Effects of Wheat Composition on the Physicochemical and Volatile Components of Daqu (A Primary Starter for Chinese Baijiu Fermentation)

Wheat serves as the primary raw material for medium- and high-temperature Daqu, a key saccharification, fermentation, and flavoring agent in Chinese Baijiu production. To investigate the influence of wheat’s main components on the quality and volatile profile of Daqu, this study comparatively analyzed the main components of three distinct wheat varieties and the physicochemical indices and volatile characteristics of the Daqu produced from them. Results indicated significant differences (p < 0.05) in the main components of the wheats and in the physicochemical indices and sensory scores of their corresponding Daqu samples. CM605 Daqu exhibited the highest acidity, NM660 Daqu showed the highest saccharification power, and MM907 Daqu had the highest liquefaction power. A total of 66 volatile compounds were identified across the three Daqu types, encompassing esters, alcohols, aldehydes, acids, phenols, ketones, pyrazines, etc. The contents of volatile compounds varied significantly among the Daqu samples made from different wheats; notably, the total contents of esters, alcohols, and aldehydes showed significant differences (p < 0.05). The Spearman correlation analysis revealed highly significant correlations (p < 0.01) between several wheat quality characteristics and Daqu quality indices, identifying wheat starch and protein as key factors affecting Daqu quality. The PLS-DA analysis revealed 34 differential volatile compounds. Mantel test correlation analysis further confirmed that wheat components including starch, albumin, globulin, gliadin, glutenin, and fat could influence the differential volatiles in Daqu. For instance, amylopectin content showed a significant positive correlation with n-pentanol, isovaleric acid, and propyl acetate (p < 0.05). This study provides a solid foundation for a deeper understanding of the relationship between wheat composition and Daqu quality, facilitating the more precise selection of wheat varieties to improve Daqu quality during production.