Selective Enumeration Of Mixture And Ferment Milk Of Kinds Of Lactic Acid Bacteria

At booming development of fermented milk industry, the lactic acid bacteria which in fermentation agent and fermentation products, development from early simple Streptococcus thermophilus and Lactobacillus bulgaricus mixed cultures fermentation agent to of multi-strain mixture of direct investment and fermentation agent. However, a mixture of various lactic acid bacteria lactic acid bacterial counts of quick detection method has not been reported. Therefore, research has become one of the hot areas of research.The paper selected Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium, Lactobacillus rhamnosus as a pilot study. First, based on the original MRS culture medium was investigated adding 0.05% (m / m) of LiCl on the impact of different strains of choice count. Then, according to the fermentation of lactic acid bacteria can use different types of sugar, using mannitol, rhamnose, xylose replace glucose MRS medium to study the five kinds of lactic acid bacteria on different types of sugar mixture in the growth of different strains, then achieve an accurate count of lactic acid bacteria can be detected. And on the basis of these studies, for the culture time, temperature and inoculation method were optimized. Finally, optimization methods in the process of yogurt fermentation products, commercial yogurt mix powder and commercially available in the three systems was verified.The results show that: in the normal MRS medium containing 0.05% LiCl, only Streptococcus thermophilus and Lactobacillus rhamnosus can grow; in xylose as the sole source of sugar modified MRS medium only Bifidobacterium and Lactobacillus rhamnose could grow; in mannitol as the sole source of the MRS medium of sugar, only Lactobacillus rhamnosus and Lactobacillus acidophilus can grow; in Lactobacillus rhamnose as the sole source of the MRS medium of sugar, only Lactobacillus rhamnose could grow. After optimization of the culture temperature was 37℃, the culture time was 48h, inoculation method is pouring. Three kinds of system validation tests showed that on the five medium the appropriate concentration of bacteria were cultured, can be calculated in the mixed bacteria strain types and their respective ratio.This study offers a method that can provide a rapid detection and enumeration of mixed lactic acid bacteria. The method offers a theoretical foundation for quality of fermented dairy products and research and development of dairy.