Human Bifidobacterium strains as adjunct cultures in Spanish sheep milk cheese

Three bifidobacteria strains of human origin (Bifidobacterium pseudolongum INIA P2, Bifidobacterium breve INIA P734, and Bifidobacterium longum INIA P678) were used as potential probiotic adjunct cultures for the manufacture of pasteurized sheep milk cheese. Bifidobacteria were inoculated at 5 to 6 log cfu/mL in milk vats. Microbiological, physicochemical, rheological, color, and sensory characteristics were determined at 7, 28, and 60 d of ripening. Counts of B. pseudolongum INIA P2 remained above 6 log cfu/g during 60 d of ripening as well as after further simulated gastrointestinal digestion of cheeses. Bifidobacterium breve INIA P734 counts remained stable during 28 d and decreased by less than 1 log unit after simulated digestion. Bifidobacterium longum INIA P678 counts dropped sharply during cheese manufacture and ripening and were below detection level after simulated digestion. Addition of bifidobacteria strains did not affect starter viability, cheese pH, dry matter, water activity, or salt content but significantly increased overall proteolysis and the concentration of some free amino acids. Cheeses with bifidobacteria exhibited no significant differences in most sensory characteristics with respect to control cheese. According to our results, B. breve INIA P734 and B. pseudolongum INIA P2 are promising candidates as probiotic adjunct cultures in fresh and semi-hard sheep milk cheese.