The Relationship between Phenylthiocarbamide (PTC) and n-6-Propylthiouracil (PROP) Taster Status and Taste Thresholds for Sucrose and Quinine

Abstract

Objective The aim of this study was to investigate the relationship of taster status with taste detection and recognition thresholds for sucrose and quinine.

Design Sixty-nine subjects (35 men and 34 women; mean age, 23.9 ± 1.2 years) were included. Stimulus fluids were prepared, one each for phenylthiocarbamide (PTC), 6-n-propylthiouracil (PROP), sucrose and quinine HCl. In each series, successive solutions, which comprised a total of 15 grades, differed by 0.25 log units of the molar concentration. Two concentrations of NaCl (0.32 and 1.0 M) were prepared. The subjects were classified as nontasters and tasters using their PTC and PROP perceptions. Tasters were classified as medium-tasters and supertasters by the ratio of perceived bitterness of above-threshold PROP relative to the perceived saltiness of NaCl (PROP ratio). Taste detection and recognition thresholds for sucrose and quinine were determined by standard two-alternative forced choice trials. A Student's t-test, a Pearson's correlation analysis and linear contrasts in a one-way analysis of variance (ANOVA) were used.

Results The percentages of nontaster, medium-taster and supertaster were 13, 70 and 17%, respectively. There were no significant gender differences in the taste detection and recognition thresholds for sucrose and quinine. The threshold for PTC and PROP showed significant correlations with taste threshold for quinine. Linear contrast in one-way ANOVA showed that the greater the value of PROP ratio, the more sensitive to sweet and bitter tastes (p < 0.001).

Conclusion The PTC and PROP taster status is closely related with taste detection and recognition thresholds for sucrose and quinine.