Dynamic Changes of Physicochemical Quality, Flavor and Fungal Community Structure during Medium-High Temperature Daqu Fermentation Process in Xufang Region

In this study, medium-high temperature Daqu (MHTD), the primary saccharification and fermentation agent in the production of strong-aroma Baijiu, was investigated across different fermentation stages. Employing national standard methods, artificial intelligence sensing technology, and high-throughput sequencing techniques, a comprehensive analysis was conducted to investigate the physicochemical properties, flavor, taste, and changes in fungal community structure during the MHTD fermentation process. The correlation between quality indicators of MHTD and dominant fungal genera was also explored. The results revealed that, during fermentation, the moisture content, levels of organic sulfur compounds, terpenes, hydroxides, and astringency gradually decreased in MHTD, while saltiness steadily increased. The fungal community structure of MHTD was established in the early stages of fermentation. However, as fermentation progressed, fungal community diversity gradually decreased, accompanied by significant changes in the relative abundance of certain genera. Specifically, the relative abundance of Saccharomycopsis gradually decreased, while Thermoascus and Candida increased, becoming dominant in the later stages of fermentation. Procrustes analysis and correlation analyses indicated a significant correlation (P<0.05) between fungal community structure and flavor and taste indicators of MHTD. Specifically, Saccharomyces showed a close relationship with the synthesis of aromatic compounds, alkane aromatic components, and ethanol in Daqu. Thermoascus, on the other hand, might play a role in inhibiting the production of organic sulfur compounds and terpene compounds. The genus Rhizopus demonstrated inhibitory effects on the formation of astringent substances. This study enhances the understanding of the dynamics of fungal communities and quality changes during MHTD production, providing valuable insights for improving production processes and enhancing product quality for relevant industries.