The roles of bitter and sweet taste receptors in food allergy: Where are we now?

Food allergy (FA) is a growing global concern, which contributes significantly to anaphylaxis and severe allergic reactions. Despite advancements in treatments like allergen immunotherapy and biologics, current approaches have notable limitations and there is a pressing need for new therapeutic strategies. Recent research into taste receptors has unveiled their potential role in FA, offering fresh perspectives for understanding and managing this condition. Taste receptors, particularly type 1 taste receptors (TAS1Rs/T1Rs, sweet taste receptors) and type 2 taste receptors (TAS2Rs/T2Rs, bitter taste receptors), are distributed not only in the oral cavity but also in various extra-oral tissues, and their interactions with immune responses are increasingly recognized. This review highlights the connections between taste receptors and FA, exploring how taste receptor mechanisms might contribute to FA pathogenesis and treatment. Taste receptors, especially TAS2Rs, which include multiple subtypes with varying ligand specificities, have been implicated in modulating allergic responses and could serve as targets for novel FA therapies. Additionally, compounds such as bitter agents and sweeteners that interact with taste receptors show promise in influencing FA outcomes. This review emphasizes the need for further research into the mechanisms of taste receptor involvement in FA and suggests that targeting these receptors could provide new avenues for therapeutic intervention in the future.

Contributions and future potential of animal models for geroscience research on sensory systems

Sensory systems mediate our social interactions, food intake, livelihoods, and other essential daily functions. Age-related decline and disease in sensory systems pose a significant challenge to healthy aging. Research on sensory decline in humans is informative but can often be difficult, subject to sampling bias, and influenced by environmental variation. Study of animal models, including mice, rats, rabbits, pigs, cats, dogs, and non-human primates, plays a complementary role in biomedical research, offering advantages such as controlled conditions and shorter lifespans for longitudinal study. Various species offer different advantages and limitations but have provided key insights in geroscience research. Here we review research on age-related decline and disease in vision, hearing, olfaction, taste, and touch. For each sense, we provide an epidemiological overview of impairment in humans, describing the physiological processes and diseases for each sense. We then discuss contributions made by research on animal models and ideas for future research. We additionally highlight the need for integrative, multimodal research across the senses as well as across disciplines. Long-term studies spanning multiple generations, including on species with longer life spans, are also highly valuable. Overall, integrative studies of appropriate animal models have high translational potential for clinical applications, the development of novel diagnostics, therapies, and medical interventions and future research will continue to close gaps in these areas. Research on animal models to improve understanding of the biology of the aging senses and improve the healthspan and additional research on sensory systems hold special promise for new breakthroughs.

Perception of Sour Taste in Subjects with Olfactory Deficits: Role of Myrtle Aromatization

BACKGROUND

Sour taste is associated with acid-base homeostasis, which is critical to cell metabolism and health conditions. Vinegar, which contains acetic acid as the main component, is a sour food considered the second most common condiment in Italy.

OBJECTIVES

The aim of the study was to assess differences in sourness perception in subjects with olfactory deficits compared to controls and evaluate myrtle aromatization's potential effect in modulating sourness perception in subjects with hyposmia.

METHODS

To this end, olfactory function was assessed with the Sniffin' Sticks test and gustatory function by the Taste Strips test. Sensory perception of a traditional white wine vinegar (WV) and a WV aromatized with myrtle (AWV) was evaluated. The sourness perception of the two vinegars was estimated through the rates of odor and taste pleasantness, intensity, and familiarity using a labeled hedonic Likert-type scale.

RESULTS

Our data indicated that in patients with hyposmia, a significant decrease was observed only in sour taste perception compared to controls. The increase in vinegar aroma due to the myrtle aromatization modulated sourness perception in patients with hyposmia.

CONCLUSIONS

Myrtle aromatization increased the number of significant correlations between odor and the taste dimensions of the vinegar in controls and in patients with hyposmia in a different manner.

