Nutritional implications of genetic taste variation: the role of PROP sensitivity and other taste phenotypes

Test-retest reliability and normative data for "Seven-iTT", a test for the assessment of taste and oral trigeminal function

BACKGROUND

Assessment of taste and somatosensory perception in clinical practice lacks fast tests that are validated and reliable. Recently, a 12-item identification test for taste and oral trigeminal perception, and its shorter version, the Seven-iTT, was developed. The objectives of this study were to evaluate its test-retest reliability and establish normative data.

NEW METHOD

Two-hundred participants (120 women, 80 men) with a good sense of taste performed a whole-mouth identification test using 12 filter-paper strips impregnated with low and high concentrations of sweet, sour, salty, bitter, astringency, and spiciness. Fifty of them repeated the task, with a median interval of 122 days from the first visit. Test-retest reliability was determined using Spearman correlation and the Bland-Altman plot method.

RESULTS

There was a significant correlation in identification score between the first and the second session for both versions of the test (r ≥ 0.28; p ≤ 0.048). The Bland-Altman plot reflected a good congruence between the results of the two sessions. Additionally, frequencies of correct identification were consistent between sessions, with women outperforming men (p = 0.005). Hypogeusia was established at Seven-iTT score of 3 of less.

COMPARISON WITH EXISTING METHODS

The identification test combines taste and somatosensory perception, thus creating a more detailed diagnosis tool. Scores were correlated with self-rated taste perception.

CONCLUSION

The present results confirmed the applicability of Seven-iTT for a reliable, fast evaluation of taste and somatosensory perception in the general population, that can be extended to clinical practice.

The gustin gene variation at rs2274333 and PROP taster status affect dietary fat perception: a stepwise multiple regression model study

Gustin, a trophic factor for taste bud development, and its polymorphism at rs2274333 influence taste perception of 6-n-propylthiouracil (PROP) and fungiform papillae (FP) density. The PROP taster status affects dietary fat sensing and body composition. However, there is a paucity of research on the gustin genotype with dietary fat perception, PROP tasting ability, and body mass index (BMI). Thus, taste sensitivity to fat and bitterness was evaluated in 178 healthy individuals. The general labeled magnitude scale was used to determine suprathreshold taste intensity ratings, whereas the alternative forced choice approach was used to estimate the taste-sensing ability. The FP density was assessed by applying blue-colored food dye over the anterior region of the tongue. Restriction fragment length polymorphism was used to detect the genetic polymorphism (rs2274333) in the carbonic anhydrase VI (CA-VI) gene. Fisher's chi-square analysis showed that the CA-VI genotype and allelic frequencies significantly correlated (p<0.001) with the PROP taster status and BMI. Healthy individuals with AA genotypes of the CA-VI polymorphism and PROP super-tasters demonstrated stronger gustatory sensitivity for linoleic acid (LA) with greater FP density in comparison to individuals with AG/GG genotypes and other PROP taster groups. Stepwise forward multiple regression analysis indicates that BMI and PROP taster status significantly influence the LA sensing ability. The suprathreshold intensity rating for LA was also significantly impacted by PROP taster status and CA-VI genotypes, with a variation of 73.3%. Overall, our findings show a relationship between the taste papillae environment and the CA-VI genetic mutation at rs2274333, which influenced the gustatory preference for dietary fat and bitter taste.

Gene Methylation Affects Salivary Levels of the Taste Buds' Trophic Factor, Gustin Protein

The salivary protein, Gustin/carbonic anhydrase VI, has been described as a trophic factor responsible for the growth of taste buds. We found, in a genetically homogeneous population, that the polymorphism rs2274333 (A/G) of the Gustin gene is crucial for the full functionality of the protein and is associated with taste sensitivity. However, other studies have failed to find this evidence. Here, we verified if Gustin gene methylation can affect the salivary levels of the protein, also concerning the polymorphism rs2274333 and PROP bitter responsiveness. The Gustin gene methylation profiling and the quantification of the Gustin salivary levels were determined in sixty-six volunteers genotyped for the polymorphism rs2274333 (A/G) (Ser90Gly in the protein sequence). The fungiform papillae density was also determined. The results confirm our earlier observations by showing that AA genotypes had a greater density of fungiform taste papillae, whereas the GG genotypes showed a lower density. We also found variations in the protein levels in the three genotype groups and an inverse relationship between Gustin gene methylation and the salivary levels of the protein, mostly evident in AA and ST volunteers, i.e., in volunteers who would be carriers of the functional isoform of the protein. These findings could justify the conflicting data in the literature.

A new perspective on obesity: perception of fat taste and its relationship with obesity

BACKGROUND

Obesity, which results from a long-term positive energy balance, is affected by many factors, especially nutrition. The sensory properties of foods are associated with increased food intake through hedonic appetite. Taste perception, a component of flavor, is also responsible for increased consumption, through reward and hedonic mechanisms. Foods with high fat and energy content are among the foods that create the reward perception. The perception of fat taste, the primary taste that has recently entered the literature, may also be associated with increased food consumption and body weight. Therefore, in this review, the relationship between fat taste and obesity is examined, using the latest literature.

RESULTS

Different hypotheses have been proposed regarding the mechanism of the relationship between fat-taste perception and obesity, such as hedonic appetite, microbiota, decreased taste perception, and increased taste threshold level. In addition, some studies examining this relationship reported significant associations between the level of fat-taste perception and obesity, whereas others did not find a significant difference.

CONCLUSION

Considering the prevalence and contribution to obesity of Western-style nutrition, characterized by high amounts of fat and sugar consumption, elucidating this relationship may be an essential solution for preventing and treating obesity.

Food bioactive peptides: functionality beyond bitterness

Bitter taste is an aversive taste because it is unconsciously associated with toxic compounds. However, a considerable variability in bitter sensitivity exists in those who have the genetic polymorphism for bitter taste receptors (TAS2Rs). Besides the oral cavity, TAS2Rs are present in many body tissues, including the gastrointestinal tract; therefore, they are crucial players both in the gustatory/hedonic system and in the homeostatic system, triggering numerous biological responses, including adipogenesis, carcinogenesis, or immunity. Bitter-tasting compounds are widely distributed in plant and animal foods and belong to many chemical classes. In this study, the evidence was reviewed on bitter peptides, considering the food sources, their formation in food under different processing and storage conditions and in the gastrointestinal tract during digestion, as well as their biological activities. Bitterness associated with peptides is due to the presence of hydrophobic amino acids in the C-terminus. The current literature mainly explores the enzymes and hydrolysis conditions, with the aim of reducing the formation of bitter peptides in hydrolysate preparation or food. Few studies highlight the bioactivity (namely, antihypertensive, antidiabetic, antioxidant, or immunity boosting), besides the bitterness. However, encapsulation of bitter peptides has been tentatively used to develop antihypertensive and antidiabetic supplements. In the era of personalized nutrition and precision medicine, the evidence available suggests the opportunity to use bitter bioactive peptides as functional ingredients in food. Such types of food may modulate a plethora of physiological mechanisms by targeting TAS2Rs in the gastrointestinal tract, thus modulating appetite sensations or gastrointestinal motility and discomfort according to individual nutritional needs and goals. More studies are needed to optimize the technological strategies to target TAS2Rs by bitter bioactive peptides, improve their stability in food, and validate the biological efficacy through well-designed in vivo studies.

