of recent recommendations issued by international food associations, the formation of trans-isomers during hydrogenation using conventional nickel catalysts is considered undesirable. Conventional partial hydrogenation results in the formation of up to 40% of trans-isomers in the hydrogenated product. In a laboratory study, Ajzenberg (2002) studied the amount of trans-isomers as a function of the hydrogenation temperature and the amount of silica-supported nickel catalyst. Fernández et al. (2007) studied the partial hydrogenation of sunflower oil using conventional nickel catalysts under different operational conditions. These results may be used as a basis for the improvement of industrial hydrogenation processes. New catalysts have been studied with a view to minimising the trans-isomer content of partially hydrogenated sunflower oils (Piqueras et al. 2008; Naglic et al. 1998; Tonetto et al. 2009; Sánchez et al. 2009). However, none of the commercially available catalysts enables the production of a partially hydrogenated sunflower oil having an insignificant trans content. Supercritical fluids may be used for the hydrogenation of low vapour pressure substrates. The use of supercritical fluids leads to an increased solubility of hydrogen in the oil phase, thereby resulting in a single phase; as opposed to conventional hydrogenation methods, which rely on three-phase (gas–liquid–solid) systems. Additional benefits resulting from the use of supercritical fluids are associated with increased diffusion coefficients of both reactants and products, thus eliminating mass-transfer restrictions and resulting in increased reaction rate and selectivity. The use of a supercritical fluid and a platinum catalyst has been proposed, enabling a reduction in the trans content to values below 5% (Ajzenberg 2002).

5.6.2

Interesterification of sunflower oil

Products showing different thermal behaviour may be obtained by interesterification of sunflower oil with different solid fats and may be used in several specific food-industry applications as an alternative to the use of the partially hydrogenated oil – rich in trans-isomers.

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5.6.2.1

155

Interesterification of beef tallow with regular sunflower oil

Countries rich in livestock resources produce large amounts of beef tallow as a by-product of the slaughter industry. Beef tallow has traditionally been used in the manufacture of bakery products. Among other properties of beef tallow, a hard texture and a melting point above the mouth temperature are disliked by some consumers. Composed of large solid spherulites responsible for a sandy mouth feel, beef tallow may be interesterified with sunflower oil to obtain a blend that solidifies in the form of minute crystals, giving the solid product enhanced consistency and texture. The chemical interesterification of beef tallow with regular sunflower oil has been reported (Chobanov and Chobanova 1977; Grompone 1991; Rodríguez et al. 2001). Lipase catalysis constitutes an alternative to chemically catalysed interesterification-yielding products of different physical properties according to lipase specificity (Foglia et al. 1993; Jachmanián et al. 2002).

5.6.2.2

Interesterification of palm oil with regular sunflower oil

A tendency to crystallise in the β′ form makes palm oil suitable for use in yellow fat spread formulations. However, as it does not melt completely in the mouth, it is usually blended or interesterified with softer oils – such as lauric or other, liquid vegetable oils. Dian et al. (2006) studied the chemical interesterification of various binary and ternary mixtures of palm oil, regular sunflower oil and palm kernel olein. Lai et al. (1998) examined the enzymecatalysed interesterification of a mixture of sunflower oil with palm stearin using commercially available lipases.

5.7

OXIDATIVE STABILITY OF COMMERCIAL SUNFLOWER OILS

Good oxidative stability results in a good storage quality of sunflower oil and related oilbased products. The oxidation reactions leading to the deterioration of both sunflower oil and related products during their useful life are the same as for other edible vegetable oils, and may be found in the general literature.

5.7.1

Inherent stability of different commercial sunflower oil types

The oxidative stability of a fat or oil depends on the fatty acid composition of its constituent triacylglycerols. Gunstone and Hilditch (1945) reported a 1:10:25 ratio for the relative oxidation rates of 18:1, 18:2 and 18:3 methyl esters, respectively. The inherent stability is a theoretical value defined as the weighted sum of relative oxidation rates multiplied, respectively, by the percentage content of each constituent fatty acid, in such a way that the lower the inherent stability value, the more stable a fat or oil is. Erickson (2006) calculated the inherent stability of common edible fats and oils (Table 5.9). The iodine value accounts for the overall degree of unsaturation of an oil’s constituent fatty acids, but does not relate directly to the inherent stability, as the latter is dependent on the fatty acid profile and particularly on the proportion of polyunsaturated fatty acids.

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Table 5.9

Inherent stability and iodine value of different fats and oils.

Oil/fat

Inherent stability

Iodine value

7.0 6.8 6.2 5.5 5.4 4.3 3.7 1.9 1.7 1.5 1.3 0.86 0.27 0.24

132 136 128 120 110 105 100 85 62 82 50 44 13 8

Soybean Sunflower (regular) Corn Rapeseed (LEAR) Cottonseed Ricebran Peanut Sunflower (high-oleic) Lard Olive Palm Tallow Palmkernel Coconut Source: Erickson (2006).

Table 5.10 Fatty acid composition (%) and calculated inherent stability of regular, high-oleic (HO), highstearic/high-oleic (HS HO), high-stearic/high-linoleic (HS HL), high-palmitic/high-linoleic (HP HL) and high-palmitic/high-oleic (HP HO) sunflower oils.

16:0 18:0 18:1 18:2 Inherent stability

Regular

HS HL

HP HL

HS HO

HP HO

7 6 29 58 5.9

6 30 10 50 5.3

32 13 8 46 4.7

6 24 62 5 0.7

29 9 56 5 0.6

HO 5 3 90 2 0.2

Source: Garcés et al. (2009); Martínez-Force et al. (2007).

Table 5.10 shows the inherent stability of regular, high-oleic (HO), high-stearic/higholeic (HS HO), high-stearic/high-linoleic (HS HL), high-palmitic/high-linoleic (HP HL) and high-palmitic/high-oleic (HP HO) sunflower oils, according to their fatty acid compositions (Martínez-Force et al. 2007; Garcés et al. 2009). The inherent stability of these oils depends mainly on the level of 18:2. In addition to the fatty acid composition, several factors affect the oxidative stability of an oil during storage. Although the inherent stability may be used for preliminary assessment of oxidative stability, measurements should be made for the particular commercial variety, batch and storage conditions.

5.7.2

Shelf-life of sunflower oil

Martín-Polvillo et al. (2004) studied the oxidative stability of sunflower oils with different levels of unsaturation: a regular oil (OSI time of 7.4 h) and a high-oleic oil (OSI time of 20.1 h). Topallar et al. (1997) examined the autoxidation kinetics of unhydrogenated (iodine

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157

value of 131.7) and partially hydrogenated (iodine value of 82.4) regular sunflower oils stored under ambient conditions in sunlight for 30 days in glass, PET and metal containers. Results were as expected: (i) the oxidation rate was higher for the unhydrogenated than for the partially hydrogenated oil; (ii) the oxidation rate was higher for the oils stored in glass containers than for those stored in PET containers; (iii) the lowest rate of oxidation was found for the oil stored in metal containers; that is, unexposed to light. The oxidative stability of a commodity vegetable oil depends not only on the amount of natural antioxidant remaining in the oil after refining, but also on the amount of added antioxidants, among other quality parameters of the refining process. The content of natural tocopherols and tocotrienols of sunflower oil was discussed in Section 5.2.3.4. Fuster et al. (1998) studied the effect of added α-tocopherol and γ-tocopherol on the oxidative stability of a sunflower oil stripped of natural antioxidants and kept at 55 °C for seven days. At concentrations below 40 ppm, α-tocopherol was found to be a more efficient antioxidant than γ-tocopherol, while the opposite was apparent at concentrations above 200 ppm when α-tocopherol was less effective. No pro-oxidant behaviour was found at concentrations below 2000 ppm. These results showed that the apparent pro-oxidant effect of α-tocopherol may be attributed to a synergistic action with pro-oxidants such as transition metal ions and peroxides. Despite much research into the role of β-carotene in the oxidation of fats and oils, results are still unclear. Some researchers reported a pro-oxidant action of β-carotene, attributed to the associated increase in the oxygen absorption rate, while other researchers reported an antioxidant effect of β-carotene on the stability of an oil stored in the dark. Various studies have concluded a concentration- and light-dependent behaviour of β-carotene. Yanishlieva et al. (2001) studied the effect of β-carotene (0.001–0.002%) on the room-temperature oxidation of a sunflower oil containing naturally occurring tocopherols and of the same oil stripped of tocopherols. β-Carotene was found to act as a prooxidant in the tocopherol-stripped oil, the effect being greater in the dark than under light conditions. In contrast, carotene increased the stability of oil containing tocopherols exposed to light.

5.7.3

Accelerated ageing of sunflower oil

Lee et al. (2007) determined the peroxide value and the p-anisidine value of regular sunflower oil samples oxidised at different temperatures in the dark, and calculated the corresponding induction periods. The activation energy for the autoxidation of sunflower oil was as high as 19.0 kcal/mol (compared with 17.6 kcal/mol for soybean oil and 12.5 kcal/mol for olive oil). The natural tocopherols were degraded during autoxidation. Results suggest that the induction period decreases with increasing temperature, due to loss of an increasing amount of tocopherols. Marmesat et al. (2009) studied changes in the peroxide value (Figure 5.9) during oxidation of antioxidant-stripped regular and high-oleic (HOSO) sunflower oils stored at 40 °C in the dark. Consistent with the inherent stabilities of both oils, HOSO showed a higher oxidative stability than regular sunflower oil (Table 5.9). These results are consistent with data reported by Martín-Polvillo et al. (2004). Ramírez et al. (2001) examined the effect of light (12 hours in the dark and 12 hours in the light) and temperature conditions on the useful life of a commercial refined regular sunflower oil stored in PET bottles under nitrogen atmosphere. Results showed a strong influence of storage temperature on the estimated shelf-life of those samples stored in the light,

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Vegetable Oils in Food Technology 1200 Regular

1000

Peroxide value

HOSO 800

600

400

200

0 0

50

100

150

200

250

Oxidation time (h) Figure 5.9 Behaviour of the peroxide value of regular and high-oleic (HOSO) sunflower oils during the progress of oxidation at 40 °C in the dark. Source: Marmesat et al. (2009).

amounting to 281 days at 20 °C, and to 91 days at 35 °C. A significantly higher estimated shelf-life of ca. 1140 days was found for the oil stored in the dark at 20 °C. Corbett (2003) determined the AOM values of several high-oleic oils: 40–60 h for HO sunflower, 35–50 h for HO canola, 40 h for HO safflower, 20 h for partially hydrogenated soybean and 15 h for regular sunflower oils. High-oleic sunflower oil showed the highest AOM value, indicating the highest oxidative stability at the assayed temperature. Carelli et al. (2000) reported oxidative stability indices (OSI times) of 12.7 h and 11.8 h for two refined regular sunflower oils containing natural tocopherols. Tabee et al. (2008) reported the OSI times of several vegetable oils containing natural tocopherols. The stabilities of the studied oils were found to decrease in the following order: palm olein > high-oleic rapeseed > refined olive > low-erucic rapeseed > regular sunflower. Allowing for differences in the tocopherol content and composition, the OSI times were consistent with the respective inherent stabilities of the studied oils (Table 5.9).

5.7.4

Stabilisation of sunflower oil by added antioxidants

Carelli et al. (2000) reported the effect of different commercial antioxidants on the oxidative stability of refined regular sunflower oil containing natural tocopherols. Tert-butyl hydroquinone (TBHQ) showed the greatest antioxidant effectiveness, the OSI time increasing by two- or threefold with 50 ppm or 150 ppm additions of TBHQ, respectively. Propyl gallate (PG) also showed a high effectiveness, with a twofold increase in OSI time following the addition of 130 ppm of the antioxidant. Butylated hydroxytoluene (BHT) showed little effect, as the OSI time increased by only 2 hours with the addition of the maximum permissible amount of the antioxidant. Merrill et al. (2008) studied the OSI time at 110 °C of high-oleic oils with added antioxidants and compared the OSI time of regular sunflower oil (5.2 hours; 1170 ppm tocopherols)

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Table 5.11 Natural tocopherol content (mg/kg) of soybean and regular sunflower oils. Tocopherol

Soybean

Sunflower

α-tocopherol β-tocopherol γ-tocopherol δ-tocopherol

120 10 610 260

610 10 30 10

Source: Warner (2005).

with that of high-oleic sunflower oil (16.5 hours; 819 ppm tocopherols). Rosemary extract (1000 ppm), ascorbyl palmitate AP (1000 ppm), TBHQ (200 ppm) and mixed tocopherols (200 ppm) were assayed for their antioxidant effectiveness. The best results were obtained using TBHQ (49.6 hours) or a combination of TBHQ with other antioxidants. However, such combinations only led to slightly improved antioxidant effectiveness. Allam et al. (2002) examined the thermal stability of sunflower oil on the basis of the OSI time (at room temperature and after 1 hour’s heating at 180 °C) with added natural antioxidants (mixed tocopherols and mono-acylglycerol citrate) and commercial antioxidants (BHA, BHT, PG, TBHQ and AP) as well as antioxidant mixtures. The oil with added TBHQ showed the highest thermal stability, while AP led to the lowest stability. Tabee et al. (2008) studied the effect of added α-tocopherol on the OSI time at 110 °C of a regular sunflower oil containing 54.5 mg/100 g of natural tocopherols, 51.3 mg/100 g of which were of α-tocopherol. For additions larger than 1000 ppm, the OSI time was found to decrease, showing a negative effect of a high concentration of α-tocopherol on its antioxidant effectiveness. Different results were reported by Fuster et al. (1998). Stored in the dark, soybean oil has a higher oxidative stability than regular sunflower oil, although soybean oil contains as much as 8–9% of linolenic acid. However, when stored in the light, the oxidative stability of sunflower oil is higher than that of soybean oil – the susceptibility of soybean oil to photo-oxidation being widely reported. The tocopherol profile differs widely for the two oils (Figure 5.6 and Tables 5.10 and 5.11). To test the influence of the tocopherol profile on oxidative stability, Warner (2005) stripped a soybean oil and a regular sunflower oil of all minor constituents and added pure tocopherols in proportions according to the profile of both oils, and in a combined manner. She conducted tests of autoxidative (at 60 °C in the dark) and photo-oxidative stability (at 30 °C in the light). In tests of accelerated autoxidation in the dark, sunflower oil with added tocopherols corresponding to the tocopherol profile of soybean oil was found to be the most stable preparation, while soybean oil with added tocopherols according to the profile of sunflower oil was the least stable combination. However, in tests of photo-oxidation, the addition of tocopherols corresponding to the profile of regular sunflower oil led to a significant improvement in the oxidative stability of both oils compared with the addition of the tocopherols of soybean oil. These results show a significantly higher effectiveness of the tocopherol profile of soybean oil (rich in γ-tocopherol) in inhibiting autoxidation in the dark; whereas the typical tocopherol profile of a regular sunflower oil (rich in α-tocopherol) is more effective in inhibiting photo-oxidation. For some time, synthetic antioxidants such as BHT, BHA and TBHQ were used as food additives. However, these antioxidants are known to have harmful effects on health. As a result, there is a growing trend towards the substitution of synthetic antioxidants by innocuous antioxidants occurring naturally in fruit, vegetable, nut, seed and leaf extracts, among

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other natural sources. Several researchers have studied the antioxidant effect of plant extracts on the stability of regular sunflower oil (De Leonardis et al. 2003; Anwar et al. 2006; Iqbal and Bhanger 2007; Ahn et al. 2008; Iqbal et al. 2008; Chiou et al. 2009). Among the many biological effects of flavonoids, they show antioxidant activity. Marinova et al. (2007) studied the synergic effect of α-tocopherol and myricetin on the stability of a sunflower oil. Myricetin showed a greater and more efficient antioxidant effect than α-tocopherol, while mixtures of both antioxidants consistently showed a synergistic effect. Major phenolic compounds found in sunflower seeds are chlorogenic and caffeic acids along with other compounds occurring in less significant amounts. Marinova et al. (2009) studied the antioxidant effect of pure caffeic and chlorogenic acids on a regular sunflower oil over a wide range of concentrations. While at low concentrations both acids showed the same antioxidant effectiveness, caffeic acid was found to have a greater effectiveness at high concentrations. Using OSI times, Silva et al. (2001) reported the effect of 160 ppm and 200 ppm additions of propyl caffeate, propyl hydrocaffeate, propyl ferulate and propyl isoferulate on the stability of refined regular sunflower oil.

5.8

FOOD USES OF DIFFERENT SUNFLOWER OIL TYPES

Both regular and high-oleic sunflower oil may be used for the preparation of several food products, although the former is generally used because of the price difference between the two types. Other specific uses of sunflower oil are associated with the particular properties of different sunflower oil types, which differ in oil composition.

5.8.1

Use of regular sunflower oil as salad oil and cooking oil

Refined sunflower oil is pale yellow in colour and has a bland flavour. In view of its relatively good oxidative stability, refined regular sunflower oil has several applications at both the domestic and industrial level. In countries where sunflower oil is a common edible oil, it is mainly used as salad dressing and cooking oil. Industrially, sunflower oil is used in frying applications (see Section 5.9.1) and in the manufacture of mayonnaise and oil-based dressings. Although high-oleic sunflower oil is also suitable for these applications, it is used predominantly as frying oil (Section 5.9.2).

5.8.2

Margarine and shortening

Owing to the strong tendency of partially hydrogenated sunflower oil to crystallise in the β form, care should be taken to prevent the appearance of sandiness. The addition of crystal-modifying agents stabilises the metastable intermediate β′ phase. For optimal creaminess, 5–15% of a β′-crystallising partially hydrogenated oil may be included in margarine and certain shortening formulations (Melgarejo 1998). An increase of β′ crystals results from the interesterification of a blend of sunflower oil and completely hydrogenated soybean oil – originally showing a strong tendency to crystallise in the β form. Such observations enabled the formulation of zero-trans margarines of optimal textural properties (Zeitoun et al. 1993). To reduce the sandiness of margarines manufactured with partially hydrogenated sunflower oil, this may be blended with partially hydrogenated cottonseed oil, with the consequent increase in 16-carbon fatty acids. A strong tendency of partially hydrogenated

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cottonseed oil to crystallise in the β′ form favourably affects the crystallisation of the rest of the blend. Rivarola et al. (1987) studied the crystallisation pattern of margarines formulated with blends of partially hydrogenated cottonseed oil, partially hydrogenated sunflower oil and unhydrogenated sunflower oil. An alternative solution to the appearance of sandiness in a partially hydrogenated sunflower oil relies on the addition of emulsifiers, such as saturated and unsaturated fatty acid monoacylglycerols, acting as modifiers of the crystalline structure. Another alternative relies on the addition of sorbitan tristearate at a 0.3% ratio, thereby inhibiting the transition from β′ to β form crystals in a margarine. Sucrose ester may also be used as an inhibitor (Herrera and Márquez Rocha 1996). The conventional partial hydrogenation process results in the formation of a large amount of trans-isomers, which, having considerably higher melting points than their cis-isomers, improve the thermal behaviour and plasticity of the partially hydrogenated oil. However, in the light of nutritionists’ recommendations, research has been aimed at reducing the trans content of margarines. One widely used method consists in the complete hydrogenation of an oil, which does not result in the formation of trans-isomers, followed by interesterification with an unhydrogenated oil. The oxidative stability of the resulting interesterified product is limited by the instability of the unhydrogenated oil. In view of the low content of polyunsaturated fatty acids of high-oleic sunflower oil, it appears as a suitable component for the production of such blends. Ahmadi and Marangoni (2009) obtained a zero-trans shortening by chemical interesterification of a mixture of high-oleic sunflower oil, completely hydrogenated rapeseed oil and completely hydrogenated soybean oil at a weight ratio of 70:17:13. Products based on blends of completely hydrogenated vegetable oils and high-oleic sunflower oil are commercially available.

5.9

FRYING USE OF COMMERCIAL SUNFLOWER OIL TYPES

Both continuous and discontinuous deep-fat frying is normally used for the preparation of food products. Discontinuous frying is used according to consumer demand. A frying oil is exposed to the air as it is heated for relatively short and sometimes occasional cooking periods, and most often with infrequent oil replenishment. Continuous frying, used for the industrial processing of fried and pre-fried foods, usually requires a fast oil turnover, as a large amount of oil is removed with the fried product. The steam generated during the frying process constitutes a protective barrier against air exposure and oxidation. Oil decomposition products absorbed with the frying oil by the product affect not only the sensory and nutritional quality but also the useful life of fried foods. Such products include polar compounds (e.g. triacylglycerol dimers and polymers, di- and monoacylglycerols, free fatty acids and peroxidised compounds).

5.9.1

Frying use of regular sunflower oil

In countries where sunflower oil has a large share of the edible oil consumption market, as with Argentina and Uruguay, regular sunflower oil is commonly used as frying oil. The frying performance and stability of regular sunflower oil have been studied. Some studies are based on simulated frying operations without the incorporation of food products (BarreraArellano et al. 1997). The deterioration of sunflower oil in discontinuous frying processes with the incorporation of foods, mainly potato chips (French fries), was also studied

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(Masson et al. 1997; Bastida and Sánchez-Muniz 2002). Other researchers studied the continuous process using different rates of oil turnover (Cuesta et al. 1993; Cuesta and SánchezMuniz 1998). Also, the frying oil recovered from the fried product was studied (Martín-Polvillo et al. 1996; Masson et al. 2002). Results show that regular sunflower oil rarely reaches the critical value of 25% of polar compounds during continuous frying processes using a high rate of oil turnover, showing the suitability of sunflower oil for this application. The addition of natural antioxidants has been studied with a view to improving the stability of regular sunflower oil. The following preparations have been studied: dried lavender and thyme (Bensmira et al. 2007), coriander extract (Angelo and Jorge 2008) and polyphenolrich olive leaf extract (Chiou et al. 2009).

5.9.2

Frying use of high-oleic sunflower oil

Dobarganes et al. (1993) and Márquez-Ruiz et al. (1999) studied the thermal stability and frying performance of oils obtained from mutant sunflower seeds containing different amounts of oleic acid (see Section 5.2.4). Márquez-Ruiz et al. (1999) compared the performance of regular and high-oleic sunflower oil in continuous and discontinuous potatofrying processes. Results showed (i) a lesser degree of deterioration for high-oleic than for regular sunflower oil during either continuous or discontinuous frying; (ii) a higher stability of products fried in high-oleic sunflower oil than for products fried in regular sunflower oil when stored at 60 °C; (iii) the critical importance of antioxidants in the manufacture of fried products requiring extended storage prior to consumption. Studies on the frying use of high-oleic sunflower oil have been designed along the same lines as those made on the use of regular sunflower oil, and generally include a comparison of both oil types (Niemela et al. 1996; Martín-Polvillo et al. 1996; Jorge et al. 1996; Dobson et al. 1996; Dutta and Appelqvist 1996; Barrera-Arellano et al. 1997; Márquez-Ruiz et al. 1999). Such comparative studies conclude a higher oxidative stability for high-oleic sunflower oil than for the regular type. Several studies report on the deterioration of high-oleic sunflower oil for use in deep-fat frying in either a discontinuous (Márquez-Ruiz et al. 1999) or a continuous manner (Jorge et al. 1996; Niemela et al. 1996; Romero et al. 1998; Márquez-Ruiz et al. 1999). Some thermo-oxidation studies rely on a simulated frying process in the absence of food and air bubbling at 180 °C (Barrera-Arellano et al. 1997). The oil heated in a convection oven or hot plate was also the subject of research (Jorge et al. 1996). Other studies reported on the deterioration of frying oil recovered from the fried foods and on the deterioration of the fried products during storage (Martín-Polvillo et al. 1996; Márquez-Ruiz et al. 1999). The effect of added dimethyl polysiloxane (DMPS; 2 mg/kg) on a frying oil’s performance has been reported (Niemela et al. 1996; Martín-Polvillo et al. 1996; Jorge et al. 1996). DMPS is an anti-foaming silicone forming a monolayer on the oil surface, protecting it against oxidation by air exposure. In continuous frying processes, a steam barrier generated by the food product protects surface oil against oxidation, making the use of DMPS unnecessary. However, DMPS may be used as an effective means of increasing the oxidative resistance of regular and high-oleic sunflower oil in discontinuous frying, where the oil surface is exposed to atmospheric oxygen for extended time periods between successive frying cycles. The oxidative stability of a frying oil may be improved by the addition of tocopherols. High-oleic sunflower oil with added γ-tocopherol was reported to have a good performance in frying studies (Lampi and Kamal-Eldin 1998).

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5.9.3

163

Frying use of mid-oleic sunflower oil

Although mid-oleic sunflower oil is relatively new on the market, its frying use has also been the subject of research. Abidi and Warner (2001) reported on the frying use of regular, high-oleic and mid-oleic sunflower oil for the manufacture of fried potato chips, potato crisps and fresh white-corn tortilla chips. Kleingartner and Warner (2001) summarised several studies conducted by private companies on the frying use of mid-oleic sunflower oil. Kiatsrichart el al. (2003) compared the pan-frying stability of NuSun oil with that of a commercial canola oil (both oils having a similar iodine value) when used for potato frying. Despite the different composition of the two oils (canola oil contains linolenic acid, as opposed to NuSun), they showed a similar pan-frying stability.

5.9.4

Frying use of sunflower oils with a high content of saturated fatty acids

High-palmitic/high-oleic sunflower oil with a low linoleic acid content (Fernández-Martínez et al. 1997; see Section 5.2.4) showed high oxidative and thermo-oxidative stability (Márquez-Ruiz et al. 1999), indicating a good performance of this oil in industrial frying processes. Marmesat et al. (2005) studied the thermo-oxidation of this oil at 180 °C, finding HP HO sunflower oil to have a higher stability against thermo-oxidation than palm olein.

ACKNOWLEDGEMENT Translated from the Spanish by Eduardo Speranza.

REFERENCES Abidi, S.L. (2003) Tocol-derived minor constituents in selected plant seed oils, Journal of the American Oil Chemists’ Society, 80, 327–333. Abidi, S.L. and Warner, K. (2001) Molecular-weight distributions of degradation products in selected frying oils, Journal of the American Oil Chemists’ Society, 78, 763–769. Abramovic, H. and Klofutar, C. (1998) The temperature dependence of dynamic viscosity for some vegetable oils, Acta Chimica Slovenica, 45, 69–77. Ahmadi, L. and Marangoni, A.G. (2009) Functionality and physical properties of interesterified high oleic shortening structured with stearic acid, Food Chemistry, 117, 668–673. Ahn, J.-H., Kim, Y.-P., Seo, E.-M., Choi, Y.-K. and Kim, H.-S. (2008) Antioxidant effect of natural plant extracts on the microencapsulated high oleic sunflower oil, Journal of Food Engineering, 84, 327–334. Ajzenberg, N. (2002) Introducción a la hidrogenación de aceite y su implementación en un proceso supercrítico: Caso del aceite de girasol, Grasas y Aceites, 53, 229–238. Ali, Y. and Hanna, M.A. (1994) Alternative diesel fuels from vegetable oils, Bioresource Technology, 50, 153–163. Allam, S.S.M. and Mohamed, H.M.A. (2002) Thermal stability of some commercial natural and synthetic antioxidants and their mixtures, Journal of Food Lipids, 9, 277–293. Álvarez-Ortega, R., Cantisán, S., Martínez-Force, E. and Garcés, R. (1997) Characterization of polar and nonpolar seed lipid classes from highly saturated fatty acid sunflower mutants, Lipids, 32, 833–837. Angelo, P.M. and Jorge, N. (2008) Antioxidant evaluation of coriander extract and ascorbyl palmitate in sunflower oil under thermoxidation, Journal of the American Oil Chemists’ Society, 85, 1045–1049. Anwar, F., Jamil, A., Iqbal, S. and Sheik, M.A. (2006) Antioxidant activity of various plant extracts under ambient and accelerated storage of sunflower oil, Grasas y Aceites, 57, 189–197.

Gunstone_c05.indd 163

1/21/2011 6:20:58 PM

164

Vegetable Oils in Food Technology

AOCS (1997) Physical and chemical characteristics of oils, fats and waxes, in Official Methods and Recommended Practices of the American Oil Chemists’ Society, AOCS Press, Champaign, IL. Autino, H., Wnuk, F. and Vacca, P. (1993) Historia, presente y futuro de una oleaginosa atractiva: El girasol, Aceites y Grasas, 3, 21–30. Barrera-Arellano, D., Márquez-Ruiz, G. and Dobarganes, M.C. (1997) A simple procedure to evaluate the performance of fats and oils at frying temperatures, Grasas y Aceites, 48, 231–235. Bastida, S. and Sánchez-Muniz, F.J. (2002) Polar content vs. TAG oligomers content in the frying-life assessment of monounsaturated and polyunsaturated oils used in deep-frying, Journal of the American Oil Chemists’ Society, 79, 447–451. Bensmira, M., Jiang, B., Nsabimana, C. and Jian, T. (2007) Effect of lavender and thyme incorporation in sunflower seed oil on its resistance to frying temperatures, Food Research International, 40, 341–346. Bhattacharyya, S. and Reddy, C.S. (1994) Vegetable oils as fuels for internal combustion engines: A review, Journal of Agricultural Engineering Research, 57, 157–166. Bloch, S. (1990) Desarrollos recientes en el desgomado y la neutralización de aceites vegetales, Aceites y Grasas, 1, 27–33. Bockisch, M. (1998) Fats and Oils Handbook, AOCS Press, Champaign, IL. Boukhchina, S., Gresti, I., Kallel, H. and Bézard, I. (2003) Stereospecific analysis of TAG from sunflower seed oil, Journal of the American Oil Chemists’ Society, 80, 5–8. Brevedan, M.I.V., Carelli, A.A. and Crapiste, G.H. (2000) Changes in composition and quality of sunflower oils during extraction and degumming, Grasas y Aceites, 51, 417–423. Cantisán, S., Martínez-Force, E. and Garcés, R. (2000) Enzymatic studies of high stearic acid sunflower seed mutants, Plant Physiology and Biochemistry, 38, 377–382. Carelli, A.A., Bodnariuk, P. and Crapiste, G.H. (2000) Efectividad de los antioxidantes en el aceite de girasol, Aceites y Grasas, 10, 227–231. Carelli, A.A., Frizzera, L.M., Forbito, P.R. and Crapiste, G.H. (2002) Wax composition of sunflower seed oil, Journal of the American Oil Chemists’ Society, 79, 763–768. Chiou, A., Kalogeropoulos, N., Salta, F.N., Efstathiou, P. and Andrikopoulos, N.K. (2009) Pan-frying of French fries in three different edible oils enriched with olive leaf extract: Oxidative stability and fate of microconstituents, LWT-Food Science Technology, 42, 1090–1097. Chobanov, D. and Chobanova, R. (1977) Alterations in glyceride composition during interesterification of mixtures of sunflower oil with lard and tallow, Journal of the American Oil Chemists’ Society, 54, 47–50. Codex Alimentarius: Standard for Named Vegetable Oils Codex-Stan 210-1999. Corbett, P. (2003) It’s time for an oil change! Opportunities for high-oleic vegetable oils, INFORM, 14, 480–481. Coupland, J.N. and McClements, D.J. (1997) Physical properties of liquid oils, Journal of the American Oil Chemists’ Society, 74, 1559–1564. Cuesta, C. and Sánchez-Muniz, F.J. (1998) Quality control during repeated fryings, Grasas y Aceites, 49, 310–318. Cuesta, C., Sánchez-Muniz, F.J., Garrido-Polonio, C., López-Varela, S. and Arroyo, R. (1993) Thermoxidative and hydrolytic changes in sunflower oil used in frying with a fast turnover of fresh oil, Journal of the American Oil Chemists’ Society, 70, 1069–1073. Damiani, P., Cossignani, L., Simonetti, M.S., Santinelli, F. and Monotti, M. (1997) Stereospecific analysis of triacylglycerols from vegetable oils by two procedures – II: Normal and high-oleic sunflower oils, Journal of the American Oil Chemists’ Society, 74, 927–933. De Leonardis, A., Macciola, V. and Di Rocco, A. (2003) Oxidative stabilization of cold-pressed sunflower oil using phenolic compounds of the same seeds, Journal of Scientific Food Agriculture, 83, 523–528. DeMan, J.M. (1992) Chemical and physical properties of fatty acids, in Fatty Acids in Foods and Their Health Implications (ed. C.K. Chow), Marcel Dekker, New York, Chapter 2. Dian, N.L.H.M., Sundram, K. and Idris, N.A. (2006) DSC study on the melting properties of palm oil, sunflower oil, and palm kernel olein blends before and after chemical interesterification, Journal of the American Oil Chemists’ Society, 83, 739–745. Disk, I.D., White, D.A., Carvalho, A. and Gray, D.A. (2006) Tocopherol – an intrinsic component of sunflower seed oil bodies, Journal of the American Oil Chemists’ Society, 83, 341–344. Dobarganes, M.C., Márquez-Ruiz, G. and Pérez-Camino, M.C. (1993) Thermal stability and frying performance of genetically modified sunflower seed (Helianthus annuus L.) oils, Journal of Agricultural Food Chemistry, 41, 678–681. Dobson, G., Christie, W.W. and Dobarganes, M.C. (1996) Changes in molecular species of triacylglycerols during frying, Grasas y Aceite, 47, 34–37.

Gunstone_c05.indd 164

1/21/2011 6:20:58 PM

Sunflower Oil

165

Dubinsky, E. (2008) Utilización del aceite de girasol de alto esteárico como alternativa saludable en la industria de alimentos, Aceites y Grasas, 18, 352–358. Dutta, P.C. and Appelqvist, L.-A. (1996) Sterols and sterol oxides in the potato products, and sterols in the vegetable oils used for industrial frying operations, Grasas y Aceites, 47, 38–47. Erickson, D.R. (2006) Production and composition of frying fats, in Deep Frying: Chemistry, Nutrition, and Practical Applications (ed. M.D. Erickson), 2nd edn, AOCS Press, Urbana, IL, pp. 21–22. Fernández, M.B., Tonetto, G.M., Crapiste, G.H. and Damián, D.E. (2007) Revisiting the hydrogenation of sunflower oil over a Ni catalyst, Journal of Food Engineering, 82, 199–208. Fernández-Martínez, J.M., Mancha, M., Osorio, J. and Garcés, R. (1997) Sunflower mutant containing high levels of palmitic acid in high oleic background, Euphytica, 97, 113–116. Fernández-Moya, V., Martínez-Force, E. and Garcés, R. (2000) Metabolism of triacylglycerol species during seed germination in fatty acid sunflower (Helianthuis annuus) mutants, Journal of Agricultural Food Chemistry, 48, 770–774. Fernández-Moya, V., Martínez-Force, E. and Garcés, R. (2002) Temperature effect on a high stearic acid sunflower mutant, Phytochemistry, 59, 33–37. Fernández-Moya, V., Martínez-Force, E. and Garcés, R. (2005) Oils from improved stearic acid sunflower seeds, Journal of Agricultural Food Chemistry, 53, 5326–5330. Fernández-Moya, V., Martínez-Force, E. and Garcés, R. (2006) Lipid characterization of a high-stearic sunflower mutant displaying a seed stearic acid gradient, Journal of Agricultural Food Chemistry, 54, 3612–3616. Foglia, T.A., Petruso, K. and Feairheller, S.H. (1993) Enzymatic interesterification of tallow-sunflower oil mixtures, Journal of the American Oil Chemists’ Society, 70, 281–285. Fuster, M.D., Lampi, A.-M., Hopia, A. and Kamal-Eldin, A. (1998) Effects of α- and γ-tocopherols on the autooxidation of purified sunflower triacylglycerols, Lipids, 33, 715–722. Garcés, R., Martínez-Force, E., Salas, J.J. and Venegas-Calerón, M. (2009) Current advances in sunflower oil and its applications, Lipid Technology, 21, 79–82. Grompone, M.A. (1991) Propiedades físicas y químicas de las grasas bovinas fraccionadas e interesterificadas, Grasas y Aceites, 42, 349–355. Gunstone, F.D. and Hilditch, T.P. (1945) The union of gaseous oxygen with methyl oleate, linoleate and linolenate, Journal of the Chemical Society, 836–841. Gupta, M.K. (1998) NuSun: The future generation of oils, INFORM, 9,1150–1154. Gupta, M.K. (2002) Sunflower oil, Vegetable Oils in Food Technology: Composition, Properties and Uses (ed. F.D. Gunstone), Blackwell Publishing, Oxford, Chapter 5. Halvorsen, J.D., Mammel, W.C. and Clements, L.D. (1993) Density estimation for fatty acids and vegetable oils based on their fatty acid composition, Journal of the American Oil Chemists’ Society, 70, 875–880. Herrera, M.L. and Márquez Rocha, F.J. (1996) Effects of sucrose ester on the kinetics of polymorphic transition in hydrogenated sunflower oil, Journal of the American Oil Chemists’ Society, 73, 321–325. International Olive Council (2003) COI /T.15/NC N°3/Rev. 1, December 5. Iqbal, S. and Bhanger, M.I. (2007) Stabilization of sunflower oil by garlic extract during accelerated storage, Food Chemistry, 100, 246–254. Iqbal, S., Haleem, S., Akhtar, M., Zia-ul-Haq, M. and Akbar, J. (2008) Efficiency of pomegranate peel extracts in stabilization of sunflower oil under accelerated conditions, Food Research International, 41, 194–200. Jachmanián, I., Gil, M. and Grompone, M.A. (2002) Mejoramiento de las propiedades térmicas y nutricionales de la grasa vacuna uruguaya mediante interesterificación enzimática, Aceites y Grasas, 46, 84–92. Jorge, N., Márquez-Ruiz, G., Martín-Polvillo, M., Ruiz-Méndez, M.V. and Dobarganes, M.C. (1996) Influence of dimethylpolysiloxane addition to edible oils: Dependence on the main variables of the frying process, Grasas y Aceites, 47, 14–19. Keller, W.A. (1995) Sources of oilseeds with specific fatty acid profiles, Development and Processing of Vegetable Oils for Human Nutrition (eds R. Przybylski and B. E. McDonald), AOCS Press, Champaign, IL, Chapter 7. Kiatsrichart, S., Brewer, M.S., Cadwallader, K.R. and Artz, W.E. (2003) Pan-frying stability of NuSun oil, a mid-oleic sunflower oil, Journal of the American Oil Chemists’ Society, 80, 479–483. Kleingartner, L.W. (2002) NuSun sunflower oil: Redirection of an industry, in Trends in New crops and New Uses (eds. J. Janick and A. Whipkey), ASHS Press. Alexandria, VA. Kleingartner, L. and Warner, K. (2001) A look at a new sunflower oil, Cereal Foods World, 46, 399–404. Kövári, K., Dense, J., Kemény, Z. and Recseg, K. (2000) Physical refining of sunflower oil, OCL, 7, 305–308. Lai, O.M., Ghazali, H.M. and Chong, C.l. (1998) Effect of enzymatic transesterification on the melting points of palm stearin-sunflower oil mixtures, Journal of the American Oil Chemists’ Society, 75, 881–886.

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Lampi, A.-M. and Kamal-Eldin, A. (1998) Effect of α- and γ-tocopherols on thermal polymerization of purified high-oleic sunflower triacylglycerols, Journal of the American Oil Chemists’ Society, 75, 1699–1703. Lee, J., Lee, Y. and Choe, E. (2007) Temperature dependence of the autoxidation and antioxidants of soybean, sunflower, and olive oil, European Food Research Technology, 226, 239–246. Liu, H., Przybylski, R., Dawson, K., Eskin, N.A.M. and Biliaderis, C.G. (1996) Comparison of the composition and properties of canola and sunflower oil sediments with canola seed hull lipids, Journal of the American Oil Chemists’ Society, 73, 493–497. Marinova, E., Toneva, A. and Yanishlieva, N. (2007) Synergistic antioxidant effect of α-tocopherol and myricetin on the autoxidation of triacylglycerols of sunflower oil, Food Chemistry, 106, 628–633. Marinova, E.M., Toneva, A. and Yanishlieva, N. (2009) Comparison of the antioxidative properties of caffeic and chlorogenic acids, Food Chemistry, 114, 1498–1502. Marmesat, S., Mancha, M., Ruiz-Méndez, M.V. and Dobarganes, M.C. (2005) Performance of sunflower oil with high levels of oleic and palmitic acids during industrial frying of almonds, peanuts, and sunflower seeds, Journal of the American Oil Chemists’ Society, 82, 505–510. Marmesat, S., Morales, A., Velasco, J., Ruiz-Méndez, M.V. and Dobarganes, M.C. (2009) Relationship between changes in peroxide value and conjugated dienes during oxidation of sunflower oils with different degree of unsaturation, Grasas y Aceites, 60, 155–160. Márquez-Ruiz, G., Garcés, R., León-Camacho, M. and Mancha, M. (1999) Thermoxidative stability of triacylglycerols from mutant sunflower seeds, Journal of the American Oil Chemists’ Society, 76, 1169–1174. Márquez-Ruiz, G., Martín-Polvillo, M., Jorge, N., Ruiz-Méndez, M.V. and Dobarganes, M.C. (1999) Influence of used frying oil quality and natural tocopherol content on oxidative stability of fried potatoes, Journal of the American Oil Chemists’ Society, 76, 421–425. Martínez-Force, E., León, A. and Garcés, R. (2007) Nuevos aceites de girasol: El futuro para una industria alimentaria saludable, Aceites y Grasas, 17, 268–273. Martínez-Force, E., Ruiz-López, N. and Garcés, R. (2009) Influence of specific fatty acids on the asymmetric distribution of saturated fatty acids in sunflower (Helianthus annuus L.) triacylglycerols, Journal of Agricultural Food Chemistry, 57, 1595–1599. Martín-Polvillo, M., Márquez-Ruiz, G. and Dobarganes, M.C. (2004) Oxidative stability of sunflower oils differing in unsaturation degree during long-term storage at room temperature, Journal of the American Oil Chemists’ Society, 81, 577–583. Martín-Polvillo, M., Márquez-Ruiz, G., Jorge, N., Ruiz-Méndez, M.V. and Dobarganes, M.C. (1996) Evolution of oxidation during storage of crisps and French fries prepared with sunflower oil and high oleic sunflower oil, Grasas y Aceites, 47, 54–58. Masson, L., Robert, P., Dobarganes, M.C. et al. (2002) Stability of potato chips fried in vegetable oils with different degree of unsaturation. Effect of ascorbyl palmitate during storage, Grasas y Aceites, 53, 190–198. Masson, L., Robert, P., Romero, N. et al. (1997) Comportamiento de aceites poliinsaturados en la preparación de patatas fritas para consumo inmediato: Formación de nuevos compuestos y comparación de métodos analíticos, Grasas y Aceites, 48, 273–281. Melgarejo, M. (1998) Girasol en Argentina, Aceites y Grasas, 8, 49–52. Merrien, A. (1998) Conociendo el girasol, Aceites y Grasas, 8, 75–80. Merrill, L.I., Pike, O.A., Ogden, L.V. and Dunn, M.L. (2008) Oxidative stability of conventional and higholeic vegetable oils with added antioxidants, Journal of the American Oil Chemists’ Society, 85, 771–776. Muratorio, A., Cabello, R., González, L. and Racca, E. (2003) Composición de ácidos grasos del aceite de girasol obtenido de semillas certificadas sembradas en distintas zonas de la República Argentina. Cosecha 2001–2002, Aceites y Grasas, 13, 430–437. Muratorio, A., Romano, A., González, L. and Kerlakian, C. (2007) Los aceites vegetales argentinos en relación a una propuesta y posterior Normativa Brasileña N° 49, el Codex Alimentarius y la Normativa IRAM. Parte II, Aceites y Grasas, 17, 682–698. Naglic, M., Smidovnik, A. and Koloini, T. (1998) Kinetics and catalytic transfer hydrogenation of some vegetable oils, Journal of the American Oil Chemists’ Society, 75, 629–633. Niemela, J.R.K., Wester, I. and Lahtinen, R.M. (1996) Industrial frying trials with high oleic sunflower oil, Grasas y Aceites, 47, 1–4. Nolasco, S.M., Aguirrezábal, L.A.N., Mateo, C. and Lúquez, J. (2005) Tocoferoles en el aceite de girasol, Aceites y Grasas, 15, 122–128. Osorio, J., Fernández-Martínez, J., Mancha, M. and Garcés, R. (1995). Mutant sunflowers with high concentration of saturated fatty acids in the oil, Crop Science, 35, 739–742.

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Sunflower Oil

167

Pérez-Vich, B., Garces, R. and Fernandez-Martinez, J. M. (2000) Epistatic interaction among loci controlling the palmitic and stearic levels in the seed oil of sunflower, Theoretical Applied Genetics, 100, 105–111. Piqueras, C.M., Tonetto, G., Bottini, S. and Damiani, D.E. (2008) Sunflower oil hydrogenation on Pt catalyst: Comparison between conventional process and homogeneous phase operation using supercritical propane, Catalysis Today, 133–135, 836–841. Prévot, A. (1987) L’huile de tournesol aujourd’hui, Revue Française des Corps Gras, 34, 183–195. Ramírez, G., Hough, G. and Contarini, A. (2001) Influence of temperature and light exposure on sensory shelf-life of a commercial sunflower oil, Journal of Food Quality, 24, 195–204. Rivarola, G., Segura, J.A., Añón, M.C. and Calvelo, A. (1987) Crystallization of hydrogenated sunflowercottonseed oil, Journal of the American Oil Chemists’ Society, 64, 1537–1543. Rodenbush, C.M., Hsieh, F.H. and Viswanath, D.S. (1999) Density and viscosity of vegetable oils, Journal of the American Oil Chemists’ Society, 76, 1415–1419. Rodríguez, A., Castro, E., Salinas, M.C., López, R. and Miranda, M. (2001) Interesterification of tallow and sunflower oil, Journal of the American Oil Chemists’ Society, 78, 431–436. Romero, A., Cuesta, C. and Sánchez-Muniz, F.J. (1998) Effect of oil replenishment during deep-fat frying of frozen foods in sunflower oil and high-oleic acid sunflower oil, Journal of the American Oil Chemists’ Society, 75, 161–167. Rossell, J.B., King, B. and Downes, M.J. (1983) Detection of adulteration, Journal of the American Oil Chemists’ Society, 60, 333–339. Ruiz-Gutiérrez, V., Morgado, N., Prada, J.L., Pérez-Jiménez, F., and Muriana F.J.G. (1998) Composition of human VLDL triacylglycerols after ingestion of olive oil and high oleic sunflower oil, Journal of Nutrition, 128, 570–576. Sánchez M.J.F., González Bello, O.J., Montes, M., Tonetto, G.M. and Damián, D.E. (2009) Pd/Al2O3cordierite and Pd/Al2O3-fecralloy monolithic catalysts for the hydrogenation of sunflower oil, Catalysis Communications, 10, 1446–1449. Siger, A., Nogala-Kalucka, M. and Lampart-Szczapa, E. (2008) The content and antioxidant activity of phenolic compounds in cold-pressed plant oils, Journal of Food Lipids, 15, 137–149. Silva, F.A.M., Borges, F. and Ferreira, M.A. (2001) Effects of phenolic propyl esters on the oxidative stability of refined sunflower oil, Journal of Agricultural Food Chemistry, 49, 3936–3941. Tabee, E., Azadmard-Damirchi, S., Jägerstad, M. and Dutta, P.C. (2008) Effects of α-tocopherol on oxidative stability and phytosterol oxidation during heating in some regular and high-oleic vegetable oils, Journal of the American Oil Chemists’ Society, 85, 857–867. Tonetto, G.M., Sánchez M.J.F., Ferreira, M.L. and Damiani, D.D. (2009) Partial hydrogenation of sunflower oil: Use of edible modifiers of the cis/trans-selectivity, Journal of Molecular Catalysis A: Chemical, 299, 88–92. Topallar, H,, Bayrak, Y. and Iscan, M. (1995) Effect of hydrogenation on density and viscosity of sunflower oil, Journal of the American Oil Chemists’ Society, 72, 1519–1522. Topallar, H., Bayrak, Y. and Iscan, M. (1997) A kinetic study on the autoxidation of sunflower oil, Journal of the American Oil Chemists’ Society, 74, 1323–1327. Turkulov, J., Dimic, E., Karlovic, D. and Vuksa, V. (1986) The effect of temperature and wax content on the appearance of turbidity in sunflower oil, Journal of the American Oil Chemists’ Society, 63, 1360–1363. Turkulov, J., Dimic, E., Karlovic, D. and Vuksa, V. (2000) Efecto de la temperatura y del contenido de ceras en el momento de aparición de turbidez en el aceite de girasol, Aceites y Grasas, 10, 256–259. Warner, K. (2005) Effects on the flavor and oxidative stability of stripped soybean and sunflower oils with added pure tocopherols, Journal of Agricultural Food Chemistry, 53, 9906–9910. Warner, K., Miller, J. and Demurin, Y. (2008) Oxidative stability of crude mid-oleic sunflower oils from seeds with high γ- and δ-tocopherol levels, Journal of the American Oil Chemists’ Society, 85, 529–533. Weisz, G.M., Kammerer, D.R. and Carle, R. (2009) Identification and quantification of phenolic compounds from sunflower (Helianthus annuus L.) kernels and shells by HPLC-DAD/ESI-MS, Food Chemistry, 115, 758–765. Yanishlieva, N.V., Raneva, V.G. and Marinova, E.M. (2001) β-carotene in sunflower oil oxidation, Grasas y Aceites, 52, 10–16. Yen, G.-C., Shao, C.-H., Chen, C.-J. and Duh, P.-D. (1997) Effects of antioxidants and cholesterol on smoke point of oils, Lebensmittel-Wissenschaft und-Technologie, 30, 648–652. Zeitoun, M.A.M., Neff, W.E., List, G.R. and Mounts, T.L. (1993) Physical properties of interesterified fat blends, Journal of the American Oil Chemists’ Society, 70, 467–471.

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6

The Lauric (Coconut and Palm Kernel) Oils

Ibrahim Nuzul Amri

6.1

INTRODUCTION

The term ‘lauric oils’ refers to oils containing high levels of lauric acid (12:0), namely coconut oil (CO), palm kernel oil (PKO), babassu, tukum, murumuru, ouricuri, cohune and some cuphea oils. CO and PKO are commonly traded lauric oils in the international market, while the others are produced for local consumption. These oils, from coconut palm (Cocos nucifera L.) and oil palm (Elaeis guineensis Jacq), grow productively in tropical regions of Asia, Africa and Central and South America. The Philippines and Indonesia are the major producers of CO, while Indonesia and Malaysia are the major producers of PKO. Production and trading aspects of the oils have been elaborated in Chapter 1. This chapter will focus on the characteristics, processing and food applications of CO and PKO. Both oils also have important non-food uses, but these are not included in this book (Gervajio 2005). CO and PKO contain high levels of medium- and long-chain saturated fatty acids. Both oils are rich in lauric acid, but differ in their levels of C8 (caprylic or octanoic), C10 (capric or decanoic) and oleic acids. CO is more saturated than PKO, hence the iodine value of the former is lower than the latter at 6–10 and 14–21 respectively. Lauric oils are used for food and non-food applications. They are used in the confectionery industries and may be blended with C16/18 oils to produce margarine, spreads and shortening. Lauric oils are also used in cosmetics, toiletries and lubricants. This chapter is divided into six sections: introduction, coconut oil, palm kernel oil, processing, food uses and health aspects. The physical and chemical properties and trading specification of the two oils are be discussed separately, but the processing, applications and chemical properties of CO and PKO are discussed together in Sections 6.4, 6.5 and 6.6.

6.2 6.2.1

COCONUT OIL Coconut palm

Coconut palm is productively grown within 20° north and south of the equator, especially along coastal areas (Gunstone and Harwood 2007). There are two types of coconut palm: the tall and the dwarf. The tall coconut palm gives higher oil yields than the dwarf type Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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because the tough copra obtained from the latter makes it unsuitable for commercial purposes. It is planted mainly as an ornamental. The more common tall variety reaches a height of over 30 m and has a lifespan of more than 50 years (Canapi et al. 2005). Typically, fresh coconut kernel contains (% wt) moisture (50), oil (34), ash (2.2), fibre, (3.0), protein (3.5) and carbohydrate (7.3) (Canapi et al. 2005).

6.2.2

Coconut oil

6.2.2.1

Mechanical pressing of copra

The first step in CO extraction is dehulling; that is, cracking the shell to take out the meat or kernel. The kernel contains about 50% moisture and it has to be dried to a moisture content of 6–8% before oil extraction. This can be achieved by drying the kernel under the sun, with direct heat or through the use of hot air. The dried kernel is known as copra and has an oil content of 64%. Traditionally, coconut oil is extracted from the copra by crushing in an expeller, followed by solvent extraction to recover the residual oil from the cake (Canapi et al. 2005). The crude oil is then refined by physical or chemical refining to remove impurities, making it suitable for human consumption and prolonging its shelf-life. In physical refining, the crude oil is firstly pre-treated with 0.05–0.1% aqueous phosphoric acid (85%) and heated to 80–90 °C for 20–30 min, then bleached with a mixture of bleaching clay/activated carbon (10:1 ratio) at 90–95 °C for 20–30 min and finally by deodorisation at 240 °C for 1–1.5 h, with steam injected at the bottom of the column (Canapi et al. 2005). Phospholipids are removed during the pre-treatment. Colour bodies, metal ions, phosphoric acid and other adsorbable impurities are removed during bleaching, along with free fatty acids (FFA) and volatile components. In chemical refining the FFA in the oil is neutralised with sodium hydroxide and removed in a water stream at an early stage.

6.2.2.2

Virgin coconut oil

Virgin coconut oil (VCO) is defined as the oil obtained from the fresh, mature kernel of the coconut by mechanical or natural means, with or without the use of heat, but without chemical refining, bleaching or deodorising. There is virtually no alteration in the nature of the oil and this is suitable for consumption without further processing (Philippine National Standard, PNS 2004). VCO can be produced by dry or wet processes. In the dry process, the fresh kernel is first shredded and dried. Extraction of the oil then leaves a residue of coconut flour. In the wet process, water is added to the shredded kernel and the extraction process is conducted by spinning the wet kernel. The resulting oil/milk mixture can be separated by fermentation or by heat treatment. The partially defatted meat is dried and pressed to extract the remaining oil, while the flake can be used as flour (Philippines Coconut Authority, 2004). Virgin coconut oil is colourless, with a natural fresh coconut scent, and is free from rancid odour or taste. VCO and CO come from the same source (coconut meat), differing only in the way they are processed. Therefore, the characteristics of the two oils are similar, unless otherwise stated. Table 6.1 shows the requirements for VCO according to the Philippine and Malaysian standards. In a study of commercial virgin coconut oil sold in Malaysia and Indonesia, Marina et al. (2009) reported that the fatty acid composition of VCO is comparable to that of CO according to the Codex Standard. The authors conclude that VCO is superior to RBD CO because of its higher content of phenolic compounds and consequently its enhanced oxidative stability.

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Table 6.1

171

Virgin coconut oil specifications according to Philippine and Malaysian standards.

Properties

Philippine

Malaysian

Moisture and volatile content, % FFA (as lauric acid), % Peroxide value, meq/kg oil Food additives Iodine value (Wijs) Contaminants Matter volatile at 105 °C, % Heavy metal, mg/kg Iron (Fe) Copper (Cu)

0.2 max 0.2 max 3.0 max None permitted NM

<0.15 <0.5 <3 NM 5.5–10.6

0.2 max

<0.2

5.0 max 0.4 max

≤5.0 ≤0.4

Lead (Pb) Arsenic (As) FAC by GLC, % 6:0 8:0 10:0 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3

0.1 max 0.1 max

≤0.1 ≤0.1

ND–0.7 4.6–10.0 5.0–8.0 45.1–53.2 16.8–21.0 7.5–10.2 ND 2.0–4.0 5.0–10.0 1.0–2.5 ND–0.2

0.80–0.95 8.00–9.00 5.00–7.00 47.00–50.00 17.00–18.50 7.50–9.50 ND 2.50–3.50 4.50–6.00 0.70–1.50 ND

Source: Philippine National Standard PNS/BAFPS 22:2004 and Malaysian Standard MS 2043:2007. Key: ND = non-detectable NM = not mentioned

6.2.3

Composition

The major component of crude oils is triacylglycerol (TAG) (about 95%), while the minor components comprise free acids, monoacylglycerols, diacylglycerols, phospholipids, free and/or acylated sterols, tocols and hydrocarbons such as alkanes, squalene and carotenes (Gunstone 2006). About 0.5% of crude coconut oil is not saponified by caustic treatment. This unsaponifiable matter consists mainly of tocols, sterols, squalene, color pigments, carbohydrates and odour compounds (lactones) (Canapi et al. 2005). Most of the unsaponifiables are removed during the refining, bleaching and deodorising of crude coconut oil. The crude oil also contains protein, crude fibre and trace amounts of metals such as iron, copper and lead. 6.2.3.1

Fatty acid composition

Table 6.2 shows the fatty acid composition (FAC) of CO. The major fatty acids are lauric (12:0) and myristic acids (14:0), at about 48% and 18% respectively. The difference between CO and PKO is clearly indicated by FAC profile, since CO contains more caprylic (8:0) and capric acids (10:0), but less oleic acid (18:1) than PKO. The high lauric acid content causes the oil to have a sharp melting property.

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Table 6.2

Fatty acid composition (% weight) of coconut oil. Mean§

Fatty acid 6:0 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 18:3 20:0 20:1 Total saturated Iodine value* SMP Protein %** Crude fibre %**

0.4 7.3 6.6 47.8 18.1 8.9 2.7 6.4 1.6

Range§ 0–0.6 4.6–9.4 5.5–7.8 45.1–50.3 16.8–20.6 7.7–10.2 2.5–3.5 5.4–8.1 1.0–2.1

0.1 91.8 8.5 24.1 3.3 4.3

0–0.2 – 6.3–10.6 23.0–25.0 – –

Codex 2009 ND–0.7 4.6–10.0 5.0–8.0 45.1–53.2 16.8–21.0 7.5–10.2 2.0–4.0 5.0–10.0 1.0–2.5 ND–0.2 ND–0.2 ND–0.2 – 6.3–10.6 – – –

Source: Pantzaris and Basiron (2002) and Codex Alimentarius (2009). Notes: * Iodine value calculated from fatty acid composition. ** Francis (2000). § Leatherhead Food Research Association (LFRA) survey, 35 samples. Key: SMP = slip melting point ND = not detected

Coconut oil contains about 92% saturated fatty acid. This makes the crude oil very stable against oxidation. Young (1983) reported stability values of the crude oil at between 30 h and 250 h (active oxygen method, AOM). However, refined oil has less oxidative stability compared to crude oil due to the loss of natural antioxidants during the refining process. Fatty acids with 8 to 12 carbon chains are classified as medium-chain fatty acids (MCFA). The sum of MCFA in CO is 62%, which makes the oil the richest source of MCFA among vegetable oils. Despite being highly saturated, the oil has a relatively low melting point since it contains mainly short- and medium-chain fatty acids. Before the general use of gas liquid chromatography (GLC), the Reichert–Meissl and Polenske values were common tests for CO. These values indicate the level of short- and medium-chain fatty acids. Typical Reichert–Meissl and Polenske values of coconut oil are 8.5 and 10.7, respectively (Gopalakrishnan et al. 1987). These tests are laborious and not very discriminating between CO and PKO in blends with other oils. 6.2.3.2

Triacylglycerol composition

TAG can be separated and quantified by high-performance liquid chromatography (HPLC) or by high-temperature programmed gas chromatography and reported as the ‘equivalent carbon number’ or as the sum of carbon atoms of the three fatty acids attached to the glycerol moiety respectively. Table 6.3 shows the TAG of CO based on the LFRA survey (1989) of 34 specimens, with C32 to C42 as the major TAG. The TAG profile can serve to distinguish

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173

Table 6.3 Triacylglycerol composition by carbon number (% weight) of coconut oil.

28 30 32 34 36 38 40 42 44 46 48 50 52 54

Mean

Range

0.8 3.5 13.4 17.1 19.1 16.5 10.2 7.3 4.1 2.5 2.1 1.5 1.2 0.8

0.5–1.0 2.6–5.0 10.8–17.5 15.6–20.1 18.3–20.6 15.1–18.0 8.4–11.9 5.5–8.8 2.8–4.7 1.6–3.0 1.2–2.6 0.7–2.0 0–2.0 0–1.7

Source: Adapted from Pantzaris and Basiron (2002).

CO from other lauric oils. Even though CO and PKO have similar amounts of C36 triacylglycerols, the two oils can be distinguished since CO contains a higher amount of shortchain (C30–C34) and a lower amount of the long-chain TAG (C44–C54) than PKO. The major C36 TAG is trilaurin, along with minor compounds such as myristic-lauriccapric and palmitic-capric-capric (Pham et al. 1998). Caro et al. (2004) reported the distribution of fatty acids in the TAG between the sn-2 and sn-1/3 positions. The TAG composition of CO used in the study was almost similar to the mean values shown in Table 6.3. The TAG was subjected to chemical deacylation and the resulting partial acylglycerols were separated by preparative thin-layer chromatography and analysed by GLC. The fatty acids at the sn-2 position were lauric (78%), while the major fatty acids at the sn-1/3 positions were lauric (only 33%), myristic (22%) and palmitic (13%). 6.2.3.3

Tocols

The tocols (tocopherols and tocotrienols) are natural antioxidants present in vegetable oils and fats. CO contains low level of tocols, as expected for a highly saturated oil. The major tocol component is α-tocotrienol, ranging from 0–44 mg/kg, while the minor tocols are α-, β- and γ-tocopherols, ranging from 0–17 mg/kg, 0–11 mg/kg and 0–14 mg/kg respectively, as shown in Table 6.4 (Firestone 2006). In addition to these minor tocols, Codex Alimentarius (2009) includes γ-tocotrienol at 0–1 mg/kg. Tocols contribute to the oxidative stability of the oil. In comparison, animal fats have lower oxidative stability than vegetable oils since they contain only trace amount of tocols. Refining of crude CO leads to a reduction of tocol content and consequently reduces the oxidative stability of the oil. Addition of 50–200 ppm α-tocopherol does not increase the stability. It seems that the natural level of tocopherol in the oil is the optimum concentration for the oil stability. The oxidative stability can, however, be improved by adding citric acid to the refined oil as a chelating agent for trace metals (Gordon and Rahman 1991). Other common antioxidants are the synthetic compounds BHA and BHT.

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Vegetable Oils in Food Technology Table 6.4 Tocol content of coconut oil (mg/kg). Codex 2009 α-tocopherol β-tocopherol γ-tocopherol α-tocotrienol γ-tocotrienol Total

ND–17 ND–11 ND–14 ND–44 ND–1 ND–50

Key: ND = not detected

Table 6.5

Ranges and means of sterol content in CO (% of sterol fraction; total in mg/kg).

Cholesterol Brassicasterol Campesterol Stigmasterol Sitosterol Δ5-Avenasterol Δ7-Stigmasterol Δ7-Avenasterol Others Total (mg/kg)

Range

Mean

Codex 2009

0.6–3.0 ND–0.9 7.5–10.2 11.4–13.7 42.0–52.7 20.4–35.7 NS–3.0 0.6–3.0 ND–3.6 470–1110

1.7 0.5 8.7 12.5 46.7 26.6 2.4 1.1 1.1 807

ND–3.0 ND–0.3 6.0–11.2 11.4–15.6 32.6–50.7 20.0–40.7 ND–3.0 ND–3.0 ND–3.6 400–1200

Source: Rossel (2001). Key: ND = not detected NS = not separated

6.2.3.4

Sterols

Sterols in vegetable oils are known as phytosterols, as opposed to zoosterols in animal fats. Phytosterols are the major part of the unsaponifiable fraction. They are beneficial to human health (Gunstone 2006) because of their ability to reduce blood cholesterol levels. Table 6.5 shows the level of various sterols in CO, as compiled by Rossel (2001) and in Codex Alimentarius (2009). Data from Codex covers a wider range of the sterol content than Rossel’s results. The major sterols are campesterol, stigmasterol, β-sitosterol and Δ5-avenasterol, with mean values of 8.7%, 12.5%, 46.7% and 26.6% of total sterols respectively. The total sterol content is 807 mg/kg. 6.2.3.5

Other minor components

Hydrocarbon and lactones are among the other minor components present in CO. The presence of a high level of hydrocarbon makes the oil unfit for human consumption. Contamination with petroleum products may occur during transport or through handling of the oil. Naturally, CO contains 7.7 mg/kg of hydrocarbon (n-alkanes), while crude petroleum and diesel oil contain 72 200 and 148 562 mg/kg respectively (Moffat et al. 1995). The levels in the mineral oils are of a different order of magnitude. Squalene and polycyclic aromatic hydrocarbon content

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Table 6.6

175

Codex (2009) standard for CO.

Chemical and physical characteristics

CO

Relative density 40/20 °C Refractive index (ND/40 °C) Saponification values (mg KOH/g oil) Iodine value Unsaponifiable matter (g/kg)

0.908–0.921 1.448–1.450 248–265 6.3–10.6 ≤15

Quality characteristics for CO and PKO Matter volatile at 105 °C Insoluble impurities Soap content Iron (Fe) Refined Virgin Copper (Cu) Refined Virgin Acid value Refined Virgin Peroxide value Refined Virgin Reichert value Polenske value

0.2% m/m 0.05% m/m 0.005% m/m 1.5 mg/kg 5.0 mg/kg 0.1 mg/kg 0.4 mg/kg 0.6 mg KOH/g oil 4.0 mg KOH/g oil up to 10 meq of active O2/kg oil up to 15 meq of active O2/kg oil 6–8.5 13–18

Source: Codex Standard for Named Vegetable Oils CODEX STAN 210–1999, last revision 2010.

in crude CO are 0.002% (20 ppm) and 0.30% (3000 ppm) respectively (Greyt and Kellens 2000; Gunstone 2000). The pleasant odour and taste of coconut oil are largely due to δ- and γ-lactones, which are present in trace quantities (Young 1983). γ-Valerolactone is considered to be responsible for the characteristic taste of coconut oil (Leffingwell & Associates 1999).

6.2.4

Properties

The chemical and physical characteristics of a vegetable oil are important for quality control, standardisation and trading purposes. The common parameters to characterise crude CO are free fatty acids (FFA), iodine value (IV), moisture and impurites (M&I), refractive index (RI), specific gravity (SG), saponification value (SV) and unsaponifiable matter (US). For refined CO, the common parameters are colour, peroxide value (PV), slip melting point (SMP) and solid fat content (SFC). These values reflect the authenticity and quality of the oil and serve as a guideline to distinguish CO from other oils. The Codex (2009) standard for crude/virgin and refined CO is shown in Table 6.6 and the Malaysian standard (1987) is shown in Table 6.7. 6.2.4.1

Iodine value

Iodine value (IV) is the number of grams of iodine reacting with 100 g of oil. It can also be calculated from fatty acid composition by fitting the unsaturated fatty acid content into a formula. The IV is a measure of unsaturation and consistency for unhydrogenated fats.

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Table 6.7

Malaysian standard MS 239 (1987): Requirement for coconut oil.

Characteristics

Crude Grade 1

FFA (as lauric) (%) max Moisture & insoluble impurities (%) max Iodine value (Wijs) Colour (5¼″) Lovibond cell, max Refractive index at 40 °C Specific gravity at 30/30 °C Saponification value (mg KOH/g) Unsaponifiable matter (%) max

1.0 0.50 7.5–10.5 3R 1.4480–1.4490 0.915–0.920 248–264 0.8

Refined Grade 2 3.5 * * 4R * * * *

0.1 0.10 * 1.5R * * * 0.5

Note: * Same as for grade 1.

There is a strong correlation between the IV, SMP and SFC of non-hydrogenated fats of the same species. A correlation applies also to hydrogenated oils, provided they have been processed under the same selectivity conditions. According to Codex Alimentarius (2009), the range for IV of CO is from 6.3 to 10.6, while Malaysian Standard (1987) defined a narrower range, from 7.5 to 10.5. The low IV is due to the low content of unsaturated fatty acid (8%) in this highly saturated fat. 6.2.4.2

Melting point

The slip melting point (SMP) of a fat is defined as the temperature at which a column of fat in an open capillary tube moves up the tube when it is subjected to controlled heating in a water bath. Unlike pure substances with sharp melting points, fats are mixtures of TAG and generally exhibit a range of melting temperatures. However, this is not the case for CO. It melts relatively sharply due to the high content of short and medium fatty acids in the oil. SMP is the most common tool to measure the consistency of oils and fats. The range of SMP for CO is 23–25 °C, with a mean value of 24.1 °C (Table 6.2). 6.2.4.3

Solid fat content

Solid fat content (SFC) is another measure of consistency that indicates the amount of solid TAG in oils and fats and is determined by nuclear magnetic resonance. It gives a complete melting profile of an oil or fat at various temperatures. CO contains 36% SFC at 20 °C and melts completely at 25 °C (Rossel 1985). In another study by Zhang et al. (2005), the SFC of coconut oil at 20 °C was 30.3% and it was fully melted at 30 °C, but the authors did not measure the SFC of the oil at 25 °C. This parameter is used for quality control purposes in modified fats to assess the properties of food products, such as hardness and mouth feel. It is an important analytical tool for spread and for confectionery products. 6.2.4.4

Other physical characteristics

Other physical characteristics of CO, such as boiling point, heat of combustion, heat of fusion, specific heat, surface tension and viscosity, are shown in Table 6.8. These characteristics are essential to engineers in designing a mill or refinery plant. The engineers should

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177

Miscellaneous physical properties of CO and of trilaurin.

Parameter

Value

Boiling point (lauric acid) at 1 mm Hg 760 mm Hg Heat of combustion Heat of fusion (trilaurin) 46.3 °C Specific heat (trilaurin) 66 °C Surface tension at 20 °C 80 °C 100 °C Vapour pressure (trilaurin) at 188 °C 244 °C Viscosity (trilaurin) at 60 °C 70 °C 80 °C

130.2 298.9 9020 cal/g 46.2 cal/g 0.510 cal/g 33.4 dyne/cm 28.4 dyne/cm 24.0 dyne/cm 0.001 mm Hg 0.05 mm Hg 13.59 cP 10.30 cP 8.09 cP

Source: Wan (2000).

Table 6.9

MEOMA specification for crude and refined CO: For export. Crude CO

FFA (as lauric acid) Moisture & impurities Iodine value (Wijs) Colour (5¼″ Lovibond cell)

Refined CO

Grade 1

Grade 2

1.0% max 0.5% max 7.5–10.5

3.5% max 0.5% max 7.5–10.5

0.1% max 0.1% max 7.5–10.5 1.5 Red max

Source: Handbook of Malayan Edible Oil Manufacturers’ Association 2006/2007, Kuala Lumpur, Malaysia.

know the viscosity of an oil to determine the appropriate diameter of pipes and power needed to pump the oil. Relative density and refractive index are shown in Table 6.6.

6.2.5

Trade specifications

Trade specifications are related to the quality parameters of oils and fats and are part of commercial contracts. This is to ensure that the oils and fats are traded within quality ranges that are acceptable to both buyers and sellers. Sometimes buyers ask for higher-quality products with a different specification. When it is possible to cater for a special request, the production cost will be higher and would be granted only for a large order sold at a premium price. Table 6.9 shows a trade specification prepared by the Malayan Edible Oil Manufacturers’ Association (MEOMA) 2006/07 for crude and refined CO, which includes FFA, moisture and impurities, iodine value and colour. Crude oils are categorised into two grades, differing in FFA content. Grade 1 with lower FFA content is of higher quality than Grade 2. Other parameters are the same. Colour is not part of the specification for crude oil, but it is included in Malaysian Standard (Table 6.7). The colour of crude oil is yellowish,

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expressed as 3 Red on the Lovibond Tintometer scale, while the refined oil should be colourless or is allowed to have a maximum 1.5 Red.

6.3

PALM KERNEL OIL

6.3.1

Palm kernel oil

6.3.1.1

Oil palm

The oil palm, Elaeis guineensis Jacq., originated in West Africa along the Guinea coast and was spread to other tropical regions by Portuguese explorers in the fifteenth century (Abraham 2000). Currently, it is widely grown in Malaysia, Indonesia, South America, Africa and South Pacific countries. It grows well within 5° north and south of the equator, with rainfall of over 2000 mm per year spread evenly throughout the year, adequate sunshine of over 2000 h per year and moderately high temperatures of 25–33 °C (Basiron 2005). It has a single stem that grows to 35 m in height and is topped by leaves typically 7 m in length. The fruit matures about six months after pollination. An adult palm tree is capable of producing 12 bunches per year. Even though the tree can live up to 200 years, its economic life span is 25–30 years (Chong 2000). 6.3.1.2

The palm fruit

The reddish orange palm fruit, which is oval or pear shaped, about 3 × 5 cm and weighs up to 30 g, grows in bunches in the axil of the leaves. These fresh fruit bunches (FFB) contain around 1500 fruits each and weigh 20–30 kg. The FFB grow and mature progressively on the tree and are harvested at intervals of 10–14 days. The outer fleshy mesocarp gives the PO, while the kernel, which is inside a hard shell, gives PKO. The kernel constitutes about 45–48% (by weight) of the nut. 6.3.1.3

Palm kernels

Harvested FFB are quickly transported to a palm oil mill where they are sterilised with steam to inactivate enzymes and microorganisms. Sterilisation also disintegrates the bunches, loosens the fruits and facilitates the separation of the nuts. The fruits are then conveyed to a screw press to obtain PO from the fleshy mesocarp. The pressure of the screw press is set not to break the nuts. The nuts are separated from the fibres and then cracked to remove the shell. The kernels are separated from the shells by hydrocyclone or clay bath. At this stage, the moisture content of the kernels is about 20%, which permits mould growth and could lead to a rapid increase in the FFA of palm kernel oil. Ideally, therefore, the kernels should be dried to a moisture level of 7% for safe storage and delivery without deterioration by mould growth. The oil content in dried kernels is around 50% (Basiron 2005). A typical composition of Malaysian palm kernel is shown in Table 6.10. 6.3.1.4

Palm kernel oil

Crude palm kernel oil (CPKO) is a co-product of crude palm oil (CPO), which is the primary oil derived from oil palm. The oil is extracted from the dried kernels by mechanical screw press, by solvent extraction or by a combination of both methods. With a screw press,

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Table 6.10 Typical composition of Malaysian palm kernel and palm kernel cake (% by weight).

