Multi-omics study on traditional Xiaoqu of Fangxian Huangjiu: Unveiling interactions among physicochemical factors, microbiome and volatile flavor compounds

Xiaoqu is the key fermentation starter of Huangjiu, with its microbial profile closely linking to the flavor quality. This study investigated Fangxian Xiaoqu (FXXQ) and corresponding Fangxian Huangjiu (FXHJ) by physicochemical analysis, microbiomics, and flavoromics. Results showed significant variations in physicochemical properties, with Weissella and Saccharomycopsis identified as dominant bacteria and fungi, respectively. A total of 255 bacterial and 151 fungal differential taxa in FXXQ were identified, as well as 76 volatile flavor compounds in FXHJ, including ten newly reported for FXHJ. Correlation analysis revealed acid protease activity as the most critical physicochemical factor shaping bacterial communities, while alcohol-producing capacity dominated fungal communities. Esters content was positively correlated with the abundances of Leuconostoc and Staphylococcus, and alcohols content with that of Saccharomycopsis. This study provides theoretical support for standardizing the preparation of FXXQ and regulating the flavor of the final FXHJ product.