Quality Factors of Fruits and Vegetables. Chemistry and Technology PDF
Preview Quality Factors of Fruits and Vegetables. Chemistry and Technology
Quality Factors of Fruits and Vegetables In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 405 ACS SYMPOSIUM SERIES Quality Factors of Fruits and Vegetables Chemistry and Technology Joseph J Jen The University of Georgia Developed from a symposium sponsored by the Division of Agricultural and Food Chemistry at the 196th National Meeting of the American Chemical Society, Los Angeles, California, September 25-30, 1988 American Chemical Society, Washington, DC 1989 In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Library of Congress Cataloging-in-Publication Data Quality factors of fruits and vegetables (ACS symposium series, ISSN 0065-6156; 405) "Developed from a symposium sponsored by the Division of Agricultural and Food Chemistry at the 196th National Meeting of the American Chemical Society, Los Angeles, California, September 25-30, 1988." Includes bibliographical references. 1. Fruit—Quality—Congresses. 2. Vegetables— Quality—Congresses. 3. Food—Analysis—Congresses. 4. Food—Sensory evaluation—Congresses. I. Jen, Joseph J., 1939- . II. American Chemical Society. Division of Agricultural and Food Chemistry. III. American Chemical Society. Meeting (196th: 1988: Los Angeles, Calif.) IV. Series. TX557.Q35 1989 664'.807 89-17684 ISBN 0-8412-1663-0 Copyright © 1989 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per-copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, MA 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, tor creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance ot any right or permission to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. ACS Symposium Series M. Joan Comstock, Series Editor 1989 ACS Books Advisory Board Paul S. Anderson Mary A. Kaiser Merck Sharp & Dohme Research Ε. I. du Pont de Nemours and Laboratories Compan Michael R. Ladisch Alexis T. Bell Purdue University University of California—Berkeley John L. Massingill Harvey W. Blanch Dow Chemical Company University of California—Berkeley Daniel M. Quinn Malcolm H. Chisholm University of Iowa Indiana University James C. Randall Alan Elzerman Exxon Chemical Company Clemson University Elsa Reichmanis John W. Finley AT&T Bell Laboratories Nabisco Brands, Inc. C. M. Roland U.S. Naval Research Laboratory Natalie Foster Lehigh University Stephen A. Szabo Conoco Inc. Marye Anne Fox The University of Texas—Austin Wendy A. Warr Imperial Chemical Industries G. Wayne Ivie U.S. Department of Agriculture, Robert A. Weiss Agricultural Research Service University of Connecticut In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Foreword The ACS SYMPOSIUM SERIES was founded in 1974 to provide a medium for publishin format of the Serie IN CHEMISTRY SERIES except that, in order to save time, the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously pub lished papers are not accepted. Both reviews and reports of research are acceptable, because symposia may embrace both types of presentation. In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Preface QUALITY OF RAW AND PROCESSED FRUIT AND VEGETABLE PRODUCTS are sometimes elusive factors and may differ from person to person based on individual tastes. However, there is no doubt that consumers want high-quality foods in our fast-moving society. Consumers want convenient, fresh, light, and nutritious products for their diets. Fruits and vegetables fit in th who work with fresh an processe vegetable high-quality products to consumers economically. It was with this thought in mind that I organized the symposium on which this book is based. I had a second motive in organizing this symposium on quality factors of fruits and vegetables. Literature and research reports on the subject appear in many different places: in journals and books that cover food science, food technology, plant physiology, plant pathology, horticulture, agricultural sciences, agricultural engineering, and packaging. One cannot gather the vast amount of information on the quality of fruits and vegetables in one volume. However, I hope this book can serve as an important starting reference for researchers working in this field. It may also serve as a textbook for students interested in fresh and processed fruits and vegetables. The book is separated into six sections and 30 chapters. An overview chapter is provided to introduce the subject. The first three sections deal with the chemical aspects of the three major quality factors of fruits and vegetables, that is, color, flavor, and texture. The next three sections deal with the technological aspects of quality factors of fresh and processed fruits and vegetables: Section four deals with storage and light processing of fresh produce; section five deals with quality improvement of further processed fruits and vegetables; and section six deals with some of the newer technology used in this field. With 30 chapters and multiple authors in this book, it is unavoidable that some minor duplication of coverage may occur. The comprehensiveness of each chapter will differ. Nevertheless, all authors are well-known researchers in their respective fields or have published extensively in the subject. I hope that cross-fertilization among the authors can help the growth of this scientific field. xi In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Acknowledgments I want to thank many people for assisting me in bringing this book to fruition. I want to thank the authors for presenting the papers and for their cooperation in completing the chapters in a timely manner. Also, more than 50 scientists served as reviewers. Their comments contributed greatly to the quality of the book. The editors of the ACS