Prepare Fermented Soybean Yogurt By Lactic Acid Bacteria And The Starter Of Lactobacillus Acidophilus

Soybean milk as our traditional plant protein drink, has been popular. The technology of fermentation of soybean milk (soybean yogurt) by mixed lactic acid bacteria strains was researched. This new nutritional health of plant protein drink meets the needs of the people on the low-fat, high-protein food. And Lactobacillus acidophilus which was one of fermentative stains, as a direct vat starter (DVS) with the technology of spray-drying was studied.The optimum processing technology was determined by single factor experiment and orthogonal experiment, which were as follows:ratio of Streptococcus thermophilus, Lactobacillus delbrueckii and Lactobacillus acidophilus 1:1:2, inoculum of mixed strain 4%, fermentation temperature 43℃, sucrose addition 6%, and fermentation time 4 hours. Under these conditions, the number of live bacteria of the soybean yogurt processed under the above condition was 5.7×108cfu/mL. This soybean yogurt has good quality, delicate tissue, uniform texture, fragrance of lactic acid flavor, sweet and sour taste.The best medium and culture conditions of Lactobacillus acidophilus are:3%glucose, 3.5% yeast extract,0.2% K2HPO4,0.2% ammonium citrate,0.5% sodium acetate,0.1% twain 80,0.02% MgSO4,0.005% MnSO4 and 10% meal carrot juice. Regulate of medium pH to cultivate 6.2～6.4,37℃ aerobic culture 24 hours, the viable number of up to 1.58 ×108cfu/mL.The DVS of Lactobacillus acidophilus was prepared by spray-drying. The optimized protectants was determined by single factor experiment and orthogonal experiment. The optimized protectants:4% sucrose,5% dextrin and 15% skim milk. Spray-drying condition was obtained using the single factor experiment and Response Surface Methodology. The optimized condition:the inlet temperature 119℃, material flow rate 55mL/h, ratio of bacteria and protectant 1:28. The viable number of the DVS of Lactobacillus acidophilus to 1.67×109cfu/g.Soybean yogurt was fermented by direct vat starter and subculture starter. Soybean yogurt was fermented by direct vat starter, its sour taste was little insufficient, but flavor was still sufficient and sensory score was higher. Soybean yogurt was fermented by direct vat starter has the practical application of significance.