Abstract
Aldehyde compounds are crucial for the flavor profile of Baijiu; however, their metabolic interplay with microbial communities remains inadequately understood. This study demonstrates that the dynamics of aldehydes during Sauce-Flavor Baijiu (SFB) fermentation are primarily driven by stage-specific microbial activities. Based on microbial succession patterns, the fermentation process was divided into early (0-7 days) and late (20-30 days) stages. Seven major aldehydes were identified, with furfural being the dominant component, accounting for over 70% of the total aldehyde content. An integrated Environmental-Microbe-Flavor analysis systematically revealed stage-dependent microbial-metabolite interactions. In the early stage, dominant microorganisms such as Fusarium and Apiotrichum scarabaeorum consumed substrates including starch and reducing sugars. Their growth was strongly promoted by increasing ethanol levels and temperature, thereby accelerating aldehyde transformation. As fermentation progressed, moisture emerged as a key regulatory factor, showing a significant negative correlation with Paenibacillus, suggesting that moisture may shape aldehyde metabolism by modulating microbial community structure. Further moisture regulation (51.1-52.7%) applied in the seventh fermentation cycle showed that increased moisture in Zaopei was inversely correlated with aldehyde transformation efficiency (88.3-75.5%). This study elucidates the moisture-mediated regulatory mechanism underlying microbial metabolism and aldehyde conversion, offering novel insights for optimizing the fermentation process of SFB.