Multi-omics analysis reveals the mechanism underlying microbial-driven flavor formation in fermented xuecai (Brassica juncea var. multiceps).

The unique flavor of xuecai stems from microbial metabolism, but how microbial community evolution is connected to fermentative flavor formation remains unclear. In this study, a comprehensive analysis of xuecai fermentation was conducted via untargeted metabolomics, microbiomics, and biochemical techniques to investigate the relationships among its physicochemical properties, flavor compounds, and microbial communities. Nontargeted metabolomics revealed 113 volatile flavor compounds, including 14 aldehydes, 38 alcohols, 37 esters, 11 ketones, and 13 phenols, and the overall flavor and nutritional quality of xuecai reached an optimal state after 32 days of fermentation. A correlation analysis of the microbial communities and physicochemical indicators showed that Companilactobacillus, Weissella, Latilactobacillus, Debaryomyces, and Hannaella were the core microbial taxa driving flavor formation; specifically, Companilactobacillus, Weissella, and Debaryomyces exhibited positive correlations with 3 volatile flavor compounds and 15 amino acids. Furthermore, structural equation modeling (SEM) demonstrated the direct role of microbial communities in shaping the flavor profile of fermented xuecai. This study reveals the dynamic mechanism underlying flavor formation during xuecai fermentation and provides new insights into microbe-mediated fermentation process optimization in industrial production.