| Summary: | 碩士 === 國立臺灣大學 === 畜產學研究所 === 89 === Samples were prepared using skim milk inoculated with 1% of Lactobacillus acidophilus and 2% of Bifidobacterium longum. After fermentation for 10 hr at 37℃, the samples were then mixed with vegetable juice in the ratio 1：1 to produce the vegetable drinking yogurt. This study investigated the effects of sugars and prebiotics on the activity of L. acidophilus and B. logum, and established the optimum model to manufacture the new dairy product with stable quality and high nutrition.
Chicory inulin, isomalto-oligosaccharides and sucrose were selected to investigate the effects of sugars on the activity of L. acidophilus and B. logum. Results indicated that adding isomalto-oligosaccharides not only could stimulate growth of L. acidophilus and B. logum and yielded better β-galactosidase activity during fermentation, but also kept higher level of L. acidophilus and B. logum during one month storage. Therefore, isomalto-oligosaccharides was chosen as an additive to vegetable drinking yogurt.
For the prebiotics of the vegetable drinking yogurt, a three-variable and three-level design method, which was analyzed by response surface methodology (RSM), was used to determine optimum addition of calcium gluconate, sodium gluconate and N-acetylglucosamine. Results indicated that these three prebiotics affected responses significantly (p<0.05). RSM suggested five optimum models in which the percentage of calcium gluconate, sodium gluconate and N-acetylglucosamine were 0.46, 0.05, 0.01%; 0.45, 0.06, 0.02% ; 0.43, 0.01, 0.02% ; 0.49, 0.12, 0.00% and 0.47, 0.12, 0.00%. Through the validation process, no difference in the counts of L. acidophilus and B. logum (p>0.05) was observed, however, the counts of B. logum andβ-galactosidase activity of the first group were superior to the other groups (p<0.05). Therefore, the optimum added percentage of calcium gluconate, sodium gluconate and N-acetylglucosamine were 0.46, 0.05, 0.01%.
Concluded from the comprehensive study from the experiments, the ideal process of manufacturing vegetable drinking yogurt was that skim milk was blended with 4% of isomalto-oligosaccharides and then pasteurized at 85℃ for 30 min. After cooling (42℃), calcium gluconate, sodium gluconate and N-acetylglucosamine were added 0.46, 0.05, 0.01% ,then inoculated with 1% of L. acidophilus and 2% of B. longum. After 37℃ fermentation for 10 hr, then mixed with vegetable juice in the ratio 1：1 and stored at 4℃.
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