Exploring the Relationship Between GuaYi Levels and Microbial-Metabolic Dynamics in Daqu

Daqu is a crucial saccharifying and fermenting agent in the production of Baijiu, with GuaYi referring to the white fungal colonies on Daqu's surface, serving as a critical indicator for sensory evaluation. However, the correlation between distinct GuaYi and the consequent internal modifications in Daqu remains to be elucidated. Our investigation delineates that Heavy GuaYi Daqu (HGY), distinguished by an elevated prevalence of white microflora (notably Saccharomycopsis), sustains enhanced moisture levels internally. This environment is conducive to the proliferation of Aspergillus and Kroppenstedtia, resulting in significant increases of 50.95% and 40.75% in the concentrations of alcohols and pyrazines, respectively. Conversely, Light GuaYi Daqu (LGY) creates a comparatively arid environment, favoring Thermoascus and Staphylococcus growth, which is instrumental in the decomposition of complex biomolecules such as starch, reducing sugars, and proteins. These insights elucidate the nuanced interplay between GuaYi and Daqu's quality and stylistic attributes, providing an invaluable theoretical framework for the refinement of sensory evaluation standards for Daqu.