Multi-method joint analysis reveals differences in the quality and microbial composition of high-temperature and medium–high-temperature Daqu

Abstract

Daqu plays a key role in the fermentation of Baijiu and affects its quality. In this study, Daqu was sourced from a winery in Yingtan City, and the microbial profiles and quality of different Daqu samples were examined using ultra-high-deep metagenomic sequencing and bionic technology, respectively. The starch content of high-temperature Daqu was determined to be 35.65%, which was significantly lower than that of medium–high-temperature Daqu ( P < 0.05). In contrast, the acidity, amino nitrogen content, and protein content of high-temperature Daqu were significantly higher than those of medium–high-temperature Daqu ( P < 0.05). The fermentation analysis revealed that the alcohol-producing, liquefying, and saccharifying power of high-temperature Daqu were 4.41 U, 2.22 U, and 280.35 U, respectively. These values were all significantly lower than those of medium–high-temperature Daqu ( P < 0.05). High-temperature Daqu displayed a higher aroma intensity but weaker bitterness and astringency ( P < 0.05). Thus, there were certain differences in sensory quality and fermentation performance between the two types of Daqu. Staphylococcus gallinarum and Kroppenstedtia sp. were mainly found in high-temperature Daqu, while Saccharopolyspora rectivirgula and Saccharopolyspora sp. were found in medium–high-temperature Daqu. Functional analyses revealed that high-temperature Daqu had a higher content of carbohydrate esterases , while medium–high-temperature Daqu had higher auxiliary activity ( P < 0.05). The results showed that the temperature-induced differences in the microbial structure of Daqu could affect its sensory quality and fermentation performance. This study provides necessary data support for the screening of wine-making microbes and improvement of Daqu fermentation quality.