Combining Untargeted Metabolomics and High-Throughput Sequencing to Explore the Dynamics of Small-Molecular Metabolites in the Fermentation Stage of Inner Mongolian Cheese

The purpose of this work was to investigate the metabolite changes, taste compounds, and microbial composition throughout the fermentation process of Inner Mongolian cheese, comprising a total of 106 differential metabolites, including 71 kinds of lipids and lipid-like molecules, 9 kinds of organoheterocyclic compounds, and so on. Determination of free amino acids (FAAs) showed that the contents of FAAs with delightful tastes (i.e., Glu, Pro, Asp) are significantly increased during fermentation stages. Five possible key metabolic pathways were identified based on the KEGG database. High-throughput sequencing results indicated that Lactococcus and Geotrichum were the predominant microorganisms during fermentation, which were significantly correlated to differential metabolites and FAAs. Our work provided a theoretical basis for the production of functional ingredients and flavor substances in cheese and the development of adjunct starters.