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Individual variation in fungiform papillae density with different sizes and relevant associations with responsiveness to oral stimuli
Abstract
The association of fungiform papillae (FP) density with responsiveness to oral sensations is controversial. It has been speculated that FP size is a relevant feature for oral responsiveness, thus partially accounting for inconsistencies between FP density and oral responsiveness. This study aims to evaluate factors affecting the number of FP with different diameter sizes (age, gender, PROP status) and to explore the relevant associations with responsiveness to oral sensations in water solutions and food products.
Three-hundred-fifty subjects participating in the Italian Taste project were involved, balanced for gender (53% females) and age class (18–30, 35%; 31–45, 35%; 46–60, 30%). The automated image analysis of tongue pictures was used to detect FP and count their frequencies, distinguishing 11 diameter size classes (range from 0.3 to 1.05 mm). Frequencies were converted into FP densities (FP/cm²) for each size. Taste responsiveness in water solutions (sour, bitter, salty, umami, sweet, astringent, pungent) and in three food products with varied intensity of target sensations (pear juice for sourness; bean purée for saltiness; tomato juice for pungency) was measured.
Density of FP from all size classes decreased with age. Females showed higher FP density in size of 0.78–0.84 mm diameter, and males in the size of 0.44–0.49 mm. PROP status did not significantly affect the density of FP in any size class. Principal Component Analysis on individual FP density values of the 11 classes allowed identifying four subject groups with different FP patterns: high density and large diameter (HighLarge), high density and small diameter (HighSmall), low density and large diameter (LowLarge), low density and small diameter (LowSmall). FP pattern groups significantly affected oral responsiveness, the highest responsiveness was associated to the uniform pattern characterized by low density and small size FP.
... Recently a classification of subjects based on their differences in both FP density and diameter was proposed (Piochi et al., 2019). Positive associations were reported between FPD and the perception of texture related sensations such as creaminess in milk (Hayes & Duffy, 2007) and hardness and crunchiness in biscuits (Zhou et al., 2021). ...
... On the other hand, other studies failed to find significant associations between FPD and food texture attributes, such as astringency in bread (Bakke & Vickers, 2008). Furthermore, FP size was hypothesised to associate with oral responsiveness (Melis et al., 2013) with uniform patterns of low density and small size FP related with higher responsiveness to tastes, astringency and pungency (Piochi et al., 2019). ...
... Gender was confirmed to be a predictor of PROP bitterness responsiveness, with women showing significantly higher sensitivity than men (Linda M. Bartoshuk, Duffy, & Miller, 1994;Monteleone et al., 2017;Tepper, Banni, Melis, Crnjar, & Barbarossa, 2014). FPD mean values were similar to those reported in previous studies on young adult population (Piochi et al., 2019) and women were confirmed to have higher FPD than men (Fischer et al., 2013;Dinnella et al., 2018). ...
This study investigated the individual variability in oral tactile sensitivity considering touch, by means of Von Frey Hair monofilaments (VFH) and spatial resolution, using the grating orientation test (GOT). The relationships of the two measures with 6‐n‐propylthiouracil (PROP) responsiveness and fungiform papillae density and size were investigated. One hundred and forty‐four subjects (48.6% women, aged 18‐30) participated in the study. VFH and GOT thresholds were assessed by three‐down/one‐up staircase method. Responsiveness to 3.2mM PROP was assessed on the general Labelled Magnitude Scale. Fungiform papillae density (FPD) and size were determined from automated counting. VFH thresholds appeared unsuitable to reveal individual variation in responsiveness to point‐pressure on the tongue. The frequency of GOT thresholds approximated a normal distribution and covered the whole range of variation, thus indicating an ability to measure individual variation in oral tactile sensitivity. No significant linear correlations were found between any of the oral tactile sensitivity measures and PROP responsiveness, FPD total and size class. VFH and GOT thresholds were not significantly associated. Agglomerative hierarchical clustering was used to classify participants for their PROP responsiveness, total FPD and GOT threshold. Three clusters were identified, C1 (n=67), Cl2 (n=42) and Cl3 (n=35), differing for PROP responsiveness and FPD only. Results encourage future studies to explore association between GOT and both perception and preference for different food texture. Furthermore, deeper investigation of individual variability in sensitivity to different types of oral tactile stimuli would be helpful to capture differences in tactile sensitivity among the most sensitive individuals.
... Our study showed that in children, FP numbers decreased, while the age increased (r = −0.0441, p = 0.001) in accordance with previous studies [5,[15][16][17][18]. This outcome is consistent with the results of FP numbers of adults and children, where children have more FP [19,20]. ...
... Also other studies reported that the female FP number was higher than males [22,25,26]. Several other studies found no significant difference between males and females [13,18,21,23], and one study found a significant gender difference only in some age groups (30-39 years and 40-49 years) [26]. In two studies on children (7-12 years, 8-11 years), gender did not make a significant difference in FP number [5,13]. ...
Objectives
Fungiform papillae (FP) contain numerous taste buds. A genetic susceptibility between tasting via FP and caries risk has been suggested. This study aimed to investigate the relationship between FP number and dental caries and to determine whether FP number may be considered as a test for caries risk.Materials and methodsThe study included 157 children who attended the pediatric dentistry department at a public university. Questionnaires, including the children’s medical health, oral health knowledge, fluoride exposure, and taste preferences, were filled in by their parents. The FP number on the dorsal surface of the tongue was counted according to the Denver Papilla Protocol. Caries was recorded using deft/DMFT indices. Statistical analyses were performed using SPSS.ResultsThe FP number decreased significantly according to age (r = −0.441, p = 0.001), and the mean of the girls’ FP number was significantly higher than the boys’ (p = 0.022). A greater number of FP was associated with increased deft score (p = 0.02, odds ratio [OR] = 1.164).Conclusion
The caries risk increased in children who had more FP (FP > 30); therefore, FP number could be evaluated in terms of caries risk. FP number could be evaluated as a risk factor for determining dental caries since the risk of caries increased after a FP cut-off point of 29 was achieved.Clinical relevanceClinicians can start preventive treatments for caries earlier by determining the FP number for each child.
... Prior to the tasting, the subjects were extensively instructed in the use of the scale. 'The strongest imaginable sensation of any kind' was defined as the most intense sensation that involves remembered/imagined sensations in any sensory modality, including non-oral sensations, such as loudness, oral pain/irritation, or sight (e.g., the loudest sound ever heard, the most intense pain experienced, or the brightest light ever seen) [29,30]. Between products, a rinsing procedure was inserted. ...
Blue-veined cheese tends to polarize the consumers’ affective responses due to its strong flavor. This study aims to: (i) explore the consumers’ sensory perceptions and liking of Gorgonzola PDO cheese; (ii) identify the sensory drivers of acceptance for Gorgonzola in the function of the cheese style; (iii) characterize them by the volatile organic compounds (VOCs); and (iv) explore the relationships of the VOCs with sensory perception and liking. Six samples of Gorgonzola cheese differing in style (sweet vs. piquant), aging time (70–95 days), and production process (artisanal vs. industrial) were evaluated by 358 subjects (46% males, 18–77 years) using liking and Rate-All-That-Apply (RATA) tests. The cheese VOCs were measured by SPME/GC-MS. Liking was significantly higher for the sweet cheese than for the piquant cheese and for the artisanal cheese than for the industrial samples. Penalty Analysis showed that ‘creamy’, ‘sweet’, ‘nutty’, and ‘salty’ were significant drivers of liking while the ‘soapy’ and ‘ammonia’ flavors turned out to be drivers of disliking. Fifty-three VOCs were identified. Regression models revealed the significant highest associations between the VOCs and ‘ammonia’, ‘pungent’, ‘soapy’, and ‘moldy’ flavors. A good association was also found with the consumers’ liking. The identification of the sensory drivers of (dis) liking and their relationship with the VOCs of Gorgonzola opens up a new understanding of the consumers’ blue-veined cheese preferences.
