Fermented milk by Lactobacillus delbrueckii, Lacticaseibacillus paracasei, and Kluyveromyces marxianus shows special physicochemical and aroma formation during the storage

In this study, the microbial interactions among co-culture of Lactobacillus delbrueckii DPUL-F36, Lacticaseibacillus paracasei DPUL-F115, and Kluyveromyces marxianus 39 in fermented milk were evaluated during 13 days of refrigerated storage (4 ± 0.5 °C), in terms of titratable acidity, viable cell counts and metabolites. The fermented milk involving K.marxianus 39 showed a maximum lactobacilli count (4.8 × 10 9  CFU/mL) and titratable acidity (151.0 ± 1.7 °T). K. marxianus 39 could enrich the flavor of the fermented milk and improve the sensory quality of the fermented milk on the 5th and 9th day of storage. The contents of aspartic acid, glycine, alanine, valine, methionine, leucine, lysine, and tyrosine increased significantly, while the contents of valine, methionine, leucine, phenylalanine, and lysine in milk fermented by Lactobacillus delbrueckii DPUL-F36, Lacticaseibacillus paracasei DPUL-F115, and Kluyveromyces marxianus 39 were significantly lower than those in milk fermented by Lactobacillus delbrueckii DPUL-F36, Lacticaseibacillus paracasei DPUL-F115 during storage. The higher concentrations of acetic acid, nonanoic acid, acetoin, 2-nonanone, and 2-undecanol were observed in the fermented milk involved with K. marxianus 39. Our results showed K. marxianus 39 has the potential to be a starter culture for fermented dairy products.