Microbial Community Structure and Volatile Flavor Composition of High-Temperature Daqu with Different Colors

Aims: This study aimed to compare white (WQ), black (BQ), and yellow (YQ) high-temperature Daqu to determine how color differences correspond to variation in microbial community structure and volatile metabolite profiles, and to elucidate how these factors influence functional performance in Baijiu fermentation. Study Design: This was an experimental, laboratory-based comparative analysis that integrated culture-dependent microbial enumeration, high-throughput sequencing, and volatile profiling to characterize three Daqu types differing in color and fermentation ecology. Place and Duration of Study: The study was conducted at the College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, over three months from December 2024 to February 2025. Methodology: White, black, and yellow Daqu samples were collected and subjected to culture-dependent plate counts, PacBio high-throughput sequencing, and HS-SPME–GC–MS volatile analysis. Microbial abundance, diversity indices, and taxonomic composition were quantified and compared across Daqu types. Volatile compounds were identified and categorized into esters, alcohols, acids, aldehydes, and pyrazines. Microbial metabolite correlations were assessed to reveal functional associations between dominant genera and key aroma compounds. Results: Substantial microbial variation was observed among the Daqu types. WQ exhibited the highest total viable counts, whereas BQ showed reduced microbial abundance, likely attributable to greater thermal stress during maturation. Sequencing identified Kroppenstedtia, Bacillus, Thermoascus, and Thermomyces as core genera, with Saccharopolyspora enriched specifically in BQ. YQ demonstrated the highest microbial richness and evenness. More than 80 volatile compounds were detected across samples. WQ contained elevated alcohols and pyrazines, YQ showed higher concentrations of organic acids, and BQ exhibited increased esters and aldehydes. Strong positive correlations were observed between dominant microbial taxa and their corresponding volatile classes. Conclusion: Daqu color reflects distinct microbial and metabolic functional profiles that shape fermentation behavior and aroma development in Baijiu production. Differences in microbial abundance, community structure, and volatile formation highlight the role of Daqu color as an indicator of fermentation potential. These findings provide scientific guidance for Daqu classification, quality control, and targeted flavor optimization.