... P = 0.196) (Fig. 9C). In support of our results, recent studies showed a lack of association between the papillae density and the human responsiveness to PROP (Garneau et al. 2014;Dinnella et al. 2018;Piochi et al. 2019). In the past Arvidson and Friberg (1980) had counted the number of taste buds in a population of single fungiform papillae by histological observation after taste stimulation to single taste buds. ...
The lingual surface potential (LSP), which hyperpolarizes in response to salt and bitter stimuli, is thought to be a bio-electrical signal associated with taste transduction in humans. In contrast, a recent study reported sweet and sour stimuli to evoke a depolarization of the LSP. We questioned the origin of such a depolarization because liquid junction potentials (JPs), which arise at the interfaces of recording electrode and taste solutions, are neglected in the report. We recorded the LSPs to sucrose and NaCl solutions on the human tongue using an Ag/AgCl electrode. To estimate JPs generated by each taste solution we made an agar model to simulate the human tongue. The lingual surface was rinsed with a 10 mM NaCl solution that mimics the sodium content of the lingual fluid. In the human tongue, sucrose dissolved in distilled water evoked a depolarizing LSP that could be attributed to JPs, resulting from the change in electrolyte concentration of the taste solution. Sucrose dissolved in 10 mM NaCl solution evoked a hyperpolarizing LSP which became more negative in a concentration dependent manner (300 ~ 1500 mM). Lactisole (3.75 mM), an inhibitor of sweet taste, significantly reduced the LSPs and decreased perceived intensity of sweetness by human subjects. The negative JPs generated by 100 mM NaCl in the agar model were not different from the LSPs to 100 mM NaCl. When the electrolyte environment on the lingual surface is controlled for JPs, the bio-electrical signal associated with sweet taste transduction is a hyperpolarizing potential.
... These factors include, among others, differences in anatomy of the peripheral taste system (i.e. fungiform papillae density) (Bartoshuk et al., 1994;Essick, Chopra, Guest, & McGlone, 2003;Piochi et al., 2019;Tepper & Nurse, 1998), age (Mennella, Pepino, Duke, & Reed, 2010;Tepper et al., 2017), gender (Barragán et al., 2018;Tepper et al., 2017), salivary protein composition , psychological traits such as alexithymia and disgust sensitivity (Ammann, Hartmann, & Siegrist, 2019), polymorphisms in the gustin (CA6) gene (involved in taste bud growth and maintenance) (Calò et al., 2011;Padiglia et al., 2010), and variation in TAS2R38 mRNA expression (Lipchock et al., 2017). ...
The combined influence of TAS2R38 genotype and PROP phenotype on oral sensations is still to be clarified. The present work investigates their influence on the intensity of basic tastes and somatosensory stimuli (capsaicin, aluminium sulphate), using a large cohort of 1117 individuals. The possible influences of gustin genotype and fungiform papillae density were also assessed. PROP phenotype was mainly associated with TAS2R38 genotype with AVI/AVI individuals reporting the lowest mean bitterness intensity (12.6±1.26), and PAV/AVI individuals rating PROP lower (46.53±0.93) than PAV/PAV individuals (54.14±1.33). However, 25% of AVI/AVI subjects reported PROP bitterness perception higher than ‘moderate’ and small percentages of both PAV/PAV and PAV/AVI responded very little to PROP stimulation. PROP phenotype significantly affected ratings to all the tastant solutions with ST subjects giving the highest ratings and NT the lowest. An unexpected systematic effect of TAS2R38 diplotype on perceived intensity was found, with AVI/AVI individuals rating tastant solution intensity higher than PAV/AVI and PAV/PAV for all the stimuli. Recursive partitioning analysis was used to determine the influence of the explanatory variables (TAS2R38 diplotype, PROP status, age and gender) on intensity for each tastant solution. Regression trees indicated that TAS2R38 genotype is the most important variable for explaining differences in intensity of basic tastes and astringency, when compared to PROP responsiveness, gender, and age. Gender was the primary determinant of heightened perception of pungency. PROP status was the second most influential variable in all the models, with limited influence only on sweetness and umami perception. No significant variations of intensity of taste and somatosensory sensations were found in association to gustin polymorphism or fungiform papillae density. These findings call for a re-examination of the notion that the TAS2R38 gene uniquely controls PROP tasting and for future research devoted to a more in-depth genetic characterization of the AVI/AVI group and its possible associations with other polymorphisms.
... Individuals differ greatly also in the density of fungiform papillae in the tongue, which host the taste receptors. A higher density has been associated with heightened sensitivity, but studies on larger samples did not confirm this association [51,52] and rather suggested that other factors play a role apart from the number of papillae, such as taste pore density [53,54]. Recently, some studies reported that obese children [55] and adults [56] have a lower number of fungiform papillae than normal-weight individuals. ...
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.
... Bartoshuk (2000) indicates that thresholds are insufficient in studying sensory experience since they only encompass the dimmest sensations and do not include the range of real-world sensory intensities. The second method involves fungiform papillae (FP) density (count and diameter sizes) (Hayes et al., 2008;Monteleone et al., 2017;Piochia et al., 2019). FP is innervated by both taste and touch nerves, and it is hypothesized that individuals with higher FP will also report higher 6-n-propylthiouracil (PROP) ratings and capsaicin burn (Karrer & Bartoshuk, 1991). ...
Sensory tests involving taste-sensitive individuals provide the food industry with valuable information. However, the traditional evaluation of 6-n-propylthiouracil (PROP) tasters, which is assumed to reflect general taste sensitivity, is controversial. Therefore, the present study aimed to develop a rapid method for the classification of an individual’s sensitivity to chemesthetic sensation, and to investigate the relationship between taste and chemesthetic sensation sensitivity at the suprathreshold level. In all, 72 young adults were screened and participated in the tests. The intensity of the pungency, heat, bitterness and saltiness that were presented via five concentrations of Sichuan pepper oleoresin (Spo), capsaicin, PROP and NaCl, respectively, were rated using generalized Labeled Magnitude Scales (gLMS). The method, namely 20% relative standard deviation (RSD), was developed for the classification of an individual’s sensitivity. The results of ordinal multinomial logistic regression showed that the sensitivity to bitterness could be partly predicted by the sensitivity to saltiness, as well as the heat and pungency sensations. Furthermore, it was found that threshold should be used in conjunction with suprathreshold intensity ratings for classifying individuals. These findings regarding panelist sensitivity will be most useful in sensory evaluations of pungent food and in large-scale consumer studies.
... However, whether these differences between sexes are reflected in the number of FP is still unclear and several studies failed to find a significant effect of gender 8,15,[28][29][30][31][32][33][34] . On the contrary, other recent large-scale studies reported that women consistently having a higher number of FP in respect to men 9,10 , and Piochi and colleagues 35 hypothesized that males and females may differ in the number of FP having specific diameters. ...
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 quantification of fungiform papillae (FP) has also been used to infer taste sensitivity. However, there is a concern related to using this method, as recent studies involving large population samples concluded that FP density does not directly correlate to taste sensitivity [24][25][26]. ...
