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.

Untargeted metabolomics based on ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS) was adopted to study three types of Boza, made from different raw materials. Multivariate statistical techniques such as principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were used to screening for differential metabolites, and pathway enrichment analysis of differential metabolites was carried out. The results showed that there were significant differences in metabolites among the three types of Boza. Altogether, 109, 124 and 114 differential metabolites were identified in intangible cultural heritage (G1) vs traditional Talmi Boza (G2), G1 vs traditional corn Boza (G3), and G3 vs G2, respectively. These differential metabolites mainly included lipids and lipidlike molecules, organic acids and their derivatives, organic heterocyclic compounds, phenylpropanoids, and polyketones. The difference might be caused by the difference in raw materials. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway enrichment analysis, these differential metabolites mainly participated in the biosynthesis of various secondary metabolites in plants, the biosynthesis of phenylpropanoids, the biosynthesis and degradation of flavonoids, and other metabolic pathways. This study provides a theoretical basis for the comprehensive development and utilization of Boza.

The bacterial diversity and metabolomic characteristics of yogurt from three different producers in Bole, Xinjiang were analyzed by using Illumina sequencing and untargeted metabolomics, and the relationship between them was explored. Bacterial diversity analysis showed that the major bacterial genera in the yogurt samples were Lactobacillus, Klebsiella, Lactococcus, and Acetobacter. Using linear discriminant analysis effect size (LEfSe) and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt), Lactobacillus, Klebsiella, and Lactococcus were identified as biomarkers, and their functions were predicted. The metabolomic analysis identified a total of 397 metabolites in the positive ion mode and 324 metabolites in the negative ion mode, with lipids and lipid-like substances, organic acids and their derivatives, and organic heterocyclic compounds being the predominant ones. Notably, lipids and lipid-like substances, organic acids and their derivatives were the major differential metabolites, contributing to the flavor of yogurt. The metabolic pathway analysis revealed amino acid metabolism and secondary metabolism to be the main enriched pathways, which aligned partially with the functional prediction results. Integrated microbiomic and metabolomic analyses showed that the genera Lactobacillus, Limosilactobacillus, Lactococcus, and Klebsiella were significantly correlated with some metabolites such as organic acids and their derivatives, as well as lipids and lipid-like substances, indicating that the microbial community affected the nutrients of yogurt through its metabolic activities. This study provides a scientific theoretical basis for the production and quality improvement of Xinjiang yogurt.