Vitamin E Content and Stability in Peanuts and Peanut
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VITAMIN E CONTENT AND STABILITY IN PEANUTS AND PEANUT PRODUCTS DURING PROCESSING AND STORAGE by JI-YEON CHUN (Under the Direction of Ronald R Eitenmiller) ABSTRACT Vitamin E content and changes in moisture, color, microstructure and oxidative stability of raw and roasted peanuts were investigated during processing and storage. The mean α-tocopherol levels (mg/100g) were 8.2 for raw peanuts, 4.1 for roasted peanuts, 9.4 for peanut butter, 5.5 for reduced-fat peanut butter and 12.3 for peanut oils. Contribution of the oil and stabilizer added to the roasted peanuts during peanut butter processing was 4% of α-T and 5% of γ-T in peanut butter. Tocopherol loss by peanut butter manufacture was below 6%. Oven roasting at 140 to 160 ºC rapidly decreased moisture content. About 5, 12, 20, and 10% of initial levels of α-, β-, γ- and δ-T in peanuts were lost during roasting at 160 ºC, respectively. Tocopherol levels of peanuts slightly increased at 140 ºC and were remained constant at 150 ºC. Tocopherol levels of peanut oils prepared by pressing the roasted peanuts significantly decreased at all roasting temperatures (p<0.05). After roasting at 160 ºC for 20 min, a 16% loss of α-T occurred in the peanut oils. Swollen epidermal cells and rupture of parenchyma tissue of peanuts were observed in roasted peanuts by SEM. During storage at 21 ºC, lipid oxidation rapidly progressed in roasted peanuts. Under vacuum, lipid oxidation was significantly retarded for both raw and roasted peanuts (p<0.05). Tocopherol levels of raw and roasted peanuts exponentially decreased with increasing peroxide value during storage (α- T=8.8956e-0.0468PV, R2 = 0.9246). Under air, α- and γ-T of roasted peanuts dramatically decreased during the initial four weeks of storage, resulting in about 84 and 68% losses for α- and γ-T, respectively. α-T showed the least stability during storage and the most stability to roasting. After 12 weeks of storage, more than 50% of α-T remained for roasted peanuts stored under vacuum compared to about 10% stored under air. INDEX WORDS: Vitamin E, HPLC, Direct extraction, Peanuts, Peanut butter, Peanut oils, Roasting, Peanut butter manufacture, Storage, Oxidative stability, Microstructure, Color, Scanning electron microscopy VITAMIN E CONTENT AND STABILITY IN PEANUTS AND PEANUT PRODUCTS DURING PROCESSING AND STORAGE by JI-YEON CHUN B.A.G., Korea University, Korea, 1995 M.A.G., Korea University, Korea, 1997 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fullfillment of the Requirements of the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2002 2002 Ji-Yeon Chun ALL Rights Reserved VITAMIN E CONTENT AND STABILITY IN PEANUTS AND PEANUT PRODUCTS DURING PROCESSING AND STORAGE by JI-YEON CHUN Major Professor: Ronald R. Eitenmiller Committee: Philip E. Koehler Robert D. Phillips Robert L. Shewfelt William L. Kerr Electronic Version Approved: Gordhan L. Patel Dean of the Graduate School The University of Georgia December 2002 DEDICATION This dissertation is dedicated to My parents in law and My parents For constant support, encouragement, and unconditional love. To My beloved husband Sung-Gil Choi For his patience, deepest love and encouragement. AND To My beloved sons Seung-Beom Choi and Seung-Zoo Choi, who give me strength, joy, patience and love. Without all of you, nothing would be possible. I always love you. iv ACKNOWLEDGMENTS I would like to express my deepest appreciation and gratitude to my major professor, Dr. Ronald R. Eitenmmiller for his inspiration, invaluable guidance, lovely patience, constant encouragement, and financial support throughout my Ph.D. program. His belief and care of me helped me finish my research. I also would like to thank Philip E. Koehler, Dr. Robert D. Phillips, Dr. Robert L. Shewfelt, Dr. William L. Kerr for serving on my advisory committee. I am very grateful to the faculty and staff at the Food Science and Technology Department for their guidance and kind help toward completing my study. Thanks to all graduate students and postdoctoral fellows past and present with whom I have worked in the laboratory and the department: Lin Ye, Junsoo Lee, Nantipa Pansawat (Tang), Jin-Kyung Kim, Yoo-Kyung Kim, In-Sook Son, Sunisa Siripongvutikorn, Walairut Chantarapanon (Jane), Poom, Panada Banjongsinsiri, Yusof Maskat, and others for their encouragement, assistance, and friendships. Appreciation is also extended to Ms. Wonda Rogers who always listened to my voice and is a strong helper to work in the Lab. I would like to give a special thanks to Ms. Rosemarie Goodrum for encouragement and guidance for my defense seminar. Thanks are extended to Dr. Glene Ware and Jae-Choul Lee for assistance in statistics for experiments. I also