Responsiveness to warning sensations and anxiety-related psychological traits modulate individual differences in preference for vegetable foods with varied sensory properties

The innate aversion to warning sensations is an important barrier to the acceptance of vegetable food often characterized by bitter and sour tastes, and astringency. Large individual variations exist in preference for this food category. The present study aimed at exploring differences in demographics, anthropometrics, taste responsiveness, personality traits and attitudes in consumers differing in their preference for vegetable food with varied levels of warning sensations. A panel of Italian consumers (n = 718; 53.6% women, age 18-74 years) self-reported familiarity with, preference for and choice of vegetables with high and low levels of warning sensations. Two clusters were identified: High Warning-Vegetable Consumers (HWVC, n = 464) and Low-Warning Vegetable Consumers (LWVC, n = 254). HWVC showed higher familiarity with and preference for vegetables as a whole and higher choice of vegetables characterized by warning sensations than LWVC. HWVC were more represented by older and normal weight individuals as compared to LWVC. Differences among clusters in liking for and perception of a phenol-enriched plant-based food model specifically developed to induce different levels of bitterness, sourness and astringency were found. HWVC rated bitterness, sourness, and astringency lower and liking higher than LWVC. Scores in anxiety-related psychological traits were lower while attitudes to healthy and high-quality food choice were higher in HWVC than in LWVC. The results of the present study depicted a coherent interplay among several person-related dimensions in modulating preference for vegetable foods. Higher responsiveness to warning sensations, higher level of anxiety-related traits, lower importance assigned to food healthy/quality aspects and younger age all acted as barriers to exposure and acceptance of vegetable food and call for a multidimensional approach to promote the consumption of this food category.

Child-reported vegetable neophobia is associated with risk avoidance for distaste in children aged 4-15 years

Children who are food neophobic and/or picky eaters often refuse intake of especially fruits and vegetables, thereby narrowing their dietary variety and impairing the quality of their food intake. In this preregistered study, we investigated whether picky eating and food neophobia are related to bitter taste sensitivity (PROP taster status) and risk avoidance for distaste. A total of 367 children (201 girls; M age = 8.7 years, range: 4-15 years) participated in the study. They completed the vegetable neophobia subscale of the fruit and vegetable neophobia instrument (FVNI). A caregiver completed the child food rejection scale (CFRS), a parent-report measure of food neophobia and picky eating. Children's bitter taste sensitivity was measured with a PROP (6-n-propylthiouracil) taste strip, and the children completed a modified Children's Gambling Task (Candy Gambling Game) to measure risk avoidance for distaste. In this task, children could select cards from a risky deck (chance of winning two tasty cherry-flavoured jelly beans, but also the risk of getting a distasteful soap-flavoured jelly bean) or a safe deck (chance of winning one tasty jelly bean or no jelly bean). The results show that picky eating and food neophobia (either parent- or self-reported) are not related to PROP taster status. However, children who self-reported higher levels of vegetable neophobia showed less risky choice behaviour in the Candy Gambling Game, although this relationship was not found with parent-reported food neophobia. We conclude that risk avoidance for distaste, but not taste function, is associated with children's self-reported food rejection tendencies. To broaden the food repertoire of children high in food neophobia, it might be useful to reduce the perceived risk of distaste, when introducing a novel food or meal.

Bringing down barriers to children's healthy eating: a critical review of opportunities, within a complex food system

This narrative review revises the scientific evidence of recent years on healthy eating in children and adolescents, making sense of promising avenues of action, from a food system perspective. A conceptual framework is provided to better understand how eating habits of children and adolescents are shaped to identify key multisectoral approaches that should be implemented to promote healthier diets. The following influencing factors are discussed: individual factors (physiological and psychological factors, food preferences and food literacy competencies), factors within the personal and socio-cultural food environments, external food environments, and the supply chain. In each section, the main barriers to healthy eating are briefly discussed focussing on how to overcome them. Finally, a discussion with recommendations of actions is provided, anchored in scientific knowledge, and transferable to the general public, industry, and policymakers. We highlight that multidisciplinary approaches are not enough, a systems approach, with a truly holistic view, is needed. Apart from introducing systemic changes, a variety of interventions can be implemented at different levels to foster healthier diets in children through fostering healthier and more sustainable food environments, facilitating pleasurable sensory experiences, increasing their food literacy, and enhancing their agency by empowering them to make better food related decisions. Acknowledging children as unique individuals is required, through interpersonal interactions, as well as their role in their environments. Actions should aim to enable children and adolescents as active participants within sustainable food systems, to support healthier dietary behaviours that can be sustained throughout life, impacting health at a societal level.

CD36 genetic polymorphism and salivary cues are associated with oleic acid sensitivity and dietary fat intake

There is a lack of research on the combined effects of genetic variations (specifically CD36 SNPs-rs1761667 and rs1527483), dietary food habits (vegetarian or not), and the salivary environment on obesity and taste sensitivity, especially in the Indian population. The current study aims to better understand the relationship between impaired taste perception, fat consumption, higher BMI and obesity development by examining the combined association between CD36 SNPs, oleic acid (OA) detection threshold, and food habits among Indian participants. Furthermore, the relationship between oral fatty acid (FAs) sensitivity and taste physiology factors linked to inflammation and salivary proteins was considered. Participants with the minor allele (AA/AG) of CD36 (in both rs1527483 and rs1761667) consumed more fat, particularly saturated FAs (p = 0.0351). Salivary lipopolysaccharide, which causes inflammation, was significantly greater in non-vegetarians with a higher BMI (p < 0.05), and it exhibited a negative correlation (r = -0.232 and p < 0.05) with Ki67 gene expression, a marker for taste progenitor cells. A positive correlation (r = 0.474, p = 0.04) between TLR4 mRNA levels and the OA detection threshold was also observed. Participants with BMI > 25 kg/m2 had substantially higher TNF-α and IL-6 receptor mRNA expression levels, but there were no significant differences between the vegetarian and non-vegetarian groups. However, salivary CA-VI, which has a buffering capability on the oral environment, was lower in non-vegetarian adults with BMI >25. Thus, it was shown that non-vegetarians with overweight and obesity in India were in at-risk groups for the CD36 SNP (AA/AG at rs1761667 and rs1527483) and had higher levels of inflammatory markers, which exacerbated alterations in food behaviour and physiological changes, indicating their relevance in the development of obesity.

Consumer Liking of Turnip Cooked by Different Methods: The Influence of Sensory Profile and Consumer Bitter Taste Genotype

Brassica vegetables are bitter, predominantly because they contain bitter-tasting glucosinolates. Individuals with high bitter taste sensitivity are reported to have lower consumption of bitter vegetables. Studies reported that cooking methods can alter the sensory characteristics of vegetables, increasing acceptability. This study investigated consumer liking of turnip cooked by four methods (boiled-pureed, roasted, steamed-pureed and stir-fried) and related this to sensory characteristics. Additionally, this study examined the effect of the bitter taste genotype on taste perception and liking of the cooked turnip samples. Participants (n = 74) were recruited and the TAS2R38 genotype was measured. Liking, consumption intent, perception of bitterness and sweetness of turnip were evaluated. A sensory profile of the cooked turnip variants was also determined by a trained sensory panel. There were significant differences in the overall (p = 0.001) and taste (p = 0.002) liking between cooking methods. Turnip liking was increased when preparation led to sweeter taste profiles. The TAS2R38 genotype had a significant effect on bitter perception (p = 0.02) but did not significantly affect taste liking. In conclusion, the cooking method affected turnip liking, and the bitter perception in turnip was influenced by the TAS2R38 genotype. However, taste sensitivity did not predict turnip liking in this UK adult cohort.