Books Department worked patiently with me. My wonderful, diligent secretary, Beth Knight, assisted in the handling of the manuscripts. Last, but not least, I appreciate the financial assistance provided by the Financial Committee of the Division of Agricultural and Food Chemistry of the American Chemical Society, the Agricultural Research Division of Campbell Soup Company, the Basic Research Division of Kraft, Inc., and the Research and Developmen Company. JOSEPH J. JEN Department of Food Science and Technology The University of Georgia Athens, GA 30602 April 25, 1989 xii In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Chapter 1 Chemical Basis of Quality Factors in Fruits and Vegetables An Overview Joseph J. Jen Department of Food Science and Technology, The University of Georgia, Athens, GA 30602 Color, flavor, texture generally recognized as the four quality factors of fruits and vegetables. The natural pigments, chlorophylls, carotenoids and anthocyanins, form the chemical basis of color. Enzymatic and non -enzymatic browning contribute to coloring of certain processed fruits and vegetables. Various volatile aroma and nonvolatile compounds give fruits and vegetables special flavors. Cell wall components and turgor pressure are the two entities that provide the texture of fruits and vegetables. Pectic substances and pectic enzymes are closely related to firmness and softening of many fruits and vegetables. Celluloses and lignins are associated with toughness and woody texture. The roles of hemicelluloses and extinsins in fruits and vegetables are not clear. Vitamin C and minerals are the major nutrients of fruits and vegetables. Processing often alters the quality of fruits and vegetables but does not change the chemical basis underlining the factors. Fruits and vegetables constitute an important part of the human diet. It is one of the four major groups of food our body needs to ingest daily. The current consumer trend is towards fresh, natural, minimally processed, and, yet, convenience foods. This situation increases the opportunities for this segment of diet to play an increased role in our health and well-being. Consumers purchase foods on the basis of quality. To improve quality of fruits and vegetables, we must understand the chemical basis of the quality factors. Many books and chapters have been written on food quality although few have been devoted solely on fruits and vegetables (1, 2). Brief summaries of the subject matter can usually be found in food chemistry books (3). The purpose of this chapter is to provide an overview of the chemical bases of quality 0097-6156/89/0405-0001$06.00/0 c 1989 American Chemical Society In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 2 QUALITY FACTORS OF FRUITS AND VEGETABLES factors in fruits and vegetables. Subsequent chapters will provide detailed information on many specific topics. The flavor and nutritive value of foods are often the subject of many symposia and books. This volume will emphasis color and texture of fruits and vegetables. Color With few exceptions, the coloring matters of fruits and vegetables belong to one of the following four categories of chemical compounds (4): 1. Tetrapyrrole derivatives: chlorophylls, pheophytins 2. Isoprenoid derivatives: carotenoids, xanthophylls 3. Benzopyran derivatives: anthocyanins, flavonoids, and related compounds 4. Certain artifacts The first three groups are natural pigments while the last group is reaction products of enzymatic and non-enzymatic browning reactions from natural physiological changes or from processing of fruits and vegetables. The chlorophylls are responsible for the green color of nearly all fruits and vegetables. The isomers, chlorophyll a. and chlorophyll b^, exist in a 3:1 ratio in higher plants. They have slightly different visible spectra and color shades. Chlorophylls are magnesium-chelated tetrapyrroles with an esterified 20 carbon alcohol, phytol. The phytol gives the pigments a unique ability to be embedded in the cell organelle chloroplasts. The naturally existing chlorophyllases can convert chlorophylls to water-soluble chlorophyllides, without the phytol, but do not significantly alter the green color. Acidic conditions can cause the replacement of hydrogen for magnesium and make the chlorophylls into pheophytins. The pheophytins are brown in color and are normally undesirable in most foods. The loss of green color in green vegetables is an important problem in certain thermal processing operations. The chlorophyll chemistry has been the subject of several investigations. The conversion of chlorophylls to pheophytins follows first-order reaction kinetics (5). The photooxidation of chlorophylls have slow reaction rates (6). Organic acids released from the destruction of intact cells can cause conversion of chlorophylls to pheophytins in processed plant foods. Acids are also formed during processing of certain green leafy vegetables (7). Various methods developed to preserve the green color of processed food have undesirable effects of one form or another. Green metallocomplexes of chlorophyll derivatives formed during thermal processing offer a possible solution to some vegetables. A chapter dealing with this subject is included in this book. The carotenoids are a group of lipid-soluble pigments responsible for the yellow, orange, and red color of many fruits and vegetables. Most plant foods contain a variety of carotenoids that differ mainly in their content of double bonds and oxygen atoms. The mevalonic acid pathway derived isoprenoids may also occur in combination with reducing sugars via glycosidic bonds. In Quality Factors of Fruits and Vegetables; Jen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
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