Oil content Protein Crude fibre Moisture Ash Carbohydrate

Kernel

Cake

49.0 8.3 8.1 6.5 2.0 26.1

7.9 14.8 16.7 6.4 3.9 50.3

Source: Tang and Teoh (1985).

double pressing is usually required to ensure efficient oil extraction. The resultant cake left after the oil extraction is used as animal feed, since it is rich in nutrient and protein (Table 6.10). Generally, PKO production is about 10–12% of PO output (O’Brien 2000a). Even though the two oils come from the same fruit, they are entirely different in fatty acid composition. The national average oil extraction rate for CPKO in Malaysia for 2009 was 46.05%, an increase of 0.23% from 2008 (MPOB 2010). CPKO can be refined by a chemical or physical process. The latter is more widely used due to its cost effectiveness, efficiency and minimal effluent treatment (Tang 2005). The first stage in physical refining is pre-treatment or degumming of CPKO with phosphoric acid solution (80–85%). The oil is heated to 90–95 °C and continuously dosed with 0.02–0.05% of the concentrated phosphoric acid, with a resident time of 20–30 min. For the bleaching stage, 0.5–1% bleaching clay is added and the temperature is raised to 95–110 °C with a retention time of 30 min. The bleached oil is then filtered to remove the clay and subjected to deodorisation, where the temperature is further raised to 220–240 °C. Steam is supplied into the oil and the process is conducted under vacuum.

6.3.2

Composition

6.3.2.1

General composition

The main composition of crude oils is TAG at about 95%, with the rest made up of free acids, monoacylgycerols, diacylglycerols, phospholipids, free and/or acylated sterols, tocols and hydrocarbons such as alkanes, squalene and carotenes. Oils from different sources differ in fatty acid and triacylglycerol composition and in the detailed composition of the various minor components. The fatty acid composition and properties of PKO are similar to those of CO. The main difference is that PKO has slightly less of the short-chain fatty acids (caprylic and lower) and more oleic acid. Typically the IV is 18.5 against 8.5 for CO. The heavy preponderance of a single saturated fatty acid, combined with low levels of unsaturation, gives the oil its steep melting profile. Besides triacylglycerols and FFA, crude PKO contains about 0.8% unsaponifiable matter such as sterols, tocols, triterpene alcohols, hydrocarbons and lactones. Even after full hydrogenation, the melting point of PKO does not rise much above mouth temperature and fractionation gives a palm kernel stearin (PKS) with sharper melting. Fats melting sharply just below mouth temperature leave a clean, cool, non-greasy sensation on the palate, difficult for any of the common non-lauric oils to match. Cocoa butter is the only

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Table 6.11

Fatty acid composition of CPKO (%) by GLC.

Fatty acid 6:0 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 Total saturated Iodine value

Range

Mean

Codex 2009

MS 80

0.2–0.4 3.2–4.7 2.9–3.5 45.4–49.8 15.4–17.2 7.9–9.3 1.9–2.3 13.7–17.0 2.1–2.9 – 17.0–20.0

0.3 3.6 3.3 48.0 16.7 8.5 2.1 14.9 2.5 82.6 17.8

ND–0.8 2.4–6.2 2.6–5.0 45.0–55.0 14.0–18.0 6.5–10.0 1.0–3.0 12.0–19.0 1.0–3.5 – 14.1–21.0

0.3 3.6 3.3 48.0 16.7 8.5 2.1 14.9 2.5 82.6 17.8

Sources: Ibrahim et al. (2003); Codex Alimentarius 2009; MS 80:2009 (draft).

other natural fat with similar properties, but it is an expensive speciality fat and is not included among the 17 major oils and fats in world trade. Malaysian Standard MS80:1987 for palm kernel oil has been revised and will be replaced with MS80:2009. The revised standard is in the final stage of getting approval from the relevant authority and is expected to be in force from June 2010. Discussion of palm kernel oil here is made with reference to this revised standard. 6.3.2.2

Fatty acid composition

Table 6.11 shows the FAC of CPKO from Malaysia based on a one-year survey conducted by Ibrahim et al. (2003). A total of 174 samples were analysed for FAC and other parameters. Lauric acid is the most abundant fatty acid in CPKO, followed by myristic and oleic acids. The fatty acid compositions obtained from the survey have been incorporated into the Malaysian Standard (MS 80:2009) (draft) for crude palm kernel oil. Generally, FAC values in the revised standard are narrower than the current standard and this leads to slightly lower mean values. However, the difference is not significant. Lauric acid content in CPKO is very similar to CO, but the oleic acid content is twice that in CO and consequently the iodine value is higher. As for medium-chain fatty acids, the content is lower in CPKO than in CO, 55% and 62% respectively. All FAC values are within the Codex Alimentarius 2009 range. Lauric oils are very stable against oxidation due to the low level of unsaturated acids and particularly of polyunsaturated acids. 6.3.2.3

Triacylglycerol composition

Medium-chain triacylglycerols are medium-chain fatty acid esters of glycerol. As mentioned earlier, lauric oils are rich in MCFA and this makes the oils a good source of mediumchain triacylglycerols. This is not the same as the commercial product MCT (medium-chain triglycerides) made from coconut-derived octanoic and decanoic acids. CPKO contains about 23% of C36 triacylglycerols (Table 6.12), with trilaurin as the major component (Tang et al. 1995). CPKO contains more long-chain triacylglycerols (C42–C50) than CO due to the higher amount of total C18 acids in the former. Triacylglycerols containing saturated and unsaturated C18 acids are eluted together when analysed by gas chromatography. CPKO contains less MCT (C30–C34) than CO.

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Table 6.12 Triacylglycerol composition by carbon number (%). TAG 28 30 32 34 36 38 40 42 44 46 48 50 52 54

Range

Mean

0.1–1.9 0.8–2.1 5.6–6.8 7.7–9.5 19.1–26.2 14.8–18.5 9.3–10.8 8.3–10.1 5.9–7.2 4.7–5.8 4.8–6.9 1.5–3.4 1.7–3.3 1.8–3.7

0.55 1.25 6.34 8.43 23.33 16.96 9.79 9.10 6.56 5.14 5.79 2.30 2.17 0.45

Source: Tang et al. (1995).

Table 6.13

Tocols content of PKO (mg/kg).

α-tocopherol β-tocopherol γ-tocopherol α-tocotrienol γ-tocotrienol Total

Range

Codex 2009

ND–44 ND–248 ND–257 ND–trace ND–60 ND–257

ND–44 ND–248 ND–257 ND ND–60 ND–260

Source: Rossel (2001). Key: ND = not detected

6.3.2.4

Tocols

The range of tocol levels in PKO is shown in Table 6.13. Major tocols are β- and γ-tocopherols, up to 248 and 257 mg/kg respectively, while the others are present as minor tocols. The high content of β- and γ-tocopherols in PKO could possibly be due to migration of palm oil into the kernels (Rossel 2001). The content of these two tocol isomers are about 20 times higher than in CO. α-Tocotrienol was reported to be the major tocol in CO (see Table 6.4), but its presence is hardly detected in PKO. Tocopherols are oil-soluble antioxidants that also show vitamin E activity. α-Tocopherol shows the greatest vitamin E activity and γ-tocopherol has the greatest antioxidant activity. 6.3.2.5

Sterols

All oils and fats contain small amounts of unsaponifiable matter, of which sterols are a major component. Cholesterol is the predominant sterol in animal fats. In vegetable oils the sterols consist of a mixture collectively known as phytosterols. β-Sitosterol is the major

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182

Table 6.14

Sterol content of PKO (% of sterol fraction; total in mg/kg).

Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmasterol Δ7-Avenasterol Others Total (mg/kg)

Range

Mean

Codex 2009

1.0–3.7 ND–0.3 8.4–12.7 12.3–16.1 62.6–70.4 4.0–9.0 ND–2.1 ND–1.4 ND–2.7 792–1187

1.7 0.1 10.0 13.7 67.0 6.2 0.6 0.1 0.7 1025

0.6–3.7 ND–0.8 8.4–12.7 12.0–16.6 62.6–73.1 1.4–9.0 ND–2.1 ND–1.4 ND–2.7 700–1400

Source: Rossel (2001). Key: ND = not detected

Table 6.15

Composition of sterol in crude PKO and RBD PKO (mg/kg). CPKO

Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmasterol Δ7-Avenasterol Others Total (mg/kg)

RBD PKO

Range

Mean

Range

Mean

14.7–20.9 0–1.2 95.5–125.3 143.8–179.3 658.0–825.2 45.0–51.6 2.0–4.9 1.1–2.4 13.8–31.8 985–1228

18.5 0.8 106.9 158.6 742.5 49.3 3.1 1.8 20.9 1104

12.7–14.3 0–1.7 76.8–80.6 118.3–130.5 561.5–627.0 29.9–38.4 0–2.7 0–1.7 17.4–30.4 827–906

13.7 0.6 78.9 124.3 599.2 33.2 1.5 1.0 23.2 875

Source: Tang (1996).

sterol present in PKO, followed by stigmasterol and campesterol (Table 6.14). PKO contains more β-sitosterol but less Δ-5-avenasterol than CO. The two oils contain about the same amount of other types of sterols. Each refining step has the effect of reducing the total sterols present. The bleaching stage is responsible for the greatest reduction in the sterol content due to adsorption on the bleaching earth. Physical refining or the deodorisation step in a chemical refining process also reduces the content of free sterols in the oil (Gordon 2002), as shown in Table 6.15. 6.3.2.6

Hydrocarbons

Vegetable oils naturally contain low concentrations of n-alkanes with odd carbon numbers ranging from 15 to 33 (McGill et al. 1993). The presence of exceptionally high levels of hydrocarbon indicates that the oil has been contaminated with an outside source hydrocarbon, for example from petroleum. Furthermore, hydrocarbon content can be used in the

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Table 6.16

183

Draft Malaysian standard for palm kernel oil (2009): Identity characteristics.

Characteristics Refractive index, nD 40 °C Apparent density, g/ml at 40 °C Saponification value, mg KOH/g Unsaponifiable matter, % by mass Slip melting point, °C Iodine value, Wijs Solid fat content (% by pulsed NMR) 5 °C 10 °C 15 °C 20 °C 25 °C 30 °C Total carotenoids as carotene, mg/kg

Range

Mean

1.4500–1.4518 0.904–0.905 243–249 0.30–0.39 27.3–28.0 16.5–18.75

1.4509 0.0002 245 0.03 27.6 17.8

68.0–76.8 61.6–71.2 50.7–60.0 34.2–45.5 10.2–21.5 nil 3.3–8.1

72.8 67.6 55.7 40.1 17.1 nil 6.0

Source: Draft Malaysian Standard MS 80:2009, Department of Standards, Kuala Lumpur.

detection of processed oil in oil labelled virgin or unrefined, since the action of bleaching earth at temperatures over 100 °C leads to the generation of steroidal hydrocarbons (steradienes) by dehydration of the sterols (Rossell 2001). Tan and Kuntom (1994) reported that the range of natural hydrocarbon content in crude PKO is 0.6 to 7.1 ppm. 6.3.2.7

Other minor components

Unsaponifiable matter content in PKO is 0.30–0.39% (mean value is 0.33%). The range of total carotenoids that are part of the unsaponifiable matter is 4.3–11.8 mg/kg, with a mean value of 7.6 mg/kg (MS80:2009). The range of unsaponifiable matter and carotenoid levels as defined in the revised standard is narrower than the current standard (MS80:1987), and consequently leads to a lower mean value for these two components at levels of 0.30% and 7.6 mg/kg respectively.

6.3.3

Properties

6.3.3.1

Chemical and physical characteristics

Several oils and fats are available in the international market and it is important to distinguish them based on their unique chemical and physical characteristics. Quality control laboratories often use the characteristics specified by national and international standards to ensure that an oil conforms to its specification. As already noted, the Malaysian standard for palm kernel oil has been revised and the final draft is in the process of getting approval from the relevant authority (see Table 6.16). This section will highlight the changes in the revised standard. Fatty acid composition has been mentioned in Section 6.3.2.2 and the Codex standard for PKO is given in Table 6.17. Before the invention of GC, Reichert and Polenske values were commonly applied to distinguish between PKO and CO. Both values for PKO are lower than those for CO.

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Table 6.17

Codex standard for palm kernel oil.

Chemical and physical characteristics Relative density 40/20 °C Refractive index (ND40 °C) Saponification values (mg KOH/g oil) Iodine value Unsaponifiable matter (g/kg) Reichert value Polenske value

Range 0.899–0.914 1.448–1.452 230–254 14.1–21.0 ≤10 4–7 8≠12

Source: Codex Standard for Named Vegetable Oils CODEX STAN 210–1999, last revision 2010. Note: Quality characteristics apply to both CO and PKO (see Table 6.5).

6.3.3.2

Iodine value

Table 6.16 shows the draft Malaysian Standard, which defines a narrower range of IV, 16.5– 18.75, than both Codex (Table 6.17) and the earlier version of the Malaysian standard (16.2– 19.2). The IV of PKO (14.1–21.0) is higher than that of CO (6.3–10.6) due to the higher level of oleic acid in the former. PKS is a premium product. The IV of the PKO can serve as an indicator of the yields of stearin and olein in fractionation. It was reported that an increase of IV of 1.9 units in PKO caused a reduction in stearin yield by 11% (Soon 1991). In general, a CPKO of low IV is preferred since this gives a higher yield of stearin. 6.3.3.3

Melting point

Oils with higher percentages of saturated fatty acids generally have higher melting points. The melting point of PKO (27.6 °C) is slightly higher than that of CO (24.1 °C). Like coconut oil, PKO has a relatively sharp melting point because the saturated fatty acids that constitute about 83% of its composition have a relatively small difference between their melting points (only about 20 °C), whereas palm oil can have more than 70 °C difference between fatty acid melting points. A sharp melting point is an advantage when formulating food products that are expected to melt quickly in the mouth, such as candy coatings, candy centres, icings and other confectionery. The range of melting points as defined by the Malaysian standard is rather narrow (Table 6.16). 6.3.3.4

Solid fat content

The SFC profile for PKO indicates that the oil has sharp melting behaviour, especially from 20 to 30 °C (Table 6.14). The SFC is reduced by more than 50% as the temperature is raised from 20 to 25 °C, and melting is complete at 30 °C. The melting profile of PKO is slightly different from CO, since the latter totally melts at 25 °C. 6.3.3.5

Other physical characteristics

For other characteristics of PKO, refer to lauric acid and trilaurin in Table 6.8.

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Table 6.18

185

MEOMA (2006/2007) and the Malaysian Standard (2009) for PKO for exports. MEOMA CPKO

FFA, as lauric acid, % max Moisture and impurities, % max Iodine value (Wijs) Colour (5¼″ Lovibond cell), max

Table 6.19

5.0 0.5 19.0 –

MS 80

RBD 0.1 0.1 19.0 1.5 Red

CPKO

RBD

5.0 0.5 16.5–18.75 8.0 Red

0.1 0.1 16.5–18.75 1.5 Red

MEOMA (2006/2007) parameters for other PKO products for export.

Crude palm kernel olein

Crude palm kernel stearin

RBD palm kernel olein

RBD palm kernel stearin

Parameter

Value

FFA (as lauric acid) Moisture & impurities Iodine value (Wijs) FFA (as lauric acid) Moisture & impurities Iodine value (Wijs) FFA (as lauric acid) Moisture & impurities Iodine value (Wijs) Colour (5¼″ Lovibond cell) FFA (as lauric acid) Moisture & impurities Iodine value (Wijs) Colour (5¼″ Lovibond cell)

5.0% max 0.5% max 21 min 5.0% max 0.5% max 8 max 0.1% max 0.1% max 19 max 1.5 Red max 0.1% max 0.1% max 8 max 1.5 Red max

Note: Iodine values are at time of shipment.

6.3.4

Trade specifications

Specifications of oil and fats defined by the governing body of a country serve as a basis for trading purposes. Even though the specification is not mandatory, it is common practice to include it as part of a sales contract. Table 6.18 shows the quality requirements for PKO according to MEOMA and the Malaysian Standard, while Table 6.19 shows the requirements for other PKO products. All quality parameters as specified by MEOMA and the draft Malaysian Standard are similar except for iodine value, which is lower in the latter.

6.4 6.4.1

PROCESSING Fractionation

Fractionation is a process to separate the low and high melting triacylglycerols in edible vegetable oils and fats, which are known as olein and stearin respectively. Three types of fractionation are normally practised, namely dry, detergent and solvent. PKS is enriched with lauric and myristic acid, while caprylic, capric and the unsaturated fatty acids remain in the olein fraction. PKS is an excellent material for a lauric-based cocoa butter substitute due to the proximity of the melting point to that of cocoa butter.

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Table 6.20

Triacylglycerol composition of palm kernel olein and palm kernel stearin.

TAG (%)

26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56

Palm kernel olein

Palm kernel stearin

Range

Mean

Range

Mean

0–0.1 0.2–0.5 1.3–1.8 6.6–8.4 8.4–10.2 16.3–19.8 10.1–14.0 6.1–8.7 8.1–9.9 7.3–8.2 6.1–7.1 7.0–12.7 1.7–3.8 2.7–3.9 3.4–4.7 0–0.2

0 0.3 1.3 7.8 9.3 18.3 12.7 7.6 9.3 7.8 6.5 8.3 3.1 3.4 4.2 0.1

0–0.1 0–0.3 0.4–0.9 2.8–3.7 6.1–6.9 25.9–29.2 23.4–25.7 14.3–16.0 8.1–10.1 4.9–5.7 2.3–3.6 1.1–3.4 0.4–1.6 0.3–1.5 0.5–1.1 0.0

0 0.1 0.5 3.3 6.5 27.5 24.8 15.2 9.2 5.2 3.0 2.4 0.9 0.7 0.8 0.0

Source: Tang et al. (1995).

Table 6.21 Fatty acid composition, iodine value and slip melting point of palm kernel olein and palm kernel stearin. FAC (%)

6:0 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 20:0 IV (Wijs) SMP (°C)

Palm kernel olein

Palm kernel stearin

Range

Mean

Range

Mean

0.2–0.4 3.6–5.0 3.2–4.5 42.1–46.3 12.3–15.5 7.4–10.6 1.8–2.7 14.6–21.3 2.6–3.8 0–0.2 20.6–25.3 23.1–25.4

0.3 4.3 3.6 44.7 14.0 8.3 2.3 19.2 3.3 0.1 23.0 23.6

0–0.1 1.5–2.3 2.5–2.9 54.8–58.2 21.1–24.1 7.2–8.6 1.3–2.2 4.6–6.8 0.6–1.1 0–0.2 5.8–8.1 31.8–33.1

0.1 1.9 2.7 56.6 22.4 8.0 1.8 5.6 0.8 0.1 7.0 32.2

Source: Tang et al. (1995).

Triacylglycerol and fatty acid composition and other characteristics of refined palm kernel olein (PKOo) and PKS are shown in Tables 6.20 and 6.21 respectively, while Figure 6.1 shows the solid fat content of modified palm kernel oil products. The IV of PKS is much lower than PKO (7 and 19 respectively) and subsequently leads to a higher melting point (32.2 °C and 27.6 °C respectively). PKS is usually hydrogenated to further improve its melting profile. The MEOMA trading specifications for PKS and PKOo are shown in Table 6.19.

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187

100 90

Solid fat content (%)

80 70

RBD PKOo RBD PKOs HPKOs HPKOo HPKO CB

60 50 40 30 20 10 0 0

10

20

30

40

Temperature (8C) Figure 6.1 Solid fat content of modified palm kernel products. Sources: Palm kernel products: Tang (2000); CB (cocoa butter): Metin and Hartel (2005).

The yield of stearin from fractionation of CO is less than that from PKO and this causes the product to be more expensive. The range of IV for coconut stearin is 4–7, similar to PKS, and the SMP is 28 °C, which is lower than palm kernel stearin. Since coconut stearin is softer than PKS it is used as a confectionery filling fat (Gunstone and Harwood 2007).

6.4.2

Hydrogenation

Hydrogenation results in the direct addition of hydrogen to the double bonds in the fatty acid chains of the triacylglycerol of oils. For hydrogenation to take place, gaseous hydrogen, liquid oil and nickel catalyst are placed in a specially designed reaction vessel under controlled temperature and pressure. The purpose of hydrogenation is to change the functional characteristics of the naturally occurring fats to those required for specific applications. This process also provides taste and smell stability and enhances the shelf-life of unsaturated products (Anderson 2005). Through hydrogenation, the IV of CO is reduced from 7–10 to 0–2. This consequently leads to an increase in the SMP from 24–26 °C to 32–34 °C (Gunstone and Harwood 2007). Hydrogenated CO is suitable for whipped topping due to its steep melting property. Wan (2000) reported that fully hydrogenated CO is predominantly crystals in the β form. Hydrogenated palm kernel oil can be used in toffees as an alternative to more expensive dairy butter, either completely or partially. Hydrogenated palm kernel oil is also a good general-purpose coating fat. Hydrogenated PKOo contains higher solid fat than RBD PKOo (Figure 6.2), which shows that the hydrogenation process greatly enhances the solid fat content. The melting profile of HPKS is steeper than RBD PKS and both contain high amounts of solid fat at 30 °C, but are almost totally melted at 35 °C, which is similar to cocoa butter. This rapid melting close to body temperature gives a cool taste

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Vegetable Oils in Food Technology 70

Solid fat content (%)

60 50 Blend1 EIE1

40

Blend2 EIE2

30 20 10 0 0

10

20

30

40

Temperature (8C) Figure 6.2 Enzymatic interesterification of POs/CO (75/25) blend* and POs/PKOo blend (70/30).** Sources: * Zhang et al. (2001); ** Zainal and Yusoff (1999). Key: Blend = before interesterification EIE = after interesterification

in the mouth. Triacylglycerol composition and fatty acid composition of hydrogenated PKO products are shown in Tables 6.22 and 6.23, respectively. IV and SMP are included in Table 6.23. The SMP of the hydrogenated fats do not differ so much due to the sharp melting characteristics of the fats. SFC plots show a better melting profile for the hydrogenated oils.

6.4.3

Interesterification

Interesterification is a modification technique for oils and fats that alters their physical properties by rearranging (in a random or specific manner) the distribution of fatty acids on the glycerol backbone without changing fatty acid profiles. During interesterification, fatty acids are exchanged within (intra) and among (inter) triacylglycerols until a thermodynamic equilibrium is reached (Xu et al. 2006). The rearrangement of the fatty acids in the glycerol backbone produces a new lipid with different TAG that have chemical and physical properties sometimes deemed to be superior to those of the starting material. Interesterification can be conducted by chemical and enzymatic reactions. The former is a mature technology dating back to the 1920s, while the latter is still a relatively new technology. Even though research on enzymatic interesterification started in the 1970s (Dijkstra 2007), only a few companies have adopted the technology, including Karlshamns (Sweden), ADM (USA), KMT (Ukraine) and Flora Danica (Argentina) (Biotimes 2006). The advantage of interesterification over partial hydrogenation is that the former does not produce any trans fats.

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Table 6.22 TAG

28 30 32 34 36 38 40 42 44 46 48 50 52 54

189

Triacylglycerol composition of hydrogenated PKO products (%). Hydrogenated PKO

Hydrogenated PKOo

Hydrogenated PKOs

Range

Mean

Range

Mean

Range

Mean

0.2–0.3 1.0–1.3 5.9–6.2 7.9–8.8 19.2–22.1 16.0–18.3 9.0–10.2 9.0–9.7 6.6–7.4 4.9–5.9 5.0–6.6 2.5–2.8 2.4–2.8 2.2–3.6

0.2 1.2 6.1 8.4 21.9 16.5 9.6 9.4 7.0 5.4 6.0 2.7 2.6 3.0

0.2–0.3 1.2–1.7 6.1–8.0 7.4–10.0 16.2–19.1 11.9–13.9 7.3–8.7 8.1–10.3 7.6–8.9 6.3–8.0 7.5–9.8 2.9–4.6 2.5–5.2 3.4–5.0

0.3 1.5 7.2 8.8 18.0 12.7 7.9 9.3 8.1 6.7 8.2 3.5 3.6 4.1

0.1–0.3 0.4–0.8 3.1–3.6 5.8–6.7 24.9–28.1 20.1–25.9 13.2–16.0 8.3–12.6 4.7–6.0 2.3–4.9 1.9–4.2 0.7–2.3 0.5–1.4 0.5–1.3

0.1 0.5 3.2 6.2 27.0 24.9 15.3 9.2 5.1 3.0 2.6 1.1 0.9 0.9

Source: Tang et al. (1995).

Table 6.23 FAC

6:0 8:0 10:0 12:0 14:0 16:0 18:0 18:1 18:2 20:0 IV (Wijs) SMP (°C)

Fatty acid composition, IV and SMP of hydrogenated palm kernel products (%). Hydrogenated PKO

Hydrogenated PKOo

Hydrogenated PKS

Range

Mean

Range

Mean

Range

Mean

0–0.2 2.9–3.6 2.8–3.4 46.2–48.8 16.5–17.1 7.9–9.2 15.2–19.0 1.4–4.3 0–0.2 0–0.2 1.7–4.4 31.9–35.3

0.1 3.3 3.1 47.8 16.8 8.3 16.6 3.7 0.1 0.2 4.0 33.9

0.1–1.4 3.4–4.7 3.0–3.6 40.8–46.0 12.1–15.7 8.0–9.9 13.9–26.5 0.5–12.0 0–0.2 0–0.3 0.5–10.7 31.5–39.9

0.3 4.1 3.3 43.5 13.8 8.6 19.5 6.7 0.1 0.1 6.4 34.2

0–0.2 1.5–2.4 2.4–2.9 54.8–58.8 20.8–23.7 7.4–10.3 4.6–11.5 0–0.1 0–0.2 0–0.3 0.1–1.2 32.7–35.6

0.1 1.8 2.7 55.8 22.1 8.2 9.0 0.2 0.0 0.1 0.39 33.7

Source: Tang et al. (1995).

POs and PKO are highly suitable components of margarines, since the former provides the required SFC without the need for hydrogenation while the latter gives the right mouth feel and melting characteristics. The two oils are normally blended and subjected to interesterification to form the margarine hardstock. Other ingredients are added to the hardstock as part of the margarine formulation, namely antioxidant, colour, flavour, water and liquid oil. The effects of enzymatic interesterification of palm stearin/CO blend and palm stearin/ PKOo blend are shown in Figure 6.2. The interesterification has altered the SFC and caused the interesterified products to have a lower SFC than the non-esterified blend, which is a common effect of interesterification.

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6.5

FOOD USES

Palm kernel oil and coconut oil are mainly used for food purposes, about 83% and 61% respectively of the total usage (Gunstone and Harwood 2007). A large portion of the remaining usage is in the oleochemical industry. The food applications of lauric oils include margarine and spread formulation, shallow frying, cocoa butter substitutes, filling creams, ice creams, non-dairy whipping creams and filled milks.

6.5.1

Frying

Coconut oil is commonly used as a frying oil in tropical countries, especially in the Philippines and India (Rossel 2001; Coconut Development Board), where it is a local preference and a local product. However, it is only suitable for shallow frying and is mainly used for domestic purposes. It is not suitable for industrial frying because of its high content of lauric and other fatty acids with fewer than 14 carbon atoms. During industrial frying, the moisture in the fried food causes hydrolysis of the glycerol esters and liberation of free fatty acids. Medium-chain acids are quite volatile and cause excessive smoke development (Rossel 2001). Kochhar (2001) reported that lauric-rich oils gave unsatisfactory frying at temperatures of 180–200 °C. It is advised that lauric oil should not be mixed with palm oil or other fats with long-chain fatty acids for frying purposes, since this would lead to foaming. This problem may be associated with the heterogenous triacylglycerol structure and could be overcome by interesterification (Dijkstra 2007). In another study on interesterification of PKOo/palm oil blend, the interesterified product had a good miscibility and consequently diminished the eutectic interaction between the two oils (Dian et al. 2006).

6.5.2

Margarine

Margarine was patented in 1869 by the French chemist Hippolyte Mège Mouriès. Commercial production was initiated in the 1870s by the Dutch company Jurgens (Shukla 2005). Since its invention, the margarine manufacturing process has changed significantly from being open to the air, wet and lengthy to enclosed, dry and relatively short. Cycle times – from ingredient mixing to producing the finished packed product – have dropped from 60 hours in the early 1900s to 10 minutes by 2000 (Robinson 2005). In Europe, it is common to find lauric oils as part of margarine formulation. However, lauric oils are not used in the United States because of their high saturate content and the intense negative public opinion about ‘tropical’ oils generated by consumer groups in that country in the late 1980s. There are several types of margarine available in the market, namely table margarine, bakery margarine, puff pastry margarine and reduced fat spread. Previously, partially hydrogenated fats were commonly used in margarine formulation, but the current trend is not to use partially hydrogenated fats due to health issues associated with trans acids. Lauric oils are added into margarine formulation because of their sharp melting property. Margarine producers can predict the amount of solid fat that a particular oil or fat will contribute at specific temperatures by applying statistical software. It was reported that coconut oil would have a strong positive solid contribution at 10 °C and a negative

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Table 6.24

191

Margarine formulation containing lauric oils. SFC (%) 10 °C

Table, soft tub IE (POs:PKOo:RSO 40:20:40) Table/kitchen wrapped IE(POs:PKOo:SFO 60:20:20)* IE (POo:PKO 80:20) IE (POs:PKO:RSO 50:20:30) Industrial POs:PO:PKO 10:60:30 Puff pastry POs:PKO 80:20

20 °C

30 °C

35 °C

40 °C

26.3

8.6

1.4

–

–

33.7 40.4 42.0

18.9 20.1 24.0

7.1 5.9 9.3

– 1.8 5.2

– – –

55.4

27.9

13.7

9.1

8.4

57.8

31.1

16.8

12.2

10.1

Source: Yusoff and Dian (1995). Note: Slip melting point 38.5 °C. Key: IE = interesterified PKO = palm kernel oil PKOo = palm kernel olein PO = palm oil POo = palm olein POs = palm stearin RSO = rapeseed oil SFO = sunflower oil

coefficient at 21.1 °C (Chrysan 2005). Furthermore, lauric oils are a source for mediumchain triacylglycerols, which are more rapidly absorbed, cleared from the blood and metabolised than the long-chain fatty acids (de Deckere and Verschuren 2000). Table 6.24 shows examples of margarine formulation using lauric oils.

6.5.3

Medium-chain triacylglycerols

The acronym MCT (medium-chain triglycerides or medium-chain triacylglycerols) is used loosely. It is most widely used to describe a product made from glycerol and caprylic (8:0) and capric (10:0) acids, obtained by distillation of coconut fatty acids. Because of their low molecular weight, MCT oils are easily absorbed in the digestive tract, are used immediately as energy sources in the body and thus avoid being stored in adipose tissue. These properties make them useful ingredients in sports foods, infant foods and in clinical nutrition (enteral/ parenteral food). Another source of MCT, also containing lauric and myristic acids, is palm kernel distillate, a by-product of refining crude palm kernel oil (Low et al. 2007). MCT oils are different from other fats since they have a lower calorie content than the former (Bach et al. 1996). MCT oils are stable against oxidation since they contain saturated fatty acids. This makes the oils suitable to be used as releasing agents to prevent baked food from sticking to the pan in the baking industry (Idris and Samsudin 2005). MCT oils are often sprayed on to products such as spices, mixes and starch to avoid an unpleasant taste. They can also be used as safe lubricants in machines used in the food industry.

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6.5.4

Speciality fats: Cocoa butter substitutes

Cocoa butter contains almost equal amounts of palmitic, stearic and oleic acids and melts at 32 °C to 35 °C (Gunstone and Harwood 2007). The high price and inconsistent supply of cocoa butter have forced confectioners to look for alternatives. The alternative fat should have a sharp melting characteristic, be physically stable after crystallisation and have a bland flavour. Lauric oils are suitable for this purpose. PKO contains more oleic acid than CO and this makes PKO a better substitute for speciality fats, since it can be hydrogenated to give a wider range of melting points. PKS, obtained by fractionation of PKO, can be used as a cocoa butter substitute (CBS) due to high solid content, which gives a good snap and resistance to fat bloom. The melting property of palm kernel stearin can be further improved to match cocoa butter by complete hydrogenation to an iodine value of less than one (Senanayake and Shahidi 2005). Palm kernel oil can be used as a good ‘chocolate-coating’ fat for ice cream and deepfrozen confections because the coating formed is hard, yet elastic and not brittle. Hydrogenated PKO can be interesterified and blended with palm oil products to modify the melting property and solid fat content profile to suit certain applications (Aini and Yusoff 2000).

6.5.5

Filling creams

Filling creams are applied between layers of cakes, wafers or biscuits. The requirements for the creams are that they melt easily in the mouth and be fully molten at body temperature. Filling creams can be produced from hydrogenation of a blend containing palm kernel olein and palm kernel oil, or through interesterification of palm kernel olein blended with palm stearin. Lauric-based fillings do not require any tempering. In addition to the melting characteristic, other important requirements for filling creams are adhesion to the biscuit shell and their rate of setting. Lauric-based filling creams adhere better to the shell and set faster than non-lauric fillings. This will cause fewer problems in transporting the biscuits on conveyors and during packaging, since the biscuits do not come apart or slide off the filling.

6.5.6

Non-dairy creamer

Non-dairy creamers are substitutes for cream or fresh milk in coffee or tea and impart a desirable colour change and cream-like flavour to the food or beverage. Non-dairy creamers should provide whitening power, give body and impart viscosity. There are three types of non-dairy creamers: powder, liquid and frozen. The powder form is the most popular due to ease of handling, transportation and storage. Hydrogenated PKO of a melting point of 38 °C is suitable for the powder type. The high melting point ensures that the creamer does not melt during transportation. Hydrogenated PKO with a melting point of 35 °C is suitable for the liquid type of creamer. A formulation for non-dairy creamer is shown in Table 6.25. Fully hydrogenated CO (IV <2) is also suitable for non-dairy creamer. Non-dairy creamer has a better shelf-life and flavour stability than dairy creamer (Hammond 2006). Milk or dairy creamer has a delicate flavour and has small impact on strong beverages such as coffee and tea. Therefore, non-dairy creamer is easily accepted by consumers, since the difference in the taste between the non-dairy and the dairy creamer is hardly noticeable.

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Table 6.25

193

Formulation of a non-dairy creamer.

Ingredients Hydrogenated PKO (38 °C) Sodium caseinate Maltodextrin (28DE) Emulsifier Stabiliser (carrageenan) Dipotassium phosphate Water, colour, flavour

% 16.0 6.0 26.8 0.5 0.03 0.3 up to 100

Source: Teah et al. (1990); the Malayasian Palm Olive Board.

6.5.7

Non-dairy whipping cream

Fat components greatly influence the whipping properties and stability of whipping cream. Alternative fats to traditional dairy creams should be semi-solid at 5 °C, have good structure stability at ambient temperature and melt in the mouth (Aini and Yusoff 2000). Nesaretnam et al. (1993) reported that an interesterified blend of hydrogenated PKO/POs at a 66:34 ratio gave a good whipping performance, stability and mouth feel.

6.5.8

Non-dairy cheese

Processed cheese is made by blending natural cheese with water, colouring agent and emulsifier. The blend is then subjected to heating and agitating to produce a homogeneous mixture. Non-dairy cheese has been formulated by the Malaysian Palm Oil Board comprising of 30% palm oil and 70% palm kernel olein.

6.5.9

Filled milk

Milk has a very delicate flavour, therefore the primary criterion in selecting vegetable oil for filled milk is low flavour. For countries where fresh milk is not readily and cheaply available, it would be economical to import skimmed milk powder and reconstitute it with vegetable oils. The vegetable oils should contain only a low amount of linoleic acid in order to have a good oxidative stability. CO and PKO are frequently used due to their high oxidative stability, good mouth feel, low melting point and bland taste. The extremely stable fully hydrogenated CO, PKO and PKOo are normally used for filled milk.

6.5.10

Ice cream

Ice cream is an intricate mixture of fat globules, ice crystals and liquid water containing dissolved sugars, protein and air. It contains about 10% to 18% fat (Table 6.26). CO and PKO (with or without modification) are the best fats for non-dairy ice cream due to their high SFC at 0 °C, low melting point and bland taste. These characteristics are important to ensure that the ice cream is in the frozen state when in a freezer but melts quickly in the mouth.

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Table 6.26

Composition of ice cream mix.

Component

% weight

Water Sugar Fat Non-fat milk solids Stabilisers/ emulsifiers

60–64 13–18 10–18 7.5–11.5 0.3–0.5

Source: Dijkstra (2007).

6.5.11

Toffees and caramels

Toffees and caramels are confections made by heating sugar together with milk solids. Traditionally, these confections are made from milk fat derived from condensed milk. However, due to economic reasons, the milk fat may be replaced with vegetable fats. Hydrogenated lauric oils are commonly used due to their sharp melting point, setting properties and long shelf-life. The choice of melting point of the hydrogenated lauric oils depends on the climatic conditions. A melting point of 32–35 °C is recommended for temperate countries, while 35–45 °C is desirable for warmer countries (Lees and Jackson 1973). Vegetable fat is usually incorporated into the ingredients to adjust the texture, hardness and chewiness and to give a good mouth feel (Guelfi 1989).

6.6

HEALTH ASPECTS

Even though lauric oils contain more than 80% saturated fatty acids, it should be remembered that most of the saturated fatty acids are short- and medium-chain fatty acids (60%). These oils can be used with or without modification such as fractionation, hydrogenation or interesterification. If hydrogenation is required, the oils will be fully hydrogenated and no trans fats will then be present. Furthermore, caprylic, capric and lauric acids are considered to have little effect on plasma cholesterol levels (Mensink 1993). Lauric acid, the major fatty acid, is metabolised by a different pathway and is not deposited in adipose tissue. Another point worth considering is that lauric oils generally form only a small part of food formulation. Only a small amount of lauric oils is added to food that requires sharp melting fats, with the consequence that only minute amounts of lauric acid are consumed.

REFERENCES Abraham, G. (2000) Oilseeds and vegetable oils, in Encyclopedia of Food Science and Technology, Vol. 1 (ed F.J. Francis), 2nd edn, John Wiley & Sons, Inc., New York, pp. 1745–1755. Aini, I.N. and Yusoff, M.S.A. (2000) Food uses of palm and palm kernel oils, in Advances in Oil Palm Research, Vol 2 (eds Y. Basiron, B.S. Jalani and K.W. Chan), Malaysian Palm Oil Board, Kuala Lumpur, pp. 968–1035. Anderson, D. (2005) A primer on oils processing technology, in Bailey’s Industrial Oil and Fat Product, Edible Oil and Fat Products: Processing Technologies, Vol 5 (ed F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 1–56. Bach, A.C., Ingenbleek, Y. and Frey, A. (1996) The usefulness of dietary medium-chain triglycerides in body weight control: Fact or fancy? Journal of Lipid Research, 37, 708–726.

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195

Basiron, Y. (2005) Palm oil, in Bailey’s Industrial Oil and Fat Product, Edible Oil and Fat Products: Edible Oils, Vol. 2 (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 333–429. Biotimes, Novozymes, Denmark, www.novozymes.com. Canapi, E.C., Agustin, Y.T.V., Moro, E.A., Pedrosa, E.J. and Bendaño, M.L.J. (2005) Coconut oil, in Bailey’s Industrial Oil and Fat Products, Edible Oil and Fat Products: Edible Oils, Vol. 2 (ed F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 123–147. Caro, Y., Turon F., Villeneuve P., Pina M. and Graille J. (2004) Enzymatic synthesis of medium-chain triacylglycerols by alcoholysis and interesterification of copra oil using a crude lipase preparation, European Journal of Lipid Science Technology, 106, 503–512. Chong, Y.H. (2000) Palm oil, in Encyclopedia of Food Science and Technology, Vol. 1 (ed. F.J. Francis), 2nd edn, John Wiley & Sons, Inc., New York, pp. 1839–1852. Coconut Development Board, India, http://coconutboard.nic.in. Codex Alimentarius (2009) Food and Agricultural Organization of the United Nations. Chrysan, M.M. (2005) Margarines and spreads, in Bailey’s Industrial Oil and Fat Products, Edible Oil and Fat Products: Products and Applications, Vol. 4 (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 33–82. de Deckere, E.A.M. and Verschuren, P.M. (2000) Functional fats and spreads, Functional Foods: Concept to Product (eds Glenn R. Gibson and Christine M. Williams), Woodhead Publishing Limited, Cambridge, pp. 234–257. Dian, N.L.H.M., Sundram, K. and Idris, N.A. (2006) DSC study on the melting properties of palm oil, sunflower oil, and palm kernel olein blends before and after chemical interesterification, Journal of the American Oil Chemists’ Society, 83, 739–745. Dijkstra, A.J. (2007) Modification processes and food uses, in Lipid Handbook (eds F.D. Gunstone, J.L. Harwood and A.J. Dijkstra), 3rd edn, CRC Press, Boca Raton, FL, pp. 263–353. Firestone, D. (2006) Characteristics of oils and fats of plant origin, in Physical and Chemical Characteristics of Oils, Fats and Waxes (ed D. Firestone), 2nd edn, AOCS Press, Champaign, IL, pp. 1–57. Gervajio, G.C. (2005) Fatty acids and derivatives from coconut oil, in Bailey’s Industrial Oil and Fat Products, Industrial and Nonedible Products From Oils and Fats, Vol. 6 (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 1–56. Gopalakrishnan, N., Narayanan, C.S., Mathew, A.G. and Arumughan, C. (1987) Lipid composition of coconut cake oil, Journal of the American Oil Chemists’ Society, 64, 539–541. Gordon, M.H. (2002) Analysis of minor components as an aid to authentication, in Oils and Fats Authentication (ed. M. Jee), Blackwell Publishing Ltd., Oxford, pp. 143–155. Gordon, M.H. and Rahman, I.A. (1991) Effect of processing on the composition and oxidative stability of coconut oil, Journal of the American Oil Chemists’ Society, 68, 574–576. Greyt, W.D. and Kellens, M. (2000) Refining practice, in Edible Oil Processing (eds W. Hamm and R.J. Hamilton), Sheffield Academic Press, Sheffield, pp. 79–128. Guelfi, R. (1989) Critical factors in caramel quality, in PMCA Production Conference, 42nd edn, PMCA, Bethlehem, PA, pp. 132–135. Gunstone, F.D. (2000) Composition and properties of edible oils, in Edible Oil Processing (eds W. Hamm and R.J. Hamilton), Sheffield Academic Press, Sheffield, pp. 1–33. Gunstone, F.D. (2006) Vegetable sources of lipids, in Modifying Lipids for Use in Food (ed. F.D. Gunstone), Woodhead Publishing Limited, Cambridge, pp. 11–27. Gunstone, F.D. and Harwood, J.L. (2007) Occurrence and characterization of oils and fats, in Lipid Handbook (eds F.D. Gunstone, J.L. Harwood and A.J. Dijkstra), 3rd edn, CRC Press, Boca Raton, FL, pp. 37–141. Hammond, E. (2006) Filled and artificial dairy products and altered milk fats, in Modifying Lipids for Use in Food (ed. F.D. Gunstone), Woodhead Publishing, Cambridge, pp. 462–487. Ibrahim, N.A., Kuntom, A., Sue, T.T. and Lin, W.L. (2003) Current status of Malaysian crude palm kernel oil characteristics, Oil Palm Bulletin, 47, 15–27. Idris, N.A. and Samsudin, S. (2005) Edible uses of palm kernel oil and its products, in Palm Kernel Products: Characteristics and Applications (eds Y. Basiron, A. Darus, M.A. Ngan and C.K. Weng), Malaysian Palm Oil Board, Kuala Lumpur, pp. 70–94. Kochhar, S.P. (2001) The composition of frying oils, in Frying: Improving Quality (ed. J.B. Rossell), Woodhead Publishing, Cambridge, pp. 87–114. Lees, R. and Jackson, E.B. (1973) Caramels, toffees and fudges, in Sugar Confectionery and Chocolate Manufacture, Leonard Hill, Aylesbury, pp. 191–208. Leffingwell & Associates (1999) www.leffingwell.com.

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Low, C.T., Mohamad, R., Tan, C.P. et al. (2007) Lipase-catalyzed production of medium-chain triacylglycerols from palm kernel oil distillate: Optimization using response surface methodology, European Journal of Lipid Science Technology, 109, 107–119. Malaysian Palm Oil Board (2010) Overview of the Malaysian Oil Palm Industry 2009, Malaysian Palm Oil Board, Kuala Lumpur. MS 239 (1987) Specification for coconut oil, Department of Standards Malaysia, Cyberjaya. MS 2043 (2007) Coconut oil specification, Department of Standards Malaysia, Cyberjaya. MS 80 (2009) Palm kernel oil specification (2nd rev) (draft), Department of Standards Malaysia, Cyberjaya. Marina, A.M., Che Man, Y.B., Nazimah, S.A.H. and Amin, I. (2009) Chemical properties of virgin coconut oil, Journal of the American Oil Chemists’ Society, 86, 301–307. McGill, A.S., Moffat, C.F., Mackie, P.R. and Cruickshank, P. (1993) The composition of alkanes in edible oils, Journal of the Science of Food Agriculture, 61, 357–362. Mensink, R.P. (1993) Effects of individual saturated fatty acids on serum lipids and lipoprotein concentrations, American Journal of Clinical Nutrition, 57(s), 711s–714s. MEOMA (2006/2007) Handbook 2006–2007, Malayan Edible Oil Manufacturers’ Association, Malaysia. Metin, S. and Hartel, R.W. (2005) Crystallization of fats and oils, in Bailey’s Industrial Oil and Fat Products, Edible Oil and Fat Products: Chemistry, Properties and Health Effects, Vol. 1 (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 45–76. Moffat, C.F., Cruickshank, P., Brown, N.A. et al. (1995) The Concentration and Composition of n-Alkanes in Edible Oils, Report No. TD2736, August, CSL Food Science Laboratory, Torry, UK. Nesaretnam, K., Robertson, N., Yusof, B. and MacPhie, C.S. (1993) Application of hydrogenated palm kernel oil and palm stearin in whipping cream, Journal of the Science of Food Agriculture, 61, 401–407. O’Brien, R.D. (2000a) Fats and oils: An overview, in Introduction to Fats and Oils Technology (eds R.D. O’Brien, W.E. Farr and P.J. Wan), 2nd edn, AOCS Press, Champaign, IL, pp. 1–19. O’Brien, R.D. (2000b) Fats and oils processing, in Introduction to Fats and Oils Technology (eds R.D. O’Brien, W.E. Farr and P.J. Wan), 2nd edn, AOCS Press, Champaign, IL, pp. 90–107. Pantzaris, T.P. and Basiron, Y. (2002) The lauric oil (coconut and palmkernel) oils, in Vegetable Oils in Food Technology: Composition, Properties and Uses (ed. F.D. Gunstone), Blackwell Publishing Ltd., Oxford, pp. 157–202. Pham, L.J., Casa, E.P., Gregorio, M.A. and Kwon, D.Y. (1998) Triacylglycerols and regiospecific fatty acid analysis of Philippine seed oil, Journal of the American Oil Chemists’ Society, 75, 807–811. PNS/BAFPS 22 (2004) Virgin Coconut Oil, Philippines Coconut Authority, www.cocoscience.com. Robinson, D. (2005) The history of margarine, INFORM, 16, 135–138. Rossel, J.B. (1985) Fractionation of lauric oils, Journal of the American Oil Chemists’ Society, 62, 385–390. Rossel, J.B. (2001) Factors affecting the quality of frying oils and fats, in Frying: Improving Quality (ed. J.B. Rossell), Woodhead Publishing Limited, Cambridge, pp. 115–164. Senanayake, S.P.J.N. and Shahidi, F. (2005) Modification of fats and oils via chemical and enzymatic methods, in Bailey’s Industrial Oil and Fat Products, Edible Oil and Fat Products: Specialty Oils and Oil Products, Vol. 3 (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 555–584. Shukla, V.K.S. (2005) Margarine and baking fats, in Healthful Lipids (eds C.C. Akoh and O.M. Lai), AOCS Press, Champaign, IL, pp. 665–684. Soon, W. (1991) Specialty fats versus cocoa butter, Atlanto Sdn Bhd, Petaling Jaya. Tan, Y.A. and Kuntom, A. (1994) Hydrocarbons in crude palm kernel oil, Journal of AOAC International, 77, 67–73. Tang, T.S. (1996) Sterol composition of palm kernel oil and its fractions, in Proceedings of the PORIM International Palm Oil Congress, Kuala Lumpur, pp. 349–354. Tang, T.S. (2000) Composition and properties of palm oil products, in Advances in Oil Palm Research (eds Y. Basiron, B.S. Jalani and K.W. Chan), Malaysian Palm Oil Board, Kuala Lumpur, pp. 845–894. Tang, T.S. (2005) Processing of palm kernels, in Palm Kernel Products: Characteristics and Applications (eds Y. Basiron, A. Darus, M.A. Ngan and C.K. Weng), Malaysian Palm Oil Board, Kuala Lumpur, pp. 19–69. Tang, T.S., Chong, C.L. and Yusoff, M.S.A. (1995) Malaysian palm kernel stearin, palm kernel olein and their fractionated products, PORIM Technology, 16, 1–19. Tang, T.S. and Teoh, P.K. (1985) Palm kernel oil extraction – the Malaysian experience. Journal of the American Oil Chemists’ Society, 62, 254–258. Teah, Y.K., Sahri, M.M. and Hassan, A.H. (1990) Palm products in coffee whiteners, Palm Oil Developments, 13, 1–3.

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Wan, P.J. (2000) Properties of fats and oils, in Introduction to Fats and Oils Technology (eds Richard D. O’Brien, Walter E. Farr and Peter J. Wan), 2nd edn, AOCS Press, Champaign, IL, pp. 20–48. Xu, X., Guo, Z., Zhang, H., Vikbjerg, A.F. and Damstrup, M.L. (2006) Chemical and enzymatic interesterification of lipids for use in food, in Modifying Lipids for Use in Food (ed. F.D. Gunstone), Woodhead Publishing, Cambridge, pp. 234–272. Young, F.V.K. (1983) Palm kernel and coconut oils: Analytical characteristics, process technology and uses, Journal of the American Oil Chemists’ Society, 60, 374–379. Yusoff, M.S.A. and Dian, N.L.H.M (1995) Trans free formulation: A short review, Palm Oil Development, 22, 33–40. Zainal, Z. and Yusoff, M.S.A. (1999) Enzymatic interesterification of palm stearin and palm kernel olein, Journal of the American Oil Chemists’ Society, 76, 1003–1008. Zhang, H., Jacobsen, C. and Adler-Nissen, J. (2005) Storage stability of margarines produced from enzymatically interesterified fats compared to margarines produced by conventional methods. I. Physical properties, European Journal of Lipid Science Technology, 107, 530–539. Zhang, H., Xu, X., Nilsson, J. et al. (2001) Production of margarine fats by enzymatic interesterification with silica-granulated Thermomyces lanuginosa lipase in a large-scale study, Journal of the American Oil Chemists’ Society, 78, 57–64.

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7

Cottonseed Oil

Michael K. Dowd

7.1

INTRODUCTION

Cottonseed oil is derived from the seeds of the cotton plant (Gossypium sp). Of the 40–45 species of the Gossypium genus, four species, G. hirsutum, G. barbadense, G. arboretum, and G. herbacium, have been domesticated for fiber production. Today, 95% of cotton production is derived from varieties of the short-staple fiber of G. hirsutum. Most of the remainder is from G. barbadense varieties that yield long-staple fiber and are grown in more arid climates, such as Egypt, the south western United States, and Australia. Old World G. arboretum and G. herbacium varieties are at best small-scale productions that are confined to local or regional areas of Africa, India, and South East Asia. China is the current largest producer of cotton with an estimated 2009 production of 8.0 million metric tons (MMT), followed by India (4.9 MMT), the United States (2.8 MMT), Pakistan (2.0 MMT), and Brazil (1.2 MMT) (ICAC 2009b). Biotechnology-derived cotton varieties are rapidly becoming the standard throughout the world. Engineered traits include enhanced insect deterrence and herbicide tolerance, which have significantly reduced the application of insecticides and have increased crop yields. In 2008, genetically modified cotton varieties accounted for 67% of Chinese production, 76% of Indian production, and 86% of US production (Haire 2009). As the second product of the cotton plant, the supply of cottonseed depends directly on the need for and value of cotton fiber. Around 1.5–1.6 kg of cottonseed result from each kilogram of fiber produced, and the percentage of the crop value associated with the seed ranges between 15% and 20%. Seed is separated from the fiber by ginning. Whole cottonseed is either used as animal feed or crushed for oil production. The seed is of particular value to the dairy industry, where it has been found to increase the butterfat content of milk (Smith et al. 1981), which has led to competition for the seed between dairy farmers and oil processors. Almost all cottonseed oil is used in food products. The oil is preferred as a frying oil for its tendency to impart a toasted or nutty aroma to fried products. The oil is also widely used as a component for formulating shortenings and margarines, because as it solidifies it forms very fine crystals that impart a smooth texture and added plasticity to solid-fats products. Nevertheless, cottonseed oil competes with several other commodity oils for specific markets, and availability, pricing, and consumer interests all influence how the oil is used. Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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HISTORY

Historical evidence of cotton cultivation dates back to around the year 5000 bc in the Tehaucan Valley of Mexico, and evidence of cotton weaving dates back to around the year 3000 bc in the Indus River Valley of current-day Pakistan (ICAC 2009a). Cotton has been grown and used as a fiber since these times. Historical notes also point to the early small-scale extraction and use of cottonseed oil in both India and China, and cottonseed oil was extracted in Europe from imported Egyptian seed in the seventeenth and eighteenth centuries (Cooper 1948). It was Eli Whitney’s invention of the cotton gin in 1793, however, that enabled the industrialization of cotton production, which rapidly made the United States the world’s largest producer (a position it maintained until around 2000). With increased production, seed became available on a scale much greater than was needed for replanting. Initially, the excess seed was either disposed of or used as fertilizer. The birth of the cottonseed-crushing industry was driven principally by a need to find uses for this seed rather than by demand for the oil. Because of its availability at the time, cottonseed oil maintains a special place in the history of oilseed extraction and processing. Advances in crushing methods, processing equipment, refining techniques, fractionation processes, and chemical modifications all occurred because of the need to improve the oil’s properties or to develop new uses. Often these advances were first based on observations by European scientists or were applied on a small scale in Europe to other oilseeds and were then adapted by engineers in the United States to the industrial-scale processing of cottonseed. Several attempts were made at the commercial crushing of cottonseed, beginning around 1800 (Wrenn 1995). These early efforts generally failed after short periods, often due to poor capitalization, processing inefficiencies, refining problems, or simply limited markets for the products. It was not until around 1855 that cottonseed crushing became firmly established as an agricultural enterprise. Because short-staple G. hirsutum seed, the type of cotton grown in the south eastern United States, contained linters that absorbed considerable quantities of oil, separating the linters and hulls from the kernels became important initial steps in processing. Improved dehullers began to appear in the 1820s and 1830s, and bar-type dehullers, similar in principle to the dehullers used today, began to appear in the late 1850s. In the late 1860s seeds were ginned two or three times to remove as much lint as possible, in essence beginning the recovery of linters. Oil extraction was mostly by batch pressing of cooked cottonseed cakes with hydraulic box-type presses, which had been developed toward the end of the eighteenth century in England. Initially, cottonseed oil was used for lamp fuel as a replacement for scarce and expensive whale oil or for the lubrication of mechanical parts. Unsurprisingly, uses for the defatted meal were also needed, and cottonseed meal started to be marketed as a cattle feed, although not without considerable effort. With the discovery of petroleum around 1860, use of cottonseed oil as an illuminant rapidly declined. However, use shifted toward the production of soaps and as an adulterant for more expensive olive oil and lard. In 1878, Procter & Gamble Co. introduced an allpurpose bar soap called Ivory. Lever Brothers and the American Oil Co. quickly followed with Lifebouy soap and Gold Dust Twins washing powder, respectively. All of these household products were initially formulated with large amounts of cottonseed oil. Considerable supplies of cottonseed and cottonseed oil products were also exported to Europe during this time, where local production of animal fats and seed oils were insufficient to meet the needs of a rapidly increasing urban population. In Europe, cottonseed oil was often used as an

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inexpensive substitute for olive oil. It was also used as an adulterant to cheapen olive oil, a good part of which was exported back to the United States. By 1880, cottonseed crushing was firmly established as an industry along the Mississippi River Valley. With rapidly expanding cotton production and the development of rail infrastructure, which allowed the oil to be transported, cottonseed-crushing mills sprang up throughout the cotton belt. Initially, the cost of shipping whole seed plus problems with storing the seed for long periods led to the building of many small crushing mills near areas of cotton production. Because oil was cheaper to transport and oil refining was more complex than crushing, cottonseed oil-refining facilities tended to be located along central shipping points in the United States and Europe. Unsurprisingly, improvements in oilseed extraction and crude oil refining began around the same time as the expansion of cottonseed crushing. Continuous screw presses began to replace the batch hydraulic presses around the turn of the twentieth century. Solvent extraction of oil, first proposed in Europe in 1843, was known to be in limited use for various oilseeds during the latter half of the nineteenth century. Its first known use in the United States for cottonseed oil was in 1883 (Wrenn 1995). Nevertheless, it was not until the 1930s that the technological challenges associated with continuous solvent-extraction processes were largely overcome. The added capital costs of solvent equipment slowed the conversion of cottonseed mills from screw presses until higher labor costs forced this advance on the industry in the 1940s. Before 1900, oil refining was an art; methods were kept secret and were largely a matter of individual judgment. Little improvement was made until trained chemists began to focus on the problem, which was necessitated by the growing scale of operations. It was around this time that cottonseed crushers and oil chemists began to understand that a correlation existed between the level of free acid in the oil, the amount of alkali needed for refining, and the amount of oil lost during refining. As a consequence, the measurement of crude oil fatty acid levels became a standard quality assessment and led to price reductions for oils with excessive levels, a particular problem with cottonseed (discussed below). The process of alkali refining was, in effect, put on a scientific basis, resulting in much improved oil quality. With many small mills competing for seed to crush and selling products into limited markets, organization within the industry was enviable. Driven by the need to expand markets as well as establish trading rules, a number of cottonseed-crushing associations were formed. Among these, the Texas Cottonseed Crushing Association formed in 1894 and the Interstate Cottonseed Crushing Association (ICCA) formed in 1897 (Wrenn 1995). Because of the need to develop and standardize methods for determining oil quality, chemists were routinely invited to be present at the ICCA meetings and a chemists’ committee was established by the association at its 1909 convention. Nine of the chemists attending that 1909 meeting went further and proposed the formation of a separate organization, the Society of Cotton Products Analysts (SCPA) (Willhite 2008a). Initially, the society was closely associated with the ICCA, having its meetings in parallel and publishing a chemists’ column in the ICCA publication Cotton Oil Press. Despite a couple of difficult years, the organization quickly grew into its own entity. The association held its first meeting independently of the ICCA in Chicago in 1913. By 1919, the group had grown to around 200 members, and it included members with interests in fats and oils from sources other than cottonseed. To better encompass the broadening interests of the members, the organization changed its name to the American Oil Chemists’ Society (AOCS) in 1920 (Willhite 2008b). Early efforts of the society included the establishment

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of official methods of chemical analysis and the development of a laboratory chemists’ proficiency program. The AOCS broke another tie to the ICCA in 1924 by publishing the Journal of Oil and Fat Industries, which became the Oil and Fat Industries in 1927, Oil & Soap in 1932, and the Journal of the American Oil Chemists’ Society in 1947. The ICCA, together with other state associations, eventually evolved into the National Cottonseed Products Association (NCPA), which still maintains trading rules for the cottonseed and cottonseed products industries. Consumer food oil preferences for bland color, taste, and texture drove additional improvements in cottonseed oil finishing. From around 1880, cottonseed oil was being used to manufacture adulterated lard products, called ‘compound lard’ or simply ‘compound’, which was needed by the baking industry. Manufacturers found that adding relatively inexpensive cottonseed oil to lard made an acceptable baking fat and reduced its cost. Initially, the public knew little about the adulteration, although this changed with product labeling requirements that resulted because of lawsuits and disputes over future prices for lard. The first ‘advertised’ food product containing a substantial amount of cottonseed oil (80–85%) was called Cottolene, a yellow-colored shortening that was produced and marketed by the N. K. Fairbank Co. in 1886. Swift and Armour launched the related products Cotosuet and Vegetal, respectively, in 1893. Because consumers were used to lard being a white color, compound lards also needed to be light colored, which drove research into the improved bleaching of cottonseed oil. Early bleaching consisted of simply exposing cottonseed oil to sunlight for extended periods of time. Oil deterioration and the costs associated with the long processing times were hindrances. Again following French efforts, bleaching evolved into the exposure of the oil to fuller’s earth. Bleaching as well as cooling techniques (winterization) that allowed for fractionation of the oil enabled more cottonseed oil to be formulated in compound lards. David Wesson, a pioneering scientist of oil-processing technology and the second president of the SCPA, worked on many cottonseed-based efforts, including Cottolene, and perfected cottonseed oil deodorization around the turn of the twentieth century. By exposing the oil to superheated steam under a vacuum, odors and flavor components could be stripped from the oil at lower temperatures, which reduced oxidation. This resulted in the development of Wesson Oil as a household cooking and frying oil by the Southern Cotton Oil Co. Wesson also worked on hydrogenation processes that enabled the eventual production of shortenings without any animal-derived fats. Hydrogenation led to the development of Crisco, or ‘crystallized cottonseed oil’, by the Proctor & Gamble Co. in 1911. By the start of the Second World War, more than 90% of the cottonseed oil manufactured within the US went into food products. In a little under a century, cottonseed oil had progressed from a product with little use or value, to an illuminant and industrial lubricant, to a low-cost soap ingredient that evolved into a premium component for the manufacture of cleaning aids, to an important food product. The limited availability of cottonseed coupled with a rapidly growing demand for oil products ultimately forced food companies to look to other oilseeds to support continued expansion. By the early 1950s, soybean oil had eclipsed cottonseed oil for use as salad dressing oil and for incorporation into shortening and margarines, a trend that continues to widen to this day. More recently, the development of mid- and high-oleic acid sunflower oils has also reduced the use of cottonseed oil for frying snack foods. Despite its less prominent role in today’s oil and fat industries, the properties and functionality of cottonseed oil ensure its continued use in processed food applications.

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Figure 7.1 Cottonseed from a G. hirsutum variety (with linters) (A), from a G. barbadense variety (mostly lacking linters) (B), from G. hirsutum seed after acid delinting (C), and glanded cottonseed kernels (D).

7.3

SEED COMPOSITION

Because of species and varietal differences, considerable variation exists in cottonseed morphology, in seed size, and in composition. After ginning to remove the lint, seeds of G. hirsutum and G. barbadense differ in that G. hirsutum contain linters or short fibers that remain with the seed. Hence, seeds from G. hirsutum are often referred to as ‘white fuzzy seed’ and seeds from G. barbadense as ‘black seed’ (Figure 7.1). Linters make up about 12% of the white seed mass (Table 7.1) and are typically separated and recovered as one of the first steps in preparing cottonseed for oil extraction. Linters can also be hydrolyzed with acid, which is the usual practice for preparing seed for planting (Gregory et al. 1999). Being among the purest natural forms of cellulose, linters are a valuable co-product of oil extraction and have many uses. Cottonseed hulls make up around 30–32% of the dry weight of G. hirsutum seed (Table 7.1). Hulls contain mostly fibrous materials, cellulose and hemicelluloses. With little

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Table 7.1 Proximate composition and typical product yields from fuzzy white cottonseed. Seed component

Mass fraction, %

Seed analysis* Linters Hulls Kernels

12.7% 31.8% 55.5%

Product yields** Linters Hulls Oil Meal Misc. (debris/lost mass)

9% 25% 16% 46% 4%

Protein content, % 3.7% 3.8% 38.6%

5% 41–44%

Oil content, % 0.9% 0.8% 34.8%

1.9% 2.2%

Notes: * Moisture-free basis, data from Tharp (1948). ** Data from National Cottonseed Products Association website, www.cottonseed.com.

protein or oil, hulls are the least valuable of the seed components. Nevertheless, they are mostly separated during oil recovery and are largely used as a roughage component in animal feeds. Kernels make up about 55% of the whole seed and are the principal source of oil and protein (Table 7.1). Typically, moisture-free kernels will contain 26–43% crude oil and 26–41% protein (Stansbury et al. 1956). From a metric ton of cottonseed, oil extraction will yield roughly 160–180 kg of crude oil and 460–480 kg of a 41% protein cottonseed meal.

7.4

OIL COMPOSITION

Like all vegetable oils, cottonseed oil is composed principally of triacylglycerols; that is, esters of glycerol containing three fatty acids. Triacylglycerols are stored within seed tissues in oil-storage bodies. In preparing seed for solvent extraction, the oil bodies are ruptured, and the oil is exposed to other seed components. The oil is then dissolved by the solvent along with some of these other seed materials. In addition to the triacylglycerols, freshly extracted (crude) cottonseed oil contains free fatty acids, phospholipids, diacylglycerols, monoacylglycerols, gossypol (and related pigments), carbohydrates, sterols, tocopherols, carotenoids, and small amounts of proteinaceous materials. Trace levels of metals and pesticides can also be detected within the oil. Compared with other oilseeds, the concentration of some of these components in crude cottonseed oil can be relatively high. Even for good-quality seed, it is not unusual for more than 2% of the mass of the crude oil to be composed of these non-triacylglycerols. For very poor-quality seed, these components can make up over half of the crude oil mass, which can make purification of the oil challenging. Many of the undesirable components are removed during refining and finishing processes. In chemical refining, sodium hydroxide is added, which reacts with free fatty acids to form molecules of soap. These agglomerate and separate from the non-polar triacylglycerols as soapstock. Much of the more polar components of the crude oil, including most of the

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Table 7.2

Reported distribution of fatty acids in cottonseed oil.

Component 12:0 14:0 16:0 16:1(n-7) 17:0 17:1 18:0 18:1(n-9) 18:1(n-7) 18:2 18:3 20:0 20:1(n-9) 22:0 24:0

205

Codex*

NCPA**

nd–0.2 0.6–1.0 21.4–26.4 nd–1.2 nd–0.1 nd–0.1 2.1–3.3 14.7–21.7 – 46.7–58.2 nd–0.4 0.2–0.5 nd–0.1 nd–0.6 nd–0.1

– 0.8 22.2–24.4 0.4 – – 2.0–2.2 16.7–17.2 – 55.0–57.6 0.3 – – – –

Radcliffe et al. 2004§

NCVT 2006–2007†

0.04 1.02 25.4 0.63 – – 2.33 16.4 0.86 52.9 0.17 0.26 0.06 – –

nd–tr 0.54–1.4 19.6–27.6 0.43–0.79 trace trace 2.0–3.2 12.8–22.2 0.69–1.1 44.0–59.3 0.15–0.25 0.20–0.45 trace 0.08–0.21 0.08–0.20

Notes: * Codex alimentarius trading standard for cottonseed oil (FAO/WHO Food Standards 1999). ** National Cottonseed Products Association website (www.cottonseed.com). Range represents averages of cottonseed frying and salad oils. § Radcliffe et al. (2004) study on the effect of cottonseed oil on the fatty acid profiles of rat serum, adipose, and liver tissues. † Survey of cottonseed fatty acid composition from 35 genotypes included within the 2006 and 2007 US National Cotton Variety Trials. Range represents cotton genotypes grown in up to six separate locations. Report submitted by author to Journal of Cotton Science.

phospholipids, mono- and di-acylglycerols, carbohydrates, gossypol, metals ions, and so on, concentrate in the soapstock. Some non-polar components also become entrained and separate with this material. After the refining step, oil bleaching further helps to remove pigments and oil deodorization helps to remove the more volatile impurities. Refined, bleached, and deodorized (RBD) cottonseed oil from quality seed typically contains 98–99% triacylglycerols with 0.2–0.4% diacylglycerols, 0.0–0.4% sterols, 0.05% fatty acids, 0.05% tocopherols, and part-per-million levels of other components. Oil from lower-quality seed can have a lower percentage of triacylglycerols (95–96%) and correspondingly a higher percentage of diacylglycerols (2–3%) (D’Alonzo et al. 1982).

7.4.1

Triacylglycerol fatty acids

Cottonseed oil is classified as an ‘oleic-linoleic’-type vegetable oil, in that these acids make up most of the fatty acid component of the oil. Roughly half of the fatty acids are linoleic acid (18:2) and 16–20% of the acids are oleic acid (18:1n-9). Together with palmitic acid (16:0), these three fatty acids account for around 91–93% of the fatty acids in cottonseed oil (Table 7.2). Stearic acid (18:0) is present at between 2 and 3%. Several minor fatty acids are also present in the oil (0.1–1.0% each); these include myristic (14:0), palmitoleic (16:1n-7), malvalic (cpe18:1), cis-vaccenic (18:1n-7), sterculic (cpe19:1), α-linolenic (18:3), arachidic (20:0), behenic (22:0), and lignoceric (24:0) acids (cpe = cyclopropene, see Figure 7.2).

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CO2H

CO2H

CO2H Figure 7.2 Sterculic (top), dihydrosterculic (middle), and malvalic (bottom) acids.

Malvalic and sterculic acids are unusual in that they have cyclopropene rings near the middle of their structures (Figure 7.2). These acids have been found in the seed oils of many species of the Malvaceae plant family (Badami and Patil 1981). Their combined concentration in commercial cottonseed varieties is usually between 0.6% and 1.0% (Lawhon et al. 1977), although values as high as 2% have been noted (Phelps et al. 1965; Badami and Patil 1981). They are not evenly distributed within the kernel but are chiefly located around the embryonic radicle (Fisher and Cherry 1983). Because of their strained unsaturated ring structure, these oil components are not very stable outside the seed and they are partially destroyed by oil deodorization (Eaves et al. 1968). In finished oils, the level of these acids is usually <0.4% (Phelps et al. 1965). Dihydrosterculic acid, possessing a cyclopropane ring (Figure 7.2), has also been reported as a component of cottonseed oil’s fatty acid profile at a level of about 0.2% (Fisher and Cherry 1983). This acid is believed to be a precursor of sterculic acid and is usually found when this acid is present. Trace levels of saturated odd-chain fatty acids, including pentadecanoic (15:0), heptadecanoic (17:0), and nonadecanoic (19:0) acids as well as hexadecadienoic (16:2), heptadecenoic (17:1), heptadecadienioc (17:2), and gadoleic (20:1n-9) acids have also been noted in the oil (Fisher and Cherry 1983; Radcliffe et al. 2004). Fisher and Cherry (1983) have also noted significant levels of the monoepoxides of oleic and linoleic acids in cottonseed oil (∼1% total). These acids have not been noted by other authors, and my own attempts at finding these components by gas chromatographic separation of fatty acid methyl esters have failed to locate any candidate peaks. Although it cannot be entirely ruled out that these components may co-elute with other, more prevalent fatty acids or are present only in very small amounts, it seems likely that these identifications were artifacts, possibly due to oxidation or prolonged storage of their samples. In addition to the types of fatty acids present, oil properties are also influenced by how the acids are distributed along the glycerol backbone. In cottonseed oil, the saturated fatty acids are primarily found on the ends of the glycerol backbone – that is, at the sn-1 and sn-3 glycerol positions – and the sn-2 position usually carries an unsaturated fatty acid. Using thin-layer chromatography to separate cottonseed triacylglycerols by the number of unsaturated bonds, Jurriens and Kroesen (1965) estimated the distribution of the principal fatty acids along the glycerol backbone. Summarizing these data by grouping the fatty acids into either saturated (S) and unsaturated (U) acids gives a distribution of 0.5% SSS, 1.4% SSU, 2% USU, 16.9% SUS, 45% SUU, and 32% UUU. Bland et al. (1991) identified several of the individual triacylglycerols based on their gas and liquid chromatographic retention times

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Table 7.3 Identification of cottonseed oil triacylglycerols by gas and liquid chromatography. Component Palmitic-linoleic-linoleic Linoleic-linoleic-linoleic Palmitic-oleic-linoleic Oleic-linoleic-linoleic Palmitic-palmitic-linoleic Oleic-oleic-linoleic Palmitic-oleic-oleic Palmitic-palmitic-oleic Oleic-oleic-oleic Stearic-linoleic-linoleic Stearic-palmitic-linoleic Stearic-oleic-linoleic

by GC

by HPLC

25.7 16.1 14.0 12.9 8.7 4.4 3.3 2.5 2.4 2.4 2.1 1.5

27.5 19.0 14.0 12.5 7.1 3.1 3.1 2.2 1.6 1.4 1.5 1.3

Source: Bland et al. (1991).