This study investigates the relationships between basic tastes and fattiness sensitivity and food liking in 11-year-old children. The basic taste sensitivity of 106 children was measured using different methods, namely detection (DT) and recognition (RT) thresholds, and taste responsiveness. Caffeine and quinine (bitter), sucrose (sweet), citric acid (sour), sodium chloride (salty), and monosodium glutamate (umami) were investigated for DT and RT at five concentrations in water solutions. In addition, taste responsiveness and liking were collected for the high-intensity concentrations. PROP (6-n-propylthiouracil) responsiveness was tested on paper strips. Fattiness sensitivity was measured by a paired comparison method using milk samples with varying fat content. Liking for 30 food items was recorded using a food-list questionnaire. The test was completed in a gamified "taste detective" approach. The results show that DT correlates with RT for all tastes while responsiveness to PROP correlates with overall taste responsiveness. Caffeine and quinine differ in bitterness responsiveness and liking. Girls have significantly lower DTs than boys for bitterness and sweetness. Food liking is driven by taste and fattiness properties, while fatty food liking is significantly influenced by fattiness sensitivity. These results contribute to a better holistic understanding of taste and fattiness sensitivity in connection to food liking in preadolescents.
... Prior to tasting, subjects were instructed in the use of the gLMS scale. "The strongest imaginable sensation of any kind" was defined as the most intense sensation that involves remembered/imagined sensations in any sensory modality, including nonoral sensations, such as loudness, oral pain/irritation, or sight (e.g. the loudest sound ever heard, the most intense pain experienced, or the brightest light ever seen) (Piochi et al., 2019;Piochi, Cabrino, Morini, & Torri, 2020). Between samples, a rinsing procedure was implemented. ...
This work aims to present a multidisciplinary approach that combines methodologies from economic anthropology and sensory science to valorise non-timber forest products; this is performed by using Kenyan forest honey as a case study to foster a positive alignment between producers and consumers living in the target market. Firstly, ethnographic research was carried out in Kenya to analyse the core competences of the forest honey producers (n = 20) and to select honey samples for the sensory evaluation. Secondly, a consumer test was performed in Italy to investigate the perception of the sensory properties by using a rate-all-that-apply test and its hedonic responses for six forest honeys by subjects living in Italy (n = 50).
Based on the producers’ perceptions of the definition of the harvesting area and the floral origin of the honeys, an indigenous classification was outlined. The key core competences of the producers centred around the traditional method of production. The harvesting area was determinant in the preference of the interviewees, being forest honeys produced from the nectar of indigenous melliferous species, from which originate the most appreciated products. Similarly, results from the consumer test showed that harvesting area and the floral origin influenced the hedonic response. Moreover, the drivers of liking (e.g. intense colour, clear appearance, smoked flavour) and disliking (e.g., granularity, opaque appearance) were identified.
The paper suggests a development trajectory that promotes the commercial potential of local production but preserves the heritage thereof. The approach is potentially applicable to all marginalised food products and facilitates a promising prospective for sustainable development.
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.
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.
Excessive salt in the diet can pose significant health risks and, therefore, the reduction of salt derived from food is an important issue relating to human nutrition and health. Furthermore, the perception of saltiness will be different among people when considering their innate sensitivity, gender, age, psychological traits and dietary habits. In this study, 31 younger participants and 29 older participants were used as research subjects. A web-based questionnaire survey was used to collect information regarding of socio-demographics, consumption frequency and liking for salty and pungent food, as well as personality traits throughout the younger and the older participants. In addition, the 6-n-propylthiouracil (PROP) ratings were tested by generalized Labeled Magnitude Scale (gLMS) in the laboratory conditions. Two-alternative forced choice (2-AFC) method was used to test the sensitivity differences in the saltiness of NaCl and the pungent sensation elicited by Sichuan pepper oleoresin between the younger and older groups. The results showed significant differences in the liking for pungent food, consumption frequency of salty food, life satisfaction, negative affect, sensation seeking and PROP ratings between the younger and older groups (p<0.05). Moreover, except for the detection threshold of saltiness, thresholds were significantly lower in the younger group than in the older group. The saltiness recognition threshold and salty intensity in the presence of pungent carriers were further analyzed by using the 2-AFC and 15 cm linear scale methods. Interestingly, the results showed that the saltiness recognition threshold decreased in the presence of the sub-threshold pungency solution, while, the salty intensity was promoted in both the younger and older groups when exposed to the slightly pungent solution (0.106 g Sichuan pepper oleoresin /L water solutions) compared to the control (spring water). For the younger group, the percentage enhancement of the salty intensity was between 9.3% and 12.5 % (p<0.05), while, at the concentration of 4.05 g/L, the salty-increasing percentage increased by 6.4% in the older group (p<0.05). In addition, the percentage reduction of NaCl reached a level of up to 34.4% in the younger group and was 4.4% in the older group (p<0.05). The Partial Least Squares Regression (PLSR) method was used to further analyze the relationship between the individual physical and psychological factors, and the percentage change in salty intensity. The results indicated that the percentage change in salty intensity increased when the detection threshold of saltiness, the sensation seeking ratings and PROP ratings increased. On the contrary, the change decreased when the age, life satisfaction ratings, detection threshold of pungency and consumption frequency of salty food increased. These findings not only provide new information for the flavor design of salt-reduced food and dishes, but also be valuable to public health as well as economic benefits.
Despite considerable research investigating the role of PROP bitterness perception and variation of fungiform papillae density (FPD) in food perception, this relationship remains controversial as well as the association between the two phenotypes. Data from 1119 subjects (38.6% male; 18-60 years) enrolled in the Italian Taste project were analysed. Responsiveness to the bitterness of PROP was assessed on the general Labelled Magnitude Scale. FPD 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 gLMS. Four foods had tastants added to produce four 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). Females gave ratings to PROP and showed FPD that were significantly higher than males. Both phenotype markers significantly decreased with age. No significant correlations were found between PROP ratings and FPD. FPD variation doesn't affect perceived intensity of solutions. Responsiveness to PROP positively correlated to perceived intensity of most stimuli in solution. A significant effect of FPD on perceived intensity of target sensation in foods was found in a few cases. Responsiveness to PROP positively affected all taste intensities in subjects with low FPD while there were no significant effects of PROP in high FPD subjects. These data highlight a complex interplay between PROP status and FPD and the need of a critical reconsideration of their role in food perception and acceptability.
Fungiform papillae on human tongue are the proxy structures designated to oral stimuli detection and transduction. However, the role of their density (fungiform papillae/cm2) in explaining oral sensitivity is still controversial. While early studies generally found that the responsiveness to oral stimuli increased as the number of papillae increased, recent large-scale studies failed to confirm this finding.The present paper reviews relevant studies dealing with the relationship between fungiform papillae density and responsiveness to oral sensations including: fundamental tastes, 6-n-propyl-2-thiouracil (PROP) and sensations from trigeminal stimulation.Manual methods and automated methods for papillae detection and quantification are reviewed and their advantages and limitations highlighted. The main factors affecting fungiform papillae density and functionality (age, gender, pathologic impairments) are also considered. Possible bias related to methodological issues in counting technique (equipment used, area and location of the tongue to count, procedures to validate the count), population sample (demographics) and sensory response collection (threshold or supra-threshold stimuli, intensity scaling) are illustrated.The lack of information related to the variability in taste pores density and the possible impairments due to nerve damages, may obscure the relationship between FPD and oral responsiveness.