A Supervised Learning Regression Method for the Analysis of the Taste Functions of Healthy Controls and Patients with Chemosensory Loss

In healthy humans, taste sensitivity varies widely, influencing food selection and nutritional status. Chemosensory loss has been associated with numerous pathological disorders and pharmacological interventions. Reliable psychophysical methods are crucial for analyzing the taste function during routine clinical assessment. However, in the daily clinical routine, they are often considered too time-consuming. We used a supervised learning (SL) regression method to analyze with high precision the overall taste statuses of healthy controls (HCs) and patients with chemosensory loss, and to characterize the combination of responses that would best predict the overall taste statuses of the subjects in the two groups. The random forest regressor model allowed us to achieve our objective. The analysis of the order of importance of each parameter and their impact on the prediction of the overall taste statuses of the subjects in the two groups showed that salty (low-concentration) and sour (high-concentration) stimuli specifically characterized healthy subjects, while bitter (high-concentration) and astringent (high-concentration) stimuli identified patients with chemosensory loss. Although the present results require confirmation in studies with larger samples, the identification of such distinctions should be of interest to the health system because they may justify the use of specific stimuli during the routine clinical assessments of taste function and thereby reduce time and cost commitments.

Association between Genetic Variation in the TAS2R38 Bitter Taste Receptor and Propylthiouracil Bitter Taste Thresholds among Adults Living in Japan Using the Modified 2AFC Procedure with the Quest Method

Individual taste sensitivity influences food preferences, nutritional control, and health, and differs greatly between individuals. The purpose of this study was to establish a method of measuring and quantifying an individual's taste sensitivity and to evaluate the relationship between taste variation and genetic polymorphisms in humans using agonist specificities of the bitter taste receptor gene, TAS2R38, with the bitter compound 6-n-propylthiouracil (PROP). We precisely detected the threshold of PROP bitter perception by conducting the modified two-alternative forced-choice (2AFC) procedure with the Bayesian staircase procedure of the QUEST method and examined genetic variation in TAS2R38 in a Japanese population. There were significant differences in PROP threshold between the three TAS2R38 genotype pairs for 79 subjects: PAV/PAV vs AVI/AVI, p < 0.001; PAV/AVI vs AVI/AVI, p < 0.001; and PAV/PAV vs PAV/AVI, p < 0.01. Our results quantified individual bitter perception as QUEST threshold values: the PROP bitter perception of individuals with the PAV/PAV or PAV/AVI genotypes was tens to fifty times more sensitive than that of an individual with the AVI/AVI genotype. Our analyses provide a basic model for the accurate estimation of taste thresholds using the modified 2AFC with the QUEST approach.

Regulator of G-Protein Signalling 9: A New Candidate Gene for Sweet Food Liking?

Genetics plays an important role in individual differences in food liking, which influences food choices and health. Sweet food liking is a complex trait and has been associated with increased body mass index (BMI) and related comorbidities. This genome-wide association study (GWAS) aimed to investigate the genetics of sweet food liking using two adult discovery cohorts (n = 1109, n = 373) and an independent replication cohort (n = 1073). In addition, we tested the association of our strongest result on parameters related to behaviour (food adventurousness (FA) and reward dependence (RD) and health status (BMI and blood glucose). The results demonstrate a novel strong association between the Regulator of G-Protein Signalling 9 (RGS9I) gene, strongest single nucleotide polymorphism (SNP) rs58931966 (p-value 7.05 × 10^-9 in the combined sample of discovery and replication), and sweet food liking, with the minor allele (A) being associated with a decreased sweet food liking. We also found that the A allele of the rs58931966 SNP was associated with decreased FA and RD, and increased BMI and blood glucose (p-values < 0.05). Differences were highlighted in sex-specific analysis on BMI and glucose. Our results highlight a novel genetic association with food liking and are indicative of genetic variation influencing the psychological-biological drivers of food preference. If confirmed in other studies, such genetic associations could allow a greater understanding of chronic disease management from both a habitual dietary intake and reward-related perspective.

Agronomical Practices and Management for Commercial Cultivation of Portulaca oleracea as a Crop: A Review

Soil is an essential resource, and its degradation is challenging modern agriculture, while its impact is expected to increase in the near future. One of the strategies to address this issue is to incorporate new alternative crops able to tolerate arduous conditions, as well as for the use of sustainable agricultural practices in order to recover and/or improve soil health. Additionally, the increasing market for new functional/healthy natural foods promotes the search for potential alternative crop species with promising bioactive compounds content. For this purpose, wild edible plants are a key option because they have already been consumed for hundreds of years in traditional gastronomy and there is well-established evidence of their health-promoting effects. Moreover, since they are not a cultivated species, they are able to grow under natural conditions without human intervention. Among them, common purslane is an interesting wild edible species and a good candidate for integration in commercial farming systems. With worldwide spread, it is able to tolerate drought, salinity and heat stress and is already used in traditional dishes, while it is highly appreciated for its high nutritional value due to its bioactive compound content, especially omega-3 fatty acids. In this review, we aim to present the breeding and cultivation practices of purslane, as well as the effects of abiotic stressors on yield and chemical composition of the edible parts. Finally, we present information that helps to optimize purslane cultivation and facilitate its management in degraded soils for their exploitation in the existing farming systems.

Bitter Taste Receptor TAS2R38 Genetic Variation (rs10246939), Dietary Nutrient Intake, and Bio-Clinical Parameters in Koreans

Differential bitterness perception associated with genetic polymorphism in the bitter taste receptor gene taste 2 receptor member 38 (TAS2R38) may influence an individual's food preferences, nutrition consumption, and eventually chronic nutrition-related disorders including cardiovascular disease. Therefore, the effect of genetic variations on nutritional intake and clinical markers needs to be elaborated for health and disease prevention. In this study, we conducted sex-stratified analysis to examine the association between genetic variant TAS2R38 rs10246939 A > G with daily nutritional intake, blood pressure, and lipid parameters in Korean adults (males = 1,311 and females = 2,191). We used the data from the Multi Rural Communities Cohort, Korean Genome and Epidemiology Study. Findings suggested that the genetic variant TAS2R38 rs10246939 was associated with dietary intake of micronutrients including calcium (adjusted p = 0.007), phosphorous (adjusted p = 0.016), potassium (adjusted p = 0.022), vitamin C (adjusted p = 0.009), and vitamin E (adjusted p = 0.005) in females. However, this genetic variant did not influence blood glucose, lipid profile parameters, and other blood pressure markers. These may suggest that this genetic variation is associated with nutritional intake, but its clinical effect was not found. More studies are needed to explore whether TAS2R38 genotype may be a potential predictive marker for the risk of metabolic diseases via modulation of dietary intake.

Automated identification of the genetic variants of TAS2R38 bitter taste receptor with supervised learning

Several studies were focused on the genetic ability to taste the bitter compound 6-n-propylthiouracil (PROP) to assess the inter-individual taste variability in humans, and its effect on food predilections, nutrition, and health. PROP taste sensitivity and that of other chemical molecules throughout the body are mediated by the bitter receptor TAS2R38, and their variability is significantly associated with TAS2R38 genetic variants. We recently automatically identified PROP phenotypes with high precision using Machine Learning (mL). Here we have used Supervised Learning (SL) algorithms to automatically identify TAS2R38 genotypes by using the biological features of eighty-four participants. The catBoost algorithm was the best-suited model for the automatic discrimination of the genotypes. It allowed us to automatically predict the identification of genotypes and precisely define the effectiveness and impact of each feature. The ratings of perceived intensity for PROP solutions (0.32 and 0.032 mM) and medium taster (MT) category were the most important features in training the model and understanding the difference between genotypes. Our findings suggest that SL may represent a trustworthy and objective tool for identifying TAS2R38 variants which, reducing the costs and times of molecular analysis, can find wide application in taste physiology and medicine studies.

