New insight into umami receptor, umami/umami-enhancing peptides and their derivatives: A review

Background: The structure and mechanism of umami taste receptor remain largely unclear, thus, far more research is necessary to increase the knowledge of tasty modalities. Umami/umami-enhancing peptides and their derivatives are widely distributed in foods and have been reported to play important roles in food taste through different modes of interactions with the umami receptors. Scope and approach: In this review, recognition of umami taste receptor, along with the structures and possible binding sites (orthosteric and allosteric sites) of umami/umami-enhancing peptides and their derivatives, was firstly described. The validation of the structural characteristics of umami and umami-enhancing substances and their binding sites to the receptors allows better understanding of the sensing mechanisms of umami taste. Key findings and conclusions: There are several receptors responsible for the recognition of umami substances and each receptor may be activated through different mechanisms. Besides orthosteric sites, allosteric binding sites are also found and being emphasized as it may explain why complementary interactions among umami or umami-enhancing peptides and their derivatives as well as an increase in hydrophilicity of compounds may promote food acceptance. Unlike di-/tri-peptides, the spatial structure is the most critical factor for the taste modality of long-chain umami peptides besides amino acid composition. Quite a few of these peptides and derivatives can also act as taste enhancing agents. Multiple polar moieties in peptides and their derivatives may trigger the umami/umami-enhancing property. Maillard reaction and treatment with certain enzymes could facilitate the yield of umami/umami-enhancing peptide derivatives with increased hydroxyl or amino groups.