Study On High Effective Lyophilized Lactic Acid Starter Culture Concentrates

A primary medium which was on the basis of cucumber juice was prepared by adding 2% glucose, 0.5% peptone. The fermentative ability of five lactic acid bacteria was studied, which affirmed two strains as the primary fermentative species. Taking pH value and living cell count as indexes in the process of fermentation, the experiment had studied strain ratios, cultural medium components, cultivation conditions, enrichment methods and cryoprotectant. The purpose is to provide experimental basis for direct-to-vat culture starters. The results indicated:1. Two strains (A and D) showed good mutual fermentation character and when the ratio of the two strains' amount was 1:1, acid content and living cell count were higher than other strain ratio.2. Fermentation experiment indicated: the optimum carbon source was glucose, the optimum nitrogen source was peptone, growth factor was tomato juice. According to orthogonal experiment, the optimal medium contained the following ingredients: 2% glucose, 1% peotone, 5%tomato juice, 10% phosphate and 1% Tween 80.3. Seed volume was 3%, the incubation temperature was 30 C, Na2CO3 was used to control initial pH at 6.6, cultural fluid amount is 40mL, shaking culture with rotating speed 120 rotation per minute was used, after 14 hours' culture, nutrient substance was added to the medium and the cell population got to 7.24 + 109cfu/mL, after 20 hours' culture.Master Degree Dissertation: Study on High Effective Lyophilized Lactic Acid Starter Culture Concentrates4. After 20 hours' culture, lactic acid bacteria cells were harvested by centrifugation. Results indicated that the best effect could be obtained at 4 C with 4000 r/min for 30 min .5. Using 10% nonfat dried-milk as suspended substrate, the function of four protectors including sucrose, serum protein, glycerin and trehalose were studied. Results suggested that all of them had some effects on promoting cell count and glycerin was the best one.6. The cell suspension in 10% nonfat dried milk containing the suitable protector might be lyophilized into the lactic acid bacteria powder with high viability (the number of viable cell 3.4 + 1010cfu/g).7. The RP-F bags containing the dry starter concentrated were sealed under vacuum, stored at 4 C for 60 days. Culture starter had little effect on cell count.8. By culture starter quality test, we studied the culture starter application feature. Compared with tradition fluid culture starter, the seed volume of freeze-drying culture starter reduced 100 times. Freeze-drying culture starter produced quickly acid through long lag phase, but acid-produced amount was as well as liquid culture starter's . The pickle by freeze-drying culture had good in color, smell and taste.