Taste and oral somatosensation: Role of PTC bitter sensitivity, gender, and age

Sensitivity to the bitterness of phenylthiocarbamide (PTC) is considered to be linked to general taste perception, which is higher in women, and exhibits a slight decrease with age. Additionally, PTC sensitivity may contribute to somatosensory perception of spiciness and astringency. However, controversial data have been reported. This study investigates the relation between PTC perception, age, and gender on taste and somatosensory sensitivity using the Seven-iTT. A total of 200 healthy participants were classified based on their PTC perception, and subjects underwent an extended version of Seven-iTT to identify and rate the intensity of twelve stimuli. Results indicated that individuals classified as Tasters (T) exhibited higher taste scores compared to Non-Tasters (NT) for PTC, with age serving as a significant factor (p ≤ 0.009). Women outperformed men only among NT (p = 0.019). Older T demonstrated higher taste sensitivity than NT, suggesting that PTC status might act as a protective factor of gustatory function in aging. While PTC taster status significantly affected the intensity of sweet, salty, and bitter sensations (p ≤ 0.032), it had minimal impact on the intensity of somatosensory sensations (capsaicin and tannins). The combined use of Seven-iTT and the investigation of PTC status show promise for applications in research and clinical practice, offering a comprehensive approach to understanding taste perception and its implications for diet, nutrition, and aging.

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.

Investigation of the fungiform papillae number in children with tooth number anomalies

OBJECTIVE

This cross-sectional study investigated the association between fungiform papillae (FP) numbers and tooth number anomalies in children, considering variables related to hypodontia and hyperdontia. The aim was to explore this association while adjusting for age and sex differences.

MATERIALS AND METHODS

A total of 144 children (aged 8-10) were categorized into hypodontia (n = 48), hyperdontia (n = 48), and control groups (n = 48). Clinical and radiographic diagnoses were used to classify tooth number anomalies. Hypodontia was categorized by number and location, while hyperdontia was categorized by number, shape, and location. FP were assessed using the Denver Papillae Protocol. Data analyses were performed using NCSS software, with p < 0.05 considered statistically significant.

RESULTS

The hypodontia group (22.5 ± 8.4) exhibited significantly lower FP than the control group (30.4 ± 9.2) and the hyperdontia group (27.9 ± 7.8) (p < 0.0005, p = 0.003, respectively). No significant difference existed between the hyperdontia and control groups. FP numbers in hypodontia subgroups showed no significant differences based on teeth agenesis numbers or locations. Similarly, hyperdontia subgroup analyses revealed no significant differences in FP numbers based on supernumerary teeth shapes (supplemental, conical, tuberculoid, paramolar) or the numbers of supernumerary teeth.

CONCLUSIONS

The lower FP numbers in children with hypodontia suggested an association between teeth and FP number. However, the non-significant difference in FP numbers with hyperdontia underscored the complexity of tooth development, warranting further investigations.

CLINICAL RELEVANCE

Children with hypodontia may exhibit distinct FP numbers compared to those without tooth number anomalies.

Does presbygeusia really exist? An updated narrative review

This review critically assessed the existence of presbygeusia, i.e., the impairment in taste perception occurring in the elderly, as a natural part of the aging process and its potential clinical implications. Several factors might contribute to age-related taste alterations (TAs), including structural changes in taste buds, alterations in saliva composition, central nervous system changes, and oral microbiota dysbiosis. A comprehensive literature review was conducted to disentangle the effects of age from those of the several age-related diseases or conditions promoting TAs. Most of the included studies reported TAs in healthy elderly people, suggesting that presbygeusia is a relatively frequent condition associated with age-related changes in the absence of pathological conditions. However, the impact of TAs on dietary preferences and food choices among the elderly seems to be less relevant when compared to other factors, such as cultural, psychological, and social influences. In conclusion, presbygeusia exists even in the absence of comorbidities or drug side effects, but its impact on dietary choices in the elderly is likely modest.

