Kokumi taste substances exemplified by γ-glutamyl peptides and Maillard Peptides modulate salt and umami tastes. However, the underlying mechanism for their action has not been delineated. Here, we investigated the effects of a kokumi taste active and inactive peptide fraction (500-10,000 Da) isolated from mature (FIIm) and immature (FIIim) Ganjang, a typical Korean soy sauce, on salt and umami taste responses in humans and rodents. Only FIIm (0.1-1.0%) produced a biphasic effect in rat chorda tympani (CT) taste nerve responses to lingual stimulation with 100 mM NaCl + 5 μM benzamil, a specific epithelial Na+ channel blocker. Both elevated temperature (42 °C) and FIIm produced synergistic effects on the NaCl + benzamil CT response. At 0.5% FIIm produced the maximum increase in rat CT response to NaCl + benzamil, and enhanced salt taste intensity in human subjects. At 2.5% FIIm enhanced rat CT response to glutamate that was equivalent to the enhancement observed with 1 mM IMP. In human subjects, 0.3% FIIm produced enhancement of umami taste. These results suggest that FIIm modulates amiloride-insensitive salt taste and umami taste at different concentration ranges in rats and humans.
Keywords: Korean soy sauce; amiloride-insensitive salt taste pathway; chorda tympani; kokumi; salty; umami.