Abstract
Miraculin is a glycoprotein, and it changes the perceived quality and intensity of tastes (especially, sourness and sweetness). The oral application of miraculin in a high concentration elicits a strong sweetness for sour tastants. However, the mixing of different tastants increases or decreases the intensity of the taste elicited in comparison with the intensities elicited by the individual sour tastants. The synergy between different (e.g., sweetness and sourness) or similar taste qualities can be responsible for the changes in the perceived taste intensities. Despite the characteristics of miraculin and the sour tastant mixtures, the effects of miraculin on mixed acid solutions are still unknown. The goals of this study were to assess the following: 1) the intensities of the sourness and sweetness of mixed acid solutions before and after the oral application of miraculin and 2) the intensity of the sweetness of the mixed acid solutions after the oral application of miraculin. For twenty healthy young adults, sensory evaluation experiments examined the perceived intensities of taste (sweetness, sourness, and astringency) and the overall odor of six organic acid solutions (2.3 × 10–2 M of citric acid and three-binary and two-trinary mixtures including citric acid that ranged from 2.24 to 2.48 in average pH). The application of miraculin elicited sufficient sweetness, but it did not show statistically significant differences in the intensities of sweetness among the six acid solutions. Except for the sweetness, all of the four sensory items exhibited significant changes among the six solutions both before and after the application of miraculin, while the average scores for these items did not correlate with the average solution pH values. These results suggest that the binary and trinary mixed acid solutions affect the sourness both before and after the oral application of miraculan; however, there was no effect on the sweetness.
Highlights
Miraculin is a glycoprotein that changes sourness into sweetness in the mouth [1] [2]
This study found significant differences in the average pH values among the six solutions used (Table 1), and these differences did not determine the intensities of the sensory evaluation items including sourness before and after miraculin was applied, as the average pH values were not significantly correlated with any of the sensory intensities
A psychophysical study showed that the perceived intensity of sweetness after the miraculin was applied increased with an increase in the concentration of an acid solution that was tasted after the miraculin [16]
Summary
Miraculin is a glycoprotein that changes sourness into sweetness in the mouth [1] [2]. When miraculin binds to the sweet receptors on the taste buds on the tongue or the soft palate, sour foods evoke an action potential on the taste nerves that conduct the sweet sensation. The intensity of sweetness becomes stronger as the intensity of sourness becomes stronger with organic acids (e.g., citric acid). The concentration of hydrogen ions affects the intensity of the sourness, hydrogen ions are not the only determinant of taste [3]. A study on the mixing of solutions with similar taste intensities, sour solutions, found that the sourness of binary acid mixtures is stronger than that of single acid solutions [6] [7]
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