Determination of the number of fungiform papillae (FP) on the human tongue is an important measure that has frequently been associated with individual differences in oral perception, including taste sensitivity. At present, there is no standardised method consistently used to identify the number of FP, and primarily scientists manually count papillae over a small region(s) of the anterior tip of a stained tongue. In this study, a rapid automated method was developed to quantify the number of FP across the anterior 2cm of an unstained tongue from high resolution digital images. In 60 participants, the automated method was validated against traditional manual counting, and then used to assess the relationship between the number of FP and taste phenotype (both 6-n-propylthiouracil (PROP) and Thermal Taster Status). FP count on the anterior 2cm of the tongue was found to correlate significantly with PROP taster status. PROP supertasters (PSTs) had a significantly higher FP count compared with PROP non-tasters (PNTs). Conversely, the common approach used to determine the number of FP in a small 6mm diameter circle on the anterior tongue tip, did not show a significant correlation irrespective of whether it was determined via automated or manual counting. The regional distribution of FP was assessed across PROP taster status groups. PSTs had a significantly higher FP count within the first centimetre of the anterior tongue compared with the PNT and PROP medium-tasters (PMT), with no significant difference in the second centimetre. No significant relationship was found with Thermal Taster Status and FP count, or interaction with PROP taster status groups, supporting previous evidence suggesting these phenomena are independent. The automated method is a valuable tool, enabling reliable quantification of FP over the anterior 2cm surface of the tongue, and overcomes subjective discrepancies in manual counting.
Background
Study results have shown that chronic exposure to cigarette smoke affects the taste function in humans. However, neither the quantitative impact on taste sensitivity nor the time-course of taste recovery on stopping smoking have been precisely examined.
Methods
The experimental design included 2 phases, (i) a case–control phase comparing the taste sensitivity level measured by Electrogustometric (EGM) thresholds from various parts of the tongue (locus) between smokers (n = 83) and non-smokers (n = 48), (ii) a follow-up study looking at the taste sensitivity recovery in smokers after smoking cessation (n = 24) and compared with non-smokers.
Results
Smokers exhibited significantly lower taste sensitivity than non-smokers - the higher the nicotine dependence (Fagerström scores), the lower the taste sensitivity. After smoking cessation, EGM thresholds decreased progressively, and reached the taste sensitivity range of non-smokers depending on locus and time. After 2 weeks a recovery could be observed on the 3 Tip and the 2 edge loci; the recovery in the posterior loci was complete after 9 weeks, and in the dorsal loci recovery was observed only after 2 months or more.
Conclusions
Smoking cessation does lead to a rapid recovery of taste sensitivity among smokers, with recovery time found to differ based on the sensitivity of loci of the tongue. The use of EGM could potentially be explored as a motivational tool for smoking cessation.
The goal of the Denver Papillae Protocol is to use a dichotomous key to define and prioritize the characteristics of fungiform papillae (FP) to ensure consistent scoring between scorers. This protocol builds off of a need that has arisen from the last two decades of taste research using FP as a proxy for taste pore density. FP density has historically been analyzed using Miller & Reedy's 1990 characterizations of their morphology: round, stained lighter, large, and elevated. In this work, the authors forewarned that stricter definitions of FP morphology needed to be outlined. Despite this call to action, follow up literature has been scarce, with most studies continuing to cite Miller & Reedy's original work. Consequently, FP density reports have been highly variable and, combined with small sample sizes, may contribute to the discrepant conclusions on the role of FP in taste sensitivity. The Genetics of Taste Lab explored this apparent inconsistency in counting and found that scorers were individually prioritizing the importance of these characteristics differently and had no guidance for when a papilla had some, but not all, of the reported qualities of FP. The result of this subjectivity is highly variable FP counts of the same tongue image. The Denver Papillae Protocol has been developed to remedy this consequence through use of a dichotomous key that further defines and prioritizes the importance of the characteristics put forth by Miller & Reedy. The proposed method could help create a standard way to quantify FP for researchers in the field of taste and nutritional studies.
Background
There are five common, independent measures used to characterize taste function in humans: detection and recognition thresholds (DT and RT), suprathreshold intensity ratings of prototypical tastants, propylthiouracil (PROP) bitterness intensity, and fungiform papillae (FP) number.
Methods
We employed all five methods to assess taste function of 65 women (21.5 ± 4 years, BMI 22.3 ± 2.8 kg/m2). Pearson correlation coefficients were calculated between the different measures.
Results
The DT and RT were positively correlated for sweet, bitter, sour, and umami (p
Understanding the influence of taste perception on food choice has captured the interest of academics, industry, and the general public, the latter as evidenced by the extent of popular media coverage and use of the term supertaster. Supertasters are highly sensitive to the bitter tastant propylthiouracil (PROP) and its chemical relative phenylthiocarbamide. The well-researched differences in taste sensitivity to these bitter chemicals are partially controlled by variation in the TAS2R38 gene; however, this variation alone does not explain the supertaster phenomenon. It has been suggested that density of papillae, which house taste buds, may explain supertasting. To address the unresolved role of papillae, we used crowdsourcing in the museum-based Genetics of Taste Lab. This community lab is uniquely situated to attract both a large population of human subjects and host a team of citizen scientists to research population-based questions about human genetics, taste, and health. Using this model, we find that PROP bitterness is not in any way predicted by papillae density. This result holds within the whole sample, when divided into major diplotypes, and when correcting for age, sex, and genotype. Furthermore, it holds when dividing participants into oft-used taster status groups. These data argue against the use of papillae density in predicting taste sensitivity and caution against imprecise use of the term supertaster. Furthermore, it supports a growing volume of evidence that sets the stage for hypergeusia, a reconceptualization of heightened oral sensitivity that is not based solely on PROP or papillae density. Finally, our model demonstrates how community-based research can serve as a unique venue for both study participation and citizen science that makes scientific research accessible and relevant to people's everyday lives.
Taste sensitivity to PROP varies greatly among individuals and is associated with polymorphisms in the bitter receptor gene TAS2R38, and with differences in fungiform papilla density on the anterior tongue surface. Recently we showed that the PROP non-taster phenotype is strongly associated with the G variant of polymorphism rs2274333 (A/G) of the gene that controls the salivary trophic factor, gustin. The aims of this study were 1) to investigate the role of gustin gene polymorphism rs2274333 (A/G), in PROP sensitivity and fungiform papilla density and morphology, and 2) to investigate the effect of this gustin gene polymorphism on cell proliferation and metabolic activity. Sixty-four subjects were genotyped for both genes by PCR techniques, their PROP sensitivity was assessed by scaling and threshold methods, and their fungiform papilla density, diameter and morphology were determined. In vitro experiments examined cell proliferation and metabolic activity, following treatment with saliva of individuals with and without the gustin gene mutation, and with isolated protein, in the two iso-forms. Gustin and TAS2R38 genotypes were associated with PROP threshold (p=0.0001 and p=0.0042), but bitterness intensity was mostly determined by TAS2R38 genotypes (p<0.000001). Fungiform papillae densities were associated with both genotypes (p<0.014) (with a stronger effect for gustin; p=0.0006), but papilla morphology was a function of gustin alone (p<0.0012). Treatment of isolated cells with saliva from individuals with the AA form of gustin or direct application of the active iso-form of gustin protein increased cell proliferation and metabolic activity (p<0.0135). These novel findings suggest that the rs2274333 polymorphism of the gustin gene affects PROP sensitivity by acting on fungiform papilla development and maintenance, and could provide the first mechanistic explanation for why PROP super-tasters are more responsive to a broad range of oral stimuli.
The anterior region of the human tongue ceases to grow by 8–10 years of age and the posterior region at 15–16 years. This
study was conducted with 30 adults and 85 children (7–12 year olds) to determine whether the cessation of growth in the anterior
tongue coincides with the stabilization of the number and distribution of fungiform papillae (FP) on this region of the tongue.
This is important for understanding when the human sense of taste becomes adult in function. This study also aimed to determine
whether a small subpopulation of papillae could be used to predict the total number of papillae. FP were photographed and
analyzed using a digital camera. The results indicated that the number of papillae stabilized at 9–10 years of age, whereas
the distribution and growth of papillae stabilized at 11–12 years of age. One subpopulation of papillae predicted the density
of papillae on the whole anterior tongue of 7–10 year olds, whereas another was the best predictor for the older children
and adults. Overall, the population, size, and distribution of FP stabilized by 11–12 years of age, which is very close to
the age that cessation of growth of the anterior tongue occurs.