(Table 7.3). From their peak assignments, the distribution of saturated and unsaturated fatty acids along the glycerol molecule was found to be 13.3% SSU+SUS, 46.9% SUU+USU, and 35.8% UUU, which is in general agreement with the thin-layer results. Field conditions also influence cottonseed fatty acid profiles. Stansbury et al. (1953) observed a decrease in iodine value with increased field temperatures and decreased rainfall. A recent survey of cotton varieties grown in different environments as part of the National Cotton Variety Trials (NCVT) showed that linoleic acid levels decreased and saturated fatty acid levels increased when cotton was grown in hot and dry environments (report submitted by this author to the Journal of Cotton Science), which is in accord with the iodine value trend observed by Stansbury et al. (1953). In addition, increased soil salinity has been reported to decrease the level of linoleic acid and increase the levels of stearic and oleic levels in cottonseed oil (Ahmad et al. 2007). Most reported surveys on fatty acid profiles have been limited efforts that cover only a small number of commercial varieties (Lawhon et al. 1977; Nergiz et al. 1997; Lukonge et al. 2007). These surveys indicate that the variation in fatty acid profiles within commercial cotton varieties is roughly comparable to the United Nations’ Food and Agriculture Organization and World Health Organization’s Codex Alimentarius trading standards for cottonseed oil (Table 7.2; FAO/WHO Food Standards 1999). Genetic modification of cotton for improved insect control and herbicide tolerance appears to have had minimal to no effect on cottonseed fatty acid profiles. One detailed comparison between modified and non-modified parental varieties has been reported (Hamilton et al. 2004) and the overall effect on fatty acid composition was minimal. In addition, the above-mentioned NCVT survey included several genetically modified and nongenetically modified varieties. A comparison of the fatty acid profiles of these varieties separated into genetically modified and non-genetically modified groups indicated no significant differences for any of the major fatty acids. Segregation of genetically modified cottonseed oil is not, at present, practiced. Cottonseeds with altered fatty acid profiles, however, have been reported. Most dramatically, Yunusova et al. (1991) reported that their L-78 line, a linter-less variety, had

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43% palmitic acid and 26% linoleic acid, which is essentially opposite to the normal values for these acids. In addition, the seeds of closely related Gossypium sp. suggest that a wider range of fatty acids is possible. For example, seeds of G. arboreum and G. armourianum have been reported with oleic acids levels of 32% and 36%, respectively (Carter et al. 1966), which is essentially double the concentration of this acid in commercial cotton varieties. In addition, genetic techniques have been used specifically to down-regulate the Δ9 and Δ12 desaturase enzymes responsible for the conversion of stearic acid into oleic acid and the conversion of oleic acid into linoleic acid, respectively (Chapman et al. 2001; Liu et al. 2002; Sunilkumar et al. 2005). These efforts have been successful in increasing the proportions of stearic or oleic acids from their normal levels at the expense of linoleic acid, a trait that should improve the oxidative stability of the oil. Seeds with stearic acid levels of around 40% and seeds with oleic acid levels around 78% have been demonstrated (Liu et al. 2002). Modifying the fatty acid composition of cottonseed oil is a current topic of interest within the cotton research community. The recent development of sunflower oils with elevated levels of oleic acid (Gupta 1998) significantly affected cottonseed oil’s market as a snack food frying oil. This served as a wake-up call for the cotton industry to understand the advances other oilseeds have made in tailoring the composition of their oils to specific enduses and the competitive nature of the vegetable oil and food industries. Because other oilseeds have bred modified traits from mutants, either found naturally or developed through chemical mutagenesis, cottonseed oil must follow a parallel path to remain competitive. Consequently, the cotton industry has started to think about what traits might be useful for improving the value of the oil. Potential targets include modifying the level of saturated fatty acids (a case can be made for modification in either direction), changing the ratio of oleic and linoleic acids from 1:3 to 3:1, and reducing the levels of the cyclopropenoid acids. Because cotton breeding for fiber traits is well established, large seed collections of wild and obsolete varieties exist, and efforts are underway to characterize this material for fatty acid composition. Of course, cotton fiber properties cannot be compromised, which may complicate breeding for seed traits. Further developments should be expected on this topic over the next several years.

7.4.2

Other oil components

7.4.2.1

Free fatty acids

Even under the best of conditions, free fatty acid levels in cottonseed tend to rise over time. If the seeds are exposed to wet conditions during harvesting or are improperly stored, degradation can occur rapidly. Oil extracted from good-quality seed would normally have a free fatty acid level of around 1%; however, crude oil with 5% free fatty acid is not unusual, and oil from severely degraded seed can have free fatty acid levels of 10–25%. The deterioration appears to be caused by lipases that are activated either as part of normal germination processes or because of microbial contamination. Both factors probably contribute to the problem. Linoleic, oleic, and palmitic acids make up the bulk of the observed free fatty acids in crude cottonseed oil (Wan et al. 2007) and soapstock (Stansbury et al. 1957; Dowd 1996). Their distribution is roughly the same as for the esterified fatty acids, although there can be a slight skewing of the distributions toward the saturated fatty acids. This occurs because of the presence of the saturated fatty acids exclusively on the sn-1 and sn-3 positions of the glycerol backbone, which are more prone to be acted on by lipases.

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7.4.2.2

209

Mono- and di-acylglycerols

The lipase activity that elevates free fatty acids also increases the level of mono- and diacylglycerols in crude cottonseed oils. As these acylglycerols are more polar than triacylglycerols, they tend to accumulate in the soap phase during chemical refining. 7.4.2.3

Phospholipids

Research on the phospholipids of cottonseed oils has been summarized by Cherry (1985). As with other oilseeds, some phospholipids are co-extracted with the oil. Crude cottonseed oil can be water washed to recover a gum fraction that contains high levels of phospholipids. Alternatively, soapstock can be extracted with various solvents to recover fractions rich in phospholipids. These fractions are of little commercial interest, largely due to the presence of gossypol (discussed below). In fact, cottonseed gums contain so much gossypol (4–5%) that Pons et al. (1959) developed a process to recover the compound from this material. For many years, this method was a major source of the compound. Renewed interest in cottonseed phospholipids occurred with the discovery of the glandless trait in cotton (McMichael 1959), which produces only traces of gossypol in the aerial parts of the plant. Working with seed from glandless varieties, Cherry (1983) reported that phosphatidylcholines, phosphatidylinositols, and phosphatidylethanolamines were the main phospholipid classes in water-washed gums, accounting for around 50% of the extracted phosphorus. Smaller amounts of phosphatidyserines, phosphophatidic acids, phosphatidylglycerols, and lyso-compounds were also identified. Linoleic, palmitic, and oleic acids were identified as the main fatty acid component in the glycerol esters of cottonseed gums. Their distribution closely resembled the distribution of these acids in the oil (Cherry 1983). Unfortunately, cottonseed phospholipids still have not been exploited commercially. This is partly because glandless varieties have not been commercialized, and partly because miscella refining of the oil (discussed below) does not allow for the recovery of a gum fraction. 7.4.2.4

Sterols

Phytosterols are non-saponifiable, high-melting alcohols that have polycyclic ring structures and are found in all vegetable oils. These oil components are colorless, heat stable, and relatively non-reactive. Verleyen and co-workers (2002) report total sterol levels of around 690 mg per 100 g in degummed crude oil and 460 mg per 100 g in refined oil. About 80% of the sterols in cottonseed oil are in the free (non-esterified) form (Verleyen et al. 2002). β-Sitosterol is the most abundant sterol in cottonseed. Lesser amounts of campesterol, stigmasterol, and Δ5-avenasterol are reported, and trace levels of Δ-7-avenasterol, cholesterol, brassicasterol, and Δ7-stigmastenol are also detected (Itoh et al. 1973). Given the non-polar character of sterols, refining and bleaching generally do not reduce sterol levels. However, chemical refining entrains a fraction of non-polar compounds, and β-sitosterol, campesterol, and sigmasterol have all been identified as components of cottonseed soapstock (Dowd 1996). Soapstock and deodorization distillate can serve as good starting materials for the isolation of vegetable sterols (O’Brien et al. 2005).

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7.4.2.5

Tocopherols

As for most vegetable oils, cottonseed oil contains various tocopherols. These compounds are beneficial as they act as antioxidants, and levels of greater than 500 ppm are useful for maintaining oil stability. The total level of tocopherols in crude cottonseed oil is of the order of 900–1000 ppm (List and Friedrich 1989; O’Brien et al. 2005) and in finished oil a range of 630 to 970 ppm has been reported (Slover et al. 1969; Müller-Mulot 1976). α-Tocopherol, which contributes vitamin E activity, accounts for about 41% of the tocopherol distribution, and δ-tocopherol (a powerful antioxidant) accounts for 58% of the distribution (Slover et al. 1969; Müller-Mulot 1976). Trace levels of β- and γ-tocopherols are also present. Chemical refining and deodorizing processes reduce tocopherol levels, and up to a third of these beneficial components can be lost during these steps. 7.4.2.6

Carbohydrates and polyalcohols

Cottonseed is known to contain significant levels of sucrose, raffinose, and stachyose. These compounds make up about 11% of the weight of defatted cottonseed (Kuo et al. 1988). Raffinose is present in the highest concentration, accounting for about 60–65% of these sugars. There is little direct information regarding the levels of these compounds in miscella or crude oil; however, all three sugars as well as glycerol and myo-inositol have been measured in cottonseed soapstock (Dowd 1996). Combined, they make up about 3.5% of the soapstock dry matter. Assuming that soapstock represents about 3% of the crude oil mass, this suggests that these polar compounds are present in a combined level of about 0.1% of the crude oil. Refining removes essentially all of these compounds. 7.4.2.7

Carotenoids

Cottonseed oil carotenoids have not been discussed in the literature. However, they have been reported in other vegetable oils (e.g., corn oil). Because they have been identified in extracts of cottonseed made with solvents capable of extracting oil (Thompson et al. 1968), one must suspect they are present in crude cottonseed oil, albeit in very small amounts. The main carotenoid found in cottonseed is lutein, with smaller amounts of isolutein, neoxanthin, violaxanthin, α- and β-carotene, and other xanthophylls (Thompson et al. 1968). The total carotenoid concentration in seed is reported to be about 0.6 mg/kg. 7.4.2.8

Miscellaneous

Squalene has been reported in vegetable oils, including cottonseed oil (Bailey 1948). In cottonseed oil its level is very low, around 0.01%. Protein fragments (peptides) are also mentioned in the early literature (Bailey 1948). They are assumed to be present in soapstock, based on measured excess nitrogen levels not attributable to phospholipids (Dowd 1996). However, no proteinaceous components have been isolated or characterized from these materials to date. Small amounts of metals are also common in crude vegetable oils. In refined oil these can promote oxidation. They are easily removed during refining and finishing processes by chelation with an acid (often citric or phosphoric acid) followed by filtration.

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Cottonseed Oil O

OH 6’

HO

O

CH3

1

HO

OH

1’

HO

211

CH3

2’ 2

HO

CH3

6

H3C

CH3

CH3

Figure 7.3 Structure of gossypol. Because of restricted motion about the central bond, the molecule exists stably as enantiomers. With the hydroxyl groups of the left naphthalene ring oriented upward and the hydroxyl groups of the right naphthalene ring oriented forward (as shown), the molecule is in the S- or P-form, corresponding to the dextrorotary or (+)-form.

Trace levels of pesticides, residual solvent, and other hydrocarbons are not uncommon in crude cottonseed oil. Downstream refining and finishing steps reduce pesticide and solvent residues to within required standards.

7.4.3

Gossypol

Gossypol is a polyphenolic disesquiterpene (Figure 7.3), found in plants of the Gossypeae tribe of the Malvacea family, which includes the Gossypium genus. Gossypol is located in lysigenious glands (often referred to as pigment glands) that are dispersed throughout the plant’s aerial tissues and along the epidermal surfaces of root tissue. In aerial tissues, the compound appears to function to deter insect predation (Bottger et al. 1964). Concentrations of gossypol in glanded cottonseed kernels usually range between 0.8% and 1.5%, although levels between 3% and 4% are not unusual (Percy et al. 1996). Gossypol exists as a pair of stable atropisomers because of the restricted rotation about the compound’s binaphthalene bridge bond, which results in a chiral axis (Figure 7.3). The cotton plant produces both enantiomers. Considerable differences exist in the distribution of the individual gossypol enantiomers within different Gossypium species and varieties. The environment has a strong effect on the total amount of gossypol in seed (Stansbury et al. 1956), but the ratio of the individual enantiomers is largely invariant to field conditions (W.R. Meredith, Jr., personal communication, report in preparation). Seeds of cultivated G. hirsutum varieties tend to have an approximate 60:40 ratio of the (+)- to (−)-isomers. Cultivated G. barbadense varieties often have a small excess of the levorotatory form, with a 45:55 ratio of the (+)- to (−)-isomers being fairly typical (Cass et al. 1991; Percy et al. 1996). Primitive lines of both species have been identified with >90% of their gossypol in the (+)-optical form (Cass et al. 1991; Stipanovic et al. 2009), but no lines have been identified with the percentage of (−)-gossypol being greater than ∼68% (Stipanovic et al. 2009). Some gossypol is taken up by the miscella during solvent extraction, and its concentration in crude oil can be as high as 0.5% (Jones and King 1996). The extracted gossypol is

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concentrated almost entirely within the soap phase during chemical refining, and gossypol concentrations in soapstock can be as high as 8% on a whole-weight basis (Dowd 1996). Cottonseed meals typically have gossypol levels comparable to the levels in kernels; that is, 1% to 1.5%. Gossypol’s presence in refined and finished cottonseed oils is a matter of some debate, although it is not detectable with our best analytical HPLC methods. Hence if it is present, its concentration is below the compound’s ∼0.1 ppm detection limit (O’Brien et al. 2005). Early methods of gossypol preparation used either defatted kernels or root bark as starting materials. As mentioned above, Pons and co-workers (1959) found cottonseed gums to be a particularly good source of gossypol. Because gums are no longer readily available, soapstock has also been found to be good source material for gossypol recovery (Dowd and Pelitire 2001). Among gossypol’s unusual physical properties, it readily forms solvates with different low molecular weight compounds. To date, around 80 different molecular solvates have been reported, the structures and various packing arrangements of which have been described by Gdaniec et al. (1996). Most recovery procedures add acetic acid to concentrated gossypol extracts, which results in the precipitation of the compound as a racemate that contains an equimolar amount of acetic acid (i.e., rac-gossypol-acetic acid (1:1) ). This form of gossypol is the easiest to isolate, and it is the usual starting point for obtaining the compound for research work. Kenar (2006) has recently reviewed gossypol’s reaction chemistry. Of primary importance among its reactions, the compound readily forms Schiff’s base complexes with amines, which accounts for gossypol’s ability to bind to the protein and phospholipid components of the seed. The same reaction with 3-amino-1-propanol or R-(−)2-amino-1-propanol is often used for analytical measurement of the compound (Kim et al. 1996; Hron et al. 1999). The presence of gossypol in cottonseed and cottonseed meal is responsible for the occasional toxicity and reproductive problems associated with the overfeeding of cottonseed products in animal diets (Bernardi and Goldblatt 1980). Ruminant animals are much less sensitive to the compound than non-ruminant animals; consequently, cottonseed is regularly used as a protein source for dairy and beef cattle, goats, and sheep, but it is rarely used for feeding swine or poultry. In poultry, the compound has also been linked to a mottled greenish discoloration of egg yolks (Schaible et al. 1934). The binding of gossypol to protein in cottonseed meals (discussed below) is often assumed to make the meal less toxic to animals, although the factors that make the gossypol in cottonseed products ‘available’ to the animal are not well understood. These factors appear to extend beyond a simple characterization of the levels of bound and free gossypol present in the feed product, as feeding experimental diets containing comparable levels of free gossypol often produces variable and contradictory results. Further details on this issue can be found in Calhoun (2002). Gossypol exhibits a wide array of interesting and potentially valuable bioactivity, for which it is studied in its own right. The use of crude cottonseed oils in remote Chinese villages in the 1950s led to the discovery of the compound’s male anti-fertility effects. Largescale human trials were conducted in the 1970s that resulted in better than 99.98% infertility (National Coordinating Group on Male Antifertility Agents 1978). Although the compound was effective, two-month periods were required for sterility to develop and three-month periods were needed for fertility to return after discontinuation of the drug. Because of these long periods required to achieve effectiveness and recovery, as well as concerns regarding permanent sterility, gossypol has not become a male contraceptive agent. Other reported effects associated with gossypol include inhibition of cancer cells, inhibition of amoebic, protozoan, and microbial organisms, inhibition of viral replication, and antioxidant activity

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(Wang et al. 2009). Current interest in the compound is mainly focused on its anti-cancer activity (Dodou 2005), which has led to interest in the synthesis and testing of a range of racemic and chiral gossypol derivatives. Gossypol’s toxicity and bioactivity effects appear to be sensitive to the compound’s optical form. For example, (−)-gossypol is more active than (+)-gossypol in slowing the growth and reducing feed conversion in broilers (Bailey et al. 2000; Lordelo et al. 2005), but (+)-gossypol is more active than (−)-gossypol in reducing egg production and increasing egg yolk discoloration in laying hens (Lordelo et al. 2007). (−)-Gossypol also appears to be more effective in reducing sperm motility, tumor cell growth, and viral reproduction (Dodou 2005; Wang et al. 2009). However, both enantiomers appear to contribute equally to the plant’s natural defenses against insects (Stipanovic et al. 2006). In recent years, there has been considerable interest in modifying the amount and isomer distribution of gossypol in cottonseed. Glandless cotton varieties did not find commercial acceptance, largely because of concerns over the potential for increased problems with insect and rodent predation. Consequently, efforts are underway to try to develop cotton plants with gossypol levels maintained or elevated in the plant foliage but reduced or eliminated from the seed. Sunilkumar and coworkers (2006) have reported initial success toward this goal by exploiting RNAi gene silencing of δ-cadinene synthase with a seed-specific promoter to inhibit gossypol production only in the seed. In addition, because (−)-gossypol is generally considered to be less toxic than (+)-gossypol, Bell and co-workers (2000) have used G. hirsutum var. marie galante landraces that have most of their seed gossypol in the (+)-optical form to breed agronomic cotton plants with this trait. Plants from both of these efforts are currently undergoing field trials (Watkins 2009).

7.5

CHEMICAL AND PHYSICAL PROPERTIES OF COTTONSEED OIL

Over the years, a number of tests have been developed to characterize vegetable oils. These can be divided into tests that determine the physical, chemical, and optical properties of the oil. Some properties relate directly to the composition of the triacylglycerol fatty acids; other properties are affected by the order of the fatty acid along the glycerol backbone and the relative levels of the various triacylglycerol molecules present in the oil. Melting behavior is an important property for vegetable oils used in food applications. Because vegetable oils are composed of a mixture of different triacylglycerols, it is difficult to determine a single melting point, as would be normal for pure compounds. For vegetable oils, a variety of different techniques are used to determine melting, including capillary melting point determinations, softening point determinations, slipping methods, the Wiley melting point, and the Mettler dropping point. By these various measures, the melting point of RBD cottonseed oil is generally found to be between 10 °C and 16 °C. A better understanding of the melting behavior of a fat or oil can often be made by determining the amount of liquid and solid phases present in a sample over a range of temperatures. The solid-fat index provides this type of measure. This particular index, however, has been standardized to mean the percentage of solid fat existing at temperatures of 10 °C, 21.1 °C, 26.7 °C, 33.3 °C, and 40 °C. It is mainly used to measure melting of oil blends or modified oils formulated into solid-fat food products. RBD cottonseed oil has only a minimal amount of solids present at the lowest, 10 °C temperature. However, hydrogenated cottonseed oil, winterized cottonseed stearins, and cottonseed oil blended with animal fats all

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Table 7.4

Selected properties of cottonseed oils.

Property

Cottonseed oil products RBD oil

Specific gravity (25/25 °C) 0.914–0.918 Refractive index (25 °C) 1.468–1.472 Iodine value 98–118 Lovibond color (red) 2.0–6.0 Free fatty acid, % <0.05 Peroxide value, meq/kg <1.0 AOM stability, hr 15–19 Cloud point, °C −1.1–3.3 Melting point, °C 10–16 Titer, C° 30–37 Pour point, °C −3.9–0.0 Smoke point, °C 220–230 Flame point, °C 320–340 Fire point, °C 355–360 Cold test, hr ∼1 Flavor bland Unsaponifiable matter, % 0.5–0.7 Saponification value 189–198

Winterized Partially Fully (salad) oil hydrogenated oil hydrogenated oil

103–116 2.0–4.0 <0.05 <0.5 15–25 −3.9–0.0 – – −3.9–0.0 230

50–70 2.0–2.5 <0.05 <0.5 100–200 – 32–47 35–45 39–60

2–5 2.0–2.5 <0.05 <0.5 >350 – 60 >60 >60

12 to 20 bland

– bland

– bland

Sources: Values taken from several sources, but principally from O’Brien et al. (2005), Jones and King (1990), and the National Cottonseed Products Association website (www.cottonseed.com).

would have significant solid-fat indices. O’Brien et al. (2005) list solid-fat profiles for a number of fractionated and hydrogenated cottonseed oil products. Cottonseed oil hydrogenated to an iodine value of 75, for example, exhibits a solid-fat index of 20.5% at 10 °C, 10.5% at 21.1 °C, 7.0% at 26.7 °C, and 2.5% at 33.3 °C (O’Brien et al. 2005). Other measures of solidification or melting are also used to evaluate and compare oils. Cold point is a test used to determine if oil will remain clear on standing at 0 °C for 5.5 hr. Cottonseed oil generally fails this test, but winterized cottonseed oil passes it. Often this test is extended until the oil starts to cloud; in which case the procedure is referred to as the ‘cold test’ (Table 7.4). The cold testing of winterized cottonseed oil generally yields times between 12 and 20 h. The cloud point is the temperature at which the oil will ‘cloud’ or reduce the transmission of light. The cloud point of RBD cottonseed oil is typically between −1.1 °C and 3.3 °C, and the cloud point for winterized cottonseed salad oil is between −5.6 °C and −3.3 °C. The pour point temperature refers to the temperature at which the oil remains pourable, which for RBD cottonseed oil is between −3.7 °C and 0 °C. For hydrogenated cottonseed products, the pour point temperature can be as high as 60 °C. The titer value is a measure of the solidification of an oil’s fatty acids and is used primarily to characterize fatty acids from soap or fully hydrogenated oils. Titer values for cottonseed oil are relatively high compared to other oils due to the elevated levels of saturated fatty acids. Cottonseed oil has titer values ranging from 32 °C to 37 °C. The titer value of winterized cottonseed oil is slightly lower. For fully hydrogenated cottonseed oil, the titer value is around 60 °C. During the crystallization of fats and oil, it is recognized that different crystalline packing motifs or habits are possible. Three basic habits have been identified: α-, β2- and β-forms. The α-crystal habit is metastable and tends to slowly reorganize into the β2-form. Most

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vegetable oils crystallize into the β-form (O’Brien et al. 2005), which is characterized as having larger and coarser crystals. Cottonseed oil, rice bran oil, and most animal fats crystallize into the β2-form. This habit has very small, fine crystals that tend to impart a smoother consistency and a more fluid plasticity to solid-fat products, properties that are desirable in many food applications, such as icing, spreads, and shortenings. This trait appears to result from the higher levels of palmitic acid in cottonseed oil and the unequal distribution of the saturated fatty acids along the glycerol backbone. Partially hydrogenated cottonseed oils and cottonseed oil blends also tend to solidify into the β2-crystal form. Specific gravity (density) and viscosity are important processing properties. The specific gravity (25/25 °C) of RBD cottonseed oil is usually between 0.914 and 0.918 (Table 7.4). Hydrogenation reduces the density of cottonseed oil slightly. Oil viscosity directly affects the cost of pumping, and the lubricity provided by the oil can be an important property in the formulation of some food products. Bailey (1948) summarizes viscosity and density data for finished, winterized, and hydrogenated cottonseed oils. Higher degrees of saturation tend to increase oil viscosity; hence, cottonseed oil is slightly more viscous than most other vegetable oils. Both density and viscosity of oil tend to decrease with increased temperature. The refractive index of a vegetable oil is an easy test for the identity or purity of an oil. At 25 °C, cottonseed oil has a refractive index between 1.468 and 1.472. The refractive index is dependent on temperature and the structure of the glycerol ester fatty acids. With predetermined curves at a fixed temperature, the refractive index is sometimes used to estimate iodine values. The smoke point is the temperature at which the oil starts to smoke when heated; the flash point is the temperature at which sufficient oil volatiles are generated to support ignition; and the fire point is the temperature at which oil combustion can be sustained. RBD cottonseed oil with 0.04% free fatty acid levels has a smoke point around 220 °C, a flash point of near 322 °C, and a fire point near 360 °C (Jones and King 1990). These temperatures are all very sensitive to the level of free fatty acids in the oil as well as any significant level of residual solvent (Morgan 1942). Color and flavor are important properties for food applications. As mentioned above, crude cottonseed oil tends to be darkly colored. Refined cottonseed oil is generally a rich golden yellow color that is darker than soybean, canola, and sunflower oils, but lighter than corn oil. The refining of cottonseed oils for color can be technically challenging and dark oils are not uncommon. In the cottonseed industry, laboratory tests are often made on refined oil to determine the bleachability of the oil. Typically a bleachable Lovibond red value of <2.5 is required for the oil be graded as Prime-Bleachable Summer Yellow (PBSY), the highest grade for once-refined cottonseed oil (NCPA Trading Rules 2008). Oil used for food formulation or cooking should have, in general, a bland flavor that does not mask the flavor of the other components. Fully deodorized cottonseed oil used at low temperatures has a bland flavor. With heating, cottonseed oil tends to impart a toasted or nutty flavor to food products, and the oil is used specifically for this property by snack food manufacturers. Free fatty acid level is an important oil quality trait and, as discussed above, this is of particular concern for cottonseed oil. It is generally measured by dispersing the oil in solvent and measuring the acidity by titration against a known concentration of sodium hydroxide. In general, proper refining removes the bulk of the free fatty acids from the crude cottonseed oil, and bleaching and deodorization will eliminate most remaining acids to leave RBD oil with generally <0.05% free fatty acids.

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The iodine value is a simple and rapid method that determines the amount of double bonds (average unsaturation) present in a fixed amount of oil. For cottonseed oil, iodine values of 98–118 are typical. Winterized stearin fractions and hydrogenated products have lower iodine values and winterized salad oil has slightly higher iodine values (Table 7.4). Iodine value is widely used to monitor the progress of winterization and hydrogenation processes. When exposed to air and heat, vegetable oils tend to oxidize. This tendency is an important property for oils that are to be used for frying or other high-temperature purposes. During the initial stages of oil oxidation, oxygen reacts with the fatty acid double bonds to form hydroperoxides. The peroxide value provides a measure of these oxidation components in the oil and is generally reported as the number of milliequivalents present per kilogram of oil, which is determined by monitoring the liberation of iodine from potassium iodide. Good-quality cottonseed oil will typically have peroxide levels of <1. The anisidine value is a second measure of oxidation that quantifies the presence of aldehyde groups in the oil formed with more advanced oxidation. Reaction of p-anisidine with aldehyde moieties results in yellow-colored products that are detected at 350 nm. Values of <10 are typical of good-quality cottonseed oil. While peroxide and anisidine values are useful for determining the oxidative state of an existing oil, it is often more important to know the tendency of an oil to oxidize under a given set of conditions. The AOM stability test uses heat and aeration to accelerate oil oxidation, which is followed until the oil reaches a specified peroxide value. Usually, this peroxide value is 100 milliequivalents. RBD cottonseed oil tends have AOM stability times of 15–19 hr. Unsaponifiable matter is a measure of the amount of non-glycerol ester components in the oil (e.g., sterols, tocopherols, pigments, hydrocarbons) and is determined by measuring the mass of the sample taken up in a non-polar solvent after complete saponification of the oil and correction for residual fatty acids. For RBD cottonseed oil, unsaponifiable matter is typically between 0.5% and 0.7% of the oil mass (Table 7.4). The saponification value relates to the amount of potassium hydroxide that is needed to saponify a sample. In effect, it is useful for estimating the average molecular weight of the esterified fatty acids in a sample. For cottonseed and most oleic–linoleic-type vegetable oils, the saponification value ranges from 189 to 198 with an average value of 195 (Table 7.4).

7.6

PROCESSING

Like most vegetable oils, recovery of cottonseed oil follows a pathway that includes seed preparation, extraction, and purification steps. Purification of crude oils includes chemical refining, bleaching, and deodorization processes. Depending on the intended use of the oil, a second refining or bleaching of the oil is sometimes needed. Compared with other oilseeds, there is somewhat less flexibility in the processing of cottonseed, because of its high free fatty acid levels and the presence of gossypol.

7.6.1

Seed preparation

Proper storage of cottonseed prior to processing is important because of its tendency to form free fatty acids. Dry and cool storage conditions are best and aeration is normally required, although these conditions can be difficult to maintain in the cotton belt (Gregory et al. 1999).

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Seed is usually conveyed into the mill and is initially screened to remove any plant and field debris. Linters are removed by delintering machines that consist of a series of closely spaced saw blades, similar in design to the saw-blade gins used to remove cotton lint. Recovery of the linters often occurs in multiple cuts, which are then baled and sold as first-cut and second-cut linters. Delintered seed is cracked with bar dehullers that cut seeds into two or three pieces or occasionally with disc dehullers. Most hull pieces are then separated from the kernel or meat pieces by the action of a series of shaker tables and aspirators. Some hull material is allowed to remain with the meat, as it improves the efficiency of the extraction process and provides a means for controlling the protein level in the final meal product. Meats are then passed through sets of roller mills to produce thin flakes and are cooked in steam-heated stacked cookers. Cooking thin flakes allows for a more uniform heating process. The cookers usually consist of four to eight stacked steam-heated sections with rotating stirrers to keep the meats moving and gates to enable the meats to move between different sections of the cooker. Cooking temperatures, times, and moisture levels depend on the type of process to be conducted, but temperatures starting around 85–90°C and ending around 110–125°C with a total cook time of 30–120 minutes are typical. Moisture levels are usually controlled at around 12% during the initial stages, but are reduced toward the end of the process to allow for better pressing or expanding of the cooked meats. In addition to rupturing cell walls and oil-storage glands, cooking deactivates enzymes and microorganisms and helps to agglutinate proteins (Norris 1982). The moist heating also ruptures the pigment glands, which allows the gossypol to mix with other seed components and promotes its binding to proteins and phospholipids. The binding is considered desirable in that it reduces the amount of gossypol that is taken up by the crude oil, where it contributes to color and bleaching problems. Cooking is carefully controlled, as undercooking reduces the yield of oil and overcooking produces dark oils that are difficult to bleach. Overcooking also reduces the feed value of the protein in the meal.

7.6.2

Oil extraction

After cooking, a number of variations in cottonseed processing are possible. Historically, cooked flakes were hydraulically pressed. Box-type stacked-plate hydraulic presses were typically used. The seed would be wrapped in cloth and pressed in batches to recover the oil. The method was labor intensive and would leave a cottonseed ‘cake’ with 6–10% residual oil (Norris 1982). Screw pressing (or expeller pressing) could be conducted continuously, which reduced labor costs. As the meats worked their way through the screw, very high pressures and heat are applied, which forces oil out of the meat. Groups of narrowly placed bars are positioned along the outside of the screw barrow and are aligned to form narrow slits that allow the oil to escape and to be collected. The cooking process and the final moisture are adjusted to accommodate the extra heat applied in the expeller. Expeller processing typically leaves the cake with residual oil levels of 3–4% (Norris 1982). This form of screw pressing gradually gave way to solvent-based extraction methods that use commercial hexane to dissolve the oil and carry it away from the meat material. The use of solvent complicates the process, but reduces oil levels in the meal to <1.0%. A number of variations of solvent processes have been used in the cottonseed industry. Direct-solvent processes extract oil from cooked cottonseed flakes. Prepress-solvent processes recover oil in two steps, first pressing or expelling the seed cake to recover the easyto-extract oil, then solvent extracting the partially defatted meal to recover the more difficult

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oil. This process gradually evolved into the expander-solvent process. After flaking and cooking, the meat is passed through an expander (essentially an extruder) that mixes the meats and applies heat and pressure to the matrix before it is forced through a die plate. The change in pressure that results when the material exits the die plate causes the cottonseed cake to expand rapidly and form large, porous ‘collets’. Some oil is forced from the seed matrix as it exits the expander, but is rapidly readsorbed within the interstitial spaces of the collets. The addition of some hulls with the cooked meats improves the durability and extractability of the collets, allowing for a reduced solvent-to-meat ratio and a smaller solvent hold-up volume in the extractor. This expander-solvent process became commonplace in the 1970s and is the standard for much of the cottonseed-crushing industry today. Stricter demands for improved oil color led to the necessity of starting the refining of cottonseed oil immediately after extraction. Historically, crude oil was chemically refined after removal of the solvent, which exposed the oil (and its pigmented impurities) to relatively high temperatures that promoted color formation in the oil. This sometimes resulted in ‘color-set’ oils that were difficult to bleach. To get around this problem, cottonseed oil is usually miscella refined; that is, the initial chemical refining begins before the complete recovery of the solvent (Hendrix 1984). In miscella refining, the miscella is initially concentrated from the 16–17% oil level exiting the extractor to around 45–65%. Then a concentrated solution of sodium hydroxide is added and rapidly mixed. The amount of sodium hydroxide added is slightly greater than the stoichiometric amount needed to react with the free fatty acids, with the small excess helping to remove color from the oil but limiting any saponification of the triacylglycerols. After a short contact period, the soap is separated from the miscella with a continuous centrifuge. Advantages of refining in this manner include reduced viscosity, which allows for more rapid mixing of the sodium hydroxide solution; lower pumping and mixing costs; a sharper centrifugal separation of the soapstock, which reduces the entrainment of the oil; elimination of water washing to remove traces of soap from the crude oil; and improved oil color. Disadvantages of the technique include the cost and maintenance of more solvent equipment and the necessity of evaporating the solvent in stages. After separation of the soap, the remaining solvent is stripped from the refined oil. Soapstock exiting the centrifuge is often sprayed on to the defatted meat, where it reduces dustiness and adds energy content to the meal product. The meal is then desolventized with steam heat and vacuum to recover as much of the hexane as possible. At this point, the cottonseed oil is often sold as a once-refined commodity product. PBSY is the most commonly traded grade of oil, which is defined as having a bleachable color of ≤2.5 on the Lovibond color scale with <0.25% free fatty acids and ≤0.1% total moisture and volatiles (NCPA Trading Rules 2008).

7.6.3

Oil finishing

After refining, bleaching and deodorization are necessary to produce commercial RBD oil. During bleaching, the oil is mixed with a bleaching clay or earth under vacuum and elevated temperatures to remove color bodies, trace metals, and any residual soap. After a short contact period, the adsorbent is removed by filtration. Deodorization, basically a vacuum distillation process, removes volatile compounds associated with off flavors and odors. Steam is introduced to help strip away the more volatile compounds, which include residual fatty acids, fatty acid oxidation products, traces of solvent, and some of the tocopherols and sterols. Traces of pesticides not removed by refining or bleaching are also removed.

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As mentioned above, the elevated temperatures of deodorization and the presence of small amounts of free acids can destroy much of the cyclopropenoid fatty acids present in the oil (Eaves et al. 1968).

7.6.4

Additional processing

In addition to the basic refining techniques used to remove impurities, cottonseed oil frequently undergoes further processing for specific end-uses. Winterization is used to produce cottonseed oil that will remain liquid and clear at refrigeration temperatures. During winterization, the oil is maintained at a fixed temperature of around 6 °C to allow partial crystallization to occur. The oil is cooled slowly without agitation to form larger crystals. The solid crystals are then filtered to produce winterized cottonseed salad oil and winterized cottonseed stearin. Cottonseed salad oil typically has extended cold test times of between 12 and 20 hr (Table 7.4). In general, winterization is a subclass of temperature-controlled oilfractionation techniques that include dry-, detergent-, and solvent-fractionation processes. Solvent winterization of cottonseed oil produces a stearin fraction that has a greater percentage of saturated fatty acids, lower iodine value, and higher solid-fat indices than conventional dry winterization (O’Brien et al. 2005). Vegetable oil hydrogenation has been a widely used catalytic process that adds hydrogen atoms to the unsaturated double bonds of the glyceride fatty acids. The technique is used to modify melting profiles and to increase oxidative stability. The former property allows more oil to be formulated into solid-fat products, for example shortenings and margarines, while the latter property is useful for extending the working life of frying oils. The process is typically conducted at elevated temperatures with hydrogen gas in the presence of metal (usually nickel) catalysts. Cottonseed oils are regularly used in hydrogenation processes. Characterization of cottonseed oil hydrogenation products at various iodine values is given by O’Brien et al. (2005). Because partial hydrogenation results in the formation of trans-unsaturated fatty acids that have been associated with increased levels of LDL-serum cholesterol, oil hydrogenation is undergoing some reevaluation within the food industries. Blending and interesterification of liquid oils with fats and fully saturated oil basestocks all have roles in the reformulation of these types of products to reduce trans-oriented fatty acids. It is also likely that cottonseed oil will have a role to play in this effort, as its greater level of saturation should reduce the degree of hydrogenation that is needed to produce products with comparable melting and stability profiles.

7.7

COTTONSEED OIL USES

Cottonseed oil is used almost entirely in the production of edible products. Food uses of vegetable oils can be divided into the categories of liquid or cooking oils, salad oils, margarines, shortening and other products. Cottonseed oil is used in all of these applications. In 2002, approximately half of the cottonseed oil produced in the United States was used as a liquid or cooking oil; a quarter of the supply was used in shortenings; exports accounted for 16% of the oil; a small amount (maybe 2%) was used in margarines and spreads; and the remainder (∼6%) was used for other purposes (O’Brien et al. 2005). Cottonseed stearin is frequently used in the formulation of cocoa butter substitutes (Gregory et al. 1999). In the United States, essentially all cottonseed oil is bought and used as a commodity product, and

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the oil is no longer readily available at retail. The exception to this is that the oil can be found in specialty stores where it is sold as premium-quality frying oil. In large cottonproduction areas outside the United States, cottonseed oil is normally used locally as a cooking oil. In one special application of note, cottonseed oil is used in the formulation of Proctor & Gamble’s Olestra or Olein products, non-digestible fat substitutes made by esterifying vegetable oil fatty acids to sucrose. Despite its less prominent role in the oil and fat industries, cottonseed oil retains an important place in the food-processing industry, which becomes apparent in the difference in soybean and cottonseed oil prices that occurs during times of tight oil supplies. Most recently this was the case in the autumn of 2007, when concerns regarding the use of oils for biodiesel caused prices to spike, resulting in a 25–30 US¢ per pound premium for cottonseed oil over soybean oil. By inference, the oil must still be essential for some commoditytype applications. Beyond the food arena, cottonseed oil has small-volume uses in specialty soap manufacture, as a lubricant and a mold-release agent, as a pharmaceutical, fabric coating, and pesticide dispersant, in formulated protective coatings, in rubber formulations, and in processes for the manufacture of leather, flame-resistant textiles, inks, polishes and coatings, plastics, and resins.

7.8

CO-PRODUCT USES

Cottonseed meal is used primarily for its protein content as a ruminant feed ingredient. Ruminant diets can be formulated with substantial amounts of cottonseed products. For example, 15–20% of a dairy cow’s ration can be made up of a combination of cottonseed and cottonseed meal (Calhoun 2002), generally without concern for gossypol toxicity. In addition to its use as a protein source, specially formulated cottonseed meals, such as the Trader’s Protein products Proflow and Pharmamedia, are used in media for the fermentation of antibiotics, enzymes, and steroids, as well as biological pesticides and herbicides. A minor amount of cottonseed meal is marketed as a formulated fertilizer for potted plants. Cottonseed hulls are used primarily as roughage in cattle and dairy feeds, where they are employed as a bulking agent to reduce digestive disturbances. In addition, the hulls are also used as a component of oil well drilling mud, and they are valued as a component of the growth medium for mushroom production. As mentioned above, cottonseed linters have a variety of uses, which fall into two classes, chemical and non-chemical. First-cut linters, which are longer (<15 mm length) tend to be used in non-chemical applications, whereas the shorter second-cut linters (<8 mm length) are pulped and used in chemical applications (Van Wyck 1948). Some first-cut linters are used in the manufacture of absorbent cotton products, for example medical pads and gauzes. A much greater quantity is used to produce felts or batting for use in bedding products and in cushioning for furniture and automobile panels. Linters are also used together with longer cotton fibers in the manufacture of paper currency. Because linters are composed principally of pure cellulose, they are an important raw material to the chemical industry and are used in applications where the impurities present in wood pulps can be problematic. Second-cut linters are pulped by digesting, bleaching, and washing of the fibers. The pulp is then used as a bulking agent in many food and household products, including ice cream and toothpaste. It is also used to form acetates and other derivatives that are employed in photographic films, tape, and packaging products as well as in the production of plastics and molding

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products, such as instrument panels, signs, toys, flexible pipe, and tool handles. A substantial volume of linter pulp is used in the manufacture of high-grade bond paper. Linter pulp is also employed in the formulation of items such as sausage casings, fingernail polishes, gunpowder, furniture lacquer, laminates, industrial and automotive filters, and regenerated cellulose polymers.

REFERENCES Ahmad, S., Anwar, F., Hussain, A.I., Ashraf, M. and Awan, A.R. (2007) Does soil salinity affect yield and composition of cottonseed oil? Journal of the American Oil Chemists Society, 84, 845–851. Badami, R.C. and Patil, K.B. (1981) Structure and occurrence of unusual fatty acids in minor seed oils, Progress in Lipid Research, 19, 119–183. Bailey, A.E. (1948) Cottonseed oil, in Cottonseed and Cottonseed Products (ed. A.E. Bailey), Interscience, New York, pp. 364–408. Bailey, C.A., Stipanovic, R.D., Ziehr, M.S. et al. (2000) Cottonseed with a high (+)- to (−)-gossypol enantiomer ratio favorable to broiler production, Journal of the American Oil Chemists’ Society, 48, 5692–5695. Bell, A.A., Puckhaber, L.S., Kim, H.L., Stipanovic, R.D. and Percival, E. (2000) Genetic approaches for increasing percentages of (+)-gossypol levels in cotton, in Genetic Control of Cotton Fiber and Seed Quality (eds C. Benedict and G. Jividen), Cotton, Inc., Cary, NC, pp. 218–230. Bernardi, L.C. and Goldblatt, L.A. (1980) Gossypol, in Toxic Constituents of Plant Foodstuffs (ed. I.E. Liener), 2nd edn, Academic Press, New York, pp. 183–237. Bland, J.M., Conkerton, E.J. and Abraham, G. (1991) Triacylglyceride composition of cottonseed oil by HPLC and GC, Journal of the American Oil Chemists’ Society, 68, 840–843. Bottger, G.T., Sheehan, E.T. and Lukefahr, M.J. (1964) Relation of gossypol content of cotton plants to insect resistance, Journal of Economic Entomology, 57, 283–285. Calhoun, M. (2003) Cottonseed Meal and Whole Cottonseed: Optimizing Their Use in Dairy Cattle Rations, National Cottonseed Products Association, Cordova, TN, http://www.cottonseed.com/publications. Carter F.L., Castillo, A.E., Frampton, V.L. and Kerr, T. (1966) Chemical composition studies of seeds of the genus Gossypium, Phytochemistry, 5, 1103–1112. Cass, Q.B., Tiritan, E., Matlin, S.A. and Freire, E.C. (1991) Gossypol enantiomer ratios in cotton seeds, Phytochemistry, 30, 2655–2657. Chapman, K.D., Austin-Brown, S., Sparace, S.A. et al. (2001) Transgenic cotton plants with increased seed oleic acid content, Journal of the American Oil Chemists’ Society, 78, 941–947. Cherry, J.P. (1983) Cottonseed oil, Journal of the American Oil Chemists’ Society, 60, 312A–319A. Cherry, J.P. (1985) Cottonseed lecithin, in Lecithins (eds B.F. Szuhaj and G.R. List), AOCS Press, Champaign, IL, pp. 57–78. Cooper, M.R. (1948) History of cotton and the United States cottonseed industry, in Cottonseed and Cottonseed Products (ed. A.E. Bailey), Interscience, New York, pp. 3–50. D’Alonzo, R.P., Kozarek, W.J. and Wade, R.L. (1982) Glyceride composition of processed fats and oils as determined by glass capillary gas chromatography, Journal of the American Oil Chemists’ Society, 59, 292–295. Dodou, K. (2005) Investigations on gossypol: Past and present developments, Expert Opinion on Investigational Drugs, 14, 1419–1434. Dowd, M.K. (1996) Compositional characterization of cottonseed soapstocks, Journal of the American Oil Chemists’ Society, 73, 1287–1295. Dowd, M.K. and Pelitire, S.M. (2001) Recovery of gossypol acetic acid from cottonseed soapstock, Industrial Crops and Products, 14, 113–123. Eaves, P.H., Dupuy, H.P., Holzenthal, L.L., Rayner, E.T. and Brown L.E. (1968) Elimination of the Halphen response of cottonseed oils in conjunction with deodorization, Journal of the American Oil Chemists’ Society, 45, 293–295. FAO/WHO Food Standards (1999) Standard #210. Standard for named vegetable oils. Available at http:// www.codexalimentarius.net/web/standard_list.do?lang=en, accessed October 2010. Fisher, G.S. and Cherry, J.P. (1983) Variation of cyclopropenoid fatty acids in cottonseed lipids, Lipids, 18, 589–594.

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Gdaneic, M., Ibragimov, B.T. and Talipov S.A. (1996) Gossypol, in Comprehensive Supramolecular Chemistry, Vol 6. Solid-state Supramolecular Chemistry: Crystal Engineering (eds D.D. MacNicol, F. Toda and R. Bishop), Pergamon Press, Oxford, pp. 117–145. Gregory, S.R., Hernandez, E. and Savoy, B.R. (1999) Cottonseed processing, in Cotton: Origin, History, Technology, and Production (eds W.C. Smith and J.T. Cothren), John Wiley & Sons, Inc., New York, pp. 793–823. Gupta, M.K. (1998) NuSun – the future generation of oils, INFORM, 9, 1150–1154. Haire, R. (2009) Biotech cotton in international trade, Biosafety Regulations, Implementation and Consumer Acceptance, International Cotton Advisory Committee, Washington, DC, 63(1), 10–13. Hamilton, K.A., Pyla, P.D., Breeze, M. et al. (2004) Bollgard II cotton: Compositional analysis and feeding studies of cottonseed from insect-protected cotton (Gossypium hirsutum L.) producing the Cry1Ac and Cry2Ab2 proteins, Journal of Agricultural Food Chemistry, 52, 6969–6976. Hendrix, B. (1984) Current practices in continuous cottonseed miscella refining, Journal of the American Oil Chemists’ Society, 61, 1369–1372. Hron, R.J. Sr., Kim, H.L., Calhoun, M.C. and Fisher G.S. (1999) Determination of (+)- and (−)- and total gossypol in cottonseed by high performance liquid chromatography, Journal of the American Oil Chemists’ Society, 76, 1351–1355. ICAC (2009a) Cotton: Review of the world situation, 62(4), International Cotton Advisory Committee, Washington, DC. ICAC (2009b) Cotton: Review of the world situation, 63(2), International Cotton Advisory Committee, Washington, DC. Itoh, T., Tamura, T. and Matsumoto, T. (1973) Sterol composition of 19 vegetable oils, Journal of the American Oil Chemists’ Society, 50, 122–125. Jones, L.A. and King, C.C. (eds) (1990) Cottonseed Oil, National Cottonseed Products Association, Memphis, TN. Jones, L.A. and King, C.C. (1996) Cottonseed, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (ed. Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 159–227. Jurriens, G. and Kroesen, C.J. (1965) Determination of glyceride composition of several solid and liquid fats, Journal of the American Oil Chemists’ Society, 42, 9–14. Kenar, J.A. (2006) Reaction chemistry of gossypol and its derivatives, Journal of the American Oil Chemists’ Society, 83, 269–302. Kim, H.L. Calhoun, M.C. and Stipanovic, R.D. (1996) Accumulation of gossypol enantiomers in ovine tissues, Comparative Biochemistry and Physiology, 113B, 417–420. Kuo, T.M., VanMiddlesworth, J.F. and Wolf, W.J. (1988) Content of raffinose oligosaccharides in various plant seeds, Journal of Agricultural Food Chemistry, 36, 32–36. Lawhon, J.T., Cater, C.M. and Mattil, K.F. (1977) Evaluation of the food potential of sixteen varieties of cottonseed, Journal of the American Oil Chemists’ Society, 54, 75–80. List, G.R. and Friedrich, J.P. (1989) Oxidative stability of seed oils extracted with supercritical carbon dioxide, Journal of the American Oil Chemists’ Society, 66, 98–101. Liu, Q., Singh, S.P. and Green, A.G. (2002) High-stearic and high-oleic cottonseed oils produced by hairpin RNA-mediated post-transcriptional gene silencing, Plant Physiology, 129, 1732–1743. Lordelo, M.M., Davis, A.J., Calhoun, M.C., Dowd, M.K. and Dale, N.M. (2005) Relative toxicity of gossypol enantiomers in broilers, Poultry Science, 84, 1376–1382. Lordelo, M.M., Calhoun, M.C., Dale, N.M., Dowd, M.K. and Davis A.J. (2007) Relative toxicity of gossypol enantiomers in laying and broiler breeder hens, Poultry Science, 86, 582–590. Lukonge, E., Labuschagne, M.T. and Hugo, A. (2007) The evaluation of oil and fatty acid composition in seed of cotton accessions from various countries, Journal of the Science of Food Agriculture, 87, 340– 347. Morgan, D.A. (1942) Smoke, fire, and flash points of cottonseed, peanut and other vegetable oils, Oil & Soap, 19, 193–198. Müller-Mulot, W. (1976) Rapid method for the quantitative determination of individual tocopherols in oils and fats, Journal of the American Oil Chemists’ Society, 53, 732–736. National Coordinating Group on Male Antifertility Agents (1978) Gossypol: A new antifertility agent for males, Chinese Medical Journal, 4, 417–428. McMichael, S.C. (1959) Hopi cotton: A source of cottonseed free of gossypol pigments, Agronomy Journal, 51, 630.

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223

NCPA Trading Rules (2008) National Cottonseed Products Association, Cordova, TN, http://www. cottonseed.com/tradingrules. Nergiz, C., Yalçin, H. and Yildiz, H. (1997) Some analytical characters of cottonseed varieties grown in Turkey, Grasas y Aceites, 48, 411–414. Norris, F.A. (1982) Extraction of fats and oils, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (ed. D. Swern), 4th edn, John Wiley & Sons, Inc., New York, pp. 175–251. O’Brien R.D., Jones, L.A., King, C.C., Wakelyn, P.J. and Wan, P.J. (2005) Cottonseed oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2, Edible Oil and Fat Products: Edible Oils (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 173–279. Percy, R.G., Calhoun, M.C. and Kim, H.L. (1996) Seed gossypol variation within Gossypium barbadense L. cotton, Crop Science, 36, 193–197. Phelps, R.A., Shenstone, F.A., Kemmerer, A.R. and Evans, R.J. (1965) A review of cyclopropenoid compounds: Biological effects of some derivatives, Poultry Science, 44, 358–394. Pons, W.A. Jr., Pominski, J., King, W.H. and Hopper, T.H. (1959) Recovery of gossypol from cottonseed gums, Journal of the American Oil Chemists’ Society, 36, 328–332. Radcliffe, J.D., Czajka-Narins, D.M. and Imrhan V. (2004) Fatty acid composition of serum, adipose tissue, and liver in rats fed diets containing corn or cottonseed oil, Plant Food and Human Nutrition, 59, 73–77. Schaible, P.J., More, L.A. and Moore, J.M. (1934) Gossypol, a cause of discolorization in egg yolks, Science, 79, 2051. Slover, H.T., Lehmann, J. and Valis, R.J. (1969) Vitamin E in foods: Determination of tocols and tocotrienols, Journal of the American Oil Chemists’ Society, 46, 417–420. Smith, N.E., Collar, L.S., Bath, D.L., Dunkley, W.L. and Franke, A.A. (1981) Digestibility and effects of whole cottonseed fed to lactating cows, Journal of Dairy Science, 64, 2209–2215. Stansbury, M.F., Cirino, V.O. and Pastor, H.P. (1957) Composition of acidified cottonseed soapstocks as influenced by commercial methods of processing seed and oil, Journal of the American Oil Chemists’ Society, 34, 539–544. Stansbury, M.F., Hoffpauir, C.L. and Hopper, T.H. (1953) Influence of variety and environment on the iodine value of cottonseed oil, Journal of the American Oil Chemists’ Society, 30, 120–123. Stansbury, M.F., Pons, W.A. Jr., and Den Hartog, G.T. (1956) Relations between oil, nitrogen, and gossypol in cottonseed kernels, Journal of the American Oil Chemists’ Society, 33, 282–286. Stipanovic, R.D., Lopez, J.D., Dowd, M.K., Puckhaber, L.S. and Duke S.E. (2006) Effect of racemic and (+)- and (−)-gossypol on the survival and development of Helicoverpa zea larvae, Journal of Chemical Ecology, 32, 959–968. Stipanovic, R.D., Puckhaber, L.S., Liu, J. and Bell, A.A. (2009) Total and percent atropisomers of gossypol and gossypol-6-methyl ether in seeds from Pima cottons and accessions of Gossypium barbadense L, Journal of Agricultural Food Chemistry, 57, 566–571. Sunilkumar, G., Campbell L.M., Hossen, M. et al. (2005) A comprehensive study of the use of a homologous promoter in antisense cotton lines exhibiting a high seed oleic acid phenotype, Plant Biotechnology Journal, 3, 319–330. Sunilkumar, G., Campbell, L.M., Puckhaber, L., Stipanovic, R.D. and Rathore, K.S. (2006) Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol, Proceedings of the National Academy of Sciences, 103, 18054–18059. Tharp, W.H. (1948) Cottonseed composition – relation to variety, maturity, and environment of the plant, in Cottonseed and Cottonseed Products (ed. A. E. Bailey), Interscience, New York, pp. 117–156. Thompson, A.C., Henson, R.D., Hedin, P.A. and Minyard, J.P. (1968) Constituents of the cotton bud: XII. The carotenoids in buds, seeds and other tissues, Lipids, 3, 495–497. Van Wyck, P. (1948) Cotton linters, in Cottonseed and Cottonseed Products (ed. A.E. Bailey), Interscience, New York, pp. 894–905. Verleyen, T., Forcades, M., Verhe, R. et al. (2002) Analysis of free and esterified sterols in vegetable oils, Journal of the American Oil Chemists’ Society, 79, 117–122. Wan, P.J., Dowd, M.K., Thomas, A.E. and Butler, B.H. (2007) Trimethylsilyl derivatization/gas chromatography as a method to determine the free fatty acid content of vegetable oils, Journal of the American Oil Chemists’ Society, 84, 701–708. Wang, X., Page Howell, C., Chen, F., Yin, J. and Jiang, Y. (2009) Gossypol – a polyphenolic compound from cotton plant, Advances in Food Nutrition Research, 58, 215–263. Watkins, C. (2009) Oilseeds of the future: Part 2, INFORM, 20, 342–344.

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Willhite, G. (2008a) 1910–1918: Getting started. Methods, Smalley’s samples, and independence, INFORM, 19, 307–312. Willhite, G. (2008b) 1919–1928: A new decade, a new name. Of walnut trees, a Wesson hoax, and a new journal, INFORM, 19, 370–374. Wrenn, L.B. (1995) Cinderella of the New South: A History of the Cottonseed Industry, 1855–1955, University of Tennessee Press, Knoxville, TN. Yunusova, S.G., Gusakova, S.D., Glushenkova, A.I. et al. (1991) A comparative investigation of the fatty acid compositions of the seeds of a number of lines of a genetic collection of Gossypium hirsutum, Chemistry of Natural Compounds, 27, 147–150.

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8

Groundnut (Peanut) Oil

Lisa L. Dean, Jack P. Davis, and Timothy H. Sanders

8.1

PEANUT PRODUCTION, HISTORY, AND OIL EXTRACTION

Groundnut oil is expressed from the seed of Arachis hypogaea L., commonly known as groundnut, peanut, or earth nut because the seeds develop underground. Groundnuts are produced on a significant basis in more than 30 countries, with worldwide production figures estimated to be in excess of 30 million metric tons (USDA FAS, Table 13, Peanut Area, Yield and Production). The plant itself is a legume native to South America and was probably cultivated as early as 2000–3000 bc (Hammons 1973). Peanut seeds grown in the British American colonies were discussed as a source of oil to rival olive oil (Watson 1769). Near the middle of the nineteenth century, British and French oil mills began importing groundnuts from West Africa for crushing (Brooks 1975). The excellent quality of the oil resulted in mills for crushing being located throughout Europe soon after, and eventually throughout the world. The world production of groundnuts is about 7% of the world production of oilseeds, but because of the limited extraction of groundnuts, the annual production of groundnut oil is only about 4% of the world vegetable oil total (see Chapter 1). Uses in various countries differ greatly, but overall more than 50% of all groundnuts produced are crushed for oil. Whereas in India 75–80% of the groundnut crop is crushed for oil due to high demand, in contrast in the US only 10–12% of the groundnuts produced are crushed. This low percentage is indicative of the economic importance of the nuts themselves as a food crop in the US. Due to the high content of digestible protein and unsaturated oil and the exceptional roasted nutty flavor, groundnuts have substantial value as a nutritious and flavorful food commodity. More than one third of the groundnuts produced are used as food in the form of intact nuts on a worldwide basis. In the US, a high percentage of the limited number of groundnuts used for oil extraction have been separated from edible stocks because of the potential for aflatoxin contamination. After minimal oil extraction, the pressed cake, which is low in oil and high in protein, may be used for animal feed if aflatoxin is kept below acceptable levels. Aflatoxin is a potentially carcinogenic compound produced by Aspergillus flavus and Aspergillus parasiticus that can invade peanuts, corn, cottonseed, and other commodities. Control and testing programs are in place in technologically advanced countries and the Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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concentrations of aflatoxin are usually quite low in edible peanuts; however, the same may not be true in developing countries. Aflatoxin is generally associated with the protein portion of peanuts and therefore is generally not found in refined oil (Parker and Melnick 1966). Crude or lightly processed oil containing fines may contain some aflatoxin. Unacceptable pressed cake and much of the material remaining after physical and chemical extraction is relegated to fertilizer usage. Residue from oil processing may contain from 1–7% oil depending on whether the extraction was accomplished by hydraulic press, expeller, and/or solvent extractors. With inefficient equipment, the percentage oil remaining in the residue may be even higher. Pressed cake from edible-grade groundnuts with low oil content may be ground into flour for human consumption. In many parts of the world, extraction efficiency and lack of hygienic conditions yield residues unfit for human consumption. In these situations, the residue is utilized either for animal feed or as fertilizer (Woodroof 1983).

8.2 8.2.1

OIL USES Frying and food

Throughout the world, frying and cooking constitute by far the greatest use of peanut oil. It is especially suitable for deep-fat frying due to its high smoke point of 229 °C (Woodruff 1983). This high temperature allows food to cook quickly with a crisp coating and little oil absorption. Off flavor and odor development are very limited during frying with groundnut oil. However, degradation of triacylglycerols occurring during frying results in an increase of free fatty acids (FFA) and a decrease in smoke point. In a comparison of various frying oils on consumer acceptability of salted, fried peanuts, peanuts prepared from refined peanut oil were better accepted than those prepared with other vegetable oils such as sunflower, corn, soybean, and olive oils (Ryan et al. 2008). Crude groundnut oil has a nut-like odor but after refining the oil becomes odorless. This makes it useful in the preparation of shortenings, margarines, and mayonnaise. The high solidification point (0–3 °C) prevents it from meeting the strict specification for salad oil (Pattee 2005); however, as discussed later, work is ongoing to improve the cold-flow properties of peanut oil (Davis and Sanders 2007). There is some use of it as a salad oil for pourable dressings because of the length of time solids are held in suspension in the oil. Peanut oil is the main ingredient in vanaspati, a hydrogenated product make in India that resembles natural butter and ghee in appearance (Salunke and Desai 1986). It is used as a vegetable ghee substitute. Roasted peanut oils, highly aromatic oils, and peanut extract are high-value products with strong peanut flavor and nut aroma (Chiou et al. 1993). These products have applications in flavor compounds, confections, sauces, baked goods, breakfast cereals, flavorings, frozen dairy desserts, and flavor compound bases. Peanut oil is generally subjected only to standard extraction procedures and uses of peanut oil generally do not require even limited hydrogenation. However, hydrogenated vegetable oils are added at a 1–2% level to peanut butter as a (physical) stabilizer. Due to the nutritional interest in trans-fatty acids, major US brands of peanut butter were examined for the presence of trans-fatty acids, but no trans fats were detected in any of the samples using an analytical system with a detection limit of 0.01% (Sanders 2001). Recent studies, employing newer methodology capable of lower detection limits, indicated in some cases that very

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Table 8.1 peanuts.

227

Influence of maturity on quantity and composition of selected oil components of Florunner

Maturity stage* 5 6 7 8 9 10 11 12

Oil (% dry weight)

Triacylglycerol**

FFA**

Diacyl-glycerol**

Polar lipids**

25.3 30.8 34.4 42.8 45.6 46.7 48.4 48.2

85.3 89.3 88.3 90.8 92.6 94.3 94.8 95.8

4.5 3.1 2.5 1.8 1.3 0.9 0.7 0.7

4.7 3.5 3.6 3.0 2.2 2.0 1.9 1.7

2.0 1.4 1.9 1.6 1.3 1.0 0.7 0.6

Notes: * Relative maturity ranking based on internal shell color. At stage 5 seed are soft and watery, at stage 12 they are fully mature. ** Relative weight percentage.

low levels of trans-fatty acids were present in commercial peanut butter. (L.L. Dean, unpublished data). These recent findings are in line with the addition of low levels of stabilizer, themselves containing very low levels of trans-fatty acids.

8.2.2

Feed

Non-food uses of peanut oil include animal feed. Peanut oil has been tried as the lipid source in fish rations along with other vegetable oils. Use of vegetable oils would reduce the demand for fish oils for this purpose (Lin et al. 2007). Although growth is not affected, the oil profiles of the finished product reflect the feed oil and, as a result, fish and shrimp have higher levels of monounsaturated fatty acids, but decreased levels of the higher-value polyunsaturated fatty acids EPA and DHA (Narciso et al. 1999; Zhou et al. 2007).

8.3 8.3.1

COMPOSITION OF GROUNDNUT OIL Oil in seed

Although a range of 36–56% has been reported for oil content, groundnuts commonly contain 40–50% oil. Oil content is commonly considered to be about 48–50% and is generally independent of market type or growth habit (Cobb and Johnson 1973). The triacylglycerol content of the oil is generally 95%, with some differences among varieties. Maturation of the seed results in increases in total oil, triacylglycerol, and ratio of oleic acid to linoleic acid (O/L), while free fatty acids, polar lipids, monoacylglycerols, and diacylglycerols decrease (Sanders 1980a; Table 8.1). The relative proportions of many components affecting the shelf-life of oil change dramatically as peanuts mature. Immature peanuts have a substantially lower shelf-life than mature peanuts because of oil structure and composition, including the oleic/linoleic (O/L) ratio. O/L ratio and oven stability both increase with maturity (Sanders et al. 1982). The consistent relationship of these components to shelf-life leaves little doubt as to the relationship of maturity and shelf-life. Diacylglycerol and polar lipid fractions generally account for an additional 2% of the oil weight. Some reports suggest that

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Table 8.2 Major fatty acids in groundnut oil (% wt). Fatty acid

Percentage

Palmitic Stearic Oleic Linoleic Arachidic Behenic Lignoceric

7.4–12.5 2.7–4.9 41.3–67.4 13.9–35.4 1.2–1.9 2.1–3.6 0.9–1.7

total oil percentage decreases after full maturation as lipids are utilized for respiration (Ahmed and Young 1982). Factors such as maturity, environment, cultural practices, variety, and soil temperature affect oil content and composition.

8.3.2

Fatty acids

Groundnut oil contains a high proportion of unsaturated fatty acids, in particular oleic (18:1), linoleic (18:2), and 11-eicosenoic (20:1). The saturated fatty acids in groundnut oil are palmitic (16:0), stearic (18:0), arachidic (20:0), behenic (22:0), lignoceric (24:0), and hexacosanoic (26:0). Palmitic is the only saturated fatty acid that exceeds 10%. The very long-chain fatty acids (those above 22 carbons) are usually found at or about 2% each. These fatty acids have been associated with widely varying effects, such as the metabolism of the dietary fatty acids and the physical properties of the oils themselves (Dean and Sanders 2009). The oxidative stability of groundnut oil is highly correlated with the ratio of oleic acid to linoleic acid (Fore et al. 1953). This ratio generally increases with seed maturity and oil stability increases simultaneously. Fatty acid composition values for peanut oil have been reported to vary widely (Worthington et al. 1972), as indicated in Table 8.2. Principal component analyses were applied to the fatty acid profiles of oils from various runner cultivars grown in the US (Shin et al. 2010). This approach allows for a fuller understanding of variation among samples and could be useful in streamlining breeding efforts. The fatty acid composition of specific lipid classes in groundnut oil are somewhat variable. The composition of three groundnut varieties and the composition of lipid classes from those varieties are shown in Table 8.3 (Sanders 1980b). The fatty acid composition of the triacylglycerol is similar to that of whole oil, since this fraction comprises about 95% of the total. Free fatty acid fractions consistently contained higher percentages of palmitic acid than did the triacylglycerol fractions. Long-chain fatty acids (20–26 carbons) were generally more predominant in the sn-1,3-diacylglycerol than in other fractions, and only traces of these long-chain fatty acids are found in the sn-1,2 (2,3) diacylglycerol fraction. The phospholipid fractions contained the highest concentrations of palmitic acid. Cooler production climates result in a greater degree of unsaturation, a lower O/L ratio, and thus a shorter shelf-life (Holaday and Pearson 1974). Factors of temperature, irrigation, and maturity have also been variously described as affecting degree of unsaturation. Oil composition is affected by mean temperature at critical growth periods. This relationship

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Table 8.3 Fatty acid composition (mole %) of various lipid classes in petroleum ether-extracted Starr, Florunner, and Florigiant peanut oil. Variety

Lipid class

16:0

18:0

18:1

18:2

20:0

20:1

22:0

24:0

Starr

TAG FFA sn -1,3-DAG sn -1,2(2,3) DAG MAG PL WO TG FFA sn -1,3-DAG sn -1,2(2,3) DAG MAG PL WO TAG FFA sn -1,3-DAG sn -1,2(2,3) DAG MAG PL WO

14.1 21.0 17.7 15.5

3.3 4.2 3.8 2.5

44.6 40.4 48.2 48.9

32.1 29.9 22.9 33.1

1.5 1.2 1.5 –

0.8 0.4 1.2 –

2.7 2.2 3.4 –

0.9 0.8 1.3 –

17.9 22.3 14.0 11.4 16.9 13.8 13.6

2.4 3.6 2.6 2.3 3.0 2.6 1.5

46.5 44.8 43.9 51.9 45.0 51.5 48.6

27.8 24.6 34.2 28.5 30.1 25.1 36.3

0.8 0.8 1.3 1.2 1.1 1.2 –

0.8 1.0 0.8 1.2 1.2 1.6 –

2.4 1.6 2.5 2.4 1.9 2.4 –

1.4 1.2 0.8 1.2 0.8 1.4 –

16.1 21.3 11.0 11.2 16.1 13.2 12.6

3.3 3.4 1.8 3.5 3.9 3.9 2.2

47.9 45.1 51.7 52.7 46.6 52.1 48.9

27.4 28.9 29.9 26.6 28.2 22.2 35.8

0.7 – 1.0 1.5 1.6 2.4 –

0.6 – 1.1 0.9 1.0 1.7 –

3.2 0.7 2.4 2.3 1.9 3.4 0.3

0.8 0.7 1.1 1.2 0.7 1.2 0.3

16.7 22.1 11.0

4.4 3.8 2.8

48.4 42.8 54.3

26.8 29.0 27.2

0.8 0.4 1.3

– – 0.9

2.3 1.0 2.0

0.6 0.9 0.8

Florunner

Florigiant

Notes: All values are the means of three replicate analyses. () = Oil extracted with chloroform/methanol (2:1, v/v). Key: DAG = diacylglycerol FFA = free fatty acid MAG = monoacylglycerol PL = polar lipid TAG = triacylglycerol WO = whole oil

may provide a partial explanation for observed problems with oxidative stability in peanuts grown in cooler climates or with cooler temperatures during the latter weeks of the growing season. Holaday and Pearson (1974) demonstrated highly significant variations in oil production from year to year for all three major peanut types, highly significant differences among the same varieties grown in different commercial production areas, and highly significant interactions between location and year of production.

8.3.3

High-oleic peanut oil

Peanut lines with a high-oleic acid trait have been identified, and this trait has been incorporated into commercial peanut varieties. The original two lines identified had approximately 80% oleic and 2% linoleic acid (Norden et al. 1987). The lines developed with the higholeic acid trait have O/L ratios of approximately 30, but the lines do not have meaningful

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differences in oil content, flavor, color, or texture. Oxidative stability comparisons made on extracted, neutralized, and bleached oil from high oleic (75.6% oleic and 4.7% linoleic) and conventional lines (56.1% oleic and 24.2% linoleic), differing only in fatty acid composition, resulted in up to about 15 times greater oxidative stability in the high oleic oil (O’Keefe et al. 1993). Use of high-oleic oil in the roasting of peanuts resulted in slight increases in shelf-life as measured by oxidative stability and peroxide value, and the degree of improved shelf-life was related to the O/L ratio of the peanut roasted (Bolton and Sanders 2002). Work is ongoing to fully determine the genetic and biochemical pathways responsible for the high oleic trait in peanuts (Isleib et al. 2006; Chu et al. 2007; Yin et al. 2007; Yu et al. 2008). Molecular markers for breeding efforts have been recently determined in peanuts for the high oleic trait (Chu et al. 2009).

8.3.4

Triacylglycerol structure

Of the 20–36 different triacylglycerol species in peanut oil, the species OOL, OOO, OLL, POL, and POO comprise the greatest proportions (Singleton and Pattee 1987); O = oleic, L = linoleic, P = palmitic and these three letter symbols include all triacylglycerols with the three acyl groups indicated. This is expected since oleic acid, linoleic acid, and palmitic acid are the major fatty acids in peanut oil. Triacylglycerol species distribution has been utilized by the US Customs Service as one method of identification of the international origins of peanuts (Pettitt et al. 1992). Observations for distinguishing between the two production locations were: ●

●

●

●

The ratio OOO/OOP was less than 1.0 for Chinese peanuts and approximately 1.5–1.7 for the Argentinean peanuts. PSL (S = stearic) was not measurable in Chinese peanuts and was present at about 0.2% in Argentinean samples. In Chinese samples, OOB (B = behenic) accounted for about 0.4% of the total triacylglycerols, while in the Argentinean samples it accounted for about 1.1%. The percentage of OOO was ∼10% in Chinese samples versus ∼14% in Argentinean samples.

The percentage ranges of triacylglycerol species for Argentinean and US samples often overlap; however, origin identification was possible through trace element analysis. Several studies have demonstrated that environmental factors affect not only the fatty acid composition of peanut oil, but also, although apparently indirectly, the spatial arrangement of those acids on the triacylglycerol molecule (Sanders 1979; Sanders 1982). Triacylglycerol composition and structure are important in the areas of nutrition, oil stability, and possible physiological effects. Table 8.4 provides data demonstrating the differences in triacylglycerol structure reasonably expected among different varieties of peanuts. The data shown in Table 8.4 indicate a non-random distribution of fatty acids among the sn-1, -2, and -3 positions of the triacylglycerols. The percentages of palmitic and stearic acids were generally very low for the sn-2 position, higher for sn-3, and highest for sn-1. The longchain fatty acids (20–26 carbons) were located almost exclusively at the sn-3 position (Jakab et al. 2002). The sn-2 position of triacylglycerols from all the varieties was high in unsaturated fatty acids. The general pattern of fatty acids found at the sn-1 and sn-3 positions was similar for all varieties, although the mole percentages of each acid at the two positions frequently differed widely. Mole percentages of palmitic, stearic, and linoleic acids were

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231

Stereospecific analyses of triacylglycerols from three peanut varieties.

