Characteristics of the microbiota and metabolic profile of high-temperature Daqu with different grades

Microbial Community Affects Daqu Quality and the Production of Ethanol and Flavor Compounds in Baijiu Fermentation

“…There is an increasing demand for modern Daqu-making workshops equipped with air-conditioning systems which can control the temperature, humidity, and even CO 2 and O 2 concentrations accurately throughout the workshop and thus minimize the effects of undulating climate factors on the quality of Daqu. The previous studies on the microbial community in Daqu [29,32], and this present study comparing the microbial communities between QD and ID, will certainly be helpful for the development of synthetic microbial consortia as the inoculating source of functional microbes for Daqu fermentation in accurately airconditioned workshops. We believe that the quality of Daqu can be accurately controlled using updated technology.…”

“…The quality of Daqu produced in different workshops and in different seasons usually varies because Daqu is manually manufactured by spontaneous fermentation in an open environment, and the factors such as temperature and air moisture which affect microbial growth on and in Daqu bricks cannot be accurately controlled. The quality of Daqu is usually assessed based on subjective sensory parameters supplemented with starch saccharification and fermentation ability tests [29,32]. We show here that the quality of Daqu is determined by its microbial community, which in turn affects the microbial community in Baijiu fermentation and the yield and quality of the end product.…”

“…Zhang et al (2022) demonstrated that superior-and normal-grade sauce-flavor Daqu had distinct flavors. In addition, fungal counts were higher in normalgrade Daqu than superior-grade Daqu, while bacterial community richness was higher in superior-grade Daqu than in normal-grade Daqu [32]. However, there have been few comparative studies of the microbial community and physicochemical properties of QD and ID and the effects of different quality levels of Daqu on the end products of fermentation.…”

“…Due to the complicated process and multiple factors involved in Daqu production, different grades of Daqu may be obtained. The quality of Daqu is traditionally evaluated based on subjective sensory properties and physicochemical characteristics [29][30][31][32]. A qualified Daqu break usually emits strong and pure 'Qu-fragrance', is evenly covered by white spots on over 70% of the surface, and has a relatively thin skin-like structure and a homogenic cross section without obviously visible cracks and mold spots.…”

“…Researchers compared the bacterial communities of different grades of roasted-sesame-like flavored Daqu, but did not reveal the link between flavor compounds and the bacterial communities [29]. Zhang et al (2022) demonstrated that superior-and normal-grade sauce-flavor Daqu had distinct flavors. In addition, fungal counts were higher in normalgrade Daqu than superior-grade Daqu, while bacterial community richness was higher in superior-grade Daqu than in normal-grade Daqu [32].…”