Analysis of Microbial Dynamic Succession and Its Correlation with Flavor Metabolites During the Full Fermentation Cycle of Traditionally Gray Sufu

Taking grag Sufu inoculated with Mucor UV-M2 as the research object, the changes of volatile metabolites, microorganisms and their correlation during fermentation of grag Sufu were explored. In this study, the quality of the fermentation process was comprehensively evaluated using physicochemical indexes and sensory assessment methods. The results confirmed that the fermentation process reached an optimal state after 40 days. Non-targeted volatile metabolomics analysis revealed significant variations in metabolites at different fermentation stages. Based on the odor threshold, 18 compounds with an odor activity value (OAV)>1 were evaluated. Among them, 11 compounds contributed to the aroma profile, including esters, aldehydes, and ketones, while 7 compounds were associated with unpleasant odors, mainly sulfur-containing compounds. Microbiological analysis demonstrated that the diversity of fungi and bacteria decreased significantly as the fermentation progressed. Through Spearman correlation analysis, it was found that the bacteria Tetragenococcus and Halanaerobium exhibited positive correlations with most volatile compounds with OAV>1, whereas Acinetobacter showed negative correlations with these compounds. Among fungi, Mortierella, Aspergillus, Malassezia, Botrytis, Penicillium, and Sagenomella were positively correlated with most of the compounds, while Actinomucor and Candida showed negative correlations. Furthermore, the results of redundancy analysis (RDA) indicated that, among bacteria, Weissella and other genera were positively correlated with salt content. In the fungal community, amino-acid nitrogen was positively correlated with Mortierella, salt content was positively correlated with Actinomucor, and pH was positively correlated with Kodamaea. These findings suggest that the quality indexes of gray Sufu are positively associated with the core microbial flora. Overall, the above results indicate a significant correlation between the aroma characteristics and the microbial community at different stages during the fermentation of gray Sufu. This study provides valuable references for enhancing the flavor quality of gray Sufu through microbial regulation techniques.