6-n-Propylthiouracil (PROP) taster status determination and its relation to tongue anatomy, food liking and intake

This Ph.D. dissertation examined PROP taster status determination using current methods and a new method. This new method was used to examine the effect of taster status on tongue anatomy, liking and intake of bitter foods, repeated scaling of PROP, and performance on difference tests using PROP solutions.; The new method used visual, tactile, and kinesthetic (physical) stimuli as a standard in place of the NaCl standard used in current procedures. Good agreement (76%) was found between the physical and NaCl standard methods. The physical stimuli method was used to test the hypothesis that individuals who are more sensitive to PROP are more sensitive to other taste stimuli. In general, intensities of some caffeine, sucrose, and MSG solutions were rated significantly higher by supertasters than nontasters (p < 0.05). However the findings did not extend to all solutions tested, suggesting PROP taster status may only affect perception of specific stimuli. No significant differences in fungiform and circumvallate papillae numbers were found among taster groups.; Few significant differences were found among taster groups for liking for, and intake of bitter foods. Soy products were consumed significantly more often by supertasters than tasters, which may be due to cultural factors of the sample population. Cultural and environmental factors may have a stronger effect on food liking and intake than genetic factors.; Initial evaluations of intensity ratings of PROP showed supertasters' psychophysical curves were initially significantly higher (p < 0.05) than those of tasters, yet they became statistically indistinguishable with additional sessions. Intensity ratings of other stimuli (NaCl, physical stimuli) were not significantly different among taster groups across all sessions. The effect was specific to PROP, and may be caused by range effects and/or panelists' unfamiliarity with PROP in early sessions.; A preliminary examination of taster status and performance on paired comparison tests using PROP solutions showed that supertasters had significantly more (p < 0.05) correct responses for several PROP pairs tested. Nontasters had significantly fewer (p < 0.05) correct responses for all PROP pairs tested. These results support development of a suprathreshold forced-choice protocol for taster status determination.