Process Regulation of Microbial-Driven Aldehyde Metabolism in Sauce-Flavor Baijiu Fermentation

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 <i>Fusarium</i> and <i>Apiotrichum scarabaeorum</i> 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 <i>Paenibacillus</i>, 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.