Proposal of a Novel Standard for Determining the Aging Period of High-Temperature Daqu Based on the Species-Level Bacterial Composition Through PacBio Sequencing

Aging is an indispensable step to obtain high-quality Moutai-flavor Daqu. However, the criteria for determining the storage period were as yet limited. The current study aimed to judge the storage period based on bacterial composition of Daqu at the species level through PacBio Single molecular real-time sequencing. The results indicated that the diversities of Daqu (Y1-Y3) with 3-5 months were higher than that of Daqu (Y4-Y5) with >= 6 months. Kroppenstedtia was the predominant genus and was ubiquitous in all Daqu samples while Enterobacter mainly existed in Y1-Y3. Importantly, species K. sanguinis and Lentibacillus massiliensis mainly inhibited Y4 (6 months) without opportunistic pathogens E. cloacae and Staphylococcus gallinarum. Accordingly, 6 months are possibly appropriate time for aging period. This investigation for the first time adopted functional bacteria and pathogens as a bioindicator and thus provided a novel criteria determining the ripening period from the food quality and safety perspective.