Variety

Compound or position

16:0

18:0

18:1

18:2

20:0

20:1

22:0

24:0

Florigiant

TAG 1 2 3 TAG 1 2 3 TAG 1 2 3

10.8 20.1 2.2 10.3 11.4 20.7 2.1 11.4 14.2 24.2 2.4 16.0

2.9 4.9 0.7 3.2 2.1 3.5 0.6 2.3 3.3 4.9 0.8 4.2

53.1 50.7 51.5 57.2 50.9 49.5 47.8 55.5 43.3 40.4 39.5 50.0

27.3 22.6 45.3 14.0 29.1 24.4 48.8 14.1 33.0 28.4 56.9 13.8

1.8 0.5 0.1 4.8 1.6 0.3 0.1 4.4 1.8 0.4 0.1 4.8

1.0 0.7 0.3 2.0 1.1 0.7 0.4 2.3 1.1 0.6 0.2 2.4

1.9 0.4 0.1 5.3 2.4 0.5 0.1 6.5 2.7 0.7 0.1 7.3

1.1 0.3 – 3.0 1.3 0.5 0.1 3.4 0.7 0.3 – 1.8

Florunner

Starr

always higher for the sn-1 than for the sn-3 position, while those of oleic acid were consistently higher for the sn-3 position. The patterns of fatty acid distribution at sn-2 differed not only from those at sn-1 and -3, but with variety as well. Plots of the percentage of a fatty acid in the total triacylglycerol vs. the percentage of that fatty acid at one of the positions of the triacylglycerol obtained from Table 8.4 and from additional varieties were subjected to linear regression analysis and determination of correlation coefficients (Sanders 1982). Major saturated, monoene, and diene fatty acids of corn triacylglycerols exhibited a concentration effect in all cases, except for saturated acids in the sn-2 position (De La Roche et al. 1971). Peanut triacylglycerols exhibited this same pattern, and the low concentrations of the long-chain fatty acids in the triacylglycerol were significantly correlated with percentages found at the sn-3 position only. Hexacosanoic acid (26:0) was almost always found associated with unsaturated fatty acids and in most cases with two molecules of linoleic acid (18:2) (Sempore and Bezard 1986). This may be due to the general restriction of the saturated acids (16:0 and 18:0) from the sn-2 position and of the long-chain acids from the sn-1 and sn-2 positions. The concentration of a fatty acid in the total triacylglycerol fraction appeared to affect placement of that fatty acid on glycerol similarly for individual varieties of peanut. The variation in percentage of a fatty acid at any position indicates possible differences in the concentration of various triacylglycerol species found in the oil.

8.3.5

Phospholipids

The concentration of phospholipids in peanut oil is only about 1%. This class of compounds has been shown to be synergistic with tocopherols in delaying the onset of lipid oxidation. However, phospholipids are removed during oil refining. The major phospholipids of peanut oil are phosphatidic acids (PA), phosphatidylglycerols (PG), phosphatidylethanolamines (PE), phosphatidylinositols (PI), and phosphatidylcholines (PC). The phospholipid content and concentrations are affected by maturity and post-harvest treatment, as shown in Table 8.5 (Singleton and Stikeleather 1995). The higher concentrations of PA and PC in immature peanuts might be explained on the basis that these are precursors of other phospholipids.

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Table 8.5

Effect of post-harvest treatment on total phospholipids.

Treatment

Phospholipid (% area)

Control Immature Heat cured Freeze-damaged

PA

PG

PE

PI

PC

Total Phospholipid (mg/100 g dry wt)

2.2 4.5 9.5 28.3

2.5 2.3 1.1 14.1

13.3 14.0 16.0 15.2

15.7 7.6 15.4 33.5

66.4 71.7 58.1 8.8

500 700 900 250

Key: PA = phosphatidic acids PC = phosphatidylcholines PE = phosphatidylethanolamines PG = phosphatidylglycerols PI = phosphatidylinositols

Both excessive heat and freezing affect membrane stability as a result of significant differences in the phospholipid content and distribution. The large increase in PA and great decrease in PC with freezing of non-dried peanuts may be related to the fact that freezing induces phospholipase-D activity, particularly of PC. Hokes (1977) found that the oven stability of peanut oil was related to the solvent used for the extraction of phospholipids and that removal of phospholipids from the oil by precipitation reduced oven stability. The relative amounts of polar lipids extracted by different solvents might explain some variation in oven stability. Genetic changes to increase the disease resistance of peanuts have not resulted in oils with significantly different phospholipid profiles from oil expressed from traditional peanuts (Jonnala et al. 2006a). Similar results were found in a survey of oils from high-oleic peanut cultivars (Jonnala et al. 2006b).

8.3.6

Sterols

Peanuts contain β-sitosterol, campesterol, stigmasterol, Δ5 avenasterol, Δ7 stigmasterol, Δ7 avenasterol, and brassicasterol (Table 8.6). These sterols, which are secondary alcohols with 27–29 carbon atoms, are crystalline solids at room temperature. β-Sitosterol, the major component in peanut sterols, has been shown to inhibit cancer growth (Awad et al. 2000) and may offer protection from colon, prostate, and breast cancer. Sterols contribute to cardiovascular health due to regulation of serum cholesterol (Jones and Abumweis 2009). Unrefined peanut oil contains approximately 200 mg sitosterol/100 gm of oil, and this value is comparable to soybean oil that contains approximately 220 mg sitosterol/100 gm (Awad et al. 2000).

8.3.7

Antioxidants

Among the tocopherols, the major ones found in peanut oil are α and γ in almost equal amounts. Although the α form is considered to be the most biologically active, research has been reported showing that the γ form may have stronger effects against some toxins (Cooney et al. 1993). Data on tocopherol content and individual fatty acids from 31 cultivars for four years was used in a multiple regression equation for prediction of the stability

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Table 8.6 Sterol content of unsaponifiables of peanut oil and whole peanuts.

Total sterol β-Sitosterol Campesterol Stigmasterol Δ5-Avenasterol Δ7-Stigmasterol Δ7-Avenasterol Brassicasterol Other

Peanut oil (mg/100 g)

Whole peanuts (mg/100 g)

337 217 49 36 26 6 2 trace –

220 142 24 23 NR NR NR NR 31

Key: NR = not reported

of cold-pressed oil. This revealed that 87% of the stability could be correlated with the ratio of total tocopherol to the percentage of linoleic acid. In a multiyear study of oil-composition factors of peanuts from several origins, data indicated that tocopherol content was consistently different in peanuts from various origins (Sanders et al. 1992). Higher tocopherol content was consistently found in peanuts produced in the United States compared to those produced in China or Argentina. The highest levels reported in US peanuts on a whole-seed basis were almost 250 ppm, while the lowest levels were about 100 ppm. In extracted peanut oil, tocopherol content has been demonstrated to be as high as 650 ppm depending on the variety of peanut and growing conditions. Tocopherol contents of oils from various runner cultivars grown in the US were recently reported and analyzed using different chemometric techniques (Shin et al. 2009). The mean α-tocopherol level in Runner peanuts (151 samples) was 10.5 +/− 1.5 mg/100 g, which was more than 25% greater than the value reported in the USDA National Nutrient Database for Standard Reference of all peanuts. Tocopherol content in peanuts and extracted oils is also sensitive to the roasting process (Chun et al. 2005). Recent work has shown that the tocopherol content in oils extracted from ‘light’ and ‘medium’ roasted seed degraded more rapidly than that of oil from raw seed; however, tocopherol content in oil from darker roasted seed was actually better preserved than that derived from light or even raw seed (Davis et al. 2010). This effect is presumably due to increased concentrations of antioxidants generated/released during the roasting process, such as phenolic compounds and/or Maillard reaction components, which protect tocopherols from degradation. Research efforts have also focused on replacing synthetic antioxidants in various oils, including that of peanut. Using peanut oil in model systems, extracts from the Asian herbs Polygonum cuspidatum and Cortex fraxini were shown to be as effective as butylated hydroxytoluene (BHT) in preventing lipid oxidation (Pan et al. 2007a, b). A three-year study on peanuts from the United States, China, and Argentina reported on levels of the pro-oxidant metals copper and iron (Sanders et al. 1992). Copper content was always significantly lower in US peanuts and iron content was generally lower. These factors, along with higher O/L ratios, resulted in greatest oil oven stability and thus the overall

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Table 8.7

Chemical and physical characteristics of peanut oil.

Characteristic

Value

Flavor and odor Color (visual) Color (Gardner, maximum) Melting point Smoke point Specific gravity (21 °C) Free fatty acid (as oleic acid, maximum) Iodine value Peroxide value (maximum) Acetyl value Heat of fusion (unhydrogenated) Refractive index (nD 40 °C) Unsaponifiable lipids

Bland Light yellow 4 0–3 °C 229.4 °C 0.915 0.05% 82–106 10 meq peroxides oxygen/kg oil 8.5–9.5 21.7 cal/g 1.46–1.465 0.40%

potential for a longer shelf-life for peanuts produced in the United States. There is a consistently close relationship of oil quality factors such as O/L ratio, FFA, peroxide value, total carbonyls, tocopherols, copper, and iron to most measures of shelf-life stability. This suggests that any of these factors at inappropriate levels will contribute to a shorter shelf-life of products.

8.4 8.4.1

CHEMICAL AND PHYSICAL CHARACTERISTICS OF GROUNDNUT OIL General

Peanut oil characteristics compiled from several references are provided in Table 8.7. Unrefined peanut oil has a bland but slightly beany, nut-like flavor, which is removed during refining.

8.4.2

Color

As peanuts mature, oil color becomes lighter as β-carotene and lutein, which are responsible for the yellow color, become more diluted (Pattee and Purcell 1967). Although oil color may be used to assess maturity, other methods are preferred, because many factors such as curing temperature and duration influence oil color (Sanders et al. 1982). Color measurement is frequently done by visual comparison under a Commission Internationale de l’Eclairage (CIE) standard light source or Gardner color, which has a scale between 1 and 18.

8.4.3

Density and viscosity

Viscosity and density are important physical parameters central to the quality of vegetable oils. These properties, as summarized in Table 8.8, were surveyed as a function of temperature (5 °C to 100 °C) for oils from nine common cultivars of peanut to determine the potential for variation (Davis et al. 2008). Increasing content of oleic acid, decreasing content of

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Table 8.8 Density (ρ) and dynamic viscosity (μ) measured at 10 °C and 90 °C for oils from various peanut varieties. Variety GAGreen C11-2-39 AP-3 C99R DP-1 GA-01R FR-458** AT-201** GA-02C**

r-90 °C (g/ml)

r-10 °C (g/ml)

Slope* (mg/ml.°C)

m-90 °C (mPa.s)

m-10 °C (mPa.s)

0.86698 a 0.86687 b 0.86651 c 0.86640 d 0.86594 e 0.86562 f 0.86429 g 0.86409 h 0.86408 h

0.92054 a 0.92042 b 0.92005 c 0.91993 d 0.91945 e 0.91912 f 0.91772 g 0.91754 h 0.91754 h

−0.6695 f −0.6692 ef −0.6692 ef −0.6692 ef −0.6689 de −0.6688 cd −0.6679 a −0.6682 ab −0.6683 bc

8.8 g 8.8 f 8.9 e 8.8 f 8.9 d 9.0 c 9.2 b 9.2 b 9.3 a

126.0 g 127.0 fg 130.0 e 128.2 f 131.8 d 134.2 c 141.8 b 142.6 b 144.6 a

Notes: The same letter within a column indicates no difference (p<0.001) between means. * Slopes are from linear fits of density vs. temperature (10 °C to 90 °C). ** High oleic acid varieties. Key: ρ = density μ = dynamic viscosity

linoleic acid, and decreasing content of palmitic acid were each associated with decreased density and increased viscosity among the oils. High-oleic oils had both the lowest densities and highest viscosities, with viscosity differences being most apparent at cooler temperatures. Non-linearity of hydrocarbon chains due to unsaturation was considered to affect oil density and viscosity.

8.4.4

Melting point/crystallization

At refrigeration temperatures (0–3 °C), peanut oil typically sets to a gel. A potential application of peanut oils is as a salad oil. Using AOCS method Cc 11-53, salad oils must remain clear after 5.5 h of immersion in an ice bath at 0 °C (Firestone 2004) and peanut oils typically do not meet these criteria (Pattee 2005). To better understand this phenomenon, especially with the release of new high-oleic cultivars, variation in crystallization behavior among minimally refined oils from nine recent peanut cultivars was determined (Davis and Sanders 2007). Small-strain oscillatory rheological analyses were applied to monitor liquid to solidlike transitions on cooling to refrigeration temperatures. High-oleic varieties were the last to crystallize (solidify) on equivalent cooling treatment and this was attributed to the structure of oleic acid, which limits ‘packing’ during crystallization. Good agreement was observed between rheological analyses and differential scanning calorimetry (DSC) measurements of crystallization, and both measurements negatively correlated with increased concentrations of saturated fatty acids among cultivars. No peanut cultivar passed the modified cold test for salad oils; however, oil from one high-oleic variety retained a liquid-like consistency for 12+ hr at 3 °C. As a whole, these data suggest that a high-oleic peanut oil, bred or processed to be also very low in saturated fatty acids, should be capable of passing this salad oil test and generally have improved cold-flow properties (Davis and Sanders 2007). Current high-oleic varieties have superior cold-flow properties to traditional varieties.

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8.4.5

Free fatty acid (FFA)

Peanut oils generally have low levels of FFA. The highest content is found in very immature seed (0.8%) and the percentage decreases to ca. 0.05% in fully mature seed. Improper handling, moisture, fungal invasion, and other factors contribute to hydrolysis of triacylglycerols and cause significant increases in FFA (Sanders 1979). Neutralization in the refining process removes FFA, but crude oil used in many parts of the world may contain high FFA, with a resulting rapid deterioration in quality, flavor, and stability (Sanders et al. 1982).

8.4.6

Iodine value (IV)

The iodine value is a measure of the degree of unsaturation in oils, as determined by the uptake of appropriate halogen compounds. Because melting point and oxidative stability are related to the degree of unsaturation, IV provides an estimation of these quality factors. The greater the iodine value, the more the unsaturation and the higher the susceptibility to oxidation. Peanut oil (IV 82–107) is more saturated than corn (IV 103–128), cottonseed (IV 99–113), or linseed (IV 155–205) oils; however, it is considerably less saturated than coconut (IV 7.7–10.5), palm (IV 44–54), or butter (IV 25–42) oils (Pattee 2005).

8.4.7

Peroxide value

Elevated peroxide values indicate that lipid oxidation has taken place. It is measured as reactive oxygen in terms of milliequivalents per 1000 g fat. In raw peanuts, once the cell structure is disrupted by pressing or other means, lipoxygenase promotes oxidation of linoleic acid to form hydroperoxides. These oxidation products are correlated with reduced flavor scores and cardboard or painty flavor defects (Warner 1985). Peroxide value is often used as an indicator of peanut quality related to oil oxidation.

8.4.8

Acetyl value

The acetyl value is the number of milligrams of KOH (potassium hydroxide) required to neutralize the acetic acid produced by the hydrolysis of 1 g of acetylated fat and is a measure of free hydroxyl groups present in the oil. The acetyl number of peanut oil (8.5–9.5) is lower than other vegetable oils, but higher than coconut oil, palm oil, and the animal fats and oils (Cobb and Johnson 1973).

8.4.9

Heat of fusion

The heat of fusion, or latent heat, is the quantity of heat required to change 1 g of solid to a liquid with no temperature change. This latent heat increases with increasing molecular weight. The heat of fusion of peanut oil is 21.7 cal/g (Cobb and Johnson 1973).

8.4.10 Unsaponifiable material The unsaponifiable matter in peanut oil is mainly sterols, with β-sitosterol constituting the largest amount. Other compounds found in this fraction are tocopherols and triterpenic dialcohols (Zarrok et al. 2009).

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HEALTH ISSUES Cardiovascular disease and diabetes

Early work with animals suggested a high atherogenic potential when peanut oil was fed in relatively high doses. Because chemical treatment to randomize peanut oil resulted in a decrease in atherogenicity, triacylglycerol structure was believed to be involved (Kritchevsky et al. 1973). However, Ahmed and Young (1982) indicated that the Kritchevsky study did not provide adequate proof of this claim, due either to lack of inclusion of other vegetable oils for comparison or lack of adequate data for sound statistical analysis. In the last 20 years, consistent data in numerous studies indicate an amazingly high 30–50% reduction in cardiovascular disease in people who consumed nuts, including peanuts, four to five times each week (Fraser et al. 1992; Hu et al. 1998; Alper and Mattes (2003). Consumption of oils rich in MUFA, such as peanut oil, is associated with improved blood chemistry markers indicative of cardiovascular health, including reduced low-density lipoprotein (LDL) and total triacylglycerol (TAG) and increased high-density lipoprotein (HDL) (Kris-Etherton et al. 1999, 2008). Moderate consumption of oils rich in MUFA, such as peanut oil, improve risk factors for CVD in overweight individuals (Pelkman et al. 2004). In one study, subjects consumed one of five diets: a low-fat diet, one including olive oil, one including peanuts and peanut butter, one including peanut oil, and a typical American diet. Results indicated that the diet including peanuts and peanut butter, the one including peanut oil, and the diet including olive oil (all low in saturated fat and cholesterol and high in monounsaturated fat) lowered total cholesterol and LDL cholesterol. Further, each of these three diets lowered triacylglycerol levels without lowering the beneficial HDL cholesterol (Kris-Etherton et al. 2001). Along with fat-free peanut flour and whole peanuts, peanut oil was found to reduce blood chemistry risk factors for cardiovascular disease and also significantly reduce an aortic marker (cholesterol esters) for the development of atherosclerosis in an animal study (Stevens et al. 2010). Peanut oil and other oils rich in oleic acid have also been shown to be effective at limiting the negative effects of diabetes in model systems (Vassiliou et al. 2009), which supports clinical data showing that peanuts are a good food choice for people suffering from type 2 diabetes and the complications associated with diabetes and cardiovascular disease (Jiang et al. 2002; Li et al. 2009).

8.5.2

Weight control

Peanuts, like other oilseeds, are calorie dense due to the relatively high oil content in these foods; however, regular consumption of peanuts and other oilseeds is associated with stable weight or with decreased weight gain (Fraser et al. 1992; Coelho et al. 2006; Traoret et al. 2008). Potential mechanisms promoting weight maintenance after consumption of energydense oilseeds include spontaneous dietary compensation due to satiety effects from the oilseeds, increased energy expenditure, or decreased absorption of oilseed (Alper and Mattes 2002; Traoret et al. 2008). To better understand what components within peanuts and what mechanisms contributed to weight control in people consuming peanuts, a clinical feeding study was designed in which subjects from three different countries (Ghana, Brazil, and the US) were fed whole peanuts, peanut oil, peanut flour, or peanut butter in a balanced, nonvegetarian diet (Traoret et al. 2008). Data indicated that whole peanuts were more effective than peanut oil, peanut butter, or peanut flour at maintaining weight due to incomplete

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absorption of the whole seed during digestion, as determined by measuring fecal fat contents after consumption of the different diets (Traoret et al. 2008). The effects of peanut oil on energy expenditure, body composition, lipid profile, and appetite was part of a feeding study of lean and overweight individuals from Ghana and the US (Coelho et al. 2006). The peanut oil was included daily at a level representing 30% of the individuals’ resting energy as a component of a milkshake over an eight-week study. Dietary compensation among participants was significantly less among overweight as compared to lean individuals. Overweight individual showed a statistically significant weight gain after eight weeks of the study, but this weight gain was more than 40% less than theoretically predicted. Resting energy expenditure increased by about 5% for overweight individuals, but no significant change was observed for lean individuals. Blood lipid profiles improved across both classes of individuals with consumption of the peanut oil. The authors state that these findings when compared with other studies suggest that components in whole peanut beyond the oil contribute to dietary compensation effects and weight control during peanut consumption. Some work suggests that oils rich in MUFA, including peanut oil, promote satiety more effectively than lipids rich in saturated fatty acids. A feeding study tested this hypothesis in which peanut oil and canola oil, both rich in MUFA, were compared to butter, rich in saturated fatty acids, as an ingredient (40 g) of a muffin (Alfenas and Mattes 2003). All muffins containing lipids resulted in lower hunger ratings when compared to lipid-free controls; however, no differences were observed across lipid sources.

8.5.3

Allergy

In recent years, concern about food allergies in general has increased, and concern about peanut allergy is no exception. For unknown reasons, peanut allergy is associated with a higher incidence of fatal food-induced anaphylaxis than any other food allergy. Immediate hypersensitivity to foods occurs in 6–8% of children and about 1% of adults. In the United States, a recent survey suggested that 0.7% of children are allergic to peanuts in varying degrees. Avoidance is the only current method of dealing with a food allergy. Significant research efforts are underway in dealing with peanut allergy. Several peanut allergens have been identified and all are proteins (Burks et al. 1998). Highly refined peanut oil is generally not considered a threat to individuals susceptible to peanut allergenicity (Taylor et al. 1981; Hourihane et al. 1997; Crevel et al. 2000; Hidalgo and Zamora 2006). For example, 60 individuals predisposed to the peanut allergy consumed refined peanut oil in a double-blind, placebo-controlled feeding challenge and none of the participants reacted negatively to the refined peanut oil (up to 16 ml) (Hourihane et al. 1997). The refining steps are critical in removing enough protein from crude peanut oil to render it essentially allergen free. Crude peanut oil has been reported to cause an allergenic reaction in a small percentage of allergenic individuals (Hourihane et al. 1997; Olszewski et al. 1998; Crevel et al. 2000; Hidalgo and Zamora 2006). There is an approximate hundredfold reduction in protein content between crude (∼200 μg/ml) and refined peanut oil (1–2 μg/ml), but this is dependent on the refining steps utilized (Crevel et al. 2000; Peeters et al. 2004). There is some limited evidence suggesting that highly sensitized individuals can react positively to refined peanut oil (Olszewski et al. 1998); however, in these cases it is not clear if the oil was indeed highly refined (Crevel et al. 2000). A substantial challenge in this field is proper quantification of peanut protein in the oil matrix and various extraction procedures and subsequent detection methods have been

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evaluated (Crevel et al. 2000; Hidalgo and Zamora 2006). Interfering agents, such as phospholipids, in the oil present formidable challenges for protein quantification. Direct amino acid determination from oil extracts may be the most reliable method and suggest higher concentrations in oils than previously determined by colorimetric-based protein assays (Hidalgo et al. 2001; Martin-Hernandez et al. 2008). Refined peanut oil is a prominent ingredient in various topical formulations for skin-care ointments and is an effective carrier agent serving as a moisturizer and increasing the penetration of active agents. Studies have shown that, even for patients with peanut allergy, a refined peanut oil base did not elicit allergic responses (Paller et al. 2003; Ring and Mohrenschlager 2007).

NOTE The use of trade names in this chapter does not imply endorsement by the US Department of Agriculture of the products named, nor criticism of similar ones not mentioned.

REFERENCES Ahmed, E.M. and Young, C.T. (1982) Composition, quality, and flavor of peanuts, in Peanut Science and Technology (eds H.E. Pattee and C.T. Young), American Peanut Research and Education Society, Yoakum, TX, pp. 655–688. Alfenas, R.C.G. and Mattes, R.D. (2003) Effect of fat sources on satiety, Obesity Research, 11, 183–187. Alper, C.M. and Mattes, R.D. (2002) Effects of chronic peanut consumption on energy balance and hedonics, International Journal of Obesity, 26, 1129–1137. Alper, C.M. and Mattes, R.D. (2003) Peanut consumption improves indices of cardiovascular disease risk in healthy adults, Journal of the American College of Nutrition, 22, 133–141. Awad, A.B., Chan, K.C., Downie, A.C. and Fink, C.S. (2000) Peanuts as a source of β-sitosterol, a sterol with anticancer properties, Nutrition and Cancer, 36(2), 238–241. Bolton, G.E. and Sanders, T.H. (2002) Effect of roasting oil composition on the stability of roasted higholeic peanuts, Journal of the American Oil Chemists’ Society, 79, 129–132. Brooks, G.E. (1975) Peanuts and colonialism; Consequences of the commercialization of peanuts in West Africa, 1830–1870, Journal of African History, XVI, 29–54. Burks, W., Sampson, H.A. and Bannon, G.A. (1998) Peanut allergens, Allergy, 53, 725–730. Chiou, R.Y-Y., Cheng, S-L., Tseng, C-Y. and Liu, T.C. (1993) Flavor fortification and characterization of raw peanut oils subjected to roasting with partially defatted peanut meal under various atmospheric conditions, Journal of Agricultural Food Chemistry, 41, 1110–1113. Chu, Y., Holbrook, C.C. and Ozias-Akins, P. (2009) Two alleles of ahfad2b control the high oleic acid trait in cultivated peanut, Crop Science, 49, 2029–2036. Chu, Y., Ramos, L., Holbrook, C.C. and Ozias-Akins, P. (2007) Frequency of a loss-of-function mutation in oleoyl-pc desaturase (ahfad2a) in the mini-core of the US peanut germplasm collection, Crop Science, 47, 2372–2378. Chun, J., Lee, J. and Eitenmiller, R.R. (2005) Vitamin E and oxidative stability during storage of raw and dry roasted peanuts packaged under air and vacuum, Journal of Food Science, 70, C292–C297. Cobb, W.Y. and Johnson, B.R. (1973) Physicochemical properties of peanuts, in Peanuts – Cultures and Uses (ed. C.T. Wilson), American Peanut Research and Education Association, Stillwater, OK, pp. 209–263. Coelho, S.B., de Sales, R.L., Iyer, S.S. et al. (2006) Effects of peanut oil load on energy expenditure, body composition, lipid profile, and appetite in lean and overweight adults, Nutrition, 22, 585–592. Cooney, R.V., Franke, A.A., Harwood, P.J. et al. (1993) γ-Tocopherol detoxification of nitrogen dioxide: Superiority to α-tocopherol, Proceedings of the National Academy of Sciences, 90, 1771–1775. Crevel, R.W.R., Kerkhoff, M.A.T. and Koning, M.M.G. (2000) Allergenicity of refined vegetable oils, Food and Chemistry Toxicology, 38, 385–393.

Gunstone_c08.indd 239

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240

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Davis, J.P. and Sanders, T.H. (2007) Liquid to semisolid rheological transitions of normal and high-oleic peanut oils upon cooling to refrigeration temperatures, Journal of the American Oil Chemists’ Society, 84, 979–987. Davis, J.P., Dean, L.O., Faircloth, W.H. and Sanders, T.H. (2008) Physical and chemical characterizations of normal and high-oleic oils from nine commercial cultivars of peanut, Journal of the American Oil Chemists’ Society, 85, 235–243. Davis, J.P., Dean, L.L., Price, K.M. and Sanders, T.H. (2010) Roast effects on the hydrophilic and lipophilic antioxidant capacities of peanut flours, blanched peanut seed and peanut skins, Food Chemistry, 119, 539–547. De la Roche, I.A.,Weber, E.J. and Alexander, D.E. (1971) Effects of fatty acid concentration and positional specificity on maize triglyceride structure, Lipids, 6, 531–536. Dean, L.L. and Sanders, T.H. (2009) Hexacosanoic acid and other very long-chain fatty acids in peanut seed oil, Plant Genetic Research, 7, 252–256. Firestone, D. (ed.) (2004) Official Methods and Recommended Practices of the AOCS, 5th edn, American Oil Chemists Society, Champaign, IL. Fore, S.P., Morrie, N.J., Mack, C.H., Freeman, A.F. and Bickford, W.G. (1953) Factors affecting the stability of crude oils of 16 varieties of peanuts, Journal of the American Oil Chemists’ Society, 30, 298–301. Fraser, G.E., Sabate, J., Beeson, W.L. and Strahan, T.M. (1992) A possible protective effect of nut consumption on risk of coronary heart-disease – the adventist health study, Archives of Internal Medicine, 152, 1416–1424. Hammons, R.O. (1973) Early history and origin of the peanut, in Peanuts – Culture and Uses (ed. C.T. Wilson), American Peanut Research and Education Assocation, Stillwater, OK, pp. 17–45. Hidalgo, F.J. and Zamora, R. (2006) Peptides and proteins in edible oils: Stability, allergenicity, and new processing trends, Trends in Food Science Technology, 17, 56–63. Hidalgo, F.J., Alaiz, M. and Zamora, R. (2001) Determination of peptides and proteins in fats and oils, Analytical Chemistry, 73, 698–702. Hokes, J.C. (1977) Factors affecting the oxidative stability of oils from various peanut cultivars, MS thesis, University of Georgia, Athens, GA. Holaday, C.E. and Pearson, J.L. (1974) Effects of genotype and production area on the fatty acid composition, total oil and total proteins in peanuts, Journal of Food Science, 39, 1206–1209. Hourihane, J.O., Bedwani, S.J., Dean, T.P. and Warner, J.O. (1997) Randomised, double blind, crossover challenge study of allergenicity of peanut oils in subjects allergic to peanuts, British Medical Journal, 314, 1084–1088. Hu, F.B., Stampfer, M.J., Manson, J.E. et al. (1998) Frequent nut consumption and risk of coronary heart disease in women: Prospective cohort study, British Medical Journal, 317, 1341–1345. Isleib, T.G., Wilson, R.F. and Novitzky, W.P. (2006) Partial dominance, pleiotropism, and epistasis in the inheritance of the high-oleate trait in peanut, Crop Science, 46, 1331–1335. Jakab, A., Héberger, K. and Forgács, E. (2002) Comparative analysis of different plant oils by highperformance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry, Journal of Chromatography, A 976, 255–263. Jiang, R., Manson, J.E., Stampfer, M.J. et al. (2002) Nut and peanut butter consumption and risk of type 2 diabetes in women, Journal of the American Medical Association, 288, 2554–2560. Jones, P.J.H. and Abumweis, S.S. (2009) Phytosterols as functional food ingredients: Linkages to cardiovascular disease and cancer, Current Opinion in Clinical Nutrition and Metabolic Care, 12, 147–151. Jonnala, R.S., Dunford, N.T. and Chenault, K. (2006a) Tocopherol, phytosterol and phospholipid compositions of genetically modified peanut varieties, Journal of the Science of Food Agriculture, 86, 473–476. Jonnala, R.S., Dunford, N.T. and Dashiell, K.E. (2006b) Tocopherol, phytosterol and phospholipids compositions of new high oleic peanut cultivars, Journal of Food Composition and Analysis, 19, 601–605. Kris-Etherton, P.N., Hu, F.B., Ros, E. and Sabate, J. (2008) The role of tree nuts and peanuts in the prevention of coronary heart disease: Multiple potential mechanisms, Journal of Nutrition, 138, 1746S–1751S. Kris-Etherton, P.M., Pearson, T.A., Wan, Y. et al. (1999) High-monounsaturated fatty acid diets lower both plasma cholesterol and triacylglycerol concentrations, American Journal of Clinical Nutrition, 70, 1009– 1015. Kris-Etherton, P.M., Zhao, G., Binkoski, A.E., Coval, S.M. and Etherton, T.D. (2001) The effects of nuts on coronary heart disease risk, Nutrition Reviews, 59, 103–111. Kritchevsky, D., Tepper, S.A., Vesselinovitch, D. and Wissler, R.W. (1973) Cholesterol vehicle in experimental atherosclerosis. 13. Randomized peanut oil, Atherosclerosis, 17, 225–243.

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Li, T.Y., Brennan, A.M., Wedick, N.M. et al. (2009) Regular consumption of nuts is associated with a lower risk of cardiovascular disease in women with type 2 diabetes, Journal of Nutrition, 139, 1333–1338. Lin, H.Z., Liu, Y.J., He, J.G., Zheng, W.H. and Tian, L.X. (2007) Alternative vegetable lipids sources in diets for grouper, Epinephelus coioides (Hamilton): Effects on growth, and muscle and liver fatty acid composition, Aquaculture Research, 38, 1605–1611. Martin-Hernandez, C., Benet, S. and Obert, L. (2008) Determination of proteins in refined and nonrefined oils, Journal of Agricultural Food Chemistry, 56, 4348–4351. Narciso, L., Pausão-Ferreira, P., Passos, A. and Luis, O. (1999) HUFA content and DHA/EPA improvements of Artemia sp. with commercial oils during different enrichment periods, Aquaculture Research, 30, 21–24. Norden, A.J., Gorbet, D.W., Knauft, D.A. and Young, C.T. (1987) Variability in oil quality among peanut genotypes in the Florida breeding program, Peanut Science, 14, 7–11. O’Keefe, S.F., Wiley, V.A. and Knauft, D.A. (1993) Comparison of oxidative stability of high- and normaloleic peanut oils, Journal of the American Oil Chemists’ Society, 70, 489–492. Olszewski, A., Pons, L., Moutete, F. et al. (1998) Isolation and characterization of proteic allergens in refined peanut oil, Clinical and Experimental Allergy, 28, 850–859. Paller, A.S., Nimmagadda, S., Schachner, L. et al. (2003) Fluocinolone acetonide 0.01% in peanut oil: Therapy for childhood atopic dermatitis, even in patients who are peanut sensitive, Journal of the American Academy of Dermatology, 48, 569–577. Pan, Y.M., Zhang, X.P., Wang, H.S. et al. (2007a) Antioxidant potential of ethanolic extract of Polygonum cuspidatum and application in peanut oil, Food Chemistry, 105, 1518–1524. Pan, Y.M., Zhu, J.C., Wang, H.S. et al. (2007b) Antioxidant activity of ethanolic extract of Cortex fraxini and use in peanut oil, Food Chemistry, 103, 913–918. Parker, W.A. and Melnick, D. (1966) Absence of aflatoxin from refined vegetable oils, Journal of the American Oil Chemists’ Society, 43, 635–638. Pattee, H.E. (2005) Peanut oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2, Edible Oil and Fat Products: Oils and Oil Seeds (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., New York, pp. 431–463. Pattee, H.E. and Purcell, A.E. (1967) Carotenoid pigments of peanut oil, Journal of the American Oil Chemists’ Society, 44, 328–330. Peeters, K., Kunlst, A.C., Rynja, F.L., Bruijnzeel-Koomen, C. and Koppelman, S.J. (2004) Peanut allergy: Sensitization by peanut oil-containing local therapeutics seems unlikely, Journal of Allergy and Clinical Immunology, 113, 1000–1001. Pelkman, C.L., Fishell, V.K., Maddox, D.H. et al. (2004) Effects of moderate-fat (from monounsaturated fat) and low-fat weight-loss diets on the serum lipid profile in overweight and obese men and women, American Journal of Clinical Nutrition, 79, 204–212. Pettitt, B.C., Schwartz, R.C. and Hecking, L.T. (1992) Country of origin – peanuts. China vs Argentina, Customs Laboratory Bulletin, 4(3), 89–102. Ring, J. and Mohrenschlager, M. (2007) Allergy to peanut oil – clinically relevant? Journal of the European Academy of Dermatology and Venereology, 21, 452–455. Ryan, L.C., Mestrallet, M.G., Nepote, V., Conci, S. and Grosso, N.R. (2008) Composition, stability and acceptability of different vegetable oils used for frying peanuts, International Journal of Food Science Technology, 43, 193–199. Salunke, D.K. and Desai, B.B. (1986) Postharvest Biotechnology of Oilseeds, CRC Press, Boca Raton, FL. Sanders, T.H. (1979) Varietal differences in peanut triacylglycerol structure, Lipids, 14, 630–633. Sanders, T.H. (1980a) Effects of variety and maturity on lipid class composition of peanut oil, Journal of the American Oil Chemists’ Society, 57, 8–11. Sanders, T.H. (1980b) Fatty acid composition of lipid classes in oils from peanuts differing in variety and maturity, Journal of the American Oil Chemists’ Society, 57, 12–15. Sanders, T.H. (1982) Peanut triacylglycerols: Effect of season and production location, Journal of the American Oil Chemists’ Society, 59, 346–351. Sanders, T.H. (1996) High Oleic Acid Peanuts: Potentials in Health, Products, and Oil Use, No. 82-1, Institute of Food Technologists, Chicago, IL. Sanders, T.H. (2001) Non-detectable levels of trans-fatty acids in peanut butter, Journal of Agricultural Food Chemistry, 49, 2349–2351. Sanders, T.H., Schubert, A.M. and Pattee, H.E. (1982) Postharvest physiology and methodologies for estimating maturity, in Peanut Science and Technology (ed. H.E. Pattee and C.T. Young), American Peanut Research and Education Society, Yoakum, TX, pp. 624–654.

Gunstone_c08.indd 241

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Sanders, T.H., Vercellotti, J.R., Crippen, K.L. et al. (1992) Quality factors in exported peanuts from Argentina, China, and the U.S., Journal of the American Oil Chemists’ Society, 69, 1032–1035. Sempore, G., and Bezard, J. (1986) Qualitative and quantitative analysis of peanut oil triacylglycerols by reversed-phase liquid chromatography, Journal of Chromatography, 366, 261–282. Shin, E.C., Craft, B.D., Pegg, R.B., Phillips, R.D. and Eitenmiller, R.R. (2010) Chemometric approach to fatty acid profiles in runner-type peanut cultivars by principal component analysis (PCA), Food Chemistry, 119, 1262–1270. Shin, E.C., Huang, Y.Z., Pegg, R.B., Phillips, R.D. and Eitenmiller, R.R. (2009) Commercial runner peanut cultivars in the United States: Tocopherol composition, Journal of Agricultural Food Chemistry, 57, 10289–10295. Singleton, J.A. and Pattee, H.E. (1987) Characterization of peanut oil triacylglycerols by high performance liquid chromatography, gas liquid chromatography, and electron impact mass spectrometry, Journal of the American Oil Chemists’ Society, 64, 534–538. Singleton, J.A. and Stikeleather, L.F. (1995) High-performance liquid chromatography analysis of peanut phospholipids. II. Effect of postharvest stress on phospholipid composition, Journal of the American Oil Chemists’ Society, 72, 485–488. Soyatech (2009) Soya and Oilseed Bluebook, Soyatech, Bar Harbor, ME. Stevens, A.M., Dean, L.L., Davis, J.P., Osborne, J.A. and Sanders, T.H. (2010) Peanuts, peanut oil and fat free peanut flour reduced cardiovascular disease risk factors and the development of atherosclerosis in Syrian golden hamsters, Journal of Food Science, 75, in press. Taylor, S.L., Busse, W.W., Sachs, M.I., Parker, J.L. and Yunginger, J.W. (1981) Peanut oil is not allergenic to peanut-sensitive individuals, Journal of Allergy and Clinical Immunology, 68, 372–375. Traoret, C.J., Lokko, P., Cruz, A. et al. (2008) Peanut digestion and energy balance, International Journal of Obesity, 32, 322–328. U.S. Department of Agriculture, Foreign Agricultural Service, Production Estimates and Crop Assessment Division (2001) World Agricultural Production, October, http://www.fas.usda.gov. Vassiliou, E.K., Gonzalez, A., Garcia, C. et al. (2009) Oleic acid and peanut oil high in oleic acid reverse the inhibitory effect of insulin production of the inflammatory cytokine tnf-alpha both in vitro and in vivo systems, Lipids in Health and Disease, 8, 25, http://www.lipidworld.com/content/8/1/25, accessed October 2010. Warner, K. (1985) Sensory evaluation of flavor quality in oils, in Flavor Chemistry of Fats and Oils (eds Minn, D.B., Smouse, T.H.), AOCS Press, Champaign, IL, pp. 207–222. Watson, W. (1769) Some account of an oil, transmitted by Mr. George Brownrigg, of North Carolina, Philosophical Transactions of the Royal Society, 59, 379–383. Woodroof, J.G. (1983) Peanut oil, in Peanuts – Production, Processing, Products (ed. J.G. Woodroof), AVI Publishing, Westport, CT, pp. 293–307. Worthington, R.E., Hammons, R.O. and Allison, J.R. (1972) Varietal differences and seasonal effects on fatty acid composition and stability of oil from 82 peanut genotypes, Journal of Agricultural Food Chemistry, 20, 727–730. Yin, D.M., Deng, S.Z., Zhan, K.H. and Cui, D.Q. (2007) High-oleic peanut oils produced by hprna-mediated gene silencing of oleate desaturase, Plant Molecular Biology Reporter, 25, 154–163. Yu, S.L., Pan, L.J., Yang, Q.L. et al. (2008) Comparison of the delta(12) fatty acid desaturase gene between high-oleic and normal-oleic peanut genotypes, Journal of Genetics and Genomics, 35, 679–685. Zarrok, W., Carrasco-Pancorbo, A., Zarrok, M., Segura-Carretero, A. and Fernández- Guitiérrez, A. (2009) Multi-components analysis of sterols, tocopherols and triterpenic dialcohols of the unsaponifiable of fraction of vegetable oils by liquid chromatography-atmospheric pressure chemical ionization-ion trap mass spectrometry, Talanta, 80, 924–934. Zhou, Q.C., Li, C.C., Liu, C.W., Chi, S.Y. and Yang, Q. (2007) Effects of dietary lipid sources on growth and fatty acid composition of juvenile shrimp, Litopenaeus vannamei, Aquaculture Nutrition, 13, 222–229.

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9

Olive Oil

Dimitrios Boskou

9.1

INTRODUCTION

Olive oil is a major component of the diet in countries surrounding the Mediterranean sea. For those living in these countries, olive oil is the main source of fat in their cuisine. In the past few years the oil has also become more popular among consumers of northern Europe, the USA, Canada and other countries, although these new consumers are not always familiar with the properties and characteristics of this natural product. The growing enthusiasm for the Mediterranean diet and for olive oil is mainly due to studies indicating that this diet plays a positive role in the prevention of certain diseases, in particular coronary heart disease. Chemical and analytical work to elucidate the structure and to quantify the minor constituents of olive oil is now progressing rapidly. Much work has also been carried out by nutritionists to obtain more information about its key functional components. What differentiates olive oil chemically from other culinary fats is described in this chapter. The discussion does not cover olive oil chemistry and technology in full. Rather, it aims mainly at highlighting issues related to production, compositional characteristics and the properties that make this oil so distinct.

9.2

EXTRACTION OF OLIVE OIL FROM OLIVES

Virgin olive oil is obtained from the fruits of the olive tree (Olea europaea) by mechanical or other physical means under conditions that do not cause any changes in the oil. The oil is first released from the olives by crushing. In pressure systems, stone mills are generally used; in continuous centrifugation plants these are replaced by metal crushers (hammer, roller, disc). After it has been crushed the olive paste is mixed. This process is called malaxation and consists of stirring the olive mass slowly and continuously for about 30 minutes. The main constituents of the paste after malaxation are olive oil, small pieces of kernel (pith), water and cellular debris. Separation is achieved by pressure, centrifugation or selective filtration processes. Important factors in the production of good-quality olive oil are the harvesting period, the maturity of the fruit, the mode of harvesting (hand picking, nets, other means), storage of the olives before processing, leaf removal, mode of crushing and kneading, and the system of extraction. The essentials of the four methods of extraction that are in use today are briefly Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Vegetable Oils in Food Technology Crushing (generally by millstone crushers) Malaxation-mixing Paste application on mats Pressing

Oily must

Pomace

Centrifugation

Oil

Waste water

Figure 9.1 Flow chart for olive extraction by pressing.

described below. For a complete coverage of the subject the reader should consult the extended reviews by Di Giovacchino (1996), Fedeli (1996) and Petrakis (2006).

9.2.1

Pressure

Pressure is the oldest method of extraction, and is still in use although not widespread. It was largely replaced in the 1970s and 1980s by centrifugation methods, which help to cut processing costs and reduce olive storage time. In the pressure system (see Figure 9.1) the paste is pressed to release an oily ‘must’ (oil and water from the olives). The liquid separates from the solid phase through drainage. A cake (pomace) is formed between the mats and this is dried and used for the production of olive residue oil. Oil and water are further separated by centrifugation. Pressure systems yield good-quality oil when the fruits themselves are in good condition and the filtering diaphragms are properly cleaned. Otherwise, oils are produced with a high level of undesirable components, such as n-octane, 2-methyl-propanol, 3-methylbutanol and acetic acid.

9.2.2

Centrifugation (three-phase system)

In centrifugation, the crushed olives are mixed with water. A horizontal centrifuge separates the mass into ‘pomace’ and ‘must’ and the latter is further separated into oil and water (Figure 9.2).

9.2.3

Two-phase decanters

In the two-phase decanters water is not added. The crushed olives are directly separated into oil and a mixture of water and husks. This system reduces significantly the amount of waste water and so protects the environment. The oil so produced is more stable because the level of natural antioxidants is higher. However, the pomace has a high moisture content (57–58%) and this makes its transportation more costly.

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Crushing (generally by metallic crushers) Malaxation Centrifugation

Pomace

Oily must Centrifugation

Oil

Waste water

Figure 9.2 Flow sheet for olive extraction in a three-phase centrifugal system.

9.2.4

Percolation (selective filtration)

In percolation, a steel plate is plunged into olive paste. When it is withdrawn it will be coated with oil because of the different surface tension between oil and water (the metal phase is coated with a skin of oil). The system is combined with a continuous horizontal centrifuge to increase capacity.

9.2.5

Processing aids

The oil yield and the quality of the oil can be improved by enzymes with pectinolytic and cellulosolytic activity (Di Giovacchino 1996; Petrakis 2006). Micronised mineral talc is used in Spain for hard pastes to increase oil yields. Talc reduces oil/water emulsions and increases the recovery of free oil. However, the use of coadjuvants is not in accordance with the legal definition of virgin olive oil, which requires the oil to be obtained from the fruits solely by mechanical or other physical means.

9.2.6

Extraction of pomace oil (olive residue oil)

Mechanical processsing of olive paste leaves two residual products, husks (pomace) and water. Residual oil in the pomace varies depending on the mode of extraction. It is usually 6–8% in pressure systems and 3–5% in the three-phase extraction systems. The recovery of the oil from the husks is achieved with hexane in extraction plants located elsewhere. The transportation of the by-product presents a cost problem because of its high moisture content (25–58%). The raw oil extracted from the husks is dark green, with high acidity and a poor flavour. It has to be neutralised, bleached, and deodorised before it is edible. With solvent extraction, olive-residue oil contains some minor constituents at higher levels than those found in olive oils (waxes, sterols, erythrodiol and uvaol). This is the reason for designating pomace oil as a distinct product.

9.3

OLIVE OIL COMPOSITION

Olive oil is primarily a mixture of triacylglycerols with some free fatty acids, mono- and di-acylglycerols and non-glyceridic constituents (0.5–1.5%). The content of free fatty acid

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Table 9.1 Fatty acid composition of olive oil (% by gas liquid chromatography). Lauric Myristic Palmitic Palmitoleic Heptadecanoic Heptadecenoic Stearic Oleic Linoleic Linolenic Arachidic Eicosenoic Behenic Lignoceric

12 14 16 16 17 17 18 18 18 18 20 20 22 24

: : : : : : : : : : : : : :

0 0 0 1 0 1 0 1 2 3 0 1 0 0

Not detected 0.0–0.1 7.5–20.0 0.3–3.5 0.0–0.5 0.0–0.6 0.5–5.0 55.0–83.0 3.5–21.0 0.0–1.0 0.0–0.8 Not specified 0.0–0.3 0.0–1.0

Source: Codex Alimentarius (2003).

varies with the type of olive oil (extra virgin, fine virgin, ordinary, mixture of refined with virgin) and is an important quality criterion in fixing the grade.

9.3.1

Fatty acids and triacylglycerols

The fatty acid composition of olive oil ranges from 7.5–20% palmitic acid, 0.5–5% stearic acid, 0.3–3.5% palmitoleic acid, 55–85% oleic acid, 7.5–20% linoleic acid and 0.0–1.5% linolenic acid. Myristic, heptadecanoic and eicosanoic acids are found only in trace amounts (Table 9.1). Scano and co-workers (1999), using 13C nuclear magnetic resonance spectroscopy, detected and quantified cis-vaccenic (11–18:1) and eicosenoic acids. Fatty acid composition may differ from sample to sample, depending on the place of production, the latitude, the climate, the variety and the stage of maturity of the fruit. Greek, Italian and Spanish olive oils are low in linoleic and palmitic acids and have a high percentage of oleic acid. Tunisian olive oils are higher in linoleic and palmitic acids and lower in oleic acid. Triacylglycerols found in significant proportions in olive oil are OOO (40–59%), POO (12–20%), OOL (12.5–20%), POL (5.5–7%) and SOO (3–7%). Smaller amounts of POP, POS, OLnL, LOL, OLnO, PLL, PLnO and LLL are also encountered (Regulation 282/98, Official Journal of European Communities, L 28.5/4-2-1998). These three-letter symbols represent all the isomeric triacylglycerols containing the three acyl groups indicated, where P = palmitic, O = oleic, S = stearic, L = linoleic and Ln = linolenic acid. According to Santinelli and co-workers (1992), the 1-random, 2-random, 3-random distribution theory is not always applicable to olive oil. Like other vegetable oils, olive oil has a high concentration of oleic acid and a low concentration of palmitic and stearic acids in position 2 of the triacylglycerol molecules. Vlahof (2006) used linear models from a large data set acquired for Italian olive oil samples and quantitative nuclear magnetic resonance spectroscopy. The models used proved that the 1,3- and 2-distribution of saturated, oleate and linoleate chains in olive oil triacylglycerols deviate from the random distribution pattern to an extent that depends on the concentration of the fatty acid in the whole triacylglycerol.

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247

Mono- and di-acylglycerols

The presence of partial glycerides in olive oil is due either to incomplete triacylglycerol biosynthesis or to hydrolytic reactions. In virgin olive oil, the concentration of diacylglycerols ranges from 1–2.8%, with monoacylglycerols present at much lower levels (less than 0.25%). Storage conditions affect the distribution of fatty acids. 1,2-Diacylglycerols present in fresh oil tend to isomerise to the more stable 1,3-diacylglycerols. The extent of this rearrangement gives information about the age and storage conditions of the oil. Gertz and Fiebig (2006) proposed a method for the determination of isomeric diacylglycerols that was adopted and included in the German Standard Methods for checking virgin olive oil quality.

9.3.3

Other constituents

The various classes of minor constituents can be divided into two groups. The first group consists of fatty acid derivatives such as mono- and di-acylglycerols, phospholipids, waxes and sterol esters. The second group includes classes of compounds not related chemically to fatty acids: hydrocarbons, aliphatic alcohols, free sterols, tocopherols, chlorophylls, carotenoids and polar compounds such as tyrosol and hydroxytyrosol. Some minor constituents are present only in the crude oil. Refining removes phospholipids and phenols, and causes significant quantitative and qualitative changes in the other classes. Most of the minor constituents of olive oil are present in the unsaponifiable matter. 9.3.3.1

Tocopherols

Tocopherols are important fat-soluble vitamins. They contribute to the oxidative stability of an oil and have an important role in removing free radicals in vivo. Blekas et al. (1995) and Blekas and Boskou (1998) examined the role of α-tocopherol and its contribution to olive oil triacylglycerol stability. They found that α-tocopherol acts as an antioxidant at all levels, but the antioxidant effect is greater at low (100 mg/kg) than at higher concentrations (500 and 1000 mg/kg). In the presence of more effective antioxidants such as o-diphenols, α-tocopherol did not show any significant antioxidant activity during the period of low peroxide accumulation, but acted well when the primary oxidation products reached a critical level. The tocopherol content is highly variable. Concentrations may range from 5–300 mg/kg. Usual values for good-quality oils lie between 100 and 300 mg/kg. Studies for the levels of tocopherols gave values ranging from 98–370 mg/kg in Greek oils (Psomiadou et al. 2000) and 36–314 mg/kg in Italian oils (Lo Curto et al. 2001). The main component of the tocopherol mixture is α-tocopherol, which makes up 95% of the total. The other 5% is β- and γ-tocopherols. All tocopherols occur in the free (non-esterified) form. The vitamin E(mg):PUFA(g) ratio in olive oil is approximately 1:8. In countries with a high annual per capita consumption of olive oil a significant percentage of the daily requirement for vitamin E is covered by this oil. Refined, bleached and deodorised olive oils have a markedly reduced content of tocopherols because of losses during processing. 9.3.3.2

Hydrocarbons

Two hydrocarbons are present in olive oil in considerable amounts, squalene and β-carotene (discussed in the next section).

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Squalene is a highly unsaturated aliphatic hydrocarbon (C30H50) with important biological properties. It is a metabolic precursor of cholesterol. A rich source of squalene is shark liver oil. Squalene is also present in human tissue in small amounts and in some vegetable oils. The presence of squalene in olive oil probably makes a significant contribution to the health effects of the latter (Gapor Md Top and Rahman, 2000). A chemopreventive effect of squalene on some forms of cancer has been reported by Rao et al. (1998) and also by Smith et al. (1998). The abstract of a patent was published in 1999 for the production of a functional food from olive oil and grain germ. The patent reports a process for mechanical extraction of oil from a mixture of extra virgin olive oil and grain germ (presumably wheat germ or maize germ). According to Eyres (1999) the inventor aims at making a functional food with optimal nutritional properties by combining the beneficial effects of the minor constituents present in these oils, such as squalene from olive oil and tocopherols from the germ oil. Squalene has been shown to possess moderate antioxidant properties (Manzi et al. 1998), but loss during storage of the oil in the dark is greater than that of β-tocopherol. According to Psomiadou and Tsimidou (1999), squalene plays a limited role in olive oil stability and its weak antioxidant activity may be explained by the competitive oxidation of the different lipids present. Squalene, found in virgin olive oil at concentrations ranging from 0.7–12 g/kg, accounts for more than 50% in the unsaponifiable fraction of the oil. The squalene content is dramatically reduced during refining (Lanzon et al. 1994). Other hydrocarbons reported to be present in olive oil are C14–C30 n-alkanes, some n-alkenes and terpene hydrocarbons, mainly α-farnesene. The level of these hydrocarbons is approximately 150–200 mg/kg (Lanzon et al. 1994). There is also a limited presence of aromatic polycyclic hydrocarbons such as naphthalene and phenanthrene, but it is not clear to what extent these are natural constituents or contaminants (Tiscornia et al. 1982; Moret et al. 1997). 9.3.3.3 Pigments The colour of virgin olive oil is the result of green and yellow hues due to the presence of chlorophylls and carotenoids. Carotenoids The main carotenoids present in olive oil are β-carotene and lutein (see Figure 9.3 for the structures of these and other components). Xanthophylls such as violaxanthin, neoxanthin and others have also been reported to occur in very small quantities. Total carotenoids may range between 1 and 20 mg/kg, but usually values do not exceed 10 mg/kg. Psomiadou and Tsimidou (2001) reported a lutein content between 0.2 and 3.4 mg/ kg and a β-carotene content between 0.4 and 5.1 mg/kg in a series of samples from various regions in Greece. Carotenoids are singlet oxygen quenchers and protect the oil from photo-oxidation. Their role in the oxidative stability of olive oil has not yet been fully eludicated. There is probably a relation between carotenoids and the mode of action of polar phenols and α-tocopherol (Psomiadou and Tsimidou 1998). Chlorophylls Chlorophyll pigments are responsible for the greenish hues in virgin olive oil. Their content may range from 10 to 30 mg/kg. The main chlorophyll present in packed oil is pheophytin α. Chlorophyll α occurs in the oil just after production. Minguez-Mosquera et al. (1990) reported the presence of chlorophyll α, chlorophyll β, pheophytin α and pheophytin β in fresh oils.

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b-carotene

OH

HO

Lutein

HO

HO D5-avenasterol

b-sitosterol

HO

HO

Cycloeucalenol

Obtusifoliol

HO

HO

Gramisterol

Citrostadienol

Figure 9.3 Structures of various components of olive oil.

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OH

H H

HO

b-amyrin

Butyrospermol

H HO

HO

Cycloartenol

24-Methylene-cycloartanol

Me

Me

Me

Me

CH2OH Me

CH2OH

Me

Me Me Me

HO Me

Me

HO Me

Me

Me

Erythrodiol

Uvaol

Me

Me

Me

Me

Me

COOH

Me

HO

Me

COOH

Me

Me HO

Me Me

Me

Me

Me Oleanolic acid

Me

Maslinic acid

Me

Me Me

Me

COOH

Me

Ursolic acid

COOH

Me

Me HO Me

Me

HO Me

Me

Betulinic acid

Figure 9.3 Continued

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Phenolic acids COOH

CH2COOH

OCH3

CH3O OH

Syringic acid

OH 4-Hydroxyphenylacetic acid

CH2COO

CH CHCOOH OH

OCH3 OH

Homovanillic acid

o-Coumaric acid

COOH

COOH

OH OH 4-Hydroxybenzoic acid

COOH

OH OH Gallic acid

HO

CH CH COOH

OH

p -Coumaric acid

OH

Protocatechuic acid

COOH

OCH3 OH Vanillic acid

CH CH COOH

OH OH Caffeic acid

Figure 9.3 Continued

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Vegetable Oils in Food Technology CH CH COOH

OCH3 OH

CH CHCOOH

CH3O

Ferulic acid

OCH3 OH

Sinapic acid

Tyrosol, hydroxytyrosol and derivatives CH2CH2OH

CH2CH2OH

OH

OH

OH

Hydroxytyrosol

Tyrosol

OH O

OH O CH2 CO CH2 CH2

O H3C O C

OH

CH CH3 O

OH

O G

Oleuropein aglycone

Oleuropein

HO HO

CH2 CO CH2 CH2

H 3C O C

CH CH3 O

O

OH

HO O

O

HO

COOMe O

O

O

O

OHC

O

Me

Decarboxymethyl form of oleuropein aglycone

Dialdehydic form of oleuropein aglycone

O O

CH2 CO CH2 CH2

H3C O C

OH

CH CH3 O

OH

Ligostroside aglycone Figure 9.3 Continued

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Psomiadou and Tsimidou (2001) found no chlorophyll α and only traces of chlorophyll β and pheophytin β in a number of oils from various cultivars and various regions in Greece. The main pigments were pheophytin α and its unidentified derivatives, probably the pyro-derivative (loss of the carboxymethyl group) and a hydroxy-derivative formed by allomerisation. In the absence of light, chlorophylls may act as weak antioxidants. However, in the presence of light they act as strong oxidation promoters. The pro-oxidant effect of chlorophylls and pheophytins on the photo-oxidation of refined oils has been widely demonstrated. In natural olive oils a pronounced effect of the action of singlet oxygen may not be observed and this has to be attributed to the presence of singlet oxygen quenchers in natural olive oil. 9.3.3.4

Sterols

Four classes of sterols occur in olive oil: common sterols (4-α-desmethylsterols), 4-αmethylsterols, 4,4-dimethylsterols (triterpene alcohols) and triterpene dialcohols. Desmethylsterols This is the major class of sterols in olive oil. Usual values are 100–200 mg/100 g oil. Part of the total sterols is present as esters with fatty acids. β-Sitosterol makes up 75–90% of the total sterol fraction. Other sterols found in considerable amounts are Δ5-avenasterol (5–36% of the total sterol fraction) and campesterol (approximately 3% of the total sterol fraction). Other 4-desmethylsterols, present in olive oil and found only in trace or very small amounts, include cholesterol, campestanol, stigmasterol, Δ7-campesterol, chlerosterol (24S-24-ethyl-Δ5,25cholestadien-3β-ol), sitostanol, Δ5,24-stigmastadienol, Δ7-stigmasterol and Δ7-avenasterol. Virgin olive oil shows a remarkable resistance to oxidation and polymerisation during domestic deep frying of potatoes or in other uses at frying temperatures. Compared to vegetable oils such as sunflower, cottonseed, corn and soybean oils, olive oil shows a significantly lower rate of alteration, as demonstrated by measurements of viscosity, total polar compounds and loss of tocopherols. A possible explanation for the resistance of olive oil to rapid deterioration at elevated temperatures is its low iodine value and also the presence of Δ5-avenasterol. This sterol has an ethylidene side chain, which is a structural feature for retarding oxidative polymerisation in heated triacylglycerols (Blekas and Boskou 1999). 4-α-Methylsterols These compounds are intermediates in sterol biosynthesis and they are always present in small quantities in olive oil. 4-α-Methylsterols are difficult to quantify accurately because of their complex nature and their occurrence in both free and esterified form. Approximations based on combined thin-layer and gas chromatography with internal standards gave values ranging from 20–70 mg/100 g oil (Boskou et al. 2006). The predominating α-monomethyl sterols in olive oil are obtusifoliol (4α,14α-dimethyl-24-methylene-δ8-cholesten-3β-ol), cycloeucalenol (4α,14αdimethyl-9,19-cyclopropane-24-methylene-cholesten-3β-ol), gramisterol (4α-methyl-24-methylene-δ7-cholesten-3β-ol) and citrostadienol (4α-methyl,24-ethylidene-δ7-cholesten-3β-ol). Other minor sterols identified are 24-methyl-31-nor-9(11)-lanosterol, 24-methylene-31-nor-9(11)-lanosterol, 24-methyl-31-nor-E-23-dehydrocycloar-tanol, 24-methyl-E-23-dehydrolophenol, 24-ethyllophenol, 24-ethyl-E-23-dehydrolophenol, 24-methyl-24(25)-dehydrolophenol, 28-isocitrostadienol and 24-ethyl-24(25)-dehydrolophenol (Itoh et al. 1981). 4,4-Dimethylsterols (triterpene alcohols) The main triterpene alcohols present in olive oil are β-amyrin, butyrospermol, cycloartenol and 24-methylenecycloartanol. This sterol fraction is complex and many constituents are still unidentified. Itoh and his co-workers (1981) used argentation thin-layer chromatography

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and GC-MS to identify minor 4,4-dimethylsterols present in olive oil and olive pomace oil (β-residue oil). New compounds reported are taraxerol, dammaradienol, germaniol, parkeol, 7,24-tirucalladienol, 24-methylene-24-dihydroparkeol, cyclosadol and cyclobranol. Significant differences were observed by Itoh et al. (1981) between olive oil and β-residue oil in the composition of triterpene alcohol fractions, particularly in the percentage of 24-methylenecycloartanol. Significant differences were also observed between the distribution patterns of the total and esterified triterpene alcohol fraction in virgin olive oil, especially in the percentages of 24-methylenecycloartanol, butyrospermol and cycloartanol. Triterpene alcohols are present at concentrations ranging from 100–150 mg/100 g oil. Olive husk oil has a much higher content. 9.3.3.5

Tritepene dialcohols

The two main triterpene dialcohols of olive oil are erythrodiol (homo-olestranol, 5α-olean12-ene-3β,28-diol) and uvaol (Δ-12-ursen-3β,28-diol). Absolute amounts of erythrodiol plus uvaol range from 1–20 mg/100 g in olive oil and may be as high as 280 mg/100 g in β-residue oil. Triterpene dialcohols can be extracted and co-chromatographed with the 4-desmethyl sterol fraction. Their relative content in the total fraction as determined by GLC is used as a reliable indicator for distinguishing olive oil from β-residue oil. 9.3.3.6

Hydroxyterpenic acids

Pentacyclic hydroxyterpenic acids are important olive fruit constituents and biologically active compounds. They are isolated from the acidic fraction of olive oil by TLC, and are reported to be present in olive oil at levels between 40 and 185 mg/kg. Their levels are higher in high-acidity oils and in extracted oils. Oleanolic acid was found to be the reason for a turbidity that sometimes appears in physically refined olive oil. Severge (1983) suggested a modification of operating conditions to eliminate this problem. 9.3.3.7

Fatty alcohols, waxes and diterpene alcohols

Fatty alcohols are an important class of olive oil minor constituents because they can be used to differentiate various olive oil types. The main linear alcohols present in olive oil are docosanol, tetracosanol, hexacosanol and octacosanol. Odd carbon atom alcohols (tricosanol, pentacosanol, heptacosanol) may be present in trace amounts. Total aliphatic alcohol content does not usually exceed 35 mg/100 g oil. In olive-extracted oil, the level of fatty alcohols is ten times higher or even greater. Dry climatic conditions and high temperatures may cause a high alkanol content of olive oil. Alcohols in olive oil have been reviewed by Tiscornia et al. (1982) and Boskou et al. (2006). Waxes Waxes are esters of fatty alcohols with fatty acids. The olive oil wax content is very low and does not exceed 35 mg/100 g. Extracted olive oils have a high wax content and this difference is used officially for the distinction between pressed oil and β-residue oil. The main waxes detected in olive oil are C36–C46 esters, but the whole fraction is very complex because of the presence of several types of esters (saturated and unsaturated, straight-chain, even-numbered esters) and also benzyl alcohol, phytyl and geranylgeranyl esters (Reiter and Lorbeer 2001).

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Diterpenoids Two acyclic diterpenoids have been reported to be present in the alcohol fraction isolated from olive oil. These are phytol (at a concentration of 120–180 mg/kg), which probably originates from chlorophyll, and geranylgeraniol. Their levels are used in the calculation of the alcoholic index, a useful parameter for detecting solvent-extracted olive oil in virgin olive oil (Angerosa 2006). 9.3.3.8

Polyphenols

Virgin olive oil has a unique place among vegetable oils because of its minor constituents and much has been written in the last two decades about their importance. Both completed and ongoing studies associate these constituents with the beneficial role of olive oil in human health (Visioli 2000; Trichopoulou and Vasilopoulou 2000; Boskou 2009; Arbones-Mainar Navarro and Nou-Bonafonte 2009). The polyphenols are an important class of minor constituents linked both to the flavour of virgin olive oil and to its keepability. There are now many publications dealing not only with the nutritional effects of polyphenols, but also with the agronomic factors that influence their presence in olives and in olive oil, the mechanisms that contribute to a longer shelf-life and the importance of the processing conditions. Phenolic compounds present in olive oil are conventionally characterised as polyphenols, though not all of them are polyhydroxy aromatic compounds. They are part of the polar fraction usually obtained from the oil by extraction with methanol-water. Compounds that often appear in lists of olive oil polyphenols are (in alphabetical order) 4-acetoxy-ethyl-1,2-dihydroxybenzene, 1-acetoxy-pinoresinol, apigenin, caffeic acid, cinnamic acid (not a phenol), o- and p-coumaric acids, elenolic acid (not a phenol), ferulic acid, gallic acid, homovanillic acid, p-hydroxybenzoic acid, p-hydroxyphenylacetic acid, hydroxytyrosol, ligstroside luteolin, oleuropein, pinoresinol, protocatechuic acid, sinapic acid, syringic acid, tyrosol, vanillic acid and vanillin (Morales and Tsimidou 2000; Garcia et al. 2001; Mateos et al. 2001; Boskou 2009). Tyrosol (4-hydroxyphenylethyl alcohol) and hydroxytyrosol (3,4-dihydroxyphenylethyl alcohol) in their various forms are reported to be the major constituents. The more polar part of the methanol-water extract contains free phenols and phenolic acids. The less polar part contains aglycones of oleuropein and ligstroside (the hydroxytyrosol and tyrosol glycosides), diacetoxy and dialdehydic forms of the aglycones, elenolic acid, flavonoids (luteolin, apigenin), the lignans 1-acetoxypinoresinol and pinoresinol and cinnamic acid. Litridou et al. (1997) reported the presence of an ester of tyrosol with a dicarboxylic acid. The same investigators demonstrated that the total content of phenols and o-diphenols was higher in the less polar part of the methanol-water extracts. Glycosides were found to be present only in trace amounts. Garcia and his co-workers (2001) determined the dialdehydic forms of elenolic acid linked to hydroxytyrosol and tyrosol, 4-acetoxyethyl-1,2-dihydroxybenzene (hydroxytyrosol acetate), 1-acetoxypinoresinol, pinoresinol, oleuropein aglycone, luteolin and ligstroside aglycone as phenols with a higher concentration in Italian oils. The polyphenol content differs from oil to oil. Wide ranges have been reported (50–1000 mg/ kg), but values are usually between 100 and 300 mg/kg. The cultivar, system of extraction and conditions of olive oil processing are critical factors for the polyphenol content. Polyphenols are important for the flavour and stability of olive oil. When their content exceeds 300 mg/kg the oil may have a bitter taste. Formation of 4-vinylphenol from p-coumaric acid by decarboxylation or the presence of esters of cinnamic acid may also

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contribute to the flavour in a negative way. However, a high polyphenol content appears to be beneficial for the shelf-life of the oil and there is a good correlation of stability and total phenol content (Tsimidou et al. 1992; Monteleone et al. 1998). Among the various phenolic compounds tested for their contribution to the antioxidant effect, hydroxytyrosol was found to be the most potent and more effective than butylated hydroxy toluene (BHT). GutierrezRosales and Arnaud (2001) found that the concentration of hydroxytyrosol, the dialdehydic form of elenolic acid linked to hydroxytyrosol and oleuropein aglycone are highly correlated to the oil’s stability. 9.3.3.9

Volatile and aroma compounds

Olive oil also possesses a unique place among vegetable oils due to the mode of extraction and to the presence of volatile and non-volatile flavouring compounds. The most important constituents of the aroma of olive oil are C6 aldehydes and alcohols formed in the fruit from polyunsaturated fatty acids. This takes place on crushing, the first step of processing. The plant tissue is disrupted and a sequence of lipoxygenase-catalysed reactions occur. The hydroperoxides formed by oxidation of polyunsaturated fatty acids (18:2 and 18:3) are decomposed by a specific lyase, yielding aldehydes of six or nine carbon atoms and C12 or C9 oxo-acids. The aldehydes formed are transformed to the corresponding alcohols by reducing enzymes with dehydrogenase activity or to hexyl esters with specific transferases. The most important classes of volatiles are hydrocarbons, alcohols, aldehydes, esters, phenols, phenol derivatives, oxygenated terpenes and furan derivatives (Reiners and Grosch 1998; Morales and Aparicio 1999; Morales and Tsimidou 2000). For a review see Boskou et al. (2006). Approximately 280 compounds have been identified in the volatile fraction of virgin olive oils and the mechanisms for their formation have been suggested. Some of the volatile compounds are odourless (e.g. octane), while others, at least in the concentrations found, make only a very small contribution to the aroma. About 20 contribute to the flavour with sensory defects. In a series of papers, Grosch and his collaborators (Guth and Grosch 1991; Blekas et al. 1994; Blekas and Guth 1995) indicated that only a small fraction of the complex mixture of volatiles causes the characteristic odour of olive oil. To measure the potency of odorants, they applied a technique called aroma extract dilution analysis (AEDA). This is a screening method applied to the volatiles distilled in high vacuum. An aliquot of the sample is diluted in diethyl ether and analysed by capillary gas chromatography while the effluent of the capillary is sniffed. The aliquot is then diluted in a volume 1:1 and the new sample is analysed again. The procedure continues until no odour is detected. In this way the flavour dilution factor (FD-factor) is estimated. FD-factors are relative measures and are proportional to the odour activity value (OAV), which is the ratio of concentration to odour threshold of the compound in an odourless oil. Grosch and his co-workers concluded that the compounds mainly contributing to four basic flavour notes are: ● ● ● ●

green: (Z)-3-hexenal fruity: ethyl 2-methylbutyrate, ethyl isobutyrate, ethyl cyclohexylcarboxylate fatty: (Z)-2-nonenal blackcurrant: 4-methoxy-2-methyl-2-butanethiol

Other important odorants are (Blekas and Guth 1995; Reiners and Grosch 1998; Morales and Aparicio 1999):

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green: hexanal, (E)-2-hexenal, (E)-3-hexen-1-ol, (E)-2-hexen-1-ol fruity: hexyl acetate, (Z)-3-hexenyl acetate, 2-methylpropanoate, 2-methylbutanoate fatty: heptanal, (E)-2-nonenal, (E)-2-octenal, (Z)-3-nonenal, (E)-2- decenal grassy: hexanal (Z)-3-hexen-1-ol soapy: nonanal, octanal deep fried: 2,4-decadienal sweet: phenyl ethanol, phenyl acetaldehyde, hexyl acetate astringent-bitter: (E)-2-hexen-1-ol, (E)-2-hexenal

OAVs were calculated for potent odorants in oils from Italy, Spain and Morocco by Reiners and Grosch (1998). After quantification the concentrations of the odorants were divided on the basis of their nasally determined threshold values in sunflower oil. High OAVs were shown by the following compounds: ●

●

●

Oils from Italy: acetaldehyde, acetic acid, propanal, 1-penten-3-one, (E,Z)-2,4-decadienal, (Z)-3-hexenyl acetate, trans-4,5-epoxy-(E)-2-decenal, (Z)-3-hexenal and (E)-2-hexenal. Oils from Spain: acetaldehyde, acetic acid, trans-4,5-epoxy-(E)-2-decenal, 4-methoxy-2methyl-2-butanethiol, ethyl 2- and 3-methyl butyrate and 3-methyl butanal. Oils from Morocco: acetaldehyde, (E,Z)-2,4-decadienal, trans-4,5-epoxy-(E)-2-decenal, (Z)-3-hexenal, ethyl 2- and 3-methyl butyrate, ethyl cyclohexyl-carboxylate and ethyl isobutyrate.

