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