Sensitivity to Sweet and Salty Tastes in Children and Adolescents with Type 1 Diabetes

Taste function impairment is observed in people with type 1 diabetes (T1D). It is most often related to sweet taste. It is associated with such factors as diabetic neuropathy, smoking, age, duration of the disease and a rigorous diet that eliminates easily digestible carbohydrates. The aim of the study was to compare sensitivity to sweet and salty tastes between healthy children and adolescents and children and adolescents with T1D. The study group consisted of children with T1D (n = 35), with at least 5 years of disease history, while the group of healthy children included 46 individuals selected in terms of age, gender and BMI. A study concerning the perception of sweet and salty taste was carried out with the use of the specific gustometry method (examining the recognition and assessment of the intensity of taste sensations, performing a hedonic assessment). Children and adolescents from both groups had trouble recognising tastes. Children and adolescents with T1D were more likely to recognise sweet taste correctly even at its lower concentrations compared to healthy individuals (p = 0.04). Salty taste was significantly more often correctly identified by healthy children compared to T1D patients (p = 0.01). Children and adolescents with T1D reported a stronger intensity of perceived tastes than healthy ones. No significant differences in perceived pleasure were noted at lower sucrose concentrations in any group. The intensity score was higher in individuals with T1D at higher sucrose concentrations. No significant differences occurred in the assessment of salty taste intensity. The hedonic scoring of solutions with higher concentrations of sweet taste was higher in people with T1D than in healthy ones, while salty taste was assessed neutrally. Children and adolescents with T1D were demonstrated to have some taste recognition disorders. Therefore, monitoring taste function in pediatric diabetic clinical practice seems relevant, as it may be associated with important implications for the intake of a particular type of food and for the development of eating habits and preferences.

Associations between Sweet Taste Sensitivity and Polymorphisms (SNPs) in the TAS1R2 and TAS1R3 Genes, Gender, PROP Taster Status, and Density of Fungiform Papillae in a Genetically Homogeneous Sardinian Cohort

Individual differences in sweet taste sensitivity can affect dietary preferences as well as nutritional status. Despite the lack of consensus, it is believed that sweet taste is impacted by genetic and environmental variables. Here we determined the effect of well-established factors influencing the general taste variability, such as gender and fungiform papillae density, specific genetic variants (SNPs of TAS1R2 and TAS1R3 receptors genes), and non-specific genetic factors (PROP phenotype and genotype), on the threshold and suprathreshold sweet taste sensitivity. Suprathreshold measurements showed that the sweet taste response increased in a dose-dependent manner, and this was related to PROP phenotype, gender, rs35874116 SNP in the TAS1R2 gene, and rs307355 SNP in the TAS1R3 gene. The threshold values and density of fungiform papillae exhibited a strong correlation, and both varied according to PROP phenotype. Our data confirm the role of PROP taste status in the sweet perception related to fungiform papilla density, show a higher sweet sensitivity in females who had lower BMI than males, and demonstrate for the first time the involvement of the rs35874116 SNP of TAS1R2 in the sweet taste sensitivity of normal weight subjects with body mass index (BMI) ranging from 20.2 to 24.8 kg/m². These results may have an important impact on nutrition and health mostly in subjects with low taste ability for sweets and thus with high vulnerability to developing obesity or metabolic disease.

Emotional responses to taste and smell stimuli: Self-reports, physiological measures, and a potential role for individual and genetic factors

Taste and olfaction elicit conscious feelings by direct connection with the neural circuits of emotions that affects physiological responses in the body (e.g., heart rate and skin conductance). While sensory attributes are strong determinants of food liking, other factors such as emotional reactions to foods may be better predictors of consumer choices even for products that are equally-liked. Thus, important insights can be gained for understanding the full spectrum of emotional reactions to foods that inform the activities of product developers and marketers, eating psychologist and nutritionists, and policy makers. Today, self-reported questionnaires and physiological measures are the most common tools applied to study variations in emotional perception. The present review discusses these methodological approaches, underlining their different strengths and weaknesses. We also discuss a small, emerging literature suggesting that individual differences and genetic variations in taste and smell perception, like the genetic ability to perceive the bitter compound PROP, may also play a role in emotional reactions to aromas and foods.

The Effects of Cranberry Polyphenol Extract (CPE) Supplementation on Astringency and Flavor Perception as a Function of PROP Taster Status and Other Individual Factors

This study investigated whether PROP (6-n-propylthiouracil) taster status and other individual factors (gender, ethnicity, BMI, and age) are markers of variation in perceptions of astringency and other flavor attributes. Participants (n = 125) evaluated cranberry juice cocktail samples (CJC) supplemented with cranberry-derived polyphenol extract (CPE, added at 0, 0.3, 0.5 and 0.75 g/L), as well as control samples, unsweetened cranberry juice (CJ) and an aqueous solution of 0.75 g/L CPE. Subjects evaluated samples for key sensory attributes and overall liking using a 15 cm line scale. The data were analyzed using ANCOVA and machine learning tools (regression trees and random forest modeling) to examine if the latter approach would extract more meaningful insights about the roles of personal factors in sensory perceptions of cranberry-derived stimuli. ANCOVA revealed robust stimulus effects, but no effect of PROP taster status on astringency perception was observed. Several effects of PROP×gender, ethnicity, and other factors were observed on other sensory attributes and liking. ANCOVA and machine learning tools yielded similar findings, but regression trees provided a more visualized framework. These data show that PROP taster status has a limited role in astringency perception in complex samples and that other personal factors deserve greater focus in future research on astringency perception.

Association of phenylthiocarbamide perception with anthropometric variables and intake and liking for bitter vegetables

Phenylthiocarbamide (PTC) sensitivity, a sensory trait mediated by the bitter taste receptor 38 (TAS2R38), has been described as a promising biomarker of health status or disease risk. The aim of this cross-sectional study was to evaluate the influence of PTC phenotypes on (1) individual anthropometric and clinical history variables; (2) other basic taste recognition thresholds (RTs), and (3) the hedonic perception and habitual intake of Brassicaceae vegetables in a young adult population (18.9 ± 1.7 years old). The PTC phenotype was determined by the quantitative measure of the PTC recognition threshold (non-tasters, 24.1%; tasters, 52.3%; and super tasters, 23.6%). No significant differences in smoking habits, oral and nasal disorders, family antecedents of diseases related to metabolic syndrome, and Brassicaceae vegetable hedonic perception and consumption were found between the PTC phenotype groups. The average BMI of super-taster females and males was significantly lower compared to non-tasters. In addition, the PTC taster status was a predictor of lower scores for other basic taste RTs. Overall, the defined PTC super-taster cohort could be differentiated from the non-tasters by variables related to weight control such as BMI and sucrose RT.

Assessment of the Volatile Profiles and Identification of Differentiating Aromas of Wild Undervalued Plants

Wild edible plants have played an important role in traditional diets, including the Mediterranean diet. Many of these plants have acquired an undervalued status, since they are under-appreciated in terms of their nutritional, organoleptic qualities, or their seasonality. However, some of these species are still used in local gastronomy for their aromatic and taste characteristics. This study has investigated the quantitative and qualitative aromatic characteristics of seven undervalued wild plants that determine their organoleptic characteristics. Volatiles of the fresh leaves of each species have been determined by head-space solid-phase microextraction, a sensitive and solvent-free technique, coupled with gas chromatography and mass spectrometry. A total of 37 compounds with remarkable quantitative and qualitative differences were identified. In general, benzenoids and monoterpenoids were the most abundant groups, while branched unsaturated hydrocarbons, fatty alcohols, and sesquiterpenoids were the minor groups. Benzyl nitrile, benzyl isothiocyanate, p-cymene, and 2-hexenal were the main individual volatiles, while benzyl alcohol, eugenol, and α-copaene were the differentiating aromas. The results display that the undervalued species studied could be a suitable choice to include as new environmentally friendly crops, providing a double benefit to producers, because they are a possible way to achieve sustainable production systems, and they are an alternative for consumers, because these plants provide flavors that have high organoleptic qualities.

