Pre-treatment with creatinine alters the perceived bitterness-sweetness balance of L-histidine in young Japanese female participants.

Taste modulation induced by interactions among specific compounds remains poorly understood. L-histidine and creatinine are both bitter compounds abundant in dried bonito dashi. This study investigated whether 10 bitter compounds could shift the taste quality of L-histidine from bitterness toward sweetness, as assessed by sensory evaluation using a fixed-sum method. When presented alone, 4% L-histidine elicited bitterness accompanied by weak sweetness, whereas iso-bitter creatinine evoked predominantly bitterness. Remarkably, pre-stimulation with creatinine shifted the taste quality of L-histidine toward sweetness. Similar effects were observed after pre-stimulation with isoleucine, tryptophan, phenylalanine, and creatine, but not with histidine, valine, leucine, caffeine, or carnosine. This effect was transient, as increasing the interval after creatinine pre-stimulation restored the bitterness of L-histidine. In addition, 0.1% NaCl altered the bitterness-to-sweetness balance of L-histidine toward sweetness after pre-stimulation with creatinine. The taste quality of histidine alone was highly sensitive to pH: bitterness peaked at pH 7.0, whereas sweetness increased under alkaline conditions. In contrast, varying the pH of the pre-stimulation solution between 5.0 and 8.0 did not affect the modulation of L-histidine taste. These findings demonstrate a previously unrecognized histidine-specific form of taste modulation, suggesting interactions among naturally coexisting bitter compounds may dynamically alter taste qualities in traditional broths and other complex foods.