Characterization and correlation analysis of the bacterial composition,physicochemical properties and volatiles in Baijiu fermentation pit mud of different ages

Abstract:

[Background] The quality of pit mud (PM) is one of the critical factors affecting the quality of Luzhou-flavor Baijiu.The physicochemical properties,microbiome,and volatiles determine the quality of PM.[Objective] To reveal the relationship between physicochemical properties,microbiome,and volatiles of PM at different ages.[Methods] The physicochemical properties of growing PM (10 years) and mature PM (30 years) were compared.Volatiles were analyzed by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS).PacBio SMRT high-throughput sequencing was conducted to analyze the microbiome.Spearman’s correlation analysis was performed with the obtained data.[Results] Moisture,available phosphorus and potassium,and the key flavor volatiles (caproic acid,ethyl caproate,and ethyl butyrate) in mature PM were higher than those in growing PM,whereas lactic acid and hexanol showed the opposite trend.Proteiniphilum and Petrimonas(Bacteroidia) were most abundant in growing PM,whereas Caproiciproducens and Clostridium(Clostridia) were most abundant in mature PM.The relative abundance of Clostridia(Caproiciproducens and Clostridium) was positively correlated with the content of caproic acid and ethyl caproate,and negatively correlated with the content of lactic acid.The physicochemical properties of PM influenced most species of Clostridia in PM.Moisture and available phosphorus and potassium were positively correlated with the content of key volatiles and the relative abundance of Clostridia.[Conclusion] Moisture,available phosphorus and potassium are the key factors affecting both the composition of Clostridia and the content of key volatiles (caproic acid and ethyl caproate) in Luzhou-flavor Baijiu.These findings improve our understanding of the microbial succession and volatile profile in PM,which facilitates the fermentation regulation and PM quality improvement of Luzhou-flavor Baijiu.

Key words:pit mud;physicochemical properties;volatiles;microbial community;Spearman correlation