Effects of Different Contents of Sorghum Tannin on Fermentation Process and Flavor of Sichuan Xiaoqu Baijiu

To elucidate the effects of sorghum tannin content on the fermentation process and flavor profile of Sichuan Xiaoqu Baijiu, Australian sorghum (tannin content 0.2%) was used as the raw material, with natural sorghum tannin concentrations of 0%, 0.5%, 1.0%, 1.5%, and 2.0% added prior to saccharification. The physicochemical parameters and volatile flavor compounds of fermented grains were systematically analyzed throughout the fermentation stages using techniques such as HS-SPME-GC-MS and electronic nose. Post-fermentation, the aromatic components and sensory profiles of different Baijiu samples were systematically analyzed through HS-SPME-GC-MS and GC×GC-TOFMS techniques. Results indicated that ester compound formation in fermented grains accelerated during the late fermentation stage (6~10 days), showing an initial increase with the tannin content followed by a subsequent decline. Quantitative descriptive analysis (QDA) through HS-SPME-GC-MS and GC×GC-TOFMS identified n-propanol, isobutanol, ethyl acetate, acetal, and isoamyl alcohol as the five key compounds most significantly influencing the aromatic differentiation among the five groups of Baijiu samples. Compared with the control group, the concentrations of pungent compounds including aldehydes (e.g., acetal, furfural) and higher alcohols (e.g., isobutanol, isoamyl alcohol) in Baijiu samples supplemented with 1.0% (w/w) tannin showed significant reduction (P<0.05), with concomitant decreased in harsh flavor notes (P<0.05). The concentrations of ethyl acetate, ethyl caprylate, and ethyl lactate were significantly elevated (P<0.05), concomitant with a marked enhancement in the floral and sweet characteristics of the Baijiu samples (P<0.05). This study provides data support and theoretical basis for the study of the influence of sorghum tannin content on Baijiu brewing, and provides reference for the breeding of wine making raw materials.