Predominant odorants in modern and traditional types of Chinese xiaoqu liquor (Baijiu) were identified and compared by the combined use of gas chromatography−olfactometry, odor activity values (OAVs), and multivariate analyses. A total of 79 aroma compounds were identified in a typical modern type xiaoqu Baijiu (M) and a typical traditional type xiaoqu Baijiu (T), 42 of them had OAV > 1 in both M and T samples. The main differences between the two samples were obtained for the concentration of 23 aroma-active compounds. A total of 22 samples made by different brewing processes were analyzed to confirm the differences. Partial least squares discriminant analysis confirmed that 20 compounds could be used as potential markers for discrimination between modern type xiaoqu Baijiu and traditional type xiaoqu Baijiu. Their difference in content is between 1.5 and 17.9 times for modern type xiaoqu Baijiu and traditional type xiaoqu Baijiu. The results showed the aroma characteristics of modern and traditional type xiaoqu Baijiu clearly and comprehensively, which will provide guidance for modern Baijiu quality control and evaluation.

Ethyl acetate, a characteristic flavor compound in light-flavor Baijiu (LFB), plays a pivotal role in defining its sensory profile. Insufficient concentrations in fermented grains may diminish the quality of Baijiu. Indigenous microbial bioaugmentation has proven effective in improving Baijiu quality by reshaping microbial community and modulating flavor metabolism within fermentation ecosystems. This study investigated the effects of Jiuqu fortified with an indigenous Saccharomycopsis fibuligera Y162 on the microbial community, physicochemical parameters, and volatile compound profiles throughout the fermentation of LFB. Results demonstrated a significant increase in ethyl acetate content in both original Baijiu and fermented grains, alongside pronounced fungal community restructuring. PacBio single-molecule real-time (SMRT) sequencing analysis showed that Lactobacillus helveticus, Rhizopus sp., Saccharomyces cerevisiae, and Issatchenkia orientalis became the dominant species at the end of fermentation. Correlation network analysis revealed that ethyl acetate was significantly related (P < 0.05, |ρ| > 0.7) to the I. orientalis and Rhizopus sp. (the main fungal biomarkers), which was driven by the functional S. fibuligera. Mantel test further highlighted acidity, temperature, and moisture as critical environmental factors influencing the microbial community (P < 0.05, |ρ| > 0.7). To summarize, biofortification with S. fibuligera exhibited positive effects in enhancing typical flavor metabolites by influencing fungal community structure in LFB. These findings imply that the indigenous strains have great application potential in improving the quality of Baijiu.