Taste is the sensory system devoted primarily to a quality check of food to be ingested. Although aided by smell and visual inspection, the final recognition and selection relies on chemoreceptive events in the mouth. Emotional states of acute pleasure or displeasure guide the selection and contribute much to our quality of life. Membrane proteins that serve as receptors for the transduction of taste have for a long time remained elusive. But screening the mass of genome sequence data that have recently become available has provided a new means to identify key receptors for bitter and sweet taste. Molecular biology has also identified receptors for salty, sour and umami taste.
The fungiform papilla is a gustatory organ that provides a specific tissue residence for taste buds on the anterior tongue. Thus, during development there must be a progressive differentiation to acquire papilla epithelium, then taste cell progenitor epithelium, and finally taste cells within the papilla apex. Arranged in rows, the patterned distribution of fungiform papillae requires molecular regulation not only to induce papillae, but also to suppress papilla formation in the between-papilla tissue. Intact sensory innervation is not required to initiate papilla development or pattern. However, members of several molecular families have now been identified with specific localization in developing papillae. These may participate in papilla development and pattern formation, and subsequently in taste progenitor and taste cell differentiation. This review focuses on development of fungiform papillae in embryonic rat and mouse. Basic morphology, cell biology and molecular phenotypes of developing papillae are reviewed. Regulatory roles for molecules in several families are presented, and a broad schema is proposed for progressive epithelial differentiation to form taste cell progenitors in parallel with the temporal course, and participation of lingual sensory innervation.
The density of fungiform papillae (FPD) on the human tongue is currently taken as index for responsiveness to oral chemosensory stimuli. Visual analysis of digital tongue picture and manual counting by trained operators represents the most popular technique for FPD assessment. Methodological issues mainly due to operator bias are considered among factors accounting for the uncertainty about the relationships between FPD and responsiveness to chemosensory stimuli.The present study describes a novel automated method to count fungiform papillae from image analysis of tongue pictures. The method was applied to tongue pictures from 133 subjects. Taking the manual count as reference method, a PLRS model was developed to predict FPD from tongue automated analysis output. FPD from manual and automated count showed the same normal distribution and comparable descriptive statistic values. Consistent subject classifications as Low and High FPD were obtained according to the median values from manual and automated count. The same results on the effect of FPD variation on taste perception were obtained both using predicted and counted values.The proposed method overcomes count uncertainties due to researcher bias in manual counting and is suited for large population studies. Additional information is provided such as FP size class distribution which would help for a better understanding of the relationships between FPD variation and taste functions.
Food choice is influenced by many interacting factors in humans. Its multidimensional and complex nature is well recognized, particularly within the sensory and consumer food science field. However, the vast majority of the studies aimed at understanding determinants of food choices, preferences, and eating behaviours are affected by important limitations: the limited number of factors that are considered at once and the sample size. Furthermore, sensory and hedonic responses to actual food stimuli, are often not included in such studies.
Chemesthesis is the stimulation of somatic sensory nerves by chemicals. These chemicals produce sensations described as spicy, piquant, pungent, cooling, buzzing, and irritating. This chapter presents an overview of the anatomy and physiology of the nose and the mouth as they relate to chemesthesis, including a description of the nerve fibers types responsible for conducting these signals and the various epithelial tissues these nerves innervate. Additionally, we discuss the contribution of taste signaling elements (T2R, α-gustducin, PLCβ2 and TRPM5) in solitary chemosensory cells and chemosensory cilia as they relate to respiratory tract irritation. Finally, a variety of experimental techniques for observing chemesthetic responses in single cells, nerves and brain regions are explored. The chapter culminates a brief discussion on the anatomical basis for the integration of chemesthesis with gustation and olfaction.
The aim of this study was to elucidate the relationship between the gustatory function and average number of taste buds per fungiform papilla (FP) in humans. Systemically healthy volunteers (n = 211), pre-operative patients with chronic otitis media (n = 79), and postoperative patients, with or without a chorda tympani nerve (CTN) severed during middle ear surgery (n = 63), were included. Confocal laser scanning microscopy was employed to observe fungiform taste buds because it allows many FP to be observed non-invasively in a short period of time. Taste buds in an average of 10 FP in the midlateral region of the tongue were counted. In total, 3,849 FP were observed in 353 subjects. The gustatory function was measured by electrogustometry (EGM). An inverse relationship was found between the gustatory function and average number of fungiform taste buds per papilla. The healthy volunteers showed a lower EGM threshold (better gustatory function) and had more taste buds than did the patients with otitis media, and the patients with otitis media showed a lower EGM threshold and had more taste buds than did postoperative patients, reflecting the severity of damage to the CTN. It was concluded that the confocal laser scanning microscope is a very useful tool for using to observe a large number of taste buds non-invasively.
There are five common, independent measures used to characterize taste function in humans: detection and recognition thresholds (DT and RT), suprathreshold intensity ratings of prototypical tastants, propylthiouracil (PROP) bitterness intensity, and fungiform papillae (FP) number. METHODS: We employed all five methods to assess taste function of 65 women (21.5 ± 4 years, BMI 22.3 ± 2.8 kg/m(2)). Pearson correlation coefficients were calculated between the different measures. RESULTS: The DT and RT were positively correlated for sweet, bitter, sour, and umami (p < 0.05), but not for salt. The DT or RT did not correlate with suprathreshold intensity ratings, except for umami (suprathreshold intensity and RT: r = -0.32, p = 0.009). FP number did not correlate with any measurement of taste function. PROP bitterness intensity ratings did not correlate with any measurement of taste function, except for suprathreshold ratings for saltiness (r = 0.26, p = 0.033). CONCLUSION: As most of the individual measures of taste function did not correlate with each other, with exception of the two threshold measures, we conclude that there are multiple perceptual phases of taste, with no single measure able to represent the sense of taste globally.
The aim of this study was to compare the distribution of taste buds in fungiform papillae (FP) and gustatory function between young and elderly age groups. Confocal laser scanning microscopy was used because it allows many FP to be observed non-invasively in a short period of time. The age of participants (n = 211) varied from 20 to 83 yr. The tip and midlateral region of the tongue were observed. Taste buds in an average of 10 FP in each area were counted. A total of 2,350 FP at the tongue tip and 2,592 FP in the midlateral region could be observed. The average number of taste buds was similar among all age groups both at the tongue tip and in the midlateral region. The taste function, measured by electrogustometry, among participants 20-29 yr of age was significantly lower than that in the other age groups; however, there was no difference among any other age groups in taste function. These results indicate that the peripheral gustatory system is well maintained anatomically and functionally in elderly people.
Taste buds are found on the tongue in 3 types of structures: the fungiform papillae, the foliate papillae, and the circumvallate
papillae. Of these, the fungiform papillae (FP) are present in the greatest numbers on the tongue, and are thought to be correlated
to the overall number of taste buds. For this reason, FP density on the tongue is often used to infer taste function, although
this has been controversial. Historically, videomicroscopy techniques were used to assess FP. More recently, advances in digital
still photography and in software have allowed the development of rapid methods for obtaining high quality images in situ.
However, these can be subject to inter-researcher variation in FP identification, and are somewhat limited in the parameters
that can be measured. Here, we describe the development of a novel, automated method to count the FP, using the TongueSim
suite of software. Advantages include the reduction in time required for image analysis, elimination of researcher bias, and
the added potential to measure characteristics such as the degree of roundness of each papilla. We envisage that such software
has a wide variety of novel research applications.
