Analysis of Volatile Flavor Characteristics and Microbial Community Structure in Different Types of Douchi Using GC-IMS and High-Throughput Sequencing

Differences in fermentation processes and microbial communities lead to distinct volatile flavor profiles in douchi, yet the underlying mechanisms remain insufficiently understood. This study combined gas chromatography–ion mobility spectrometry and high-throughput sequencing to characterize volatile compounds and microbial community structures in 3 representative types of douchi. A total of 76 volatile compounds were tentatively identified based on chromatographic retention indices and ion mobility information, including esters, alcohols, aldehydes, ketones, acids, and pyrazines. Class-level comparison revealed distinct volatile profiles among the 3 types of douchi. LYDC exhibited a higher relative contribution of esters and a slightly higher contribution of pyrazines, which were associated with fruity and roasted aromas. TCDC showed higher relative contributions of ketones, alcohols, and aldehydes, including compounds associated with buttery and creamy notes. In contrast, TRDC was predominantly characterized by acids, accompanied by elevated levels of selected aldehydes and alcohols, resulting in a distinctive and complex volatile profile. Microbial community composition varied among the 3 douchi types. Variations in bacterial and fungal diversity, along with the dominance of specific genera such as Bacillus , Weissella , Aspergillus , and Scytalidium , were observed across samples. Exploratory Spearman correlation analysis identified several associations between dominant bacterial and fungal genera and selected volatile compounds, including a limited number of associations that remained significant after FDR correction. These findings revealed preliminary patterns of microbial–volatile co-variation, although the observed relationships could not establish direct microbial contributions to flavor formation.