COMPARISON OF DAIRY YOGURT WITH IMITATION YOGURT FERMENTED BY DIFFERENT LACTIC CULTURE FROM SOYBEAN MILK by YEERU JENNIFER CHENG, B.S. A THESIS IN FOOD TECHNOLOGY Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved December, 1988 ACKNOWLEDGHENTS I would like to thank ny research advisor. Dr. Leslie D. Thonpson, for her guidance, encouragenent, and patience during ny graduate career at Texas Tech. I also would like to thank Dr. Helen Brittin for her advisenent on sensory evaluation in ny research. I an indebted to Dr. Margarette Harden for taking tine fron her busy schedules to serve on ny connittee. I an very grateful to ny sensory taste panelists, for their patience, and serious cooperation in this study. I thank ny best friends, Szu-ning Chung, Sun-yung Chen, and Eillen Chao, for their valuable helping on making the soybean nilk. Finally, and nost inportantly, 1 thank ny parents, Mr. and Mrs. An-Tsen Cheng, for their generous support for this research. 11 LIST OF CONTENTS ACKNOWLEDGMENTS ii LIST OF TABLES vi LIST OF FIGURES viii CHAPTER I. INTRODUCTION 1 II. LITERATURE REVIEW 4 Background of the Soybean Plant 4 Chenical Conposition of Soybean Seed... 6 Carbohydrates 6 Protein 7 Lipids 8 Nutritional Aspect 9 New Soybean Food Developnent 12 Fernentation 13 Hicroorganisns 14 Protein Coagulation 17 Flavor 18 111 III. COMPARISON OF SOYBASED YOGURT FERMENTED WITH DIFFERENT COMBINATIONS OF LACTIC ACID BACTERIA WITH DAIRY YOGURT AND NONFERMENTED SOYMILK 22 Sunnary 22 Materials and Methods 23 Culture Preparation 23 Soynilk Preparation 23 Soybased Yogurt Preparation 25 Proxinate Analysis 27 Sensory Evaluation 27 Objective Analysis 29 Statistical Analysis 29 Results and Discussion 30 Conclusion 51 IV. COMPARISON OF DAIRY YOGURT WITH FERMENTED SOYBEAN YOGURTS FORMULATED WITH GELATIN AND LACTOSE 52 Sunnary 52 Introduction 53 Materials and Methods 53 Culture Preparation 53 Soynilk Preparation 54 Soybased Yogurt Making 55 Sensory Evaluation 55 IV Objective Measurenents 56 Statistical Analysis 56 Results and Discussion 58 Conclusion 70 REFERENCES 71 LIST OF TABLES TABLE 1. Anino acids in the protein of soybeans and cow's nilk 10 2. Generation tines for lactic acid bacteria grown in soynilk and cow's nilk 15 3. Propagation tenperatures for lactic acid bacteria 24 4. Incubation tenperatures and tines for the fernentation of soybased yogurts 26 5. Proxinate conposition of dairy yogurt, various soybased yogurts and unfernented soynilk 31 6. Standard color by Munsell Color Systen of dairy yogurt, fernented soybased yogurts and unfernented sojmilk 49 7. Hunter L, a, b color values systen for dairy yogurt, fernented soybased yogurts, and unfernented soynilk 50 8. The standard plate counts of bacterial inoculun after propagation and after fernentation for soybean treatnents, fornulated with only gelatin and both lactose and gelatin 59 9. Objective neasurenents of acidity for dairy plain yogurt, fernented soybased yogurt addition with gelatin, and fernented soybased yogurt addition with lactose along with gelatin 64 VI 10. The hue, value and chroma of dairy, fernented soybased yogurt with gelatin, and fernented soybased yogurt with both gelatin and lactose 68 11. Hunter Lab systen L, a and b values for plain dairy yogurt, fernented soybased yogurt addition with gelatin, and fernented soybased yogurt addition with gelatin along with lactose 69 Vll LIST OF FIGURES FIGURE 1. Sensory score sheet used in the evaluation of dairy yogurt, various soybased yogurts and nonfernented soynilk 28 2. Subjective beany arena evaluation of dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all species, and unfernented soynilk 33 3. Subjective buttery arena evaluation of dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all species, and unfernented soynilk 34 4. Subjective evaluation of bitter flavor for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all species, and unfernented so3milk 35 Subjective evaluation of sour taste for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all species, and unfernented soynilk 36 Vlll 6. The pH values for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all the species, and unfernented soynilk 39 7. Percent titratible acidity (Z lactic acid) of dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mensenteroides, and