RELATIONSHIP OF PROP (6-N-PROPYLTHIOURACIL) TASTER STATUS WITH THE BODY MASS INDEX AND FOOD PREFERENCES OF FILIPINO ADULTS

The study determined the 6-n-propylthiouracil (PROP) status of Filipino adults and how it relates to their body mass indices (BMI) and food preferences. Self-reported food preference checklists were administered to 100 male and female adults aged 18–60, classified according to BMI. Increasing concentrations of PROP and NaCl solutions were rated in labeled magnitude scale to establish the PROP taster status of the selected respondents. The Filipino adult respondents were composed of 12% nontasters, 45% medium tasters and 43% supertasters. No association ( P >  0.05) between BMI and PROP taster status was found. Sweet-tasting foods were the most preferred and bitter-tasting foods were the least preferred within each taster status. Furthermore, medium tasters and supertasters had the highest acceptance for meats, fish and poultry, and least acceptance for beverages, which were mostly bitter. Decreased preferences for fats and oils, sugars and confectionery, and beverages were correlated ( P <  0.05) with responsiveness to PROP.

PRACTICAL APPLICATIONS

The research provides a general baseline data of the PROP taster status of Filipino adults. The findings from this study can be used as a reference and can be compared to similar studies conducted in other countries. Likewise, the information from the study can add to the scarce data for taste genetics specifically for the Asian population. The relationship of PROP taster status with body mass index and food preferences can be a guide in the design of products and dietary plans. Likewise, the study would be a means to understand why people vary in liking for particular food items and how these can be reflected in their food consumption and nutritional status.     

SENSORY EVALUATION OF VANILLA-DAIRY DESSERTS BY REPERTORY GRID METHOD AND FREE CHOICE PROFILE

“Natillas” are semisolid dairy desserts widely consumed in Spain, with notable differences existing between commercial brands in their composition and sensory and physical properties. The repertory grid method, in conjunction with the free choice profile (FCP), was used to provide data on how consumers perceived eight commercial “natillas” samples. The most frequent terms used were: vanilla flavor, sweetness, consistency and liquid texture as described by 77, 67, 57 and 53% of the consumers, respectively. A three‐dimensional solution was chosen. Dimension 1 accounted for 27.23% of variance and separated the samples largely by yellow‐color intensity and consistency. Dimension 2 (15.88%) was mainly related to the visual attributes of texture, creaminess and different notes of flavor. The third dimension (11.34%) was related to structural‐texture attributes, orange‐yellow color and acid and artificial flavors. The assessors plot showed two clusters. Analysis of each group data revealed differences in their perception of sample variation, mainly regarding texture and color.     

Measures of individual differences in taste and creaminess perception

Previous reports that the sensitivity to the bitter tasting substance 6-n-propylthiouracil (PROP) is related to the sensitivity to other tastes, to chemical irritants, and to fats and oils have led to adoption of PROP as a measure of general oral sensitivity and as a predictor of dietary habits that could impact health. The results, however, have not been consistent. It was recently discovered that the ability to perceive "thermal taste" (i.e., sweetness from thermal stimulation alone) was associated with higher responsiveness to 4 prototypical taste stimuli but not to PROP. This finding implied that individual differences in taste perception are determined in large part by factors other than those related to genetic expression of the PROP receptor. The present study followed up this observation by comparing individual differences in perception of 4 prototypical taste stimuli (sucrose, NaCl, citric acid, and quinine) and PROP under conditions that also enabled assessment of the reliability of individual intensity ratings of taste. Creaminess ratings of 3 milk products that had different fat contents were also collected to investigate further the relationship between taste and oral somatosensory perception. The results showed that intensity ratings across 2 trials were significantly correlated for all 5 taste stimuli and that averaging across replicates led to significant correlations among the 4 prototypical stimuli. In contrast, the bitterness of PROP was correlated only with the bitterness of quinine. None of the taste stimuli, including PROP, was significantly correlated with ratings of creaminess. These results imply 1) that with the exception of PROP, as few as 2 intensity ratings of common taste stimuli can reveal individual differences in overall taste perception and 2) that any relationship between taste and oral sensation is too weak to be detected under the same conditions. Accordingly, the results support other evidence that the genetic factors which determine the ability to perceive PROP do not play a major role in overall taste and oral somatosensory perception.     

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.     