The Number of Fungiform Papillae, Taste Sensitivity and Smell Functions of Children Aged 11–15

Differences in the ability to identify and perceive tastes and smells might influence food consumption and, ultimately, chronic nutrition-related conditions such as overweightness and obesity. This study aimed to investigate the associations between taste sensitivity and odour function, anthropometry, and quantity of fungiform papillae in children at age 11–15. Taste strips (4 base tastes), U-Sniff sticks (12 selected smells), and a filter paper strip impregnated with 6-n-propylthiouracil (PROP) were used. The photographic method was used to estimate the number of fungiform papillae (FP) on the tongue. The results showed that the quantity of FP was not related to anthropometry or gender. The taste test total scores were higher for girls, for whom the median score was 14 (12.0–15.0), than for boys, for whom the median score was 12 (9.0–13.0). Of the children, 13.9% had some difficulty in identifying odours. The Mann–Whitney U test showed that children who were most sensitive to bitter taste had more FP (p = 0.0001). The median score for this group (score = 4) was 34.0 (27.0–37.0). For those who had some problems with correctly assessing all bitter taste strips (score = 0–3), the median score was 24.0 (20.0–31.0). Higher numbers of FP were also observed in tasters, that is, people sensitive to PROP, than in nontasters. Only some measures of the taste function correlated with each other, but not very significantly. We concluded that there are multiple perceptual phases of taste, with no single measure able to entirely represent the sense of taste.

Application of a salt substitute in bitter taste suppression and toward better acceptance of cruciferous vegetables in diet

The addition of table salt has been reported to enable better acceptance when consuming the least preferred vegetables belonging to the Cruciferae family. Considering the adverse effect of excessive table salt intake on incidence of hypertension and cardiovascular diseases, it is essential to explore an alternative healthier option for better acceptance and to encourage consumption of these vegetables. In this study, 261 adult participants were evaluated for their preferences toward basic tastes and food as well as sensory evaluation of a meal prepared from cruciferous vegetables with the addition of two different salts, sodium chloride and salt substitute containing a blend of potassium and sodium salts. A general questionnaire was used to assess taste and food preferences, while the Cruciferous Vegetable Food Frequency Questionnaire (CVFFQ) was used for vegetable intake assessment. The Labeled Magnitude Scale (LMS), Just About Right (JAR) scale, and several hedonic scales were used to determine taster status and sensory evaluation. The results show that a low concentration of the salt substitute did not impact bitterness suppression but did result in higher preference of the cruciferous vegetable meal. Although, subjects self-reported to have salty taste preferences were more sensitive to bitter taste, they did not perceive samples as less salty and less acceptable than subjects with lower sensitivity. The results show the necessity for further examination of the effectiveness of different concentrations of the assessed salt substitute in suppressing perceived bitterness of cruciferous vegetables and regarding their overall acceptance for inclusion in diets.

Associations between Taste and Smell Sensitivity, Preference and Quality of Life in Healthy Aging-The NutriAct Family Study Examinations (NFSE) Cohort

Taste and smell function decline with age, with robust impairment in the very old. Much less is known about taste and smell function in young and middle aged. We investigated taste and smell sensitivity via thresholds in a sub-sample of the NutriAct Family Study (NFS), the NFS Examinations cohort (NFSE; N = 251, age M = 62.5 years). We examined different aspects relating to taste and smell function: the degree to which taste and smell sensitivity relate to another and to taste and smell preferences, the role of gender and age, as well as effects on Quality of Life (QoL). Taste thresholds were highly correlated, but no correlation was observed between taste and smell thresholds and between thresholds and preference. Women were more sensitive for both taste and smell than men. We found no effect of age on sensitivity and no effect of sensitivity on QoL. All null findings were complemented by Bayesian statistics. Together our results indicate the independence of taste and smell despite their overlap during sensorial experiences. We found no evidence for age-related sensory decline, which could be due to our sample’s characteristics of non-clinical volunteers with good dental health and 93% non-smokers.

Are taste variations associated with the liking of sweetened and unsweetened coffee?

OBJECTIVE

In this study, we evaluated the influence of taste phenotypes and genotypes on the hedonics of sweetened and unsweetened coffee.

METHODS

Liking of espresso coffee from food questionnaire and of a ready-to-drink unsweetened coffee beverage was measured using a 9-point hedonic scale in 1551 Italian individuals. Perception and liking for different bitter and sweet compounds were also collected. Genotyping of selected Single Nucleotide Polymorphisms (SNPs) in five taste genes (TAS1R3, GNAT3, TAS2R14, TAS2R19, TAS2R38) was performed. Linear and logistic regression models, including sex and gender as covariates, were used to test the relationship of taste phenotypes and selected SNPs with coffee liking.

RESULTS

We found that increased caffeine bitterness perception was associated with an increasing liking for sweetened coffee (p-value = 0.018) and decreased liking of unsweetened coffee (p-value = 0.034). The liking of unsweetened coffee beverage was also negatively associated with sweet intensity perception (p-value = 0.03). Analysis of SNPs in taste-related genes showed that rs6467192 G allele (intron 4 variant) in GNAT3 sweet taste gene was associated with higher liking of sweetened coffee (p-value = 0.002) and lower liking of unsweetened coffee (p-value = 0.01). An association also emerged between unsweetened coffee and SNPs in bitter receptor genes, with rs2597979 in TAS2R14 gene associated with liking of unsweetened coffee (p-value = 0.004) and rs10772420 in TAS2R19 gene associated with liking of both unsweetened espresso coffee and coffee beverage (p-value = 0.04 and p-value = 0.03, respectively).

CONCLUSION

These findings suggested that individual preference for sweetened and unsweetened coffee may be influenced by both phenotypic and nucleotide variations in bitter and sweet taste sensitivity.

Altered Taste Function in Young Individuals With Type 1 Diabetes

Past studies on altered taste function in individuals with type 1 diabetes have yielded inconsistent results. We therefore evaluated taste recognition and possible association with personal and diseases characteristics in young individuals with type 1 diabetes and healthy controls. Taste recognition and intensity for 6-n-propylthiouracil (PROP), quinine, citric acid, sucrose, and sodium chloride were assessed using a filter paper method in 276 participants with type 1 diabetes and 147 healthy controls. Personal and clinical data were recorded for all participants during a baseline visit. Regression analysis was adjusted for sex, age, and standardized BMI. Overall, 47% of participants with type 1 diabetes vs. 63.5% of healthy controls recognized all tastes (p = 0.006). Moreover, a lower capacity for recognizing the bitter taste of PROP and the sour taste of citric acid was found in participants with type 1 diabetes compared to healthy controls (p = 0.014 and p = 0.003, respectively). While no significant effect of glycemic control on taste recognition was found, an association with lower age at onset emerged. Our findings suggest an impaired taste perception in individuals with type 1 diabetes, possibly linked to age at onset.

