The Influence of Formulation and Processing on the Retention of B Vitamins in Asian Noodles
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The influence of formulation and processing on the retention of B vitamins in Asian noodles A thesis submitted for the degree of Doctor of Philosophy by Lan Bui BSc Food Sci (Hons) Victoria University Victoria University Australia July 2003 WER THESIS 664.755 BUI 30001007974027 Bui, Lan The influence of formulation and processing on the retention of B vitamins in Declaration I hereby declare that all work carried out in this project was performed while I was enrolled as a Ph.D. student in the School of Life Sciences and Technology, Victoria University of Technology, Werribee Campus. To the best of my knowledge, this work has not been submitted in whole or part for any other degree or diploma in any University and no material contained in this thesis has been previously written or published by another person, except where due reference is made in the text. Lan To Thi Bui June 2003 Acknowledgements Acknowledgments I would like to firstly express my special appreciation to my supervisor, Dr Darryl Small. He kindly provided invaluable advice, support and encouragement throughout my research and during preparation of this thesis. I am especially grateful for his patience, thoughtfulness and practical approach as well as his guidance to overcome all the difficulties during the whole project. This project was carried out at the Werribee Campus of Victoria University and many people there provided help. I am grateful to the laboratory staff including Stacey Lloyd, Dale Tomlinson, Michael Rogerson, Joseph Pelle and especially Vilnis Ezernieks, for their friendship as well as enthusiastic assistance and support in using the various items of laboratory equipment. Vilnis contributed greatly by showing me how to set up and use the chromatography instruments. His skill in troubleshooting and repairing were invaluable. I also thank my best friends, Irawati Prasatya, Mai Giang and Panuwat Suppakul for their warm friendship, help and consideration. I express gratitude to the security staff on campus - they were always friendly and watched over me when no-one else was around. I also thank all the library staff at Werribee for their resource assistance, wonderful service and smiling all the time. Many people made valuable time available and provided suggestions and I thank: Dr Alison Duncan (Victoria University) who helped with the microbiological aspects of folate analysis; the staff of Agrifood Technolgy, Werribee, who supplied samples and allowed me to use plate reading equipment; the staff of Food Science Australia, Werribee for helpful discussions and use of facilities; Lata Masih (University of Melbourne, Werribee), Dean Clarke (Australian Government Analytical Laboratory, South Melbourne) and Assoc Prof WUliam Thiel (School of Pharmacy, Monash University) for helpful discussions; Assoc Prof Mary Millikan (Victoria University) who provided encouragement; Darren Jones (Waters-Millipore) for suggestions on HPLC analyses; and Michael Teller (Bronson and Jacobs, Melbourne) who supplied commercial vitamin samples. I am particularly grateful to Dr Jeanne Rader (United States Food and Drug Administration, Maryland) who always answered my emails ill Acknowledgements promptly with wise advice and kind encouragement during the critical stage of validating the folate determination. 1 am thankful to Professors Mike Adams and Andrew Halmos of the Departments of Applied Chemistry and Food Science, respectively, at RMIT University, Melbourne. They kindly provided me with access to their facilities during the later stages of this work. I gratefully acknowledge the financial support provided by an Australian Postgraduate Award throughout the course of the study. I also received assistance to attend the Australian Cereal Chemistry Conference in Sydney during September 2001 through the award of a scholarship by the Royal Australian Chemical Institute, Cereal Chemistry Division. I would like to express my special thanks to my husband, Ba Nguyen, for his moral support, help and patience which encouraged me to complete this study. I am also grateful to my mother and all the family members in Australia as well as in Vietnam for their love, encouragement and support. IV Publications Publications and presentations Parts of the research reported in this thesis have been published and the details are as follows: Journal article Lan T. T. Bui and Darryl M. Small. 