Cross-over fermentation dynamics and proteomic properties of acid gels with indigenous Lactobacillus spp. isolated from cheeses

The present study examined the proteomic characteristics and fermentation dynamics of indigenous bacteria isolated from traditional Mihalic cheese in an acid gel matrix. Accordingly, autochthonous strains of Levilactobacillus brevis, Lacticaseibacillus paracasei, and Lacticaseibacillus rhamnosus were adapted to the gel matrix alongside commercial yogurt culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus). The study evaluated bacterial activity, proteolytic behavior, physicochemical characteristics, and textural and sensory properties in acid gel samples. The microorganisms demonstrated high survival rates (>7.35 log₁₀ cfu/g) in the fermented gel system and induced limited acidification throughout the product's shelf life. Regarding proteomic properties, the highest amino acid variation during the shelf life was observed in the FMB sample (28.20%). Furthermore, arginine, leucine, phenylalanine, aspartic acid, lysine, and cysteine reductions were noted in samples containing the isolated microorganisms. Including indigenous microorganisms in the fermented milk increased the levels of essential amino acids. Principal Component Analysis of sensory properties revealed that samples containing indigenous microorganisms differed significantly from the control sample (C), which contained only commercial yogurt culture. The results revealed the proteolytic changes associated with fermentation, including producing free amino acids as nutritional components, forming specific aroma compounds, and modifying textural and sensory properties. These results demonstrate the potential of utilizing local cultures to develop products enriched with novel bioactive components, offering consumers enhanced nutritional and sensory benefits.