99D-15 |
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C.-L. WANG and A. Mustapha. Department of Food Science, University of Missouri, 256 William C. Stringer Wing, Columbia, MO 65211-5160 Probiotics are currently added as supplemental cultures into yogurts. Due to the acidity of yogurts and antagonism by traditional starter cultures, the survival of probiotics in such products is often limited. Thus, using probiotics as starters may be a more efficient way to deliver these health beneficial organisms to consumers. Our object was to determine if an acceptable soy yogurt-like product could be manufactured by using the probiotic bacterium, Lactobacillus paracasei or Lactobacillus rhamnosus GG together with Streptococcus thermophilus. The yogurt base was made using commercial soymilks mixed with sugar and nonfat dry milk for a total solid content of 15%. Cultures consisting of a S. thermophilus yogurt starter, and L. paracasei or L. rhamnosus GG at a 1:1 ratio were used to ferment the base, while a Lactobacillus bulgaricus starter together with S. thermophilus served as the control. Strawberry and vanilla flavors were added and fermentation proceeded at 37°C until the pH reached 4.5-4.6. Microbial counts, titratable acidity and pH were measured every 5 days for 30 days during refrigerated storage, while descriptive sensory analysis was performed on days 0, 7 and 14. Lactobacilli counts of 108 CFU/ml were established and maintained in vanilla and strawberry soy yogurts for 30 days of storage. The numbers of L. bulgaricus, on the other hand, significantly declined by 3-5 log CFU/ml within 10 days and to as low as 0-15 CFU/ml by the end of storage. The pH values were in the range of 4.4-4.5 and titratable acidity ranged from 0.85-1.04%. There were significant differences in fermented, beany, astringency and thickness attributes. The results suggest that an acceptable soy yogurt can be successfully manufactured by using the probiotics L. paracasei and L. rhamnosus GG. The high counts maintained in the yogurts would ensure sufficient numbers would be delivered to consumers.
Session 99D, Food Microbiology: General
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