Data Analysis of the C'orkelation between Processing Variables and Concen'i'rai'ions of Isoflavones in Soymilk

Li Xiuyu (Writer) (Last Name) (First Name) (Initial) Data analysis of the correlation between processing variables and concentrations of isoflavones in soymilk (Title) Food & Nutritional Sciences Ana M.Q. VandeLinde, PhD May, 2005 5 2 (Graduate Major) (Research Advisor) (MonthIYear) (No. of Pages) American Psychological Association (APA) Publication Manual, 5th Edition (Name of Style Manual Used in This Study) Soybeans and soyfoods are rich in isoflavones. The importance of isoflavones is widely appreciated and is the subject of intense research and discussions. The most common isoflavones are genistin, genistein, daidzin, and daidzein. Genistein and daidzein are the nonglucoside forms of genistin and daidzin, respectively. The chemical structures of these nonglucoside forms are very similar to the human estrogen. In soybeans the concentrations of the glucoside forms of isoflavones are relatively higher than the corresponding non-glucoside compounds. When soyfoods are made, processing procedures can affect the concentrations of the isoflavones. The main objective of this study is to determine the effects of processing variables on concentrations of genistin, daidzin, genistein and daidzein in soymilk. The variables that were considered are type and pH of soaking solution, soaking temperature, grinding temperature, and addition of glucosidase enzyme. The three soaking solutions are water, hydrochloric acid (HCI), and acetic acid (HC2H302) solutions. The three soaking temperatures used are 5 "C, 21 "C, and 55 "C. The pH of HC1 and HC2H302 solutions are 2,4, and 6. The two grinding temperatures used are 21 "C and 80 "C. High-Performance-Liquid-Chromatography (HPLC) was used to determine isoflavone contents of soymilk samples. The data were analyzed using a statistical package called Statistical Product and Service Solutions (SPSS). Statistical analysis was conducted to evaluate correlations between processing variables and the concentrations of isoflavones in soymilk. In addition, pair-sample t-test was conducted to evaluate whether or not there are differences in the means of isoflavone concentrations in soymilk treated with and without glucosidase enzyme. The major findings of this study are: the pH of HC2H302 solution significantly affected the yield of genistein (p < 0.05). A negative correlation was found between soaking temperature and the concentrations of genistin and daidzein in soymilk made from beans that were soaked in water (p < 0.05). There were strong correlations between grinding temperature and the concentrations of genistein, daidzin, daidzein (p < 0.01), and genistin (p < 0.05) in soymilk made from beans that were soaked in HC1 solution. The results of pair-sample t-test showed that the addition of glucosidase enzyme significantly increased the yield of the four isoflavones in soymilk.