Adiposity in Middle‐aged Women is Associated with Genetic Taste Blindness to 6‐n‐Propylthiouracil

Objective: Taste blindness to the bitterness of 6‐n‐propylthiouracil (PROP) may be a genetic marker for food preferences and dietary choices that ultimately influence body weight. A previous study in middle‐aged women showed that those who were taste blind to PROP (i.e., nontasters) had higher BMIs than those with the greatest sensitivity to PROP (i.e., supertasters). This study tested the hypothesis that the nontaster phenotype was associated with greater adiposity in middle‐aged women. Research Methods and Procedures: Forty women with a mean BMI of 26.6 ± 1.3 kg/m² and a mean age of 41.8 ± 1.8 years were recruited from the local community. They were classified as nontasters (n = 8), medium tasters (n = 18), or supertasters (n = 14) of PROP using a filter paper screening procedure. Anthropometric measures included height, weight, body fatness, triceps skinfold thickness, and waist circumference. Dietary restraint and disinhibition were also measured to assess cognitions associated with body weight. Results: BMI was 6.2 units higher in nontaster women compared with supertaster women (29.7 ± 0.9 vs. 23.5 ± 0.9, respectively; p < 0.05). Body fatness (p < 0.01) and triceps skinfold thickness (p < 0.05) were also higher in these women. Waist circumference showed a trend in the appropriate direction. Although disinhibition was associated with greater adiposity, the relation between PROP status and adiposity was not altered after controlling for disinhibition. Discussion: The PROP nontaster phenotype was strongly associated with several measures of adiposity in middle‐aged women. These data confirm our previous findings and suggest that the PROP polymorphism may be a reliable indicator of weight gain susceptibility.     

Responsiveness to 6-n-propylthiouracil (PROP) is associated with salivary levels of two specific basic proline-rich proteins in humans

Thiourea tasting can be predictive of individual differences in bitter taste responses, general food preferences and eating behavior, and could be correlated with saliva chemical composition. We investigated the possible relationship between PROP bitter taste responsiveness and the salivary proteome in subjects genotyped for TAS2R38 and gustin gene polymorphisms. Taste perception intensity evoked by PROP and NaCl solutions was measured in sixty-three volunteers (21 males, 42 females, age 25±3 y) to establish their PROP taster status, and 24 PROP super-tasters and 21 nontasters were selected to participate in the study. TAS2R38 and gustin gene molecular analysis were performed using PCR techniques. Qualitative and quantitative determination of salivary proteins was performed by HPLC-ESI-MS before and after PROP taste stimulation. PROP super-tastings was strongly associated with the 'taster' variant (PAV haplotype) of TAS2R38 and the A allele of rs2274333 polymorphism in the gustin gene and nontasting was associated with the minor alleles at both loci. ANOVA revealed that basal levels of II-2 and Ps-1 proteins, belonging to the basic proline-rich protein (bPRPs) family, were significantly higher in PROP super-taster than in nontaster un-stimulated saliva, and that PROP stimulation elicited a rapid increase in the levels of these same proteins only in PROP super-taster saliva. These data show for the first time that responsiveness to PROP is associated with salivary levels of II-2 peptide and Ps-1 protein, which are products of the PRB1 gene. These findings suggest that PRB1, in addition to TAS2R38 and gustin, could contribute to individual differences in thiourea sensitivity, and the expression of the PROP phenotype as a complex genetic trait.     

PERCEPTION OF FAT IN A MILK MODEL SYSTEM USING MULTIDIMENSIONAL SCALING

This study examined the contributions of stimulus fat content and flavor volatiles to the perception of fat in a milk model system. The model system was formulated by adding bland vegetable oil (0%, 5%, or 10% w/v) and natural cream flavor (0%, 0.5% or 1% w/v) to a skim milk base. Panelists judged pairs of samples for similarity on the basis of three attributes (fat content, mouthcoating and thickness) and the results were analyzed using a multidimensional scaling procedure. Two-dimensional solutions best represented the data. The stimulus spaces for fat content and mouthcoating were visually similar to each other and provided reasonable separation of the samples. Instrumental measures helped to define the underlying dimensions of the stimulus space for fat content. Dimension 1 related to texture and included the contributions of viscosity, and fat particle size and number distribution; dimension 2 related to flavor perception. The sample with a moderate fat content (5%) and the highest concentration of added cream flavor (1%) was perceived to be similar to the 10% fat samples with added flavor. Thus, the added flavor provided the sensation of higher fat content. These data suggest that flavor plays an important role in the preception of fat in dairy foods. A psychophysical model of fat perception in dairy foods is proposed which includes the contribution of viscosity, fat particle size and number distribution, and volatile flavor perceptions.     

