Key flavor compounds in cheese fermented with infant-qualified probiotics: comparison of single strain and multi strain culture.

Cheese is a probiotic carrier, but how single- and mixed-strain fermentation affects flavor and metabolism remains unclear. Cheeses fermented singly or in combination with Limosilactobacillus reuteri DSM 17938 and Bifidobacterium animalis subsp. lactis strains BB-12 and Bi-07 were evaluated by volatile and non-volatile metabolite profiling, sensory analysis, and gastrointestinal digestion. The numbers of detected aldehydes and esters increased from 20 and 6 in single-strain cheeses to 47 and 12 in mixed-culture cheeses, respectively, while the number of detected acids decreased from 55 to 42. Fruity aroma scores reached 8.2-8.9 in mixed-culture cheeses versus 5.0-6.0 in single-strain cheeses, whereas sulfurous/onion aroma scores decreased to 3.5-5.3 from 6.5 to 7.2. Metabolite profiles revealed strain-dependent peptide- and free-amino-acid enrichment, with lower biogenic amine signals and greater umami potential in selected mixed cultures. In vitro digestibility of the three-strain cheese was comparable to DSM 17938 cheese (82.41%). Targeted co-fermentation improved cheese quality for infant-oriented applications.