| With the rapidly development of fermented dairy product industry, It's of significant for promoting the industrial process of Lacfic acid bacteria starter, improving development of fermented dairy product;. In this paper, it has isolated strains and optimizalion collocation for fine Lactic acid bacteria. The cheap enrichment medium suited for industrial processing and freeze-drying protectant were screened. The technology of enrichment culture for Lacfic acid bacteria , cell concentration % lyophilization were studied. The suitable survival condition for lactic acid bacteria in the process of freeze-drying were explored initially. High efficiency concentrated Lactic acid mixed freeze-drying culture were prepared. And the fermentation activity of freeze-drying starter hi milk were examined.Hundreds of Lactic acid bacteria strains isolated from fine yogurt product or commercial starter in our country or abroad. Lactobacillus bulgaricus four isolates and Strerptococcus thermophilus four isolates were initially screened. By studying on fermentation nature and mixed proportion in milk. Lactobacillus bulgaricus L.b-DR and Strerptococcus thermophilus S.t-3 with good fermentation nature were screened. The optimum proportion of two strain for mixed fermented in milk is determined at the rate of 1:1.Jerusalem artichoke juice(JAJ)x tomato juice(TJ) and carrot juice(CJ) which are apt to gain and separate. By cell growth experimented, regard JAJ medium as optimal base medium for L.b-DR. At the same tune, it is good for S.t-3 as well. JAJ medium inoculated with S.t-3 cultivated at 37℃ for 16h. The highest courts were 2.8 x 109cfu/ml. Adding 15 kinds of different nutritional factors hi JAJ medium was used to study the effects on L.b-DR cell growth .The result indicated TJ, Lactose, Peptone, CaCO3 can have a significant effect on L.b-DR growth. The orthogonality test were used to screen the optimal enrichment medium for L.b-DR. The proportion of medium is JAJ containing 7.5% TJ, 1.5%lactose, 1% peptone and 0.3% CaCO3. JAJ compound enrichment medium inoculated with L.b-DR cultivated at 37℃ for 16h.The live counts reach 1.5 x 109cfu/ml. Compared with control, live counts in JAJ were increased by 23.93 times. The cost is decreased 1600yuan/t compared with MRS medium used in lab.The effects of culture condition and nutritional medium on resistant freeze of L.b-DR. were studied, The results shows: Cultivated at 37℃, initial pH at 6.0,cell gaining at the end of logarithm and beginning of stable, pH hi protectant at 6.0,Added glycerin 0.1% or VE 0.01%,can dramatically increase the freeze-drying survival rate of L.b-DR.In the Study of the effect of centrifuging force time on the loss rates of Lactic acid bacteria, The optimum centrifugal factor on cell concentration were decided: Centrifugating for L.b-DR and S.t-3 at 3672g(6000r/min) for 10 min. The loss rate of L.b-DR and S.t-3 separately were decreased to 0.05‰ and 0.28‰. The relation of freeze-drying thickness and drying time -, water content of freeze-drying culture were studied. The basic factor of freeze-drying technology were determined. The prescription for 4 kinds of fine mixed protectant were screened. After freeze-drying, the survival rate of L.b-DR and S.t-3 attained above 60% and 80% respectively. The number of live cells of them were over 1 x 109cfu/g. L.b-DR with mixed protectant (37℃) were frozen, the survival rate of cell reach 68.0%. The viable counts get to 4.99 x 109cfu/g. S.t-3 with mixed protectant (46℃) were frozen, The survival rate of cell reach 98.0%, the viable counts attained 1.25 x 10 10cfu/g.By examining the activity of freeze-drying cultures in milk, the result indicates: the mixed freeze-drying cultures were prepared by 4 kinds of find compound protectant; which viable counts reach above 1 x 10 10cuf/g. The fermentation nature is better. Inoculated with 0.01% and cultivated at 42℃ for 4h. The fermented dairy acidity can reach 80°T ~90°T, pH is about 4.5.The yoghurt has nice flavor and taste. Compared with traditional yoghurt, inocul...
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