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Flavor and texture contribute to the perception of creaminess in dairy products, but the nature of this interaction is not well understood. Previous studies on the genetic ability to perceive the bitter compound 6-n-propylthiouracil (PROP) reveal the existence of individual differences in creaminess perception. The objective of the present study was to use PROP-classified subjects to gain insight into this individual variation to better understand the cues for creaminess in dairy products, and to ascertain the contributions of flavor and texture to the integrated perception of creaminess. Ten nontasters and 10 supertasters of PROP participated in the study. Subjects evaluated nine commercial dairy products using Free-Choice Profiling (FCP), a type of descriptive analysis that allows subjects to rate products on individual lists of descriptors. Generalized Procrustes Analysis was used to develop separate consensus spaces for nontasters and supertasters. The models for both groups accounted for approximately 54% of the variance in the data and were resolved in two dimensions (a dairy flavor/texture axis and a sweet-sour continuum). The products were arranged in a similar pattern along the dimensions in both models. However, nontasters used a limited number of simple terms (sour, sweet, milky and mouthcoating) to describe the products, whereas supertasters used a more complex vocabulary (rich, buttery, creamy, light, grainy, gritty and sandy). The model for nontasters gave equal weight to the sweet-sour and dairy flavor/texture dimensions (28 and 26% variance, respectively); whereas, the model for supertasters relied more heavily on the dairy flavor/texture dimension (34% variance), and less so on the sweet-sour dimension (20% variance). These data suggest that the overall impression of creaminess was similar for nontasters and supertasters, but the cues the two groups used to judge creaminess differed.

The purpose of this study was to develop a quantifiable method to fix 6-n-propylthiouracil (PROP) onto filter paper disks and to test the validity of the method relative to the three-solution test, previously developed in this laboratory. Filter paper disks were impregnated with 50 mmol/l PROP or 1.0 mol/l NaCl then dried. The concentration of PROP per disk was determined to be 0.280 mg+/-2.2% (CV) by ethanol extraction. Subjects were studied in two groups (n=62 per group). All subjects were initially classified by the three-solution test and then were independently classified by the paper disk test. In the paper disk test, group means for PROP (+/-95% confidence interval) were calculated and used to establish numerical cutoff scores for taster group classification. Cutoff scores for Group 1 were used to classify subjects in Group 2, verifying that the cutoffs were applicable to another subject group. The percentage of nontasters, medium tasters, and supertasters identified by paper disk was 27%, 42%, and 31%, respectively, which is consistent with expected frequencies in the population. For Group 1, the agreement between the two classification methods ranged from 86% to 94% across taster groups. For Group 2, the agreement ranged from 83% to 100%. The contingency coefficient (P) of the degree of association between the two classification methods was high (P=0.77 and P=0.74 for Groups 1 and 2, respectively; P< or =.001). These results demonstrate that the paper disk method is a reliable screening tool for assessing sensitivity to PROP that has numerous applications in basic and applied research.