Chinese liquor is one of the 6 well-known distilled spirits in the world. High-temperature Daqu acts as an important source of nutrients and of microorganisms in the solid-state fermentation of Chinese Moutai-flavor liquor, which has a critical impact on the final flavor of the liquor. The study identifies a novel DGGE marker and provides an efficient way to identify bacterial diversity in Daqu from different fermentation stages. Importantly, the study defines dynamic changes of the physicochemical parameters and the infrared spectra analysis of Daqu during the fermentation process. These studies will help to (1) establish a standard operation procedure for Daqu production; (2) stabilize manufacturing process for Daqu fermentation and even for liquor brewing.

Yellow Daqu, black Daqu and white Daqu are three common types of high-temperature Daqu, which are formed due to the difference of Daqu Culture microenvironment. However, the judgment of these types still depends on sensory evaluation, and no objective evaluation depends on data. In this study, three types of Daqu were differentiated based on melanoidin content and mid-infrared spectrum analysis for the first time. Mid-infrared spectroscopy technology was utilized for the rapid identification of different types of Daqu based on various functional group information and fingerprint characteristics. Furthermore, near-infrared spectroscopy technology provides us an effective and efficient quantitative approach of melanoidins. In addition, the difference in microbial community structure and metabolites including volatiles and non-volatiles were further analyzed through multivariate statistical analysis. Microbial functional potential prediction using PICRUSt2 shows that bacteria plays an important role in white and yellow Daqu, while fungi were main contributors in black and yellow Daqu in major metabolic pathway. Bacillales, Lactobacillales, Pseudonocardiales and Eurotiales, and Wallemiales were also selected as biomarker microbes in order’s level.