Storage time drives divergent microbial functions and flavor metabolism in high-temperature Daqu

Baijiu is a traditional Chinese distilled liquor, whose unique flavor highly relies on the synergistic metabolism of diverse microbial communities during the brewing process. The high-temperature Daqu (HTD) used in sauce-flavor Baijiu plays a crucial role in flavor synthesis due to its enrichment of heat-resistant functional microbiota. However, traditional techniques have limited understanding of microbial community succession and functional dynamics during Daqu storage, hindering precise quality and flavor regulation. This study systematically investigated the dynamic evolution of physicochemical indexes, microbial community structure, metabolic functions, and flavor compounds in HTD during different storage periods (1st, 3rd, and 6th months) through integrated metagenomics and GC-MS metabolomics. Results showed continuous decreases in moisture, starch, and pH during storage, while aminopeptide nitrogen and acidity peaked at the 3rd month. Esters reached their highest levels at the 1st month (YQ), alcohols peaked at the 3rd month (EQ), and aldehydes dominated at the 6th month (SQ). LEfSe analysis identified Kroppenstedtia eburnea and Paecilomyces variotii as biomarkers for YQ, Saccharopolyspora rectivirgula and Aspergillus chevalieri for EQ, and Rasamsonia emersonii for SQ. Metagenomic analysis revealed differential carbohydrate and amino acid metabolism pathways: YQ showed highest enzyme abundance for phenethyl alcohol metabolism, EQ exhibited peak enzymes for pyrazine synthesis and ethanol metabolism, while SQ demonstrated superior glucoamylase activity. In addition, maximum tetramethylpyrazine at the 3rd month and highest microbial diversity in later storage (6th month).