Study On Key Flavor Substances Of Sichuan Bran Vinegar And Their Correlation With Brewing Microorganisms

Sichuan bran vinegar,as one of China’s four famous vinegars,has a long history.It uses bran as the main raw material and Chinese herbal medicine vinegar as the saccharification agent.It is first produced by vinegar and porridge,then solid-state saccharification,alcoholization and acetic acid fermentation,and finally by aging and vinegar.However,the production of Sichuan bran vinegar is still in a relatively extensive experience stage,and the mechanism of the formation of microbial bacteria and flavor substances in the production process is not very clear.Therefore,this paper uses key techniques such as high performance liquid chromatography and gas chromatography-mass spectrometry to determine the key flavor substances of Sichuan bran vinegar,and uses second-generation gene sequencing technology to explore the bacterial colony diversity of brewing microorganisms,and preliminary analysis of the two Correlation.The results are as follows:The determination of the key flavor substances in Sichuan bran vinegar showed that among the finished vinegars of different varieties,lactic acid was the highest acid except acetic acid,and lactic acid showed a high correlation with Sichuan bran vinegar.Secondly,the measurement results of volatile substances in Sichuan bran vinegar showed that 89 kinds of volatile substances were detected in Sichuan bran vinegar.Among them,furfural,acetic acid,phenethyl acetate,2,3-butanediol,and butyric acid are the main aroma components of Sichuan bran vinegar,and 5-methylfuran aldehyde and phenethyl alcohol have an important contribution to the overall flavor of Sichuan bran vinegar.Comparing Sichuan bran vinegar with field vinegar,it was found that Sichuan bran vinegar has 5 unique ingredients,which are 2-acetylfuran,2,3-butanediol,5-methylfuranaldehyde,ethyl phenylacetate,butyric acid.Further analysis of the content of these five unique ingredients showed that butyric acid and 2,3-butanediol were the characteristic volatile flavor substances of Sichuan bran vinegar.During the solid state fermentation of Sichuan bran vinegar,the content of acetic acid and lactic acid is relatively high.It has a correlation with lactic acid in the early stage of fermentation and acetic acid in the later stage.A total of 50 kinds of volatile substances were detected during the fermentation of Sichuan bran vinegar.Through principal component analysis,it was found that butyric acid,ethyl phenylacetate,etc.are the main flavor substances in the fermentation process,isoamyl acetate,acetoin,etc.are important flavor substances in the fermentation process.The measurement of the physical and chemical indicators during the fermentation process showed that the moisture content changed little throughout the fermentation process.In the early stage of fermentation,the alcohol level,total acid,volatile acid,total sugar,reducing sugar,and amino nitrogen increased.The protease activity value began to increase after a short decrease,and the saccharification enzyme activity value decreased.In the middle of fermentation,alcoholization is the main factor.The growth rate of total acid,volatile acid and amino nitrogen slows down,the alcohol level increases,and the total sugar and reducing sugar decrease.Bacteria are also inhibited and reduced.In the later stage of fermentation,vinegar is the main factor.Volatile and total acids increase,alcohol level decreases,saccharification enzyme and protease activity values are lower,and total sugar and reducing sugar change less during this period.The growth rate of amino nitrogen slowed down.The bacterial diversity and the correlation with environmental factors and flavor substances in the fermentation process of Sichuan bran vinegar were analyzed.The changes of shannon index and ace index showed that the bacterial species were the most abundant at the beginning of fermentation.As the fermentation progressed,the abundance and diversity began to decrease,and they were at a higher position at the end.Lactobacillus and Acetobacter are the dominant bacteria in the fermentation process.In addition,there are some low-abundance but accompanied by the entire fermentation process such as Gluconobacter,Pseudomonas and Bacillus.Through CCA analysis,a correlation analysis at the OTU classification level found that the acidity was negatively correlated with the 7 days before fermentation,and gradually decreased with the fermentation time,and was positively correlated with the 9th to 12 th days of fermentation,but related The sex is small,and it has a strong positive correlation with the 23 rd day of fermentation.The degree of alcohol has a negative correlation with the first 5 days,and as the fermentation progresses,the correlation decreases.It has a weak positive correlation with the 7-21 days of fermentation and a strong positive correlation with the 23 rd day of fermentation.Acetic acid and succinic acid have a positive correlation,and the correlation with bacterial colonies is similar to acidity.Butyric acid and ethyl phenylacetate had a positive correlation.They were positively correlated with the 7 days before the fermentation process and negatively correlated with the 9-23 days.Among them,there was a strong negative correlation with the 23 rd day of fermentation.