Brassicaceous vegetables (BV) have chemoprotective effects and yet consumption of BV in the UK is low. Previous studies suggest perception, liking and intake of BV are influenced by bitter taste sensitivity which this study further explores. Phenotypical taste sensitivity of 136 subjects was classified using propythiouracil (PROP) and sodium chloride and fungiform papillae density (FPD) was measured from tongue images. Polymorphisms of TAS2R38 and gustin (CA6) genes were analysed. Liking and bitterness of four raw vegetables (two BV (broccoli and white cabbage) and two non-BV (spinach and courgette)), as well as habitual consumption, were evaluated.
There was a significant association between TAS2R38 genotype and PROP taster status (p < 0.0001) and between FPD and PROP taster status (p = 0.029). Individuals with greater sensitivity for PROP predominantly had TAS2R38 PAV/PAV genotype and greater FPD. BV were perceived as more bitter than non-BV (p < 0.0001) with PAV/PAV subjects perceiving significantly stronger bitter intensity. There was a significant difference in liking for the four vegetables (p = 0.002), and between consumers of different TAS2R38 genotype (p = 0.0024). Individuals with TAS2R38 AVI/AVI genotype liked BV more. Regarding intake, both PAV/PAV and AVI/AVI individuals consumed more total vegetables and BV than PAV/AVI. Although PROP nontasters tended to consume more vegetables and BV than the other two phenotype groups, liking and vegetable intake were not significantly affected by taste phenotype. Although there was not a significant effect of CA6 genotype on bitterness ratings, there was a significant interaction between CA6 and TAS2R38, and in addition CA6 genotype was significantly associated with BV intake. However, these effects require validation as the proportions of the population with the CA6 G/G genotype was extremely small (7%).
Our results confirmed that bitter taste perception in vegetables was influenced by both genotype and phenotype of bitter taste sensitivity. Moreover, our findings demonstrated that neither genotype nor phenotype of taste sensitivity alone accurately predict vegetable liking and intake as demographic factors were found to have a substantial influence.
This chapter provides sufficient knowledge on peripheral gustatory anatomy. Taste buds occur in distinct papillae of the tongue, the epithelium of the palate, oropharynx, larynx, and the upper esophagus. Lingual taste buds are found exclusively within gustatory papillae, that is, those bearing taste buds. The gustatory papillae include the vallate, foliate, and fungiform papillae. In addition to taste buds and free nerve endings, the solitary chemosensory cells (SCC) comprise another chemosensory system in vertebrates. One of the most intriguing challenges for suggesting possible functional properties of taste bud cells is to identify subsets of cells by morphological features and molecular properties, many of which can be traced even in enriched primary taste bud cell cultures. The observation that taste buds degenerate after dissection of their sensory innervation and, subsequently, reappear after regeneration of their peripheral nerves has been a major focus of research in the peripheral taste system.
The hedonic 9-point scale was designed to compare palatability among different food items; however, it has also been used occasionally to compare individuals and groups. Such comparisons can be invalid because scale labels (for example, "like extremely") can denote systematically different hedonic intensities across some groups. Addressing this problem, the hedonic general Labeled Magnitude Scale (gLMS) frames affective experience in terms of the strongest imaginable liking/disliking of any kind, which can yield valid group comparisons of food palatability provided extreme hedonic experiences are unrelated to food. For each scale, 200 panelists rated affect for remembered food products (including favorite and least favorite foods) and sampled foods; they also sampled taste stimuli (quinine, sucrose, NaCl, citric acid) and rated their intensity. Finally, subjects identified experiences representing the endpoints of the hedonic gLMS. Both scales were similar in their ability to detect within-subject hedonic differences across a range of food experiences, but group comparisons favored the hedonic gLMS. With the 9-point scale, extreme labels were strongly associated with extremes in food affect. In contrast, gLMS data showed that scale extremes referenced nonfood experiences. Perceived taste intensity significantly influenced differences in food liking/disliking (for example, those experiencing the most intense tastes, called supertasters, showed more extreme liking and disliking for their favorite and least favorite foods). Scales like the hedonic gLMS are suitable for across-group comparisons of food palatability.
This study demonstrated that individual diversities of taste sensitivity on the anterior tongue are due, in part, to variations in fungiform taste bud density. Citric acid solutions were delivered to a closed, spatially-matched (each test site was 43 mm2) flow chamber attached to the surface of the anterior tongue in 84 subjects. A two-alternative forced choice, modified staircase procedure was used to derive a detection threshold value for citric acid. The same session also included a visual analog rating procedure to scale the taste intensity judgement of five concentrations of citric acid. The taste buds within the chamber were distinguished by methylene blue stain and recorded by videomicroscopy. The sip-and-spit method was used to contrast the spatially-matched condition with whole mouth stimulation. We found that detection threshold values were inversely related to the number of fungiform taste buds, independent of gender or age. Whole-mouth threshold values determined for each subject were always well below the spatially-matched threshold values. In addition, the data demonstrated that subjects were able to scale the dynamic range of citric acid solutions. However, y-intercept approached zero intensity as the number of fungiform papillae decreased. The observed differences in citric acid sensitivity and fungiform taste bud density indicated that taste performance on the anterior tongue in humans varies, in part, with the number of taste buds.
The distribution of fungiform papillae density and associated factors were examined in the Beaver Dam Offspring Study. Data
were from 2371 participants (mean age = 48.8 years, range = 21–84 years) with 1108 males and 1263 females. Fungiform papillae
were highlighted with blue food coloring and the number of fungiform papillae within a standard 6-mm circle was counted. Whole
mouth suprathreshold taste intensity was measured. The mean fungiform papillae density was 103.5 papillae/cm2 (range = 0–212.2 papillae/cm2). For each 5-year increase in age, the mean fungiform papillae density was 2.8 papillae/cm2 lower and the mean density for males was 10.2 papillae/cm2 lower than for females. Smokers had significantly lower mean densities (former smokers: −5.1 papillae/cm2; current smokers: −9.3 papillae/cm2) than nonsmokers, and heavy alcohol drinkers had a mean density that was 4.7 papillae/cm2 lower than nonheavy drinkers. Solvent exposure was related to a significantly higher density (+6.8 papillae/cm2). The heritability estimate for fungiform papillae density was 40.2%. Propylthiouracil taster status, TAS2R38 haplotype, and perceived taste intensity were not related to density. In summary, wide variability in fungiform papillae
density was observed and a number of related factors were found including the modifiable factors of smoking and alcohol consumption.
A method developed to quantify taste buds in living human subjects to study the relationship between taste sensitivity and taste bud distribution was used to count the taste buds in 10 human subjects; fungiform papillae were mapped in 12 subjects. Taste buds were identified by staining taste pores with methylene blue, and images of the papillae and their taste pores were obtained with videomicroscopy and an image processor. Fungiform papillae showed a 3.3-fold range in density, from 22.1 to 73.6 papillae/cm 2 with an average of 41.1 ± 16.8/cm 2 (s.d., n = 2). There was a 14-fold range in taste pore density, from 36 to 511 pores/cm 2 among subjects, with an average of 193 ± 133/cm 2 (s.d., n = 10). Fungiform papillae contained from 0 to 22 taste pores, with an average per subject of 3.75 ± 1.4 taste pores/papilla (s.d., n = 10). We hypothesize that some differences in human taste sensitivity may be related to these variations in taste bud density.
The purpose of this study was to determine how bitterness, roughness, color, perceived 6-n-propylthiouracil (PROP) intensity, and fungiform papillae density affect bread liking. To accomplish this, 78 subjects rated their liking for bread samples that were manipulated to vary independently in bitterness (provided by added wheat germ extract), roughness (provided by added bleached bran), and darkness (provided by added caramel color). The bitterness from added germ extract decreased bread liking. The roughness from the bleached bran increased bread liking; this increase was larger for subjects with higher fungiform papillae densities and was larger for subjects less sensitive to PROP.Added color decreased liking for subjects who preferred refined bread, but it increased liking for subjects who preferred whole wheat bread.Research highlights► Bitterness from added germ extract decreased bread liking. ► Roughness from the bleached bran increased bread liking. ► The effect of added color on liking depended on consumers’ stated bread preference. ► Bread liking depended on both fungiform papillae density and PROP sensitivity.
