Freeze-dried And Keep-alive Lactic Acid Bacterial (LAB) Key Technology Research

With the rapidly development of fermented dairy product industry, It's significan t for promoting the industrial process of lactic acid bacteria starter culture, improvin g development of fermented dairy product. In this paper, it has introduced many func tions of lactic acid bacteria (LAB), expounded the mechanism and influence fa ctors of freeze-drying. After high density fermenting LAB, it researched the effe ct of centrifuging force and time on the loss rates of lactic acid bacteria; quested the te chniques of freeze-drying technology and good conditions for lactic acid bacteria; ana lyzed the advantaged factors during preserve and resurrection.The preparation of starter is the key technology of yoghurt production, an d the step of separating cell is the important process for LAB starter. Throug h researching the effect of centrifuging force and time, we obtained the optimum centr ifugal conditions for lactic acids bacteria: centrifugal force is 5100g, rotate speed is 6000r/min, centrifugal time is 10min.We researched technological parameters of freeze-drying technology: freeze-dryi ng thickness, drying time and so on, screened out four excellent combine protective m aterials: skim milk 15%, trehalose 4%, vitamin C 1%, MSG 1.5%. With this protectiv e materials, the survival rate of Lactobacillus acidophilus,Laacillus bulgaricus and S. thermophilus can reach 89.10%,87.96% and 88.13%. In addition, we researched th e effect under different ways of pre-freezing, got the conclusion that the pre-freezin g with liquid nitrogen is better than normal way and the smaller the surface area of ba cteria drops, the better the viable count is.Finally, compared the effect factors of preserve and resurrection after freeze-dryi ng technology, we fined the physiological saline is a good medium of rehydration, wh at's more, controlling the content of oxygen and water activity is important way to get higher lactic acid bacteria viable count.