The Development and Improvement of Instructions
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FACTORS INFLUENCING ANTIOXIDANT PHYTOCHEMICAL STABILITY OF TEAS A Dissertation by YOUNGMOK KIM Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2008 Major Subject: Food Science and Technology FACTORS INFLUENCING ANTIOXIDANT PHYTOCHEMICAL STABILITY OF TEAS A Dissertation by YOUNGMOK KIM Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Stephen T. Talcott Committee Members, Rosemary L. Walzem Mian Nadeem Riaz Luis Cisneros-Zevallos Intercollegiate Faculty Chair, Jimmy T. Keeton December 2008 Major Subject: Food Science and Technology iii ABSTRACT Factors Influencing Antioxidant Phytochemical Stability of Teas. (December 2008) Youngmok Kim, B.E., Kyungwon University, South Korea; M.S., University of Florida Chair of Advisory Committee: Dr. Stephen T. Talcott Tea is second only to water as the most consumed beverage in the world due to its health-promoting benefits and characteristic flavor. Even though many botanical teas such as yaupon holly (Ilex vomitoria) and mamaki (Pipturus albidus) are currently available in the tea market, only limited information is available on their polyphenolic contents containing diverse biological activities. Identification of phenolic compounds was performed using advanced analytical technique of mass spectrometry to provide polyphenolic profile of teas. To present fundamental information of phytochemical stability during tea storage, studies to determine the impacts of tea processing, different packaging materials, and various storage conditions on the phytochemical stability were conducted. Ascorbic acid addition and lowering pH successfully decreased the reduction of phenolic compounds by reducing the rate of oxidative degradation while tea pasteurization accelerated oxidative degradation. Glass bottles were most effective to retain higher concentration of polyphenolics. Tea polyphenolics at lower temperature (3 °C) without light exposure iv were higher retained in each tea. Tea cream, the complex formed by interaction between polyphenolics, caffeine, protein, and metal ions, is highly undesirable in tea industry since it causes haziness and cloudiness in tea infusion as well as deteriorates sensorial properties. Only limited information is available on tea creaming in non-fermented type teas such as green tea, yaupon holly, and mamaki even though many tea creaming compounds are present in these teas. Therefore, studies were conducted to determine the degree of contribution of the tea creaming compounds to tea creaming and to develop novel chemical methods to minimize tea creaming without detrimental effects. Methods applied in the present study defined that hydrophobic interaction was the driving force make tea cream insoluble in the solution. Results obtained by present studies provided fundamental and practical information to the tea industry in terms of phytochemical stability and suggested storage stability of phytochemicals should be considered during processing and storage, since it could be better retained or improved by applying appropriate methods. v DEDICATION This dissertation is dedicated to tea lovers. Drink more tea! vi ACKNOWLEDGEMENTS Words cannot express my deep appreciation for my doctoral committee chair, Dr. Stephen T. Talcott who is my lifetime mentor and role model. During the last five years of study in graduate school, he has never hesitated to share his time with me and put endless efforts in helping and encouraging me to pursue my goal. He has made my time at University of Florida and Texas A&M University truly memorable with his great personality. His profound knowledge and infectious enthusiasm have been a major driving force for me to complete my work. My dissertation is a true reflection of his intellectual influence. I would like to express my deepest gratitude to him. I am also very thankful for having a great doctoral committee. I appreciate Drs. Rosemary L. Walzem, Mian Nadeem Riaz, and Luis Cisneros-Zevallos for serving as my committee members with their consideration and valuable advice. The benefits I gained from them will last throughout my life. My sincere gratitude also goes to my precious lab brothers and sister, Chris Duncan, Jorge Cardona, and Lisbeth Pacheco. They always provided me unconditional help, support, and love. I am truly blessed to have these people in my life. I also thank my little sister Kimmy Krenek who always made me smile. I will be happy to watch her growing as a great scholar. Thanks also go to my old lab mates in University of Florida: Dr. Joonhee Lee, Dr. David Del-Pozo, Flor Nunez, Lorenzo Puentes, and Lanier Fender. I am very proud of knowing such a brilliant and charming group of people. It was so enjoyable to have vii worked and shared the fun with my people. My appreciation is extended to the professors in University of Florida, Drs. Charles Sims, Bruce Welt, Don Huber, Susan Percival, Jeffrey Brecht and Murat Balaban for their endless support and trust. Many thanks to my RAs at Texas A&M University: Jennifer, Carl, Tram, and Mike. Without their effort and time, I would not have been able to finish my research. I am greatly indebted to my parents for their unconditional and endless encouragement, support, and love. I have been honored and inspired by the strength and dignity of their character. I am truly blessed to be born as their son. Finally, my greatest blessing goes to my beloved wife, Sunghee Ahn. She always trusted and encouraged me and it became a strong energy for me to cope with any kinds of obstacles during my days in graduate school. I truly believe that marrying her is one of the best choices I have ever made in my entire life. I will love her from the bottom of my heart until death do us part. viii TABLE OF CONTENTS Page ABSTRACT .............................................................................................................. iii DEDICATION .......................................................................................................... v ACKNOWLEDGEMENTS ...................................................................................... vi TABLE OF CONTENTS .......................................................................................... viii LIST OF FIGURES ................................................................................................... x LIST OF TABLES .................................................................................................... xxiv CHAPTER I INTRODUCTION ................................................................................ 1 Justification .................................................................................... 1 Objectives ....................................................................................... 2 II LITERATURE REVIEW ..................................................................... 4 Tea and Ready-to-Drink Tea Markets ............................................ 4 Health Benefits from Teas .............................................................. 5 Roles of Polyphenolics ................................................................... 7 Phytochemicals in Teas .................................................................. 10 Processing of RTD Teas ................................................................. 16 Packaging Materials for RTD Teas ................................................ 19 Conditions for RTD Tea Storage ................................................... 21 Tea Cream Formation ..................................................................... 23 III IDENTIFICATION OF ANTIOXIDANT PHENOLIC COMPOUNDS IN THREE TEA VARIETIES USING LC-ESI-MSN ANALYSIS .......................................................................................... 27 Introduction .................................................................................... 27 Materials and Methods ................................................................... 28 Results and Discussion ................................................................... 34 ix CHAPTER Page IV IMPACT OF TEA PROCESSING METHODS ON PHYTOCHEMICAL STABILITY AND QUALITY OF THREE TEA VARIETIES DURING STORAGE ............................................ 65 Introduction .................................................................................... 65 Materials and Methods ................................................................... 66 Results and Discussion ................................................................... 69 V THE IMPACT OF PACKAGING MATERIALS ON THE ANTIOXIDANT PHYTOCHEMICAL STABILITY OF THREE TEA VARIETIES ................................................................................. 121 Introduction .................................................................................... 121 Materials and Methods ................................................................... 122 Results and Discussion ................................................................... 124 VI DETERMINATION OF THE INFLUENCE OF VARIABLE STORAGE CONDITIONS ON THE QUALITY AND PHYTOCHEMICAL STABILITY OF THREE TEA VARIETIES .... 149 Introduction .................................................................................... 149 Materials and Methods ................................................................... 150 Results and Discussion ..................................................................