According to Morales and Aparicio (2005), the main contributors to the fusty off-flavours from olive fruits in advanced stages of maturity are ethyl butanoate and also propanoic and butanoic acids. Responsible for the musty humidity off flavour is 1-octen-3-ol and to a lesser extent 1-octen-3-one. 9.3.3.10

Phospholipids

Experimental work for the determination of phospholipids in olive oil is rather limited. Freshly produced virgin olive oil was found to contain 40–135 mg/kg of phospholipids (Tiscornia et al. 1982). Crude pomace oil has higher levels. Phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidic acid and phosphatidylglycerol were the main phospholipids identified and quantified in a commercial olive oil sample by Boukchina et al. (2004). More recently, Hatzakis and others (2008) developed a non-destructive method based on high resolution 31P NMR spectroscopy for the determination of phospholipids. The phospholipids found in olive oil were phospaditic acid, lyso-phospatidic acid and phosphadidylinositol. The fatty acids composition in the phospholipids and triacylglycerols was similar. The level of phospholipids may be important, because these compounds have some antioxidant activity and act either as synergists by regenerating antioxidants or as metal scavengers (Pokorny and Korczak 2001). The possible contribution of phospholipids to the oxidative stability of olive oils has not been fully studied. Koidis and Boskou (2006) determined phosphorous in cloudy (veiled) olive oils, filtered oils and refined oils. Values obtained were in the range 1–6 mg P/kg oil, corresponding approximately to 20–156 mg phospholipids/kg oil. The veiled oils were found to be more stable to oxidation and this was attributed to the higher levels of phenols (Tsimidou et al. 2004) and possibly to the higher level of phospholipids.

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9.3.3.11

Metals

Transition metals, especially iron and copper, are known as pro-oxidant factors, because they generate free radicals. In virgin olive oil traces of iron and copper may originate from the soil and fertilisers or through contamination from the processing equipment and storage vessels. The use of stainless steel equipment is necessary to avoid metal contamination. Concentrations of iron reported for virgin olive oil usually range between 0.5 and 3 ppm. Values reported for copper are 0.001–0.2 ppm. The iron and copper content is related, at least in part, to the system used for the extraction of oil. Oils obtained by classical systems were found to have higher percentages of these two metals compared to oils extracted by the centrifugal and percolation techniques. Other metals present in virgin olive oil (chromium, manganese, tin, nickel and lead) do not exceed a few ppb.

9.4 9.4.1

EFFECT OF PROCESSING OLIVES ON THE COMPOSITION OF VIRGIN OLIVE OILS Aroma compounds

Olive oil crushing and kneading are important factors for aroma compounds. Lercker et al. (1999) found that after crushing Italian olives the volatile fraction contained approximately 20% trans-2-hexenal and after 70 minutes of kneading this increased to 50%. The hexanal content also increased, but its level remained significantly lower than that of hexenal. When kneading was over a different tendency was observed: an increase in hexanal and a decrease in hexenal. The authors concluded that strong enzyme activity and extended kneading periods generate desirable aroma compounds at the expense of stability through loss of antioxidants. Morales and Aparicio (1999) studied the conditions of extraction and showed that a temperature of 25 °C and a malaxing time of 30–45 minutes produce volatiles contributing to the best sensory quality. Higher temperatures (>35 °C) and minimum malaxing time (<30 min) produce oils with pleasant green notes. Ranalli and his co-investigators (2001) examined three Italian olive varieties and four malaxation temperatuures (20 °C, 25 °C, 30 °C and 35 °C). The results of the study indicated that by malaxing the paste at 30 °C a satisfactory oil output is obtained and the oil has a pleasant green flavour. Generally, malaxation times shorter than 45 minutes and low malaxation temperatures produce oils with better aromas and higher (E)-2-hexenal/hexanal ratios. The temperature of malaxation is critical because of the behaviour of hydroxyperoxide lyase, which affects the production of volatiles through the lipoxygenase pathway. Esposto et al. (2009) proposed online monitoring of C6 and C5 aldehydes, which may be helpful in defining the operative conditions of malaxation. The study is based on the use of an MOS sensor array connected to the malaxation chamber during the malaxation of olive pastes. The validity of the semiconductor sensor was checked by parallel analysis of volatiles by hyphenated solid phase-gas chromatography–mass spectroscopy.

9.4.2

Polyphenols

The content of polyphenols depends on the extraction system. Pressure systems and twophase decanters yield oil with a higher polyphenol content and longer induction periods. In the three-phase centrifugal systems the paste is thinned with water and part of the phenols is lost in the water (Di Giovacchino 1996).

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The type of crushing of the fruits also seems to be important. Stone mills give oil with a lower polyphenol content, while hammer crushers give oils with a characteristically high content of phenols. This suggests a difference in the enzymatic hydrolytic activity during crushing and may be used to upgrade the quality of extra virgin olive oils. Olives yielding oils with a very high content of polyphenols can be processed in a stone mill to avoid enhancement of ‘bitterness’ and ‘pungency’. For olives giving ‘sweet’ oils with a low level of polyphenols, it is better to use the hammer system (Caponio et al. 1999). The sensory and health properties of virgin olive are strongly related to its volatile and phenolic composition. Changes in volatile and phenolic compounds due to malaxation temperatures and time have been extensively studied by Kalua et al. (2006). Servili and his coworkers (2008) indicated that the control of oxygen concentration in the pastes during malaxation may be a new technological parameter to regulate enzymatic activities (lipogygenase, peroxidase, phenoloxidase), which affect the phenolic and volatile composition. They suggested an approach based on the monitoring of carbon dioxide and oxygen concentration during industrial olive paste malaxation, and establishing the relationships between the concentration of gases and aroma compounds and phenol composition. Gomez-Rico et al. (2009) stressed that malaxation should be considered to be more than a simple physical separation, because it is accompanied by a complex bioprocess affecting the composition and quality of the final product. Concerning the phenolics, kneading in an experimental mill showed that the major phenolic compound in the olive paste was the dialdehydic form of elenolic acid linked to hydroxytyrosol (a percentage higher than 60% of total phenols). As malaxation proceeds the concentration of this compound is gradually reduced. The changes in the phenolic compounds and the C6 aldehydes depended greatly on temperature and time of malaxation.

9.4.3

Other minor constituents

Among other minor constituents, carotenoids and chlorophylls are affected by the extraction system. Their level is higher in the oils obtained by centrifugation, because the metallic crushers used in this system release more of the pigments. The content of aliphatic alcohols and waxes may increase if the temperature of the paste is too high (Cert et al. 1999).

9.5 9.5.1

REFINING AND MODIFICATION Olive oil and olive pomace oil refining

Refining is applied to olive pomace oil and non-edible grades of virgin olive oil with high acidity and unacceptable sensory characteristics. Alkali refining, bleaching and deodorisation are the standard procedures. Physical refining may also be used, but the temperatures applied can lead to the formation of trans fatty acids and promote interesterification reactions, which increase the percentage of saturated acids at the β-position of triacylglycerol molecules. Attempts are now being made to deodorise olive oil using nitrogen as a stripping gas (Ruiz-Mendez and Dobarganes 1999). This is expected to increase free fatty acid vaporisation efficiency and also to reduce losses of unsaponifiables and triacylglycerols. Olive residue oil needs two additional steps, degumming and winterisation. Degumming is necessary for olive pomace oil because it contains phospholipids and is achieved by treatment with phosphoric or citric acid to form hydrated phospholipids. Winterisation removes

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waxes and high-melting triacylglycerols. The process is based on freezing (5–8 °C), ‘maturing’ to increase the size of the crystals, and the addition of 5% water. The mixture of oil and water is placed in a centrifuge, which separates the aqueous phase with the wax from the (dewaxed) oil. Further washing with warm water and centrifugation eliminates the residual impurities (mainly soaps). When winterisation is carried out in a hexane solution the operation is performed before bleaching. Trends in olive oil and olive pomace oil processing (neutralisation, bleaching, deodorisation), monitoring of effective refining and basic quality parameters have been discussed by Antonopoulos et al. (2006).

9.5.2

Refining and minor constituents

Refining is applied to remove constituents (pigments, free fatty acids, oxidation products) that make the oil unsuitable for edible purposes. However, alkali treatment, bleaching earths and the high temperatures used in the deodorisation step may cause an unwanted loss of tocopherols. Changes taking place during refining can be used to check the identity of refined olive oils and to recognise admixtures with natural olive oil. 9.5.2.1

Sterols

Alkali refining may cause a reduction of sterols of up to 15%. Losses are also observed during decolorisation and deodorisation. Free 4α-methylsterols and triterpene alcohols undergo severe changes during bleaching. Isomerisation of the side chain and opening of the 9β-19cyclopropane ring may occur. The intensity of bleaching can be assessed by the presence of steradienes formed from the dehydration of sterols. The determination of these hydrocarbons is an effective means of detecting refined oils labeled as non-refined. The main steradienes found are stigmasta-3,5-diene (from β-sitosterol), campesta-3,5-diene (from campesterol) and 3,5,22-stigmastatriene (from stigmasterol). 9.5.2.2

Fatty acids and triacylglycerols

In the various stages of refining, conjugated double-bond systems and geometrical isomers are formed. Dienes absorb at 232 nm and trienes at 268 nm. Trans fatty acids are detected by capillary gas chromatography or by argentation thin-layer chromatography combined with gas chromatography. In addition to geometrical isomerisation, long deodorisation periods at high temperatures may result in interesterification, with a consequent increase in palmitic acid at the 2-position of the triacylglycerols. 9.5.2.3

Alkanols

The content of linear alcohols increases during refining through the liberation of alcohols from waxes. 9.5.2.4

Tocopherols and squalene

Tocopherols and squalene are removed when the olive is processed. Deodorisation sludges are rich in squalene and can be used as a source of this hydrocarbon for industrial purposes. Squalene losses are accompanied by the formation of squalene isomers in the deodorised oil.

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261

Phenolic compounds

These compounds are very polar, dissolve in the water used in the various refining steps and are lost. 9.5.2.6

Other constituents

Various other constituents are drastically reduced or disappear completely. These are pigments, triterpene acids, phospholipids, aroma compounds and contaminants such as metals, aromatic hydrocarbons and insecticide residues. While volatile hydrocarbons disappear others, such as diterpenes, may be formed by the degradation of phytol.

9.6

HARDENING AND INTERESTERIFICATION

Olive oil is too valuable to be hydrogenated, since even non-edible oils (lampante) are usually more expensive than commodity seed oils. Small quantities may be neutralised, decolorised and hydrogenated when there is a surplus of raw material. To obtain a plastic product suitable for the preparation of cooking fats or margarines, olive oil has to be hydrogenated under conditions that favour stereomutation. Finished products usually have a low percentage of diene acids and a rather high level of undesirable geometrical and positional isomers. Interesterification of blends of refined olive oil and tristearin gives zero-trans plastic fats with a higher percentage of unsaturated fatty acids than hydrogenated olive oil. Gavriilidou and Boskou (1991) interesterified blends of refined olive oil and glycerol tristearin on a laboratory scale using sodium methoxide as a catalyst. The rearranged fats had properties very close to those of soft tube and packed margarines. Blends of refined olive oil and partially hydrogenated palm oil were subjected to chemical and enzymic interesterification by Alpaslan and Karaali (1998). The products were similar to those of package margarines, but higher in mono-unsaturated fatty acids. Vural et al. (2004) prepared interesterified olive oil to be used as a beef fat substitute in sausages and to obtain a better ratio of unsaturated to saturated fatty acids. Other attempts have been made to use olive oil in the preparation of the so-called structured lipids (Fomuso et al. 2002; Tynek and Ledochowska 2005). Criado and co-workers (2008) prepared various products via enzymatic interesterification of extra virgin olive oil and fully hydrogenated palm oil. These products with a high molar ratio of monounsaturated to saturated fatty acids at the sn-2 position were soft over a wide range of temperatures and their potential applications included margarines and cooking fats. Lee and his co-workers (2008) also reported the preparation of interesterified plastic fats, free from trans fatty acids and with varying physical properties, using olive oil and fully hydrogenated soybean oil and palm stearin.

9.7

QUALITY, GENUINENESS AND REGULATIONS

Criteria for the quality and genuineness of the various olive oil types are described in the Norm of the Codex Alimentarius and EU Commission Regulation 2568/91 and its amendments. An important amendment of the basic regulation is Regulation 1989/2003, which summarises most of the changes since 1991.

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The Codex Alimentarius and the International Olive Oil Council standard for olive oil (2003) include additional limits for volatile matter, insoluble impurities, colour, taste, iron, copper, permitted additives, contaminants (lead, arsenic, halogenated solvents), refractive index, saponification value, iodine value and unsaponifiable matter. Physical and chemical constants such as iodine value and saponification value are not found in the EU regulation. This is explained by the fact that more definite information is obtained by determining fatty acid composition, sterol and wax composition, trans fatty acid content, stigmastadiene and so on. In the Codex Alimentarius an additional class (ordinary olive oil) is recognised with acidity less than 3.3% in oleic acid. This category is not included in the European standards. Non-edible forms begin from free acidity above 2%.

9.7.1

Olive oil

The descriptions and definitions given below are included in the standards of the organisations already mentioned. 9.7.1.1

Virgin olive oil

The oil obtained from the fruit of the olive tree (Olea europaea) only by mechanical or other physical means under conditions, particularly thermal, that do not lead to alteration in the oil and that has not undergone treatment other than washing, decantation, centrifugation and filtration. ●

●

●

●

●

●

●

●

●

Extra virgin olive oil. This type has a maximum acidity of 0.8 g/100 g in terms of oleic acid and other characteristics, according to regulations in force. Virgin olive oil. This type has maximum acidity of 2 g/100 g in terms of oleic acid and other characteristics according to regulations in force. Ordinary virgin olive oil. This type has a maximum acidity in terms of oleic acid of 3.3 g/100 g. It is not included in the European Regulation. Virgin lampante olive oil. This oil has an acidity in terms of oleic acid of more than 3.3 g/100 g. Refined olive oil. This oil, which is obtained from virgin olive oil by refining methods that do not lead to alteration in the initial triacylglycerol structure, has a maximum acidity in terms of oleic acid of 0.3 g/100 g. Olive oil. This oil, which consists of a blend of virgin olive oil (except lampante) and refined olive oil, has a maximum acidity in terms of oleic acid of 1.0 g/100 g and other characteristics according to regulations in force. Crude olive pomace oil (crude olive residue oil). This oil is obtained by treating olive pomace with solvents. Oils obtained by re-esterification processes and mixtures with other oils are excluded from this class. Other characteristics are according to regulations in force. Refined olive pomace oil. This oil, which is obtained from crude olive pomace oil by refining methods not altering the initial triacylglycerol structure, has an acidity of no more than 0.3 g/100 g and other characteristics according to regulations in force. Olive pomace oil. This oil, which is a mixture of refined olive residue oil and virgin olive oil (except lampante), has a maximum acidity in terms of oleic acid of 1 g/100 g and other characteristics according to regulations in force.

The identity and quality characteristics of the above types of olive oil are given in Table 9.2. Theoretical ECN42 values are calculated from the fatty acid composition and the

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≤0.8 ≤2.0 >2.0 ≤0.3 ≤1.0 – ≤0.3 ≤1.0

1 2 3 4 5 6 7 8

≤20 ≤20 – ≤5 ≤15 – ≤5 ≤15

C

≤250 ≤250 ≤300 ≤350 ≤350 >350 ³350 >350

D

F

G

H

I

J

K

≤1.5 ≤0.15 ≤0.2 ≤2.50 ≤0.22 ≤0.01 Md 0 Mf >0 ≤1.5 ≤0.15 ≤0.2 ≤2.60 ≤0.25 ≤0.01 Md ≤ 2.5 Mf >0 ≤1.5 ≤0.50 ≤0.3 – – – Md >2.5 – ≤1.8 – ≤0.3 – ≤1.10 ≤0.16 – ≤1.8 – ≤0.3 – ≤0.90 ≤0.15 – ≤2.2 – ≤0.6 – – – – ≤2.2 – ≤0.5 – ≤2.5 ≤0.20 – ≤2.2 – ≤0.5 – ≤1.70 ≤0.18 –

E

Olive oil characteristics.

0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

1.0 0.10 0.9 0.10 0.10 0.10 0.10 0.10

0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

0.2 0.2 0.2 0.2 0.2 0.3 0.3 0.3

0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

14:0 18:3 20:0 20:1 22:0 24:0 ≤0.05 ≤0.05 ≤0.10 ≤0.20 ≤0.20 ≤0.20 ≤0.40 ≤0.40

L ≤0.05 ≤0.05 ≤0.10 ≤0.30 ≤0.30 ≤0.10 ≤0.35 ≤0.35

M ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5

N ≤0.1 ≤0.1 ≤0.1 ≤0.1 ≤0.1 ≤0.2 ≤0.2 ≤0.2

O ≤4.0 ≤4.0 ≤4.0 ≤4.0 ≤4.0 ≤4.0 ≤4.0 ≤4.0

P * * * * * * * *

Q ≥93.0 ≥93.0 ≥93.0 ≥93.0 ³93.0 ³93.0 ³93.0 ≥93.0

R

T ≤0.5 ³1000 ≤0.5 ³1000 ≤0.5 ³1000 ≤0.5 ³1000 ≤0.5 ³1000 ≤0.5 ³2500 ≤0.5 ³1800 ≤0.5 ≥1600

S

≤4.5 ≤4.5 ≤4.5 ≤4.5 ≤4.5 >4.5 ³4.5 >4.5

U

Source: European Union Commission Regulation 1989/2003. Note: * present at levels lower than that of campesterol. Key: A 1 Extra virgin olive oil, 2 Virgin olive oil, 3 Virgin lampante olive oil, 4 Refined olive oil, 5 Olive oil, 6 Crude olive-residue oil, 7 Refined olive-residue oil, 8 Olive-residue oil B Acidity % C Peroxide value mEq02/kg D Waxes mg/kg E Saturated fatty acids in triacylglycerols at position 2 (%) F Stigmastadienes mg/kg G Difference between HPLC and theoretical calculation of ECN42 H K232 I K270 J Delta K Panel test, median of defects, median of fruity 14:0 (myristic acid %), 18:3 (linolenic acid %), 20:0 (arachidic acid %), 20:1 (eicosenoic acid %), 22.0 behenic acid %, 24:0 (lignoceric acid %) L Sum of trans oleic % M Sum of trans linoleic and linolenic N Cholesterol % O Brassicasterol % P Campesterol % Q Stigmasterol % R β-sitosterol % S Δ-7-stigmasterol % T Total sterols mg/kg U Erythrodiol plus uvaol, % of sterol fraction

B

A

Table 9.2

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1,3-random, 2-random distribution theory using an appropriate computer program. The difference between theoretical values and real values obtained by HPLC has replaced trilinolein content. K232 and K270 are specific UV extinctions of 1% solution of the fat in a specified solvent, in a cell of thickness 1 cm. Panel tests express the assessment of trained tasters, on a 0–9 scale. 9.7.1.2

Cloudy and unrefined olive oil

Extra virgin olive oil can be produced in the form of an emulsion or dispersion, which can persist for several months before full deposition of a residue. Many chefs prefer this natural slight cloudiness in salads or in gourmet dishes and there is a growing interest in cloudy (veiled) extra virgin olive oil. Some consumers consider this to be more ‘green’ and not overprocessed, but this is not correct because the additional ‘processing’ is only precipitation and filtering. Veiled oils have longer induction periods compared to filtered oils. It is, therefore, believed that the material in suspension-dispersion that ‘veils’ extra virgin olive oil plays a significant stabilising role against oxidation, although there is little evidence concerning the chemical nature of the material that forms the stable dispersion system. Another possible explanation might be the presence of emulsifiers. There are compounds in the oil with a low solubility in water that act as tensioactive solutes. Mono- and di-acylglycerols and galactolipids belong to this category. Bianco and his co-workers (1998) identified two digalactosyl glycosides in freshly produced oils, a α-1,6-digalactosyl derivative of the 1,2-glycerol diester of linolenic acid and a α-1,6-digalactosyl derivative of the glycerol linolenate-oleate diester. The physicochemical characteristics of such compounds and the stable emulsions formed may allow an increase in the transfer of hydrophilic phenolic compounds (mainly o-diphenols), which are strong antioxidants. Tsimidou et al. (2004) found a higher total phenolic compounds content in veiled oils in relation to the filtered oil and this may partly explain the higher stability. A lipoxygenase activity has been detected in freshly prepared olive oils (Georgalaki et al. 1998). Taking into consideration the higher stability of cloudy oil, it can be postulated that the polar phenolic compounds present act not only as primary antioxidants but also as inhibitors of oxidising enzymes.

9.7.2

Analysis and authentication

It is clear from the definitions and standards that olive oils, and especially virgin olive oil, are strictly regulated. This is related to their high price and to the fact that natural olive oil has always been the subject of fraud by mixing less expensive vegetable oils and olive residue oil. The importance of quality and identity parameters for the various types of olive oil, the analytical methods and the significance of limits not included in the official methods of analysis for detecting authenticity have been analytically discussed by Angerosa (2006). The evaluation of the quality and the control of the genuinenesss of olive oil are made on the basis of analytical data of a number of parameters, which must be within the limits established. In addition to the analytical methods already described in EU legislation and the IOOC standards, researchers continually propose methods and approaches that support results of non-conclusive official analysis (in cases of very sophisticated adulteration) or attempts to identify geographical origin and typicality.

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9.7.2.1

265

Quality parameters not included in the standards

In addition to measurements of acidity, peroxide value, UV absorbance, organoleptic assessment, halogenated solvents, metals, volatiles, unsaponifiables and insoluble impurities and α-tocopherol that are considered official, other measurements have been proposed related to the level of antioxidants, hydrolysis products, pigments and contaminants. Total phenolics and individual phenols contribute to a better assessment of the oil’s stability. Some phenols are responsible for the bitter taste (Boskou 2009). Methods for the analysis of phenols by high-performance liquid chromatography, NMR spectroscopy and other techniques have been discussed by Angerosa (2006) and Dais and Boskou (2009). Certain volatiles related to sensory defects such as heptenals, hexanals and pentanals can be used to detect the progress of the autoxidation process. Partial glycerides also provide parameters to check freshness. Pigments such as pheophytin-α and their degradation products are also useful in the quality control of virgin olive oil (Anniva et al. 2006). 9.7.2.2

Genuineness

The chemical and physical constants used to reveal adulteration of virgin olive oil with seed oils, refined olive and olive pomace oils are iodine value, refractive index, fatty acid composition, total and individual sterols, trans isomers of fatty acids, fatty acids at the 2-position of triacylglycerols, ΔECN42 values, erythrodiol and uvaol content, wax content, aliphatic alcohols, stigmastadienes and spectrophotometric constants at 230 and 270 nm. Other proposed methods not included in official standards include HPLC analysis of triacylglycerols and analysis of the hydrocarbon fraction. Today there are also many techniques to characterise olives according to variety and origin and to verify some properties of oils with a denomination of protected origin (DOP). The analysis of sterols has been proposed for the detection of hazelnut oil in olive oil. Hazelnut oil has a similar fatty acid composition to olive oil. Azadmard-Damirchi and Dutta (2006, 2007) used a solid-phase extraction method to separate 4-desmethyl-, 4-monomethyland 4,4-dimethylsterol fractions, which were further analysed by gas chromatography and gas chromatography–mass spectrometry. Significant differences were observed in the 4,4dimethylsterol fractions between olive oil and hazelnut oil. The presence of lupeol in this fraction can permit the detection of olive oil adulteration at levels as low as 2%. A series of publications in recent years has focused on differentiation according to cultivar and geographical area. Methods tested so far include mainly separation techniques, spectroscopic techniques and mass spectrometry. Chemometric analysis of the data is also necessary. Vichi and others (2006) proposed the composition of the sesquiterpene hydrocarbon fraction to differentiate oils from different cultivars, after headspace solid-phase microextraction coupled to gas chromatography–mass spectrometry. Garcia-Gonzales (2009) attempted a geographical identification of virgin olive oils from Spain, Italy and Portugal. A total of 64 compounds were analysed by gas chromatography and high-performance liquid chromatography. Artificial neural network (ANN) models were used for each of the levels of a proposed classification scheme, while an extremely high number of samples from the three countries served as training and as test sets for the ANN models for the grouping of samples according to country fatty acid analysis. For the verification of claims for the oils with protected designation of origin (PDO) status, additional data from the analysis of sterols, alcohols and hydrocarbons were required. Other emerging techniques tested for their ability to differentiate geographical

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origin are stable isotope ratio, nuclear magnetic resonance and FT-IR in combination with principal component analysis or other chemometric methods. One of the innovative approaches that can facilitate assessment of the place of origin is based on the identity of DNA, when this is recoverable from olive oil samples and can be amplified by PCR techniques (Busconi et al. 2003; Angerosa 2006).

9.8

CONSUMPTION AND CULINARY APPLICATIONS

The Mediterranean diet has been associated with a lower incidence of degenerative diseases such as cardiovascular disease and certain cancers. These health benefits have been partially attributed to the consumption of virgin olive oil by Mediterranean populations. Olive oil’s biological value is related to its fatty acid composition. In 2004 the US Food and Drug Administration announced the availability of a qualified health claim for monounsaturated fat from olive oil and a reduced risk of coronary heart disease (CHD). According to the FDA, there is evidence that individuals may reduce their risk of CHD if they consume monounsaturated fat from olive oil and olive-containing food in the place of highly saturated fat, while at the same time not increasing the total number of calories consumed. However, the biological value of olive oil is probably due not only to its fatty acid composition but also to the nature and level of its minor constituents. Recent research has focused on the biologically active phenolic compounds and diterpene acids and alcohols naturally present in the oil. A large number of studies (in vivo, in vitro, animal, human) have indicated that olive oil phenolics have positive effects on a number of physiological effects such as plasma lipids, oxidative damage, inflammation platelet and cellular function and antimicrobial activity. The results of such studies may justify the characterisation of olive oil as a ‘functional food’ (Stark and Madar 2002). (For reviews see Trichopoulos and Trichopoulou 2009; Covas et al. 2009; Antonopoulou et al. 2009; Kampa et al. 2009; Dilis and Trichopoulou 2009.) Global olive oil production in the last five years was approximately 2.5 million tonnes. The main producing countries are Spain, Italy, Greece, Tunisia, Turkey, Syria, Morocco, Algeria, Portugal and Jordan. There is smaller-scale production in Argentina, Croatia, Israel, Lebanon, Libya, Palestine and France and even smaller in Cyprus, Mexico and the USA. World consumption during the period 2004/05 averaged 2.738 million tonnes (International Olive Oil Council). The share of this consumption is main producer countries (Italy, Spain, Greece and Portugal) 72%; USA, Australia, Japan and Brazil, 11.5%’ Tunisia, Turkey, Syria and Morocco, 10%. Spain, Italy and Greece, the main producing countries, have the highest total consumption and the highest per capita per year consumption, followed by Portugal, Syria, Tunisia, Jordan, Libya and Lebanon. Virgin olive oil has a remarkable stability and can be stored for 18 months or more. Resistance to the development of rancidity is combined with a vast array of flavour notes and colour hues, as well as distinct features due to differences in the olive cultivars from which the oil is extracted. These qualities offer opportunities for a variety of culinary applications with no or very little processing. Olive oil contributes flavours that are reflected throughout the dish. A good-quality olive oil blends perfectly with green vegetables. Traditional dishes are prepared with seasonal vegetables, various greens, parsley and grains. In vegetarian dishes olive oils with herbal hues are usually preferred. For salads a pronounced hint of apple is suitable, while for grilled meats a peppery flavour is desirable. Other dishes such as pies, mayonnaise, fried

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eggs and so on require different hues for those who go deeply into sensorial characteristics like mouth feel, bouquet, taste and aftertaste and have developed their own personal preferences. ‘Freshly cut grass flavour’, ‘flowery aroma’, ‘pepperiness’ and other such comments are very likely to be heard, not only in oil-tasting parties but even in common discussions among consumers with a sophisticated palate. The taste of olive oil is very often complemented by the sharp taste of vinegar, lemon or tomato. A simple traditional salad dressing is an instantly beaten mixture of olive oil and lemon juice, a rich source of both lipid-soluble and water-soluble vitamins. In salads or in cooking, olive oil is usually mixed with herbs and spices, which are also important elements of the Mediterranean diet. Herbs like oregano, rosemary or thyme and others from the plants of the Lamiaceae family are rich sources of phenolic compounds with strong antioxidant activity (Tsimidou and Boskou 1994; Antoun and Tsimidou 1997; Exarchou et al. 2001). These herbs maintain the nutritional value of the food and enhance the shelf-life of the food product. The stability and biological importance of olive oil have stimulated the interest of the food industry. Today in the market many patented products such as margarines, mayonnaise and meat products contain olive oil. The justification for such products is better stability, a better balance of saturated, monounsaturated and polyunsaturated fatty acids and additional nutritional benefits (Ansorena and Astiazaran 2004; Vural et al. 2004).

9.8.1

Olive oil in frying

Olive oil shows remarkable stability during domestic deep frying of potatoes or in other uses requiring frying temperatures (Boskou 1999). When compared to other vegetable oils such as sunflower, cottonseed, corn and soybean oil, olive oil has a significantly lower rate of alteration. This increased stability to thermal oxidation explains why the oil can be used for repeated frying. The reason for the resistance of olive oil to rapid deterioration at elevated temperatures is its fatty acid composition and the presence of natural antioxidants, such as tocopherols, squalene and Δ5-avenasterol (Blekas and Boskou 1999). The polar antioxidants found in virgin olive oil may also make a contribution to the increased stability to thermal oxidation and polymerisation. These properties of olive oil are well known to people of the Mediterranean basin, who traditionally use good-quality olive oil for frying, but only for a limited number of times. According to Varela (1992), deep frying in olive oil offers a means to improve the lipid intake profile, since during the frying process there are important changes in fat composition because of the olive oil’s penetration into the fried food. Western diets using blended oils containing animal fats are rich in saturated fats and also in the linoleic acid (n-6) series. If, however, meat is cooked in olive oil, there is a favorable change in the saturated to polyunsaturated fatty acids ratio. A better combination is to cook fish with olive oil. If sardines, for example, are fried in olive oil, the nutritional benefits of the oil are combined with the n-3 series fatty acids from the fish (Cuesta et al. 1998). When frying is extended, the concentration of phenolics, especially that of hydroxytyrosol and oleuropein derivatives, is reduced significantly. Losses of antioxidant activity have been measured by ABTS and DPPH radical decolorisation, electron spin resonance and other methods. These measurements indicate that the oil has a remarkable stability and reaches the rejection time in longer times compared to other oils, but when health effects are expected from the phytochemicals present, the number of heating operations should be kept to a minimum (Boskou 2009).

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REFERENCES Alpaslan, S.L. and Karaali, A. (1998) The interesterification-induced changes in olive oil and palm oil blends, Food Chemistry, 61, 301–305. Angerosa, F, (2006) Analysis and authentication, in Olive Oil, Chemistry and Technology (ed. D. Boskou), AOCS Press, Champaign, IL, pp. 93–112. Anniva, C., Grigoriadou, D., Psomiadou, E. and Tsimidou, M. (2006) Pheophytin- alpha degradation products as useful indices in the quality control of virgin olive oil, Journal of the American Oil Chemists’ Society, 83, 1–5. Ansorena, D. and Astiazaran, I. (2004) Effect of storage and packaging on fatty acid composition and oxidation in dry fermented sausages made with added olive oil and antioxidants, Meat Science, 67, 337–244. Antonopoulos, K.,Valet, N., Spiratos, D. and Siragakis, G. (2006) Olive oil and pomace olive oil processing, Grasas Aceites, 57, 56–67. Antonopoulou, S., Karantonis, C. and Nomikos, T. (2009) Antithrombotic and antiatherogenic lipid minor constituents from olive oil, in Olive Oil: Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 173–193. Antoun, N. and Tsimidou, M. (1997) Gourmet olive oils: Stability and consumer acceptability studies, Food Research International, 30, 131–136. Arbones-Mainar Navarro, J.M. and Nou-Bonafonte, J.M. (2009) Olive Oil Phenolics as Potential Therapeutic Agents, Nova Science, New York. Azadmard-Damirchi, S. and Dutta, P.C. (2006) Novel solid-phase extraction method to separate 4-desmethyl-, 4-monomethyl- and 4,4-dimethylsterols in vegetable oils, Journal of Chromatography A,1108, 183–187. Azadmard-Damirchi, S. and Dutta, P.C. (2007) Free and esterified 4,4-dimethylsterols in hazelnut oil and their retention during refining processes, Journal of the American Oil Chemists’ Society, 84, 297–304. Bianco, A., Mazzei, R.A., Malchioni, C. et al. (1998) Microcomponents of olive oil. Part II: Digalactosyldiacylglycerols from Olea Europaea, Food Chemistry, 62, 343–346. Blekas, G. and Boskou, D. (1998) Antioxidative activity of 3,4-dihydroxyphenylacetic acid and α-tocopherol on the triglyceride matrix of olive oil: Effect of acidity, Grasas Aceites, 49, 34–37. Blekas, G. and Boskou, D. (1999) Phytosterols and stability of frying oils, in Frying of Food (eds D. Boskou and I. Elmadfa), Technomic Publishing, Lancaster, pp. 205–222. Blekas, G. and Guth, H. (1995) Evaluation and quantification of potent odorants of Greek virgin olive oil, in Food Flavours: Generation, Analysis and Process Influence (ed. G. Charalambous), Elsevier, Amsterdam, pp. 419–427. Blekas, G., Guth, H. and Grosch, W. (1994) Changes in the levels of olive oil odorants during ripening of the fruits, in Trends in Flavour Research (ed. H. Maarse and D.G. Vander Heij), Elsevier Sciences, Amsterdam, pp. 449–502. Blekas, G., Tsimidou, M. and Boskou, D. (1995) Contribution of α-tocopherol to olive oil stability, Food Chemistry, 52, 289–294. Boskou, D. (1999) Non-nutrient antioxidants and stability of frying oils, in Frying of Food (eds D. Boskou and I. Elmadfa), Technomic Publishing, Lancaster, pp. 183–204. Boskou, D. (2009) Phenolic compounds in olives and olive oil, in Olive oil. Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 11–54. Boskou, D., Blekas, G. and Tsimidou, M. (2006) Olive oil composition, in Olive Oil, Chemistry and Technology (ed. D. Boskou), AOCS Press, Champaign, IL, pp. 41–72. Boukchina, S., Sebai, K., Cherif, A., Kallel, L. and Mayer, P. (2004) Identification of glycerophospholipids in rapeseed, olive, almond and sunflower oils by LC-MS and LC-MS-MS, Canadian Journal of Chemistry, 82, 1210–1215. Busconi, M., Foroni, C., Corradi, M. et al. (2003) DNA extraction from olive oil and its use in the identification of the production cultivar, Food Chemistry, 83, 127–134. Caponio, F., Alloggio, V. and Gomes, T. (1999) Phenolic compounds of virgin olive oil: Influence of paste preparation techniques, Food Chemistry, 64, 203–209. Cert, A., Alba, J. and Perez-Camino, C. (1999) Influence of extraction methods on the characteristics and minor components of extra virgin olive oil, Olivae, 79, 41–50.

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Olive Oil

269

Covas, M-I., Khymentes, O., Fito, M. and de la Torre, R. (2009) Bioavailability and antioxidant effect of olive oil phenolic compounds in humans, in Olive Oil: Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 109–128. Criado, M., Hernandez-Martin, E., Lopez-Hernandez, A. and Otero, C. (2008) Enzymatic interesterification on olive oil with fully hydrogenated palm oil: Characterization of fats, European Journal of Lipid Science Technology, 110, 714–724. Cuesta, I., Perez, M., Ruiz-Roso, B. and Varela, G. (1998) Comparative study of the effect on the sardine fatty acids composition during deep frying and canning in olive oil, Grasas Aceites, 49, 371. Dais, P. and Boskou, D. (2009) Detection and quantification of phenolic compounds in olive oil, olives and biological fluids, in Olive Oil: Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 55–107. Di Giovacchino, L. (1996) Olive harvesting and olive oil extraction, in Olive Oil (ed. D. Boskou), AOCS Press, Champaign, IL, pp. 12–51. Dilis, V. and Trichopoulou, A. (2009) Mediterranean Diet and Olive Oil Consumption: Estimation of Daily Intake of Antioxidants from Virgin Olive Oil, CRC Press, Boca Raton, FL, pp. 201–210. Esposto, S., Montedoro, G., Selvaggini, S. et al. (2009) Monitoring of virgin olive oil volatile compounds evolution during olive oil malaxation by an array of metal oxide sensors, Food Chemistry, 113, 345–350. Exarchou, V., Troganis, A., Gerothanassis, I.P., Tsimidou, M. and Boskou, D. (2001) Identification and quantification of caffeic and rosmarinic acid in complex plant extracts by the use of Variable-Temperature Two-Dimensional Nuclear Magnetic Resonance Spectroscopy, Journal of Agricultural Food Chemistry, 49, 2–8. Eyres, L. (1999) Functional food from olive oil and grain germ, Patent abstracts, Lipid Technology, 11, 22. Fedeli, E. (1996) Olive oil extraction technology and preservation, in World Olive Encyclopaedia, International Olive Oil Council, Madrid, pp. 253–291. Fomuso, L.B., Corredig, M. and Acoh, C.C. (2002) A comparative study of mayonnaise and Italian dressing prepared with lipase catalyzed transesterified olive oil and caprylic acid, Journal of the American Oil Chemists’ Society, 78, 771–774. Gapor Md Top, A. and Rahman, H.A. (2000) Squalene in oils and fats, Palm Oil Developments, 32, 36–40. Garcia, A., Brenes, M., Martinez, F. et al. (2001) High performance liquid chromatography evaluation of phenols in virgin olive oil during extraction of laboratory and industrial scale, Journal of the American Oil Chemists’ Society, 78, 623–629. Garcia-Gonzales, D.L. (2009) Stepwise geographical traceability of virgin olive oils by chemical profiles using artificial neural network models, European Journal of Lipid Science Technology, 11, 1003–1013. Gavriilidou, V. and Boskou, D. (1991) Chemical interesterification of olive-tristearin blends for margarines, International Journal of Food Chemistry, 26, 451–456. Georgalaki, M.D., Sotiroudis, T.G. and Xenakis, A. (1998) The presence of oxidizing enzyme activities in virgin olive oil, Journal of the American Oil Chemists’ Society, 75, 155–159. Gertz, C. and Fiebig, H.-J. (2006) Isomeric diacylglycerols. Determination of 1,2-and 1,3- diacylglycerols in virgin olive oil, European Journal of Lipid Science Technology, 108, 1066–1069. Gomez-Rico, A., Inarejos-Garcia, M., Desamparados Salvador, M. and Freggapane, G. (2009) Effect of malaxation conditions on phenol and volatile profiles in olive paste and the corresponding virgin olive oils (Olea europaea L.Cv. Corniraba), Journal of Agricultural Food Chemistry, 57, 3587–3595. Guth, H. and Grosch, W. (1991) A comparative study of the potent odorants of different virgin olive oils, Fat Science Technology, 93, 335–339. Gutierrez-Rosales, F. and Arnaud, T. (2001) Contribution of polyphenols on the oxidative stability of virgin olive oil, 24th World Congress and Exhibition of the ISF, Berlin, September, Abstracts, pp. 61–62. Hatzakis, E., Koidis, A., Boskou, D. and Dais, P. (2008) Determination of phospholipids in olive oil by 31P NMR spectroscopy, Journal of Agricultural Food Chemistry, 56, 6232–6240. Itoh, T., Yoshida, K., Yatsu, T., Tamura, T. and Matsumoto, T. (1981) Triterpene alcohols and sterols of Spanish olive oil, Journal of the American Oil Chemists’ Society, 58, 545–550. Kalua, C.M., Bedgood, D.R., Bishop, A.G and Prenzie, P.D. (2006) Changes in volatile and phenolic compounds with malaxation time and temperature during virgin olive oil production, Journal of Agricultural Food Chemistry, 54, 7641–7651. Kampa, M., Pelekanou, V., Nota, G. and Castanas, E. (2009) Olive oil phenols, basic cell mechanisms and cancer, in Olive Oil: Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 129–172.

Gunstone_c09.indd 269

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270

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Koidis, A. and Boskou, D. (2006) The content of proteins and phospholipids in cloudy (veiled) virgin olive oil, European Journal of Lipid Science Technology, 108, 323–328. Lanzon, A., Albi, T., Cert, A. and Gracian, J. (1994) The hydrocarbon fraction of virgin olive oil, Journal of the American Oil Chemists’ Society, 71, 285–291. Lee, J.H., Acoh, C.C., Himmelsbach, D.S. and Lee, K-T. (2008) Preparation of interesterified plastic fats from fats and oils free of trans fatty acids, Journal of Agricultural Food Chemistry, 56, 4039–4046. Lercker, G., Frega, N., Bocci, F. and Mozzon, M. (1999) Volatile constituents and oxidative stability of virgin olive oils. Influence of the kneading of olive paste, Grasas Aceites, 50, 26–29. Litridou, M., Linssen, J., Schols, H. et al. (1997) Phenolic compounds of virgin olive oils: Fractionation by solid phase extraction and antioxidant activity assessment, Journal of the Science of Food and Agriculture, 74, 169–174. Lo Curto, S., Duco, L., Mondello, L., Errante, G. and Russo, M.T. (2001) Variation in tocopherol content in Italian virgin olive oils, Italian Journal of Food Science, 13(2), 221–226. Manzi, P., Panfili, G., Esti, M. and Pizzoferrato, L. (1998) Natural antioxidants in the unsaponifiable fraction of virgin olive oils from different cultivars, Journal of the Science of Food and Agriculture, 77, 115–120. Mateos, R., Espartero, J.L., Trujillo, M. et al. (2001) Determination of phenols, flavones and lignans in virgin olive oils by SPE and HPLC with diode array ultraviolet detection, Journal of Agricultural Food Chemistry, 49, 2185–2192. Minguez-Mosquera, I., Gandul-Rojas, B., Garrido-Fernadez, J. and Gallardo-Guerrero, L. (1990) Pigments present in virgin olive oil, Journal of the American Oil Chemists’ Society, 67, 192–196. Monteleone, E., Caporale, G., Carlucci, A. and Pagliarini, E. (1998) Optimization of extra virgin olive oil quality, Journal of the Science of Food and Agriculture, 1998, 77, 31–37. Morales, M.T. and Aparicio, R. (1999) Effect of extraction conditions on sensory quality of virgin olive oil, Journal of the American Oil Chemists’ Society, 76, 295–300. Morales, M.T. and Aparicio, R. (2005) Comparative study of virgin olive oil sensory defects, Food Chemistry, 91, 293–301. Morales, M.T. and Tsimidou, M. (2000) The role of volatile compounds and polyphenols in olive oil sensory quality, in Handbook of Olive Oil (eds J. Harwood and R. Aparicio), Aspen Publishers, Gaithersburg, MD, pp. 393–438. Moret, S., Piani, B., Bortolomeazzi, R. and Contel, L.S. (1997) HPLC determination of polycyclic aromatic hydrocarbons in olive oil, Zeitschrift Lebensmittel – Unters Forschung, 205, 116–120. Petrakis, C. (2006) Olive oil extraction, in Olive Oil, Chemistry and Technology (ed. D. Boskou), AOCS Press, Champaign, IL, pp. 191–224. Pokorny, J. and Korczak, J. (2001) Preparation of natural antioxidants, in Antioxidants in Food (eds J. Pokorny, N. Yanishlieva and M. Gordon), CRC Press, Boca Raton, FL, pp. 311–330. Psomiadou, E. and Tsimidou, M. (1998) Simultaneous HPLC determination of tocopherols, carotenoids and chlorophylls for monitoring their affect on virgin olive oil oxidation, Journal of Agricultural Food Chemistry, 46, 5132–5138. Psomiadou, E. and Tsimidou, M. (1999) On the role of squalene in olive oil stability, Journal of Agricultural Food Chemistry, 47, 4025–4032. Psomiadou, E. and Tsimidou, M. (2001) Pigments in Greek virgin olive oils: Occurrence and levels, Journal of the Science of Food and Agriculture, 81, 640–647. Psomiadou, E., Tsimidou, M. and Boskou, D. (2000) α-Tocopherol content of Greek virgin olive oils, Journal of Agricultural Food Chemistry, 48, 1770–1775. Ranalli, A., Contento, S., Schiavone, C. and Simone, N. (2001) Malaxing temperature affects volatile and phenol composition as well as other analytical features of virgin olive oil, European Journal of Lipid Science Technology, 103, 228–238. Rao, C.V., Newmark, H.L. and Reddy, B.S. (1998) Chemopreventive effect of squalene in colon cancer, Carcinogenesis, 19, 287–290. Reiners, J. and Grosch, W. (1998) Odorants of virgin olive oils with different flavour profiles, Journal of Agricultural Food Chemistry, 46, 2754–2763. Reiter, B. and Lorbeer, E. (2001) Analysis of the wax ester fraction of olive oil and sunflower oil by gas chromatography–mass spectroscopy, Journal of the American Oil Chemists’ Society, 78, 881–888. Ruiz-Mendez, M.V. and Dobarganes, C. (1999) Olive oil and olive pomace oil refining, OCL (Oleagineux, Corps gras, Lipides), 6, 56–60.

Gunstone_c09.indd 270

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Olive Oil

271

Santinelli, F., Damiani, P. and Christie, W.W. (1992) The triacylglycerol structure of olive oil determined by silver ion high performance liquid chromatography in combination with stereospecific analysis, Journal of the American Oil Chemists’ Society, 69, 552–557. Scano, P., Casu, M., Lai, A. et al. (1999) Recognition and quantitation of cis-vaccenic and eicosenoic fatty acids in olive oils by C-13-Nuclear Magnetic Resonance spectroscopy, Lipids, 34, 757–759. Servili, M., Taticchi, A., Esposto, S. et al. (2008) Influence of the decrease in oxygen during malaxation of olive paste on the composition of volatiles and phenolic compounds in virgin olive oil, Journal of Agricultural Food Chemistry, 56, 10048–10055. Severge, A. (1983) Difficulties in physical refining of olive oil due to the presence of triterpene oleanolic acid, Journal of the American Oil Chemists’ Society, 60, 584–587. Smith, TJ., Yang, G.Y., Seril, D.N., Liao, J. and Kim, S. (1998) Inhibition of 4-(methylnitrosaminol)-1(3-pyridyl)-1-butanone induced lung tumorogenesis by dietary olive oil squalene, Carcinogenesis, 19, 703–706. Stark, A.H. and Madar, Z. (2002) Olive oil as as a functional food, Nutrition Review, 60, 170–176. Tiscornia, E., Fiorina, N. and Evangelisti, F. (1982) Chemical composition of olive oil and variations induced by refining, Rivista Italiana delle Sostanze Grasse, 59, 519–555. Trichopoulos, D. and Trichopoulou, A. (2009) Traditional Mediterranean diet and health, in Olive Oil: Minor Constituents and Health (ed. D. Boskou), CRC Press, Boca Raton, FL, pp. 7–11. Trichopoulou, A. and Vasilopoulou, E. (2000) Mediterranean diet and longevity, British Journal of Nutrition, 84, suppl. 2, S205–S209. Tsimidou, M. and Boskou, D. (1994) Antioxidant activity of essential oils from the plants of the Lamiaceae family, in Herbs, Spices and Edible Fungi (ed. G. Charalambous), Elsevier, Amsterdam, pp. 273–284. Tsimidou, M., Papadopoulos, G. and Boskou, D. (1992) Phenolic compounds and stability of virgin olive oil, Part 1, Food Chemistry, 45, 141–144. Tsimidou, M., Georgiou, A., Koidis, A. and Boskou, D. (2004) Loss of stability of veiled (cloudy) virgin olive oil in storage, Food Chemistry, 93, 377–383. Tynek, M. and Ledochowska, A. (2005).Structural triacylglycerols containing behenic acid preparation and properties, Journal of Food Lipids, 12, 77–82. Varela, G. (1992) Some effect of deep frying on dietary fat intake, Nutrition Reviews, 50, 256–262. Vichi, S., Guadayol, J.M., Caixach, J., Lopez-Tamames, E. and Buxaderas, S. (2006) Monoterpene ans sesquiterpene hydrocarbons in virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass specytometry, Journal of Chromatography A, 1125, 117–123. Visioli, F. (2000) Antioxidants in Mediterranenan diets, in Mediterranean Diets (eds A. Simopoulos and F. Visioli), Karger, Basel, pp. 43–53. Vlahof, G. (2006) Determination of the 1,3-and 2-positional distribution of fatty acids in olive oil triacylglycerols by nuclear ¹³C magnetic resonance spectroscopy, Journal of the Official Association of Analytical Chemists International, 89, 1071–1076. Vural, H.P., Havidpour, I. and Ozbas, O. (2004) Effects of interesterified oils and sugarbeet fiber on the quality of frankfurters, Meat Science, 67, 65–72.

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10 Corn Oil Robert A. Moreau

10.1 10.1.1

COMPOSITION OF CORN OIL Introduction: The corn oil industry

Unlike most other vegetable oils, corn oil (maize oil) is obtained from seeds (kernels) that contain only 3–5% oil. Almost all commercial corn oil is obtained by pressing and/or hexane extraction of the oil-rich corn germ (embryo) portion of the corn kernel, and corn oil could accurately be called ‘corn germ oil’ (Moreau 2005). Obtaining oil directly from the kernels is technically possible, but ‘corn kernel oil’ is more costly to produce (due to the low levels of oil in the kernels). Although they have not been produced commercially, ‘corn kernel oil’ and ‘corn fiber oil’ have been produced on a laboratory scale (Moreau et al. 2009c) and both have unique composition and potential uses as nutraceuticals and functional foods (described in a later section of this chapter). Because corn kernels contain high levels of starch (60–75%), a process, ‘wet milling’, was developed to efficiently isolate pure starch from corn kernels. The first corn wet mill in the US started producing cornstarch in 1842 and by 1860 several corn wet mills were in operation in the US (Anonymous 2006). During industrial wet milling, the non-starch portions of the kernel are separated into four fractions: (i) steepwater solubles (∼7%); (ii) fiber (∼10%); (iii) corn gluten meal (∼6%); and (iv) germ (∼7%) (Moreau et al. 1999b). The steepwater solubles and fiber fractions are blended together to produce an animal feed called ‘corn gluten feed’, which contains about 21% protein and 60–70% fiber. The high fiber content restricts its use mainly to ruminant feeds. Corn gluten meal contains about 60% protein and low fiber (<1%), and is a premium feed for non-ruminants (poultry and swine). Corn germ is rich in oil (20–50%) and is the source of all commercial corn oil; like ‘wheat germ oil’, corn oil could more accurately be called ‘corn germ oil’. As noted in Chapter 1, about 2.4 million tonnes of corn oil was produced worldwide in 2008/09, with about half from the USA, followed by China in second place. Compared to the nine vegetable oils listed in Table 1.7, the production level of corn oil is slightly lower than the ninth oil (olive oil – 2.97 million tonnes in 2008/09, as noted in Table 1.7). Unlike oilseeds, where solvent extraction alone can be used to obtain oils, extraction after flaking of wet-milled corn germ produces a substantial amount of ‘fines’ that interfere with the efficiency of the solvent-extraction process. Traditionally oil is removed from the wet-milled germ using a conditioning (heating) process, followed by mechanical expelling Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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(‘pre-press’) and then hexane extraction. Extrusion can be employed as a means of germ preparation for solvent extraction, producing a crude corn oil of high quality and high yield (Maza 2001). Others have demonstrated that corn germ can be effectively extracted by supercritical fluid extraction (Ronyai et al. 1998). Within the US, most of the crude and refined corn oil is currently produced by three wet-milling companies (Archer Daniels Midland, Cargill, and Corn Products International) (Anonymous 2009a). It was estimated that in 2006, about 95% of commercial corn oil in the US was from wet-milled germ and the remainder from dry-milled germ (Anonymous 2006). Oil is usually obtained from dry-milled corn germ by full press (via an expeller). List et al. (1984) compared some of the chemical components in corn oil from wet-milled germ versus dry-milled germ and reported lower levels of free fatty acids, lower levels of phosphorous, and higher levels of tocopherols in the latter. Some published results compared the optimal conditions for the bench-scale pressing of dry-milled corn germ and wet-milled corn germ (Moreau et al. 2005; Dickey et al. 2007). Microscopic evidence was presented that cooking corn germ in a conventional oven or a microwave causes destruction of the oil body membrane (spherosome) and causes the oil in the oil bodies to coalesce (Dickey et al. 2007). Although several ‘high-oil’ corn hybrids are available, most of the crop has been used for animal feed (with the fat providing more calories) and little or none has been wet milled to obtain starch, corn oil, and other products. A process for extracting oil from the flaked kernels of high-oil (>8%) corn hybrids was patented (Ulrich and Anderson 2001). An interesting aspect of the proprietary process is that it uses the popular flaking and extraction machinery that is usually employed for soybean oil processing. Although almost all of the commercial corn oil is currently obtained by a combination of pressing and/or hexane extraction, new alternative corn germ extraction methods are being developed. Because of its toxicity and flammability and the increasing regulatory safeguards and costs associated with handling hexane, research is underway to develop alternatives to hexane extraction. One promising alternative is aqueous enzymatic extraction for corn germ to produce corn oil. An aqueous enzymatic corn oil extraction was first reported by Yugoslavian researchers (Bocevska et al. 1993; Karlovic et al. 1994). Our laboratory has also continued research in this area, utilizing newer enzymes developed for the food industry and more economical enzymes developed for the cellulosic ethanol industry (Moreau et al. 2004, 2009a; Dickey et al. 2009).

10.1.2

Common corn oil refining steps and effects on oil composition

The major component of crude corn germ oil is triacylglycerols (TAG), but crude (unrefined) corn oil also contains other minor non-polar and polar lipid components (Table 10.1). Free fatty acids, pigments, volatiles, phospholipids, and waxes are the major undesirable components in crude corn oil and these are removed by several refining steps. In corn oil processing, most companies remove free fatty acids by alkali refining, which involves adding base and neutralizing (and sequestering) the free fatty acid soaps (and phospholipids) into a by-product called ‘soapstocks’ (Strecker et al. 1996). Alternatively, free fatty acids can be removed by a process called ‘physical refining’ or ‘steam refining’, which involves treating the oil at high temperature and vacuum to volatilize the free fatty acids. Physical refining begins by removing phospholipids by a water-degumming step (Antoniassi et al. 1998). Whereas soybean oil processing is usually preceded by water degumming, during corn oil processing degumming is usually not included if corn oil is going to be processed via alkali refining. However, degumming is necessary if physical refining is used. Failure to

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Corn Oil Table 10.1 Oil

Germ oil (crude) Germ oil (crude) Germ oil (RBD) Kernel oil (crude) Fiber oil (crude) Fiber oil (crude)

Polar and nonpolar lipid classes in corn germ oil, corn kernel oil, and corn fiber oil.

TAG FFA St:E

St

FPE

Wt %

Total lipid

1.2*

96.8 0.31 0.47 98.9 0.03 nr

95.6 1.7

nr

275

nr

nr

tocols

GL PL

nr

0.06

nr

0.48

0.01

0.17

nr

1.1*

nr

0.05

0

0.76–3.09 0.54–1.28 0.047–0.839 0.023-0.127 nr

84.5 2.11 5.61

1.17

4.11

0.76

nr

nr

1.9–4.3

6.5–9.5

nr

nr

nr

2.9–9.2

Reference

1.2 Orthoefer and Sinram (1987) nr Moreau et al. (1999b) 0 Orthoefer and Sinram (1987) nr Moreau et al. (2001b) nr Moreau et al. (1999b) nr Singh et al. (2000)

Note: * Value is after saponification, meaning that it is the sum of St and St:E. Key: GL = glycolipids FFA = free fatty acids FPE = phytosteryl ferulate esters nr = not reported PL = phospholipids RBD = refined, bleached, and deodorized oil St = free phytosterols St:E = phytosteryl fatty acyl esters TAG = triacylglycerols tocols = tocopherols and tocotrienols

adequately remove the phospholipids (by either alkali refining or degumming) results in a corn oil that will form dark colors and off flavors when heated (Anonymous 2006). After a subsequent bleaching step, the next step in physical refining is steam distillation at high temperature and very low pressure (vacuum), which volatizes the free fatty acids. Leibovitz and Ruckenstein (1983) reported higher yields of oil with physical refining than with alkali refining. Others have noted that oils that contain phytosteryl esters (especially phytosterol ferulates, such as those found in corn fiber oil and rice bran oil) are extensively hydrolyzed during conventional alkali refining, but remain relatively intact during physical refining (R. Nicolosi, personal communication). Other strategies for removing free fatty acids from crude oil have included liquid–liquid extraction and a new method involving solvent extraction in a perforated rotating disk (Pina and Meirelles 2000). Deodorization of corn oil involves treatment at high temperature (>200 °C) and low vacuum (∼2–10mm Hg), which removes undesirable odors and flavor components (Orthoefer and Sinram 1987). Unfortunately, the deodorization process also removes some phytosterols and tocopherols. The by-product of deodorization, the ‘deodorizer distillate’, has been used as a major industrial source of tocopherols and phytosterols (used as precursors in the synthesis of some steroid pharmaceuticals and sometimes converted to phytostanols via hydrogenation). A study compared the levels of tocopherols and phytosterols in industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower, and soybean oils (Verleyen et al. 2001). Pigments are usually removed by treating the oil with acid-activated bleaching clay (Strecker et al. 1996). Another refining step that ensures (physical) stability of oils at low temperature is dewaxing or ‘winterization’, which involves cooling the oil to 5–10 °C, and removing precipitates via filtration (Leibovitz and Ruckenstein 1983).

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Key: Int = international hybrids nr = not reported RBD = refined, bleached, and deodorized oil US = US hybrids 16:0 = palmitic acid 18:0 = stearic acid 18:1 = oleic acid 18:2 = linoleic acid 18:3 = linolenic acid 20:0 = arachidic acid

11.0 ± 0.5 9.2–16.5 10.9 11.0 ± 0.6 12.9 ± 1.4 9.2–11.8 13.8 ± 0 10.72 ± 0.02 11.46 ± 0.02 12.29 ± 0.03

16:0 1.8 ± 0.3 0–3.3 1.8 1.7 ± 0.3 2.6 ± 0.6 1.1–1.7 1.7 ± 0 1.85 ± 0.01 1.83 ± 0 2.34 ± 0

18:0 0.2 ± 0.2 0.3–0.7 nr nr nr 0.3–0.5 0.3 ± 0 0.45 ± 0 0.45 ± 0.01 0.61 ± 0

20:0 25.3 ± 0.6 20–42.2 24.2 25.8 ± 0.9 33.1 ± 2.5 19.5–30.4 23.8 ± 0.1 27.65 ± 0.02 24.66 ± 0.03 22.33 ± 0.02

18:1

Fatty acids in refined corn germ oil and corn fiber oil (mol% of total fatty acids).

Germ oil (RBD) US Germ oil (RBD) US Germ oil (RBD) US Germ oil (RBD) US Germ oil (RBD) Int Kernel oil (crude) Int Corn fiber oil (crude) Corn germ oil (RBD) Corn kernel oil (crude) Corn fiber oil (crude)

Oil

Table 10.2

60.1 ± 1.0 39.4–65.6 58.0 59.8 ± 1.2 48.8 ± 2.4 53.0–65.3 56.4 ± 0.1 57.26 ± 0.04 57.23 ± 0.22 54.55 ± 0.003

18:2 1.1 ± 0.3 0.5–1.5 0.7 1.1 ± 0.4 1.4 ± 0.4 1.2–2.1 2.6 ± 0 1.22 ± 0.01 1.68 ± 0.03 4.20 ± 0.01

18:3

Orthoefer and Sinram (1987) Firestone (1999) Anonymous (2009c) Strecker et al. (1996) Strecker et al. (1996) Goffman and Böhme (2001) Moreau et al. (2000) Moreau et al. (2009b) Moreau et al. (2009b) Moreau et al. (2009b)

Reference

Corn Oil

10.1.3

277

The composition of crude corn oils – comparison of corn germ oil, corn kernel oil, and corn fiber oil

Although all current commercial corn oil is produced from corn germ oil, considerable research has been devoted to the study of extracting the entire corn kernel to produce ‘corn kernel oil’ and extracting corn fiber (a by-product of wet milling) to obtain ‘corn fiber oil’ (Table 10.1). The levels of total phytosterols (the sum of free phytosterols and phytosteryl fatty acyl esters) in corn germ oil average a little more than 1%, which is higher than the levels found in most other common vegetable oils (Orthoefer and Sinram 1987). Some of these phytosterols are removed during refining, but even after refining, the levels of phytosterols in commercial corn oil are about 1% (Table 10.1). Hojilla-Evangelista et al. (1992) at Iowa State University developed a process, the ‘sequential extraction process’ (SEP), which uses anhydrous ethanol to extract oil from whole flaked corn kernels, and then employs additional steps to fractionate proteins and starch. Although analyses of their SEP oil (a type of corn kernel oil) have not been published, our lab has published some data on the composition of hexane-extracted corn kernel oil, and we have found (Moreau et al. 2001b) that it contains higher levels of the three phytosteryl lipid classes (free phytosterols, phytosteryl fatty acyl esters, and phytosteryl ferulates) than those in germ oil (Table 10.1). We also recently reported some detailed analyses of corn kernel oil obtained by the ethanol extraction of ground corn (Moreau and Hicks 2005, 2006; Moreau et al. 2003). The levels of tocotrienols were much higher in corn kernel oil than in hexane-extracted corn germ oil (Moreau and Hicks 2006). The yellow pigments in yellow corn are mostly lutein and zeaxanthin. The levels of lutein and zeaxanthin (types of oxygenated carotenoid called xanthophylls) are about 200-fold higher in ethanol-extracted corn kernel oil than in corn germ oil (Moreau et al. 2007). Also, ethanolextracted corn kernel oil was found to contain about 1% polyamine conjugates (diferuloylputrescine and p-coumaroyl feruloylputrescine), which are undetectable in corn germ oil (Moreau et al. 2001a). It has been suggested that polyamine conjugates may have protective functions in the corn kernel, but the only biological activity that has been reported is their inhibition of aflatoxin biosynthesis (Mellon and Moreau 2004). Moreau et al. (1996, 1998) reported that a unique oil, very rich in the two phytosteryl esters (their chemical properties will be described in a later section), could be extracted from corn fiber. Corn fiber oil contains the highest levels of natural phytosterols and phytostanols (see Section 10.1.6) of any known plant extract (Hicks and Moreau 2001; Moreau et al. 2009b). Corn fiber (a wet-milling fraction) is comprised of pericarp, endosperm fiber, and aleurone cells, whereas corn bran (from dry milling) is mostly pericarp (Singh et al. 2001). Most of the phytosterols in corn fiber appear to be localized in the aleurone cells (Moreau et al. 2000; Singh et al. 2001).

10.1.4

Fatty acid composition of corn triacylglycerols

Edible oils are often compared by performing alkaline hydrolysis (saponification) of the triacylglycerols and comparing the fatty acid profiles. In the 1950s and 1960s a marketing slogan for corn oil was that it was ‘high in polyunsaturates’, mostly attributed to its high levels of linoleic acid, an essential fatty acid (one that is not synthesized by humans and must be obtained in the diet), abbreviated as 18:2 (Table 10.2). Another desirable feature of corn oil is that it contains relatively low levels (<15%) of saturated fatty acids and very low levels of linolenic acid (18:3), which is especially susceptible to oxidation, leading to rancidity.

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Although the levels of linoleic acid in US corn oil average about 60%, it has been noted that its levels in corn oil produced outside of the US are closer to 50%, with most of the difference being accounted for by higher amounts of oleic acid (Strecker et al. 1996). Several studies have reported that when the same corn hybrids are grown in multiple locations, the corn oil produced from plants grown in cooler regions had higher levels of linoleic acid (White and Weber 2003). It was also noted that the average levels of linoleic acid in US commercial corn oil increased from 57.8% to 62.0% between 1974 and 1986 (White and Weber 2003). In response to the current demand for high-monounsaturate vegetable oils, recent efforts have been devoted to developing corn hybrids that produce corn germ oils with high levels of oleic acid. A ‘high oil – high oleic acid’ corn hybrid was recently patented (Leto and Ulrich 2001). In addition to the extensive literature on the fatty acid composition of crude and refined corn germ oil, there also have been reports about the fatty acid composition of crude corn kernel oil (Goffman and Böhme 2001) and crude corn fiber oil (Moreau et al. 2009b); the fatty acid composition of both are very similar to that of corn germ oil (Table 10.2).

10.1.5

Triacylglycerol molecular species

Reversed-phase HPLC techniques have been developed to quantitatively analyze the triacylglycerol molecular species of oils of plant and animal origin. Reports of the triacylglycerol molecular species of refined corn oil indicated the successful identification of 19 to 27 individual molecular species, with oleate-linoleate-linoleate and linoleate-linoleatelinoleate being the two most abundant molecular species (Table 10.3). Silver ion HPLC was also used to quantitatively analyze the triacylglycerols in corn oil (Neff et al. 1994). The method separated the triacylglycerols into eleven fractions, with the largest two fractions having five and six double bonds with the structures dienoic-dienoic-monoenoic and dienoic-dienoic-dienoic (confirming the two most abundant molecular species identified in reversed-phase HPLC).

10.1.6

Unsaponifiables and phytosterols

Commercial corn oil has been recognized as containing the highest levels of unsaponifiables (1.3–2.3%) of all the commercial vegetable oils (Strecker et al. 1996). The three main chemical components in the unsaponifiable fraction of corn oil are phytosterols, tocopherols, and squalene. Corn germ oil contains two phytosteryl lipid classes, free phytosterols and phytosteryl fatty acyl esters (Table 10.1). Phytosterols have been recognized as one of the 12 most important classes of phytonutrients (Fahey et al. 1999), mainly due to their cholesterollowering properties (Moreau et al. 2002). Most structural identification of phytosterols in vegetable oils has been conducted by saponifying (hydrolyzing with base) the oil and measuring the resulting free phytosterols, usually by GLC (Table 10.4). The major phytosterols in corn germ oil are β-sitosterol > campesterol > stigmasterol (Table 10.4). Snyder et al. (1999) developed a method to concentrate and fractionate the phytosterols in corn germ oil. Examination of the total phytosterols in corn fiber oil revealed that the major phytosterol was sitostanol (Table 10.4). Sitostanol is a phytostanol (meaning that it is completely saturated, and thereby contains no carbon–carbon double bonds, whereas phytosterols typically contain at least one unsaturated center). Natural sitostanol is rare in plants, and the only reports of its presence in greater than trace amounts have been

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Corn Oil Table 10.3

Triacylglycerol molecular species in refined corn germ oil.

TAG molecular species LLO LLL LLP OOL PLO PPL OOP LLS LOS OOO PPO PLS LLLn LnLO OOS POS PLnL PPP OOLn PLnO PPS SSL LnLS SSO PPLn SSP SSS

279

Area %*

Area %**

Area %§

20.0 17.8 13.7 11.8 10.9 2.5 3.5 2.6 1.8 4.4 1.6 0.8 0.9 2.2 0.6 0.2 0.4 0.0 1.1 0.0 0.4 0.0 0.0 0.0 0.0 0.0 0.0

21.5 25.4 14.7 10.7 10.0 2.5 2.9 2.2 1.8 2.8 0.9 0.8 1.2 0.9 0.6 0.3 0.5 0.0 0.1 0.1 0.0 0.1 0.1 0.0 0.0 0.0 0.0

23.0 22.6 15.2 10.6 10.4 1.7 2.4 1.8 1.3 3.2 0.4 0.4 0.8 2.3 0.5 0.3 0.5 0.1 1.0 0.5 0.1 0.3 0.0 0.0 0.2 0.1 0.1

Sources: * from Strecker et al. (1990); ** HPLC-mass spec. values from Byrdwell et al. (2001); detector values from Byrdwell et al. (2001). Key: L = linoleic acid Ln = linolenic acid O = oleic acid P = palmitic acid S = stearic acid

§

HPLD-flame ionization

in grains (Moreau et al. 2009c). The sitostanol used in commercial sitostanol-ester margarines is produced by catalytic hydrogenation. Sitostanol is the product of catalytic hydrogenation of the two most common plant phytosterols, β-sitosterol and stigmasterol (Hicks and Moreau 2001). Our lab recently reported that most of the sitostanol in corn fiber oil is found as the phytostanol ester of ferulic acid, and most of the sitostanol in corn fiber (and in corn kernels) is found in the aleurone layer (Table 10.4). In some grains the aleurone layer is multiple cell layers, but in corn it is comprised of a single layer of (phytosterol-rich) living cells (Singh et al. 2001).

10.1.7

Tocopherols and tocotrienols

Corn oil has long been recognized as a rich source of tocopherols, with γ-tocopherol being the most abundant tocopherol, followed by α-tocopherol and then δ-tocopherol (Table 10.5). Among the tocopherols, α-tocopherol has received the most attention because of its vitamin

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Table 10.4 Total sterols (mg/100 g oil) in corn oil samples after alkaline hydrolysis. Corn kernel oil was refined, bleached, and deodorized (RBD) by conventional processes. Corn fiber oil was refined, bleached, and deodorized (RBD) using gentle processes. Commercial corn germ oil (RBD) was purchased locally. Values presented are the mean of two analyses for each sample.

Campesterol Campestanol Stigmasterol Sitosterol Sitostanol Δ5-Avenasterol Stigmasta-5,24 (25)-dienol Gramisterol + α-amyrin Cycloartenol Δ7-stigmastenol Δ7-Avenasterol 24-Methylene cycloartanol Citrostadienol Total

Corn kernel oil

Corn fiber oil

Corn germ oil

135 74 46 510 184 38 27 12 44 10 20 11 1109

594 1182 142 1897 2964 375 65 92 249 144 121 116 7939

151 13 54 503 30 29 5 9 18 5 15 8 840

Source: Moreau et al. (2009b).

E activity, but the other isomers also are known to have valuable antioxidant properties. Some evidence suggests that γ-tocopherol may be superior to α-tocopherol in preventing the oxidation of low-density lipoproteins and delaying thrombus formation (Saldeen et al. 1999). Wang et al. (1998) reported significant levels of tocotrienols (the most abundant was γ-tocotrienol followed by α-tocotrienol) in corn kernel oil, and saponfication of the kernels caused about a twofold increase in the levels of extractable tocotrienols and γ-tocopherol. It is currently believed that, in addition to their valuable antioxidant properties, tocotrienols also possess cholesterol-lowering properties, probably associated with their ability to inhibit cholesterol biosynthesis (Parker et al. 1993). We reported high levels of γ-tocopherol in corn fiber oil (about 0.36 wt %), noting that heat pretreatment of the corn fiber (prior to extraction) caused a nearly tenfold increase in the levels of extractable γ-tocopherol (increasing its concentration in the oil to about 3%; Moreau et al. 1999a). However, in a later study, using better analytical methods, we found that the levels of γ-tocopherol were unchanged or diminished by heat pretreatment and the peak that we erroneously identified as γ-tocopherol in our earlier report was probably a triacylglycerol hydroperoxide (Moreau and Hicks 2006).

10.1.8

Carotenoids

High levels of carotenoids have been reported in corn kernels, with most (74–86%) being localized in the endosperm, 2–4% in the germ, and 1% in the bran (Weber 1987). The most abundant carotenoids in corn kernels are lutein and zeaxanthin, and consuming foods that are rich in these carotenoids may decrease the risk of age-related macular degeneration (Sommerburg et al. 1998). The levels of carotenoids in commercial corn oil are relatively low, partly due to their low concentrations in the germ and partly due to their removal during the bleaching step of processing. As reported earlier in this chapter, the levels of lutein and zeaxanthin (oxygenated carotenoids, generally called xanthophylls) are about 200-fold higher in ethanol-extracted corn kernel oil than in hexane-extracted corn germ oil (Moreau et al. 2007). Also, two tablespoonfuls (30 g) of ethanol extracted corn kernel oil would provide about 6 mg

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0 0 0

48

166.0 ± 1.4 425.6 ± 11.0 0

Kernel, crude (saponified) Corn germ oil (crude) Corn kernel oil (crude) Corn fiber/ oil (crude)

Key: nr = not recorded RBD = refined, bleached and deodorized

nr

23–573 67–276

Germ, RBD Kernel, crude

0–356 0–20

18

134

Germ, RBD

0

191

993.3 ± 12.7 1034.7 ± 5.2 79.0 ± 19.5

532

268–2468 583–1048

412

493

133.9 ± 3.7 112.4 ± 0.8 35.7 ± 1.2

nr

23–75 12–71

39

118

mg/kg oil

0 173.6 ± 0.4 15.3 ± 2.1

124

0–239 46–90

nr

nr

nr

0–20 nr

nr

nr

Moreau et al. (2005) Moreau et al. (2005) Moreau and Hicks (2006)

Strecker et al. (1996) Strecker et al. (1996) Firestone (1999) Goffman and Böhme (2001) Wang et al. (1998)

d-tocotrienol Reference

67.7 ± 0.5 0 324.2 ± 0.5 49.5 ± 2.8 378.3 ± 104.2 70.0 ± 2.7

197

0–450 60–133

nr

23

a-tocopherol b-tocopherol g-tocopherol d-tocopherol a-tocotreinol g-tocotrienol

Tocopherols and tocotrienols in corn germ oil.

