Changes in Microbial Communities and Volatile Compounds during the Seventh Round of Sauce-Flavor baijiu Fermentation in Beijing Region

Abstract

Sauce-flavor baijiu products produced in different regions have perceptible differences in flavor characteristics, but the reasons for the formation of regional flavor substances are still unclear. The brewing process of sauce-flavor baijiu includes multiple rounds of pit fermentation. The base baijiu produced at the end of pit fermentation contributes significantly to the flavor of sauce-flavor baijiu products. This study investigated the microbial community succession and changes in flavor compounds during 7th round pit fermentation of sauce-flavor baijiu produced in Beijing region and comparatively analyzed the componential differences in microbial community and flavor compounds with sauce-flavor baijiu produced in other regions. It was found that Lactobacillus, Virgibacillus, Thauera, and Kroppenstedtia were the dominant bacterial genera, and Byssochlamys, Cutaneotrichosporon, and Apiotrichum were the dominant fungal genera. A total of 47 volatile compounds were identified and quantified in fermented grains. The concentrations of ethyl L(-)-lactate, ethyl caproate, and diethyl succinate gradually decreased with time, while the concentrations of phenethyl acetate, ethyl palmitate, and ethyl phenylacetate increased. The relative abundance of dominant microorganisms as well as the concentrations of volatile compounds showed a successional pattern with fermentation time. Lactobacillus, Virgibacillus, and Kroppenstedtia were positively associated with the synthesis of ethyl phenylacetate and phenylethyl alcohol, while negatively associated with the synthesis of ethyl caproate. Differences in microbial community structure are partly responsible for the regional flavor characteristics of sauce-flavor baijiu and the flavor differences between rounds of base baijiu. This study will provide in-depth insights into the formation of regional flavor compounds of sauce-flavor baijiu.