Comparative analysis of microbial communities and flavor compounds in fermented grains from different sorghum varieties used in Sichuan Xiaoqu liquor

Sorghum is the primary raw material for liquor brewing, and its increasing cost has significantly impacted liquor manufacturers. In response, the industry is exploring the possibility of using low-cost imported sorghum as an alternative to domestic sorghum. The present study monitored the physicochemical properties, flavor components, and microbial community structure of fermented grains during the fermentation of Australian sorghum (AS) and Northeastern sorghum (DS) in real-time. Additionally, the correlation between microbial communities and the flavor of Xiaoqu liquor was investigated. Fermentation was analyzed over five periods: 0, 2, 4, 6, and 8 days. The reducing sugar content of DS was significantly higher than that of AS in the early stage, while the starch content remained consistently higher than that of DS. The acidity of both fermented grains showed an increasing trend, whereas moisture content and fermentation temperature remained relatively stable. A total of 52 flavor compounds were detected, with alcohols being the most abundant aroma compounds. The three most differentiated volatile flavor compounds were [V3] isopentyl formate, [V26] 6-methylheptan-1-ol, and [V16] 9-hexadecenoic acid, ethyl ester. A total of 90 bacterial and 46 fungal genera were identified. The dominant bacterial genera in AS were Lactobacillus, Bacillus, Pediococcus , and Acinetobacter , while the dominant fungal genera were Saccharomyces, Saccharomycopsis , and Cutaneotrichosporon . In DS, the dominant bacterial genera were Lactobacillus, Bacillus, Pediococcus , and Enterobacter , while Saccharomyces and Saccharomycopsis were the dominant fungal genera. The AS bacterial community showed stronger microbial interactions, resulting in a more complex and tightly interconnected bacterial network, whereas its fungal network structure remained relatively simple. Correlation analyses further demonstrated that alcohols and hydrocarbons were strongly correlated with bacterial metabolic activity, and AS microorganisms exhibited weaker correlations with flavor compounds. This study provides a comprehensive comparison of the fermentation characteristics of AS and DS, offering a theoretical foundation and valuable data for optimizing the use of Australian sorghum in Xiaoqu liquor production. • For the first time, the dynamics of fermentation grains indicators in Australian sorghum Xiaoqu liquor were investigated. • A total of 13 volatile flavor compounds exhibited significant differences between the two types of fermented grains. • Lactobacillus, Bacillus, Pediococcus, Saccharomyces, and Saccharomycopsis are the core microorganisms in the fermentation process. • The bacterial community structure of Australian fermented grains is more complex, but its fungal community is simpler.