Decoding the aroma characterization and influencing factor in the core brewing process of China’s northern Sauce-Flavored Baijiu

Microecology makes aroma of sauce-flavored baijiu (SFB) obviously different. However, understanding of aroma characteristics of China's northern SFB and influencing factor of aroma difference was still limited, this study compared aroma characteristics of base liquor (BL), environmental temperature, as well as physicochemical parameters, volatile compounds and microbial succession of fermented grains across core rounds (3   R to 6   R). Sensory evaluation revealed 3   R was characterized by grain aroma, 4   R by fermentation aroma, 5   R by alcohol and sour aroma, and 6   R by fruit and floral notes. Using HS-SPME-GC-MS combined with external standard quantitative technology, a total of 204 and 213 volatile compounds were detected from BL and fermented grains, respectively. Through traceability analysis, 29 ester substances (including ethyl acetate, ethyl lactate, hexadecanoic acid ethyl ester) were identified as main metabolic marker responsible for aroma difference. LEfSe and Spearman correlation analysis indicated that 10 differential fungi, such as Pichia , Wickerhamomyce and Millerozyma were principal contributors to variation in ester production. RDA analysis showed that temperature was main driving factor, indicating that ambient temperature in northern regions influenced yeast metabolism in production of ester, imparting a distinct aroma to each round of BL. This study provided a theoretical foundation for northern SFB brewing process control.