Effect of cross-cultural differences on thickness, firmness and sweetness sensitivity

Sensitivity of the somatosensory system may be influenced by multiple physiological parameters. Variations in oral physiology can arise from cross-cultural differences which may potentially affect sensory sensitivity. The aim of this case study was to quantify texture and taste sensitivity in Dutch (Caucasian) and Chinese (Asian) adults living in the Netherlands. Eighty-five healthy subjects were recruited including 44 Dutch (Caucasian) adults (29 females, 22.8 ± 2.3 yrs) and 41 Chinese (Asian) adults (30 females, 24.5 ± 2.1 yrs) living in the Netherlands for less than 1 year. Three sets of stimuli were used to quantify sensitivity of thickness (maltodextrin solutions differing in viscosity), firmness (agar gels differing in fracture stress) and sweetness (sucrose solutions differing in concentration). The 2-Alternative Forced Choice (2-AFC) ascending staircase method was used to determine texture and taste sensitivity. Unstimulated and stimulated saliva flow rate, fungiform papillae density (FPD), lingual tactile threshold and PROP taster status were determined and are referred to as physiological and sensory consumer characteristics. No significant differences were observed between Chinese and Dutch adults for thickness (Dutch 2.60 mPas, Chinese 2.19 mPas), firmness (Dutch 10.5 kPa, Chinese 10.3 kPa) and sweetness sensitivity (Dutch 0.012 g/mL, Chinese 0.017 g/mL). No significant differences were observed between Chinese and Dutch adults for saliva flow rate, lingual tactile threshold and PROP taster status. The relationships between the three sensory sensitivities (thickness, firmness, sweetness) and five physiological and sensory consumer characteristics (unstimulated and stimulated saliva flow rate, FPD, lingual tactile threshold, PROP taster status) were analyzed. Only one out of 15 relationships, firmness sensitivity and FPD, was significantly and weakly related suggesting that inter-individual variation in these consumer characteristics is almost unrelated to sensory sensitivity. We conclude that in this case study thickness, firmness and sweetness sensitivities do not differ between Dutch and Chinese adults living in the Netherlands. Saliva flow rate, fungiform papillae density, lingual tactile threshold and PROP taster status do not explain inter-individual variation in sensory sensitivity between these consumers.

Taste of Fat and Obesity: Different Hypotheses and Our Point of View

Obesity results from a temporary or prolonged positive energy balance due to an alteration in the homeostatic feedback of energy balance. Food, with its discriminative and hedonic qualities, is a key element of reward-based energy intake. An alteration in the brain reward system for highly palatable energy-rich foods, comprised of fat and carbohydrates, could be one of the main factors involved in the development of obesity by increasing the attractiveness and consumption of fat-rich foods. This would induce, in turn, a decrease in the taste of fat. A better understanding of the altered reward system in obesity may open the door to a new era for the diagnosis, management and treatment of this disease.

Re-evaluating how sweet-liking and PROP-tasting are related

Past research has identified distinct phenotypic differences in responses to sweet taste, although the origins of these differences remain unclear. One possibility is that these individual differences in sweet-liking are a manifestation of the more widely known differences in sensitivity to the bitter tastant 6-n-propylthiouracil (PROP), which has been related to wider differences in food liking and preference. However, previous studies exploring the relationship between sweet-liking and PROP-tasting have had mixed outcomes. This is possibly due to older studies using a more simplistic dichotic characterisation of sweet likers, whereas recent research suggests three sweet-liking phenotypes (extreme sweet likers, ESL; moderate sweet likers, MSL; and sweet dislikers, SD). To re-assess how sweet-liking and PROP tasting are inter-related, 236 volunteers evaluated their liking for 1.0 M sucrose and the intensity of three concentrations of each NaCl and PROP. Using three different methods for classifying PROP taster status, our analysis confirmed that all three sweet-liking phenotypes were represented in all three PROP taster groups (super-tasters, ST; medium tasters, MT; and non-tasters, NT), but relatively few ESL were classified as ST, or SD as NT. Overall, these data suggest that while PROP tasting and sweet-liking are not causally related, the SD phenotype may partly be explained by a broader tendency for anhedonia.

Automated Classification of 6-n-Propylthiouracil Taster Status with Machine Learning

Several studies have used taste sensitivity to 6-n-propylthiouracil (PROP) to evaluate interindividual taste variability and its impact on food preferences, nutrition, and health. We used a supervised learning (SL) approach for the automatic identification of the PROP taster categories (super taster (ST); medium taster (MT); and non-taster (NT)) of 84 subjects (aged 18-40 years). Biological features determined from subjects were included for the training system. Results showed that SL enables the automatic identification of objective PROP taster status, with high precision (97%). The biological features were classified in order of importance in facilitating learning and as prediction factors. The ratings of perceived taste intensity for PROP paper disks (50 mM) and PROP solution (3.2 mM), along with fungiform papilla density, were the most important features, and high estimated values pushed toward ST prediction, while low values leaned toward NT prediction. Furthermore, TAS2R38 genotypes were significant features (AVI/AVI, PAV/PAV, and PAV/AVI to classify NTs, STs, and MTs, respectively). These results, in showing that the SL approach enables an automatic, immediate, scalable, and high-precision classification of PROP taster status, suggest that it may represent an objective and reliable tool in taste physiology studies, with applications ranging from basic science and medicine to food sciences.

Relationships between Intensity and Liking for Chemosensory Stimuli in Food Models: A Large-Scale Consumer Segmentation

This study, which was conducted as part of the Italian Taste project, was aimed at exploring the relationship between actual liking and sensory perception in four food models. Each food model was spiked with four levels of prototypical tastant (i.e., citric acid, sucrose, sodium chloride, capsaicin) to elicit a target sensation (TS) at an increasing perceived intensity. Participants (N = 2258; 59% women, aged 18-60) provided demographic information, a stated liking for 40 different foods/beverages, and their responsiveness to tastants in water. A food-specific Pearson's coefficient was calculated individually to estimate the relationship between actual liking and TS responsiveness. Considering the relationship magnitude, consumers were grouped into four food-specific clusters, depending on whether they showed a strong negative (SNC), a weak negative (WNC), a weak positive (WPC), or a strong positive correlation (SPC). Overall, the degree of liking raised in parallel with sweetness responsiveness, fell as sourness and pungency perception increased, and showed an inverted U-shape relationship with saltiness. The SNC clusters generally perceived TSs at higher intensities, except for sourness. Clusters were validated by associating the level of stated liking towards food/beverages; however, some unexpected indications emerged: adding sugar to coffee or preferring spicy foods differentiated those presenting positive correlations from those showing negative correlations. Our findings constitute a step towards a more comprehensive understanding of food preferences.

Perceived acceptability of partial enteral nutrition (PEN) using oral nutritional supplement drinks in adolescent and adult Crohn's disease outpatients: A feasibility study

BACKGROUND AND AIMS

Studies, mainly in Japanese cohorts, have shown that partial enteral nutrition (PEN) including oral nutritional supplement (ONS) drinks can prolong disease remission and increase drug effectiveness in Crohn's disease (CD). Acceptability is a key feasibility parameter to determine whether PEN is a viable treatment option in UK CD patients. We report the results of a single centre cross-sectional feasibility study carried out to investigate perceived acceptability of PEN using ONS drinks and whether ONS preference varies with sex, nutritional status or phenylthiocarbamide (PTC) sensitivity.

METHODS

Patients with a confirmed CD diagnosis were recruited using convenience sampling from an adult and adolescent gastroenterology outpatient clinic over 3 years. Blind taste testing of 5 polymeric ONS drinks were conducted using a validated 9-point hedonic rating scale followed by completion of an acceptability questionnaire based on the preferred ONS drink. A subset of patients took home the preferred ONS drink for a 7-day ONS study.

RESULTS

105 CD patients (55 males), aged 34.9 (±15.4) years were recruited and 28 patients completed the 7-day ONS study. Overall impression scores did not significantly vary with nutritional status, sex, BMI, handgrip strength (HGS), mid-upper arm circumference (MUAC) or PTC sensitivity. Ensure plus milkshake™ rated highest for overall impression (6.5, p=<0.0001) and all other organoleptic properties (p < 0.0001). The main perceived benefits of using ONS drinks as PEN related to assurance of nutrient intake (89%), convenience (86%), and improvement of gut symptoms (85%). The main perceived barriers related to reduction in pleasure from eating and drinking (56%), struggling with drink storage (54%) having less energy and feeling more tired than if eating 3 solid meals daily (52%). 65% of patients would consider using ONS drinks as PEN as a maintenance treatment option. 81% of patients felt confident-very confident about consuming ONS drinks daily as PEN for three months but this dropped to 64% and 37% at 6 and 12 months, respectively. There was a significant drop in perceived ease of use of ONS drinks as PEN after the 7-day ONS study (P = 0.01).

