Microbial Diversity And Quality Analysis Of Natural Fermented Soybean Paste

The topic is to study the three naturally fermented soybean pastes as the object.The basic physical and chemical indicators of soybean paste detection by the national standard,the application of electronic tongue analysis of the taste characteristics of soybean paste,and high-throughput sequencing analysis of microbial diversity in the fermentation process of soybean paste,further analysis of the correlation between physical and chemical indicators,taste characteristics and microbial diversity,it provides the basis for promoting soybean paste technology and protecting microbial resources.(1)Detection of changes in physical and chemical indicators during the fermentation of three soybean paste by national standard,to ensure the accuracy of experiments,take the average of physical and chemical indicators of the three soybean paste.In the process of natural fermentation of soybean paste,the value of water and pH decreased and then remained stable,fermentation maturity index of fermentation was 66.7% and 5.24;The content of amino nitrogen,fat and protein increased and then stabilized,fermentation maturity indexes were 0.919g/100 g,3.92g/100 g and 10.47g/100g;The content of nitrite,total acid and total sugar increased first and then decreased,and the fermentation maturity indexes were 4.65mg/kg,0.967g/100 g and 1.87g/100g;The content of sodium chloride floats up and down between 11.58~12.45g/100 g during the whole fermentation process.(2)Application of electronic tongue to analyze the flavor characteristics of fermented soybean paste,explore the interrelationships between by correlation analysis and regression analysis.The electronic tongue analysis of soybean paste tastes salty and fresh as a whole.With the increase of fermentation time,the umami,aftertaste-B,aftertaste-A,saltiness,bitterness,and richness of soybean paste weaken,sourness and astringentcy enhancement;There is a very significant or significant correlation in one or more indicators of taste and physicochemical properties,for example,sourness,astringency with pH show extremely negative correlations,significant positive correlation between umami,abundance and saltiness with pH.(3)Using high-throughput sequencing techniques to study microbial relationships between meju and soybean paste of microbial,the predominance of phyla in the meju and soybean paste is basically the same;the dominant fungal genus in meju and soybean paste is Penicillium;Proteobacteria in meju and there are far greater than the proportion of Proteobacteria in soybean paste;Tetragenococcus is very little in meju,and it become the dominant bacteria in the fermentation of soybean paste.(4)Physical and chemical indicators,taste characteristics with microbial correlation analysis,the influence of the bacteria on the physical and chemical indicators and taste characteristics was greater than the effect of the fungus on the taste characteristics.