2003. The influence of formulation and processing on stability of thiamin in three styles of Asian noodles. Food Chemistry - accepted for publication. Conference presentations Four papers were presented at the 51^' Australian Cereal Chemistry Conference held in Sydney in September 2001. The tides of the presentations are listed below. In addition, the page numbers for each correspond to the proceedings of the conference, edited by M Wootton, IL Batey and CW Wrigley, and published in 2002 by the Cereal Chemistry Division of the Royal Australian Chemical Institute, Melbourne, ISBN 1 876892 03 2. The stability of B group vitamins during storage of Asian noodles, pages 228-231. The influence of formulation and processing on stability of B group vitamins in Asian noodles, pages 232-236. B group vitamins in Asian noodles - a study of commercial products, pages 217-220. Methods for extraction and analysis of B group vitamins from flour and cereal based foods, pages 237-240. Abstract Abstract Foods prepared from wheat flour represent a potential source of B group vitamins in the diet. Although Asian noodles account for the end-use of at least twelve percent of all wheats produced globally, the contribution of these foods to dietary intakes of B vitamins is unknown. Other issues are the instability of vitamins and the analytical challenges of vitamin analysis resulting from the presence of vitamers in many foods. Accordingly the aims of this investigation were firstly to re-evaluate and validate procedures for extraction and measurement of B group vitamins in wheat flour and the three major styles of Asian noodles. Secondly, the stability of thiamin, riboflavin, folate and vitamin B-6 during processing of noodles has been investigated. Initial studies of HPLC procedures which might allow simultaneous determination of all the B vitamins of interest indicated that no one approach to extraction and analysis provided reliable results. Accordingly the vitamins were investigated separately. In each case various alternative procedures were compared and these included a number of heating and enzymatic treatments for extraction as well as analysis methods based on microbiological growth, fluorhnetry and HPLC. The procedures found to be most suitable were validated in terms of analyses of a reference sample, along with repeatability and recovery studies. The three common vitamer forms of vitamin B-6 were found in flour although levels were relatively low. Fortification of flour resulted in Asian noodles with enhanced levels of the vitamin. In all three styles of noodle, losses occurred during dough mixing and also during cooking. The overall losses were in the range 57-65 percent of initial levels. The varying formulations and processes for each style had little impact on stabiUty of added pyridoxine used for fortification. Various published methods for extraction and analysis for riboflavin have been evaluated. Enzymatic digestion gave higher results for riboflavin than methods using acids and reverse phase chromatography was found to be effective with a solvent system including methanol and hexanesulphonic acid. When this was applied to white salted and yellow alkaline styles of Asian noodles stored under various conditions it was Vll Abstract observed that losses occurred particularly in fresh noodles. Moisture content, product pH and temperature appear to be the primary determinants of riboflavin retention. The stability of riboflavin varied markedly between the different styles with losses typically occurring at each step. Prior to cooking, losses of between 27 and 38 percent of the riboflavin were found in fortified noodles. During boiling to the optimum point, a further decline occurred resulting in overall losses of 52-71 percent. The incorporation of alkaline salts in the formulation appeared to be the primary factor influencing the extent of losses in the three styles of Asian noodles. Folate was analysed by a microbiological method employing Lactobacillus casei in combination with enzymatic extraction procedures. The application of conjugase, a- amylase and protease was found to give the highest results for total folate contents of flour and noodle samples. Noodles were fortified with folic acid and up to forty percent of the added vitamin was lost for all three styles of noodle. The losses were greater during boiling in comparison with other steps in manufacture. Overall losses for each style were similar. The proportion of original folate levels present in the formulation which was lost during processing was the same for unfortified noodles and for varying levels of fortification up to amounts of half RDI per serving. It is concluded that all three styles of Asian noodles can provide effective vehicles for folate fortification. A standard fluorometric procedure was selected and validated for the determination of thiamin in flours and noodle samples. A range of dried commercial Asian noodles was chosen to include white salted, yellow alkaline and instant styles of noodles and the thiamin contents measured before and after cooking. For most samples, the thiamin levels were relatively low and considerable losses