Study On The Microorganisms And Flavor Substances In The Fermentation Of Soybean-flavor Liquor

Soybean-flavor liquor is unique to the Pearl River Delta region.It has local characteristics and is popular among consumers.Since the 1970 s,scholars have continued to study the microorganisms and flavor substances of soybean-flavor liquor,but most of the research has focused on the finished liquor or the base liquor.There are few reports on the microbial community and flavor substances in the fermentation process of soybean-flavor liquor.This paper mainly studied the types and evolution of microbial community,and the changes of flavor substances in the fermentation process of soybean-flavor liquor,and then discussed the correlation between microorganisms and flavor substances.The main conclusions were as follows:1.The high-throughput sequencing technology was used to study the bacterial and fungal microbial structure of the liquor starter and fermentation process of soybean-flavor liquor.The results showed that both bacteria and fungi had rich diversity in the liquor starter and fermentation process,and the diversity of bacteria was greater than that of fungi.In the analysis of the bacterial flora,the main dominant bacteria in the liquor starter were Lactobacillus and Weissella;the dominant bacteria in the fermentation process were Lactobacillus,Pediococcus,Lactococcus,Weissella and Enterobacter,all of which came from liquor starter.Among them,Lactobacillus gradually increased in the fermentation process and became the absolute dominant genus,with an average relative abundance of78 %.In the analysis of the fungal flora,the main dominant fungi in liquor starter were Rhizopus and Saccharomycopsis;the dominant fungi in the fermentation process were Saccharomyces,Trichosporon,Diutina,and Saccharomycopsis,among which Trichosporon and Diutina,were from the environment.Saccharomyces increased first and then decreased in the fermentation process,and was always the most dominant genus,with an average relative abundance of 92 %.2.The dynamic changes of organic acids and amino acids in the fermentation process of soybean-flavor liquor were studied by using HPLC and automatic amino acid analyzer.The results showed that the content of organic acids and amino acids gradually increased during the fermentation process,and the total range of change was: 8.30-30.88 mg/L and1473.3-5127.4 mg/kg,of which lactic acid,acetic acid and succinic acid were the main organic acids;Glu,Ala,Val,Leu and Phe were the main amino acids.3.The HS-SPME-GC-MS technology was used to study the volatile flavor substancesin the soybean-flavor liquor starter,rice and fermentation process.The results showed that61 kinds of volatile flavor substances were detected in the liquor starter,among which the number and content of alcohols,esters and aldehydes were more.A total of 54 kinds of volatile flavor substances were detected in the rice,among which the number and content of hydrocarbons(alkanes and olefins)were the most.During the fermentation process,a total of 72 volatile flavor substances were detected,among which alcohols and esters accounted for a large proportion.The content of alcohols increased rapidly from 92.08mg/kg to 141.09 mg/kg in the first 3 days,decreased sharply to 94.22 mg/kg in the third to fifth days,and then increased steadily to 113.39 mg/kg.The ester content increased from25.9 mg/kg to 35.93 mg/kg.Aldehydes accounted for a small proportion,and the content of aldehydes decreased sharply from 6.1 mg/kg to 1.82 mg/kg in the first 2 days,and then increased steadily to 3.07 mg/kg.In the fermentation process,there were 24 volatile flavor substances with OAV > 1,among which 1-octen-3-one,ethyl caprylate,ethyl caproate andβ-phenylethanol contributed a lot.4.The CorrelationCalculator was used to study the correlation between microbial flora and flavor substances in the fermentation of soybean-flavor liquor.The results showed that there was a good correlation between microbial flora and flavor substances.The bacteria with strong correlation with flavor substances were mainly Lactobacillus,Weissella,Rhodococcus,Pediococcus,Enterococcus,Lactococcus,Leuconostoc,and mainly Lactobacillus.The fungi with strong correlation with flavor substances were mainly Diutina,Candida,Zygosaccharomyces,Saccharomycopsis,Kluyveromyces,Naumovozyma,Rasamsonia,Saccharomyces,Torulaspora,and mainly Saccharomyces.