Otitis media and tonsillectomy are associated with enhanced palatability of energy dense foods and with weight gain. Otitis media can damage the chorda tympani nerve (CN VII); tonsillectomy and head and neck radiation treatment can damage the glossopharyngeal nerve (CN IX). Both of these nerves function prominently in taste sensation. The present study utilizes these sources of damage to study central interactions among the nerves that mediate oral sensations. Mild damage restricted to one of these nerves can actually intensify sensations evoked from undamaged nerves (i.e., whole-mouth taste, oral tactile sensations evoked by fats and irritants). These intensifications may result from disruption of central inhibitory taste circuits, as taste damage appears to disinhibit other oral sensory nerves. In addition, mild damage restricted to one taste nerve can intensify odors perceived from foods in the mouth during chewing and swallowing (i.e., retronasal olfaction); this may be a secondary consequence of the intensification of whole-mouth taste. Damage to both nerves leads to widespread oral sensory loss. At present, the link between sensory alterations and weight gain has not been established for adults (e.g., does increased fat preference occur in individuals with oral sensory intensifications, those with losses, or both?). Finally, pain in non-oral locations is also related to taste loss. When participants rated "the most intense pain of any kind they had ever experienced," those with the greatest taste loss gave the highest ratings. These effects suggest that taste loss significantly influences long-term health outcomes.
Sensory endings of chorda tympani and lingual (trigeminal) nerve fibers were identified by selective denervation and localized within specific regions of fungiform pipillae in the hamster. The chorda tympani was resected from the middle ear and the peripheral fibers were allowed to degenerate for 1, 3, or 8 days prior to perfusion-fixation and electron-microscopic examination of the anterior tongue. Taste buds were virtually devoid of intact nerves by 3 days following chorda tympani denervation. Remnants of the fibers were restricted to taste buds. Lingual fibers, on the other hand, persist in normal numbers after chorda tympani resection and populate perigemmal areas of connective tissue and extragemmal areas located apically in the squamous, nontaste epithelium surrounding the taste bud. This study provides evidence of a segregation of chorda tympani fibers in the taste bud and lingual nerve fibers in the apical fungiform papilla. The lingual nerve-epithelial arrangement and superficial location, near the least cornified area of the tongue, may be well suited for relatively sensitive somatosensation, possibly mechanoreception. Thus, the apical fungiform papilla appears to be a site where both taste and tactile oral stimuli interact with receptors.
In the oral cavity, the food is subjected to several mechanical and chemical processes. It is fractured by the teeth, diluted and broken down by saliva, heated or cooled by the ambient temperature of the mouth, formed into a bolus and finally swallowed. Numerous receptors in the oral cavity and nose respond to the initially ingested food and monitor the changes during processing. This leads to central perceptions of taste, odor, irritation and texture of the food. Most sensations associated with food texture occur only when the food is manipulated, deformed or moved across the oral receptors. In addition, people assessing the same stimulus differ in their ratings of that stimulus and their oral physiological parameters also exhibit inter-individual variations. This paper is based on the PhD thesis of one of the authors. It gives an overview of this study and includes related work of other authors. The aim of our research was to improve the understanding of oral texture perception, in particular to examine the role of oral physiological processes in oral texture perception of semisolids and to investigate whether individual differences in perception could be attributed to differences in oral physiology among subjects. The results of our study demonstrate that oral physiological parameters such as oral sensitivity, tongue movements, temperature and saliva composition are of importance for texture perception of semisolids. Many parameters of oral physiology correlate with various perceived texture attributes. This implies that intra-individual differences in texture perception could be attributed to variations in oral physiology. Oral physiology thus plays a role in texture perception of semisolids and should be taken into account in future texture research.
Our sodium-rich food supply compels investigation of how variation in salt sensation influences liking and intake of high-sodium foods. While supertasters (those with heightened propylthiouracil (PROP) bitterness or taste papillae number) report greater saltiness from concentrated salt solutions, the non-taster/supertaster effect on sodium intake is unclear. We assessed taster effects on salt sensation, liking and intake among 87 healthy adults (45 men). PROP bitterness showed stronger associations with perceived saltiness in foods than did papillae number. Supertasters reported: greater saltiness in chips/pretzels and broth at levels comparable to regular-sodium products; greater sensory and/or liking changes to growing sodium concentration in cheeses (where sodium ions mask bitterness) and broths; and less frequently salting foods. PROP effects were attenuated in women. Compared with men, women reported more saltiness from high-sodium foods and greater liking for broth at salt levels comparable to regular-sodium products. Across men and women, Structural Equation Models showed PROP and papillae number independently explained variability in consuming high-sodium foods by impacting salt sensation and/or liking. PROP supertasters reported greater changes in sensation when more salt was added to broth, which then associated with greater changes in broth liking, and finally with more frequent high-sodium food intake. Greater papillae number was associated with less frequent high-sodium food intake via reduced liking for high-fat/high-sodium foods. In summary, variation in sensations from salt was associated with differences in hedonic responses to high-sodium foods and thus sodium intake. Despite adding less salt, PROP supertasters consumed more sodium through food, as salt was more important to preference, both for its salty taste and masking of bitterness.
The specific aim of this study is to measure the taste volume in healthy human subjects over a 2.5-month period and to demonstrate morphological changes of the peripheral taste organs.
Eighteen human taste buds in four fungiform papillae (fPap) were examined over a 10-week period. The fungiform papillae investigated were selected based on the form of the papillae or the arrangement of surface taste pores. Measurements were performed over 10 consecutive weeks, with five scans in a day once a week. The following parameters were measured: height and diameter of the taste bud, diameter of the fungiform papilla and diameter of the taste pore.
The findings of this exploratory study indicated that (1) taste bud volumes changed over a 10-week period, (2) the interval between two volume maxima within the 10-week period was 3-5 weeks, and (3) the diameter of the fPap did not correlate with the volume of a single taste bud or with the volume of all taste buds in the fPap within the 10-week period.
This exploratory in vivo study revealed changes in taste bud volumes in healthy humans with age-related gustatory sensitivity. These findings need to be considered when studying the effect of denervation of fungiform papillae in vivo using confocal microscopy.
Differences between 6-n-propylthiouracil (PROP) taster groups have long been the focus of studies on individual variation in perception of oral sensation. Recently, "thermal taste" was described, the phenomenon whereby some individuals perceive "phantom" taste sensations after thermal stimulation of small areas of the tongue. As with PROP taster status (PTS), thermal taster status (TTS) has been proposed as a proxy for general responsiveness to oral stimuli. Here we examined the influence of PTS and TTS, independently, on the perceived intensity of sweet, sour, salty, bitter, astringent, and metallic stimuli, and temperature on heating or cooling the tongue. Interactions between PTS and TTS were also examined, and fungiform papillae (FP) density and salivary flow rate (SFR) were determined. Both PTS and TTS were associated with perceived stimulus intensities. PROP super-tasters (pSTs) rated all oral stimuli as more intense than PROP non-tasters (pNTs). Thermal tasters (TTs) gave higher logged ratings than thermal non-tasters (TnTs) for all oral sensations including temperature, with the exception of metallic flavour (at low concentration) and PROP. Examination of ETA-squared values showed that PTS had a greater effect on perceived intensities than did TTS for most sensations. No PTSTTS interaction was found for any oral stimuli. In contrast with PTS, TTS was not associated with FP density, and neither PTS nor TTS were associated with SFR. We conclude that pSTs and TTs possess greater responsiveness across a range of taste and trigeminal stimuli and concentrations.
