Molecular Mechanism and Sensory Characterization of “Kokumi” Substances

Abstract

Humans can sense five basic tastes, sweet, bitter, sour, salty, and umami. Receptors for each basic taste quality are thought to be expressed in separate populations of taste bud cells. Humans also possess orosensory mechanisms to detect compounds that do not elicit any basic tastes. Some foods are known to have taste sensation that cannot be explained by the five basic tastes alone, such as continuity, mouthfulness and thickness. It was demonstrated that these sensations are evoked by the addition of kokumi substances, flavor modifiers that have no taste themselves. We recently demonstrated that the orally administered agonists/modulators of calcium-sensing receptor (CaSR) affect these orosensory perception that cannot be explained by the five basic tastes. For instance, in human sensory studies, CaSR activators, Ca²⁺ and γ-glutamyl peptides enhance the intensities of umami, sweet, and salty tastes in a CaSR-dependent manner. Furthermore, we found the positive correlation between CaSR activity and taste enhancing effect of kokumi substances. We conclude that calcium-sensing receptor (CaSR) is involved in kokumi substances perception. In this review, we also show that CaSR activating peptide, γ-Glu-Val-Gly is the potent kokumi substance and would be useful for improving the flavor of foods.