Flavor tuning of semi-hard cheese by targeted formation of γ-glutamyl dipeptides

The kokumi sensation of mature Gouda cheese was found to be induced by γ-glutamyl dipeptides, which are formed from glutamine and a second amino acid catalyzed by γ-glutamyl transferase (GGT). With the aim of accelerating kokumi peptide biosynthesis, the GGT activity of raw milk was preserved by applying microfiltration for reduction of microbial count, and glutamine as substrate was incorporated into the curd of semi-hard cheese by extrusion. The resulting samples were analyzed regarding chemical composition, hardness, and melting behavior and were comparable to other cheese products. The concentration of γ-glutamyl dipeptides increased continuously over the 12-week ripening period. The enhancement in kokumi perception corresponding to prolonged ripening times was estimated using a model based on commercial cheese samples with different degrees of maturation. The combination of substrate availability and enzyme activity resulted in γ-glutamyl dipeptide levels equivalent to 8 months of ripening after only 3 months. The improved sensory profile was finally confirmed using sensory studies.