The role of Lacticaseibacillus paracasei K7 in regulating proteolysis, aroma formation and the peptidome profile of semi-hard cheese.

This study evaluated the effectiveness of a novel strain of L. paracasei K7 as an adjunct starter culture to accelerate ripening and improve the quality of semi-hard cheese. Control cheeses produced with a traditional starter culture and experimental cheeses additionally inoculated with L. paracasei K7 underwent comprehensive multiparametric evaluation during ripening and cold storage. The addition of L. paracasei K7 did not inhibit starter culture development and promoted faster colonization of the cheese matrix by day 10 of ripening. Biochemical markers of proteolysis and 2D-PAGE analysis showed that by day 45, the cheese with L. paracasei K7 had reached a level of proteolysis comparable to that of the control sample after 60 days of ripening. The volatile compound profile of the experimental cheese shifted toward acetic acid predominance, whereas propionic acid was detected in the control cheese. Diacetyl, which imparts characteristic creamy notes, was detected exclusively in the sample with L.paracasei K7 and accounted for 31.9% of total ketones. The cheese made with L. paracasei K7 and ripened for 45 days received the highest overall sensory score (43.3 points), surpassing the control sample ripened for 60 days (40.7 points). Peptide analysis confirmed the preservation of bioactive peptide diversity while reducing the proportion of bitter sequences in the cheese containing L. paracasei K7. Taken together, these results confirm that the novel strain L. paracasei K7 is a promising adjunct starter culture capable of accelerating semi-hard cheese ripening, improving flavor and aroma development, enhancing microstructural stability, and promoting the accumulation of functionally significant peptides without compromising product quality.