Reaction Mixtures Rich in [γ-Glu]_{(<i>n</i>≥1)}-Arg Derived from Enzymatic Synthesis as Potential Salt and Umami Enhancers

Some arginyl dipeptides and γ-glutamyl peptides have been identified as salt and umami enhancers. These compounds provide an operable approach for reducing sodium uptake without losing the palatability of foods. γ-Glu-Arg was hinted to have a taste-enhancing effect in the past, but few research studies have focused on it. In the present study, a series of γ-glutamyl peptides containing Arg such as γ-Glu-Arg, [γ-Glu](n=2)-Arg, [γ-Glu](n=3)-Arg, [γ-Glu](n=4)-Arg, [γ-Glu](n=5)-Arg, [γ-Glu](n=6)-Arg, [γ-Glu](n=7)-Arg, and [γ-Glu](n=8)-Arg were synthesized using glutaminase from Bacillus amyloliquefaciens in the presence of Gln and Arg. A high solid concentration of 30% was found to increase the production of [γ-Glu](1≤n≤4)-Arg. Sensory evaluation revealed that individual [γ-Glu](n=1,2,3,4)-Arg has a slightly bitter and astringent taste. [γ-Glu](n=1,2)-Arg (1.0 mg/mL) significantly increased the umaminess in the mixture of salt and sodium glutamate but showed no significant effect on saltiness in the salt solution, whereas [γ-Glu](n=3,4)-Arg and postenzymatic reaction mixtures (1.0 mg/mL) significantly increased both saltiness and umaminess. [γ-Glu](n=3,4)-Arg and postenzymatic mixtures in the system with 30% solid concentrations showed a high and similar taste-enhancing effect. Moreover, umaminess and saltiness increased 1.9 and 2.4 times in the simulated broth, respectively, while saltiness increased 1.5 times in the salt solution by the addition of postenzymatic reaction mixtures in the system with 30% solid concentrations at 20.0 mg/mL. These results indicated that [γ-Glu](n=1,2,3,4)-Arg and postenzymatic reaction mixtures rich in [γ-Glu](n≥1)-Arg were potential salt or umami enhancers.