Fermentation Characteristics Of Strains In Sufu And The Preparation Of Starter Cultures

Sufu is a Chinese traditional fermented soybean product. The research of sufu strain characteristics help to solve the problem of long sufu fermentation cycle and the unstable quality through pure inoculation fermentation method. Kedong sufu is fermented food type of bacteria typical of rich microbial types. In previous studies, this thesis mainly evaluates on Kedong sufu isolated 143 strains fermented characterization, identifying the strains with good fermentation characteristics which are made into fermentation agent. This thesis mainly makes PH, acidity, amino nitrogen, soluble protein and activity of lipase fermentation characteristics as index and evaluates the Sufu strain; Then it applies principal component analysis, hierachical cluster analysis and single factor analysis and chooses optimal fermentative strains with good fermentation characteristics. It makes use of morphological and 16Sr-RNA sequencing technology to identify dominant strains and uses the technology of fermentation engineering to optimize the culture conditions on the dominant strain proliferation, and optimizes the dominant strains by D-optimal mixture design. On this basis, using good properties of strains which compose fermentation agent to prepare sufu.Two principal components of Principal component analysis can explain 62.322% of the strains fermentation characteristics, and also can fully reflect the whole characteristics of 143 strains. The first principal component is divided into amino acid nitrogen and soluble protein, the contribution rate of which is 35.311%. The second principal component is p H, the contribution rate of which is 27.011%. According to the above factors, this thesis selects three strains which have good fermentation characteristics, including number 143, 43 and 25 strains respectively; In the process of the hierarchical clustering analysis, the total number of number 143 bacterial, amino nitrogen and soluble protein are prominent in Ⅲ type serial, and number 43 and number 25 have rich amino acid nitrogen content.Number 43, 25 and 143 strains are all gram positive strains of staphylococcus aureus. identified by 16Sr-RNA It is found that NO.143 and C micrococcus, NO.43 and A micrococcus, NO.25 and B micrococcus are highly homologous, and it is confirmed that NO.143, NO.43 and NO.25 strains are C micrococcus, A micrococcus and B micrococcus respectively from the perspective of molecular systematic.A micrococcus optimum temperature is 30°C, p H 8.0 and speed 150r/min. The addition amount of maltose of medium optimization of proliferation is 15.8g/L, yeast extract:soy peptone=1:1 additional amount is 68.8g/L, and dipotassium hydrogen additional amount is 4.9g/L. Cultured in the above conditions, the viable cell count of A micrococcus actually measured is 5.62×109CFU/m L; B micrococcus optimum temperature is 30°C, p H 8.0, speed 150r/min. The additional amount of maltose of medium optimization of proliferation is 15.4g/L, yeast extract:peptone=1:3 additional amount is 69.4g/L, and adding amount of sodium citrate is 4.8g/L. Cultured in the above conditions, the number of viable cells in the actual measured is 6.89×109CFU/m L; C micrococcus optimum temperature is 30°C, p H 8.0, speed 150r/min. The adding amount of sucrose of medium optimization of proliferation is 14.8g/L, yeast extract:soy peptone=1:1 additional amount is 28.1g/L, and dipotassium hydrogen additional amount is 7.3g/L. According to the previous conditions, the viable cell count actually measured is 5.45×109CFU/m L.The compound proportion of 143, 43 and 25 strains were optimized through D-optimal mixture design method. The research results show that when the initial total number of bacteria NO.143:NO.43:NO.25 is 67.00:2.40:3.06, determination of the three main ingredients of p H 7.30, amino acid nitrogen is 0.31g/100 g, soluble protein is 21.20μg/m L respectively.Compound with starter preparation fermented sufu, and complex fermented sufu samples and traditional methods fermented sufu samples from different fermentation periods measured, the results show that the preparation of fermented sufu samples composed by the previous three strains, when fermented for 120 days, the moisture content, amino nitrogen and acidity are 48.13%(<72%)、0.56g/100g(>0.45g/100g)and 0.63g/100g(total acid <1.2g/100g), which are the requirements of national standard(SB/T 10170-2007). Analysis of texture characteristics results tend to be 171.00 g for hardness, adhesiveness reaches 13.73 gsec, and the changes of elastic stability decline. It is similar to the traditional fermentation preparation method of Sufu samples in the indicators and the quality, and the constitutive characteristics of 150 days. The research results of this paper provide reliable data support for the subsequent fermentation experiment.