Astringency and its sub-qualities: a review of astringency mechanisms and methods for measuring saliva lubrication

Astringency is an important mouthfeel attribute that influences the sensory experiences of many food and beverage products. While salivary lubricity loss and increased oral friction were previously believed to be the only astringency mechanisms, recent research has demonstrated that nontactile oral receptors can trigger astringency by responding to astringents without mechanical stimulation. Various human factors have also been identified that affect individual responses to astringents. This article presents a critical review of the key research milestones contributing to the current understanding of astringency mechanisms and the instrumental approaches used to quantify perceived astringency intensity. Although various chemical assays or physical measures mimic in-mouth processes involved in astringent mouthfeel, this review highlights how one chemical or physical approach can only provide a single measure of astringency determined by a specific mechanism. Subsequently, using a single measurement to predict astringency perception is overly idealistic. Astringency has not been quantified beyond the loss of saliva lubrication; therefore, nontactile receptor-based responses must also be explored. An important question remains about whether astringency is a single perception or involves distinct sub-qualities such as pucker, drying, and roughness. Although these sub-quality lexicons have been frequently cited, most studies currently view astringency as a single perception rather than dividing it into sub-qualities and investigating the potentially independent mechanisms of each. Addressing these knowledge gaps should be an important priority for future research.

Fine wine recognition and appreciation: It is time to change the paradigm of wine tasting

Wine quality maybe understood under two perspectives: (a) commercial quality, intended to satisfy overall consumers, and (b) fine wine quality, aimed at achieving a product with aesthetic value. The current food sensory techniques (e.g. Descriptive Analysis) have been successfully applied to develop wines accepted worldwide and characterized by pleasant sweetish flavours and smooth mouthfeel. On the contrary, these techniques are not suited to characterize fine wines given their dependence on sensory properties with aesthetic value. The conventional tasting approaches follow the sequence of vision, smell (orthonasal), taste and mouthfeel, ending by an overall evaluation. The sensory descriptors tend to be analytic (e.g. different aromas and tastes) or synthetic (e.g. body, structure) and the quality judgement is left for the final step. Some synthetic attributes may have an aesthetic significance (e.g. complexity, harmony, depth) and are more valued when the analytic or synthetic descriptors are highly praised (e.g. oakiness, silkiness, body, minerality). Consequently, these highly praised attributes are regarded as surrogates of fine wine quality. However, commercial wines are frequently judged of higher quality than fine wines irrespective of the taster expertise. We argue that the conventional sensory analysis sequence makes the overall evaluation secondary in relation to the previous analytical steps blurring the assessment of wine's aesthetic properties. Probably due to top-down processing, the initial evaluation of colour or flavours governs the final overall quality evaluation that may be inconsistently rated. Then, to promote the recognition of fine wines, tasting should begin by first acknowledging the aesthetic properties and only proceed to the analytical steps if necessary. A tasting method is proposed to consumer educational programs where emotional responses are used to explain the differences between commercial and fine wine styles. Furthermore, cultural aspects should be included to appreciate the wholeness of wine. Hopefully, this holistic perspective would turn wine appreciation more approachable and facilitate the recognition of fine wines among consumers, increasing their appreciation and enjoyment.

Alteration of taste perception, food neophobia and oral microbiota composition in children with food allergy

Currently, the mechanisms underlying sensory perception and sensory performance in children with food allergies are far from being understood. As well, only recently, single research afforded the oral host-commensal milieu, addressing oral microbial communities in children with peanut allergies. To bridge the current gaps in knowledge both in the sensory and microbial fields, a psychophysiological case-control study was performed in allergic children (n = 29) and a healthy sex-age-matched control group (n = 30). Taste perception, food neophobia, and liking were compared in allergic and non-allergic children. The same subjects were characterized for their oral microbiota composition by addressing saliva to assess whether specific profiles were associated with the loss of oral tolerance in children with food allergies. Our study evidenced an impaired ability to correctly identify taste qualities in the allergic group compared to controls. These results were also consistent with anatomical data related to the fungiform papillae on the tongue, which are lower in number in the allergic group. Furthermore, distinct oral microbial profiles were associated with allergic disease, with significant down-representations of the phylum Firmicutes and of the genera Veillonella spp., Streptococcus spp., Prevotella spp., and Neisseria spp. For the first time, this study emphasizes the link between sensory perception and food allergy, which is a novel and whole-organism view of this pathology. Our data indicated that an impaired taste perception, as regards both functionality and physiologically, was associated with food allergy, which marginally influences the food neophobia attitude. It is also accompanied by compositional shifts in oral microbiota, which is, in turn, another actor of this complex interplay and is deeply interconnected with mucosal immunity. This multidisciplinary research will likely open exciting new approaches to therapeutic interventions.

