The relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) taster status and taste thresholds for sucrose and quinine

doi:10.1016/j.archoralbio.2005.10.002

Archives of Oral Biology

Volume 51, Issue 5, May 2006, Pages 427-432

https://doi.org/10.1016/j.archoralbio.2005.10.002 Get rights and content

Summary

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.

Introduction

Phenylthiocarbamide (PTC) and its chemically related compound, 6-n-propylthiouracil (PROP), provide an extremely bitter taste to some subjects (tasters) but are tasteless or only slightly bitter to others (nontasters).1, 2, 3, 4 Although approximately 15–30% of people are known to be nontasters genetically,5, 6 the taster/nontaster frequency differs among ethnic groups.7, 8, 9, 10 Noting that the taster group showed much variability in taste threshold, it was proposed that sub-populations of ‘supertasters’ and ‘medium-tasters’ might exist. Supertasters were distinguished from medium-tasters by their elevated ratio of perceived bitterness of above-threshold PROP solutions relative to the perceived saltiness of NaCl solutions.¹¹ Tasters, especially supertasters, may have a reduced dietary exposure to bitter but beneficial phytonutrients found in vegetables and fruits.12, 13 Therefore, screening for PTC and/or PROP (PTC/PROP) taster status may have a public health importance.14, 15

The PTC/PROP perception has been known to correlate with the taste perception of various primary taste qualities,16, 17 especially bitter and sweet tastes.18, 19, 20, 21 However, these previous results on the relationship of PTC/PROP perception with perception of taste quality were based on food aversions and taste intensities, not on threshold tests, which are the most widely used quantitative taste tests. Of the available quantitative threshold tests, a taste detection threshold test establishes the lowest concentration at which a substance can be distinguished from water. In contrast, a taste recognition threshold test determines the lowest concentration at which the taste quality of a substance can be identified.²²

The aim of this study was to investigate whether or not the PTC/PROP taster status is related to the taste detection and recognition thresholds for sucrose and quinine in the young adult population.

Section snippets

Participants

Sixty-nine subjects (35 men and 34 women; mean age, 23.9 ± 1.2 years), who were students of the School of Dentistry at Seoul National University, were enrolled in the study. All of them were nonsmokers. A questionnaire, which included questions regarding chronic sinusitis, chronic obstructive pulmonary disease, diabetes, psychological disorders, loss of olfactory sense, history of ear surgery or tonsillectomy and dry mouth, was used to select the subjects. The subjects did not show any positive

Results

As shown in Table 1 and Fig. 1, the percentages of nontasters, medium-tasters and supertasters were 13, 70 and 17%, respectively. Taster/nontaster status determined using the PTC was exactly in accordance with that found using the PROP (data not shown).

The detection and recognition thresholds for sucrose and quinine HCl in all subjects are shown in Table 2. Although each detection and recognition threshold was higher in men than in women, there was no significant difference.

As shown in Table 3,

Discussion

The percentage of nontasters among Korean young adults was found to be 13% in this investigation and 20% in a previous study.¹⁰ These numbers are higher than those found in American Indians, and lower than those observed in European and American Caucasians.7, 9 The percentage of supertasters was 17% in this study, which was lower than the results of previous studies reporting 21–30% of supertasters.11, 13, 31, 32, 33, 34, 35 This is likely explained by a combination of factors, such as ethnic

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The relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) taster status and taste thresholds for sucrose and quinine

Summary

Objective

Design

Results

Conclusion

Introduction

Section snippets

Participants

Results

Discussion

Oral Surg Oral Med Oral Pathol Oral Radiol Endod

Physiol Behav

Am J Clin Nutr

J Am Diet Assoc

J Am Diet Assoc

Appetite

Physiol Behav

Food Qual Pref

Physiol Behav

Physiol Behav

Physiol Behav

Physiol Behav

NeurobiolAging

Physiol Behav

The relationship between chemical constitution and taste

Proc Natl Acad Sci USA

Taste blindness to phenyl-thio-carbamide and related compounds

Psychol Bull

The measurement of taste sensitivity to phenylthiourea (P.T.C.)

Ann Eugen

PTC taste blindness and the taste of caffeine

Nature

Textbook of medical physiology

Comparing sensory experiences across individuals: recent psychophysical advances illuminate genetic variation in taste perception

Chem Senses

Observation on taste blindness

Science