Analysis of Physicochemical Indices, Volatile Flavor Components, and Microbial Community of a Light-Flavor Daqu

Daqu contains the raw materials, microorganisms, and enzymes needed for Baijiu making, and also provides the flavors and flavor precursors found in Baijiu. Herein, we describe our systematic study into the physicochemical indices, volatile flavor compounds, and microbial community structures of light-flavor Daqu. The results indicated that this Daqu exhibited unique characteristics. The solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) results showed that the Daqu contained 46 volatile components, such as esters, alcohols, alkenes, sulfur compounds, ketones, furans, aldehydes, nitrogen-containing compounds, and alkanes, and the main volatiles were esters, alcohols, aldehydes, and alkanes. Moreover, ethyl butyrate, nonyl aldehyde, n-hexanol, 1-(2-ethylhexyl) nitrohexane, 2,3,5,6-tetramethylpyrazine, n-octanol, 1-octen-3-ol, and phenylethanol were present in relatively high abundance. In terms of the microbial flora structure, Kroppenstedtia, Oceanobacillus, Lactobacillus, Paucisalibacillus, Bacillus, and Lentibacillus were the main genera of prokaryotic microorganisms. The eukaryotic microbes were primarily Aspergillus, Pichia, and Saccharomycopsis. This article has systematically studied the physicochemical indices, flavor compounds, and microbial community structures of Daqu. These results enrich our knowledge of Daqu and can be used to promote the development of traditional fermentation technology.