Tongue papillae density and fat taster status- a cardinal role on sweet and bitter taste perception among Indian population

Obesity is a complex nutritional disorder that may be influenced by calorie intake and eating behaviours. Aside from many studies, the influence of papillae count on obesity is still debated. Despite the multiple variables connected to weight gain and altered taste perception, determining the association between papillae count and taste sensitivity to fat, sweet and bitter tastes, in particular, has recently become a focus of attention. This study aimed to rule out the relationship between the number of papillae on different areas of the tongue and taste sensitivity in people (n = 150) among the various groups depending on their body mass index (BMI) and fat taste sensitivity. The general labelled magnitude scale (gLMS) was used for the taste sensitivity analysis, and participants were asked to rate the intensity of each concentration of the different tastants. Using a digital camera to obtain a picture of the tongue, the density of the papillae on the tongue was counted manually by three different operators. The study reveals that the total papillae density and BMI had a direct negative correlation (r = -0.43), with papillae density (PD) decreasing as BMI increased. Concurrently, persons with higher BMIs had lower papillae distributions (32.38 ± 1.85 PD/cm²) and significantly lower perceptions of the intensity of fat taste. Further examining papillae density in the anterior front part of the tongue, the front-right section, showed significantly higher papillae distribution (74.04 ± 2.11 PD/cm²) than the front-left section. When considering the sensitivity in the tip of the tongue, middle tongue, and whole mouth, high-sensitivity individuals for fat are more sensitive to both sweet and bitter tastes. Overall, the results of this study demonstrated a strong relationship between taste sensitivity in the Indian population, BMI, and tongue papillae density in various regions of the tongue.

The role of saliva in taste dysfunction among cancer patients: Mechanisms and potential treatment

Two of the highest prevalent symptoms reported by cancer patients are taste dysfunction (17.6-93%) and dry mouth/xerostomia (40.4-93%). While it has been hypothesized that reduced saliva may impair taste function, few studies investigate the co-occurrence of taste and dry mouth symptoms in cancer patients. This review provides a summary of the physiological relationship between saliva and taste, focusing on taste transduction mechanism, regulation of the taste sensitivity, and protection of taste receptor cells, including the impact of cancer treatments and malignancy on saliva function, salivary components, and the mechanisms in which it can negatively impact the taste function. Here, the authors present a scoping review of the recent literature reporting on the association between taste dysfunction and dry mouth in cancer patients, including reports of non-pharmaceutical liposomal agents or drugs taken to improve dry mouth symptoms that also assess taste dysfunction. Considering the complexities of cancer and cancer treatment, understanding the physiological relationship between saliva and taste function may provide important insight into identifying treatments for alleviating taste dysfunction and dry mouth symptoms. There are substantial research gaps given the limited studies assessing the co-occurrence of taste loss and dry mouth and inconsistencies in the assessment of these symptoms. Clinical studies examining taste dysfunction will provide a foundational groundwork that will help understand the relationship between taste and saliva. Considering the increased rates in survivorship and the significant negative impact of taste dysfunction on quality of life, more research is needed to reduce the suffering of cancer patients.

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.

