Abstract

This study sought to investigate the relationship between PTC taste sensitivity and acceptance to dark chocolate. This study hypothesizes that a PTC taster is likely to have a higher tendency to dislike dark chocolate since they are more sensitive to the bitterness taste. Similarly, it is hypothesized that a non-PTC taster has a higher tendency to like and enjoy dark chocolate. The study used 23 students from the Generic Lab Class, who were asked whether they were tasters or non-tasters of PTC and whether they like or dislike chocolate after tasting PTC. The results show that both PTC tasters and non tasters like dark chocolate, and that the ability to test PTC is not related to the preference for dark chocolate. There were no significant differences in food preferences for mildly sweet foods among PTC tasters and non-tasters. From the results reported in this study, it can be inferred that, whereas the differences as regards bitter taste perceptions have been significant, they have minimal impacts on the food preferences and eating habits.

Introduction

Food preferences vary among people; no two individuals can have the same food preferences. Several diverse factors that influence food preferences consist of sex and age of the person, individual metabolic factors and sex of the person, quantity of food intake, and food availability. A study by Krondl et al (190) involving newborns affirmed the existence of genetic inborn food dislikes and likes. Environmental influences are capable of modifying the taste aversions present in infants; nevertheless, most are still present in young children. Different studies have found a positive correlation existing between the food preferences of children and the food preferences of their parents (Wooding et al 933). Others have also reported no correlations between the food preferences of children and their parents’ preferences. In situations whereby an individual’s food preference is the same as the parent’s food preferences, it is because of the culture in which the individual is living. Studies involved in the psychophysics of taste usually utilize threshold test measurements (Wooding et al 933). A person’s threshold level for bitter taste influences his/her food preferences; however, the food preferences do not influence a person’s threshold level for bitter taste (Ly and Drewnowski 46). Of the four tastes (bitter, sour, sweet and salty), bitter is the most aversive. Some of the factors that influence the bitter threshold level consist of disease and age.

Phenylthiocarbamide (PTC), an anti-thyroid compound, has been reported to be perceived bitter by 70% of North American and European populations (Drewnowski and Gomez-Carneros 1425). The remaining 30% are not capable of tasting PTC. However, the mode of inheritance regarding the inability to test PTC is a subject of contention. Some of the factors that have been established to influence the ability to test PTC include liquor consumption, age and sex. The manner in which people perceive taste varies among people, which accounts for differences in food preferences (Ly and Drewnowski 42). Another factor that influences the sensitivity towards PTC is sex; women tend to be more sensitive towards PTC when compared to men; nevertheless, there is no link between the heredity for the capability to taste PTC (Drewnowski and Gomez-Carneros 1430). Progress regarding the capability to test PTC has been reported in both females and males in the course of puberty. Individual differences regarding sensitivity towards PTC have been established to be closely associated with particular disease types. Smoking and age do not influence sensitivity towards PTC; however, a number of researchers have argued that age is likely to be a significant factor influencing sensitivity to PTC.

The consumption of liquor is also likely to have an impact on PTC sensitivity. Kang et al (6) hypothesized correlation between PTC sensitivity and liquor consumption. Using Korean participants, Kang et al (24) reported lower PTC thresholds for subjects who reported consuming and liking liquor.  The role of hereditary in food preference has been explored by Krond et al (20), who studies 23 sets of twins (13 monozygotic and 10 di-zygotic pairs). Krond et al (6) used a food preference questionnaire containing 8 foods that are PTC-related including green beans, cauliflower, broccoli, strawberries, cabbage, Brussels sprouts, spinach, and turnips. The results reported that PTC testers found saccharin and caffeine to be bitter when compared to non-tasters.

This study sought to investigate the relationship between PTC taste sensitivity and acceptance to dark chocolate. This study hypothesizes that a PTC taster is likely to have a higher tendency to dislike dark chocolate since they are more sensitive to the bitterness taste. Similarly, it is hypothesized that a non-PTC taster has a higher tendency to like and enjoy dark chocolate. The following are the hypotheses used in this study:

H1: A PTC taster is likely to have a higher tendency to dislike dark chocolate

H2: A non-PTC taster has a higher tendency to like and enjoy dark chocolate

Methods and Materials

            The study used 23 students from the Generic Lab Class, who were asked whether they were taster or non-tasters of PTC and whether they like or dislike chocolate after tasting PTC. Participants rinsed their mouth with water prior to the experiment in order to remove any residue. Each student was provided with a PTC testing paper (Carolina: 0.007 mg), dark chocolate (4.56g of Hershey’s Special dark chocolate, large cups to be used for rinsing. The PTC testing paper was used to classify the participants as either tasters or non-testers. After being grouped into tasters and non-tasters, participants consumed dark chocolate and then allowed to state whether they liked or disliked the taster of dark chocolate. Each participant provided a record of his/her ability to test PTC with a matching preference for dark chocolate.

