Unlocking the Feng-flavor baijiu code: Single-strain yeast inoculants outperform co-cultures in enhancing sweet honey-ester aroma.

Abstract

The addition of exogenous functional microbial strains during Feng-flavor Baijiu fermentation influences the organoleptic profile of Baijiu, but its regulatory mechanisms remain unclear. In this study, three yeast species, Wickerhamomyces anomalus (W. anomalus, T1 group), Saccharomyces cerevisiae (S. cerevisiae, T2 group), and Geotrichum candidum (G. candidum, T3 group), isolated from Feng-flavor Daqu were inoculated into the solid-state fermentation system of Feng-flavor Baijiu to explore their enrichment impacts on the physicochemical properties of fermented grains, microbial community structure, and the modulation of base Baijiu flavor profiles. The results demonstrated that inoculation with G. candidum promoted ethanol accumulation (from 40.3% (v/v) to 43.4% (v/v)) and enhanced the utilization of reducing sugars (from 1.65% (w/w) to 1.35% (w/w)), whereas opposite trends were observed with W. anomalus and S. cerevisiae. All inoculated groups exhibited a significant enhancement in the content of ester aroma compounds (ethyl acetate from 1412.16 mg/L to 3379.46 mg/L in T1 and ethyl hexanoate from 176.83 mg/L to 273.25 mg/L in T2) along with sweet honey-like aroma compounds (phenethyl acetate from 0.47 mg/L to 1.97 mg/L in T1, 2-phenylethanol from 17.33 mg/L to 42.50 mg/L in T2, and ethyl 3-phenylpropanoate from 6.53 mg/L to 13.47 mg/L in T3) in the base Baijiu (p < 0.05). Notably, single-strain inoculations exerted stronger modulation effects than mixed-culture fermentation. Analysis of microbial community diversity revealed that targeted yeast fortification significantly modulated the community compositions of bacteria and fungi; many genera within these communities indicated a positive correlation with the content of ethyl acetate and phenethyl acetate (|r| > 0.6, p < 0.05). These shifts are likely driven by altered microbial interactions, such as the competitive exclusion of