Assessment of Taste Function

Taste disorders, impacting well-being and physical health, can be caused by many etiologies including the use of medication. Recently, taste disturbance is also considered as one of the predominant symptoms of COVID-19 although its pathogenesis requires further research. Localized taste disorders may be overlooked considering that whole-mouth taste perception is insured through several mechanisms. Individuals often fail to discern taste from flavor, and interviews/surveys are insufficient to properly assess taste function. Hence, various taste assessment methods have been developed. Among them, psychophysical methods are most widely applied in a clinical context. Less-biased electrophysiological, imaging, or morphological methods are used to a much lesser degree. Overall, more research is needed in the field of taste.

Food Preferences and Obesity

Obesity is a multifactorial disease with several potential causes that remain incompletely understood. Recent changes in the environment, which has become increasingly obesogenic, have been found to interact with individual factors. Evidence of the role of taste responsiveness and food preference in obesity has been reported, pointing to a lower taste sensitivity and a higher preference and intake of fat and, to a lesser extent, sweet foods in obese people. Studies in the last decades have also suggested that individual differences in the neurophysiology of food reward may lead to overeating, contributing to obesity. However, further studies are needed to confirm these findings. In fact, only a limited number of studies has been conducted on large samples, and several studies were conducted only on women. Larger balanced studies in terms of sex/gender and age are required in order to control the confounding effect of these variables. As many factors are intertwined in obesity, a multidisciplinary approach is needed. This will allow a better understanding of taste alteration and food behaviours in obese people in order to design more effective strategies to promote healthier eating and to prevent obesity and the related chronic disease risks.

Comparison of manual and machine learning image processing approaches to determine fungiform papillae on the tongue

Human taste perception is associated with the papillae on the tongue as they contain a large proportion of chemoreceptors for basic tastes and other chemosensation. Especially the density of fungiform papillae (FP) is considered as an index for responsiveness to oral chemosensory stimuli. The standard procedure for FP counting involves visual identification and manual counting of specific parts of the tongue by trained operators. This is a tedious task and automated image analysis methods are desirable. In this paper a machine learning image processing method based on a convolutional neural network is presented. This automated method was compared with three standard manual FP counting procedures using tongue pictures from 132 subjects. Automated FP counts, within the selected areas and the whole tongue, significantly correlated with the manual counting methods (all ρs ≥ 0.76). When comparing the images for gender and PROP status, the density of FP predicted from automated analysis was in good agreement with data from the manual counting methods, especially in the case of gender. Moreover, the present results reinforce the idea that caution should be applied in considering the relationship between FP density and PROP responsiveness since this relationship can be an oversimplification of the complexity of phenomena arising at the central and peripherical levels. Indeed, no significant correlations were found between FP and PROP bitterness ratings using the automated method for selected areas or the whole tongue. Besides providing estimates of the number of FP, the machine learning approach used a tongue coordinate system that normalizes the size and shape of an individual tongue and generated a heat map of the FP position and normalized area they cover. The present study demonstrated that the machine learning approach could provide similar estimates of FP on the tongue as compared to manual counting methods and provide estimates of more difficult-to-measure parameters, such as the papillae's areas and shape.

The effects of taste sensitivity and repeated taste exposure on children's intake and liking of turnip (Brassica rapa subsp. rapa); a bitter Brassica vegetable

Low consumption of vegetables in children is a concern around the world, hence approaches aimed at increasing intake are highly relevant. Previous studies have shown that repeated taste exposure is an effective strategy to increase vegetable acceptance. However, few studies have examined the effect of repeated taste exposure on children varying in bitter taste sensitivity. This study investigated the influence of taste genotypes and phenotypes on the effects of repeated taste exposure to a Brassica vegetable. 172 preschool children aged 3-5 years were recruited into this study. Turnip was selected as the target vegetable and parents completed a questionnaire to ensure unfamiliarity. During the intervention, children were exposed to steamed-pureed turnip for 10 days (once/day). Intake and liking were measured before, during and after the intervention, and a follow-up was done 3 months post-intervention. Taste genotypes (TAS2R38 and gustin (CA6) genotypes) and taste phenotypes (PROP taster status and fungiform papillae density) were determined. There was a significant effect of exposure shown by significant increases in intake (p < 0.001) and liking (p = 0.008) post-intervention; however, there were no significant effects of taste genotypes or phenotypes on intake and liking. In summary, repeated taste exposure is confirmed to be a good strategy to increase vegetable acceptance in children, regardless of bitter taste sensitivity.

