Identification of a key umami-active fraction in modernized Korean soy sauce and the impact thereof on bitter-masking

•F05, containing materials of molecular weight less than 500 Da, plays a crucial role in imparting an umami taste to mJGN.•Glu, Ala, Leu, Ser, and Val are the dominant free amino acids, and Glu the dominant bound amino acid, in F05.•F05 bitter-masked the human responses to l-Ile, Gly-Leu, and caffeine.•F05 suppressed caffeine-induced Ca2+ responses in cells expressing the hTAS2R43 and hTAS2R46 bitter-taste receptors.

Food protein hydrolysates created by natural fermentation have been used for centuries as food flavorings. The aim of this study was to define the key umami-active fraction of modernized Korean soy sauce (mJGN) and the impact thereof on bitter-masking of human sensory and bitter-taste receptor-expressing cells. We found strong correlations between taste profiles of mJGN and a contained fraction (F05). The latter contained compounds of less than 500 Da, and elicits a distinct umami taste. Both free amino acids and Glu-enriched oligopeptides are suggested to be crucial in terms of the effects of F05 on taste. F05 not only reduced human-perceived bitterness, but also effectively suppressed the intracellular Ca2+ response induced by caffeine in the hTAS2R43 and hTAS2R46 human bitter-taste receptor-expressing cells. This suggests that F05, a key umami-active fraction of mJGN, contains components that at least partially modulate human bitter-taste receptor action, improving food flavor.