Unraveling the correlation between physicochemical properties, volatile flavor compounds, and microbial communities during the fermentation of Aspergillus-type douchi

Abstract

As a traditional fermented food, Aspergillus-type Douchi develops its characteristic flavor through natural fermentation in a semi-open environment. However, the extensive production methods traditionally employed for Aspergillus-type Douchi often result in inconsistent quality and increased contamination risks. This study utilized headspace solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography-mass spectrometry and high-throughput sequencing techniques to elucidate the dynamic succession of volatile flavor compounds and microbial communities during the fermentation of Aspergillus-type Douchi. The results demonstrated that the total organic acid content increased steadily from 23.33 mg/g to 64.03 mg/g, predominantly comprising succinic acid, lactic acid, and citric acid. Free amino acid levels exhibited an initial rise followed by a decline, with umami amino acids consistently dominating. Alcohols, esters, aldehydes, and acids were the predominant flavor compounds in Aspergillus-type Douchi, with 36 identified as key volatile flavor compounds (VIP >1, p < 0.05). In the microbial community, bacterial communities dominated by Firmicutes, Proteobacteria, and Bacteroidota were the principal fermenting microbiota, whereas fungal communities were predominantly composed of Ascomycota. Correlation analysis results indicated that pH and total acidity were the primary environmental factors influencing bacterial communities, while amino acid nitrogen significantly impacted fungal communities. Furthermore, Corynebacterium, Bacteroides, Wickerhamomyces, Bacillus, Lactobacillus, and Staphylococcus exhibited highly significant positive correlations with at least four key volatile flavor compounds, suggesting their roles as core functional microbiota shaping the distinctive flavor profile of Aspergillus-type Douchi. This research provids a theoretical foundation for targeted quality control and the screening of novel fermentation cultures for Aspergillus-type Douchi.