Associations Among Taste Perception, Food Neophobia and Preferences in Type 1 Diabetes Children and Adolescents: A Cross-Sectional Study

Type 1 diabetes (T1D) is one of the most common systemic diseases in childhood which predisposes the patient to serious short-term and long-term complications, affecting all body systems. Taste and olfactory impairments were first described a long time ago in adult patients affected by diabetes (both type 1 and type 2 diabetes). However, studies evaluating taste perception, behavioral attitudes (e.g., food neophobia), and preferences toward foods in children and adolescents affected by T1D are globally lacking. Therefore, the purpose of this study was to assess taste sensitivity, food neophobia, and preferences among children and adolescents affected by T1D and healthy controls in a cross-sectional study. T1D patients presented a significantly lower ability in general to correctly identify taste qualities, especially bitter and sour tastes. Moreover, they were characterized by fewer fungiform papillae compared to controls, as well as a lower responsiveness to the bitter compound 6-n-propylthiouracil (PROP). There were no significant differences in food neophobia scores between the two groups, but differences were observed in the mean hedonic ratings for some product categories investigated. Diabetic patients showed a greater liking for certain type of foods generally characterized by sourness and bitterness, an observation probably linked to their impaired ability to perceive taste stimuli, e.g., sourness and bitterness. These results may help to enhance the understanding of these relationships in populations with elevated diet-related health risks.

Impact of Fungiform Papillae Count on Taste Perception and Different Methods of Taste Assessment and their Clinical Applications: A comprehensive review

Fungiform papillae are raised lingual structures which contain taste buds and thus play an important role in taste perception. These structures vary in number due to their relative sensitivity to a range of systemic and local factors which affect the dorsum of the tongue. Taste sensation can be measured using both chemical and electrical methods; however, the number of fungiform papillae has a direct effect on chemogustometric and electrogustometric values during evaluation. This review provides a general overview of fungiform papillae, their quantification methods and the various factors which may affect these structures. In addition, numerous methods of recording taste sensation and their clinical applications are highlighted.

Individual differences in the perception of orthonasal irritation induced by food

Oral responsiveness to the burning/spicy sensation affects food behaviors and diet; therefore, it is reasonable to hypothesize that the variation in nasal responsiveness to irritant foods may play a role in modulating food behaviors. This study explored the variation among individuals in orthonasal irritation induced by smelling food ingredients containing irritant compounds: mustard oil (2.0, 10.0, and 100.0% v/v mustard oil in corn oil; irritant compound: allyl isothiocyanate); vinegar (3.5, 42.3, and 98.6% v/v vinegar in water; irritant compound: acetic acid); and wasabi (0.1, 0.2, and 0.4% w/w wasabi powder in water; irritant compound: allyl isothiocyanate). Sixty-eight subjects (40% males; 19-87 years) smelled the nine samples and rated their perceived intensity of odor, irritation and liking. Wide individual variation in the perception of irritation and odor intensity was found, especially at the highest concentrations. Young individuals were the most sensitive to all stimuli. No significant differences were found between males and females. Fifty-seven percent of subjects were "HYPO" and 43 percent "HYPER" responsive to irritation, respectively. Perceived irritation was positively correlated with odor intensity and tended to be negatively correlated with liking, especially in familiar stimuli. The results suggest that the variation in nasal responsiveness to irritant foods may contribute to influencing food acceptance and therefore, to modulating food behaviors.

