Differences in Functional Characteristics and Microbial Community Structures of Three Types of High-Temperature Daqu

This study investigated the differences in the physicochemical indexes, volatile flavor substances and microbial community composition of three different colored Daqu (black, yellow and white). Physicochemical analyses showed that the acidity, moisture content and saccharifying power of black Daqu were intermediate between those of yellow and white Daqu, white Daqu had the highest saccharifying power, fermenting power, and esterifying power, and yellow Daqu contained the highest starch content. Flavor substance analysis indicated significant differences in the contents of ethyl caproate, ethyl acetate, phenylethyl alcohol, 1-hexanol and furfural among the three types of Daqu. Microbial community structure analysis revealed that Bacillus and Scopulibacillus were the dominant bacteria, and Thermomyces and Thermoascus were the major fungi in all three types of Daqu. Redundancy analysis (RDA) suggested that Bacillus and Thermomyces had a positive correlation with fermenting power, esterifying power and saccharifying power. Spearman correlation analysis showed that Scopulibacillus, Virgibacillus and Aspergillus were positively correlated with most key flavor compounds. This study provides reference data for the rational application of Daqu in the production of Jiang-flavor Baijiu and is of great value for the standardization of Jiang-flavor Baijiu production.