Lipid Oxidation Pathways, Volume Two PDF
Preview Lipid Oxidation Pathways, Volume Two
Lipid Oxidation Pathways Volume 2 Lipid Oxidation Pathways Volume 2 Editors Afaf Kamal-Eldin Department of Food Science Swedish University of Agricultural Sciences David B. Min Department of Food Science and Technology Ohio State University U , I rbana llInoIs AOCS Mission Statement To be a global forum to promote the exchange of ideas, information, and experience, to enhance personal excellence, and to provide high standards of quality among those with a professional interest in the science and technology of fats, oils, surfactants, and related materials. AOCS Books and Special Publications Committee M. Mossoba, Chairperson, U.S. Food and Drug Administration, College Park, Maryland R. Adlof, USDA, ARS, NCAUR-Retired, Peoria, Illinois M.L. Besemer, Besemer Consulting, Rancho Santa, Margarita, California P. Dutta, Swedish University of Agricultural Sciences, Uppsala, Sweden T. Foglia, ARS, USDA, ERRC, Wyndmoor, Pennsylvania V. Huang, Yuanpei University of Science and Technology, Taiwan L. Johnson, Iowa State University, Ames, Iowa H. Knapp, DBC Research Center, Billings, Montana D. Kodali, Global Agritech Inc., Minneapolis, Minnesota G.R. List, USDA, NCAUR-Retired, Consulting, Peoria, Illinois J.V. Makowski, Windsor Laboratories, Mechanicsburg, Pennsylvania T. McKeon, USDA, ARS, WRRC, Albany, California R. Moreau, USDA, ARS, ERRC, Wyndoor, Pennsylvania A. Sinclair, RMIT University, Melbourne, Victoria, Australia P. White, Iowa State University, Ames, Iowa R. Wilson, USDA, REE, ARS, NPS, CPPVS-Retired, Beltsville, Maryland AOCS Press, Urbana, IL 61802 ©2008 by AOCS Press. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means without written permission of the publisher. ISBN 978-1-893997-56-1 Library of Congress Cataloging-in-Publication Data Lipid oxidation pathways / [edited by] Afaf Kamal-Eldin. p. cm Includes bibliographical references and index. ISBN 1-893997-43X (acid-free paper) 1. Lipids--Oxidation. I. Kamal-Eldin, Afaf. QP751.L5517 2003 572´.57--dc21 2003006200 CIP Printed in the United States of America. 12 11 10 09 08 5 4 3 2 1 The paper used in this book is acid-free and falls within the guidelines established to ensure permanence and durability. Contents Preface ......................................................................................................................vii 1 Chemistry and Reactions of Singlet and Triplet Oxygen in Lipid Oxidation Hyun Jung Kim and David B. Min .................................................................1 2 Chemistry and Reactions of Reactive Oxygen Species in Lipid Oxidation Eunok Choe .................................................................................................31 3 Oxidation of Long-Chain Polyunsaturated Fatty Acids Kazuo Miyashita ..........................................................................................51 4 Oxidation of Conjugated Linoleic Acid Taina I. Pajunen (née Hämäläinen) and Afaf Kamal-Eldin ...........................77 5 Oxidation of Cholesterol and Phytosterols Afaf Kamal-Eldin and Anna-Maija Lampi ...................................................111 6 Tocopherol Concentration and Antioxidant Efficacy Afaf Kamal-Eldin, Hyun Jung Kim, Levon Tavadyan, and David B. Min .......127 7 Carotenoids and Lipid Oxidation Reactions Afaf Kamal-Eldin ........................................................................................143 8 Co-Oxidation of Lipids with Proteins and Nucleic Acids Karen M. Schaich ........................................................................................181 9 Lipid Oxidation in Food Dispersions Eric A. Dekker, Wilailuk Chaiyasit, Min Hu, Habibollah Faraji, and D. Julian McClements ...........................................................................273 10 Antioxidant Evaluation Strategies Leif H. Skibsted ...........................................................................................291 Index .................................................................................................................... 307 v Preface The first volume of Lipid Oxidation Pathways, published in 2003, tried to highlight some of the anomalies and gaps in our current understanding of the lipid oxidation mechanism and kinetics. The different chapters discussed how lipid oxidation pro- ceeds in different environmental surroundings and highlighted areas where further research is needed. A number of prominent scientists in academia and industry said they appreciate the book for its particular focus on the anomalies between observed and predicted behaviour and requested a new volume of the book that focuses on the oxidation kinetics and mechanisms governing the behaviour of different molecular species involved in lipid oxidation reactions. This second volume thus aims to com- plement the first volume and extend it to more detailed reviews of the reactions of lipid molecules other than conventional polyunsaturated fatty acids. The first chapter discusses the basic chemistry of singlet oxygen and its involve- ment in lipid oxidation reactions with particular reference