Germ, crude

Oil

Table 10.5

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Vegetable Oils in Food Technology

of lutein + zeaxanthin, which is the amount that has been identified to slow the progression of age-related macular degeneration (Moreau et al. 2007). Although it is generally believed that carotenoids function as antioxidants, there is some evidence that, under certain conditions, carotenoids in vegetable oils and certain other food matrices may serve as pro-oxidants, especially at higher concentrations (Subagio and Morita 2001).

10.1.9

Trans fatty acids

The common unsaturated fatty acids in all vegetable oils exist only in the cis configuration. During the production of margarine, spreads, and shortenings via catalytic hydrogenation, carbon–carbon double bonds are converted to carbon–carbon single bonds, but the process also catalyzes the production (isomerization) of some trans fatty acids (Enig et al. 1983). There is considerable variation in the levels of cis and trans fatty acids in commercial corn oil margarines and spreads (Table 10.6), with the levels of trans fatty acids ranging from a low of 2.79 to a high of 20.13 grams of total trans fatty acids per 100 grams of product. Concerns about possible association between trans fatty acids and certain types of cancer (Ip 1997) have caused some groups to seek to reduce or eliminate the levels of trans fatty acids in foods, either by using butter, or by using processes other than hydrogenation to raise the melting point of corn oil and thereby produce new types of margarines and spreads (see Section 10.3). With the controversy associated with trans fatty acids produced during chemical hydrogenation, some individuals may not realize that a natural group of trans fatty acids, ‘conjugated linoleic acid’ or CLA (the trans double bond is produced by anaerobic rumen bacteria via ‘biohydrogenation’), has been discovered in dairy and beef products. Current international research indicates that CLA may have several health-promoting properties (Lawson et al. 2001). The discovery of these health-promoting properties of some trans fatty acids (CLA) may provide an incentive to undertake an objective reevaluation of the risks of the trans fatty acids in margarines from corn and other vegetable oils. In the USA since 2006, the Food and Drug Administration (FDA) has required food manufacturers to list trans fat (i.e., trans fatty acids) on Nutrition Facts and some Supplement Facts panels (FDA 2010), unless the product contains <0.5 g of trans fat per serving. In response to this new trans fat labeling requirement, most food manufacturers have eliminated or reduced the amount of trans fatty acids in most processed foods. Items that contain less than 0.5 g of trans fat per serving can be declared as 0 g.

10.2 10.2.1

PROPERTIES OF CORN OIL Chemical and physical properties

The basic properties of corn oil include its pleasing flavor, high levels of polyunsaturated (essential) fatty acids, low levels of saturated fatty acids, and low levels of linolenic acid (Anonymous 2006). The other main physical and chemical properties of corn oil are summarized in Table 10.7.

10.2.2

Stability

Because frying is a major use of corn oil, numerous studies have compared the thermal stability of corn oil and other vegetable oils during frying (Strecker et al. 1996; Gertz et al. 2000). One frying study demonstrated that when compared to canola and soybean oils, corn

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9 3.9 2

82.09

38.8

19.5

Key: C = cis T = trans For other abbreviations see Table 10.2.

8.1

10.9

16:0

80

100

% Fat

0

0

0

0

0

16:1

0.8

2.4

5.2

6

1.8

18:0

4.8

9.4

17.0

17.5

24.2

18:1

C

2.7

5.2

19.6

19.7

0

18:1

T

Cis and trans fatty acids in corn oil and corn oil margarines.

Corn oil margarine (stick) Corn oil margarine (stick) Corn oil spread, light (tub) Corn oil spread, extra light (tub)

Corn oil

Oil

Table 10.6

18:2

CT

7.8

15

25.7

20.8

58

0.1

0.5

0.5

0.7

0

g/100 g product

18:2

CC

0

0

0

0

0

18:2

TT

0.2

0.3

0.5

2.2

0.7

18:3

CCC

0

0.2

0.2

0.26

0

20:0

0

0.1

0.2

0

0

20:1

2.8

5.7

20.1

19.7

0

Total trans

Anonymous (2009c) Anonymous (2009c) Exler et al. (2001) Exler et al. (2001) Exler et al. (2001)

Reference

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Vegetable Oils in Food Technology Table 10.7

Physical and chemical characteristics of corn oil.

Property

Value

Iodine value Saponification number Free fatty acids after RBD Color Lovibond Gardner Refractive index 20 °C 26 °C Specific gravity 25/25 °C Viscosity 40 °C 60 °C Dielectric constant 26 °C Surface tension, 25 °C Interfacial tension, k H2O at 24 °C Thermal conductivity at 130 °C Unsaponifiables Weight per gallon at 60 °C Melting point Smoke point Flash point Fire point Cloud point

127–133* 187–193* 0.05% max** 3.0 red max** 6 max** 1.4753* 1.4726* 0.91875* 30.80 cP* 18.15 cP* 3.954* 34.80 dyn/cm* 18.60 dyn/cm* 4.2017 × 10−5 J/s/cm2/°C* 1–2%§ 7.7 pounds† −11 to −8 °C† 230 to 238 °C† 332 to 338 °C† 366 to 371 °C† −14 to −11 °C†

Sources: * Strecker et al. (1996); ** Anonymous (2009a); § Firestone (1999); † Anonymous (2006).

oil produced the lowest levels of oxidation products and retained the highest levels of tocopherols, during five days at continuous frying temperatures (Strecker et al. 1990). Another oxidative stability study revealed that corn oil hybrids with higher levels of saturated fatty acids were more stable than traditional corn oils (Shen et al. 1999). An optical assessment study was developed, providing a parameter for assessing the oxidative stability of corn oil during frying (Sebben et al. 1998).

10.2.3

Nutritional properties

Numerous clinical studies (>30) during the last 40 years have supported the hypothesis that corn oil has cholesterol-lowering properties (Strecker et al. 1996). This observation of corn oil’s superiority over other vegetable oils in its cholesterol-lowering properties has been termed the ‘maize oil aberration’ (Meijer 1999). In the 1950s, experts believed that the high levels of polyunsaturated fatty acids in corn oil were the reason for its cholesterol-lowering properties (Anonymous 2006). Others have suggested that because corn oil contains the highest levels of unsaponifiables and phytosterols of any common vegetable oil, these components cause the cholesterol-lowering effect (Howell et al. 1998). A recent study comparing corn oil with cottonseed oil found that, although corn oil contained more unsaponifiables, cottonseed oil was more effective at lowering total serum cholesterol, which the authors attributed to the specific types of unsaponifiables in cottonseed oil (Radcliffe et al. 2001). Lichtenstein et al. (1993) reported that hydrogenation of corn oil reduces its cholesterollowering properties in humans.

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Some clinical studies with phytosteryl and phytostanyl ester products have indicated that a person must ingest 1.6 to 3.3 g of phytosterols per day to achieve a 5–10% reduction in total serum cholesterol (Meijer 1999). To ingest 1 g of phytosterols from corn oil, a person would need to eat about 100 g (about ½ cup and about 900 calories) of corn oil per day, an amount that is feasible, but not practical. One recent hamster study (van Tol et al. 1999), comparing corn oil and olive oil, presented evidence that, although both oils reduced LDL cholesterol (‘bad cholesterol’), olive oil was better at increasing HDL cholesterol (‘good cholesterol’). Other recent studies indicated that corn fiber oil is more effective than corn germ oil (commercial corn oil) at lowering serum cholesterol in hamsters (Wilson et al. 2000; Jain et al. 2008). Obviously, more work is required to evaluate the health-promoting properties of corn oil and corn fiber oil. The antioxidant properties of tocopherols (such as those found in corn oil) may be involved in combating atherosclerosis by preventing the oxidation of low-density lipoproteins (Saldeen et al. 1999). Another study indicated that the particular ratio of tocopherols in corn oil (a high ratio of γ-tocopherol/α-tocopherol) may achieve better protection against DNA damage than α-tocopherol alone (Elmadfa and Park 1999). Others have demonstrated beneficial effects of corn oil on blood pressure, platelet aggregation, and diabetes (Strecker et al. 1996).

10.3 10.3.1

MAJOR FOOD USES OF CORN OIL Cooking/salad oil

Of the 2.5 billion pounds of refined corn oil produced in the US in 2004 (equivalent to about 1.1 million tonnes), approximately 47% was used for cooking and salad oils, about 43% was used for shortenings, and the remainder was used for margarines and spreads (Anonymous 2006). Corn oil has long been a popular cooking oil, because of its mild flavor, its stability (due to low levels of linolenate), and its reputation as a healthy edible oil (due its high levels of polyunsaturated fatty acids). Because of its higher levels of polyunsaturates than most other commodity vegetable oils (especially soy), corn oil was considered a superior oil and was sold at a premium. In recent years, with the increased popularity of monounsaturaterich oils (olive, canola, and now NuSun® sunflower oil), corn oil is still considered a premium vegetable oil, but there has been a drop in the price differential between corn oil and other commodity vegetable oils. In January 2010 the wholesale US prices for crude (unrefined) oils from corn, soy, sunflower, and canola oils were 0.39–0.42, 0.36–0.39, 0.54–0.57, and 0.44–0.47 US$/lb, respectively (ERS 2010).

10.3.2

Margarines and spreads

Corn oil margarine (common ‘stick’ margarines contain 80% fat) and corn oil spreads (common ‘tub’ margarine spreads contain 20–65% fat) are popular food products. In the late 1870s Unilever began manufacturing margarine in Europe and the US Dairy Company began production of ‘artificial butter’ in the US (Anonymous 2009b). Sales of corn oil margarine in the US climbed slowly and reached a volume of about 1 million pounds in 1930 (Anonymous 2006). From 1950 to 1980 (when there was growing consumer interest in the health-promoting properties of the polyunsaturates in corn oil), production of corn oil margarine in the US climbed from 15 to 250 million pounds per year (Anonymous 2006). In recent years there has

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been growing concern about the possible harmful effects of the trans fatty acids in margarines and spreads (which can range from 10–20% of the total fatty acids) made from corn oil and other vegetable oils (see Section 10.2), and consumer concerns about trans fatty acids have become a major issue for margarine manufacturers. Methods have been developed to produce margarines, shortenings, and spreads by interesterifying (List et al. 1995) or blending oils (including a patent that details a process to produce ‘trans-free’ shortening by blending corn oil and palm fat; Sundram et al. 1999), thus eliminating the need for chemical hydrogenation and eliminating the formation of trans fatty acids. Zero trans fatty acid margarines and spreads currently account for a major portion of the sales in several European countries, and several manufacturers are now marketing zero trans fatty acid margarines and spreads in the US.

10.4

CONCLUSIONS

Corn oil’s desirable properties include its mild, nutty flavor, its high levels of unsaturated fatty acids, its low levels of saturated fatty acids, its very low levels of linolenic acid, its high levels of unsaponifiables (including phytosterols and tocopherols), and its stability during frying. Although consumer focus has been shifting toward ‘high-monounsaturate’ oils (olive, canola, and NuSun sunflower oils), additional research is still needed to objectively compare the health-promoting properties of polyunsaturates versus monounsaturates. The food industry currently relies on corn oil margarine and other food products that contain hydrogenated corn oils. Additional research also is needed to objectively evaluate the risks associated with trans fatty acid-containing products made from hydrogenated corn oil, especially in light of the recent evidence that at least some types of trans fatty acids (conjugated linoleic acids) may have multiple health-promoting properties.

REFERENCES Anonymous (2006) Corn Oil, 5th edn, Corn Refiners Association, St. Louis, MO, www.corn.org/CornOil. pdf, accessed October 2010. Anonymous (2009a) Corn Annual 2009, Corn Refiners Association, St. Louis, MO, www.corn.org/ CRAR2009.pdf, accessed October 2010. Anonymous (2009b) National Association of Margarine Manufacturers, Washington, DC, www. margarine.org/historyofmargarine.html, accessed October 2010. Anonymous (2009c) U.S.D.A. National Nutrient Database for Standard Reference, Release 22, http://www. data.gov/raw/1458, accessed October 2010. Antoniassi, R., Esteves, W. and Meirelles, A.J.D. (1998) Pretreatment of corn oil for physical refining, Journal of the American Oil Chemists’ Society, 75, 1411–1415. Bocevska, M., Karlovic, D., Turkulov, J. and Pericin, D. (1993) Quality of corn oil obtained by aqueous enzyme extraction, Journal of the American Oil Chemists’ Society, 70, 1273–1277. Byrdwell, W.C., Neff, W.E. and List, G.R. (2001) Triacylglycerol analysis of potential margarine base stocks by high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry and flame ionization detection, Journal of Agricultural Food Chemistry, 49, 446–457. Dickey, L., Cooke, P.H., Kurantz, M.J. et al. (2007) Using microwave heating and microscopy to estimate optimal corn germ oil yield with a bench-scale press, Journal of the American Oil Chemists’ Society, 84, 489–495. Dickey, L.C., Kurantz, M.J., Parris, N., McAloon, A. and Moreau, R.A. (2009) Foam separation of oil from enzymatically treated wet-milled corn germ dispersions, Journal of the American Oil Chemists’ Society, 86, 927–932. Elmadfa, I. and Park, E. (1999) Impact of diets with corn oil or olive/sunflower oils on DNA damage in healthy young men, European Journal of Nutrition, 38, 286–292.

Gunstone_c10.indd 286

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Corn Oil

287

Enig, M.G., Pallansch, L.A., Sampugna, J. and Keeney, M. (1983) Fatty acid composition of the fat in selected food items with emphasis on trans components, Journal of the American Oil Chemists’ Society, 60, 1788–1795. ERS (2010) U.S. Vegetable Oil and Fats Prices, Economic Research Service, USDA, Washington, DC, http://www.ers.usda.gov/Briefing/soybeansoilcrops/Data/table9.xls, accessed October 2010. Exler, J., Lemar, L. and Smith, J. (2001) Fat and Fatty Acid Content of Selected Foods Containing Trans Fatty Acids, USDA Food Nutrition and Information Center, Washington, DC, http://www.nal.usda.gov/ fnic/foodcomp/Data/Other/trans_fa.pdf, accessed October 2010. Fahey, J.W., Clevidence, B.A. and Russell, R.M. (1999) Methods for assessing the biological effects of specific plant components, Nutrition Reviews, 57, S34–S40. FDA (2010) Consumer Nutrition and Health Information, US Food and Drug Administration, Silver Spring, MD, http://www.fda.gov/Food/LabelingNutrition/ConsumerInformation/default.htm, accessed October 2010. Firestone, D. (1999) Corn oil, in Physical and Chemical Characteristics of Oils, Fats, and Waxes, AOCS, Champaign, IL, pp. 31–32. Gertz, C., Klostermann, S., and Kochhar, S.P. (2000) Testing and comparing oxidative stability of vegetable fats and oils at frying temperature, European Journal of Lipid Science Technology, 102, 543–551. Goffman, F.D. and Böhme, T. (2001) Relationship between fatty acid profile and vitamin E content in maize hybrids (Zea mays L.), Journal of Agricultural Food Chemistry, 49, 4990–4994. Hicks, K.B. and Moreau, R.A. (2001) Phytosterols and phytostanols: Functional food cholesterol busters, Food Technology, 55, 63–67. Hojilla-Evangelista, M.P., Johnson, L.A. and Myers, D.J. (1992) Sequential extraction processing flaked whole maize – Alternative technology for wet milling, Cereal Chemistry, 69, 643–647. Howell, T.J, MacDougall, D.E. and Jones, P.J.H. (1998) Phytosterols partially explain differences in cholesterol metabolism caused by corn or olive oil feeding, Journal of Lipid Research, 39, 892–900. Ip, C. (1997) Review of the effects of trans fatty acids, oleic acid, n-3 polyunsaturated fatty acids, and conjugated linoleic acid on mammary carcinogenesis in animals, American Journal of Clinical Nutrition, 66, 1523S–1529S. Jain, D., Ebine, N., Jia, X. et al. (2008) Corn fiber oil and sitostanol decrease cholesterol absorption independently of intestinal sterol transporters in hamsters, Journal of Nutritional Biochemistry, 19, 229–236. Karlovic, D.J., Bocevska, M., Jakolevic, J. and Turkulov, J. (1994) Corn germ oil extraction by a new enzymatic process, Acta Alimentaria, 23, 389–400. Lawson, R.E, Moss, A.R. and Givens, D.I. (2001) The role of dairy products in supplying conjugated linoleic acid to man’s diet: A review, Nutrition Research Review, 14, 153–172. Leibovitz, Z. and Ruckenstein, C. (1983) Our experiences in processing maize (corn) germ oil, Journal of the American Oil Chemists’ Society, 60, 395–399. Leto, K.J. and Ulrich, J.F. (2001) Corn plants and products with improved oil composition, U.S. Patent 6,248,939. Lichtenstein, A.H., Ausman, L.M., Carrasco, W. et al. (1993) Hydrogenation impairs the hypolipidemic effect of corn oil in humans, Arteriosclerosis, Thrombosis, and Vascular Biology, 13, 154–161. List, G.R., Friedrich, J.P. and Christianson, D.D. (1984) Properties and processing of corn oils obtained by extraction with supercritical carbon dioxide, Journal of the American Oil Chemists’ Society, 61, 1849–1851. List, G.R., Mounts, T.L., Orthoefer, F. and Neff, W.E. (1995) Margarine and shortening oils by interestification of liquid and trisaturated triglycerides, Journal of the American Oil Chemists’ Society, 72, 379–382. Maza, A. (2001) Process for the recovery of corn oil from corn germ, U.S. Patent 6,201,142. Meijer, G.W. (1999) Blood cholesterol-lowering plant sterols: Types, doses and forms, Lipid Technology, November, 129–132. Mellon, J.E. and Moreau, R.A. (2004) Inhibition of aflatoxin biosynthesis in Aspergillius flavus by diferuloylputrescine and p-coumaroylputrescine, Journal of Agricultural Food Chemistry, 52, 6660–6663. Moreau, R.A. (2005) Corn oil, in Bailey’s Industrial Oil & Fat Products, Vol. 2, Edible Oil and Fat Products: Edible Oils (ed. F. Shahidi), 6th edn, John Wiley & Sons, Inc., Hoboken, NJ, pp. 149–172. Moreau, R.A. and Hicks, K.B. (2005) The composition of corn oil obtained by the alcohol extraction of ground corn, Journal of the American Oil Chemists’ Society, 82, 809–815. Moreau, R.A. and Hicks, K.B. (2006) A reinvestigation of the effect of heat pretreatment of corn fiber on the levels of extractable tocopherols and tocotrienols, Journal of Agricultural Food Chemistry, 54, 8093–8102. Moreau, R.A., Dickey, L.C., Johnston, D.B. and Hicks, K.B. (2009a) A process for the aqueous enzymatic extraction of corn oil from dry-milled corn germ and enzymatic wet milled corn germ (E-germ), Journal of the American Oil Chemists’ Society, 86, 469–474.

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Vegetable Oils in Food Technology

Moreau, R.A., Hicks, K.B., Nicolosi, R.J. and Norton, R.A. (1998) Corn fiber oil – its preparation, composition, and use, U.S. Patent 5,843,499. Moreau, R.A., Hicks, K.B. and Powell, M.J. (1999a) Effect of heat pretreatment on the yield and composition of oil extracted from corn fiber, Journal of Agricultural Food Chemistry, 47, 2869–2871. Moreau, R.A., Johnston, D.B. and Hicks, K.B. (2005) The influence of moisture content and cooking on the screw pressing and pre-pressing of corn oil from corn germ, Journal of the American Oil Chemists’ Society, 82, 851–854. Moreau, R.A., Johnson, D.B. and Hicks, K.B. (2007) A comparison of the levels of lutein and zeaxanthin in corn germ oil, corn fiber oil, and corn kernel oil, Journal of the American Oil Chemists’ Society, 84, 1039–1044. Moreau, R.A., Johnston, D.B., Powell, M.J. and Hicks, K.B. (2004) A comparison of commercial enzymes for the aqueous enzymatic extraction of corn oil from corn germ, Journal of the American Oil Chemists’ Society, 81, 1071–1075. Moreau, R.A., Lampi, A-M. and Hicks, K.B. (2009b) Fatty acid, phytosterol, and polyamine conjugate profiles of edible oils extracted from corn germ, corn fiber, and corn kernels, Journal of the American Oil Chemists’ Society, 86, 1209–1214. Moreau, R.A., Nuñez, A. and Singh, V. (2001a) Diferuloylputrescine and p-coumaroyl feruloylputrescine, abundant polyamine conjugates in lipid extracts of maize kernels, Lipid, 36, 839–844. Moreau, R.A., Powell, R.A. and Hicks, K.B. (1996) The extraction and quantitative analysis of oil from commercial corn fiber, Journal of Agricultural Food Chemistry, 44, 2149–2154. Moreau, R.A., Powell, M.J. and Singh, V. (2003) Pressurized liquid extraction of polar and nonpolar lipids in corn and oats with hexane, methylene chloride, isopropanol, and ethanol, Journal of the American Oil Chemists’ Society, 80, 1063–1067. Moreau, R.A., Singh, V., Eckhoff, S.R. et al. (1999b) A comparison of the yield and composition of oil extracted from corn fiber and corn bran, Cereal Chemistry, 76, 449–451. Moreau, R.A., Singh, V. and Hicks, K.B. (2001b) Comparison of oil and phytosterol levels in germplasm accessions of corn, teosinte, and Job’s tears, Journal of Agricultural Food Chemistry, 49, 3793–3795. Moreau, R.A., Singh, V., Nunez, A. and Hicks, K.B. (2000) Phytosterols in the aleurone layer of corn kernels, Biochemical Society Transactions, 28, 803–806. Moreau, R.A., Singh, V., Powell, M.J. and Hicks, K.B. (2009c) Corn kernel oil and corn fiber oil, in Gourmet and Health-Promoting Specialty Oils (eds R.A. Moreau and A. Kamal-Eldin), AOCS Press, Urbana, IL, pp. 409–432. Moreau, R.A., Whitaker, B.D. and Hicks, K.B. (2002) Phytosterols, phytostanols, and their conjugates in foods: Structural diversity, quantitative analysis, and health-promoting uses, Progress in Lipid Research, 41, 457–500. Neff, W.E., Adlof, R.O., List, G.R. and El-Agaimy, M. (1994) Analysis of vegetable oil triacylglycerols by silver ion high performance liquid chromatography with flame ionization detection, Journal of Liquid Chromatography, 17, 3951–3968. Orthoefer, F.T. and Sinram, R.D. (1987) Corn oil: composition, processing, and utilization, in Corn: Chemistry and Technology (eds S.A. Watson and P.E. Ramstad), American Association of Cereal Chemists, St. Paul, MN, pp. 535–552. Parker, R.A., Pearce, B.C., Clark, R.W., Gordon, D.A. and Wright, J.J. (1993) Tocotrienols regulate cholesterol production in mammalian cells by post-transcriptional suppression of 3-hydroxy-3-methylgluaryl-coenzyme A reductase, Journal of Biological Chemistry, 268, 11230–11238. Pina, C.G. and Meirelles, A.J.A. (2000) Deacidification of corn oil by solvent extraction in a perforated rotating disc column, Journal of the American Oil Chemists’ Society, 77, 553–559. Radcliffe, J.D., King, C.C., Czajka-Narins, D.M. and Imrhan, V. (2001) Serum and liver lipids in rats fed diets containing corn oil, cottonseed oil, or a mixture of corn and cottonseed oils, Plant Foods and Human Nutrition, 56, 51–60. Ronyai, E., Simandi, B., Tomoskozi, S. et al. (1998) Supercritical fluid extraction of corn germ with carbon dioxide ethyl alcohol mixture, Journal of Supercritical Fluids, 14, 75–81. Saldeen, T., Li, D.Y. and Mehta, J.L. (1999) Differential effects of alpha and gamma-tocopherol on lowdensity lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis, Journal of the American College of Cardiology, 34, 1208–1215. Sebben, E., Slaughter, D.C. and Singh, R.P. (1998) Optical assessment of corn oil during frying, Journal of Food Processing and Presentation, 22, 265–282.

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Shen, N., Duvick, S., White, P. and Pollak, L. (1999) Oxidative stability and AromaScan analyses of corn oils with altered fatty acid content, Journal of the American Oil Chemists’ Society, 76, 1425–1429. Singh, V., Moreau, R.A. and Cooke, P.H. (2001) Effect of corn milling practices on aleurone layer cells and their unique phytosterols, Cereal Chemistry, 78, 436–441. Singh, V., Moreau, R.A., Haken, A.E., Eckhoff, S.R. and Hicks, K.B. (2000) Hybrid variability and effect of growth location on corn fiber yields and corn fiber oil, Cereal Chemistry, 77, 692–695. Snyder, J.M, King, J.W., Taylor, S.L. and Neese, A.L. (1999) Concentration of phytosterols for analysis by supercritical fluid extraction, Journal of the American Oil Chemists’ Society, 76, 717–721. Sommerburg, O., Keunen, J.E.E., Bird, A.C. and Kuijk, F.J.G.M. (1998) Fruits and vegetables that are sources for lutein and zeaxanthin: The macular pigment in human eyes, British Journal of Ophtalmology, 82, 907–910. Strecker, L.R., Bieber, M.A., Maza, A., Grossberger, T. and Doskoczynski, W.J. (1996) Corn oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2, Edible Oil and Fat Products: Oils and Oilseeds (ed. Y.H. Hui), 5th edn, John Wiley & Sons, Inc., New York, pp. 125–158. Strecker, L.R., Maza, A. and Winnie, F.G. (1990) Corn oil – composition, processing and utilization, in Proceedings of the World Conference on Edible Fats and Oils Processing: Basic Principles and Modern Practices (ed D.R. Erickson), AOCS, Champaign, IL, pp. 309–325. Subagio, A. and Morita, N. (2001) Instability of carotenoids is a reason for their promotion of lipid oxidation, Food Research International, 34, 183–188. Sundram, K., Perlman, D. and Hayes, K.C. (1999) Blends of palm fat and corn oil provide oxidation-resistant shortening for baking and frying, U.S. Patent 5,874,117. Ulrich, J.F. and Anderson, S.C. (2001) Extraction of corn oil from flaked corn grain, U.S. Patent 6,313,328. van Tol, A., Terpstra, A.H.M., van den Berg, P. and Beynen, A.C. (1999) Dietary corn oil versus olive oil enhances HDL protein turnover and lowers HDL cholesterol levels in hamsters, Atherosclerosis, 147, 87–94. Verleyen, T., Verhe, R., Garcia, L. et al. (2001) Gas chromatographic characterization of vegetable oil deodorization distillate, Journal of Chromatography A, 921, 277–285. Wang, C., Ning, J., Krishnan, P.G. and Matthees, D.P. (1998) Effects of steeping conditions during wetmilling on the retentions of tocopherols and tocotrienols in corn, Journal of the American Oil Chemists’ Society, 75, 609–613. Weber, E.J. (1987) Lipids in the kernel, in Corn: Chemistry and Technology (eds S.A. Watson and P.E. Ramstad), American Association of Cereal Chemists, St. Paul, MN, pp. 311–350. White, P.J. and Weber, E.J. (2003) Lipids of the kernel, in Corn Chemistry and Technology (eds L.A. Johnson and P.J. White), 2nd edn, American Association of Cereal Chemists, St. Paul, MN. pp. 355–405. Wilson, T.A., DeSimone, A.P., Romano, C.A. and Nicolosi, R.J. (2000) Corn fiber oil lowers plasma cholesterol levels and increases cholesterol excretion greater than corn oil and similar to diets containing soy sterols and soy stanols in hamsters, Journal of Nutritional Biochemistry, 11, 443–449.

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11

Minor and Speciality Oils

S. Prakash Kochhar

11.1

INTRODUCTION

There are many minor vegetable oils that are of great importance because of their special characteristics, properties, nutrition and health benefits. Some, such as sesame seed, rice bran, ‘virgin’ olive oil (Chapter 9) and exotic oils like avocado, argan seed, grape seed, pumpkin seed, hazel nut, walnut and macadamia nut, are now available in selected shops and may be used by the food industry. This chapter deals with several of these minor oils.

11.2

SESAME SEED OIL

Sesame (Sesamum indicum, L.) is one of the oldest oilseed crops known to mankind and is the only cultivated Sesamum species. Sesame seed has been considered important because of its high oil content (42–56%) and protein (20–25%) and also because it is a good source of minerals, particularly calcium, phosphorus, potassium and iron (Deshpande et al. 1996). Sesame oil is highly resistant to oxidation and displays several useful medicinal effects (Kochhar 2000, 2002). Researchers believe that sesame originated in Sudan, where many wild species are found (Bedigian 1984). The magic words ‘Open Sesame’ relate to its popularity in Arab countries. The seed colour varies from white through various shades of brown, gold, grey, violet and black. Because of their characteristic flavour and sweet taste, dehulled sesame seeds are extensively used in baked goods (as a garnish on top of breads, rolls, bread sticks, buns and some biscuits and crackers) and in many confectionery products. In the Middle East and some other countries, sesame seeds are used mainly for preparing tahini (sesame butter) and halvah (sweet). In many European countries sesame snack bars produced with honey, and hummus – a dip-in-chilled product made from chick-pea flour and sesame paste – are sold in stores.

11.2.1

World seed production

Sesame, also known as gingelly, beniseed, sim-sim and sesamum, is an important annual crop of many countries. The sesame plant is cultivated in relatively hot and dry regions because the seeds are adaptable and drought resistant (Salunkhe et al. 1991). India, Myanmar (Burma), China, Sudan, Uganda and Ethiopia are the major countries involved in the growing Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Vegetable Oils in Food Technology Table 11.1 Major countries involved in the production, import and export of sesame seed and oil in 2007. Sesame seed (thousand tonnes) Crop

Imports

India Myanmar China Sudan Uganda Ethiopia Total*

757 590 557 242 168 150 3 056

Exports

China Japan Turkey South Korea Syria United States

226 170 108 60 53 40

India Ethiopia Sudan Nigeria Myanmar Paraguay

317 140 106 80 61 46

Total*

900

Total*

960

Sesame oil (tonnes) Imports

Exports

United States China United Kingdom Japan Malaysia

12 200 3 880 2 900 2 660 2 250

China Japan Mexico India Singapore

10 970 5 770 5 600 5 500 2 150

Total*

40 500

Total*

42 400

Source: FAOSTAT, top 20 countries by commodity; http://faostat.fao.org. Note: * Data from top 20 countries.

and production of sesame seed. It is interesting to note that in Myanmar, the sesame crop matures in about 60 days, in Sudan in about 80 days, and in southern United States, Mexico and India in about 80–140 days, depending on the variety (Deshpande et al. 1996). The total production of sesame seed relating to the 2007 harvest is about 3.01 million tonnes (Table 11.1). China, the third-largest seed-producing country, is involved in the import and export of both sesame seed and the oil. About 30% of this production is exported, particularly to China, Japan, Turkey, EU countries, South Korea, Syria and USA. Some of the seed is used as such or in dehulled form in a variety of exotic products, but the bulk (70%) is crushed to yield oil. Most of the oil is consumed in the major producing countries and only a small amount (about 40 000 metric tons) is exported, mainly by China, Japan, Mexico and India to the USA, Malaysia and the UK.

11.2.2

Lipid composition

Like most vegetable oils, sesame oil consists mainly of neutral triacylglycerols (∼90%), with small quantities of diacylglycerols (6%), free fatty acids, phospholipids and unsaponifiable material. However, compared with other vegetable oils, sesame oil contains a relatively high percentage of unsaponifiable matter (1–2%), which includes sterols, sterol esters, (mainly) γ-tocopherol, and unique compounds called sesame lignans (Hwang 2005; Kochhar 2002). Sesame oil is classified as a polyunsaturated, semi-drying oil containing about 82% unsaturated fatty acids. The fatty acids of sesame oil comprise mainly equal proportions of oleic acid (33–54%) and linoleic acid (35–59%), together with palmitic acid (8–17%) and stearic acid (3–9%)

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Table 11.2 Typical fatty acid composition and Codex ranges of some parameters of sesame seed oil. Parameter Specific gravity (20/20 °C) Refractive index (40/40 °C) Iodine value Saponification value Unsaponifiable matter (g/100 g) Fatty acids (% wt) 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 Others Induction period (h at 120 °C)

Commercially refined sample (typical value)

109 193 0.9–2.0 0.1 9.2 (9.6)* 0.1 5.8 (5.0)* 40.6 (39.7)* 42.6 (45.0)* 0.3 (0.4)* 0.7 (0.6)* 0.2 0.2 0.2

Codex range 0.915–0.924 1.465–1.469 104–120 186–195 2 nd–0.1 7.9–12.0 nd–0.2 4.5–6.7 34.4–45.5 36.9–47.9 0.2–1.0 0.3–0.7 nd–0.3 nd–1.1 nd–0.7

6.0

Source: Kochhar (2002); * Dubois et al. (2007); Codex Stan 210-1999. Key: nd = not detected

(Kochhar 2002). Kamal-Eldin and co-workers (1992b) compared the fatty acid composition and triacylglyerols profiles of different varieties of the cultivated sesame, S. indicum, with three wild species (S. alatum, S. angustifolium and S. radiatum) growing in Sudan, using capillary column GC and HPLC. The oil content of the wild species (29–36%) was much less than that in the cultivated varieties (47–54%). The reported percentage fatty acid ranges of 16:0, 18:0, 18:1 and 18:2 in the S. indicum varieties were 9.2–10.9, 5.2–6.7, 36.1–41.3 and 41.3–46.7, and in the wild species 8.7–11.5, 5.6–9.9, 36.3–44.2 and 36.9–44.8, respectively. Table 11.2 presents the Codex ranges of some parameters and the fatty acid composition of sesame oil, along with typical data for commercially produced oil. The fatty acid composition of sesame oil was only slightly affected by genotype, agroclimatic conditions and stages of ripening (Brar 1977, 1980; Lee and Kang 1980; Sekhon and Bhatia 1972). The triacylglycerol composition of the S. indicum variety comprised 1.5% monounsaturated, 7.7% diunsaturated and 90.8% polyunsaturated triacylglycerols (Kamal-Eldin et al. 1992b). The major triacylglycerols were found to be 25.4% LLO, 19.6% LLL, 15.1% LOO, 1.8% PLL and 8.1% PLO (L = linoleic, O = oleic, P = palmitic, with each three-letter symbol representing all the triacylglycerols containing the three acids indicated). Oil from cultivated S. indicum comprised 88.9% triacylglycerols, 6.5% diacylglycerols, 1.2% free fatty acids, 2.8% polar lipids and 0.6% sterol esters (Kamal-Eldin and Appelqvist 1994a). Fatty acid composition is often used to characterise individual oils, including sesame oil. A number of other parameters such as hydroxyl value, titre and Baudouin test have been described by Kochhar (2002). These can be useful for characterisation of the oil. Aued-Pimentel et al. (2006) have suggested that in addition to fatty acid and sterol composition analysis, evaluation of the tocopherol profile is an important indicator for detecting adulteration of sesame oil.

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Crude oil

Codex

Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others

0.0–0.3* – 15.4–20.3 5.4–8.0 60.3–66.9 6.4–10.6 0.8–2.7 0.3–1.4 –

0.1–0.5 0.1–0.2 10.1–20.0 3.4–12.0 57.7–61.9 6.2–7.8 1.2–5.6 0.7–9.2 4.4–11.9

Total sterols (mg/kg)

4500–19 000

Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol γ-Tocotrienol

2–24§ 3–4 420–570 7–9 –

nd–3.3 nd 521–983 4–21 nd–20

Total (mg/kg)

440–550**

330–1010

Source: Codex Stan 210-1999; * Kamal-Eldin et al. (1992a); ** Kamal-Eldin and Appelqvist (1994b) – predominantly γ-tocopherol (95.5–99%) and a small amount of δ-tocopherol; § Aued-Pimentel et al. (2006). Key: nd = not detected

Unlike many other vegetable oils, sesame oil is dextrorotatory. Minor components of the unsaponifiable fraction of sesame oil are responsible for the optical rotation of the oil, with sesamin (+68.6°) and sesamolin (+218°) having the molecular rotations indicated. The unsaponifiable material (1–2%) consists mainly of sterols, tocopherols and sesame lignans. For four cultivated species of S. indicum, the level of unsaponifiable material has been reported to be 1.4–1.8% (Kamal-Eldin and Appelqvist 1994b). The sesame oils from these species contained total sterols (0.51–0.76%), including desmethyl sterols (85–89% of total sterols), monomethyl sterols (9–11%) and dimethyl sterols (triterpene alcohols) (2–4%), respectively. β-Sitosterol (62–67%), campesterol (15–20%), stigmasterol (5–8%) and Δ5-avenasterol (7–10%) are the major sterols present in both free and esterified forms. The monomethyl sterols (gramisterol, citrostadienol and obtusifoliol) were present mainly as esters (Kochhar 2002). Tocopherols of crude sesame oils are generally in the region of 400 to 700 mg/kg, of which γ-tocopherol is predominant (96–98%) along with a small portion of δ-tocopherol (2–3%). Table 11.3 lists the Codex ranges of the desmethyl sterols and the tocopherol content of crude sesame oil. Sesame seed and its oil contain significant amounts of characteristic lignans, sesamin and sesamolin. Figure 11.1 shows the chemical structures of the two major lignans. A wide range of variation in the levels of sesamin (0.02–1.13%) and sesamolin (0.02–0.59%) was reported in S. indicum oils (Fukuda et al. 1988a; Tashiro et al. 1990; Yoshida and Kajimoto 1994). Kamal-Eldin and Appelqvist (1994b) determined the contents of sesamin and sesamolin in

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295

O

O

O O

O

H

H

H

H

O

O

O O

O

O

O

Sesamin

Sesamolin

Figure 11.1 Chemical structures of two major lignans present in sesame seed and oil.

O

O

O

O

O

O O

O

O

OH O

O

O

O OH

O

OH OCH3

OCH3

O Sesaminol

Sesamolinol

OH

OH

OH

H3CO

Pinoresinol

OCH3

OCH3

O O

COOH Syringic acid

Sesamol

CH = CHCOOH Ferulic acid

HO H3C

O CH3 g - Tocopherol

Figure 11.2 Structural formulae of antioxidants present in sesame seed and oil.

oils from Sesamum indicum to be 0.55% and 0.50% respectively. The presence of other lignans, sesangolin and 2-episesalatin in some wild sesame species has also been reported. Two new lignans, sesaminol and sesamolinol, both with antioxidant properties, have been isolated along with pinoresinol (Fukuda et al. 1986a). The content of these antioxidative lignans, having a phenolic group, in sesame oil is small (Osawa et al. 1985). In commercial crude sesame oil produced from seeds of seven different origins, the percentage of sesamin was 0.31–1.18% and of sesamolin 0.19–0.62% (Kochhar 2002). Traces of sesamol, diasesaminol and sesaminol were also observed in several of these oil samples. The structural formulae of important antioxidative components present in sesame seed and oil are given in Figure 11.2. In addition, the presence of water-soluble potent antioxidants, four pinoresinols and two caffeoyl glucosides has been reported in sesame seed (Katsuzaki et al. 1992, 1993, 1994).

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11.2.3

Seed processing and oil refining

The sequence of commercial processing of sesame seed involves (i) cleaning; (ii) cracking, flaking and conditioning; and (iii) cooking and pressing (single or double) for crude oil. The cake still contains 8–10% of oil and is either solvent extracted for crude oil with subsequent refining or used directly as a premium-quality cattle feed. Yen and Shyu (1988) reported the effects of various pretreatments of the seed on oil yield and quality. The smaller the particle size, the higher the oil yield, but with a slight increase in acid value and hydroperoxide level. Oil pressed from dehulled sesame seeds has the best storage stability. The sesame hull (about 17%) contains a large amount of undesirable oxalic acid and indigestible fibre. Dehulling sesame seed is therefore essential to improve the quality of the meal so that it can be used for human food. Most dehulling methods involve the use of water and its subsequent removal from the wet, dehulled seeds. The cost of this drying process raises the price of the dehulled seeds 30–40% above that of commercial seeds. The dehulled seed contains significantly more oil (58–64%) and less crude fibre, calcium, iron, thiamin and riboflavin. Oxalic acid, mostly present in the seed coat, is significantly decreased in level by dehulling (Narasinga Rao 1985). When the seed is properly decoated, the oxalic acid content is reduced from about 3% to less than 0.25% of the seed mass (Johnson et al. 1979). In many seed-producing countries, cold-pressed crude oil is favoured and used directly in cooking. Sesame oil may be obtained from roasted sesame seed or from seed cooked with steam. Roasted seed is classified according to roasting temperature (e.g.140–150 °C, 160–180 °C and ∼200 °C) and time (5–30 minutes). The expelled oil is filtered and used without further purification. Roasted sesame oil ranges in colour from light to dark brown and has a characteristic roasted flavour, the strength of which depends on the roasting conditions. A large number of nitrogen- and sulphur-containing compounds have been identified among a total of 141 flavour components (Namiki 1995). Each of these seems to contribute to the characteristic flavour of roasted sesame seed and oil, but no single compound has been identified that can be considered responsible for the characteristic roasted sesame flavour. Yoshida (1994) studied the effect of roasting of sesame seeds (at 120–250 °C for 30 minutes) on the composition and quality of the oil. Acid, peroxide, anisidine and thiobarbituric acid values rose with increasing temperature. In the roasted oil at 250 °C, the glycolipid content per 1000 seeds increased markedly (263 mg) compared with unroasted oil (7 mg) and phospholipids were no longer detectable. γ-Tocopherol and sesamolin remained at up to 90% of their original level after roasting at 180 °C, but were almost removed at 250 °C. Roasting at temperatures below 220 °C had little effect on fatty acid composition, but higher temperatures considerably reduced oleic and linoleic acid levels (Yen 1990). Roasted oil is very popular in Chinese, Korean and Japanese cooking because of its flavour. Currently, roasted oil is also available in several supermarkets in the UK and other EU countries. The unroasted oil is usually called sesame salad oil. It is refined by the traditional steps of degumming, neutralisation, bleaching and deodorisation (Deshpande et al. 1996). Han and Ahn (1993) found that refining did not affect sesame oil characteristics but decreased its oxidative stability. The refined oil is pale in colour and pleasant to taste. For use as a base in salad dressing, the oil is generally winterised to remove any higher melting point components. However, for salad oil application, the refined oil requires no winterization. Both roasted and unroasted oils are also used for various pharmaceutical purposes.

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297

Sesame antioxidants and oil stability

Compared with other vegetable oils, sesame oil is highly resistant to oxidative deterioration (Kochhar 2000). Fukuda et al (1988b) found that croutons fried in roasted or unroasted sesame oil had a better oxidative stability than those fried in safflower oil, corn oil or a mixture of soybean and rapeseed oils. Fatty acid composition and tocopherol levels do not completely explain the high stability of sesame oil. Refined sesame oil possesses many fewer antioxidants than roasted sesame seed oil. Yen and Shyu (1989) investigated the effect of roasting conditions (at temperatures of 180 °C, 190 °C, 200 °C and 210 °C for 30 minutes) on the oxidative stability of sesame oil. The results showed that the oil, prepared with roasting at 200 °C for 30 minutes followed by 7 minutes of steam cooking time, had the best oxidative stability. Yoshida and Kajimoto (1994) reported the effect of microwave heating on the antioxidant components and oil quality of sesame seeds. During microwave treatment (for 2, 4, 6, 8, 12, 20, 25 or 30 minutes), the carbonyl and anisidine values increased gradually and the concentration of tocopherols, sesamin and sesamolin decreased until approximately 20% of these components were lost after treatment for 30 minutes. However, after microwave treatment for 16–20 minutes, sesame oil still retained 85% of its antioxidant components. The strong antioxidant activity of roasted oil has been attributed to the sesamol formed from sesamolin during roasting and to the presence of γ-tocopherol. However, this is not enough to explain the strong antioxidant activity of roasted oil. It was noticed (Namiki et al. 1993) that in roasting the antioxidant activity increased significantly with browning, and browning increased significantly above 180 °C. It was thus suggested that browning products, formed especially at temperatures above 190 °C, contributed substantially to the formation of antioxidant components. Most likely, the superior antioxidant efficacy of roasted oil can be explained by the synergistic effect of these known antioxidants with as yet unidentified components. Marked changes have been found to occur during acid clay bleaching of sesame oil. Sesamolin, though not having any antioxidant properties in itself, is a precursor to several phenolic antioxidants. During a normal acid-bleaching process at 90–105 °C, sesamolin is transformed into sesamol, sesaminol and its isomers. The reaction pathway involves scission of sesamolin between acetal oxygen and carbon to produce an oxonium ion and sesamol, and an electrophilic addition of sesamol at the ortho position to the oxonium ion to form sesaminol. Four isomers of sesaminol are then formed by intermolecular transformation (Kochhar 2002). Traditional deodorisation of the bleached sesame oil undesirably removes sesamol almost completely and more than 85% of the original sesamolin and related isomers of sesaminol. This reduces considerably the antioxidant effectiveness of the refined, bleached and deodorised sesame oil. In contrast, it is interesting to report that using a ‘dedicated’ refining process of sesame seed oil (according to the US Patent of Silkeberg and Kochhar 2000), more than 78% of sesamolin and related potent components and 95% of γ-tocopherol were retained. Table 11.4 compares the data on the effects of normal and ‘dedicated’ refining on antioxidants of sesame oil. In contrast, using traditional refining, the losses in antioxidants were very high, only 12.5% by weight of the original total of sesamolin, sesaminol and episesaminol, and 55% by weight of γ-tocopherol being retained in the refined oil. Apart from tocopherols, other phenolics and antioxidant precursors, sesame seed oil also contains considerable amounts (0.08–0.26%) of Δ5- and Δ7-avenasterols and of citrostadienol, which contain an ethylidene group (CH3CH=). These ethylidene-containing side-chain sterols have an antipolymerisation effect that protects the oil at high temperatures. The protective effect

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Table 11.4

Effects of various refining steps on antioxidants (mg/kg) of sesame oil. Sesamolin

Sesamol

Sesaminol

Episesaminol

g-T

Total

Traditional refining* Crude oil Neutralised & washed Bleached Deodorised

5100 4248 0 0

43 7 463 17

0 0 339 284

0 0 480 343

335 226 218 184

5478 4481 1500 828

‘Dedicated’ refining** Crude oil Neutralised & washed Bleached Deodorised

6188 6092 3273 3160

2 tr 1781 1593

10 tr 71 74

nd nd 36 36

402 401 398 383

6602 6493 5559 5246

Source: * Fukuda et al. (1986b); ** Silkeberg and Kochhar (2000). Key: g-T = gamma-tocopherol nd = not detected tr = trace <0.5 mg/kg

at elevated or frying temperatures has been ascribed to the formation of an allylic free radical at C-29 followed by isomerisation to a relatively stable tertiary free radical at C-24 (Gordon 1989; Gordon and Magos 1983). Gertz and Kochhar (2001) suggested that a complex set of non-radical reactions occurs, predominantly at frying temperatures. The polymerisation reactions of triacylglycerols during deep frying could thus be retarded by acid-catalysed reactions involving the ethylidene group-containing sterols and other natural components, such as sesamolin, present in sesame oil. Moreover, the protective effect of such components in sesame oil has been related to the finding that they retard the loss of tocopherols in heated oils and thus enhance the frying life of the oil and subsequently prolong the shelf-life of fried snacks on storage. Yen and Lai (1989) showed that instant noodles fried in sesame oil or in its blend with rice bran or soybean oils had a better oxidative stability than those fried in rice bran or soybean oils alone. Rice bran oil (as discussed later) also contains, in addition to a unique group of compounds called oryzanol, a significant amount (0.36%) of ethyldiene side-chain sterols, which enhance the thermal stability of the oil blend and thus reduce the loss of tocopherols.

11.2.5

Health-promoting effects

Sesame seeds and oil have long been used as health foods to slow down ageing and prevent several ailments (Namiki 1995; Namiki and Kobayashi 1989). Several scientific studies (Hirata et al. 1996; Chen et al. 2005) suggest that consumption of sesame lignans, especially sesamin, sesame diet and/or roasted sesame seeds can reduce significantly total cholesterol and LDL cholesterol in hypercholestrolemic patients, including postmenopausal women who have a higher level of cholesterolemia (Chang et al. 2002). Moreover, high-density lipoprotein cholesterol (HDL-C), ‘good’ cholesterol, levels were unchanged in all of these human studies (Wu et al. 2006). The consumption of sesame oil and its lignans increases plasma and tissue concentration of γ-tocopherol without altering δ-tocopherol (Lemcke-Norojarvi et al. 2001). These findings suggest that sesamin can inhibit the metabolism of γ-tocopherol, which results in its higher bioavailability observed in human and animal studies (Frank et al. 2004; Abe et al. 2005). From the study of rats fed a sesame seed diet, Sirato-Yasumoto et al. (2001)

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suggested that the sesame seeds can possibly exert their triacylglycerol-lowering effect through increasing the rate of fatty acid oxidation and reducing the rate of fatty biosynthesis in the liver. Sesame seed lignans are also known to inhibit Δ5-desaturate activity involved in the biosynthesis of n-6 fatty acids, but have no effect on the biosynthesis of n-3 fatty acids in vivo (Mizukuchi et al. 2003). More research on sesame oil is still needed to explore many other beneficial health effects of lignans of sesame seeds and their metabolites.

11.3

RICE BRAN OIL

Rice (Oryzae sativa L.) is the principal staple food of about half of the world’s population. It is grown in more than 100 countries under a variety of climatic conditions (Wadsworth 1992). When harvested from the field, rice is in the form of paddy (rough rice) where the kernel (white rice) is fully enveloped by the hull. When paddy is milled, the germ and bran layer separate from the endosperm and result in the milling residue, which is commonly called ‘bran’. Rice bran oil is, therefore, a by-product of rice milling and has been used for centuries in many South East Asian countries. Typically, rice bran oil (simply, rice oil or ‘heart’ oil) comprises about 20% saturated fatty acids and an even balance of monounsaturated and polyunsaturated fatty acids (40:40). Rice bran oil contains relatively large amounts of unsaponifiable components (4–5%). In recent years, the oil has gained worldwide attention due to the presence of several health-beneficial components such as the unique material called oryzanol and other high-value compounds, including tocotrienols and squalene.

11.3.1

Production of bran and oil extraction

Current world production of rice is approximately 600 million metric tons per annum (FAO 2007). Most of this is consumed close to the area where it is produced. Milling of rough rice involves drying to 11–12 % moisture, cleaning, shelling, separation of kernels, bran removal, polishing and glazing to add consumer appeal. In some areas, rough rice is dehusked at harvest and brown rice (with the bran layer still attached) is stored for later milling. The bran contains pericarp, aleurone, germ and some endosperm. The milling operation of paddy produces about 20% husk, 8–10% bran and approximately 70% starch endosperm (white rice). Rice bran with ∼15–30% lipids is a good source of protein, minerals, vitamins, phytin, trypsin inhibitor, lipase and lectin (Orthoefer 2005; Gopala Krishna 2000). The oil content of rice bran, produced by a different milling process, is generally in the range of 15–20%. Parboiled rice bran has a higher lipid content (20–30%) due to less endosperm contamination and the outward movement of lipids from aleurone and germ cells to the bran layer (Juliano 1985). In 2005, about 2 million metric tons of rice bran oil was processed. This represents only about 20% of the potentially available rice bran oil from all the rice produced worldwide (FAO 2007). India is the largest producer of rice bran oil, with an estimated production in 2008/09 of 760 000 tonnes (Mistry 2009). Rice bran oil contains 2–4% free fatty acids at the time of milling. If not immediately extracted, the lipids in freshly milled rice bran oil undergo hydrolysis due to the presence of a potent lipase. Development of free fatty acids at the rate of 5–7% per day has been reported in rice bran (Saunders 1986). To obtain good-quality rice bran oil, it is therefore important to stabilise the bran quickly prior to extraction. Sayre et al. (1982) reviewed the methods of stabilising rice bran, which include dry heat, wet heat and extrusion. For example, if the bran is subjected to a short-term high-temperature treatment immediately after milling, lipase

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activity is destroyed and ‘stabilised’ bran is produced. Heat stabilisation of bran at 125–135 °C for 1–3 s at 11–15% moisture causes no adverse effect on nutritional quality in feeding trials with rats, chicks and pigs (Kochhar 2002). The stabilised rice bran is expanded to rice flakes or pellets prior to extraction. Palletising (6–8 mm diameter) not only improves percolation but also minimises the fines in the miscella. The wet extrusion method involves the injection of approximately 10% additional water, usually as steam, into the bran. Typically, this is done with an extruder fitted with steam-injection ports, which reduces the stabilisation temperature to 120 °C. The expansion process yields porous rice bran pellets that facilitate the percolation of solvent for oil extraction. The stabilised rice bran flakes are then dried, prior to extraction, usually by passing hot air over a bed of bran pallets. Typically, stabilised rice bran comprises 18–24% oil, 4–6% free fatty acids, 2–4% moisture, 12–17% protein, 45–55% carbohydrates, 23–35% dietary fibre, 2–6% soluble fibre and 7–10% ash (Kochhar 2002). Sayre and co-workers (1985) showed that the stabilisation of rice bran by extrusion cooking produced high-quality, edible-grade rice bran oil. Wet extrusion produces the most satisfactory pellets for solvent extraction (Orthoefer and Eastman 2004). Hexane is generally used for counter-current extraction of the stabilised bran flakes/pellets in a batch or continuous operation. As waxes are soluble in hot hexane, an extraction temperature between 30 and 50 °C gives optimised oil extraction without excessive wax removal. The extracted oil and hexane miscella are transferred to a solvent-recovery unit for the production of crude rice bran oil. The cake is treated separately with stripping steam in a desolventiser to remove residual solvent. The crude oil is usually dark greenish brown, depending on the extraction method, bran condition and composition. The colour pigments include carotenoids, chlorophyll and Maillard browning products. Parboiled rice bran oil is generally darker in colour than that produced from raw rice bran. The lipid composition of good-quality, crude rice bran oil is presented in Table 11.5. Table 11.5 values).

Lipid composition of crude rice bran oil (typical

Component

% wt

Saponifiable lipids Neutral lipids Triacylglycerols Diacylglycerols Monoacylglycerols Free fatty acids Waxes Glycolipids Phospholipids

90–96 88–89 83–86 3–4 6–7 2–4 3–4 6–7 4–5

Unsaponifiable lipids Phytosterols 4-Methyl sterols 4-Dimethyl sterols (triterpene alcohols)** Hydrocarbons§ Tocopherols and tocotrienols

4.2 43* 10 28 18 3

Source: Sayre and Saunders (1990); Orthoefer (1996). Notes: * These figures are % of total unsaponifiable lipids. ** Mainly oryzanol. § Squalene 16–40%, i.e. 0.12–0.3% in oil.

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Ramsay et al. (1991) studied the supercritical fluid extraction of rice bran oil and found the oil yield with CO2 to be slightly lower (18.0%) than that obtained with hexane extraction (20.2%). Aqueous extraction of oil from rice bran has been studied on a laboratory scale (Hanmoungjai et al. 2000). Extraction temperature and pH were found to be the main factors influencing oil yield. Enzymatic treatment of rice bran prior to solvent extraction or pressing has also been reported (Hernandez et al. 2000). Gaur et al. (2007) have reported that a combination of enzyme-assisted extraction with less toxic butanol led to an oil recovery of 86%. Sparks et al. (2006) compared supercritical extraction with compressed propane and pressurised hexane relative to rice bran oil extraction efficiency. An oil yield of 26.1% was obtained, using an accelerated solvent-extraction system that heated hexane to 100 °C and produced a pressure of 10.34 MPa.

11.3.2

Oil refining and high-value by-products

The composition of the crude oil has a major influence on the refining method and conditions used. Rice bran oil is usually difficult to refine due to high free fatty acid (FFA) levels, waxes, bran fines and pigments. In general, traditional refining of rice bran oil involves dewaxing, degumming, neutralisation, bleaching to improve colour, and steam deodorisation (Orthoefer 2005). Both waxes and free acids exert a strong effect on refining losses. For example, 5% FFA crude oil could have losses from 12–40% by the cup method. The causes of high refining losses in rice bran oil are associated with the presence of hydroxy and oxidised compounds as well as the high FFA content (Hartman and Dos Reis 1976). The simple procedure to remove wax from crude rice bran oil is to use settling tanks in which the crude oil is gradually cooled, followed by filtering or centrifuging. This removes bran fines and most of the wax. Generally, a temperature of less than 60 °C is employed for initial dewaxing, and further dewaxing may be performed in combination with degumming or alkali neutralisation. It is also possible to remove wax from refined bleached oil, but the yields improve if most of the wax is removed prior to alkali refining (Gingras 2000). Degumming and/or acid pre-treatment with food-grade phosphoric acid or citric acid is carried out to precipitate gums, metals and other undesirable components from the oil. Standard water degumming is applied if food-grade lecithin is required. Degumming temperatures above 80 °C are recommended to keep waxes from crystallising and being removed with the gums. Depending on the FFA content and the type of refining process, the degummed or acid pre-treated oil is then neutralised with 16–30 Baume caustic with 20–40% excess. Soap-stock separation temperatures in the region of 55–70 °C work well (Orthoefer 2005). Miscella refining in hexane can also be used to obtain good-quality refined oil from highFFA rice bran oil (Bhattacharyya et al. 1986). The refined oil is water washed to remove traces of soaps and dried prior to bleaching for removal of colour pigments and other undesirable components. Depending on the characteristics of the neutral oil and acid activity of the bleaching earth employed, the bleaching doses may range from 2–4% under standard conditions. The oil is then deodorised by steam stripping (220–250 °C, 2–5 mm of Hg) to remove objectionable flavours/odours and any residual undesirable contaminants. Physical refining, also called steam refining, may be an option for better edible oil yield from high-FFA crude rice oil. However, the oil must be dewaxed, degummed, acid pretreated and bleached before the steam-refining step. The presence of even small amounts of lecithin (phospholipids) will irrevocably darken the oil being steam refined at standard physical refining temperatures. Therefore, in many cases, high-FFA rice bran oil is partially neutralised with caustic and washed prior to steam refining to obtain lighter-colour,

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high-grade, edible rice oil. The fully refined rice bran oil often becomes cloudy/turbid below 15 °C due to the presence of saturated and high-melting triacylglycerols remaining in the oil. The oil requires winterisation to satisfy a cold test of 5 hours if the oil is to be sold in bottles. Typically, rice bran oil winterisation involves cooling from 30–35 °C to 15 °C at a uniform rate over a period of 12 h with slow agitation. The oil is then further cooled to 4–5 °C without agitation, followed by a holding period of 24–48 hours. This allows the highermelting components to crystallise as large stable crystals, which are separated using appropriate filter aids. Winterisation is normally performed prior to deodorisation. Recently, the effect of the various refining steps on the retention of oryzanol in fully refined rice bran oil has been reported (Gopala Krishna et al. 2001). Steam refining of crude rice oil did not affect the content of oryzanol appreciably (total loss 8%) but 83–95% of the original oryzanol content (1.9–2.1%) was lost during alkali refining. Moreover, Narayana et al. (2002) have described more efficient processes to refine rice bran oil, giving special attention to dewaxing, degumming and deacidification steps. The improvement steps include simultaneous dewaxing and degumming, enzymatic degumming, and the removal and separation of glycolipids for potential use in the cosmetics industry. Over recent years, several researchers have produced interesting papers about reefing of rice bran oil, for example Nasirullah (2005) described electrolyte degumming to reduce oil losses during superdegumming; the effect of chemical refining processes on the minor components of rice bran oil (Van Hoed et al. 2006); and the use of membrane technology for efficient filtration in the dewaxing stage and the other key developments (Ghosh 2007). Bhosle and Subramanian (2005) have reviewed the newer techniques that could be employed in the deacidification step of rice bran oil. Vali et al. (2005) have investigated a process for the preparation of food-grade rice bran wax and determined its composition. Almost pure wax esters (> 99% purity) have been obtained after defatting the sediments with hexane and isopropanol, and bleaching with NaBH4 to remove unwanted components such as free fatty acids, alcohols and aldehydes. The by-products of rice bran oil refining include wax, lecithin, soap-stock (containing high-value oryzanol) and deodoriser distillate containing sterols, tocopherols, tocotrienols and squalene. The characteristics and physical properties of purified rice wax are similar to carnauba wax (Sayre and Saunders 1990). Rice bran wax (2–4% level in crude oil) consists of long-chain fatty acids (C16–C26) and fatty alcohols (C22–C30). Crude rice wax is usually purified by washing with acetone or ethanol. In many countries, purified rice wax has been approved as a releasing agent for plastic packaging material intended for food contact and is employed as a coating for fruits and vegetables to prevent moisture loss. Also, it is being used for several applications in the cosmetics industry. Standard water-degumming techniques are used to obtain food-grade rice lecithin. Degumming temperatures above 80 °C are employed to keep waxes from crystallising and being removed with gums, thereby avoiding concentration of waxes in the lecithin fraction. The lecithin produced from rice bran oil is very similar in composition and function to that obtained from soybean oil (Orthoefer 2005). Caustic refining of rice oil removes, along with the soapstock, substantial quantities of oryzanol, which is present in the oil at a level of 1.5–2.9%. The soapstock residue contains 5–10% oryzanol and is excellent feedstock for the industrial production of oryzanol (Seetharamaiah and Prabakhar 1986). After acidification of the soapstock, oryzanol may be recovered by ether extraction at pH 9.5 and further purified by chromatographic and crystallisation techniques. A simulated moving-bed chromatography separator has been examined for the recovery of oryzanol from degummed and dewaxed rice bran oil (Saska and Rossiter 1998). The

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crude product containing 12–15% oryzanol was purified by crystallisation from heptane to produce 90–95% pure oryzanol. Rice bran oil deodoriser distillate contains substantial quantities of tocopherols, tocotrienols, squalene and free sterols. The fatty acid distillates from steam refining may also contain small amounts of oryzanol. These valuable components may be concentrated by molecular distillation at very low pressure and low temperature. Mendes et al. (2005) have described a process to isolate high-value sterols and tocols from deodoriser distillate of rice bran oil using supercritical fluid CO2 extraction.

11.3.3

Lipid composition and food uses

Crude rice bran oil may contain 14–17% of non-triacylglycerol components and 4–5% of unsaponifiable material (Table 11.5). The minor constituents of the oil consist of phospholipids, glycolipids, waxes, sterols, ferulic esters of sterols (oryzanol), tocopherols, tocotrienols, colour pigments, hydrocarbons and squalene. The predominant phospholipid components are phosphatidylcholines, phosphatidylethanolamines and phosphatidylinositols. The glycolipids are mainly galactose and glucose derivatives. Rice waxes have been classified into hard wax melting at 79.5 °C and soft wax melting at 74 °C (Orthoefer 2005). Refining of crude oil removes almost all of the glycolipids, phospholipids and waxes, colour pigments and (partly) other minor components, depending on the conditions used. Table 11.6 lists some important characteristics and fatty acid composition of refined rice bran oil. Depending on the winterisation conditions and the intended application, the cloud point of the refined rice oil may vary from below 0 °C to 17 °C. Palmitic, oleic and linoleic fatty acids constitute 93–95% of the fatty acid portion of the glycerol esters. The major

Table 11.6 Characteristics and fatty acid composition of refined rice bran oil. Parameter

Typical

Range

Specific gravity (20 °C) Refractive index (20 °C) Free fatty acid (as % oleic) Iodine value Saponification value Smoke point (°C) Colour Lovibond (5.25 inch) Unsaponifiable (%)

0.916 1.470 0.05 95 193 213 2.5R, 27Y 4.2

0.916–0.922 1.470–1.474 0.05–0.12 90–110 180–195 2.5–3.5R, 25–35Y 3–5

Fatty acid composition (% wt) 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 Others

0.4 19.8 0.2 1.9 42.3 31.9 1.2 0.9 0.5 0.3 0.6

0.2–0.7 12–28 0.1–0.5 2–4 35–50 29–45 0.5–1.8 0.5–1.2 0.3–1.0 0.1–1.0 1.0 max

Source: Sayre and Saunders (1990); Orthoefer (2005); Firestone (1999); Gopala Krishna (2000). Key: wt = weight

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Table 11.7 Normal (4-desmethyl) sterols composition and content of tocopherols and tocotrienols of rice bran oil. Sterols composition Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others total sterols Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol α-Tocotrienol γ-Tocotrienol δ-Tocotrienol Total (mg/kg)

Crude % (mg/kg) – 20.4 (6580) 7.8 (2520) 54.1 (17 450) 11.0 (3550) 2.2 (710) 4.4 (1420) (20) (32 250)

Range % – 20–28 7–15 49–53 5–11 1–3 2–5

Refined % 0.2 19.8 12.8 60.6 6.6

(mg/kg) (14)a (1448) (943) (4449) (487)

(7765)* (15 090)*

Typical 106*; 347** nd; nd 112; 89 nd; 42 63; 126 284; 301 nd; 10

Mean 292** 1 144 15 71 319 18

Range nd–454** nd–10 16–358 nd–42 nd–174 62–975 nd–104

565; 915

860

88–1609

Sources: * Madawala et al. (2010); ** Kochhar (2002). Note: Figures given in brackets are in mg/kg. Key: nd = not detected

triacylglycerol molecular species of rice bran oil comprises PLO, PLL and OOO (i.e. all glycerol esters containing the acyl groups indicated). The majority of unsaponifiable material of rice bran oil consists of sterols present as free sterols, sterol esters, sterol glycosides and acylsterol glycosides. Sterol glycosides are effectively removed during degumming and refined rice oil is virtually free from these components. Refined rice bran oil contains considerable quantities of Δ5-avenasterol and related sterols containing an ethylidene group (1850–3550 mg/kg). Crude rice bran oil contains 4-desmethyl (normal) sterols 3225 mg/kg, 4-monomethyl sterols 420 mg/kg and dimethyl sterols (triterpene alcohols) 1176 mg/kg. Refining of crude oil removes about 65% of the normal sterols (Kochhar 2002). As with common vegetable oils, β-sitosterol is the major sterol in rice bran oil (49–61%, Table 11.7). More than 75% of the sterols of rice bran oil are esterified and are collectively called oryzanol (a group of ferulic acid esters of triterpene alcohols and plant sterols). These sterol esters of ferulic acid show antioxidant activity as well as physiological/biological effects. The major oryzanol components are the ferulic acid esters of cycloartanol, 24-methylenecycloartanol, campesterol, β-sitosterol and cycloartenol. The total content of oryzanol in five refined rice oils from different processors was reported to be 1150–7870 mg/kg, and the individual components cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate, β-sitosteryl ferulate plus cycloartanyl ferulate were 350–2320, 300–3140, 390–3420 and 0–840 mg/kg respectively (Rogers et al. 1993). The large variation in the concentration of these oryzanol components is probably due to different rice varieties used as well as potential losses during processing. Gopala Krishna et al. (2001) has reported the

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effect of the different refining steps on the retention of oryzanol in refined rice bran oils and on the oryzanol content (1.63–2.72%) of 18 Indian paddy cultivars. Rice bran oil contains a relatively high amount of tocopherols and tocotrienols. The major types present are α-tocopherol, γ-tocopherol, α-tocotrienol and γ-tocotrienol (Table 11.7). The tocotrienols (α, γ and δ) comprise 48–80% of the total tocols. The antioxidant properties of tocotrienols are slightly superior to those of tocopherols, but they also have a variety of additional physiological functions (Eitenmiller 1997; Nesaretnam et al. 1998). Rice bran oil is being used for edible purposes in Japan, Thailand, Korea and India. The oil exhibits excellent frying stability and contributes a pleasant flavour to the fried food. The oxidative stability of rice oil was found to be equivalent to that of peanut oil when tested in simulated deep-frying conditions (Orthoefer 1996, 2005). The good stability of rice oil is probably due to the combined protective effects of oryzanol, phytosterols, squalene, tocopherols and tocotrienols. These make the oil a premium choice for frying high-quality products with delicate flavours, ranging from potato chips (crisps) to other snack products and convenience foods. For the same reason, rice bran oil is rapidly gaining popularity in stir-frying of a variety of oriental dishes, both in the USA and European countries. Winterised rice bran oil is an excellent salad oil and is very suitable for producing mayonnaise and salad dressings. The stearin fraction separated during the winterisation process can be used for margarine and shortening applications. In addition to its pleasant flavour, several factors contribute to the remarkable performance of rice oil as a component in margarine and spreads. Its natural tendency to form stable β′ crystals and its palmitic acid glycerol esters result in a good balance between plasticity, creaminess and spreading properties. Specially produced rice bran oil, retaining high levels of potent antioxidants, can be used as coating/spray oil for a wide range of products, such as crackers, nuts and other similar snacks, to extend their shelf life. Kodali (2009) reported the use of rice bran wax (RBX) in stabilising long-chain polyunsaturated fatty acid oils. The oxidative stability of menhaden oil containing 1.5% RBX was comparable to that of the oil stabilised with a mixture of 500 mg/kg tocopherols and 200 mg/kg tert-butylhydroquinone (TBHQ). The functional and nutraceutical properties of rice bran oil provide several applications in the health-food industry (McCaskill and Zhang 1999). In other words, these unique properties of rice oil make it an attractive food ingredient that can provide healthful benefits to a wide range of food products.

11.3.4

Potential health benefits and future trends

Rice bran oil has a fatty acid composition similar to that of groundnut oil. The oil is rich in phytosterols, squalene, tocopherols and tocotrienols, and, as already discussed, contains a unique compound, called oryzanol, which is a mixture of at least five sterol ferulates. Rice bran oil has many health benefits, such as lowering plasma cholesterol levels (Nicolosi et al. 1991; Rukmini and Raghuram 1991; Sharma and Rukmini 1987; Yoshino et al. 1989). It is also reported to decrease early atherosclerosis (Rong et al. 1997), inhibit platelet aggregation (Seetharamaiah et al. 1990), decrease hepatic cholesterol biosynthesis (Nakamura 1966), increase fecal bile acid excretion (Nakamura 1966) and decrease cholesterol absorption and aortic fatty streak formation (Ni et al. 1997). The beneficial effects of oryzanol and rice oil also include anti-inflammatory properties (Nagasaka et al. 2007), anti-ageing activities (Noboru and Yusho 1970) and anti-dandruff and anti-itching properties (Shugo 1979). Rice bran oil contains significant levels of tocotrienols (400–1000 mg/kg), which display protective benefits in reducing LDL cholesterol. Their anti-carcinogenic effects have also

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been reported in several studies (Gould et al. 1991; Qureshi et al. 1991; Kato et al. 1985; Ngah et al. 1991). Elson and Yu (1994) suggested that isoprenoid constituents of the diet suppress tumour growth by depriving the cells of mevalonate-derived products. This hypothesis links suppression of HMGR (3-hydroxy-3-methylglutaryl co-enzyme A reductase) with the anti-carcinogenic properties of various isoprenoids, including the tocotrienols present in rice-bran oil. Yokoyama (2004), Most et al. (2005) and Clevidence (2007) have extensively reviewed the nutritional properties and cholesterol-lowering capacity of rice bran oil. From the findings of these studies, Iqbal et al. (2004) suggested that long-term intake of the tocotrienol-rich fraction of rice bran oil could reduce cancer risk by preventing hepatic lipid peroxidation and protein oxidation damage. It has been forecast that the production of edible-grade rice bran oil as a by-product of rice milling will continue to grow in many countries, including China (a potential producer of rice bran oil in the near future), India, Thailand and the USA. The usage of rice bran oil is also expected to increase due to new evidence of the potential health-beneficial properties of the oil and its bioactive constituents. As consumer awareness of the high-value nutraceutical components such as oryzanol and tocotrienols of rice oil grows, more of the speciality oil will be used as a nutritional ingredient in a variety of food products and novel foods.

11.4

FLAXSEED (LINSEED AND LINOLA) OIL

Flax crops have been grown for many centuries, but originally for the fibres that can be used as the textile linen. Linseed is an alternative name for flax, which points towards the modern uses of the plant seed (Krawczyk 1999). Both linseed and flax are cultivars of Linum usitatissimum. Linseed varieties have shorter (60–80 cm high) and thicker stems, with more branches compared to flax (80–120 cm). A flax crop produces fewer capsules and smaller seeds than linseed. Crops grown for seed are termed linseed in India and in the UK, flax seed in Canada and oil flax or seed flax in many European countries. The crops grown for both seed and flax are generally called dual-purpose flax or flax grown for fibre flaxseed. The oil content of commonly grown linseed varieties lie between 40% and 44%. The high content of linolenic acid (18:3), usually above 50%, makes linseed oil an excellent drying oil. This is used principally for non-edible purposes, such as in the manufacture of paints, varnishes, linoleum and printing inks. As discussed below, among the unique features of flaxseed is that it is a rich source of ω-3 α-linolenic acid (omega-3), plant lignans and dietary soluble fibre. The whole flaxseed/linseed is edible and is used in the baking and confectionery industries. Moreover, edible flaxseed or linseed oil is sold at health-food stores, where its health benefits are recognised.

11.4.1

Flax production and oil composition

Flax is a subtropical or cool-to-warm temperature annual crop grown mainly in Canada, Argentina, India, the USA, China, Ethiopia, Bangladesh, the Russian Federation, Ukraine and some European countries. More than 60 years ago the average world production of flaxseed was 3.4 million tonnes (Krawczyk 1999), which was more than sunflower oil at 2.5 million tonnes. Since then, however, world production of flaxseed has been about 2 million tonnes annually, Canada being the main producer (∼33%), followed by China (20%), the USA (16%) and India (11%) (Berglund 2002). In 2007, according to FAOSTAT, about 1.65 MMT of flaxseed was produced, with Canada again being the largest producer (∼39%), followed by China (29%), India (10%) and the USA (9%).

