The Technology Of Direct Vat Set Starter For Fermented Acidic Whey Tofu

Fermented acidic whey as coagulant is one of the most important links in making fermented acidic whey tofu.The quality of fermented acidic whey tofu can be guaranteed by the variety and quantity of lactic acid bacteria.In order to produce high-efficiency and high-quality fermented acidic whey,it has become a research hotspot to combine the selected dominant strains with commercial strains to ferment acidic whey.However,the activity of the dominant bacteria isolated from the natural fermented acid whey is low,the liquid lactic acid bacteria is not conducive to transportation,and the activity generally decreases rapidly with the storage time.The activation and extended culture of the strain increased the production cost.In this study,high-density cultivation was carried out on the dominant strains isolated from fermented acidic whey.The high-concentration lactic acid bacteria used in fermentation of fermented acidic whey were prepared into mixed bacteria powder,optimizing the preparation process of the bacteria agent to ensure the survival rate of the bacteria agent for the production of high-activity bacteria agent,making the production of fermented acidic whey Tofu more convenient.The main results are as follows:The optimal culture conditions of Lactobacillus delbrueckii HCUL 1.1801-1912 which isolated from Yunnan natural fermented acid whey by using the stable strain density on stable period as an index were as follow:the culture temperature was 37℃,the initial PH was 6.5,and the inoculation amount was 5×10⁶cfu/m L.Based on bouillon culture medium,The nutrient contents of Culture medium were as follows:Glucose 10 g/L,sucrose 10 g/L,yeast extract 24g/L,beef extract 5 g/L,peptone 16 g/L,Mn SO₄0.1g/L,Mg SO₄0.1g/L,Na₂HPO₄g/L,citric acid 4 g/L,growth-promoting factor is soybean powder 0.1 g/L.Compared with MRS,the density of bacterial increased from 8.4×10⁸cfu/m L to 7.1×10¹⁰cfu/m L.The effects of centrifugation and freeze-drying conditions on the survival rate of strain was studied.The results showed that the optimum conditions of centrifugation for HCUL1.1801-1912 was 6000rpm 10min,1.2472 was 8000rpm 10min,1.2718 was 6000rpm 10min.The mycelium yield was 90.59%,86.38%and 90.28%.The freeze-drying condition of mixed fungus powder was-80℃for 24 hours.The survival rate of HCUL 1.1801-1912 was used as the index to study the protective effect of different protectants on the strain,the survival rates of 1.2472 and 1.2718 were tested.Taking the freeze-drying survival rate of isolated strains as an index,the optimum addition amount of single protective agent was determined according to the single factor test,and the defatted milk powder and maltose were mixed with other protective agents in different proportions according to the protective effect,the optimal ratio of the protective agent（W/V）was 11.6%maltose,10.2%yeast extract and 5.3%trehalose,which was obtained by response surface methodology,the freeze-drying survival rate of the mixed powder could reach83.07%.The effects of stress treatment before freeze-drying,p H and storage temperature on the activity of bacterial powder were studied by using the survival rate of bacterial powder as an index.The bacterial powder produced by the optimized technology has a long effective period and can be used for the production of ermented acidic whey tofu instead of the bacterial liquid.