Jiuqu supplementation enriches whiskey-relevant volatile metabolites in corn-whiskey mash: volatile metabolomics and microbial ecological associations

Corn-whiskey fermentation relies on monoculture fermentation with Saccharomyces cerevisiae , which helps ensure stable alcoholic fermentation but may limit microbial metabolic diversity and flavor complexity. In contrast, Jiuqu, a saccharifying-fermenting starter used in Chinese Baijiu, harbors diverse microorganisms and contributes to the diverse and abundant flavor compounds characteristic of Baijiu. However, its role in liquid corn-whiskey fermentation remains unclear. Here, we compared a mixed Jiuqu flavor-enhanced fermentation (JQFEF) with a whiskey-specific Saccharomyces cerevisiae fermentation (WSK) in terms of physicochemical characteristics and volatile metabolite profiles, and performed metagenomic analysis of JQFEF to characterize the restructuring and flavor-related metabolic potential of Jiuqu-derived microbiota. A literature-derived set of 33 whiskey hallmark flavor metabolites (WHFMs) was used to evaluate whiskey-representative compounds. Compared with WSK, JQFEF showed stronger substrate conversion, greater acidification, higher volatile accumulation, and broader volatile classes, particularly esters, alcohols, and acids. Fifteen WHFMs were significantly increased in JQFEF, mainly fatty acid esters, lactones, terpenes, phenolics, and higher alcohols. JQFEF metagenomics revealed progressive enrichment of lactic acid bacteria, particularly Lacticaseibacillus and Lactiplantibacillus , while Saccharomyces dominated the fungal community and non- Saccharomyces yeasts maintained stable niches. Functional annotation and association analyses indicated that microorganisms such as Lacticaseibacillus and Saccharomycopsis possessed metabolic potential and showed high network connectivity with WHFMs. Overall, these results characterize microbial community restructuring following Jiuqu supplementation and suggest potential ecological associations between candidate microorganisms and volatile enrichment during corn-whiskey fermentation. These findings provide preliminary information for validation of potential flavor-associated microorganisms and may inform future exploration of their application in multi-strain corn-whiskey fermentation.