Individual Variation in PROP Status, Fungiform Papillae Density, and Responsiveness to Taste Stimuli in a Large Population Sample

Despite considerable research investigating the role of 6-n-propylthiouracil bitterness perception and variation of fungiform papillae density in food perception, this relationship remains controversial as well as the association between the 2 phenotypes. Data from 1119 subjects (38.6% male; 18-60 years) enrolled in the Italian Taste project were analyzed. Responsiveness to the bitterness of 6-n-propylthiouracil was assessed on the general Labeled Magnitude Scale. Fungiform papillae density was determined from manual counting on digital images of the tongue. Solutions of tastes, astringent, and pungent sensations were prepared to be moderate/strong on a general Labeled Magnitude Scale. Four foods had tastants added to produce 4 variations in target sensations from weak to strong (pear juice: citric acid, sourness; chocolate pudding: sucrose, sweetness; bean purée: sodium chloride, saltiness; and tomato juice: capsaicin, pungency). Women gave ratings to 6-n-propylthiouracil and showed fungiform papillae density that was significantly higher than men. Both phenotype markers significantly decreased with age. No significant correlations were found between 6-n-propylthiouracil ratings and fungiform papillae density. Fungiform papillae density variation does not affect perceived intensity of solutions. Responsiveness to 6-n-propylthiouracil positively correlated to perceived intensity of most stimuli in solution. A significant effect of fungiform papillae density on perceived intensity of target sensation in foods was found in a few cases. Responsiveness to 6-n-propylthiouracil positively affected all taste intensities in subjects with low fungiform papillae density whereas there were no significant effects of 6-n-propylthiouracil in those with high fungiform papillae density. These data highlight a complex interplay between 6-n-propylthiouracil status and fungiform papillae density and the need of a critical reconsideration of their role in food perception and acceptability.

Influences of Psychological Traits and PROP Taster Status on Familiarity with and Choice of Phenol-Rich Foods and Beverages

Plant phenolics are powerful antioxidants and free radical scavengers that can contribute to the healthy functional properties of plant-based food and beverages. Thus, dietary behaviours rich in plant-based food and beverages are encouraged. However, it is well-known that the bitter taste and other low-appealing sensory properties that characterize vegetables and some other plant-based foods act as an innate barrier for their acceptance. The aim of this study was to investigate the influence of psychological traits and PROP status (the responsiveness to bitter taste of 6-n- propylthiouracil) on the choice of and familiarity with phenol-rich vegetables and beverages varying in recalled level of bitterness and astringency. Study 1 aimed at assessing the variations of the sensory properties of vegetable and coffee/tea items with two check-all-that-apply (CATA) questionnaires (n = 201 and n = 188 individuals, respectively). Study 2 aimed at investigating how sensitivity to punishment, to reward, and to disgust, food neophobia, private body consciousness, alexithymia, and PROP responsiveness affect choice and familiarity with phenol-rich foods (n = 1200 individuals). A Choice Index was calculated for vegetables (CV) and coffee/tea (CC) as a mean of the choices of the more bitter/astringent option of the pairs and four Familiarity Indices were computed for vegetables (FV) and coffee/tea (FC), higher (+) or lower (-) in bitterness and astringency. Subjects higher in food neophobia, sensitivity to punishment or sensitivity to disgust reported significantly lower choice indices than individuals lower in these traits, meaning that they systematically opted for the least bitter/astringent option within the pairs. Familiarity with vegetables was lower in individuals high in sensitivity to punishment, in food neophobia and in alexithymia, irrespective of their sensory properties. The Familiarity Index with coffee/tea characterized by higher bitterness and astringency was lower in individuals high in food neophobia, sensitivity to disgust, and alexithymia. No significant effect of PROP was found on any indices. The proposed approach based on product grouping according to differences in bitterness and astringency allowed the investigation of the role of individual differences in chemosensory perception and of psychological traits as modulators of phenol-rich foods preference and consumption.

Exploring variability in detection thresholds of microparticles through participant characteristics

This study investigated how product familiarity and physiological characteristics of participants affect detectability of microparticles in viscous and semi-solid foods.