Genetic Sensitivity to 6-n-Propylthiouracil (PROP) and Hedonic Responses to Bitter and Sweet Tastes

Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil(PROP) has been associated with greater acuity for bitter andfor some sweet tastes. Thus far, few studies have explored therelationship between PROP taste sensitivity and hedonic responsesto bitter and sweet. In this study, 87 normal-weight young womenwere divided into PROP non-tasters (n = 18), regular tasters(n = 49), and supertasters (n = 20), based on their PROP detectionthresholds and the scaling of five suprathreshold solutionsof PROP and NaCl. Non-tasters had thresholds >1.8 x 10^–4mol/l PROP. Supertasters had thresholds <3.2 x 10^–5mol/l PROP and PROP/NaCl ratios >1.70. As expected, dislikeof the bitter taste of PROP was determined by its perceivedintensity, which was greater among supertasters than among regulartasters or non-tasters. Significant correlations were observedbetween PROP taste thresholds and the sum of intensity ratings(r = –0.61) and between summed intensity and summed hedonicratings (r = –0.80). PROP taste sensitivity was weaklylinked to enhanced perception of sweet taste, but did not predicthedonic responses to sucrose or to saccharin solutions. Giventhat the dislike of PROP solutions is determined by their perceivedintensity, hedonic responses to PROP solutions may provide arapid way of screening for PROP taster status. Chem. Senses22: 27–37, 1997.     

Revisiting sugar-fat mixtures: sweetness and creaminess vary with phenotypic markers of oral sensation

Genetic variation in oral sensation presumably influences ingestive behaviors through sensations arising from foods and beverages. Here, we investigated the influence of taste phenotype [6-n-propylthiouracil (PROP) bitterness, fungiform papillae (FP) density] on sweet and creamy sensations from sugar/fat mixtures. Seventy-nine subjects (43 males) reported the sweetness and creaminess of water or milk (skim, whole, heavy cream) varying in sucrose (0-20% w/v) on the general Labeled Magnitude Scale. Sweetness grew with sucrose concentration and when shifting from water to milk mixtures--the growth was greatest for those tasting PROP as most bitter. At higher sucrose levels, increasing fat blunted the PROP-sweet relationship, whereas at lower levels, the relationship was effectively eliminated. Perceived sweetness of the mixture exceeded that predicted from the sum of components at low sucrose concentrations (especially for those tasting PROP most bitter) but fell below predicted at high concentrations, irrespective of fat level. Creaminess increased greatly with fat level and somewhat with sucrose. Those tasting PROP most bitter perceived greater creaminess in the heavy cream across all sucrose levels. Perceived creaminess was somewhat lower than predicted, irrespective of PROP bitterness. The FP density generally showed similar effects as PROP on sweetness and creaminess, (but to a lesser degree) and revealed potential taste-somatosensory interactions in weakly sweet stimuli. These data support that taste phenotype affects the nature of enhancement or suppression of sweetness and creaminess in liquid fat/sugar mixtures. Taste phenotype effects on sweetness and creaminess likely involve differential taste, retronasal olfactory, and somatosensory contributions to these perceptual experiences.     

COMPARISON OF ATTRIBUTE LIKING AND JAR SCALES TO EVALUATE THE ADEQUACY OF SENSORY ATTRIBUTES OF MILK DESSERTS

Just-about-right (JAR) scales and attribute liking questions are usually used to study consumer perception of the sensory characteristics of food products. The aim of the present work was to compare the performance of attribute liking and JAR scales to evaluate consumers' perceived adequacy of flavor and texture of milk puddings. Two groups of consumers were asked to evaluate eight milk desserts using (1) overall liking followed by attribute liking for texture and flavor and (2) overall liking followed by JAR scales for thickness, creaminess, sweetness and vanilla flavor. Overall liking scores were significantly different when JAR scales or attribute liking questions were considered. Texture, flavor and overall liking scores were highly correlated to each other, providing the same information. JAR scales correlated better with the intensity of sensory attributes evaluated by a trained sensory panel, being JAR percentages a reliable tool to study the adequacy of sensory attributes.

PRACTICAL APPLICATIONS

Results from the present work showed that consumers might not be able to independently evaluate their liking of different sensory attributes of a product. For this reason, the use of attribute liking questions for studying the adequacy of sensory attributes in complex products would not be recommended. JAR scales were better indicators of the adequacy of sensory attributes. Consumers were able to independently evaluate texture and flavor attributes using JAR scales. However, the influence of JAR scales on overall liking scores should be taken into account when including these scales on consumer studies.     

