COMPARISON OF NEW AND EXISTING METHODS FOR THE CLASSIFICATION OF INDIVIDUALS ACCORDING TO 6-N PROPYLTHIOURACIL (PROP) TASTER STATUS

We developed an alternative method for the determination of 6-n propylthiouracil (PROP) taster status that is based on the comparison of intensity ratings of PROP solutions with intensity ratings of visual, tactile, and kinesthetic (physical) stimuli. We then compared the classification obtained with this method to those derived from traditional approaches. One hundred and forty-two subjects rated the perceived intensity of 0.000032, 0.00018, 0.00032, 0.0018, and 0.0032 M PROP, and 0.01, 0.032, 0.1, 0.32, and 1.0 M NaCl, as well as five levels each of perceived roughness of sandpaper, grayness of shades, and thickness of honey and water mixtures on the Labeled Magnitude Scale (LMS). Ratings for 0.00032 M PROP and 0.1 M NaCl were also compared in a one solution test. Subjects were classified as PROP nontasters, tasters or supertasters by all three procedures. Seventy-six percent of panelists were classified in a similar way by the physical stimuli and NaCl procedures, while 70% percent of panelists were classified similarly by the physical stimuli procedure and the one solution test, as well as by the NaCl procedure and the one solution test. Only 65% of panelists were classified similarly by all three procedures. Further, in replicate ratings of PROP solutions, supertasters' evaluations of PROP at all concentration levels decreased significantly (P < 0.01) from the first to the second rating. It is evident from these findings that the method used to determine PROP taster status can greatly influence the outcome of any investigation of PROP taster status on other phenotypes.