to reactions in foods such as reversion of flavour in soybean oil. The second chapter discusses the different reac- tive oxygen species and their particularities in lipid oxidation. Chapter 3 discusses in detail the oxidation of long chain polyunsaturated fatty acids, including eicosapentae- noic acid (EPA) and docosahexaenoic acid (DHA), and discusses the kinetic effects of different environments. Chapter 4 provides a detailed description of the oxidation of conjugated linoleic acid (CLA), particularly the fact that hydroperoxides are not the major primary oxidation products from this fatty acid and that conventional methods for estimating the degree of lipid oxidation (such as peroxide value and conjugated dienes) will lead to erroneous conclusions in this case. Chapter 5 describes the oxida- tion of sterols, which follow the same basic mechanism as for oleic acid. In chapter 6, possible reactions behind the paradoxical behaviour of tocopherols, i.e. increased rate of inhibited oxidation at high levels of these antioxidants or what has been known as tocopherol’s pro-oxidant effect, has been delineated. Chapter 7 reviews the literature pertinent to the oxidation mechanisms and oxidation products of carotenoids. Like with the case of CLA, radical addition rather than hydrogen abstraction seem to be the most plausible mechanism. The co-oxidation of lipid and proteins is discussed comprehensively in Chapter 8 with emphasis on the reactions of proteins with free radicals and lipid hydroperoxides, epoxides, and carbonyl compounds. Chapter 9 dis- vii viii A. Kamal-Eldin and D.B. Min cusses lipid oxidation in emulsions and how it is affected by interaction with proteins, type of emulsifier, antioxidants, and the structural organization of different molecular species. Chapter 10 discusses the complication in evaluating lipid antioxidants and inhibitors as it relates to the widely different modes of their action. The editors sincerely thank the authors of the different chapters for their valu- able contribution with timely literature reviews within this second volume of Lipid Oxidation Pathways. We also acknowledge, with sincere gratitude, Jodey Schonfeld, Brock Peoples, and their colleagues at the AOCS Press for their professional help in the editing and for the production of this volume. Afaf Kamal-Eldin David B. Min Uppsala, Sweden Columbus, OH 1 Chemistry and Reactions of Singlet and Triplet Oxygen in Lipid Oxidation Hyun Jung Kim and David B. Min Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Road, Columbus, OH 43210 Introduction Oxidation of food components can influence flavor quality, nutritional quality, con- sumer acceptability, and toxicity of food products (Min and Boff, 2002; Choe and Min 2006). Lipid oxidation products are especially responsible for the development of rancidity by the production of low-molecular-weight compounds that impart undesir- able flavors. Oxidation occurs by both triplet oxygen and singlet oxygen. Atmospheric triplet oxygen contains two unpaired electrons, while singlet oxygen has no unpaired electrons. The electron arrangement of triplet oxygen does not allow for a direct reac- tion with compounds, such as unsaturated fatty acids, that is nonradical and in the singlet state. Triplet oxygen oxidation of foods has been extensively studied during the last 70 years (Labuza, 1971; Min and Lee 1996). Singlet oxygen formed in the presence of triplet oxygen by excitation is thought to be responsible for initiating lipid oxidation of food compounds, due to its ability to directly react with the electron-rich compounds. Singlet oxygen rapidly increases the oxidation rate of foods even at very low temperatures (Rawls and Van Santen, 1970). Singlet oxygen oxidation can produce new compounds, which are not found in ordinary triplet oxygen oxidation in foods (Frankel et al., 1981). During the last 30 years, the attention paid to singlet oxygen oxidation of foods has increased. This chapter will discuss the basic information on the chemical properties, forma- tion, inhibition, and detection of singlet oxygen oxidation as it relates to the oxidation of lipids. Electron Configuration of Triplet and Singlet Oxygen The molecular orbital theory best describes the electron structure of molecular oxy- gen and its excited states (Korycka-Dahl and Richardson 1978). Molecular oxygen is composed of two oxygen atoms and has 10 molecular orbitals containing 12 valence electrons. Valence electrons are added sequentially to the orbitals in order of increasing energy to obtain molecular orbitals of triplet oxygen and singlet oxygen (Figures 1 and 2). According to Pauli’s exclusion principle, only two electrons can occupy each orbital. Hund’s rule states that one electron is placed into each orbital of equal energy one at a 1 2 H.J. Kim and D.B. Min Molecular σ* Atomic Atomic π* π* π π 2p 2p 2p 2p 2p 2p x y z z y x σ Energy σ* 2s 2s σ σ* 1s 1s σ Fig. 1.1. Molecular orbital of triplet oxygen. Molecular σ* Atomic Atomic π* π* π π 2p 2p 2p 2p 2p 2p x y z z y x σ Energy σ* 2s 2s σ σ* 1s 1s σ Fig. 1.2. Molecular orbital of singlet oxygen.
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