Amino Acid Bitterness:\nCharacterization and Suppression

Amino acids are necessary for life, and many must be\nconsumed because\nthey cannot be endogenously synthesized. Typically, we eat them as\nproteins and peptides, which have little taste. However, we also directly\ningest free amino acids, several of which are aversive because they\nelicit bitterness. This bitterness often prevents many patient populations\nfrom taking formulas and supplements containing free amino acids.\nHere, we characterize which amino acids are the most bitter, their\nconcentration-intensity functions, and individual differences in bitterness\nperception, and we explore how sodium salts suppress the bitterness\nof amino acids. We found that the essential amino acids comprise the\nmost bitter stimuli, with six of them conveying the most bitterness.\nClustering and correlating amino acids by individual differences in\nbitterness perception show that there are approximately four groupings\nof amino acids and suggest that within these clusters, amino acids\nmay be activating the same or overlapping TAS2Rs. We also show that\nbitterness can be largely suppressed by sodium salts for 5 of the\n6 most bitter amino acids. These results hold promise for managing\nthe bitter taste of nutritional supplements that contain amino acids\nand improving compliance.