The Research Of Technology About Concentrated Starter Of Lactic Acid Bacteria

To provide the datas for industrialization of concentrated lactic acid bacteria and establish the technical process and technics parameter of the lactic acid bacteria concentrated starter, the L.b and S.t optimized were choosen as original culture to study their growth condition, method of enhancement and enrichment bacteria, freeze-drying protection and rehydration.1.The growth conditions of L.b and S.t were compared and studied. The results showed that the OD value of lactic acid bacteria concentrated starter were best with cultivated temperature 42℃. The OD value increment of S.t and L.b were 0.75 and 0.84,and the growth rate were 0.3226 and 0.3005 when inoculation dosage was 2%. The stir procedure was disadvantageous to the growth of lactic acid bacteria because the content of deliquescent oxygen would be increased.2. The effect of flowing added alkali on bacteria enhancement was studied by single factor test. The results indicated that, for the L.b, the 50% ammonia was the best neutralization reagent to controll the pH value during 5.8～6.3. The same to the S.t, and the 15% sodium carbonate neutralization reagent was the best.3. For selecting buffer salt, pH value and dosage optimum, the orthogonal experiment L (3³) was used. The results exhibited that, for the L.b, the pH value had the greatest effect on bacteria enhancement and buffer salts was the second and then was the salt dosage. The optimized group was C₆H₈O₇·H₂O—Na₃C₆H₅ O₇·H₂O buffer, the original pH value and the salt dosage were 6.2 and 5%. As to S.t, the optimized group was Na₂HPO₄—C₆H₈O₇·H₂O buffer, the original pHvalue and dosage were 6.2 and 15%.4.The effects of centrifugation power and centrifugation time on losing rate and livability of lactic acid bacteria were studied in bacteria enrichment study. The result manifested that the most optimum condition parameter for preparing the lactic acid bacteria suspension were 20min, 4000r /min. In addition the application of hollow fibrous film on concentration of lactic acid bacteria thallus was still indefinited.5. Put the suspension samples in different temperatures (-20℃,-30℃and -70℃) to freeze-dried in advanced and the results showed that, the lactic acid had the highest survival rate when the bacteria suspension was freeze-dried at -20℃in advance.6. The effect of different protection agents and their admixtures on the surviving rate were compared. The results indicated that the 10%NFM+5% glycerin was the best protection agents, then the surviving rate of L.b and S.t can reached 46.8% and 75%. 7. The parameter of freeze-drying time was studied by controlling the moisture content and 34h was the appropriate freeze-drying time.8.The mathematics model for suspension's preparation condition was obtained by three factors quadratic rotary combination design:Y₁=33.44+1.66X₁-3.29X₂+9.15X₃-0.51X₁²-2.81X₂²-0.78X₃²+1.33X₁X₂+0.98X₁X₃-3.5 5X₂X₃. the optimized condition parameter for bacteria suspension preparation were acquired according the modle: pH value of protection agents was 6.5, the equation time of protection agents mixed with bacterium mud was 40min and the proportion of protection agents mixed with bacterium mud was 1:1.6.9. The effect of rehydration agents and time on titration acidity, activity and curd state lactic acid bacteria freeze-dried sample were studied. The optimum rehydration reagent was 10%NFM mixed with carrot juice NFM substrate; the optimum rehydration time was 60min. The activity of lactic acid bacteria concentrated starter can be enhanced by reusing the concentrated lactic acid bacteria concentrated starter with appropriate actived condition.