Inherited Taste Sensitivity to 6‐n‐Propylthiouracil in Diet and Body Weight in Children

Objective: Negative associations between the inherited ability to taste the bitter compound 6‐n‐propylthiouracil (PROP) and preference for fat and body weight have been observed in adults. This study tested the relationships among the ability to taste PROP, reported food intake, and body weight in young children. Research Methods and Procedures: Fifty‐three 4‐ to 5‐year‐old children were classified as tasters (N = 35) or nontasters (N = 18) of PROP using a standard screening solution. Anthropometric measures were taken in the laboratory. Mothers completed questionnaires to assess their child's food intake and their own dieting behaviors. Results: Nontaster boys had higher weight‐for‐height percentiles than taster boys (77th vs. 56th percentile, respectively), but the relationship was opposite for girls (p ≤ 0.05). Nontasters reportedly consumed a higher percentage of their daily energy from protein (p ≤ 0.01), mainly as high‐fat meat products. Tasters reportedly consumed a higher percentage of their daily energy from sugars (p ≤ 0.05), mainly in the form of brownies, doughnuts, cookies, soft drinks, and juice drinks. There were no differences between tasters and nontasters for reported intake of grains, fruits, vegetables, dairy products, or discretionary fats. Discussion: This study is the first, to our knowledge, to report weight differences in children as a function of their PROP status. Genetic taste factors seem to play a role in the development of dietary patterns and weight differences in young children, but the nature of these relationships may vary with gender.     

Binary taste mixture interactions in prop non-tasters, medium-tasters and super-tasters

It is generally assumed that the mutual, but asymmetric, suppression of the components in binary taste mixtures is an invariant property of the human psychophysical response to such mixtures. However, taste intensities have been shown to vary as a function of individual differences in sensitivity, indexed by the perceived bitterness of 6-n-propylthiouracil (PROP). To determine if these variations in taste perception influence taste mixture interactions, groups of PROP super-, medium- and non-tasters assessed four binary taste mixtures: sweet-bitter [sucrose/quinine hydrochloride (QHCl)], sweet-sour (sucrose/citric acid), salty-bitter (NaCl/QHCl) and salty-sour (NaCl/citric acid). In each experiment, subjects received factorial combinations of four levels of each of two tastants and rated individual taste intensities and overall mixture intensity. For each taste quality, super-tasters typically gave higher ratings than either medium- or non-tasters, who tended not to differ. There were also group differences in the interactions of the mixtures' components. Super-tasters rated the overall intensity of the mixtures, most likely reflecting integration of the taste components, as greater than medium- and non-tasters, who again showed few differences. In sweet-bitter mixtures, non-tasters failed to show the suppression of sweetness intensity by the highest QHCl concentration that was evident in super- and medium-tasters. These data show that the perception of both tastes and binary taste mixture interactions varies as a function of PROP taster status, but that this may only be evident when three taster groups are clearly distinguished from one another.     

'Thermal taste' predicts higher responsiveness to chemical taste and flavor

Individual differences in taste perception have been explained in part by variations in peripheral innervation associated with the genetic ability to taste the bitter substances PTC and PROP. In the present study we report evidence of another source of individual differences that is independent of taste stimulus, taste quality, or gustatory nerve. Individuals who perceived taste from thermal stimulation alone (thermal taste) gave significantly higher taste ratings to chemical stimuli--often by a factor of >2:1--than did individuals who perceived no taste from thermal stimulation. This was true for all taste stimuli tested (sucrose, saccharin, sodium chloride, citric acid, quinine sulfate, MSG and PROP), for all three gustatory areas of the mouth (anterior tongue, posterior tongue and soft palate) and for whole-mouth stimulation. Moreover, the same individuals reported stronger sensations from the olfactory stimulus vanillin, particularly when it was sensed retronasally. The generality of the thermal-taster advantage and its extension to an olfactory stimulus suggests that it arises from individual differences in CNS processes that are involved in perception of both taste and flavor.     

CONSUMER PREFERENCE OF DULCE DE LECHE AMONG STUDENTS IN THE UNITED KINGDOM

Dulce de Leche is a dairy-based confectionary product virtually unknown outside Latin America. A 2⁴ factorial design was implemented to study the influence of sugar composition, type of neutralizer, cooking time and presence of vanilla essence on the preference of Dulce de Leche by UK university students. A fractional factorial pattern was used in sen'ing samples to assessors. Analysis of variance showed that the preferred levels were: 40% replacement of sucrose by glucose syrup, 100% sodium bicarbonate as neutralizer, and no vanilla essence. Cooking time did not significantly affect preference. Partial least squares regression was used to relate preference to sensory profile scores. The correlation was good for appearance and texture, not so for flavor and aftertaste. A mapping technique showed consumers to be uniformly grouped for appearance and texture, not so for flavor. Results from preference and general acceptability were encouraging in promoting this new dairy product in Great Britain.     

