Individual variation in fungiform papillae density with different sizes and relevant associations with responsiveness to oral stimuli

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.

Exploring the association between oral tactile sensitivity measures and phenotypic markers of oral responsiveness

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.

Relationship between Sensory Attributes, (Dis) Liking and Volatile Organic Composition of Gorgonzola PDO Cheese

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.

Relationship between the fungiform papillae number and dental caries in primary teeth: a cross-sectional study

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 METHODS

The 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.

RESULTS

The 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 RELEVANCE

Clinicians can start preventive treatments for caries earlier by determining the FP number for each child.

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.

Bioelectrical signal associated with sweet taste transduction in humans is a hyperpolarizing potential on the lingual epithelium

The lingual surface potential (LSP), which hyperpolarizes in response to salt and bitter stimuli, is thought to be a bioelectrical 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 bioelectrical signal associated with sweet taste transduction is a hyperpolarizing potential.

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.

Almli V. Investigating the Relationships between Basic Tastes Sensitivities, Fattiness Sensitivity, and Food Liking in 11-Year-Old Children

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.

Linking producers' and consumers' perceptions in the valorisation of non-timber forest products: An analysis of Ogiek forest honey

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.