Storage Stability And Intestinal Tolerability Of Yogurt Soymilk Fermented By Lactobacillus Rhamnosus As Well As Yogurt Soymilk Fermented By Lactobacillus Casei

With the study and development on functional soybean products as well as the improvement of people’s health consciousness, soybean products will become heat competition issues and consume fashion in soybean products domain. Soybean yogurt is a nutrient-rich new product with unique flavor, which was made from fresh soymilk by fermentation of Lactobacillus. When separation and lack of fine texture are the mean defects of sogure. It does not only improve the flavor of soymilk, but also enhance the nutritional value of soymilk and it has health effects of soy and probiotics. Lactobacillus rhamnosus and Lactobacillus casei as typical probiotics, their function of increasing the health have been admitted, soybean products with probiotics had been a bioengineering products of 21 century. This paper studied on changes in the viable counts, pH, and titratable acidity values of in the soybean yogurt fermented by Lactobacillus casei as well as in the soybean yogurt fermented by Lactobacillus rhamnosus at different temperature during storage to determine the best storage period ; Also studied on bile toleranc,gastric juice tolerance and intestinal juice tolerance of probiotics in soybean yogurt fermented by Lactobacillus casei and the soybean yogurt fermented by Lactobacillus rhamnosus.Lactobacillus casei 05-20 and Lactobacillus rhamnosus 05-28 was isolated from dairy products and used for soymilk fermentation. The stability of soybean yogurt fermented by Lactobacillus casei as well as soybean yogurt fermented by Lactobacillus rhamnosus stored at refrigeration temperature (-20℃, 7℃, 4℃) and room temperature (25℃) for four week were investigated. The result indicated that the best storage time at refrigeration temperature (-20℃, 7℃, 4℃) were determined as 22d, under which the viable number of the soybean yogurt fermented by Lactobacillus casei was still more than 4.3×10~7cfu/mL and the pH value decreased to about 4.54. It had fine and smooth texture which tasted good. Under room temperature (25℃) storage, the best storage time of the soybean yogurt fermented by Lactobacillus casei was were determined as 12d, under which the viable number was 1.45×10~8cfu/mL and the pH value decreased to 4.37.Besides, the best storage time of the soybean yogurt fermented by Lactobacillus rhamnosus was were determined at refrigeration temperature (-20℃、7℃、4℃) were determined as 18d, under which the viable number of the soybean yogurt fermented by Lactobacillus rhamnosus was still 3.8×10~8cfu/mL above and the pH value decreased to about 4.64. It had fine and smooth texture which tasted good. Under room temperature (25℃) storage, the best storage time of the soybean yogurt fermented by Lactobacillus rhamnosus was were determined as 8d, under which the viable number was 9.8×108cfu/mL cfu/mL and the pH value decreased to 4.2.This paper studies on growth of probiotics in soybean yogurt fermented by Lactobacillus casei as well as the soybean yogurt fermented by Lactobacillus rhamnosus at different concentration of bile salt. The result indicated that Lactobacillus casei in the fermented soymilk showed strong tolerance, and the viable counts of Lactobacillus casei can still reach 1×10~6cfu/mL. Also the viable counts of soybean yogurt fermented by Lactobacillus rhamnosus can reach 1×10~6cfu/mL after processing 3h in different concentration of bile salt. It showed strong tolerance to bile salt in the fermented soymilk.This thesis studies on survival of probiotics in soybean yogurt fermented by Lactobacillus casei as well as the soybean yogurt fermented by Lactobacillus rhamnosus in the artificial digestive juices. The result indicated that Lactobacillus casei in the fermented soymilk showed strong tolerance to the artificial digestive juices, and the viable counts of Lactobacillus casei can still reach 1×10~6cfu/mL. Also the viable counts of soybean yogurt fermented by Lactobacillus rhamnosus can reach 1×10~6cfu/mL after processing 24h in artificial intestinal juice. It showed strong tolerance to artificial digestive juices in the fermented soymilk. This study provided a scientific basis for the quality control and the safe storage of the soybean yogurt.