COMPARISON OF THE SENSORY PROPERTIES OF ULTRA-HIGH-TEMPERATURE (UHT) MILK FROM DIFFERENT COUNTRIES

Shelf-stable milk, also known as ultra-high-temperature (UHT) milk is the most common form of milk in many parts of the world. This study compared the differences in flavor and texture of 37 commercially available UHT and sterilized milk samples including whole, 2% reduced-fat and low-fat milk obtained from markets in seven countries: France ( n =  2), Italy ( n =  11), Japan ( n =  1), Korea ( n =  2), Peru ( n =  3), Thailand ( n =  13) and the U.S.A. ( n =  5). Five highly trained panelists used flavor and texture profiling to describe the sensory properties of each milk sample. Data were analyzed by principal component analysis and hierarchical cluster analysis. Higher levels of processed, chalky, brown and cooked flavor notes generally corresponded to lower levels of fresh dairy flavor characteristics. In general, samples did not vary consistently within a country. Fat content did not correlate with dairy fat flavor or with viscosity. This research suggests that companies' manufacturing processes for UHT milk may have more impact than country or fat content in determining sensory properties of UHT milk.

PRACTICAL APPLICATIONS

Sensory properties of UHT milk from different countries developed in this study could be used by the dairy industry to understand the similarities and differences of UHT milk characteristics from different regions and to modify UHT milk characteristics to meet consumers' criteria or expectation. The study suggests that manufacturers who want to improve quality of UHT milk by modify flavor and texture properties should focus on improvements to the manufacturing processes.     

Extrinsic information influences taste and flavor perception: A review from psychological and neuroimaging perspectives

The perception of taste and flavor can be greatly biased by extrinsic cues, or the information about a food that comes from outside of the food itself, such as package designs, brands, prices, and so on. In order to understand taste/flavor experiences in a broader context, it is necessary to consider factors other than the food/tastants themselves. This review aims to summarize some of the relevant findings from psychological and neuroimaging studies, focusing on depicting how extrinsic cues exert their effect on taste and flavor. Currently, the most frequently considered psychological mediator for the effects of extrinsic cues is expectation. Depending on the gap between expectation and taste/flavor experience, four major models predict outcomes of expectation effects: (1) assimilation, (2) generalized-negativity, (3) contrast, and (4) assimilation-contrast. Among them, the most influential is the assimilation model proposing that taste/flavor experiences are modified toward what one expects. Thus far, all the neuroimaging studies examining the influence of extrinsic cues have dealt with assimilation effects. They suggest that when extrinsic cues influence taste/flavor perception, cortical representations of taste/flavor are also modulated. Collectively neuroimaging findings partly answer questions arising from psychological aspects: the influence of extrinsic cues is not due to superficial response bias but to truly changed perception. These findings, albeit limited to assimilation effects, suggest that combined understanding from both psychological and neuroimaging studies would help deepen our understanding of the taste experience.     

Ability to taste 6-n-propylthiouracil and BMI in low-income preschool-aged children

Background: Sensitivity to the bitter compound 6‐n‐propylthiouracil (PROP) is genetically mediated. Sensitivity to PROP has been associated with weight status in both adults and children. Objective: To determine whether there is an association between PROP sensitivity and BMI in low‐income children of diverse race/ethnicity, among whom there is a high prevalence of obesity. Methods and Procedures: Eighty‐one preschool‐aged children attending Head Start tasted a solution of 560 μmol/l PROP and reported whether it tasted “like water” or “like something else”. Mothers reported child's race, age, maternal education, maternal weight and height, child's reluctance to sample new foods via the Food Neophobia Scale (FNS), and child's dietary intake using a food frequency questionnaire. Child weight and height were measured. BMI was calculated and for children, expressed in z‐scores. Regression analyses were used to evaluate the relationship between child's PROP taster status and BMI z‐score, testing covariates child's age, gender, race, maternal education and BMI, and child's FNS score. Children's dietary intake was compared by PROP taster status. Results: PROP tasters, compared with nontasters, had significantly higher BMI z‐scores (0.99 (s.d. 1.24) vs. 0.03 (1.12), P = 0.004) and had a significantly higher prevalence of overweight (31.8% vs. 5.6%, P = 0.025), but demonstrated no differences in reported dietary intake. The most parsimonious model predicting the child's BMI z‐score included only maternal BMI and the child's PROP taster status (R ² = 22.3%). Discussion: A genetically mediated ability to taste bitter may contribute to obesity risk in low‐income, preschool‐aged children.