Analysis of the differences in physicochemical indexes and flavor characteristics between sauce-flavor Daqu and Muqu

As a seed starter in the fermentation process of high-temperature Daqu, the Muqu is innoculated during the Daqu fermentation process. Its microbial community, volatile flavor components and enzyme system will directly affect the finished Daqu quality and Daqu batch stability. In this study, using Muqu and Daqu as the research objects, the physicochemical indexes and volatile flavor compounds were analyzed, and the quality differences between the two samples were explored combined with multivariate statistics. The results showed that the moisture and saccharification power of Muqu were significantly lower than the Daqu (P＜0.05), and the acidity and melanoids were significantly higher than Daqu (P＜0.05). The volatile flavor compounds in the two types of Daqu were detected by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). A model was constructed using orthogonal partial least squares-discriminant analysis (OPLS-DA). Based on the variable projection importance (VIP) values and the P-values of variance analysis, 13 key different volatile flavor compounds (VIP≥1, P＜0.05) were selected. The results of the significance analysis indicated that the 2-furanfuranol and 3-methyl butyraldehyde in the Muqu were significantly higher than those in the Daqu (P＜0.05). The redundancy analysis (RDA) showed that the Muqu had a strong correlation with 2-furfurfurfurol, 3-methylbutyraldehyde, acidity and melanoids. This research provided a theoretical basis for establishing the screening standards of Muqu of sauce-flavor Daqu and offered new ideas for improving the quality of high-temperature Daqu and achieving standardized production.