Statistical analysis for this study was performed using Statistics Package for Social Students (SPSS) for Windows Version 20. Data was fed into the SPSS software for analysis. Data relating to PTC taste status (taster or non taster) and dark chocolate (preference) were analyzed using cross tabulations and ?² statistics. A chi-square test was used to determine if there is a significant relationship between the ability to test PTC and the preference for dark chocolate. Significant correlations between PTC taste status and dark chocolate preference among participants was tested by Pearson chi square.

Results

            Out of the 23 participants who took part in this study, 22 were PTC tasters and only 1 PTC non-tester. The preference for dark chocolate between PTC tasters and PTC non-tasters is shown in the figure 1 below. From the figure, out of the 22 PTC tasters, 10 (45.5 percent) whereas 12 (54.5 percent) liked dark chocolate. The PTC non-tester in this study liked dark chocolate.

 

Figure 1: Preference for dark chocolate among PTC tasters and non-tasters, n=23

A cross tabulation shown in table 1 below was used to determine the theoretical relationship between the ability to test PTC and the preference for dark chocolate. From the cross tab below, it is evident that a majority of the PTC tasters (54.5 percent) like dark chocolate. The theoretical observation from this cross tab is that PTC tasters have a preference for dark chocolate. Similarly, 100 percent of PTC non-tasters have a preference for dark chocolate. A chi-square test of independence was used to investigate the relationship between the ability to test PTC and preference for dark chocolate. The results show that the relationship between these variables is not statistically significant, ?² (1, N = 23) =.804, p>.01. Both PTC tasters and non-tasters prefer dark chocolate. Regarding the continuity correction, it is evident that ? (1) = 0.000, p = 1.0; as a result, there is no statistically significant association between the ability to test PTC and the preference for dark chocolate.

 

PTC Taster or Non-Taster * Preference for Dark Chocolate Cross tabulation
			Preference for Dark Chocolate		Total
			Dislike	Like
PTC Taster or Non-Taster	Non Taster	Count	0	1	1
		% within PTC Taster or Non-Taster	0.0%	100.0%	100.0%
	Taster	Count	10	12	22
		% within PTC Taster or Non-Taster	45.5%	54.5%	100.0%
Total		Count	10	13	23
		% within PTC Taster or Non-Taster	43.5%	56.5%	100.0%

Table 1: Cross tabulation for the ability to test PTC (taster or non-taster) versus preference for dark chocolate (like or dislike)

 

Chi-Square Tests
	Value	df	Asymp. Sig. (2-sided)	Exact Sig. (2-sided)	Exact Sig. (1-sided)
Pearson Chi-Square	.804a	1	.370
Continuity Correctionb	.000	1	1.000
Likelihood Ratio	1.176	1	.278
Fisher’s Exact Test				1.000	.565
N of Valid Cases	23

Table 2: Chi square test for independence

Discussion

 

From the results, both hypothesis 1 and 2 are rejected. The results show that both PTC tasters and non tasters like dark chocolate, and that the ability to test PTC is not related to the preference for dark chocolate. This finding is similar to the findings reported by past studies (Ly and Drewnowski 45). The ability to test PTC did not have an influence on the food preference for mildly sweet foods such as chocolates (Ly and Drewnowski 45 Wooding et al 933). Simply stated, there were no significant differences in food preferences for mildly sweet foods among PTC tasters and non-tasters. From the results reported in this study, it can be inferred that, whereas the differences as regards bitter taste perceptions have been significant, they have minimal impacts on the food preferences and eating habits. For instance, the study reported insignificant difference (no association) between PTC tasters and non-tasters as regards their preference (like or dislike) for dark chocolate. Chocolate contains bitter substances such as polyphenols, which is suppressed using high fat and sugar content. Basing on the findings reported in this study, evidence suggests that sweetening of chocolate may be unnecessary since its preference is unrelated to the ability to taste PTC, which is bitter. The practice debittering chocolate and other foods is common in the food industry; however, the results reported in this research affirm no link between PTC tasting and preference for mild sweet foods such as dark chocolate. This study has only focused on the food preference, leaving a potential gap for future studies to investigate the link between PTC taster status and perceived bitterness, and investigate whether perceived bitterness is a mediating factor in food preference.

Works Cited

Drewnowski, Adam and Carmen Gomez-Carneros. “Bitter taste, phytonutrients, and the consumer: a review.” The American Journal of Clinical Nutrition 74.6 (2000): 1424-1435.

Kang, Y, W Cho and K Yurn. “Taste Sensitivity to PTC of Korean Population .” Eugenics Quarterly (1967): 1-4.

Krondl, M, et al. “A Twin Study Examining the Genetic Influence of Food Selection.” Human Nutrition: Applied Nutrition (1983): 189-198.

Ly, Agnes and Adam Drewnowski. “PROP (6-n-Propylthiouracil) Tasting and Sensory Responses to Caffeine, Sucrose, Neohesperidin Dihydrochalcone and Chocolate.” Chemical Senses 26.1 (2001): 41-47.

Wooding, Stephen, et al. “Independent evolution of bitter-taste sensitivity in humans and chimpanzees.” Nature 440.7086 (2006): 930–4.