Isolation And Identification Of Microorganisms In Naturally Fermented Tofu Whey And Process Optimization Of Naturally Fermented Tofu

In order to study the biological role of microbial community in the formation of naturally fermented tofu and the flavor formation mechanism of naturally fermented tofu,this paper uses high-throughput sequencing technology and traditional separation and purification methods to separate and identify the microorganisms in naturally fermented tofu whey,and determine the best technological conditions of the naturally fermented tofu whey in the naturally fermented tofu.This provides a theoretical premise for the development of the naturally fermented tofu from the small workshop production mode to the expanded commercial production mode.The results are as follows:1 The results of high-throughput sequencing showed that there were 43,944 valid sequences,including 4 phylum,5 classes,9 orders,10 families,13 genera and 17 species in the samples of the naturally fermented tofu whey.According to the number of OTU species classification,the total number of OTU of lactobacillus was the largest and was 43318,and the total number of OTU of lactobacillus was in a dominant position.Through the analysis of rank-abundance curve,we can find that there were dominant flora in the sample and the sample diversity was low.The dilution curve showed that the sample data was reasonable.The community composition of the samples showed that the species of lactobacillus accounted for the highest proportion.It can be concluded from evolutionary analysis that there were genetic relationships among various microorganisms in the naturally fermented tofu whey.The functional prediction analysis revealed that the pathway levels in the samples were mainly related to the metabolism of sugars and lipids.In conclusion,lactobacillus is the dominant bacteria in the composition of the microbial community of the naturally fermented tofu whey.2 The traditional method of separation and purification was used to firstly narrow the range by microbial enrichment and bacterial screening of the original solution,and then separate and purify the single lactobacillus from the naturally fermented tofu whey.In different aerobic and anaerobic environments,66 strains of lactobacillus were isolated,among which 36 strains were aerobic bacteria and 30 strains were anaerobic or facultative anaerobic bacteria.Three kinds of lactobacillus L1,L2 and L3 with good identification results were identified from 66 strains of lactobacillus through biochemical identification with API 50 CHL lactobacillus identification kit,among which L1 was Leuconostoc lactis,with a total of 27 strains.L2 was Lactobacillus delbrueckii ssp.lactis,with a total of 13 strains.L3 was Lactobacillus plantarum with a total of 26 strains.3 Three strains with good identification results were selected from the three identified lactobacillus,and four factor levels were set as the index to conduct single-factor test and response surface test.By four single factor experiment it is concluded that lactobacillus bacteria liquid ratio,quantity of lactic acid bacteria,lactic acid bacteria fermentation temperature and fermentation time of all affect the sensory score.The optimal proportion of lactobacillus solution was the mixture of lactobacillus L2 and L3,that is,Lactobacillus delbrueckii ssp.lactisl and lactobacillus plantarum were mixed at a ratio of 1:1.The optimal conditions for the inoculation amount of lactobacillus were 11%,the optimal fermentation temperature of lactobacillus was 37?,and the optimal fermentation time of lactobacillus was 24 h.The optimal process parameters obtained by response surface test are mixing L2 and L3 in 1:1,the inoculation amount is 11.4%,the temperature is 37.08?,and the time is 24 h and 46 min,which can be applied in practice.