by all the species, and unfernented soynilk 40 8. Subjective evaluation of over-all yogurt flavor for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mensenteroides, and by all the species, and unfernented soynilk ' 41 9. Subjective evaluation of nouth-feel for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all the species, and unfernented soynilk 42 10. Subjective evaluation of texture for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all the species, and unfernented soynilk 44 IX 11. Texture Analyzer neasurenent for dairy yogurt, soybased yogurts fernented by Streptococcus thermophilus and Lactobacillus casei, by Lactobacillus delbrueckii and Leuconostoc mesenteroides, and by all species, and unfernented soynilk 45 12. The relationship anong hue, value, and chrona in Munsell Color Systen 46 13. The relationship anong Hunter systen L, a, and b values 48 14. Sensory score sheet used to evaluate dairy and soybased yogurts fornulated with gelatin and lactose 57 15. The subjective evaluation of various arenas found in diary yogurt and soybased yogurts fornulated with gelatin and with gelatin and lactose 60 16. Subjective evaluation of flavor of dairy yogurt and soybased yogurts addition with gelatin and with gelatin and lactose 62 17. The subjective evaluation of texture of dairy plain yogurt and soybased yogurts addition with gelatin and with gelatin and lactose 65 18. The Texture Analyzer reading for dairy yogurt and soybased yogurts addition with gelatin and with gelatin and lactose 67 CHAPTER I INTRODUCTION Due to a shortage of food in developing countries and inadequate nutritional status of people in lower socio- econonic groups in the U.S., inexpensive protein and calorie sources need to be developed and utilized. Soybeans, with 42Z protein, are an ever growing inexpensive protein source for these populations. Conpared to aninal proteins, soy proteins are relatively inexpensive. For exanple, soy protein costs $ 1.11/lb ($ 212/1000 kg soybean with 42Z protein) (FAO Monthly Bulletin of Statistics, 1987) while aninal protein in the forn of nilk costs $ 12/lb ($ 0.89/guart honogenized nilk in supernarket with 28.19Z protein). Additionally, whole soybean is nearly 20Z fat naking it an excellent energy source. Fron a cardiovascular stand point, inclusion of soy lipids in the diet is desirable due to their high proportion of unsaturated fatty acids. Kinsella (1985) has deternined that there are four critical criteria deternining the acceptance of new foods or food ingredients—nutritional value, safety, acceptability, and cost. Nutritionally, the high protein 2 quantity and quality and the high proportion of unsaturated fatty acids nakes soybeans very desirable. Through proper processing techniques and handling procedures soybased products can be a safe food source. However, soy products have low consuner acceptability due to undesirable off- flavors, which have often been described as "green," "beany," "painty," "grassy," and "bitter" (Nelson et al., 1971; Wolf and Cowan, 1975; Rackis et al., 1978). One approach to elininating the beany flavor of soybean products is the use of nicrobial fernentation (Mital and Steinkraus, 1979). Since fernentation often inproves the flavor and texture of soybeans, attempts have been nade to develop fernented products fron soybean nilk by using nethods enployed by the dairy industry (Wang et al., 1974). Ariyana subjected soybean nilk to a yogurt- type fermentation resulting in a product that had higher protein and nineral contents than that of dairy yogurt (Ariyana, 1963). At the Northern Regional Research Laboratory, acidophilus-type soybean nilk was prepared using Lactobacillus acidophilus NRRL B-629. The resulting fernented soybean nilk had a desirable flavor after the addition of sugar and vanilla flavoring (Hesseltine and Wang, 1978). Therefore, 4 different species of lactic acid bacteria. Streptococcus thermophilus, Lactobacillus casei, Lactobacillus delbrueckii, and Leuconostoc mesenteroides. were selected for fernenting soynilk to nake soybased yogurts. The objectives of this experinent were: (1) to exanine the effects of various fomentations on soynilk, and (2) to investigate the differences in sensory properties anong