like to thank to Mr. Robert Karn and TaraFoods, Albany, Georgia for providing all peanut and peanut butter samples and detail information for this research. I like to express special thanks to my wonderful friends in a church group and Alumni Family of Korea University for their love and friendships. I have no words to express my sincere gratitude and indebtedness to my beloved parents, parents in law, husband and two sons, relatives and my wonderful neighbors for their unconditional love, unwavering encouragement, and faith during my entire life span. Last, I would like to thank and worship my heavenly Father from whom all the blessing of my entire life and without whom nothing would be possible. v TABLE OF CONTENTS Page ACKNOWLEDGMENTS ...................................................................................................v CHAPTER I INTRODUCTION................................................................................................1 II LITERATURE REVIEW.....................................................................................9 III EFFECT OF PEANUT BUTTER MANUFACTURE ON VITAMIN E CONTENT OF PEANUTS AND ANALYSIS OF COMMERCIAL PEANUT PRODUCTS FOR VITAMIN E ......................................................................93 IV EFFECTS OF DRY ROASTING ON VITAMIN E CONTENT OF PEANUTS AND PEANUT OILS PREPARED FROM ROASTED PEANUTS AND MICROSTRUCTURE OF RAW AND ROASTED PEANUTS ...................112 V VITAMIN E AND OXIDATIVE STABILITY DURING STORAGE OF RAW AND DRY ROASTED PEANUTS ...............................................149 VI SUMMARY AND CONCLUSIONS..............................................................177 vi CHAPTER I INTRODUCTION 1 2 INTRODUCTION Tree nuts and peanuts are becoming established as significant dietary components contributing to lowered incidence of coronary heart disease (CHD). Five large epidemiological studies including the Adventists Health Study (Fraser et al., 1992, 1995, 1997a, 1997b), the Iowa Women’s Health Study (Prineas et al., 1993; Kushi et al., 1996), the Nurses’ Health Study (Hu et al., 1998), the Cholesterol and Recurrent Events (CARE) Study (Brown et al., 1999), and the Physicians’ Health Study (Albert and Willett, 2002) reported that overall, consuming nuts more than 5 times/week resulted in an 18-51% reduction in CHD risk. It was strongly supported by clinical findings that diets increasing the quantities of MUFA and PUFA supplied from nut slower total and LDL cholesterol levels which are risk factors for CHD (Spiller et al., 1992, 1998; Sabaté et al., 1993; Morgan and Clayshulte, 2000; Zambón et al., 2000; Curb et al., 2000; Rajaram et al., 2001; Almario et al., 2001; Hyson et al., 2002). This protective effect of nuts may be through multiple mechanisms due to the variety of nutrients and bioactive substances present in nuts. Folate, vitamin B-6, vitamin E, selenium, sterols, fiber and other phytochemicals as well as MUFA and PUFA in peanuts are considered as possible components to have protective effects on health (Sabate and Hook, 1996; Kris-Etherton et al., 1999). Peanuts contain approximately 50% oil composed of about 81% unsaturated fatty acids of which about 39% are polyunsaturated (USDA, Nutrient Data Bank, 2002). Therefore, peanut lipids meet the criteria of high MUFA content for a cholesterol- lowering diet. Conversely, it makes peanuts susceptible to oxidative rancidity during processing and storage that is the most common cause of quality loss. The quality loss of lipids due to oxidation is of economic and nutritional importance to the peanut industry because of off-flavor development and the loss of nutrients such as essential fatty acids, amino acids, and lipid-soluble vitamins such as vitamin E. Vitamin E delays the oxidation process by eliminating the free-fatty acid radicals, although it can neither completely prevent the autoxidation of lipids nor reverse the formation of peroxides. Due to its role as a scavenger of free radicals, vitamin E is also believed to protect against onset of chronic diseases, mainly cancer and cardiovascular 3 diseases (Burton an Ingold, 1989; Burton and Traber, 1990; Rader et al., 1997). Thus, it is heavily in demand as a supplementary nutrient. Natural food sources are of increasing interest to the consumer and industry. Peanuts and peanut products are good sources of Vitamin E. The levels of vitamin E in peanuts are influenced by cultivar, genotype, growing conditions, origins, year, regions, and maturity stages (Baurnfeind, 1980; Sanders et al., 1992; Hashim et al., 1993a, 1993b). After harvesting, the vitamin E level of peanuts and peanut products can be influenced by processing, storage, and marketing, primarily due to the antioxidant role of vitamin E. Peanuts are processed into peanut butter, snacks, confections and peanut