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Table 11.8 Characteristics and fatty acid composition of linseed oil (high-linolenic acid varieties). Parameter Specific gravity (25 °C) Refractive index (25 °C) Iodine value Saponification value Unsaponifiable matter (%)

Range

0.4**

Fatty acid composition (% wt) 16:0 16:1 18:0 18:1 18:2 18:3 20:0

5.5–6.5** – 2.2–4.1 13.4–22.2 15.2–17.4 51.8–60.4 –

Sterols composition (%) Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others

0.5; 2§ 0.6; 2.4 24.9; 105 8.3; 35 48.8; 206 14.0; 59 – 0.7; 2.8 2.3; 9.6

0.924–0.936* 1.477–1.482 170–203 188–196 0.1–2.0 Range 5.7–7* tr–0.2 3–4 20–20.3 17–17.3 52–54 tr–0.1 0–0.9 0.1–0.7 25–31 6–9 45–53 8–12 0–3 0–0.3

Total (mg/kg)

422

Tocopherols (mg/kg) α-Tocopherol γ-Tocopherol δ-Tocopherol

tr–1; 12§ 30–575; 520 tr–1; 10

5–10 430–575 4–8

542

440–588

Total (mg/kg)

Sources: Gunstone et al. (2007); * Firestone (1999); ** Choo et al. (2007), Wakjira et al. (2004); § Schwartz et al. (2008). Key: wt = weight; tr = trace

These days most flax is grown to make flaxseed oil, rich in α-linolenic acid (omega-3 fatty acid). Edible flaxseed oil is produced by cold pressing at temperatures lower than 50 °C (this is the legal limit for cold-pressed oils in the UK). Cold pressing without traditional refining is important in producing good-quality flaxseed oil, which also depends on the original seed quality (Zheng et al. 2003). The other factors that can affect the quality and yield of oil obtained from mechanical pressing include the feed rate of the seed into the press, the speed of screw rotation, the choke size and the moisture content of the seed (Wiesenborn et al. 2005). The lipids of flaxseed oil comprise 90–96% acylglycerols (neutral lipids), about 6% glycolipids, 4–6% phospholipids and a small amount (0.4–1.3%) of unsaponifiable components (Stenberg et al. 2005; Choo et al. 2007). The neutral lipids contain 93.5% triacylglycerols, small amounts of mono- and di-acylglycerols and about 3% free fatty acids (Khotpal et al. 1997). Table 11.8 gives some characteristics, fatty acid composition, sterol composition and tocopherols content of linseed oil from high-linolenic acid varieties of L. usitatissium. Both

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seed variety and climatic conditions during maturation affect the linolenic acid content of the oil. The major fatty acids of flaxseed oil comprise 5.5–6.5% palmitic (P), 2.2–4.1% stearic (S), 13.4–22.2% oleic (O), 15.2–17.4% linoleic (L) and 51.8–60.4% α-linolenic (Ln) (Choo et al. 2007; Wakjira et al. 2004). The main triacylglycerol molecular species of the oil comprise LnLnLn 22–35%, PLnLn ∼6%, SLnLn ∼10%, OLnLn ∼15%, LLnLn ∼14%, PLLn ∼5%, POLn ∼5%, SLLn ∼10% and LOO ∼3% (Krist et al. 2006; Holcapek et al. 2003). Linseed oil contains 0.42% of the usual sterols. The predominant sterols, namely β-sitosterol, campesterol, Δ5-avenasterol and stigmasterol, have been reported to be 46%, 29%, 13% and 9% respectively (Gunstone et al. 2007). Schwartz et al. (2008) determined the total sterol content of flaxseed oil to be 700 mg/kg, and reported the composition of normal (desmethyl) and 4-methyl sterols together. Linseed oil contains 440–588 mg/kg of tocopherols, γ-tocopherol being most predominant (Firestone 1999). Moreover, flaxseed oil is also characterised by relatively high levels (43–72 mg/kg) of plastochromanol-8, a unique tocopherol analogue (Velasco and Goffman 2000). In addition, flaxseed oil contains total flavonoids and phenolic acids at 127–256 mg/kg and 768–3073 mg/kg respectively (Choo et al. 2007). The high levels of α-linolenic acid (18:3 n-3) make the oil highly susceptible to oxidation. When the oil is used for food purposes a ‘paint-like’ flavour is imparted to food products in a very short time. Therefore, edible flaxseed oil must be stored under cold, oxygen-free, light-free conditions and be protected by the addition of a suitable antioxidant formulation containing metal chelators and oxygen quenchers. Nag (2000) showed that incorporation of oil-soluble capsicum extract slowed considerably the rate of oxidation of the oil. The colour of the stabilised oil was bright red, but the product flavour was acceptable when used as a salad oil. Traditionally, the oil for human consumption is extracted by the cold-press technique. Depending on the application, the oil is then mildly refined and perhaps deodorised at low temperature for encapsulation and blending with other healthful oils.

11.4.2

Edible uses of flaxseed and its oil

Edible flaxseed oil is not generally used as food oil due to its very low oxidative stability. However, ground or whole flaxseed is edible and is used in many bakery and confectionery products to enhance nutritional value by supplying a good source of the n-3 essential fatty acid, α-linolenic acid. Flaxseed contains about 25% fibre, of which 20–40% is soluble fibre (Vaisey-Genser 1994), which may play an important role in lowering plasma cholesterol. Flaxseed is also a rich source of plant lignans, thought to be protective against hormonerelated cancers of the breast, prostate and colon. Flaxseed and its oil are sold at many healthfood stores for these benefits. Carter (1993) reviewed the usage and health aspects of flaxseed and flaxseed oil, with special emphasis on their high fibre and n-3 fatty acid contents, and their potential use in baked goods and other foods. Thompson and Cunnane (2003) have discussed various nutritional characteristics and health-beneficial effects of flaxseed and its oil. After oil extraction, flax cake or meal is usually sold for cattle feed. Krawczyk (1999) reported that whole flaxseed can be used as a dairy feed to promote the production of conjugated linoleic acid in milk (Dhiman et al. 2000) and in milk fat (Chouinard et al. 2001). Flaxseed can also be used in chicken feed to produce eggs high in n-3 fatty acids (Suzuki et al. 1994; Stroh et al. 1997). The egg protects against oxidative deterioration of α-linolenic acid during its shelf life and n-3-enriched eggs fetch a premium at the grocery store. Over recent years numerous studies (Campos et al. 2008; Paschos et al. 2005, 2007; Albert et al. 2005) have suggested that an α-linolenic acid-rich diet containing flax oil has beneficial effects on cardiovascular diseases including in the endothelium, and in reducing stroke risk, breast cancer risk (Klein et al. 2000), prostate cancer (Leitzmann et al. 2004)

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and gene expression (Deckelbaum et al. 2006). Most flaxseed destined for human consumption is sold in health-food stores or as oil in capsule form as a dietary supplement. The volume of ‘organically’ grown flax is increasing to meet growing demands from the typical health-food consumer. The edible use of flaxseed and its oil is bound to rise in the future due to their health-beneficial components.

11.4.3

Linola oil

The low oxidative stability of linseed oil renders it unsuitable for use as an edible oil. Through traditional plant-breeding procedures, a joint venture between CSIRO (Commonwealth Scientific and Industrial Research Organisation, Australia) and United Grain Growers Ltd of Winnipeg, Canada has led to the development of edible linseed oil. The fatty acid composition of the new oilseed crop, named ‘Linola’ (a registered trademark of CSIRO), has been changed and the level of linolenic acid substantially reduced, from 50% to 2%. This greatly increases the oxidative stability of the oil, which is a polyunsaturated oil almost identical to sunflower oil, safflower oil or corn oil in fatty acid composition. The colour of linola seed is also changed to a pale yellow colour, which allows it to be distinguished from (brownish) traditional flaxseed. The new oilseed crop can be grown wherever flax and linseed varieties are currently cultivated (Haumann 1990; Weiss 1993). The climate in northern Europe is highly suitable for the production of linola where sunflower and corn/maize cannot be produced. Linola seed can be processed in existing crushing plants using standard procedures and linola meal can also be used in ruminant feed in the same way as linseed meal. Refining of crude linola oil by conventional steps (degumming, alkali refining, bleaching, winterisation and deodorisation) produces a pale-coloured bland oil with good oxidative stability (Green and Paul Dribnenki 1994). Analytical data of crude and RBD linola oils are given in Table 11.9. The flavour quality and oxidative stability of pilot-plant deodorised linola oil were found to be comparable with that of rapeseed (canola) oil. The Food and Drug Administration (FDA) has given GRAS approval to linola (‘solin’ is the common generic name) oil for use as a general-purpose cooking, frying and salad oil, and as an ingredient in margarine, shortenings and other food products (INFORM 1998). Currently, because of several beneficial dietary effects, there is a growing interest in the use of linola seeds in many bakery and confectionery applications. Moreover, the golden-yellow colour of linola seed makes it an attractive and appealing topping on bakery goods. Both linola oil and seed of the new oilseed crop appear to have a promising future.

11.5

SAFFLOWER OIL

Safflower (Carthamus tinctorius L.) is a minor oilseed crop that is a member of the thistle (Compositae) family. In ancient times, safflowers were mainly grown and used to produce a bright red dye for colouring textiles. Depending on hull thickness, the oil content of the seed varies from 25–45%. It is widely grown in semi-arid and arid regions of the world. Safflower is cultivated on about 800 000 ha globally with a yield of about 650 000 tonnes. India is the largest producer of safflower (Indian name kusum, kusumbha or karadi oil) in the world and grows the crop on 402 000 ha, producing about 206 000 tons of seed annually (Kizil et al. 2008). The other leading producers are the United States, Mexico, Australia, China, Argentina and Kazakhstan. In 2007, according to FAOSTAT, about 515 000 tonnes of safflower seed were produced, India being the main producer (∼47%), followed by Mexico (22%), the USA (18%) and Argentina (11%). Despite being a minor

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Vegetable Oils in Food Technology Table 11.9 Analytical data for crude and pilot-plant refined, bleached and deodorised (RBD) linola oil. Parameter

Crude oil

RBD oil

1.4657 0.921 46.8 325 0.4 5R, 70Y 0.3 142

1.4665 0.920 46.4 <0.5 0.0 0.9R, 4.7Y <0.02 144

Fatty acid composition (% wt) 16:0 18:0 18:1 18:2 18:3 Others

5.6 4.0 15.9 71.8 2.0 0.7

5.6 4.0 15.9 71.9 2.0 0.6

Sterols (mg/kg) Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol

30 801 164 1608 492

17 530 96 1251 430

Total (mg/kg)

Refractive index (460C) Specific gravity Viscosity (cp) Phosphorus (mg/kg) Chlorophyll (mg/kg) Colour Free fatty acid (as % oleic) Iodine value

3095

2324

Tocopherols (mg/kg) α-Tocopherol γ-Tocopherol δ-Tocopherol

20 471 16

tr 172 nd

Total (mg/kg)

507

172

Source: Green and Paul Dribnenki (1994). Key: nd = not detected tr = trace cp = centipoise

crop, safflower is highly valued worldwide because of the nutritional properties of its seed oil, both in the traditional high-linoleic acid type as well as the high-oleic acid type (developed by natural mutation). There are two types or varieties of safflower, both low in saturated fatty acids, which produce different kinds of oil: the traditional one high in polyunsaturated fatty acid (linoleic acid, 75–83%) and the other high in monounsaturated fatty acid (oleic acid, 74–80%). The lipid composition of solvent-extracted safflower oil comprises about 94% neutral lipids, 4.5% glycolipids and 1.2% phospholipids (Rafiquzzaman et al. 2006). The neutral lipids of crude oil consist of 90.5% (% wt) triglycerides, 2.7% diacylglycerols, 3.1% monoacylglycerols and free fatty acids and unsaponifiable components. Tables 11.10a and b present the Codex ranges of some parameters, fatty acid composition and minor components (sterols and tocopherols) of the high-linoleic acid and high-oleic safflower oil respectively, along with typical data of commercially produced oils. The traditional

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safflower oil has the highest source of ω-6 fatty acid, linoleic acid and vitamin E. Both types of the oils have high levels of β-sitosterol (40–50% of the total sterols and 52–60% of the total sterols in high-linoleic and high-oleic-rich oil, respectively) and are good sources of natural tocopherols (245–660 mg/kg), mainly α-tocopherol with the highest vitamin E activity. Velasco and Fernandez-Martinez (2004) have developed two safflower germplasms with an increased level of tocopherols in the seeds, mainly α-tocopherol. Roasting of safflower seed was found to increase the content of α-tocopherol from 441 to 520 mg/kg in the oil as the roasting temperature increased from 140 °C to 180 °C, thus increasing the oxidative stability of the oil with no significant effect on the fatty acid composition (Lee et al. 2004).

Table 11.10a Fatty acid composition and Codex ranges of some parameters of high-linoleic acid safflower seed oil. Parameter

Typical

Refractive index (25 °C) Specific gravity (20/20 °C) Iodine value Saponification value Unsaponifiable matter (%)

1.474* 0.924** 143 192 0.5

Fatty acid composition (% wt) 14.0 16:0 18:0 18:1 18:2 18:3 Others Sterols composition (%) Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others Total sterols (mg/kg) Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol γ-Tocotrienol δ-Tocotrienol Total tocopherols (mg/kg)

Codex range 1.467–1470 0.922–0.927 136–148 186–198 <1.5

0.1§ 6.8 2.3 12.0 77.7 0.4 0.7

nd–0.2 5.3–8.0 1.9–2.9 8.4–21.3 67.8–83.2 nd–0.1 nd–4.2

– – 13 9 52 1 20 3 2

nd–0.7 nd–0.4 9.2–13.3 4.5–9.6 40.2–50.6 0.8–4.8 13.7–24.6 2.2–6.3 0.5–6.4

3480

2100–4600

445 10 8

234–660 nd–17 nd–12 nd–12

8 471

240–670

Source: * Rafiquzzaman et al. (2006); Codex Stan 210-1999; ** Smith (1996) – at 15.5 °C; § O’Brien (2009). Key: nd = not detected tr = trace wt = weight

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Table 11.10b Fatty acid composition and Codex ranges of some parameters of high-oleic acid safflower seed oil. Parameter

Typical

Codex range*

Refractive index (25 °C) Specific gravity (20/20 °C) Iodine value Saponification value Unsaponifiable matter (%)

1.468§ –

1.466–1470 0.913–0.916

87 – –

80–100 186–194 1.0

nd 5.2; 6.0** 2.2; 2.4 78.0; 78.7 13.2; 12.8 0.1; 0.1 1.3

nd–0.2 3.6–6.0 1.5–2.4 70.0–83.7 9.0–19.9 nd–1.2 nd–2.8

Fatty acid composition (% wt) 14.0 16:0 18:0 18:1 18:2 18:3 Others Sterols composition (%) Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others

Crude**

RBD** nd–0.5 nd–2.2 8.9–19.9 2.9–8.9 40.1–66.9 0.2–8.9 3.4–164 nd–8.3 4.4–11.9

21; (317) 7.5; (113) 71.5; (1084)

20.4; (250) 3.3; (40) 76.3; (937)

Total sterols (mg/kg)

1514

1227

2000–4100

Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol γ-Tocotrienol

206 nd 24 20

153 nd 16 9

234–660 nd–13 nd–44 nd–6 nd–10

Total (mg/kg)

250

178

250–700

Sources: Firestone (1999); * Codex Stan 210-1999; ** Ortega-Garcia et al. (2006); § O’Brien (2009). Key: nd = not detected tr = trace wt = weight

The refining process removed 28.5% of the tocopherols and 19% of the total sterols (Table 11.10b) from high-oleic safflower oil (Ortega-Garcia et al. 2006). Traditionally refined and deodorised high-linoleic safflower oil is flavourless and odourless, and is used mainly in soft margarines and salad oils. High-linoleic safflower oil is generally favoured as a starting material to produce CLA (conjugated linoleic acid)-rich oil by alkali isomerisation under optimum processing conditions (Fernie 2003). The fatty acid composition of the high-oleic oil type is similar to that of olive oil but with a bland flavour. The high-oleic safflower oil is a premium frying oil with high oxidative stability, three to four times more stable than that of the high-linoleic acid type (O’Brien 2009), and contains practically no trans fatty acids.

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Safflower petals are important as a source of medicinal preparations, natural food colour and dyes (on a small scale) for traditional religious occasions. The use of safflower petals for treating several chronic diseases such as hypertension, coronary heart ailments, rheumatism and male and female fertility problems has been reported (Rajvanshi 2005). Currently, safflower oil is popular among health-conscious people. Its health benefits include help in the reduction of the cholesterol level in plasma, reducing excess abdominal (belly) fat weight, regularising menstrual cycles and strengthening the body’s immune system. Many dieticians and doctors recommend the use of safflower seed oil to obese people suffering from diabetes to lower their blood sugar levels. Safflower oil is the richest source of n-6 linoleic acid (82%). Using modern science of plant breeding and biotechnology, Arcadia Biosciences (USA) has successfully produced a high-linolenic acid (GLA, Section 13) safflower oil containing 40% GLA. The US Food and Drug Administration (FDA) regulatory process is now complete for SONOVA 400 highGLA safflower oil. This new dietary product/ingredient was to begin being marketed and sold in the first quarter of 2010 (Watkins 2009).

11.6

ARGAN KERNEL OIL

The argan tree of the family Sapotaceae is found commonly in Morocco. Argan oil is produced from the kernels of the fruits of argan trees (Argania spinosa L.). Traditionally, edible argan oil is prepared by Berber women. They manually break the nuts of argan fruits, which are then collected and roasted. The roasted kernels are crushed with a manual millstone, hand mixed with warm water, followed by hand pressing of the wet dough to furnish the argan oil. On a large scale, argan oil is obtained by mechanical pressing of the roasted kernels, thus reducing the overall time and increasing the oil yield dramatically. In addition, this allows a reproducible and consistent delicate hazelnut flavour for dietary argan oil. Cosmeticgrade oil is produced from non-roasted kernels, and/or by solvent extraction of the pressed cake. Acid value and peroxide value are currently used as quality criteria for different types of argan oil, for example acid and peroxide values of extra virgin oil are specified to be 0.8 and 1.5 meq O2 per kg respectively (Charrouf and Guillaume 2008). High-quality extravirgin argan oil from Morocco is probably the most expensive vegetable oil. The major fatty acids of argan oil are 12% palmitic (P), 5% stearic (S), 46% oleic (O) and 34% linoleic (L). The acylglycerols of the oil consist of about 95% triglycerides, 0.27–1.65% monoacylglycerols, 0.68–1.53% diacylglycerols and 1.1–2% free fatty acids (Maurin 1992). Typical fatty acid composition and some characteristics of argan kernel oil are presented in Table 11.11. The main triacylglyerols molecular species of the oil comprise OOL 19.5%, POL 13.6%, OLL 13.6%, LLL 7.4%, PLL 6.3%, OOO 12.8%, SOO 3.4%, POO 11.5% and PPO 3.2% (Rahmani 2005). The oil contains 0.4–1.1% unsaponifiable matter containing carotenoids (37%), tocopherols (8%), sterols (29%), triterpene alcohols (20%) and xanthophylls (5%). The levels of tocopherols in the extra virgin oil range from 600 to 900 mg/kg, and γ-tocopherol (81–92%) is the main tocopoherol (Table 11.11). Several phenolic antioxidants, including caffeic acid, oleuroein, vanillic acid, tyrosol, ferulic acid, catechol, resorcinol, epicatechin and catechin, have also been identified (Charrouf and Guillaume 2008). These antioxidants and the high levels of γ-tocopherol contribute to the good oxidative stability of the oil, with an induction period of 27 h at 100 °C (Madawala et al. 2010). The percentage levels of five identified triterpene alcohols are 27.9% tirucallol, 27.3% ß-amyrin, 18.1% butyrospermol, 7.1% lupeol and 4.5% 24-metyhlene cycloartanol (Charrouf and Guillaume 2008).

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Table 11.11 Characteristics, fatty acid and sterols composition and tocopherol content of argan oil. Parameter Refractive index (20 °C) ) Specific gravity (20/20 °C) Acid value Iodine value Saponification value Unsaponifiable matter (%) Fatty acid (% wt) 14.0 16:0 18:0 18:1 18:2 18:3 Others Sterols composition (%) Campesterol β-Sitosterol Δ7-Avenasterol Stigmasta-8,22-diene3ß-ol α-Spinasterol Schottenol

Dietary virgin oil*

Range**

1.463–1.472 0.906–0.919 0.8¶

1.463–1.470 0.906–0.919 0.8–2.5* 92–102 190–195 0.4–1.1

1.0 0.1§; tr† 12.3; 11.9 5.1; 5.8 45.9; 45.0 34.4; 35.6 1.4; 0.1 0.8; 1.6

0.1–0.2* ** 11–16 4–7 43–50 29–36 0.1–0.3 0.3–0.4

nd† nd nr 3.3

<0.4* nd 4–7 3.2–5.7

45.8 50.9

34–44 44–49

Total sterols (mg/kg)

121 731

142–220

Tocopherols α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol

(mg/kg) 90† nd 463 71

(% wt)* ¶ 2.4–6.5 0.1–0.3 81–92 6.2–12.8

Total (mg/kg)

624

600–900

Sources: * Charrouf and Guillaume (2008); ** Firestone (1999); § Dubios et al. (2007); identified sterols presented, and 445 mg/kg of other unidentified sterols. Key: nd = not detected nr = not reported tr = trace wt = weight ¶ extra virgin oil

†

Madawala et al. (2010) –

Argon oil contains between 142 and 220 mg/kg of phytosterols, and the two major sterols found in oil are 44–49% shottenol (Δ7-stigmastenol) and 34–44% α-spinasterol (7,22-stigmastadien-3ß-ol; Table 11.11). Interestingly, the most common sterol, ß-sitosterol, occurring in most vegetable oils, is absent from argan oil. These findings are important in detecting the adulteration of argan with cheaper vegetable oils. Dietary argan oil is traditionally considered to have several heath-beneficial properties. Some clinical trials and human epidemiological studies have confirmed properties such as hypercholesterolemia and lipid lowering, hypertension reducing and an anti-proliferation effect on prostate cancer (Bennani et al. 2007; Cherki at al. 2005; Drissi et al. 2004; Khalloulki et al. 2003). The phenolic fraction of argan oil has been shown to inhibit LDL oxidation, thereby reducing cardiovascular risks (Berrougui et al. 2006). Some clinical researchers recommend an argan oil-rich diet to patients with cardiovascular diseases.

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Cosmetic-grade argan oil is used for treating skin pimples, juvenile acne, chickenpox pustules and dry skin, and reducing the rate of appearance of wrinkles.

11.7

AVOCADO OIL

Avocado (Persea americana) is a subtropical tree grown in Mexico, Chile and the USA, and in smaller producer countries such as Indonesia, Israel, Spain, South Africa, New Zealand and Australia. Avocado oil is generally produced from fruit rejected by the fresh-food trade market. The cosmetic-grade oil is often produced from poor-quality rejected fruit, with the crude oil being subsequently refined, bleached and deodorised. The RBD oil is pale yellow with little avocado odour or taste, and is highly valued for its beneficial effects on the skin. Avocado oil is easily absorbed by the skin and its unsaponifiable material is reported to provide some protection from the sun. Cold-pressed avocado oil is a relatively new product with significant production and marketing only in recent years. The oil content in commercially mature avocados ranges from 10–32% on a flesh weight basis, depending on the time of harvest (Woolf et al. 2009). There is very little oil (∼2%) in the seed. The major fatty acids of cold-pressed avocado oil include 10–20% palmitic, 4–9% palmitoleic, 56–78% oleic and 10–15% linoleic acids, which are similar to olive oil. In addition, the cold-pressed oil contains relatively high levels of pigments (chlorophylls 11.1–18.5 mg/kg and carotenoids 0.9–3.5 mg/kg), making it green. Avocado oil extracted commercially by using the aqueous extraction method (Wong et al. 2008) is marketed as ‘naturally’ extracted culinary oil. This speciality/culinary oil appeals to consumers looking for a delicate buttery flavour without the pungent notes of virgin olive oil. Moreover, avocado oil has a high smoke point (>250 °C), which makes it suitable for shallow pan frying. The cold-pressed avocado oil is rich (2–7%) in unsaponifiable components, including 2230–4480 mg/kg of total sterols (mainly ß-sitosterol, 81–92%), 70–190 mg/kg of tocopherols, mainly α-tocopherol, mean value 110mg/kg (Table 11.12), and many still-unidentified components (Watkins 2009). Due to the presence of many bioactive lipid-soluble components in avocado oil, several health-promoting effects have been reported. These include inhibiting growth of prostate cancer cells, helping to reduce fat accumulation and obesity, and protection of eyesight in the elderly (Woolf et al. 2009; Lu et al. 2005; Koh et al. 2004).

11.8

CAMELINA SEED OIL

Camelina (Camelina sativa, also known as gold of pleasure or false flax) is a flowering plant in the Brassicaceae family. The plant can be grown on poorer soils that require lower inputs of fertilisers and pesticides than traditional crops. Moreover, camelina needs little water and does not compete with food crops. To improve the health of the soil, false flax may be used as a rotation crop for wheat. The seed yield is in the range of 1.5–3 tonnes per hectare and the oil content varies between 36 and 47%. The range values of refractive index at 20 °C, iodine value and saponification value of the camelina oil are 1.476–1.478, 127–155 and 180-190 respectively (Firestone 1999). Over 50% of the fatty acids in camelina seed oil are polyunsaturated acids that comprise α-linolenic acid 30–40% and linoleic acid 15–24%. The oil also contains significant amounts of oleic acid (10–20%) and about 12% eicosenoic acid (20:1). The typical fatty acid composition of

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Table 11.12

Characteristics, fatty acid and sterol compositions and tocopherol content of avocado oil.

Parameter Refractive index (25 °C) ) Specific gravity (20/20 °C) Free fatty acid (as % oleic) Peroxide value (meq/kg) Iodine value Saponification value Unsaponifiable matter (%) Fatty acid (% wt) 14.0 16:0 16:1 18:0 18:1 18:2 18:3 Others Sterols composition (% of total sterols) Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Avenasterol

Aqueous-extracted oil*

Range** 1.462–1.470 0.906–0.919

<0.5 <4.0

2–7 Typical –; nd† 15.7§; 12.6 7.3; 4.3 0.7; 0.5 60.3; 72.2 13.7; 9.7 1.4; 0.6 0.3; 0.1

85–90 177–198 1–12

9–22* ** 2–9 0.4–1.0 52–78 8–19 0.2–2.0

nd nd 5.5† 0.2 88.1 6.2 nr

0–0.2** 2 6–8 0–2 89–92 3 0.2

Total sterols, mg/kg

434 272

4040

Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol δ-Tocotrienol

89†; 110* 8 ; <10 38 ; <10 14 ; <10 15

64–100**

155–173; 70–190

83–100

Total (mg/kg)

0–19

Sources: * Woolf et al. (2009); ** Firesone (1999); § Dubios et al. (2007); † Madawala et al. (2010), total sterols also contained 910 mg/kg unidentified. Key: nd = not detected nr = not reported tr = trace wt = weight

C. sativa oil is 5.3% palmitic, 3.4% stearic, 1.4% eicosanoic, 18.7% oleic, 11.6% eicosenoic, 2.5% erucic, 16% linoleic and 38.1% α-linolenic acid (Abramovic and Abram 2005; Shukla et al. 2002). Despite its high level of unsaturation the oil shows reasonable oxidative stability, probably due to the presence of highly potent tocols, mean 170 mg/kg, mainly γ-tocopherol (>80%) and β-tocotrienol (Budin et al. 1995). Zubr and Matthaus (2002) have reported the effects of growth conditions on fatty acids and tocopherols in camelina oil. Abramovic et al. (2007) studied the changes occurring in the phenolic content, tocopherol composition and oxidative stability of the oil. They showed that the content of polar phenolic compounds in oil stored at 65 °C deceased linearly with peroxide value and with p-anisidine value. The oxidative stability of highly unsaturated camelina oil (induction

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period of 4.8 h at 110 °C) was increased by 60% by the addition of rosemary extract (Abramovic and Abram 2006). Camelina oil is reported to contain an unusually high level (188 mg/kg) of cholesterol compared with other vegetable oils (Shukla et al. 2002). Recently, Schwartz et al. (2008) reported a cholesterol level of 350 mg/kg in camelina oil and a total sterol level of 5110 mg/kg, which is predominantly ß-sitosterol (59%). Tocopherol content in the oil was found to be 780 mg/ kg (mainly γ-tocopherol at about 92%). Because of the apparent health benefits of the n-3 fatty acid, α-linolenic acid, the use of gold of pleasure oil as a functional food oil is being developed in a variety of food products as an alternative to linseed/flax. The oil is also attractive to bio-diesel producers looking for a comparatively cheaper feedstock.

11.9

GRAPE SEED OIL

Grape seed oil is a vegetable oil pressed from the seeds of various varieties of Vitis vinifera grapes, by-products of the wine-making industry. Most grape oil is produced in Italy, followed by France, Spain and Argentina. The seed contains 6–20% oil which is rich in linoleic acid, about 72% (Kamel et al. 1985). The oil contains 0.8–1.5% unsaponifiables rich in sterols. It contains a small amount of α-tocopherol (Oomah et al. 1998) but is rich in tocotrienols. Some physical characteristics, typical fatty acid composition and Codex ranges of grape seed oil, including sterols and tocopherols composition, are presented in Table 11.13. A large variation in the phytosterol content of grape seed oil has been reported in the literature. Beveridge et al. (2005) reported the content of sterols in grape seed oil from eight varieties ranging from 3160 to 18 610 mg/kg, while Crews et al. (2006) found 2580 to 11 250 mg/kg among ten grape varieties grown in three countries. β-Sitosterol was the major sterol, comprising about 60–80% of total sterols, slightly out of the Codex range given, and followed by campesterol, stigmasterol and Δ5-avenasterol. Grape seeds also contain small amounts of steradienes, dehydration products of sterols formed during heating or acidic conditions of the bleaching process. The content of steradienes in commercially extracted grape seed oils varies from 0.05 to 6.7 mg/kg (Crews et al. 2006). Processing has an effect on the content of undesirable polyaromatic hydrocarbons (PAH) (Moret et al. 2000). Some samples of grape oil are reported to have higher levels of PAH than desired (Gunstone 2006). The tocol profile of grape seed oil is different from other berry seed oils. Like rice bran, palm and wheatgerm oils, grape seed oil is tocotrienol rich (Beveridge et al. 2005; Crews et al. 2006). The major tocols, in a commercial sample of grape oil containing total tocopherols of 550 mg/kg, were γ- and α-tocotrienols (Oomah et al. 2000). In other studies, γ-tocotrienol was the major tocopherol, followed by smaller amounts of α-tocotrienol and α-, ß-, and γ-tocopherols (Table 11.13). The tocol content of grape oil is affected by the processing of the seed and the refining of the oil. For example, crude grape seed oil contained 1010 mg/kg of total tocopherols, but this level decreased by 10% after degumming, dewaxing, bleaching and physical refining (Martinello et al. 2007). It is worth mentioning that by using supercritical fluid extraction under optimum conditions, the α-tocopherol (vitamin E) content of grape oil was increased sixfold to 265 mg/kg, compared to that obtained by normal hexane extraction (Bravi et al. 2007). Grape seed oil has a light taste that can be described as slightly ‘nutty’. The oil is often used for salad dressings, stir-fries, and as an ingredient in homemade mayonnaise. Grape oil

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Table 11.13

Fatty acid composition and Codex ranges of some parameters of grape seed oil.

Parameter Refractive index (40 °C) Specific gravity (20/20 °C Iodine value Saponification value Unsaponifiable matter (g/100 g) Fatty acid composition (% wt) 14.0 16:0 18:0 18:1 18:2 18:3 Others Sterols composition Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol Others Total sterols (mg/kg) Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol α-Tocotrienol γ-Tocotrienol δ-Tocotrienol Total (mg/kg)

Crude oil

Codex range

0.8–1.5

1.467–1.477 0.920–0.926 128–150 188–194 2.0

nd 6.9* 4.1 18.3 68.4 0.3

6.3–11.6** 3.6–5.4 12.7–20.9 61.3–74.6 0.3–1.8 nd–1.2

nd–0.3 5.5–11.0 3.0–6.5 12.0–28.0 58.0–78.0 nd–1.0 nd–4.0

(%); (mg/kg) nd 0.5; 9* 10.3; 184 9.2; 164 74.9; 1336 5.1; 91

(%) nd–0.5 nd–0.2 7.5–14.0 7.5–12.0 64.0–70.0 1.0–3.5 0.5–3.5 0.5–1.5 nd–5.1

1784

2000–7000

216*; 36–309**; 10–229§ nd; 22–153; 10–133 111; 21–141; 10–168 nd; nd; 10–69 137; 102–228; 10–352 191; 217–383; 10–785 nd; nd; nd

16–38

655; 600–1000; 60–1210

nd–89 nd–73 nd–4 8–107 115–205 nd–3.2 240–410

Sources: * Madawala et al. (2010); ** Beverege et al. (2005); § Crews et al. (2006); Oomah et al. 2000, Codex Stan 210-1999. Key: nd = not detected wt = weight

is also a preferred cosmetic industry ingredient, and has been applied to clear up foot problems such as itching and scaly flaking. Grape seeds contain several types of antioxidative and health-beneficial components, including tocotrienols, resveratrol and proanthocyanadins. Yilmaz and Toledo (2006) reported the effect of solvent type on grape seed polyphenols, which are not significantly present in grape seed oil due to their high polarity. Polyphenol components are more concentrated in grape juice and red wine. The potential health benefits of grape seed oil are probably attributable to high levels of phytosterols and tocotrienols.

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Nash (2004) reported that the oil may increase high-density lipoprotein (HDL) cholesterol and reduce ‘bad’ LDL cholesterol, thus helping in the prevention of heart disease. Other possible health uses of this promising oil as an ingredient in food and cosmetic products are being recognised and developed.

11.10

PUMPKIN SEED OIL

Pumpkin (Cucurbita pepo var.) seed oil is made by pressing roasted, hulled pumpkin seeds (oil content 38%), and is a culinary speciality oil of south eastern Austria and adjacent regions. The roasting of seeds at temperatures up to 130 °C, prior to pressing, leads to the formation of the typical roasted and nutty aroma. Usually the seed meal is roasted at about 110 °C for 50 to 60 minutes to produce the characteristic dark green oil. The green colour is attributed mainly to protochlorophyll present in the thin hulls of the seeds and in the oil (Teppner 2004). Styrian pumpkin seed oil is mainly produced for the local market, with only a small percentage for export. Other types of pumpkin seed oil are also marketed worldwide. The producers use white seeds to produce cheaper, lightcoloured oil. China and India are new producers of pumpkin seeds for the international market. The oil content of different varieties and species of pumpkin seeds varies from 22% to 50% (Stevenson et al. 2007). In all species and varieties, the fatty acid composition is dominated by linoleic acid, oleic acid, palmitic acid and stearic acid. Table 11.14 gives some characteristics and fatty acid composition of pumpkin seed oil. The oil from black pumpkin seeds contains more unsaturated fatty acids (87%) than that present (78.5%) in the oil from white seeds. In Styrian pumpkin seed oil the average content of linoleic acid is 54.2% (range 35.6–60.8%) and oleic acid is 26.6% (range 21.0–46.9%). The main triacylglycerol components of the oil are dioleopalmitin (5.8–18.8%), dipalmitolinolein (8.1–8.8%), triolein (6.3–20.5%), palmitoleolinolein (15.0–16.1%), dioleolinolein (16.7–23.0%), dilinoleopalmitin (4.6–15.4%) and dilinoleolein (6.7–19.4%) (Yoshida et al. 2004). The total sterol concentration in pumpkin seed is reported to be 1710 mg/kg, which increases to 1930 mg/kg after the roasting process (Murkovic et al. 2004). The sterol profile of pumpkin seed oil is very different from that of normal vegetable oils, comprising about 30% spinasterol of the total sterols (Firestone 1999). Typically, the main sterols of pumpkin seed oil are Δ7-sterols: comprising Δ7,22.25 -stigmasatrienol (326 mg/kg), Δ7,22-stigmastadien3ß-ol (spinasterol) (300 mg/kg), Δ7.25-stigmastadienol and Δ7-stigmastenol (combined 310 mg/kg), Δ7-avenasterol (164 mg/kg), and ß-sitosterol (58 mg/kg) (Mandl et al. 1999). The concentrations of α-tocopherol and γ-tocopherol in the fresh dried seeds are 37.5 and 383 mg/kg, respectively. The concentration of the tocotrienols is about one third that of the tocopherols (α-T3 about 12 and γ-T3 about 128 mg/kg) (Murkovic et al. 2004). In the oil, tocopherols show a great variation. α-Tocopherol occurs at the level of 41–620 mg/kg, and γ-tocopherol in the range of nd–140 mg/kg. That is the level of γ-tocopherol is about 5 to 10 times higher than that of α-tocopherol. The level of ß- and α-tocopherol is normally below than that of γ-tocopherol. Pumpkin seed oil is light to dark green in colour, depending on the thickness of the sample. Due to the presence of photosensitisers (protochlorophylls), the oil should be stored in the dark at cold temperatures to ensure good stability. The oil has an intense nutty taste and

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Table 11.14

Some characteristics and fatty acid and sterol composition of pumpkin seed oil.

Parameter

Range§

Specific gravity (20/20 °C) Refractive index (20 °C) Iodine value Saponification value Unsaponifiable matter (%) Fatty acid composition (% wt) 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 Others

0.903–0.926 1.466–1.474 116–133 174–197 0.5–1.8 White* seeds

Dark/green* seeds

12 cultivars** C. maxima

Range§

– 10.7 – 8.1 30.0 48.5 – – –

– 5.7 – 6.2 34.9 52.1 – – –

0.1–0.3 check 12.6–18.4 0.1–0.5 5.1–8.5 17.0–39.5 18.1–62.8 0.3–0.8 0.3–1.1 0–0.8

0.1§ 7–15 – 3–13 21–47 36–61 – 0.3–0.5 0–0.8

Sterols composition (% of total sterols) Stigmasterol Δ7-Stigmastenol Δ7-Avenasterol Other sterols 24-Methyl-cholest-7-enol Δ7,25-Stigmastadienol Δ7,22,25Stigmastatrienol α-Spinasterol

1§ 4 10 6 22 29 27

Sources: * Gunstone (2006); ** Stevenson et al. (2007); § Firestone (1999). Key: wt = weight

is traditionally used for salad dressings, adding typical aroma and colour to prepared foods such as soup, scrambled eggs and ice cream (giving an exquisite nutty flavour). Both pumpkin seed oil and the seeds are used in folk medicine for curing prostraterelated symptoms. Other health-beneficial properties (e.g. protection for bones, arthritis) of the seeds and oil are also being investigated.

11.11

SEA BUCKTHORN OIL

Sea buckthorn berries grow naturally in northern China and are traditionally used for both food and medicine. The sea buckthorn (Hippophae rhamnoides) berry bush is now cultivated in many European countries, North America and Japan. Two oils with different fatty acid compositions are derived from the berry seed and from the pulp/soft part. The seed oil is highly unsaturated, with linoleic and α-linolenic acids together comprising about 70% and practically no palmitoleic acid (16:1 n-7). The oil from the soft/pulp part is rich in palmitic and palmitoleic

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Table 11.15 Fatty acid composition of oil from the seed and berry/soft part of sea buckthorn berries of different subspecies. Sample

Fatty acid (wt%)

Seed oil* Berry oil* Subspecies** H. mongolica H. rhamnoides H. sinensis

16:0

16:1n-7

18:0

18:1n-9

18:1n-7

18:2n-6

18:3n-3

7.7 23.1

– 23.0

2.5 1.4

18.5 17.8

2.3 7.0

39.7 17.4

29.3 10.4

30–40 20–30 15–30

40–50 30–40 12–35

1–3 1–2 1–2

4–7 13–20 12–25

5–7 8–10 6–10

5–8 6–15 3–6

1–2 1–6 1–10

Sources: * Yang and Kallio (2001) – mean of 21 samples of Hippophae rhamnoides; ** Yang (2001). Key: wt = weight

acids and the levels vary with the origin and subspecies of the berries. For example, Hippophae mongolica soft/pulp berry oil contains 30–40% palmitic acid and 40–50% 16:1. Table 11.15 presents the fatty acid composition of seed oil and soft part berry oil from different subspecies of sea buckthorn. Sea buckthorn (soft part) oil is also rich in carotenoids (∼1% w/w of the oil), and contains 0.3–0.5% tocopherols (mainly α-tocopherol), 2–3% phytosterols (Kallio et al. 2002; Yang 2001; Yang and Kallio 2001; Yang et al. 2001). The seed oil contains roughly equal levels (0.1%) of α- and γ-tocopherols (Zadernowski et al. 2003). Commercially, sea buckthorn oil is produced by supercritical CO2 extraction from dried soft parts of berries from different sources. Several health benefits are claimed for this oil, which is now available in capsule form and is being incorporated into many functional foods. The protective effects of the oil include being anti-inflammatory on the skin and mucosa, suppressing growth of cancer cells, regulating immune function and reducing risks for cardiovascular disease (Yang 2001). The beneficial effects of sea buckthorn oil are probably due to the combined effects of the fatty acids and the minor bioactive components.

11.12

COCOA BUTTER AND CBE

Cocoa butter equivalents (CBE) are commercially available vegetable fats containing a similar mixture of triacylglycerols as are present in cocoa butter. They also exhibit the same polymorphic and crystallisation behaviour. All combinations of cocoa butter and CBE crystallise in a stable ß2-3 (form V) crystal form. The six permitted tropical fats that can be formulated to produce CBE include palm oil (palm mid fraction; Chapter 2), illipe butter, kokum butter, sal fat, shea butter and mango kernel fat. The EC chocolate directive (2000/36/EC) allows up to 5% of CBE in chocolate in several member states. If CBE are added, consumers have to be informed by appropriate labelling. A reliable method to detect and quantify CBE in milk chocolate has been developed by Buchgraber and Androni (2007), the triacylglyerols profiling method (Buchgraber et al. 2007), as well as the standard methods (ISO 2006; AOCS 2007).

11.12.1

Cocoa butter

Cocoa trees require a tropical climate and are grown in a belt around the equator; that is, in Central America, Africa and the Far East. Cocoa butter (Theobroma cocoa) is obtained by pressing fermented beans, which have developed the cocoa flavour. The fat content of the

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beans is about 60%. The major fatty acids of cocoa butter comprise 23–25% palmitic (P), 33–36% stearic (S), 33–37% oleic (O) and 2-4% linoleic (L) (Firestone 1999). The main triacylglycerols molecular species are 15–18% POP, 34–41% POS, 24–29% SOS, 2–5% POO, 4–8% SOO and 1°2% PPS/PSS. Cocoa butter has a sharp melting point (31–35 °C) and melts completely in the mouth. It is brittle and fractures readily and is not greasy to the touch. These properties of cocoa butter are a reflection of its triacylglycerol composition, which is predominantly monounsaturated, disaturated glycerides (SatUSat), about 80%. Cocoa butter also contains 0.2–1% unsaponifiable matter, 1800–2100 mg/kg total sterols (58–63% ß-sitosterol, 24–31% stigmasterol, 8–11% campesterol) and 25–220 mg/kg tocopherols, mainly 85% γ-tocopherol (Firestone 1999). It also contains about 1% theobromine (Lidefelt 2007). Cocoa butter is used extensively in making chocolate and other confectionery products, and to a limited extent as an ingredient in cosmetic and pharmaceutical products. It is normally one of the most expensive fats and its high and variable cost has stimulated extensive research into cocoa butter replacement fats (CBR) and CBE. Further information on cocoa butter, CBE, CBR, CBI and confectionery fats is available in the literature (Stewart and Timms 2002; Timms 2003).

11.12.2

Illipe butter (Borneo tallow)

Illipe butter (Shorea stenoptera) is derived from the nuts of trees widely grown in Sarawak and other parts of northern Borneo. The fat content of ripe nuts varies between 40 and 60%. The main fatty acids of illipe butter are 18–21% palmitic (P), 39–46% stearic (S) and 34–37% oleic (O). The melting point of illipe fat is 37–39 °C, and its iodine value range is 29–38 (Firestone 1999). The fat contains 0.7–2% unsaponifiable matter (Kochhar 1997), including tocopherols (300 mg/kg) consisting of 70% α-tocopherol, 17% ß-tocopherol and 8% γ-tocopherol. Compared to cocoa butter (Table 11.16), a typical symmetrical monounsaturated triacylglycerol composition of illipe butter is 7% POP, 34% POS and 45% SOS. The percentage level of POS resembles that of cocoa butter (37%), making it useful as a component of cocoa butter equivalent (CBE) blends. Illipe fat can be used directly in cocoa butter equivalents without further processing. Campbell (2002) has provided an interesting account of the commercial development of illipe butter.

11.12.3

Kokum butter

The kokum tree grows in the forests of the western India, from Konkan to Mysore. Kokum (Garcinia indica) seeds contain around 44% fat. Kokum butter is a stearic- and oleic-rich fat: 2–5% palmitic (P), 52–56% stearic (S), 39–42% oleic (O) and 1–2% linoleic (Firestone 1999). The melting point of kokum fat is 38–42 °C, iodine value range 33–35 and unsaponifiable matter 0.4–2.3% (Lidefelt 2007; Kochhar 1997). Symmetrical monounsaturated triacylglycerol composition data of various tropical fats (given in Table 11.16) show that kokum fat contains high level of SOS (72%). Maheshwari and Reddy (2005) have discussed the application of kokum fat as a cocoa butter improver in chocolate.

11.12.4

Sal fat

Sal (Shorea robusta) trees are grown in two major regions of India, from the central belt and along the foothills of the Himalayas. The state of Madhya Pradesh is the largest sal-growing area. The ripe sal nut consists of 48% kernel, 30% shell and 22% wing. The kernel contains

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Table 11.16 Typical symmetrical monounsaturated triacylglycerols (%) of selected fats and of fractions suitable for use in cocoa butter equivalents (CBE). Fat type Cocoa butter Palm fraction* Shea fraction** Illipe butter Sal fraction** Kokum butter Mango kernel fraction**

POP

POS

SOS

16 66 1 7 tr tr 1

37 12 7 24 10 6 16

26 3 74 45 60 72 59

Total 79–82§ 80–81 78–82 76–88 70 78 76

Notes: * mid-fraction/double fractionation. ** stearin (hard/higher-melting) fraction. § Lidefelt (2007). Key: O = oleic acid P = palmitic acid S = stearic acid tr = trace

14–16% fat, and the crude fat (obtained by solvent extraction) is dark greenish in colour. Special care is taken in chemical refining of the strong green colour fat to produce a lightcoloured fat normally required for chocolate and confectionery products. The main fatty acids of sal fat comprise 5% palmitic (P), 44% stearic (S), 40% oleic (O), 2% linoleic and 4% arachidic (A). The sal fat has a melting point of 30–36 °C and an iodine value range of 31–45 (Firestone 1999). The main triacylglycerols molecular species of sal fat contain 11% POS, 42% SOS, 16% SOO, 13% SOA, 3% OOO and 4% AOO. Sal fat contains 0.6–1.3% unsaponifiable matter, 600–4300 mg/kg of total sterols (62% ß-sitosterol, 15% stigmasterol, 15% campesterol, and 3% Δ5-avenasterol) and tocopherols content 100 mg/kg, 80% α-tocopherol (Lidefelt 2007). Sal fat is rich in symmetrical triglycerides of the SOS and SOA types. Fractionation of sal fat is needed to concentrate the cocoa butter resembling symmetrical monounsaturated triglycerides that provide a useful ingredient for CBEs (Table 11.16).

11.12.5

Shea butter

Shea nuts are obtained from a tree (Butyrospermum parkii) which grows wild in West Africa, Upper Volta and Uganda. Shea nuts, sun-dried to a moisture content of about 8%, are exported from Nigeria, Benin, Togo, Ghana, Ivory Cost, Burkina Faso and Mali to the EU, Japan and the USA for fat extraction and processing. The nut contains 40–55% edible fat. The main fatty acids of shea nut fat comprise 4–8% palmitic (P), 36–42% stearic (S), 45–50% oleic (O) and 4–8% linoleic (L). The shea fat has a melting point of 32–45 °C and the iodine value range is 52–66 (Firestone 1999). The main triacylglycerols molecular species of shea fat contain 3% POP, 6% POS, 42% SOS, 26% SOO, 5% SOL, 5% SLS and 6% OOO (Lidefelt 2007). Shea butter is known to have the highest unsaponifiable matter content (up to 10%) of any natural fat. These unsaponifiables, non-glyceride components, comprise a mixture of hydrocarbons, triterpene esters, phytosterols and a small amount of tocopherols, 100 mg/kg.

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The tocol content is affected by the climate under which the shea tree grows (Anon 2004; Maranz and Wiseman 2004). The triterpene alcohol fraction of shea fat comprises 27% α-amyrin, 10% ß-amyrin, 22% lupeol and 25% butyrospermol (Alandar 2004). These alcohols occur mainly as esters with fatty acids or cinnamic acid and are bioactive components used in cosmetic products. The total sterols of 2470 mg/kg contain no commonly occurring ß-sitosterol, but comprise 38% Δ7-stigmastenol, 11% Δ7-avenasterol, 6% 24-methylΔ7-cholestanol, 45% Δ7, 22,-stigmastadien-3ß-ol. The shea butter is processed to remove the undesirable unsaponifiable components (triterpenes) and solvent fractionated to give hard and soft fats. The hard stearin fraction can be used as a component in a CBE formulation (Table 11.16).

11.12.6

Mango kernel fat

The mango (Mangofera indica) tree grows mainly in central areas of India, and to a smaller extent in Pakistan, Mexico, Brazil, China and Indonesia. The mango kernel has a fat content of around 10–15%. The main fatty acids of mango fat comprise 4–12% palmitic (P), 31–48% stearic (S), 38–50% oleic (O), 3–6% linoleic (L) and 2–6% arachidic (A). The melting point of the fat is 34–43 °C, and iodine value ranges from 39 to 48 (Firestone 1999). The main triacylglycerols molecular species of mango fat contain 11% POS, 40% SOS, 23% SOO, 5% POO, 4% SOA, 5% OOO and others (Lidefelt 2007). The fat contains 1.3–3% unsaponifiable matter, and up to 10 000 mg/kg of total sterols. The suitable stearin fraction of mango fat, rich in POS and SOS (Table 11.16), is a valuable ingredient in CBE formulation. The liquid fraction and the mango fat are also used in other applications such as edible oil and cosmetic products.

11.13

OILS CONTAINING g-LINOLENIC ACID (GLA) AND STEARIDONIC ACID (SDA)

Gamma linolenic acid (GLA) is an isomer of α-linolenic acid and is an n-6 fatty acid, all cis-6,9,12-octadecatrienoic acid. GLA is obtained from vegetable oils such as evening primrose oil, blackcurrant seed oil, borage oil and hemp seed oil. Hemp seed oil contains only a small amount of GLA (∼4%), but the other three oil seeds are commercially important sources of GLA. The oil from a particular seed type may be extracted by any of the four methods: cold pressing, supercritical carbon dioxide, hexane solvent extraction or enzymatic process. Generally, cold pressing and/or supercritical carbon dioxide extraction are used to alleviate concerns about the presence of solvent residues. Enzymatic digestion enhances oil yield in cold pressing. Clough (2001) has reviewed the production and uses of these GLA oils with health-beneficial properties.

11.13.1

Evening primrose oil

GLA was first isolated from the seed of evening primrose. Evening primrose is grown in many European countries, New Zealand and China (now the main producer). The oil content of evening primrose seed (Oenothera biennis) is about 25% (Ghasemnezhad et al. 2006). The oil contains about 10% GLA (range 7–14%), 8% saturated fatty acids, 9% oleic and 72% linoleic acid. Typical fatty acid composition and some physical characteristics of the various GLA-containing oils are presented in Table 11.17a. The major triacylglycerol

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Table 11.17a Characteristics and fatty acid composition of GLA-containing oils: Evening primrose oil (EPO), borage oil (BO) and blackcurrant seed oil (BCO). Fatty acid figures are typical results and accepted range of values. Parameter

EPO

BO

BCO

Refractive index (20 °C) Iodine value Saponification value Unsaponifiable matter (g/100 g)

1.479* 147–155 193–198 1.5–2.0

– 141–160* 189–192 1.2–1.9

1.479–1.481* 173–182 185–195 1.0

Fatty acid (% wt) 14:0 16:0 18:0 18:1 18:2 18:3 ALA 18:3 GLA 18:4 SDA 20:1 Others

– 0.1* 6.0**; 6–10 1.6; 1.5–3.5 8.9; 5–12 73.8; 65–80 0.1; 0.2 9.5; 8–14 –– 0.3; 0.2 0.7; 0.8

0.1; 0.1 11.9**; 9.4–11.9 4.3; 2.6–5.0 18.8; 14.6–21.3 38.5; 36.5–40.1 0.4; 0.2 21.9; 17.1–25.4 – 0.2 3.9; 2.9–4.1 3.6**; 3.7–8.0*

– 0.1 6.3**; 6–8 2.0; 1–2 15.3; 9–13 48.3; 45–50 11.9; 12–15 12.9; 14–20 1.9; 2–4 1.0; 0.9–1.0 0.3; 0.4

Sources: * Firestone (1999); ** Dubois et al. (2007). Notes: Also contains *1.8–2.8% 22:1 and 1.2–4.5% 24:1; ** 2.1% 22:1 and 1.2% 24:1. Key: ALA = α-linolenic acid 18:3n-3 SDA = stearidonic acid 18:4n-3

molecular species of evening primrose oil (EPO) comprise LLL 54.3%, LLG 17.6%, LLO 13.7% and LLP 7.9%, where the symbols P, S, O, L are as described above and G represents GLA (Yang et al. 2003). Cold-pressed EPO contains about 5% minor components, including 1.5–2% unsaponifiable matter, phytosterols, tocopherols, triterpenes and caffeoyl esters. The latter components are progressively removed during refining of the oil (Knorr and Hamburger 2004). The major sterol of the oil is ß-sitosterol 89% and the main tocol is γ-tocopherol, 187–358 mg/kg (Table 11.17b).

11.13.2

Borage oil

Borage oil is produced from borage seed (Borage officinalis), a plant with blue star-shaped flowers. Borage is native to the Mediterranean region of Europe and Northern Africa and is naturalised in many parts of North America. Borage oil (also known as starflower oil) is the richest source of γ-linolenic acid 25%, range 20–27%. The oil content of borage seed is 30–40%, and the fatty acids of the oil comprise 15% saturated, 25% monounsaturated and 59% polyunsaturated acids. Typical fatty acid composition and some physical characteristics of borage oil are presented in Table 11.17a. The major triacylglyceol molecular species of borage oil (BO) comprise LLG 15.4%, OLG 12.3%, LLL 10.1%, LGG 9.8%, PLG 9.5%, PLL/OOG 8.9%, OLL 8.2%, SLG/POG 5.0%, LLE 4.1% and OOL 4.1%, where the symbols P, S, O, L and G are as described above and E represents eicosenoic acid 20:1 (Yang et al. 2003). The major sterols of BO are campesterol, ß-sitosterol, Δ5-avenasterol, and 24-methlene cholesterol. γ-Tocopherol 690–1013 mg/kg is the main tocopherol antioxidant

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Vegetable Oils in Food Technology Table 11.17b Sterol composition and tocopherol content of GLA-containing oils: Evening primrose oil (EPO), borage oil (BO) and blackcurrant seed oil (BCO). Sterols composition (% of total sterols) Cholesterol Brassicasterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol

EPO

BO

– – 8–9 – 87–90 4 2 –

– 0–1.6 25–30 – 22–42 15–28 – 1.0

–

15–20

Other sterols 24-Metylene-cholesterol

BCO 0.2–07 – 7.2–10.4 0.5–1.0 70–85 2–3 0.4–4.5 0.4–2

Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol

76–356 – 187–358 0–19

0–46 – 33–272 690–1013

320 8 647 68

Total tocopherols

263–661

732–1111

1043

Source: Firestone (1999).

(Table 11.17b). Because of the potential heath benefits of GLA, several researchers have attempted to produce GLA concentrate from borage oil. For example, under optimum conditions, a concentration of 91% GLA was obtained from borage oil by urea fractionation (Spurvey and Shahidi 2007).

11.13.3

Blackcurrant seed oil

Blackcurrant seed oil is a by-product of the blackcurrant juice and jelly industry. Blackcurrant (Ribes nigrum) seed oil is of interest and of high value because it contains GLA (12–15%) and stearidonic acid (2–4%), which are important metabolites of linoleic and linolenic acids respectively. The oil content of blackcurrant seed is about 16%, and the fatty acids of the oil comprise 8% saturated, 16% monounsaturated and 75% polyunsaturated acids (Dubois et al. 2007). Typical fatty acid composition and some physical characteristics of blackcurrant seed oil (BCO) are presented in Table 11.17a. The major sterols of BCO is ß-sitosterol 70–85%, and the main tocopherols are α- and γ-tocopherols at 320 and 647 mg/kg respectively (Table 11.17b. In addition, the presence of phenolic antioxidants such as catechin, epicatechin, gallic, rosamarinic, sinapic and syringic acids has been reported in borage oil (Shahidi 2000; Wettasinghe et al. 2002).

11.13.4

Stearidonic acid oils

Stearidonic acid (SDA) is described as an n-3 fatty acid, all cis-6,9,12,15-octadecatetraenoic acid (18:4, n-3). Dietary sources of this fatty acid are the seed oils of hemp (2–3%) and blackcurrant (2–4%). The seed oils of many plant species of the Boraginaceae family (e.g. Eachium plantagineum) contain stearidonic acid between 10% and 20% (Tsevegsuren and

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Aitzetmuller 1996; Cisowski et al. 2001). The seed oil of Hackelia deflexa was found to contain 21.4% of SDA, while the oil from seed (Primulaceae florindae) contains stearidonic acid at the level of 10–15% (Aitzetmuller and Werner 1991). The oil contents of the various seeds vary from 10% to 25%. The fatty acid composition of Echium seed oil contains 6% palmitic acid, 3% stearic acid, 14% oleic acid, 13% linoleic acid, 33% linolenic acid, 12% GLA, 17% SDA,and 2% others. These data clearly shows that the oil is highly unsaturated oil, with 62% of the fatty acids containing 3 and 4 double bonds (Gunstone et al. 2007). Normally, the supercritical fluid-extraction method is recommended for the production of this highly unsaturated oil because it proceeds at low temperatures, and provides an oxygenfree atmosphere to minimise oxidation. Guil-Guerrero (2009) reviewed the nutritional significance, medical uses and natural sources of stearidonic acid. Starling (2009) has reported that Echium oil, derived from E. plantagineum, has been given novel food ingredient approval by the EU. Recently, the results of a small study on 152 human subjects have shown that ingestion of SDA-enriched soybean oil (modified through biotechnology) increased the levels of eicosapentaenoic acid (EPA: 20:5n-3) by 17.7% and reduced fasting triacylglycerols by 26–30% in red blood cells (Anon 2010).

11.13.5

Nutritional and health benefits of GLA and SDA oils

Numerous clinical trial studies suggest that there is good evidence to show the positive beneficial effects of γ-linolenic acid oils and stearidonic acid in treating or preventing several human diseases. These health effects include alteration of plasma lipid profiles, reducing the risk of coronary atherosclerotic heart disease, platelet aggregation, rheumatoid arthritis, dermatitis and blood pressure (Guivernau et al. 1994; Deferne and Leeds 1996; Zurier et al. 1996). For example, eight-week supplementation with blackcurrant seed oil (BCO) significantly decreased plasma total cholesterol and LDL cholesterol levels and increased plasma HDL cholesterol levels in hyperlipidemic patients (Spielmann et al. 1989). BCO also reduced the tendency of human platelets to aggregate (Kockmann et al. 1989). Other healthpromoting properties of GLA-rich oils are associated with immune function, premenstrual syndrome, cancer, gastric ulceration, asthma, hot flushes in menopause, inflammation and weight management. Schirmer and Phinney (2007) reported that obese subjects given 890 mg/d GLA in the form of dietary borage oil supplement managed to stabilise weight, although the precise mechanism for this was not elucidated. The dose-related effects of GLA or of GLA-containing oils and possible/potential mechanisms for the health benefits have been reviewed extensively by some workers (Whelan et al. 2006; Barre 2009).

11.14

TREE NUT OILS

There is a long list of tree nut kernels produced and consumed around the world. Most commonly consumed nuts include almond, cashew, chestnut, Brazil, hazel, macadamia, pecan, pine, pistachio and walnut. The various species differ in the hardness of their shells (KamalEldin and Moreau 2009). For example, the shells of macadamia, hazel and walnuts are hard. Before oil extraction, the nuts are lightly toasted for about 20 minutes, shells cracked, and nut kernels are usually removed manually. Cold pressed, at a temperature not more than 30 °C, nut oils have a superior nutty flavour and are fresh in taste, and are often used for salad dressings, in the cooking of speciality dishes and other food applications. Nut oils are

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also extracted from the nuts by a supercritical extraction process using carbon dioxide in wide temperature and pressure ranges (Salgin and Salgin 2006; Silva et al. 2008). Carbon dioxide-extracted oils are generally clearer and may contain more tocopherols and be slightly more stable than oils extracted with hexane solvent. However, Martinez et al. (2008) found that despite the high content of tocopherols in CO2-extracted oils, their oxidative stability seemed to be lower that those extracted with solvent. The meal remaining after cold pressing may be sold for applications such as speciality baking goods and energy bars. Hexane solvent is generally used for extraction of nut kernels of low quality and the cake of expeller-pressed oils. Lower-quality oil is generally refined by traditional refining steps. The refined nut oils lose their characteristic nutty flavour but are better suited for higher-temperature applications. Nut kernel oils are also widely used in massages and lubricants, several pharmaceuticals, and many cosmetic products such as creams, skin lotions, hair conditioners and shampoos.

11.14.1

Brazil nut kernel oil

The Brazil nut tree is native to the Amazonian regions of South America, including Brazil, Bolivia, Columbia, Ecuador, Peru and Venezuela. The kernels are a staple food for many people in the producing countries. They contain about 70% oil, 18% protein and 12% carbohydrates, and are a good source of selenium (Thomson et al. 2008). The lipid composition of Brazil nut (Bertholletia excelsa) oil comprises triacylglycerols 96.7%, phospholipids 0.69% and sphingolipids 0.83% (Miraliakbari and Shahidi 2008). The oil contains unsaponifiables 0.44–0.66%, free sterols 0.18%, sterol esters 0.05%, squalene 1378 mg/kg and tocopherols 199 mg/kg. The major fatty acids of the oil are 14% palmitic (P), 12% stearic (S), 29% oleic (O) and 43% linoleic (L) acid. Typical fatty acid composition and some characteristics of Brazil nut oil are presented in Table 11.18a. Triacylglyceol molecular species of the oil comprise LLL 14.8%, OLL 16.7%, LLP 13%, OLO 13.1%, LOP 16.7%, PLP 2.6%, OOO 4.6%, SLO 10% and SOO 2.3% (Holcapek et al. 2003). The major sterol of the oil is typically ß-sitosterol (1325 mg/kg), followed by lower levels of stigmasterol (577 mg/kg) and campesterol (27 mg/kg) (Ryan et al. 2006). A small amount of cholesterol (1–2% of total sterols) is also present in the Brazil nut oil (Table 11.18b).

11.14.2

Hazel nut oil

The hazel nut (Corylus avellana L.) tree, a member of the birch family, Betulaceae, is an important commercial crop in many countries, including Turkey (largest producer), Iran, Spain, Italy, Australia, New Zealand, Chile and the USA. Hazel nut (also known as cob nut) kernels contain approximately oil 60%, protein 18% and carbohydrates 15%. Raw or roasted hazel nut kernels have a characteristic flavour and are edible. The nut kernels are extensively used in the chocolate and confectionery industry. The lipid composition of hazelnut oil comprises triacylglycerols 98%, phospholipids 0.59% and sphingolipids 0.26% (Miraliakbari and Shahidi 2008). The oil contains unsaponifiables 0.2–0.3%, free sterols 0.21%, sterol esters 0.04%, squalene 186 mg/kg and tocopherols 371 mg/kg (Maguire et al. 2004). Crews et al. (2005) reported considerable variations in the levels of sterols, tocopherols and fatty acids in hazel nut oil samples from France, Italy, Spain, Croatia and Turkey. The major fatty acids of the oil are 6% palmitic (P), 3% stearic (S), 79% oleic (O) and 10% linoleic (L) acid,

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Table 11.18a Characteristics and fatty acid composition of selected nut oils: Brazil nut oil (BNO), hazel nut oil (HNO), macadamia nut oil (MNO) and walnut oil (WNO). Parameter Refractive index* (25 °C) Iodine value* Saponification value* Unsaponifiable matter* (g/100 g) Fatty acid (% wt) 14:0 16:0 16:1 18:0 18:1 18:2 18:3 ALA 20:0 20:1 Others Induction period† at 100 °C (h) (by Rancimat)

BNO

HNO

MNO

WNO

1.464–1.468

1.469–1.476

–

1.472–1.475

97–106 197–202 1

83–90 188–197 0.2–0.3

– – –

138–162 189–197 0.5

0.1**; 0.6* 13.5; 14–16 0.3; 0.3 11.8; 6–10 29.1; 29–48 42.8; 30–47 0.2 0.5; 0.3 0.2 1.5

0.1§ 5.8; 4.1–7.2* 0.3; 0.1–0.3 2.7; 1.5–2.4 79.3; 71.9–84 10.4; 5.7–22.2 0.5; 0.0–0.2 0.2; 0.1 0.1–0.3 0.9; 1–1.6¶

–

16

Typical and range 1.0§; 0.6* 8.4; 8–9 17.3; 21–22 3.2; 2–4 65.1; 56–59 2.3; 2–3 0.1 2.3; 2–3 1.5–3 0.3; 1.7

0.1§ 6.7; 7–8* 0.2; 0.1–0.2 2.3; 1.8–2.2 21.0; 17–19 57.5; 56–60 11.6; 13–14 0.1; 0.1 0.2 0.5; 0.1

37

4.2

Sources: * Firestone (1999); ** Ryan et al. (2006); § Maguire et al. (2004); † Kochhar and Henry (2009). Key: ALA = α-linolenic acid 18:3n-3; ¶ contains 0.9–1.2% 18:1n-11 (cis-vaccenic acid) wt = weight

which is very similar to the fatty acid composition of olive oil. That is why virgin olive oil is sometimes adulterated with hazel nut oil, and the detection of this adulteration is rather difficult at low levels. The typical fatty acid composition and some characteristics of hazel nut oil are presented in Table 11.18a. The main triacylglycerol molecular species of the oil comprise LLL 3.7%, OLL 12.3%, LLP 1.6%, OLO 28.2%, LOP 5.2%, OOO 36.5%, SLO 1.4%, OOP 6.1% and SOO 2.8% (Holcapek et al. 2003). The major sterol of the oil is typically ß-sitosterol (991 mg/kg), followed by lower levels of campesterol (67 mg/kg) and stigmasterol (38 mg/kg) (Maguire et al. 2004). The tocopherols of hazel nut oil are mainly α-tocopherol (310 mg/kg) which is about five times higher than γ-tocopherol (Maguire et al. 2004). Interestingly, there are many cultivars of the hazel, and some cultivars are of hybrids between common hazel and filbert. The Chilean hazelnut is incorrectly named and comes from different species (Gevuina avellana). The oil has a very different fatty acid profile, which contains 87.5% monounsaturated fatty acids (Firestone 1999).

11.14.3

Macadamia nut oil

The macadamia nut from an evergreen tree is native to Australia, and the nuts are a valuable food crop. Two edible species, Macadamia integrifolia and M. tetraphylla and their hybrids, are of commercial importance. Australia is the world’s largest producer of the nuts, although

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Table 11.18b Sterol composition and tocopherol contents of selected nut oils: Brazil nut oil (BNO), hazel nut oil (HNO), macadamia nut oil (MNO) and walnut oil (WNO). Parameter

BNO

HNO

MNO

WNO

1** 1.4*; 2 29.9; 9 68.7; 85 – 2 –

0–0.7** 5–6 1 82–93 2–8 1–3 2–3

– 4.5§ 2.3 93.1 – – –

– 5** – 89 5 – –

Total sterols (mg/kg)

1929*

1200–2000

1618

1760

Tocopherols (mg/kg) α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol α-Tocotrienol γ-Tocotrienol δ-Tocotrienol Total tocopherols (mg/kg)

83* – 116 – – – – 199

87†; 200–409** 12; 6–17 54; 18–150 nd; 1–7 nd 176 tr 329; 225–583

8†; 122§ nd 15; tr 11 20 nd nd 54; 122

71†; 10–20** nd 259; 263–400 43; 46–60 nd nd nd 373; 309–455

Sterols composition (% of total sterols) Cholesterol Campesterol Stigmasterol β-Sitosterol Δ5-Avenasterol Δ7-Stigmastenol Δ7-Avenasterol

Sources: * Ryan et al. (2006); ** Firestone (1999); § Maguire et al. (2004); † Madawala et al. (2010). Key: nd = not detected tr = trace

they are also produced in New Zealand, South Africa, Malawi, Kenya, Bolivia, Costa Rica, Brazil and the USA (Hawaii). The macadamia nut kernels contain 65–75% oil, 9% protein and 9% carbohydrates. They also contain 2% dietary fibre, with calcium, phosphorus, potassium, selenium, iron, thiamine, riboflavin and niacin. The main fatty acids of the oil are 1% myristic (M), 8% palmitic (P), 17% palmitoleic (Po), 3% stearic (S), 65% oleic (O), 2% linoleic (L) and 2% arachidic (A) acid, which makes the oil high in monounsaturated fatty acids (MUFA, 82%) and low in linoleic acid, making it a very stable oil. It is one of the richest sources of palmitoleic acid. The oil contains unsaponifiables 0.30–0.33%, including sterols 1618 mg/kg, squalene 185 mg/kg, and α-tocopherol 122 mg/kg as the major tocol (Maguire et al. 2004). The main triacylglyceol molecular species of the oil comprise PoLPo 1.3%, PoPoPo 2.6%, PoPoM 1.2%, OLPo 3.9%, PoOPo 8.2%, OPoM 1.7%, PPoPo 2.6%, PPoM 1.0%, POPo 6.1%, OOPo 16.1%, OLO 6.4%, LOP 2.7%, OOO 19.4% and OOP 9.9% (Holcapek et al. 2003). The major sterol of the oil is typically ß-sitosterol (1507 mg/kg), with lower levels of campesterol (73 mg/kg) and stigmasterol (38 mg/kg) (Maguire et al. 2004). Because of its high oxidative stability macadamia nut oil has an induction period of 37 h at 100 °C (Kochhar and Henry 2009). The oil is widely used for cosmetic products, especially for skin care. The subtle nutty flavour of macadamia nut oil makes it an excellent oil for salad dressings and for stir-frying due to its high smoke point. It imparts a delightful buttery flavour to baked goods, and is especially good on popcorn. Macadamia nut oil is the most monounsaturated edible oil and is used as a food supplement because of the growing appreciation of the beneficial effects of MUFA, including palmitoleic acid.

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11.14.4

331

Walnut oil

The walnut tree is grown throughout the world, but the Persian walnut (Juglans regia) tree provides the nuts most commonly used for edible purposes. It is grown in the temperate regions of the world, with the major producing countries including Iran, Afghanistan, Armenia and Greece. The walnut kernels contain about 60–65% oil, 15–24% protein and 10–14% carbohydrates. The lipid composition of walnut oil comprises triacylglycerols 97.2%, phospholipids 0.96% and sphingolipids 0.54% (Miraliakbari and Shahidi 2008). The oil contains unsaponifiables 0.25–0.4% (free sterols 0.26%, sterol esters 0.09%, squalene 9 mg/kg and tocopherols 321 mg/kg). Crews et al. (2005) reported considerable variations in the levels of sterols, tocopherols and fatty acids in walnut oil samples from China, India, France, Hungary, Italy, Spain and the USA. Walnut oil is a highly unsaturated oil containing both linoleic (50–60%) and linolenic acids (13–15%). The major fatty acids of the oil are 7% palmitic (P), 2% stearic (S), 21% oleic (O), 58% linoleic (L) and 12% linolenic (Ln) acid. Typical fatty acid composition and some characteristics of walnut oil are presented in Table 11.18a. The main triacylglyceol molecular species of the oil comprise LLnLn 2.1%, LLLn 20.0%, LLL 34.6%, OLLn 4.6%, LnLP 3.1%, OLL 17.2%, LLP 10.6%, OLO 3.1% and LOP 4.2% (Amaral et al. 2003). The major sterol of the oil is typically ß-sitosterol (1129 mg/kg), followed by lower levels of campesterol (51 mg/kg) and stigmasterol (55 mg/kg) (Maguire et al. 2004). The sterol composition of walnut oil was reported earlier: 89% ß-sitosterol, 5% campesterol, 5% stigmasterol and total sterols 1760 mg/kg (Firestone 1999). The ranges of α-, γ-, and δ-tocopherols are 10–20, 263– 400 and 40–60 mg/kg respectively, and the total tocopherols content range is 309–455 mg/kg (Table 11.18b). Walnut oil is a good source of n-3, α-linolenic acid. It is light coloured and has a delicate nutty flavour and aroma. It is used as a gourmet oil in Japan, France and many other countries. It should be pointed out that the bottled walnut oil should be stored in the dark and consumed in a couple of months because of its short shelf-life (Kochhar and Henry 2009).