CONCLUSION

Use of ONS drinks as PEN have high perceived benefits and appear to be a feasible option for short-term use of 3-6 months in CD patients. However, confidence in long-term use of ONS drinks as PEN is low mainly due to the perceived social impact. Future studies should assess longer trial periods and volume of ONS drinks to increase the validity of these findings.

Political taste: Exploring how perception of bitter substances may reveal risk tolerance and political preferences

Risk is endemic to the political arena and influences citizen engagement. We explore this connection by suggesting that risk-taking may be biologically instantiated in sensory systems. With specific attention to gender and gender identity, we investigate the connections between self-reported bitter taste reception, risk tolerance, and both of their associations with political participation. In three U.S. samples collected in 2019 and 2020, participants were asked to rate their preferences from lists of foods as well as whether they detected the taste of the substance N-Propylthiouracil (PROP) and, if so, the strength of the taste. In this registered report, we find that self-reported bitter taste preference, but not PROP detection, is positively associated with higher levels of risk tolerance as well as political participation. The pattern with gender and gender identity is mixed across our samples, but interestingly, we find that sex-atypical gender identity positively predicts political participation.

Characterization of sensory perceptions elicited by white wine spiked with different aroma, taste and mouth-feel active molecules

The present work was aimed at understanding the sensory responses induced by dry white wine modified with increasing concentrations of different sensory active molecules. The tasting panel was composed by 34 trained subjects characterized according to gender, smoking habits, 6-n-propylthiouracil (PROP) taster status, and sensitivity to tartaric acid, tannic acid and sucrose. Additional taste/mouthfeel responsiveness was evaluated in a basal white wine added of tartaric acid, tannic acid and sucrose. The addition of a fruity odorant mixture to the base white wine enabled the assessment of orthonasal aroma and taste intensities (sweetness, sourness, saltiness). The diversity of taste/mouthfeel responsiveness in water or wine enabled to group individuals as high or low sensitives. Likewise, the tasting panel showed two groups responding differently to aroma and flavor. Both high and low aroma sensitivity individuals showed equal (p>0.05) and congruent response to in-mouth sweet flavor perception. Moreover, the high smell sensitive group was less sensitive to sourness and saltiness than the low smell sensitives for the spiked wines across all flavor concentrations. Differences in PROP taster status and sensitivity to other tastants in water solutions were not correlated with the taste/mouthfeel perceptions in wine. The individuals most sensitive to sucrose in wine taste showed higher response to the fruity aroma. In conclusion, taste, mouthfeel and flavor perceptions showed a high variability among individuals evidencing the advantage of grouping tasters with different chemosensory sensitivities to understand cross-modal sensory interactions.

The Influence of Common Noncommunicable Diseases on Chemosensory Perception and Clinical Implications in Children and Adolescents

An increased incidence of noninfectious chronic diseases, such as obesity, diabetes, and allergies, has been noted in the last century, especially in the last 2 to 3 generations. Evidence suggested that the interrelation among these chronic conditions in pediatric age (e.g., children and adolescents aged 4-16 y) is complex and still unknown, reinforcing the interest of pediatricians in these diseases. Of interest is the need to better understand the link between these pathologies and sensory perception, since the chemical senses of taste and smell, together with chemesthesis, are reported to have a role in food choices and may provide a novel target for intervention in the treatment of these pathologies. This review aims to explore the current evidence on the link between these chronic conditions and chemosensory perception (i.e., taste and smell). In addition, the putative role that chemosensory perception may have on food choices and eating behavior of children and adolescents affected by these diseases are highlighted. Furthermore, the review addresses the unexplored issues that need to be investigated in this area. The literature data search suggested that no clear relation between taste and smell perception and the aforementioned diseases in young population yet exists. However, some possible trends have been highlighted in the adult population, in whom the duration of disease might have affected the relation. There is a need for further, high-quality, hypothesis-led research, with robust measures of taste and smell functions as the primary outcomes, to strengthen or deny this evidence.

Taste receptor polymorphisms and longevity: a systematic review and meta-analysis

Bitter taste receptors (TAS2R) are involved in a variety of non-tasting physiological processes, including immune-inflammatory ones. Therefore, their genetic variations might influence various traits. In particular, in different populations of South Italy (Calabria, Cilento, and Sardinia), polymorphisms of TAS2R16 and TAS238 have been analysed in association with longevity with inconsistent results. A meta-analytic approach to quantitatively synthesize the possible effect of the previous variants and, possibly, to reconcile the inconsistencies has been used in the present paper. TAS2R38 variants in the Cilento population were also analysed for their possible association with longevity and the obtained data have been included in the relative meta-analysis. In population from Cilento no association was found between TAS2R38 and longevity, and no association was observed as well, performing the meta-analysis with data of the other studies. Concerning TAS2R16 gene, instead, the genotype associated with longevity in the Calabria population maintained its significance in the meta-analysis with data from Cilento population, that, alone, were not significant in the previously published study. In conclusion, our results suggest that TAS2R16 genotype variant is associated with longevity in South Italy.

High-Throughput Quantitation of Key Cocoa Tastants by Means of Ultra-High-Performance Liquid Chromatography Tandem Mass Spectrometry and Application to a Global Sample Set

Historically often described as the food of gods, cocoa-based products exhibit a pleasant aroma as well as a desirable astringent, bitter, and sour taste, which results in a high consumer preference. The key taste components of cocoa were identified and characterized by combining sensory analysis, fractionation, and structure elucidation. Cocoa astringency is driven by N-phenylpropenoyl-l-amino acids, polyphenol glycosides, and flavan-3-ols, while the latter compound class also contributes to bitterness. The key principle for cocoa bitterness was shown to be the combination of alkaloids and 2,5-diketopiperazines. To understand the influence of plant genetics, breeding, and processing on the sensory profile of cocoa products, high-throughput sensometabolite quantitation must be performed throughout all of these steps. In this work, we present a rapid, sensitive, and robust quantitation method on a single ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) platform, requiring minimal workup for any sample type from farm to fork. This method was applied to a global set of 75 cocoa bean samples from all over the world before and after using a uniform roasting protocol. Within this world map, geographical origin did not predetermine cocoa taste profiles, whereas simulated processing by roasting was confirmed to be crucial in profile development. This method will open avenues for further studies to ultimately enable chocolate producers to control and optimize the taste properties of products as well as to monitor raw material selection and processing.

Do Gut Microbes Taste?

Gut microbiota has emerged as a major metabolically active organ with critical functions in both health and disease. The trillions of microorganisms hosted by the gastrointestinal tract are involved in numerous physiological and metabolic processes including modulation of appetite and regulation of energy in the host spanning from periphery to the brain. Indeed, bacteria and their metabolic byproducts are working in concert with the host chemosensory signaling pathways to affect both short- and long-term ingestive behavior. Sensing of nutrients and taste by specialized G protein-coupled receptor cells is important in transmitting food-related signals, optimizing nutrition as well as in prevention and treatment of several diseases, notably obesity, diabetes and associated metabolic disorders. Further, bacteria metabolites interact with specialized receptors cells expressed by gut epithelium leading to taste and appetite response changes to nutrients. This review describes recent advances on the role of gut bacteria in taste perception and functions. It further discusses how intestinal dysbiosis characteristic of several pathological conditions may alter and modulate taste preference and food consumption via changes in taste receptor expression.

