The Quality Characteristics of Black Soybean Compound Fermented Milk Using Lactiplantibacillus plantarum IMAU40001: A Physicochemical and Metabolomics Analysis

This study investigated the effects of co-fermentation with Lactiplantibacillus plantarum IMAU40001 and the commercial starter PYS-010 on the properties of black soybean compound fermented milk (BSCFM). Specifically, the fermentation characteristics, viable bacterial counts, texture, sensory attributes, and metabolomic profiles of BSCFM were evaluated following co-fermentation. Notably, co-fermentation enhanced water-holding capacity and textural properties, while maintaining high probiotic viability (>106 CFU/mL). Sensory evaluation indicated that co-fermentation improved the overall balance of texture in BSCFM. Non-targeted metabolomic analysis revealed an increased abundance of bioactive metabolites, including flavonoids and amino acids. KEGG pathway analysis indicated the enhanced metabolism of amino acids, lipids, and plant secondary metabolites. These results suggest that black soybean serves as a rich source of functional precursors that, upon co-fermentation, facilitate the biosynthesis of health-promoting compounds. Overall, co-fermentation with IMAU40001 and PYS-010 improves the structural, sensory, and functional properties of BSCFM, offering a promising strategy for the development of functional fermented dairy products.