11.14.5

Health benefits of nuts and nut lipids

During the last few years, several studies have provided strong evidence that the consumption of nuts and nut oils has beneficial effects on CHD risk (Kris-Etherton et al. 2001; Hyson et al. 2002; Sheridan et al. 2007). For example, controlled clinical trials showed significant reductions in serum total and LDL cholesterol concentrations in normal and hyper-cholesterolemic subjects by the consumption of nuts including macadamia nuts (Garg et al. 2003; Griel et al. 2008); hazelnuts (Durak et al. 1999) and walnuts (Almario et al. 2001; Morgan et al. 2002). It is now possible (FDA 2003) to claim: ‘Scientific evidence suggests but does not prove that eating 1.5 ounces [∼42 g] per day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.’ Other health aspects of dietary nuts and nut oils are associated with stroke, type 2 diabetes, suppressing appetite, advanced macular degeneration, gallstones and dementia. More clinical trials and investigations are needed to provide evidence for these health-promoting properties of various nut oils and their active minor constituents.

REFERENCES Abe, C., Ikeda, S. and Yamashina, K. (2005) Dietary sesame seeds elevate β-tocopherol concentration in rat brain, Journal of Nutritional Science and Vitaminology, 51, 223–230.

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Abramovic, H. and Abram, V. (2005) Physico-chemical properties, composition and oxidative stability of Camelina sativa oil, Food Technology and Biotechnology, 43, 63–70. Abramovic, H. and Abram, V. (2006) Effect of added rosemary extract on oxidative stability of Camelina sativa oil, Acta Agriculturae Slovenica, 87, 255–261. Abramovic, H., Butinar, B. and Nikolic, V. (2007) Changes occurring in phenolic content, tocopherol composition and oxidative stability of Camelina sativa oil during storage, Food Chemistry, 104, 903–909. Aitzetmüller, K. and Werner, G. (1991) Stearidonic acid (18:4n-3) in Primula florindae, Phytochemistry, 30, 4011–4013. Alandar, J. (2004) Shea butter – a multifunctional ingredient for food and cosmetics, Lipid Technology, 19, 202–205. Albert, C.M., Oh, K., Whang, W. et al. (2005) Dietary alpha-linolenic acid intake and risk of sudden cardiac death and coronary heart disease, Circulation, 112, 3232–3238. Almario, R.U., Vonghavaravat, V., Wong, R. and Kasim-Karaka, S.E. (2001) Effects of walnut consumption on plasma fatty acids and lipoproteins in combined hyperlipidemia, American Journal of Clinical Nutrition, 74, 72–79. Amaral, J.S., Casal, S., Pereira, J.A., Seabra, R.M. and Oliveira, B.P. (2003) Determination of sterol and fatty acid compositions, oxidative stability, and nutritional value of six walnut (Juglans regia L.) cultivars grown in Portugal, Journal of Agricultural Food Chemistry, 51, 7698–7702. Anon. (2004) Climate influences the tocopherol content of shea butter, Lipid Technology, 16, 191. Anon. (2010) More data on SDA to EPA conversion, INFORM, 21, 27 and 41. AOCS (2007) Official method Ce 11a-07, Cocoa butter equivalents in milk chocolate by GC, American Oil Chemists’ Society, Urbana, IL. Aued-Pimental, S., Takemoto, E., Antoniassi, R. and Gastaldo Badolato, E.S. (2006) Composition of tocopherols in sesame seed oil: An indicative of adulteration, Grasas y Aceites, 57, 205–210. Barre, D.E. (2009) Borage, evening primrose, blackcurrant, and fungal oil: γ-Linolenic acid-rich oils, In Gourmet and Health Promoting Speciality Oils (eds R.A. Moreau and A. Kamal-Eldin), AOCS Press, Urbana, IL, pp. 237–266. Bedigian, D. (1984) Sesamum indicum, L., Crop Origin, Diversity, Chemistry and Ethnobotony, PhD Thesis, University of Illinois, Urbana-Champaign, USA. Bennani, H., Drissi, A., Giton, G. et al. (2007) Antiproliferative effect of polyphenols and sterols of virgin argan oil on a human prostate cancer cell lines, Cancer Detection and Prevention, 31, 64–69. Berglund, D. (2002) Flax: New uses and demands, in Trends in New Crops and Uses (eds J. Janick and A. Whipkey), ASHS Press, Alexandria, VA, pp. 258–360. Berrougui, H., Cloutier, M., Isabelle, M. and Khalil, A. 2006 Phenolic extract from argan oil (Argania spinosa L.) inhibits low-density lipoprotein (LDL) oxidation and enhances cholesterol efflux from human THP-1 macrophages, Atherosclerosis, 184, 389–396. Beveridge, T.H.J., Girard, B., Kopp, J. and Drover, J.C.G. (2005) Yield and composition of grape seed oils extracted by supercritical carbon dioxide and petroleum ether: Varietal effect, Journal of Agricultural Food Chemistry, 53, 1799–1804. Bhattacharyya, A.C., Majumdar, S. and Bhattacharyya, D.K. (1986) Edible quality rice bran oil from high FFA rice bran oil by miscella refining, Journal of the American Oil Chemists’ Society, 63, 1189– 1191. Bhosle, B. and Subramanian, R. (2005) New approaches in deacidification of edible oils – a review, Journal of Food Engineering, 69, 481–494. Brar, G.S. (1977) Variability in the fatty acid composition of sesame seed (Sesamum indicum, L.) due to the capsule position on the plant and the seed position in the capsule, Crop Improvement, 4, 1–10. Brar, G.S. (1980) Effect of temperature on fatty acid composition of sesame (Sesamum indicum, L.), Plant Biochemistry Journal, 7, 133–137. Bravi, M., Spinoglio, E., Verdone, N. et al. (2007) Improving the extraction of α-tocopherol-enriched oil from grape seeds by supercritical CO2. Optimisation of the extraction conditions, Journal of Food Engineering, 78, 488–493. Buchgraber, M. and Androni, S. (2007) Gas-liquid chromatographic determination of milk fat and cocoa butter equivalents in milk chocolate: Interlaboratory study, Journal of AOAC International, 90, 1326– 1339. Buchgraber, M., Androni, S. and Anklam, E. (2007) Quantification of milk fat in chocolate fats by triacylglycerol analysis using gas-liquid chromatography, Journal of Agricultural Food Chemistry, 55, 3275– 3283.

Gunstone_c11.indd 332

1/21/2011 7:16:28 PM

Minor and Speciality Oils

333

Budin, J.T., Breene. W.M. and Putman, D.H. (1995) Some compositional properties of camelina (Camelina sativa L. Crantz) seeds and oils, Journal of the American Oil Chemists’ Society, 72, 309–315. Campbell, I. (2002) An exotic tale, Part I: Illipe – the uncertain crop, http://www.nioto-togo.com/spip. php?article28. Campos, H., Baylin, A. and Willett, W.C. (2008) α-Linolenic acid and risk of nonfatal acute myocardial infarction, Circulation, 118, 339–345. Carter, J.F. (1993) Potential of flaxseed and flaxseed oil in baked goods and other products in human nutrition, Cereal Foods World, 38, 753–759. Chang, L.W., Yen, W.J., Huang, S.C. and Duh, P.D. (2002) Antioxidant activity of sesame coat, Food Chemistry, 78, 347–354. Charrouf, Z. and Guillaume, D. (2008) Argan oil: Occurrence, composition and impact on human health, European Journal of Lipid Science and Technology, 110, 632–636. Chen, P.R., Chien, K.L., Su, T.C. et al. (2005) Dietary sesame reduces serum cholesterol and enhances antioxidant capacity in hypercholesterolemia, Nutrition Research, 25, 559–567. Cherki, M., Derouiche, A., Drissi, A. et al. (2005) Consumption of argan oil may have antiatherogenic effect by improving para-oxonase activities, and antioxidant status: Intervention study in healthy men, Nutrition, Metabolism and Cardiovascular Diseases, 15, 352–360. Choo, W., Birch, J. and Dufour, J.P. (2007) Physicochemical and quality characteristics of cold-pressed flaxseed oils, Journal of Food Composition and Analysis, 20, 202–211. Chouinard, P.Y., Corneau, L., Butler, W.R. et al. (2001) Effect of dietary lipid source on conjugated linoleic acid concentrations in milk fat, Journal of Dairy Science, 84, 680–690. Cisowski, W., Zielinska-Stasiek, M., Stolyhwo, A., Migas, P. and Kamieniec, A. (2001) Gas chromatographic analysis of fatty acids obtained from the seeds of some Boraginaceae plants, Acta Chromatigraphia, 11, 215–223. Clevidence, B. (2007) Rice Phytonutrients: Do Realistic Intakes of Rice and Rice Bran Oil Promote Health?, USA Rice Federation, Arlington, VA. Clough, P.M. (2001) Sources and production of speciality oils containing GLA and stearidonic acid, Lipid Technology, 13, 9–12. Codex Alimentarius (1999) (FAO/WHO) Codex Standard for named vegetable oils. CODEX STAN 210 1999 (revision and amendments: 2003, 2005). Crews, C., Hough, P., Godward, J. et al. (2005) Study of the main constituents of some authentic hazelnut oils, Journal of Agricultural Food Chemistry, 53, 4843–4852. Crews, C., Hough, P., Godward, J. et al. (2006) Quantisation of the main constituents of some authentic grape seed oils of different origins, Journal of Agricultural Food Chemistry, 54, 6261–6265. Deckelbaum, R.J., Worgall, T.S. and Seo, T. (2006) n-3 Fatty acids and gene expression, American Journal of Clinical Nutrition, 83, 1520S–1525S. Deferne, J.L. and Leeds, A.R. (1996) Resting blood pressure and cardiovascular reactivity to mental arithmetic in mild hypertensive males supplemented with blackcurrant seed oil, Journal of Human Hypertension, 10, 531–537. Deshpande, S.S., Deshpande, U.S. and Salunkhe, D.K. (1996) Sesame oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (ed Y.H. Yui), 5th edn, John Wiley & Sons, Inc., New York, pp. 457–495. Dhiman, T.R., Satter, L.D., Pariza, M.W. et al. (2000) Conjugated linoleic acid (CLA) content of milk from cows offered diets rich in linoleic and linolenic acid, Journal of Dairy Science, 83, 1016–1027. Drissi, A., Girona, J., Cherki, M. et al. (2004) Evidence of hypolipemiant and antioxidant properties of argan oil derived from argan tree (Argania spinosa), Clinical Nutrition, 23, 1159–1166. Dubois, V., Breton, S., Linder, M., Fanni, J. and Parmentier, M. (2007) Fatty acid profiles of 80 vegetable oils with regards to their nutritional potential, European Journal of Lipid Science Technology, 109, 710– 732. Durak, I., Koksal, J., Kacmaz, M. et al. (1999) Hazelnut supplementation enhances plasma antioxidant potential and lowers plasma cholesterol levels, Clinica Chimica Acta, 284, 13–115. Eitenmiller, R.R. (1997) Vitamin E content of fats and oils: Nutritional implications, Food Technology, 51, 78–81. Elson, C.E. and Yu, S.G. (1994) The chemoprevention of cancer by mevalonate-derived constituents of fruits and vegetables, Journal of Nutrition, 124, 607–614. Fernie, C.E. (2003) Conjugated linoleic acid, in Lipids for Functional Foods and Nutraceutical (ed. F.D. Gunstone), Oily Press, Bridgwater, pp. 303–305.

Gunstone_c11.indd 333

1/21/2011 7:16:28 PM

334

Vegetable Oils in Food Technology

Firestone, D. (ed.) (1999) Physical and Chemical Characteristics of Oils, Fats and Waxes, AOCS Press, Champaign, IL. FAO (2007) FSTAT, Food and Agriculture Organization, Washington, DC, http://faostat.fao.org. FDA (2003) Summary of Qualified Health Claims Permitted, US Food and Drug Administration, Centre for Food Safety and Nutrition, College Park, MD, http://www.fda.gov/Food/default.htm. Frank, J., Kamal-Eldin, A. and Traber, M. (2004) Consumption of sesame oil muffins decreases the urinary excretion of γ-tocopherol metabolites in humans, Annals of the New York Academy of Science, 1031, 365–367. Fukuda, Y., Nagata, M., Osawa, T. and Namiki, M. (1986a) Contribution of lignan analogues to antioxidant activity of refined unroasted sesame seed oil, Journal of the American Oil Chemists’ Society, 63, 1027– 1031. Fukuda, Y., Nagata, M., Osawa, T. and Namiki, M. (1986b) Chemical aspects of the antioxidative activity of roasted sesame seed oil and the effects of using the oil for frying, Agricultural Biology and Chemistry, 50, 857–862. Fukuda, Y., Osawa, T., Kawagishi, S. and Namiki, M. (1988a) Comparison of contents of sesamolin and lignan antioxidants in sesame seeds cultivated in Japan, Journal of the Japanese Society of Food Science and Technology, 35, 483–486. Fukuda, Y., Osawa, T., Kawagishi, S. and Namiki, M. (1988b) Oxidative stability of foods fried with sesame oil, Journal of the Japanese Society of Food Science and Technology, 35, 28–32. Garg, M.I., Blake, R.J. and Wills, R.B. (2003) Macadamia nut consumption lowers plasma and total LDL cholesterol levels in hypercholesterolemic men, Journal of Nutrition, 133, 1060–1063. Gaur, R., Sharma, A., Khare, S.K. and Gupta, M.N. (2007) A novel process of extraction of edible oils. Enzyme assisted three phase partitioning (EATPP), Bioresource Technology, 98, 696–699. Gertz, C. and Kochhar, S.P. (2001) A new method to determine oxidative stability of vegetable fats and oils at simulated frying temperature, Oleagineux Corps Gras Lipides, 8, 82–88. Ghasemnezhad, A., Cergil, S. and Monermeier, B. (2006) Evening primrose oil (EPO) quality changes dependent on storage temperature and storage time, Plant Medicine, 72, 207. Ghosh, M. (2007) Review of recent trends in rice bran oil processing, Journal of the American Oil Chemists’ Society, 84, 315–324. Gingras, L. (2000) Refining of rice bran oil, INFORM, 11, 1196–1203. Gopala Krishna, A.G. (2000) Nutritional components of unsaponifiable matter in rice bran oil in relation to processing. Paper presented at National Seminar on Rice Bran Oil, organised by the Solvent Extractors’ Association of India, 3 June, Goa, India. Gopala Krishna, A.G., Khatoon, S., Shiela, P.M. et al. (2001) Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil, Journal of the American Oil Chemists’ Society, 78, 127–131. Gordon, M.H. (1989) Plant sterols as natural antipolymerisation agents, in Proceedings of International Symposium, New Aspects of Dietary Lipids – Benefits, Hazards, and Uses, 17–20 September, SIK, Goteborg, Sweden. Gordon, M.H. and Magos, P. (1983) The effect of sterols on the oxidation of edible oils, Food Chemistry, 10, 141–147. Gould, M.N., Haag, J.D., Kennan, W.S., Tanner, M.A. and Elson, C.E. (1991) A comparison of tocopherol and tocotrienol for the chemoprevention of chemically induced rat mammary tumours, American Journal of Clinical Nutrition, 53, 1068–1070. Green, A.G. and Paul Dribnenki, J.C. (1994) Linola – a new premium polyunsaturated oil, Lipid Technology, 6, 29–33. Griel, A.E., Cao, Y., Bagshaw, D.D. et al. (2008) A macadamia nut-rich diet reduces total and LDLcholesterol in mildly hypercholesterolemic men and women, Journal of Nutrition, 138, 761–767. Guil-Guerrero, J.L. (2009) Stearidonic acid (18:4n-3): Metabolism, nutritional importance, medical uses and natural sources, European Journal of Lipid Science Technology, 109, 1226–1236. Guivernau, M., Mexa, N., Barja, P. and Roman, O. (1994). Clinical and experimental study on the long-term effect of dietary gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation and prostacyclin production. Prostaglandins lookout, Essential Fatty Acids, 51, 311–316. Gunstone, F.D. (2006) Minor speciality oils, in Nutraceutical and Speciality Lipids and their Co-products (ed. E. Shahidi), Taylor & Francis, Boca Raton, FL, pp. 91–126. Gunstone, F.D., Harwood, J.L. and Dijkstra, A.J. (eds) (2007) The Lipid Handbook, 3rd edn, CRC Press/ Taylor & Francis, Abingdon, pp. 69–91.

Gunstone_c11.indd 334

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Minor and Speciality Oils

335

Han, J.H. and Ahn, S.Y. (1993) Effect of oil refining processes on oil characteristics and oxidation stability of sesame oil, Journal of the Korean Agricultural Society, 36, 284–289. Hanmoungjai, P., Pyle, L. and Niranjan, K. (2000) Extraction of rice bran oil using aqueous media, Journal of Chemical Technology and Biotechnology, 75, 348–352. Hartman, L. and Dos Reis, M.I.J. (1976) A study of rice bran oil refining, Journal of the American Oil Chemists’ Society, 53, 149–151. Haumann, B.F. (1990) Low-linolenic flax: Variation on familiar oilseed, INFORM, 1, 934–945. Hernandez, N., Rodriguez-Alegria, M.E., Gonzalez, F. and Lopez-Mungui, A. (2000) Enzymatic treatment of rice bran to improve processing, Journal of the American Oil Chemists’ Society, 77, 177–180. Hirata, F., Fujita, K., Ishikura, Y. et al. (1996) Hypercholesterolemic effect of sesame lignan in humans, Atherosclerosis, 122, 135–136. Holcapek, M., Jandera, P., Zderadicka, P. and Hruba, L. (2003) Characterisation of triacylglycerol and diacylglycerol composition of plant oils using high-performance liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry, Journal of Chromatography, 1010, 195–215. Hyson, D.A., Schneeman, B.O. and Davis, P.A. (2002) Almonds and almond oil have similar effects on plasma lipids and LDL oxidation in healthy men and women, Journal of Nutrition, 132, 703–707. Hwang, L.S. (2005) Sesame oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (ed. F. Shahidi), 6th edn., John Wiley & Sons, Inc., New York, pp. 537–574. INFORM (1998) Solin oil accepted for food use in United States, INFORM, 9, 628. Iqbal, J., Minhajuddin, M. and Beg. J.H. (2004) Suppression of diethyl nitrosamine and 2-acetylaminofluorene-induced hepatocarcinogenesis in rats fed tocotrienol-rich fraction isolated from rice bran oil, European Journal of Cancer Prevention, 13, 515–520. ISO (2006) 23275-2. Animal and vegetable fats and oils – Cocoa butter equivalents in cocoa butter and plain chocolate, Part 2: Quantification of cocoa butter equivalents, International Organization for Standardization, Geneva. Johnson, L.A., Suleiman, T.M. and Lusas, E.W. (1979) Sesame protein: A review and prospectus, Journal of the American Oil Chemists’ Society, 56, 463–468. Juliano, B.O. (ed.) (1985) Rice: Chemistry and Technology, 2nd edn, American Association of Cereal Chemists, St. Paul, MN. Kallio, H., Yang, B., Peippo, P., Tahnonen, R. and Pan, R. (2002) Triacylglycerols, glycerophospholipids, tocopherols and tocotrienols in berries and seeds of two subspecies (ssp sinensis and ssp mongolica) of sea buckthorn (Hippophae rhamnoides), Journal of Agricultural Food Chemistry, 50, 3004–3009. Kamal-Eldin, A. and Appelqvist, L.A. (1994a) Variation in fatty acid composition of the different acyl lipids in seed oils from four Sesamum species, Journal of the American Oil Chemists’ Society, 71, 135–139. Kamal-Eldin, A. and Appelqvist, L.A. (1994b) Variation in the composition of sterols, tocopherols and lignans in seed oils from four Sesamum species, Journal of the American Oil Chemists’ Society, 71, 149– 156. Kamal-Eldin, A. and Moreau, R.A. (2009) Tree nut oils, in Gourmet and Health-Promoting Specialty Oils (eds R.A. Morea and A. Kamal-Eldin), AOCS Press, Urbana, IL, pp. 127–149. Kamal-Eldin, A., Appelqvist, L.A., Yousif, G. and Iskander, G.M. (1992a) Seed lipids of Sesamun indicum and related wild species in Sudan. The sterols, Journal of the Science of Food Agriculture, 59, 327–334. Kamal-Eldin, A., Yousif, G., Iskander, G.M. and Appelqvist, L.A. (1992b) Seed lipids of Sesamum indicum, L. and related wild species in Sudan I: Fatty acids and triacylglycerols, Fat Science Technology, 94, 254–259. Kamel, B.S., Dawson, H. and Kakuda, Y. (1985) Characteristics and composition of melon and grape seed oils and cakes, Journal of the American Oil Chemists’ Society, 62(5), 881–883. Kato, A., Yamaoka, M., Tanaka, A., Komiyama, K. and Umezawa, I. (1985) Physiological effect of tocotrienol, Journal of the Japan Oil Chemists’ Society, 34, 375–381. Katsuzaki, H., Kawakishi, S. and Osawa, T. (1993) Structure of novel antioxidative lignan triglucoside isolated from sesame seed, Heterocycles, 36, 933–936. Katsuzaki, H., Kawakishi, S. and Osawa, T. (1994) Sesaminol glucosides in sesame seeds, Phytochemistry, 35, 773–776. Katsuzaki, H., Kawasumi, M., Kawakishi, S. and Osawa, T. (1992) Structures of novel antioxidative lignan glucosides isolated from sesame seed, Bioscience, Biotechnology and Biochemistry, 56, 2078–2088.

Gunstone_c11.indd 335

1/21/2011 7:16:28 PM

336

Vegetable Oils in Food Technology

Khallouki, F., Younos, C., Soulimani, R. et al. (2003) Consumption of argan oil (Morocco) with its unique profile of fatty acids, tocopherols, squalene, sterols and phenolic compounds should confer valuable cancer chemopreventive effects, European Journal of Cancer Prevention, 12, 67–75. Khotpal, R.R., Kulkarni, A.S. and Bhakare, H.A. (1997) Studies on lipids of some varieties of linseed (Linum usitatissimum) of Ridarbha region, Indian Journal of Pharmaceutical Science, 59, 157–158. Kizil, S., Cakmak, O., Kirici, S. and Inan, M. (2008) A comprehensive study on safflower (Carthamus Tinctorius L.) in semi-arid conditions, Biotechnology and Biotechnological Equipment, 22, 947–953. Klein, V., Chajes, V., Germain, E. et al. (2000) Low alpha-linolenic acid content of adipose breast tissue is associated with an increased risk of cancer, European Journal of Cancer, 36, 335–340. Knorr, R. and Hamburger, R. (2004) Quantitative analysis of anti-inflammatory and radical scavenging triterpenoid esters in evening primrose oil, Journal of Agricultural Food Chemistry, 52, 3319–3324. Kochhar, S.P. (1997) Fats and fatty foods, in Food Industries Manual (eds M.D. Ranken, R.C. Kill and C.G.J. Baker), 24th edn, Blackie Academic & Professional, London, pp. 272–315. Kochhar, S.P. (2000) Sesame oil – A powerful antioxidant, Lipid Technology Newsletter, 6, 35–39. Kochhar, S.P. (2002) Sesame, rice-bran and flaxseed oils, in Vegetable Oils in Food Technology (ed. F.D. Gunstone), Blackwell Publishing Ltd., Oxford, pp. 297–326. Kochhar, S.P. and Henry, C.J. (2009) Oxidative stability and shelf-life evaluation of selected culinary oils, International Journal of Food Science Nutrition, 60(S9), 289–296. Kockmann, V., Spielmann, D., Traitler, H. and Lagrade, M. (1989) Inhibitory effect of stearidonic acid (18:n-3) on platelet aggregation and arachidonate oxygenation, Lipids, 24, 1004–1007. Kodali, D.R. (2009) The utilization of rice bran wax to stabilise long chain ω-3 polyunsaturated fatty acid esters, Lipid Technology, 21, 254–256. Koh, H.H., Murray, I.J., Nolan, D. et al. (2004) Plasma and macular response to luetin supplement in subjects with and without age-related maculopathy: A pilot study, Exploratory Eye Research, 79, 21–27. Krawczyk, T.L. (1999) Flaxseed’s new faces target new users, INFORM, 10, 1029–1035. Kris-Etherton, P.M., Zhao, G., Binkoski, A.E., Covali, S.M. and Etherton T.D. (2001) The effects of nuts on coronary heart disease risk, Nutrition Reviews, 59, 103–111. Krist, S., Stuebiger, G., Bail, S. and Unterweger, H. (2006) Analysis of volatile compounds and triacylglycerol composition of fatty seed oil gained from flax and false flax, European Journal of Lipid Science Technology, 108, 48–60. Lee, J.I. and Kang, C.W. (1980) Breeding of sesame (Sesamum indicum, L.) for oil quality improvement.1. Study of the evaluation of oil quality and differences in fatty acid composition between cultivars in sesame, Journal of the Korean Society of Crop Scientists, 25, 54–65. Lee, Y.-C., Oh, S.-W., Chang, J. and Kim, I.-H. (2004) Chemical composition and oxidative stability of safflower oil prepared from safflower seed roasted with different temperatures, Food Chemistry, 84, 1–6. Leitzmann, M.F., Stampfer, M.J. and Michaud, D.S. (2004) Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer, American Journal of Clinical Nutrition, 80, 204–216. Lemcke-Norojarvi, M., Kamal-Eldin, A., Appleqvist, L.A. et al. (2001) Corn and sesame oils increase serum concentrations in healthy Swedish women, Journal of Nutrition, 131 1195–1201. Lidefelt, J.-O. (ed.) (2007) Handbook of Vegetable Oils and Fats, 2nd edn, AarhusKarlshamn, Karlshamn. Lu, Q.Y., Arteaga, J.R., Zhang, Q.F. et al. (2005) Inhibition of prostate cancer cell growth by an avocado extract: Role of lipid soluble substances, Journal of Nutritional Biochemistry, 16, 23–30. Madawala, S., Kochhar, S.P. and Dutta, P.C. (2010) Lipid profile and oxidative stability of selected specialty oils and differently processed rapeseed oils, Journal of Food Composition and Analysis, 23, in press. Maguire, L.S., O’Sullivan, S.M., Galvin, K., O’Connor, T.P. and O’Brien, N.M. (2004) Fatty acid profile, tocopherol, squalene and phytosterol content of walnuts, almonds, peanuts, hazelnuts and macadamia nut, International Journal of Food Science and Nutrition, 55, 171–178. Maheshwari, B. and Reddy, S.Y. (2005) Application of kokum (Garcinia indica) fat as cocoa butter improver on chocolate, Journal of the Science of Food Agriculture, 85, 13–140. Mandl, A., Reich, G. and Lindner, W. (1999a) Detection of adulteration of pumpkin of kokum (Garcinia indica) fat as cocoa butter improver on chocolate, Journal of the Science of Food Agriculture, 85, 13–140. Mandl, A., Reich, G. and Lindner, W. (1999b) Detection of adulteration of pumpkin seed oil by analysis of content and composition of specific Δ7-phytosterols, European Food Research and Technology, 209, 400–406. Maranz, S. and Wiseman, Z. 2004 Influence of climate on the tocopherol content of shea butter, Journal of Agricultural Food Chemistry, 52, 2934–2937.

Gunstone_c11.indd 336

1/21/2011 7:16:28 PM

Minor and Speciality Oils

337

Martinello, M., Hecker, G. and de Carmen Pramparo, M. (2007) Grape seed oil deacidification by molecular distillation: Analysis of operative variables influence using the response methodology, Journal of Food Engineering, 81, 60–64. Martinez, M.L., Mattea, M.A. and Maestri, D.M. (2008) Pressing and supercritical carbon extraction of walnut oil, Journal of Food Engineering, 88, 399–404. Maurin, R. (1992) L’huile d’argan Argania spinsoa (L.) Skeels sapotaceae, Revue Française des Corps Gras, 39, 139–146. McCaskill, D.R. and Zhang, F. (1999) Use of rice bran oil in foods, Food Technology, 53(2), 50–53. Mendes, M.F., Pessoa, F.L.P., Coelho, G.V. and Uller, A.M.C. (2005) Recovery of the high aggregated compounds present in the deodoriser distillate of the vegetable oils using supercritical fluids, Journal of Supercritical Fluids, 34, 157–162. Miraliakbari, H. and Shahidi, F. (2008) Lipid class compositions, tocopherols, and sterols of tree nut oils extracted with different solvents, Journal of Food Lipids, 15, 81–96. Mistry, D.E. (2009) An Indian perspective on vegetable oil supply and demand, INFORM, 20, 132–135. Mizukuchi, A., Umeda-Sawada, R. and Igrashi, O. (2003) Effect of dietary fat level and sesamin on the polyunsaturated fatty acid metabolism in rats, Journal of Nutrition Science and Vitaminology, 49, 320–324. Moret, S., Dudine, A. and Conte, L.S. (2000) Processing effect on the polyaromatic hydrocarbon content of grapeseed oil, Journal of the American Oil Chemists’ Society, 77, 1289–1292. Morgan, J.M., Horton, K., Reese, D. et al. (2002) Effects of walnut consumption as part of a low-fat, lowcholesterol diet on serum cardiovascular risk factor, International Journal for Vitamin and Nutrition Research, 72, 341–347. Most, M.M., Tully, R., Morales, S. and Lefrvre, M. (2005) Rice bran oil, not fibre, lowers cholesterol in humans, American Journal of Clinical Nutrition, 81, 64–68. Murkovic, M., Hillebrand, A., Winkler, J. and Pfannhauser, W. (1996) Variability of vitamin E content in pumpkin seed (Cucurbita pepo L.), European Food Research and Technology, 202, 275–278. Murkovic, M., Mullender, U. and Neunteufl, H. (2004) Carotenoid content in different varieties of pumpkins, Journal of Food Composition and Analysis, 15, 633–638. Nag, A. (2000) Stabilisation of flaxseed oil with capsicum antioxidant, Journal of the American Oil Chemists’ Society, 77, 799–800. Nagasaka, R., Chotimarkorn, C., Shafiqul, I.M. et al. (2007) Anti-inflammatory effects of hydroxycinnamic acid derivatives, Biochemical and Biophysical Research Communications, 358, 615–619. Nakamura, H. (1966) Effect of γ-oryzanol on hepatic cholesterol biosynthesis and fecal excretion of cholesterol metabolites, Radioisotopes, 25, 371–374. Namiki, M. (1995) The chemistry and physiological functions of sesame, Food Review International, 11, 281–329. Namiki, M. and Kobayashi, T. (eds) (1989) Science of Sesame, Asakura Shoten, Tokyo. Namiki, M., Hino, T., Fukuda, Y., Koizumi, Y. and Yanagida, F. (1993) AOCS-JOCS Joint Meeting, Abstract PP6. Narasinga Rao, M.S. (1985) Nutritional aspects of oilseeds, in Oilseeds Production: Constraints and Opportunities (eds H.V. Srivastava, S. Bhaskarna, B. Vasya, and K.K.G. Menon), Oxford and IBH Publishing Co., New Delhi, pp. 625–634. Narayana, T., Kaimal, B., Vali, S.R. et al. (2002) Origin of problems encountered in rice bran oil processing, European Journal of Lipid Science and Technology, 104, 203–211. Nash, D.T. (2004) Cardiovascular risk beyond LDL-C levels: Other lipids are performers in cholesterol story, Postgraduate Medicine, 116, 11–15. Nasirullah (2005) Physical refining: Electrolyte degumming of nonhydratable gums from selected vegetable oils, Journal of Food Lipids, 12, 103–111. Nesaretnam, K., Stephen, R., Dils, R. and Darbre, P. (1998) Tocotrienols inhibit the growth of human breast cancer cells irrespective of estrogen receptor status, Lipids, 33, 461–469. Ngah, W.Z.W., Jarien, Z., San, M.M. et al. (1991) Effect of tocotrienols on hepatocarcinogenesis induced by 2-acetylaminofluorene in rats, American Journal of Clinical Nutrition, 53, 1076s–1081s. Ni, R., Ausman, L.M. and Nicolosi, R.J. (1997) Oryzanol decreases cholesterol absorption and aortic fatty streaks in hamsters, Lipids, 32, 303–310. Nicolosi, R.J., Ausman, L.M. and Hegsted, D.M. (1991) Rice bran oil lowers serum total and low-density lipoprotein cholesterol and apo B levels in non-human primates, Atherosclerosis, 88, 133–142. Noboru, K. and Yusho, T. (1970) Oryzanol containing cosmetics, Japanese Patent 70:32078, October 16. O’Brien, R.D. (ed). (2009) Fats and Oils: Formulating and Processing for Applications, 3rd edn, CRC Press/Taylor & Francis, Boca Raton, FL, pp. 33–37.

Gunstone_c11.indd 337

1/21/2011 7:16:28 PM

338

Vegetable Oils in Food Technology

Oomah, B.D., Ladet, S., Godfrey, D.V., Liang, J. and Girard, B. (2000) Characteristics of raspberry (Rubus idaeus I.) seed oil, Food Chemistry, 68, 187–193. Oomah, B.D., Liang, J. Godfrey, D. and Mazza, G. (1998) Microwave heating of grape seed: Effect on oil quality, Journal of Agricultural Food Chemistry, 46, 4017–4021. Ortega-Garcia, J., Gamez-Meza, N., Noriega-Rodriguez, J.A. et al. (2006) Refining of high oleic safflower oil: Effect on the sterols and tocopherols content, European Food Research and Technology, 223, 775– 779. Orthoefer, F.T. (1996) Rice bran oil: Healthy lipid source, Food Technology, 50, 62–64. Orthoefer, F.T. (2005) Rice bran oil, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (ed. F. Shahidi), 6th edn., John Wiley & Sons, Inc., New York, pp. 465–489. Orthoefer, F.T. and Eastman, J. (2004) Rice bran oil, in Rice, Chemistry and Technology (ed. E.T. Champagne), 3rd edn, AACC, St. Paul, MN, pp. 569–593. Osawa, T., Kang, M.-H. and Naito, M. (1999) Protective role of sesame lignans in atherosclerosis, Abstract LOQ 3 pp S45, 90th AOCS Annual Meeting, 9–12 May, Florida. Osawa, T., Nagata, M., Namiki, M. and Fukuda, Y. (1985) Sesamolinol: A novel antioxidant isolated from sesame seeds, Agricultural and Biological Chemistry, 49, 3351–3352. Paschos, G.K., Magkos, F., Panagiotakos, D.B., Votteas, V. and Zampelas, A. (2007) Dietary supplementation with flaxseed oil lowers blood pressure in dyslipidaemic patients, European Journal of Clinical Nutrition, 31, 1–6. Paschos, G.K., Yiannakouris, N., Rallidis, L.S. et al. (2005) Apo-lipoprotein E genotype in dyslipidemic patients and response of blood lipids and inflammatory markers to alpha-linolenic acid, Angiology, 56, 56–59. Qureshi, A.A., Qureshi, N., Wright, J.J.K. et al. (1991) Lowering of serum cholesterol in hypercholesterolemic humans by tocotrienols (palmvitee), American Journal of Clinical Nutrition, 53, 1021s– 1026s. Rafiquzzaman, M., Hossain, M.A. and Moynul Hasan, A.J.M. (2006) Studies on the characterization and glyceride composition of safflower (Carthamus tinctorius) seed oil, Bangladesh Journal of Scientific and Industrial Research, 41, 235–238. Rahmani, R. (2005) Composition chimique de l’huile d’argane ‘vierge’, Cahiers Agricultures, 14, 461–465. Rajvanshi, A.K. (2005) Safflower petal collector, in Vth International Safflower Conference (ed. E. Esendal), Istanbul, Turkey, 6–10 June, pp. 80–85. Ramsay, M.E., Hsu, J.T., Novak, R.A. and Reightler, W.J. (1991) Processing rice bran by super critical fluid extraction, Food Technology, 45, 98–104. Rogers, E.J., Rice, S.M., Nicolosi, R.J. et al. (1993) Identification and quantification of γ-oryzanol components and simultaneous assessment of tocols in rice bran oil, Journal of the American Oil Chemists’ Society, 70, 301–307. Rong, N., Ausman, L.M. and Nicolosi, R.J. (1997) Oryzanol decreases cholesterol absorption and aortic fatty streaks in hamsters, Lipids, 32, 303–309. Rukmini, C. and Raghuram, T.C. (1991) Nutritional and biochemical aspects of the hypolipidemic action of rice bran oil: A review, Journal of the American College of Nutritionists, 10, 593–601. Ryan, E., Galvin, K., O’Connor, T.P., Maguire, A.R. and O’Brien, N.M. (2006) Fatty acid profile, tocopherol, squalene and phytosterols content of brazil, pecan, pistachio and cashew nuts, International Journal of Food Science and Nutrition, 57, 219–228. Salgin, S. and Salgin, U. (2006) Supercritical fluid extraction of walnut kernel oil, European Journal of Lipid Science and Technology, 108, 577–582. Salunkhe, D.K., Chavan, J.K., Adsule, R.N. and Kadam, S.S. (1991) Sesame, in World Oilseeds, History, Technology and Utilisation, Van Nostrand Reinhold, New York, pp. 371–402. Saska, M. and Rossiter, G.J. (1998) Recovery of γ-oryzanol from rice bran oil with silica-based continuous chromatography, Journal of the American Oil Chemists’ Society, 75, 1421–1427. Saunders, R.M. (1986) Rice bran: Composition and potential food uses, Food Review International, 3, 415–495. Sayre, R.N. and Saunders, R.M. (1990) Rice bran and rice bran oil, Lipid Technology, 2, 72–76. Sayre, R.N., Nayyar, D.K. and Saunders, R.M. (1985) Extraction and refining of edible oil from extrusionstabilised rice bran, Journal of the American Oil Chemists’ Society, 62, 1040–1043. Sayre, R.N., Saunders, R.M., Enochian, R.V., Schultz, W.G. and Beagle, E.C. (1982) Review of rice bran stabilisation systems with emphasis on extrusion cooking, Cereal Foods World, 27, 317–322. Schirmer, M.A. and Phinney, S.D. (2007) δ-Linolenic reduces weight gain in formerly obese humans, Journal of Nutrition, 137, 1430–1435.

Gunstone_c11.indd 338

1/21/2011 7:16:28 PM

Minor and Speciality Oils

339

Schwartz, H., Ollilainen, V., Piironen, V. and Lampi, A.-M. (2008) Tocopherol tocotrienol, and plant sterol contents of vegetable oils and industrial fats, Journal of Food Composition and Analysis, 21, 152–161. Sekhon, K.S. and Bhatia, L.S. (1972) Fatty acid changes during ripening of sesame (Sesamum indicum, L), Oleagineux, 27, 371–373. Seetharamaiah, G.S. and Prabhakar, J.V. (1986) γ-Oryzanol content of Indian rice bran oil and its extraction from soap stock, Journal of Food Science and Technology, 23, 270–273. Seetharamaiah, G.S., Krishnakantha, T.P. and Chandrasekhara, N. (1990) Influence of oryzanol on platelet aggregation in rats, Journal of Nutrition Science and Vitaminology, 36, 291–297. Sharma, R. and Rukmini, C. (1987) Hypocholesterolemic activity of unsaponifiable matter of rice bran oil, Indian Journal of Medical Research, 85, 278–281. Shahidi, F. (2000) Antioxidant factors in plant foods and selected oilseeds, Biofactors, 13, 179–185. Sheridan, M.J., Cooper, J.N., Erario, M. and Cheiferz, C.E. (2007) Pistachio nut consumption and serum lipid levels, Journal of the American College of Nutritionists, 26, 141–148. Shugo, M. (1979) Anti-dandruff and anti-itching shampoo. Japanese Patent 79:36306, March 17. Shukla, V.K.S., Dutta, P.C. and Artz, W. (2002) Camelina oil and its unusual cholesterol content, Journal of the American Oil Chemists’ Society, 79, 965–969. Silkeberg, A. and Kochhar, S.P. (2000) Refining of edible oil retaining maximum antioxidative potency. US Patent number 6,033,706 and EPA no. 98102528.1-2109,13.02.98 and other worldwide patent applications pending. Silva, C.F., Mendes, M.F., Pessoa, F.L.P. and Queiroz, E.M. (2008) Supercritical carbon dioxide extraction of Macadamia (Macadamia intergrifolia) nut oil: Experiments and modelling, Brazilian Journal of Chemical Engineering, 25, 175–181. Sirato-Yasumoto, S., Katsuta, M., Okuyama, Y., Takahashi, Y. and Ide, T. (2001) Effect of sesame seed rich in sesamin and sesamolin on fatty acid oxidation in rat liver, Journal of Agricultural Food Chemistry, 49, 2647–2651. Smith, J.R. (ed.) (1996) Safflower, AOCS Press, Urbana, IL. Sparks, D., Hernandez, R., Zappi, M., Blackwell, D. and Fleming, T. (2006) Extraction of rice bran oil using supercritical carbon dioxide and propane, Journal of the American Oil Chemists’ Society, 83, 885–891. Spielmann, D., Traitler, H., Crozier, G. et al. (1989) Biochemical and bioclinical aspects of black current seeds oil ω3-ω6 balanced oil, NATO ASI Series A, 171, 309–321. Spurvey, S.A. and Shahidi, F. (2007) Concentration of gamma linolenic acid (GLA) from borage oil by urea complexation: Optimisation of reaction conditions, Journal of Food Lipids, 7, 163–174. Starling, S. (2009) Omega-3, 6 and 9 form win EU novel foods approval, www.nutraingredients.com, 18 December. Stenberg, C., Svensson, M. and Johansson, M. (2005) A study of the drying of linseed oils with different fatty acids patterns using RTIR-spectroscopy and chemiluminescence (CL), Industrial Crops and Products, 21, 263–272. Stevenson, D.G., Eller, F.J. Wang, L. et al. (2007) Oil and tocopherol content and composition of pumpkin seed oil in 12 cultivars, Journal of Agricultural Food Chemistry, 55, 4005–4013. Stewart, I.M. and Timms, R.E. (2002) Fats for chocolate and sugar confectionery, in Fats in Food Technology (ed. K.K. Rajah), Sheffield Academic Press, Sheffield, pp. 159–191. Stroh, S., Gronau, J., Paetzold, R., Kraemer, K. and Neuhaeuser-Berthold, M. (1997) Effect of laying hens’ diet on the fatty acid composition of the eggs, Zeitschrift-fuer-Ernaehrungswissenschaft, 36(1), p. 76. Suzuki, K., Ohmori, T., Okada, T., Oguri, K. and Kawamura, E. (1994) Effect of an increase of dietary linseed oil on fatty acid composition and alpha-tocopherol in hen’s egg yolk, Journal of the Japanese Society of Nutrition and Food Science, 47, 23–27. Tashiro, T., Fukuda, Y., Osawa, T. and Namiki, M. (1990) Oil and minor components of sesame (Sesamum indicum, L.) strains, Journal of the American Oil Chemists’ Society, 67(8), 508–511. Teppner, H. (2004) Notes on Langenaria and Cucurbita (Cucurbitaceae) – review and new contributions, Phyton, 44, 245–308. Thompson, L.U. and Cunnane, S.C. (eds) (2003) Flaxseed in Human Nutrition, 2nd edn, AOCS Press, Champaign, IL. Thomson, C.D., Chisholm, A., Mclachlan, S.K. and Campbell, J.M. (2008) Brazil nuts: An effective way to improve selenium status, American Journal of Clinical Nutrition, 87, 379–384. Timms, R.E. (2003) Confectionery Fats Handbook – Properties, Production and Applications, Oily Press, Bridgewater.

Gunstone_c11.indd 339

1/21/2011 7:16:28 PM

340

Vegetable Oils in Food Technology

Tsevegsüren, N. and Aitzetmüller K. (1996) γ-Linolenic and stearidonic acids in Mongolian Boraginaceae, Journal of the American Oil Chemists’ Society, 73, 1681–1684. Turner, J. (1987) Linseed Law, BASF (UK), Hadleigh. Vaisey-Genser, M. (1994) Flaxseed: Health, Nutrition and Functionality, Flax Council of Canada, Winnipeg. Vali, S.R., Ju, Y., Kaimal, T.N.B. and Chern, Y. (2005) A process for the preparation of food-grade rice bran wax and the determination of its composition, Journal of the American Oil Chemists’ Society, 82, 57–64. Van Hoed, V., Depaemelaere, G., Ayala, J.V. et al. (2006) Influence of chemical refining on the major and minor component of rice bran oil, Journal of the American Oil Chemists’ Society, 83, 315–321. Velasco, L. and Fernandez-Martinez, J.M. (2004) Registration of CR-34 and CR-81 Safflower germplasms with increased tocopherol, Crop Science, 44, 2278–2279. Velasco, L. and Goffman, F.D. (2000) Tocopherol, plastochromanol and fatty acid patterns in the genus Linum, Plant Systematics Evolution, 221, 77–88. Wadsworth, J.I. (1992) Rice, in Encyclopaedia of Food Science and Technology, Vol. IV (ed. Y.H. Hui), John Wiley & Sons, Inc., New York, pp. 264–279. Wakjira, A., Labuschagne, M.T. and Hugo, A. (2004) Variability in oil content and fatty acid composition of Ethiopian and introduced cultivars of linseed, Journal of the Science of Food and Agriculture, 84, 601– 607. Watkins, C. (2009) Oilseeds of the future: Part 3, INFORM, 20, 408–410. Weiss, E.A. (1993) Linola – a new edible oil, Oils & Fats International, 9(3), 23–24. Wettasinghe, M., Shahidi, F. and Amarowicz, R. (2002) Identification and quantification of low molecular weight phenolic antioxidants in the seeds of evening primrose (Oeneothera biennis L.), Journal of Agricultural Food Chemistry, 50, 1267–1271. Whelan, A.M., Jurgens, T.M. and Bowles, S.K. (2006) Natural health products in the prevention and treatment of osteoporosis: Systemic review of randomised controlled trials, Annals of Pharmacotherapy, 40, 836–849. Wiesenborn, D., Kangas, N., Tostenson, K., Hall III, C. and Chang, K. (2005) Sensory and oxidative quality of screw-pressed flaxseed oil, Journal of the American Oil Chemists’ Society, 82, 887–892. Wong, M., Ashton, O.B.O., Requejo-Jackman, C. et al. (2008) Avocado oil – the colour of quality, in Colour Quality of Fresh and Processed Foods (eds C.A. Culver and R.E. Wrolstad), ACS Symposium Series 983, American Chemical Society, Washington DC, pp. 328–349. Woolf, A.B., Wong, M., Eyres, L. et al. (2009) Avocado oil, in Gourmet and Health-Promoting Specialty Oils (eds R.A. Moreau and A. Kamal-Eldin), AOCS Press, Urbana, IL, pp. 73–125. Wu, W., Kang, Y., Wang, N., Jou, H. and Wang, T. (2006) Sesame ingestion affects sex hormones, antioxidant status and postmenopausal women, Journal of Nutrition, 136, 1270–1275. Yang, B. (2001) Lipophillic components of sea buckthorn (Hippophae rhamnoides) seeds and berries and physiological effects of sea buckthorn oils. PhD thesis, University of Turku, Turku, Finland (ISBN 95129-2221-5). Yang, B. and Kallio, H. (2001) Fatty acid composition of lipids in sea buckthorn (Hippophae rhamnoides L.) berries of different origins, Journal of Agricultural Food Chemistry, 49, 1939–1947. Yang, B., Gunstone, F.D. and Kallio, H. (2003) Oils containing oleic, palmitoleic, α-linolenic and stearidonic acids, in Lipids for Functional Foods and Nutraceuticals (ed. F.D. Gunstone), Oily Press, Bridgewater, pp. 271, 276. Yang, B., Karlsson, R., Oksman, P. and Kallio, H. (2001) Phytosterols in sea buckthorn (Hippophae rhamnoides L.) berries: Identification and effects of different origins and harvesting times, Journal of Agricultural Food Chemistry, 49, 5620–5629. Yen, G.C. (1990) Influence of seed roasting process on changes in composition and quality of sesame (Sesamum indicum) oil, Journal of the Science of Food Agriculture, 50, 563–570. Yen, G.C. and Lai, S.H. (1989) Oxidative stability of instant noodles fried with sesame oil – vegetable oil blends, Journal of the Chinese Agricultural Chemists’ Society, 27, 196–201. Yen, G.C. and Shyu, S.L. (1988) Effects of various parameters of sesame seed on oil yield and quality of sesame oil, Journal of the Chinese Agricultural Chemists’ Society, 26, 50–62. Yen, G.C. and Shyu, S.L. (1989) Oxidative stability of sesame oil prepared from sesame seed with different roasting temperatures, Food Chemistry, 31, 215–224. Yilmaz, Y. and Toledo, R.T. (2006) Oxygen radical absorbance capacities of grape/wine industry by products and effect of solvent type on extraction of grape seed polyphenols, Journal of Food Composition and Analysis, 19, 41–48.

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Minor and Speciality Oils

341

Yokoyama, W. (2004) Nutritional properties of rice and rice bran oil, in Rice, Chemistry and Technology (ed. E.T. Champagne), 3rd edn, AACC, St. Paul, MN, pp. 505–609. Yoshida, H. (1994) Composition and quality characteristics of sesame seed (Sesamum indicum) oil roasted at different temperatures in an electric oven, Journal of the Science of Food Agriculture, 65, 331–336. Yoshida, H. and Kajimoto, G. (1994) Microwave heating affects composition and oxidative stability of sesame (Sesamum indicum) oil, Journal of Food Science, 59, 613–616. Yoshida, H., Shougaki, Y., Hirakawa, Y., Tomiyama, Y. and Mizushina, Y. (2004) Lipid classes, fatty acid composition and triacylglycerol molecular species in the kernels of pumpkin (Cucubita spp) seed, Journal of Agricultural Food Chemistry, 84, 158–163. Yoshino, G., Kazumi, T., Amano, M. et al. (1989) Effects of γ-oryzanol on hyperlipidemic subjects, Current Therapeutic Research, 45, 543–552. Zadernowski, R., Naczk, M. and Amarowicz, R. (2003) Tocopherols in sea buckthorn (Hippophae rhamnoides L.) berry oil, Journal of the American Oil Chemists’ Society, 80, 55–58. Zheng, Y., Wiesenborn, D., Tostenson, K. and Kangas, N. (2003) Screw-pressing of whole and dehulled flaxseed for organic oil, Journal of the American Oil Chemists’ Society, 80, 1039–1045. Zubr, J. and Matthaus, B. (2002) Effects of growth conditions on fatty acids and tocopherols in Camelina sativa oil, Industrial Crops Production, 15, 155–162. Zurier, R.B., Rossetti, R.G., Jacobsem, E.W. et al. (1996) Gamma-linolenic acid treatment of rheumatoid arthritis. A randomised placebo-controlled study, Arthritis and Rheumatism, 39, 1808–1817.

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Useful Websites

GENERAL FAO/WHO Food Standards: www.codexalimentarius.net Federation of Oils, Seeds and Fats Associations: www.fosfa.org Grain and Feed Trade Association: www.gafta.com Malaysian Palm Oil Association: www.mpoa.org.my Malaysian Palm Oil Board: www.mpob.gov.my Malaysian Palm Oil Council: www.mpoc.org.my Ministry of Plantation Industries and Commodities: www.kppk.gov.my National Association of Margarine Manufacturers: www.margarine.org Oil World: www.oilworld.de USDA Agricultural Research Service: www.ncaur.usda.gov

PALM AND PALMKERNEL American Palm Oil Council: www.americanpalmoil.com Department of Standards Malaysia: www.standardsmalaysia.gov.my Federation of Malaysian Manufacturers: www.fmm.org.my International Palm Society: www.palms.org Malaysian Oil Scientists’ and Technologists’ Association: www.mosta.org.my Palm Oil HQ: www.palmoilhq.com Palm Oil World: www.palmoilworld.org Palmoil.com: www.palmoil.com Roundtable on Sustainable Palm Oil: www.rspo.org Tocotrienol Resource Website: www.tocotrienol.org

SOYBEAN American Oil Chemists’ Society: www.aocs.org Bluebook Directory: www.soyatech.com/bluebook_directory.htm National Oilseed Processors Association: www.nopa.org Soyatech: www.soyatech.com Soystats 2010: www.soystats.com Statistics of Oilseeds, Fats, and Oils: www.nass.usda.gov/Publications/Ag_Statistics/2008/Chap03.pdf

Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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Useful Websites

RAPESEED Canola Council of Canada: www.canolacouncil.org/default.aspx Canola Facts: www.soyatech.com/canola_facts.htm CanolaInfo: www.canolainfo.org/index.php Rapeseed Oil: www.sud-chemie.com/scmcms/web/page_en_7056.htm What Is Canola Oil?: www.canolainfo.org/canola/index.php?page=5

SUNFLOWER Asociacion Argentina de Girasol: www.asagir.org.ar/asagir2008 Australian Oilseeds Federation: www.australianoilseeds.com/commodity_groups/australian_sunflower_ association International Sunflower Association: www.isa.cetiom.fr National Sunflower Association of Canada: www.canadasunflower.com National Sunflower Association: www.sunflowernsa.com

COCONUT (SEE ALSO PALM/PALMKERNEL) American Palm Oil Council: www.americanpalmoil.com Coconut Development Board: http://coconutboard.nic.in Malaysian Palm Oil Board: www.mpob.gov.my Malaysian Palm Oil Council: www.mpoc.org.my United Coconut Association of the Philippines: www.ucap.org.ph

COTTONSEED American Oil Chemists’ Society: www.aocs.org National Cottonseed Products Association: www.cottonseed.com www.cottonseed.com/tradingrules www.cottonseed.com/publications Official Standards List: www.codexalimentarius.net/web/standard_list.do?lang=en

GROUNDNUT American Peanut Council: www.peanutsusa.com/USA Peanut Institute: www.peanut-institute.org

OLIVE International Olive Council: www.internationaloliveoil.org Quality Control of Olive Oil: pubs.acs.org/doi/abs/10.1021/bk-2007-0952.ch007 The Big Olive – Health: www.bigolive.com.au/about-our-olive-oil/health/http://www.globalhealingcenter. com/natural-health/benefits-of-olive-oil/

CORN Contributions from Corn RefiningL www.corn.org/CRAR2009.pdf Corn Oil: www.corn.org/CornOil.pdf

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Useful Websites

345

History of Margarine: www.margarine.org/historyofmargarine.html USDA National Nutrient Database for Standard Reference: www.ars.usda.gov/Services/docs.htm? docid=8964

MINOR OILS NUTRAingredients.com: www.nutraingredients.com USA Rice Federation: www.usarice.com/processing

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Index

allergens, 75 animal fats, 3 antioxidants, 96 AOM stability, see under selected individual oils argan kernel oil, 313 argan physico-chemical properties, 14 avocado oil, 315 biodiesel, 21 blackcurrant seed oil, 326 bleaching, see under selected individual oils borage oil, 325 borneo tallow, 322 brazil nut oil, 328–30 camelina seed oil, 315 cancer, 94 canola oil, 107, 108; see also rapeseed oil capric acid, 169 caprylic acid, 169 carotenes, 118; see also under individual oils cashew nut oil, 327 CBE, see cocoa butter equivalents chestnut oil, 327 China, 14, 118; see also selected individual oils cloud point, see under selected individual oils coconut oil, 7, 12, 169; see also lauric oils carbon numbers, 173 colour, 175 density, 175 fatty acid composition, 171, 172 hydrocarbons, 174 iodine value, 171, 172, 175 lactones, 175 melting point, 172, 176 metals, 171, 175

oxidative stability, 172 physical properties, 173 physical refining, 170 Polenske value, 172, 175 refractive index, 175 regiospecific analysis, 173 Reichert–Meissel value, 172, 175 saponification value, 175 solid fat content, 176 specific gravity, 176 squalene, 174 sterols, 174 tocols, 173 trade specification, 177 triacylglycerols, 172 unsaponifiable matter, 175 virgin oil specification, 170 viscosity, 177 cocoa butter, 321 cocoa butter equivalents, 51, 321 colour, see under selected individual oils consumption of vegetable oils, 4, 6, 7 copper, see under selected individual oils copra, 170 copra pressing, 170 corn germ oil, 275, 277 corn kernel oil, 275, 277 corn oil, 14, 127, 273 carotenes, 280 cloud point, 284 cooking oil, 285 deodorisation, 275 dielectric properties, 284 extraction, 273 fatty acid composition, 275, 276 fibre oil, 275, 277

Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

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348

Index

corn oil (cont’d ) fire point, 284 flash point, 284 food uses, 285 free fatty acid, 284 iodine value, 284 margarine, 283, 285 melting point, 284 nutritional properties, 284 oxidative stability, 282 physical properties, 282 refining, 174 refractive index, 284 salad oil, 285 saponification value, 284 soapstock, 274 specific gravity, 284 spread, 283, 285 sterols, 275, 278, 280 surface tension, 284 tocols, 280 trans acids, 282, 283 triacylglycerols, 275, 277–9 unsaponifiable matter, 275, 278, 284 viscosity, 284 winterisation, 275 corn oil industry, 273 coronary heart disease (CHD), 94 cottonseed composition, 200, 204 cottonseed history, 200 cottonseed oil, 7, 12, 199 fatty acid composition, 204 AOM stability, 214, 216 carbohydrates, 209, 210 carotenoids, 210 cloud point, 214 cold point, 214 cold test, 214 colour, 215 fire point, 214, 215 flame point, 214 flavour, 215 free fatty acid, 204, 208, 215 gossypol, 211 hydrogenation, 214 iodine value, 214, 216 linters, 207 melting behaviour, 213, 214 minor fatty acids 205 modified fatty acid profile, 206 neutralisation oxidative stability, 216

Gunstone_bindex.indd 348

phospholipids, 209 polymorphism, 215 polyols, 210 pour point, 214 processing, 216 refining, 200, 201, 215, 218 refractive index, 214, 215 smoke point, 214, 215 solid fat content, 213 specific gravity, 214–16 squalene, 210 sterculic acid, 206 sterols, 209 titre, 214 tocols, 208, 210 triacylglycerols, 205, 207 unsaponifiable matter, 213, 216 viscosity, 215 winterisation, 214 cottonseed picture, 203 Crismer value (CV), 122 crush, 6, 15 density; see also specific gravity and under selected individual oils deodorisation, see under selected individual oils DHA, 87 distillation, 2 EPA, 87 epoxypropanol, see glycidol erucic acid, 107 evening primrose oil, 324 exports, 15 extraction rates, 1 Fatty acid composition, see under individual oils flaxseed, 306 flaxseed oil, 306 fatty acid composition, 307 food use, 308 physico-chemical properties, 307 sterols, 307 triacylglycerols, 307 food use of vegetable oils, 15 food-fuel debate, 19 fractionation, 2 free fatty acid (FFA), see under selected individual oils genetically modified crops, 10; see also modification of seed oils

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Index

GLA, 87, 131, 132 GLA oils, 324, 327 glycidol, 77 grape seed oil, 317 groundnut composition, 227 groundnut oil, 7, 12, 225 acetyl value, 234, 236 afflatoxin, 225 allergens, 238 animal feed, 227 antioxidant, 232 colour, 234 copper, 233 crystallisation, 235 CVD, 237 density, 234 diabetis, 237 diacylglycerol, 227 extraction, 225 fatty acid composition, 228, 229 flavour, 234 food use, 226 free fatty acid, 227, 236 frying, 226 health issues, 237 heat of fusion, 234, 236 high-oleic oil, 229 history, 225 iodine value, 234, 236 iron, 233 lipid classes, 227 melting point, 234, 235 monoacylglycerols, 227 odour, 234 peroxide value, 236 phospholipids, 227 physical properties, 234 polar lipids, 237 refractive index, 234 smoke point, 234 specific gravity, 234 stereospecific analysis, 229–31 sterols, 232 tocols, 232 triacylglycerols, 227, 229 unsaponifiable matter, 234, 236 viscosity, 234 weight control, 237 hazel nut oil, 328–30 high-erucic acid rapeseed (HEAR), 107, 132 hydrogenation, 2

Gunstone_bindex.indd 349

349

illipe butter, 51, 322 imports, 14, 15 India, 14 industrial use of vegetable oils, 6 interesterification, 2 iodine value, see under selected individual oils iron, see under selected individual oils kokum butter, 322 lauric oils, 169; see also coconut and palmkernel oils caramels, 194 chocolate and confectionery, 192 filled milk, 193 filling creams, 192 food uses, 190 frying oil, 190 ice cream, 193 margarine, 190 MCT, 191 non-dairy cheese, 193 non-dairy cream, 192 nutrition, 194 toffees, 194 lecithin, 72–4; see also phospholipids linseed, 306; see also flaxseed linseed oil, 14 low-erucic acid rapeseed (LEAR), 107 macadamia nut oil, 329–30 maize oil, see corn oil mango kernel fat, 324 margarine, 43; see also under individual oils MCPD, see monochloro propanediol melting point, see under selected individual oils modification of seed oils, 23; see also under selected individual oils monochloro propanediol, 77, 78 mustard oil, 130 non-food use of vegetable oils, 6 oilseeds, 4; see also under individual oils olive oil, 7, 13, 146, 243 analysis, 264 aroma compounds, 256, 258 authentication, 264 carotenes, 248

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350

Index

olive oil (cont’d ) centrifugation, 244 chlorophyll, 248 cloudy olive oil, 262 consumption, 3, 266 culinary applications, 266 decanters, 244 diacylglycerols, 347 diterpenes, 255 extraction, 243 fatty acid composition, 245, 260 fatty alcohols, 254 frying, 267 genuineness, 261, 265 geographical source, 265 grades of olive oil, 261 hardening, 261 hydrocarbons, 247 interesterification, 261 lampante, 261 metals, 258 monoacylglycerols, 247 percolation, 245 phenolic compounds, 255, 258, 261 phospholipids, 257 pigments, 248 pomace oil, 245, 259 pressing, 244 processing, 258 processing aids, 245 quality parameters, 261, 265 refining, 259 regulations, 261 squalene, 248, 261 sterols, 253, 260, 265 terpenic acids, 254 tocols, 247, 260 triacylglycerols, 246, 260 triterpene alcohols, 254 unrefined oil, 262 volatiles, 256 waxes, 254 OSI, 93 Oxidative stability, 120; see also individual oils Palm fruit, 178 Palm oil, 5–8, 25, 128, 155 bleaching, 40 carotenes, 35, 36, 39 cholesterol, 52 cold stability, 34 cooking oils, 42

Gunstone_bindex.indd 350

density, 32 diacylglycerols, 30 DOBI, 40 fatty acid composition, 26, 30 food applications, 42 fractionated oils, 29 frying oils, 42 hydrocarbons, 41 iodine value, 26, 30 mayonnaise, 52 melting behaviour, 33 minor components, 35 nucleation, 31 nutrition, 52 palm oil mill effluent (POME), 53 palm olein, 29, 43, 126 palm olein blends, 43, 47 palm mid-fraction, 31 palm stearin, 31, 46, 51 PFAD, 41 phospholipids, 39 physical properties, 33 polymerisation in palm oil, 27, 46, 48, 49 polymorphic behaviour, 27 red palm oil, 52 refractive index, 32 salad dressing, 52 salad oils, 52 slip melting point, 26, 30 solid fat content, 33 squalene, 39, 41 sterols, 39–42 sustainable palm oil, 53 thermograms, 36, 37 tocols, 39–41 tocotrienols, 40 trans-free margarine, 46 triacylglycerols, 26, 30 ubiquinone, 39 palmkernel oil, 7, 13, 178; see also lauric oils carbon number, 182, 186 carotenes, 185 colour, 185 density, 183 extraction, 179 fatty acid composition, 180, 186 fractionation, 185 hydrocarbons, 182 hydrogenation, 187, 189 interesterification, 188 iodine value, 180, 184, 186 kernel composition, 179

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Index

kernels, 178 melting point, 184, 186 oil palm, 178 olein, 185 palm fruit, 178 Polenske value, 183 refining, 179 refractive index, 183 Reichert–Meissel value, 183 saponification value, 183 solid fat content, 184, 187 stearin, 185 sterols, 183 tocols, 183 trade specification, 185 triacylglycerols, 180, 186 peanut oil, see groundnut oil pecan nut oil, 327 phospholipids, see under selected individual oils physical properties, see under selected individual oils pine nut oil, 327 pistachio nut oil, 327 population, 4, 7, 20 prices, 16 production by commodity, 5, 7 production by country, 4 production levels, 3, 5–7, 19, 20, 22 pumpkin seed oil, 319 Rancimat, 93 rapeseed oil, 5–7, 10 antioxidant usage, 129 China, 130 chlorophyll, 109 cold pressed oil, 124 cold test, 122 cooking oil, 124 crude oil, 120 DAG oil, 130 density, 121 deodorised oil, 120 fatty acid composition, 109, 110 flash point, 122 food uses, 123 frying oil, 125, 129, 131 glucosinolate, 107 India, 130 interesterification, 127 iodine value, 123 margarine, 127 mayonnaise, 124

Gunstone_bindex.indd 351

351

melting behaviour, 123 minor fatty acids, 110 modified oils, 109–11, 131, 144 oxidative stability, 120 phospholipids, 109, 114 physical properties, 121 pigments, 118 polar compounds, 113, 115 polymorphism, 122 refined oil, 120 refining, 110 regiospecific distribution, 111, 113 salad dressing, 124 salad oil, 124, 129 saponification number, 122 shortening, 128 smoke point, 122 sterols, 116 sulfur compounds, 111 tocopherols, 109, 115, 116, 129 trace elements, 119, 120 trans fatty acids, 110 trans-free blends, 127 triacylglycerols, 111, 115 use by country, 120 virgin oil, 124 viscosity, 122 refining, 1 refractive index, see under selected individual oils rice bran oil, 299 extraction, 299 ferulic acid, 304 food uses, 303 health issues, 305 oryzanol, 299, 304 physico-chemical properties, 303 refining, 300 sterols, 304 tocols, 300, 304 tocotrienol, 305 wax, 300, 301 safflower oil, 309 physico-chemical properties, 311 sal fat, 322 sal stearin, 51 saponification value, see under selected individual oils sea buckthorn oil, 320 seed meals, 6

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352

Index

sesame oil, 14, 291 antioxidants, 295, 297 extraction, 296 fatty acid content, 293 health issues, 298 oxidative stability, 297 production, 291 refining, 296 sesamolin, 295, 297 sterols, 294 tocols, 294 triacylglycerols, 293 unsaponifiable matter, 294 Shea butter 51, 323 shortening, 47 solid fat content (SFC), see under selected individual oils soybean oil, 5–9, 59, 159 AOM stability, 66 aqueous processing, 66, 68 bleaching, 70 cerebrosides, 63 cholesterol, 94 composition, 59, 66 cooking oil, 95 copper content, 60 crystallisation, 83 DAG oil, 96 degumming, 67 density, 88, 91 deodorisation, 70 deodoriser distillate, 75 extraction, 65 fatty acid composition, 61 fire point, 90, 91 flash point, 90, 91 food uses, 95 fractionation, 83 free fatty acid, 60 frying oil, 85 genetic modification, 83 heat of combustion, 90, 91 hydrocarbons, 60 hydrogenation, 79–81 interesterification, 80 iron content, 60 lecithin, 72–4 low-linolenic oil, 84 low-trans fats, 79–82, 85 margarine, 96 mayonnaise, 97 meal, 66

Gunstone_bindex.indd 352

melting point, 90 minor components, 63 modified oils, 79, 84, 86, 87 neutralisation, 70 non-alkaline refining, 71 nutritional properties, 93 oxidative stability, 62, 83, 85, 92 phospholipids, 60, 62, 63, 67, 85 physical properties, 87, 91 plant breeding, 83 plasticity, 91 polymorphism, 87 production, 59 refining, 67 refractive index, 89, 91 regiospecific distribution, 61 resistivity, 91 salad dressing, 97 salad oil, 95 seed composition, 59 shortening, 96 smoke point, 90, 91 soapstock, 77 solubility, 91 specific heat, 89 sphingolipids, 63 spreadability, 91 stereospecific distribution, 61 sterols, 60, 64, 71, 76, 85 tocopherols, 60, 64, 71, 76, 83 trans acids, 94 triacylglycerols, 60 unsaponifiable matter, 60, 64 viscosity, 88, 91 specific gravity, see density and under selected individual oils spreads, 43 squalene, see under selected individual oils stearidonic acid oils, 324, 326, 327 sterols, see under selected individual oils sunflower seed oil, 5–7, 11, 126, 137 added antioxidants, 158 AOM, 158 carotenes, 157 chemical modification, 153 cooking oil, 160 degumming, 152 density, 148, 154 deodoriser distillate, 153, 155 extraction, 150 fatty acid composition, 139, 141, 156 flash point, 149

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Index

food uses, 160 frying, 161 high-oleic oil, 140, 141 hydrogenation, 154 interesterification, 154 margarine, 160 melting properties, 149, 150 mid-oleic oil, 140, 141 new sun oils, 147 oxidation, 154 oxidative stability, 155, 157 peroxide value, 157, 158 phenolic compounds, 145, 160 phospholipids, 142, 152 physical refining, 153 pigments, 146 processing, 150 refractive index, 149 regular oil, 140 salad oil, 160 saponification number, 149 seeds, 138 shelf life, 156 shortening, 160 smoke point, 149, 153 solid fat content, 151 squalene, 146 stereospecific analysis, 140, 142

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353

sterols, 145 thermal properties, 150 tocopherol and other oils, 144–5 triacylglycerols, 140, 147, 148 unsaponifiable matter, 146, 149, 153 viscosity, 149, 154 wax, 153 sustainability, 22 tocols, (tocopherols and tocotrienols), see under selected individual oils trade, see imports and exports trans acids, see under selected individual oils tree crops, 3 tree nut oils, 327, 331 triacylglycerols, see under selected individual oils unsaponifiable matter, see under selected individual oils use per person, 7 vanaspati, 49, 51, 130 viscosity, see under selected individual oils walnut oil, 329–31 winterisation, see fractionation

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For further details and ordering information, please visit www.wiley.com/go/food Vegetable Oils in Food Technology: Composition, Properties and Uses, Second Edition. Edited by Frank D. Gunstone. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd. Gunstone_both02.indd 355

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Food Science and Technology from Wiley-Blackwell F O O D S A F E T Y, Q UA L I T Y A N D M I C R O B I O LO G Y The Microbiology of Safe Food 2nd Edition Food Safety for the 21st Century Microbial Safety of Fresh Produce Biotechnology of Lactic Acid Bacteria: Novel Applications HACCP and ISO 22000 - Application to Foods of Animal Origin Food Microbiology: An Introduction 2nd Edition Management of Food Allergens Campylobacter Bioactive Compounds in Foods Color Atlas of Postharvest Quality of Fruits and Vegetables Microbiological Safety of Food in Health Care Settings Control of Food Biodeterioration Advances in Thermal and Nonthermal Food Preservation Food Irradiation Research and Technology Preventing Foreign Material Contamination of Foods Aviation Food Safety Food Microbiology and Laboratory Practice Listeria 2nd Edition Preharvest and Postharvest Food Safety Shelf Life HACCP Salmonella

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PAC K A G I N G Packaging Research in Food Product Design and Development Packaging for Nonthermal Processing of Food Packaging Closures and Sealing Systems Paper and Paperboard Packaging Technology Food Packaging Technology Canmaking for Can Fillers

DA I RY F O O D S Technology of Cheesemaking 2nd Edition Dairy Fats Bioactive Components in Milk and Dairy Products Milk Processing and Quality Management Dairy Powders and Concentrated Products Cleaning in Place Advanced Dairy Technology Dairy Processing and Quality Assurance Structure of Dairy Products Brined Cheeses Fermented Milks Manufacturing Yogurt and Fermented Milks Handbook of Milk of Non-Bovine Mammals Probiotic Dairy Products

INGREDIENTS Enzymes in Food Technology 2nd Edition Food Stabilisers, Thickeners and Gelling Agents Glucose Syrups - Technology and Applications Handbook of Vanilla Science and Technology Fish Oils Weight Control and Slimming Ingredients in Food Technology Prebiotics and Probiotics Handbook Food Colours Sweeteners Sweeteners and Sugar Alternatives in Food Technology Food Additives Data Book

F O O D L AWS & R E G U L AT I O N S BRC Global Standard – Food Food Labeling Compliance Review 4th Edition Guide to Food Laws and Regulations Regulation of Functional Foods and Nutraceuticals

O I L S & FAT S Trans Fatty Acids Rapeseed and Canola Oil - Production, Processing, Properties and Uses Vegetable Oils in Food Technology Fats in Food Technology Edible Oil Processing

For further details and ordering information, please visit www.wiley.com/go/food

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