Analysis Of Microbiota,metabolites And Their Correlation In Caishiji Soybean Paste

As a local traditional famous local product in Anhui Province,Caishiji bean paste(CSP)is made by natural fermentation in the synergistic effect of microorganisms.The raw material was high quality soybean,adding anise,cinnamon,licorice,salt,rock sugar and other spices.In this paper,the basic components,physicochemical properties and flavor metabolites of Anhui Maanshan CSP were detected in the fermentation process,and their dynamic changes were analyzed.Meanwhile the succession,similarity and diversity of the microbiota was explored.Finally,combining with the correlation analysis,the core microbiota that affected the quality of CSP in the fermentation was found out,and the influence mechanism of the core microbiota on the quality of CSP was expounded.The research results provided a basic reference for improving the traditional soybean paste production technology and improving the quality of soybean paste.The main research results are as follows:(1)Analysis of basic components and physicochemical properties of CPS.According to the relevant index detection method of soybean paste,the basic components and physicochemical properties of CSP in the fermentation were detected and analyzed.The results showed that in the fermentation,the contents of protein,fat,moisture decreased gradually;the total acid,amino acid nitrogen and salinity increased gradually;the content of reducing sugar was gradually decreased after reaching its maximum level(5.86 g/100g);the scavenging capacity of DPPH,·OH and O₂^-·and the protease activity and?-amylase activity began to decrease after reaching their respective maximum;while lipase activity remained stable basically.(2)Analysis of volatile flavor compounds and free amino acids of CSP.Amino acid automatic analyzer and GC-MS were used to analyze the flavor substances in the fermentation process.More than 70 kinds of volatile flavor compounds were involved during the fermentation stage,among them,esters,aldehydes and alcohols were the pivotal compounds,which contributed most to the aroma of CSP.The contents of esters,aldehydes and alcohols began to decrease after reaching their respective maximum,while ketones content decreased gradually.Seventeen different type of free amino acids were also involved in CSP,among them,bitter-tasting amino acids were dominant in CSP(27667.38 mg/kg),followed by umami taste and sweet taste amino acids.The content of bitter-tasting amino acids increased first and then decreased,while the content of umami taste and sweet taste amino acids increased gradually.(3)Analysis of microbiota succession of CSP.Using high-throughput sequencing technology,a total of twenty species of bacteria and seventeen species of fungi(relative abundance?1%)were detected in the microbiota analysis during the CSP fermentation process,and the change of microbial diversity was gradually decreased after reaching its maximum level;the dominant genera mainly included Bacillus,Tetragenococcus,Salinivibrio,Halomonas,Staphylococcus and Aspergillus.Among them,the relative abundance of Bacillus increased gradually;Tetragenococcus decreased gradually until disappeared;Salinivibrio,Halomonas and Staphylococcus were down after rising first;Aspergillus remained stable basically.Correlation analysis of microbiota,basic components and flavor metabolites of CSP.According to the correlation analysis,the moisture and salinity may be important factors in determining the distribution of bacterial and fungal communities in CSP;Bacillus exhibited a significantly positive correlation,while Tetragenococcus,Staphylococcus and Aspergillus were negatively correlated with 2-methylbutyraldehyde and some free amino acids,and 3-methylthiopropionaldehyde was positively correlated with fungi in the late stage of fermentation.Through the comprehensive research and analysis of microbiota distribution and succession,the dynamic changes and differences of metabolites,the correlation between microbiota and metabolites,the mechanism of microbial action on the formation of the flavor of CSP was revealed.The research results provide guidance for improving the flavor of CSP and its fermentation regulation.