Taste perception and expression in stomach of bitter taste receptor tas2r38 in obese and lean subjects

Differences in taste perception have been related to eating behavior, nutritional status, and diseases. Recently, taste receptors have been identified in several extra-oral tissues, such as the gastrointestinal tract, where they seem to influence processes like digestion, sense of satiety as well as energy balance and intraluminal changes occurring in obesity. Our study aims to analyze differences in taste perception among 42 obese patients (OB) and 41 normal-weight subjects (LEAN). Polymorphisms in the gene codifying for the bitter taste receptor TAS2R38 and its expression on the surface of the gastric mucosa were tested and compared among OB and LEAN. Taste intensity of PROP (6-n-propylthiouracil), quinine, sucrose, citric acid and NaCl were measured on a labeled magnitude scale. DNA from peripheral whole blood was extracted and three polymorphisms in the TAS2R38 gene (rs713598, rs1726866, rs10246939) analyzed. Gastric biopsies were collected during bariatric surgery in OB and during endoscopy in LEAN. RNA was extracted and TAS2R38 gene expression assessed by RT-Real-Time qPCR. Anamnestic and anthropometric data were recorded in all participants during baseline visits. Logistic regression analysis showed that OB perceives sweet (sucrose) and bitter (PROP or 6-n-propylthiouracil) taste more intensely than LEAN (p-value = 0.02 and p-value = 0.005, respectively). While polymorphisms in TAS2R38 gene did not differ among OB and LEAN, we observed a significant increase of TAS2R38 mRNA levels in the stomach of OB compared to LEAN (p = 0.01). Our results provide new evidence of a link between obesity and altered taste perception as well as TAS2R38 expression in the stomach.

Genetic variation in CD36 is associated with dietary intake in Korean males

Fat is one of the six types of taste. Perceived taste intensity could affect the preference for a food and whether or not it is consumed. Cluster of differentiation 36 (CD36) translocates fatty acids on the cellular membrane and is involved in the oral fat-sensing mechanism. Therefore, genetic variation rs1761667 in CD36 is known to be associated with the perception of fat taste and, hence, its dietary intake. This study examined whether CD36 rs1527479 T>C, a proxy of rs1761667, is associated with fat intake and related dietary behaviour in Koreans. Using the data of the Ansan/Ansung Study, a part of the Korean Genome Epidemiology Study, the association of rs1527479 with the intake of macronutrients, including fat and selected foods, and fat-related dietary behaviours were investigated in 3194 males and 3425 females grouped by their degree of obesity. The findings suggested that rs1527479 did not have a meaningful effect on the intake of fat or other macronutrients or on the selection of food among non-obese females and males. However, in males with obesity, the genetic variation showed a significant association with vegetable intake. Obese males with the mutant CC genotype had substantially lower cruciferous vegetable consumption (adjusted P = 0·0015) than individuals with the TT and CT genotypes. Rs1527479 had no significant effect on the frequency of consuming fried foods or commonly used types of seasoning and cooking oils. In conclusion, CD36 genetic variation was associated with the intake of cruciferous vegetables but not fat intake in obese Korean males.

The Associations Between Bitter and Fat Taste Sensitivity, and Dietary Fat Intake: Are They Impacted by Genetic Predisposition?

A relationship between bitter and fat taste sensitivity, CD36 rs1761667 and TAS2R38 has been demonstrated. However, research is scarce and does not take diet into account. This study aimed to explore associations between genetics, fat and bitter taste sensitivity and dietary fat intake in healthy UK adults. A cross-sectional study was carried out on 88 Caucasian participants (49 females and 39 males aged 35 ± 1 years; body mass index 24.9 ± 0.5 kg/m2). Bitter taste sensitivity was assessed using phenylthiocarbamide (PTC) impregnated strips and the general Labeled Magnitude Scale. Fat taste sensitivity was assessed by the Ascending Forced Choice Triangle Procedure and dietary intake with a semi-quantitative food frequency questionnaire. Genotyping for rs713598, rs1726866, rs10246939, and rs1761667 was performed. Participants with TAS2R38 PAV/PAV diplotype perceived PTC strips as more bitter than groups carrying AVI haplotypes (AVI/AVI, P = 1 × 10-6; AVI/AAV, P = 0.029). CD36 rs1761667 was associated with fat taste sensitivity (P = 0.008). A negative correlation between bitter taste sensitivity and saturated fat intake was observed (rs = -0.256, P = 0.016). When combining the CD36 genotypes and TAS2R38 diplotypes into one variable, participants carrying both TAS2R38 AVI haplotype and CD36 A allele had a higher intake of saturated fat compared to carriers of CD36 GG genotype or TAS2R38 PAV/PAV and PAV/AAV diplotypes (13.8 ± 0.3 vs. 12.6 ± 0.5%TEI, P = 0.047) warranting further exploration in a larger cohort.

Self-Rated Aversion to Taste Qualities and the PROP Taster Phenotype Associate with Alcoholic Beverage Intake and Preference

Consumers often identify “taste” as an important factor when selecting alcoholic beverages. Although it is assumed that reduced alcohol consumption in PROP super-tasters is due to a greater dislike of the nominally aversive sensations that they experience more intensely (e.g., bitterness) when compared to PROP non-tasters, this question has not been specifically asked to them. Therefore, we examined consumers’ self-reported aversion towards specific sensory attributes (bitter, hot/burn, dry, sour, sweet, carbonation) for four alcoholic beverage types (white wine, red wine, beer, spirits) using a convenience sample of U.S. wine consumers (n = 925). Participants rated 18 statements describing different combinations of sensory attributes and alcoholic beverages on a 5-point Likert scale (e.g., Beer tastes too bitter for me). Individuals who tended to agree more strongly with the statements (i.e., they were more averse; p(F) < 0.05) tended to (i) consume less of all beverage types, (ii) consume a higher proportion of white wine (p(r) < 0.05), and (iii) were more likely to be female or PROP super-tasters. The results suggest that self-reported aversion to specific sensory attributes is associated with not only lower overall intake of alcoholic beverages, but also a shift in the relative proportions of beverage type consumed; a key finding for studies investigating how taste perception impacts alcohol consumption.

Predominant Qualities Evoked by Quinine, Sucrose, and Capsaicin Associate With PROP Bitterness, but not TAS2R38 Genotype

Genetic variability in the ability to taste thiourea compounds has been studied for 80+ years. Over the last 3 decades, many studies have reported perceived intensity of concentrated propylthiouracil (PROP) associates with greater intensity from a broad range of stimuli, including nonbitter tastants, irritants, and retronasally delivered odorants. Thus, PROP phenotype has become a common measure of individual differences in orosensation. Much, but not all, of the phenotypic variation in PROP bitterness is explained by TAS2R38 polymorphisms. While differences in PROP bitterness are clearly due to genetic variation, mechanistically it is challenging to envision how this receptor (narrowly tuned to the N-C=S moiety) relates to overall orosensory response. Here, we report data for 200+ individuals who had been genotyped for TAS2R38 and phenotyped for PROP in a laboratory setting. Participants also reported the intensity of quinine, capsaicin, and sucrose on a general Labeled Magnitude Scale. Our data recapitulate earlier reports associating PROP bitterness with the intensity of the predominant qualities of sucrose, quinine, and capsaicin; however, we also find correlations between the intensities of sucrose, quinine, and capsaicin were much stronger with each other than with PROP. As expected, TAS2R38 diplotype did not associate with the intensity of sucrose, quinine, or capsaicin. The strength of PROP-capsaicin and PROP-sucrose relationships increased after grouping participants by TAS2R38 diplotype, with the greatest increases in association observed within homozygotes. Collectively, this suggests the suprathreshold intensity of PROP is a confounded phenotype that captures both genetic variation specific to N-C=S compounds and overall orosensation.