Isolation and Characterization of Lactic Acid Bacteria from Traditional Xinjiang Fermented Foods and Untargeted Metabolomic Analysis of Xinjiang Cheese Fermented with Them

This study isolated 13 strains of lactic acid bacteria (LAB) from Xinjiang local fermented foods and evaluated their curdling properties and antioxidant activity. Strains with superior curdling properties and antioxidant activity were selected for Xinjiang cheese production using different processing techniques, followed by untargeted metabolomic analysis. We identified five Lactiplantibacillus plantarum strains, three Pediococcus pentosaceus strains, two Limosilactobacillus fermentum strains, two Lactococcus lactis strains, and one Streptococcus thermophilus strain. All strains exhibited acid and bile salt tolerance. Based on curdling characteristics, sensory scores, and antioxidant activity, four superior strains—JY4, NC1, HM4, and HM6—were selected for cheese production using different processing methods. Untargeted metabolomic analysis of cheese samples showed that carbohydrates and their conjugates, amino acids, peptides and their analogs, and fatty acids and their conjugates were the major categories of differential metabolites. The differential metabolic pathways were primarily concentrated in the biosynthesis of secondary metabolites, lipid metabolism, amino acid metabolism, and carbohydrate metabolism. Plain Xinjiang cheese (YW), Xinjiang cheese supplemented with goji berry powder after fermentation (TJ), and Xinjiang cheese supplemented with goji berry powder before fermentation (HH) exhibited better flavor and nutritional value compared with commercial plain Xinjiang cheese (SY). Specifically, YW exhibited the best flavor quality, TJ showed more pronounced probiotic properties due to the addition of goji berries, while HH showed the best comprehensive performance in nutritional value and probiotic functionality. This study helps to enrich microbial resources and deepen the understanding of metabolites in Xinjiang cheese.