(OR16-02-23) Individual Differences in Amino Acid Bitter Taste and Its Suppression With Salts

Objectives: Amino acids are the basic unit of protein and play important roles in muscle growth, cell signaling, and health. Free amino acids are commonly found in both natural foods and in health supplements. Products with free amino acids can stimulate “off-tastes” that interfere with consumption and medical compliance. The primary off-taste generated by free amino acids is bitterness. In this study, we aimed to characterize the taste profiles of 19 amino acids, to identify which amino acids generate bitter taste, to suppress their bitterness with sodium salts, and to identify clusters among amino acids based on individual differences in subjects’ bitterness perception.

Methods: Subjects were trained to recognize the five main taste qualities (sweet, bitter, sour, salty, and umami). Participants then tasted 19 amino acids and rated the intensity of each taste quality for each amino acid. Subjects also rated the bitterness of amino acids alone and in combination with sodium salts (NaCl, NaGluconate, NaPropionate, NaSalicylate, and Na Adenosine Monophosphate) on a labeled magnitude scale. Relationships between bitter amino acids and common bitter taste compounds were analyzed by correlation matrix analysis, Principal Component Analysis, and cluster analysis. 

Results: Subjects identified isoleucine, leucine, methionine, phenylalanine, tryptophan, and arginine as the amino acids that elicited bitterness as the main taste quality. The bitter taste of all these amino acids was reduced to varying extents by the sodium salts tested, with the exception of arginine. These amino acids and their metabolites were grouped into three to four distinct clusters based on the subjects' individual sensitivities to bitterness.

Conclusions: Bitter amino acids form clusters based on their individual differences, suggesting that there may be several bitter taste receptors that respond to amino acids. Amino acid bitterness can be successfully reduced by various blocking agents. In the future, combinations of the bitter blockers tested may be used to minimize amino acid aversiveness. Minimizing the bitter taste of free amino acids found in muscle growth aids for the elderly, oral rehydration and diarrhea products, and infant hydrolysate formulae can increase compliance to these interventions and improve patient health.

Funding Sources: This work was funded by Ross Laboratories.