Some variations in human taste sensitivity may be due to different numbers of taste buds among subjects. Taste pores were counted on the tongue tips of 16 people with videomicroscopy, and the subjects were divided into two groups (N = 8) by the rank order of their taste bud densities. The "higher" density group averaged 374 +/- 134 taste pores/cm2, while the "lower" density group averaged 135 +/- 43 tp/cm2. The higher density group had an average fungiform papilla density which was 1.8 times greater than the lower density group and an average of 1.5 times more taste pores/papilla. The subjects also rated the intensity for 4 suprathreshold concentrations of 5 taste stimuli placed on the same region of the tongue where taste pores were counted. The group with higher taste bud densities gave significantly higher average intensity ratings for sucrose (196%), NaCl (135%) and PROP (142%), but not for citric acid (118%) and quinine HCl (110%) than the lower density group. Thus, the subjects with higher fungiform taste bud densities also reported some tastes as more intense than subjects with fewer fungiform taste buds.
Taste sensitivity is known to vary among regions of the tongue and between subjects. The distribution of taste buds on the human tongue is examined in this report to determine if interregional and intersubject variation of taste bud density might account for some of the variation in human taste sensitivity. The subjects were ten males, aged 22-80 years, who died from acute trauma or an acute cardiovascular episode. Specimens were obtained as anatomical gifts or from autopsy. A sample of tissue about 1 cm2 was taken from the tongue tip and midlateral region; frozen sections were prepared for light microscopy; and serial sections were examined by light microscopy to count the taste buds. The average taste bud (tb) density on the tongue tip was 116 tb/cm2 with a range from 3.6 to 514 among subjects. The number of gustatory papillae on the tip averaged 24.5 papillae/cm2 with a range from 2.4 to 80. Taste bud density in the midregion averaged 25.2 tb/cm2 (range: 0-85.9), and the mean number of gustatory papillae was 8.25/cm2 (range: 0-28). The mean number of taste buds per papilla was 3.8 +/- 2.2 (s.d.) on the tip and 2.6 +/- 1.5 (s.d.) on the midregion. Subjects with the highest taste bud densities on the tip also had the highest densities in the midregion and the highest number of taste buds per papilla. Taste bud density was 4.6 times higher on the tip than the midregion, which probably accounts for some of the regional difference in taste sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Fungiform taste buds in mature hamsters are less subject to neurotrophic influences than those of other species. This study evaluates taste-bud neurotrophism during development in hamsters by examining the relation between growing nerves and differentiating fungiform papillae. Chorda tympani (CT) or lingual (trigeminal) nerve (LN) fibers were labelled with Lucifer Yellow as they grew into (CT fibers) or around (LN fibers) developing taste buds. Developing fungiform papillae and taste pores were counted with the aid of a topical tongue stain.
The tongue forms on embryonic days (E) 10.5–11 and contains deeply placed CT and LN fibers but no papillae. By E12, the tongue epithelium develops scattered elevations. These “eminences” selectively become innervated by LN fibers that grow to the epithelium earlier and in larger numbers than CT fibers. Definitive fungiform papillae form rapidly during E13–14 and become heavily innervated by LN fibers. Intraepithelial CT fibers, rare at E13, invariably innervate fungiform papillae containing nascent taste buds at E14. During E14–15 (birth = E15–16), most papillae contain taste buds with pores, extensive perigemmal LN innervation, and extensive intragemmal CT innervation. At birth, numbers of fungiform papillae and taste pores are adultlike.
The results show that fungiform eminences begin forming in the absence of innervation. The subsequent differentiation of definitive fungiform papillae and their innervation by LN fibers occur synchronously, prior to the differentiation of taste buds and their CT innervation. The hamster is precocious (e.g., compared to rat) in terms of LN development and the structural maturity of the anterior tongue at birth. © Wiley-Liss, Inc.
A growing body of evidence suggests that individuals who differ in taste perception differ in lingual tactile perception. To address this issue, spatial resolution acuity was estimated for 83 young adult females (52 Asians and 31 Caucasians) by their ability to examine with the tongue and identify embossed letters of the alphabet. Ratings of the magnitude of the bitterness of 0.0032M 6-n-propylthiouracil (PROP) were obtained to characterize subjects' taste perception. The density and diameter of fungiform papillae on the anterior tongues of the Asian subjects were measured also. Subjects who rated the bitterness of PROP as very or intensely strong (supertasters) were found to be about 25% more tactually acute than subjects who rated the bitterness as moderate to strong (medium tasters) and twice as acute as subjects who rated it as nondetectable or weak (non-tasters; P<.0001): The threshold heights for letter recognition averaged 2.8, 3.5 and 5.4 mm, respectively, for the Asian subjects and 2.6, 3.2, and 5.1 mm for the Caucasian subjects. The thresholds correlated highly with subjects' ratings of bitterness (rho=-0.84, P<.0001), and for the Asian subjects with the density (rho=-0.84, P<.0001) and diameter (rho=0.66, P<.0001) of fungiform papillae. Mean densities varied from 54.4 cm(-2) (non-tasters) to 106.5 cm(-2) (medium tasters) to 143.7 cm(-2) (supertasters; P<.0001). These findings confirm that individuals who differ in taste (PROP) sensitivity also differ in lingual tactile acuity. Tactile and taste sensitivities covary and reflect individual differences in the density and diameter of fungiform papillae on the anterior tongue.
Labeled scales are commonly used for across-group comparisons. The labels consist of adjective/adverb intensity descriptors (e.g., "very strong"). The relative distances among descriptors are essentially constant but the absolute perceived intensities they denote vary with the domain to which they are applied (e.g., a "very strong" rose odor is weaker than a "very strong" headache), as if descriptors were printed on an elastic ruler that compresses or expands to fit the domain of interest. Variation in individual experience also causes the elastic ruler to compress or expand. Taste varies genetically: supertasters perceive the most intense tastes; nontasters, the weakest; and medium tasters, intermediate tastes. Taste intensity descriptors on conventional-labeled scales denote different absolute perceived intensities to the three groups making comparisons across the groups invalid. Magnitude matching provides valid comparisons by asking subjects to express tastes relative to a standard not related to taste (e.g., supertasters match tastes to louder sounds than do nontasters). Borrowing the logic of magnitude matching, we constructed a labeled scale using descriptors unrelated to taste. We reasoned that expressing tastes on a scale labeled in terms of all sensory experience might work. We generalized an existing scale, the Labeled Magnitude Scale (LMS), by placing the label "strongest imaginable sensation of any kind" at the top. One hundred subjects rated tastes and tones using the generalized LMS (gLMS) and magnitude matching. The two methods produced similar results suggesting that the gLMS is valid for taste comparisons across nontasters, medium tasters, and supertasters.
Contact endoscopy is a technique used to obtain detailed images of living epithelium in the fields of gynecology, rhinology and laryngology. Video microscopy is useful for observation of the surface of tongue papillae. In the present study, we attempted to apply the contact endoscopy technique together with video microscopy to observe tongue papillae, and to study the correlation between the condition of fungiform papillae and taste function.
Ten subjects (3 men, 7 women) were divided into two groups based on the results of a taste examination by electrogustometry. We compared the shape and blood vessels of the papillae between normal taste and taste disorder groups.
In the normal taste group, round shaped papillae and clear blood vessels were observed with both microscopy and contact endoscopy. In the taste disorder group, flat and irregular papillae were observed with microscopy. Blood vessel flow of the papillae was observed to be poor with contact endoscopy.
These findings suggested that the images of microscopy and contact endoscopy were related to taste function, and both techniques were useful for evaluating taste function.
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