The Study On Stability And Application Of Lb. Casei Direct Vat Set

The aim of this research is to produce Lb. casei Direct Vat Set (DVS), which is used in the actual applications fermentation. We started to research the stability of Lb. casei DVS in storage and the application in milk and soy. We can make conclusions as following.The powder had higher moisture content which had greater decline in the same storage. Storage temperature had great influence on the number of viable cells to the powder. At room temperature storage condition, the moisture content with 3.76% which the survival rate was 26.6% in the two-month testing process, while the moisture content with 6.47% which the survival rate was 2.33%. Storage temperature also affected the stability of the powder. To the moisture content with 5.39% of the powder which the number of viable cells decreased rapidly at room temperature storage condition with a period of 6 months testing, the survival rate was 3.86%.The best storage temperature was frozen, the survival rate could reach 45.7%, the better condition was cold storage, the survival rate reached 24.6%. In short, self-made powder had higher stability. The number of viable cells can be maintained at more than 10 orders of magnitude which stored at room temperature for 6 months , cold storage and frozen still had 11 orders of magnitude.Lb. casei was used to replace the part of Lb. bulgaricus on the application in fermented yogurt. Studies had shown that Lb. casei: Lb. bulgaricus: St. thermophilus=2:3:5, the inoculation volume was 5×106cfu/mL, the fermentation temperature was 42℃, the pH of fermented yogurt could reach 4.50 at 6 hours after inoculation, and the flavor was different from the traditional fermented yogurt after storage which had slower post-acidification, the pH decreased from 4.50 to 4.20 with cold storage 7 days, fermented yogurt was maintaining good taste, and the number of viable cells were kept 109cfu/mL above during the storage.Lb. casei DVS fermented soy milk. To compare the single strain with Lb. casei and composite bacteria which prepared fermented soybean milk and fermented milk drink, the results showed that Lb. casei and Lb. bulgaricus complexed acided fast to the fermented milk-based and had high nitrogen content amino acid peptide with same fermentation time. The last fermentation time shortened 10h compared with a single bacterium Lb. casei. Fermented soybean milk drink had better taste, but had more serious acidification after long-term storage; a single bacterium Lb. casei and composite Lb. paracasei had longer fermentation time, but could maintained long-term stability during storage to the product line.In addition, we researched Lb. casei to the long-term fermentation process in the physical and chemical changes. Different temperatures impacted the fermentation flavor. The results showed that Lb. casei could produce fermented milk with cheese flavor which without rennet whey and non-exclusive circumstances, which with 37℃long period of fermentation. At last fermented milk with 37℃long-term storage had better cheese flavor after-ripening process, which followed by room temperature storage, the flavor was less to the 10℃low-temperature storage.