Comparison of changes in fermented milk quality due to differences in the proteolytic system between Lactobacillus helveticus R0052 and Lactococcus lactis subsp.lactis JCM5805

As the healthy diet concept has gained broad acceptance,more and more consumers nowadays prefer to drink fermented milk.Indeed,the quality of fermented milk is influenced by the protein hydrolysis capacity of the bacterial strains used.In this study,we conducted an in silico analysis of the composition of the proteolytic system in the genomes of Lactobacillus helveticus R0052 and Lactococcus lactis subsp.lactis JCM5805,and assessed the impact of these two strains on the quality of fermented milk from several perspectives.The results showed that L.helveticus R0052 and L.lactis JCM5805 had different cell envelope proteases,oligopeptides ABC transport system,and peptidases in their protein hydrolysis systems,which resulted in significant differences in protein hydrolysis,pH,acidity,viable bacteria count,water holding capacity and texture of the produced fermented milk.Differences in the metabolic profiles and pathways of volatile and non-volatile flavor substances between L.helveticus R0052 and L.lactis JCM5805 were identified by metabolomics.L.helveticus R0052 improves the sensory quality of fermented milk compared to L.lactis JCM5805.Our study findings provide novel insights into selecting suitable strains to produce fermented milk from a genetic and metabolic perspective.