Taste Modalities Research Articles

Decoding taste perception: the role of electrophysiology in taste transduction mechanisms

Taste perception is a vital sensory process that helps organisms distinguish nutrients from harmful substances. It converts chemical stimuli into electrical signals through receptors on taste receptor cells within taste buds. The five primary taste modalities—sweet, salty, sour, bitter, and umami—are mediated by distinct molecular mechanisms. G-protein-coupled receptors, such as T1R and T2R families, are responsible for sweet, umami, and bitter tastes, while ion channels like epithelial sodium channels and proton-sensitive channels govern salty and sour detection. Electrophysiological techniques like patch-clamp recordings, multi-electrode arrays, and voltage-sensitive imaging have provided insights into the electrical properties of taste cells, neurotransmitter release, and neural coding models. Recent advancements in optogenetics, microfluidic devices, and nanoelectrode arrays have refined our understanding of taste transduction at the cellular and network levels. This review highlights key findings in the electrophysiology of taste, focusing on progress in understanding peripheral and central taste processing. It also discusses emerging technologies and future directions that could further advance the field and address ongoing questions about taste perception.

Computational screening of umami tastants using deep learning.

Umami, a fundamental human taste modality, refers to the savory flavors in meats and broths, often associated with monosodium glutamate and protein richness. With limited knowledge of umami molecules, the food industry seeks efficient approaches for identifying novel tastants. In this study, we have devised a virtual screening pipeline for identifying highly potent umami tastants from large molecular databases. We curated the most extensive classification dataset containing 439 umami and 428 non-umami molecules and trained a transformer-based architecture to differentiate between the two classes, achieving 93% accuracy. Additionally, we built a neural network model for predicting the potency of umami compounds, the first effort of its kind. The classification and potency prediction models were combined with similarity analysis and toxicity screening to build an end-to-end virtual framework for the rational discovery of novel tastants. We applied this framework to the FooDB database containing around 70,000 molecules as an illustrative use case for screening potent umami compounds. The screened molecules were validated using molecular docking with the umami taste receptor. This study demonstrates the potential of data-driven methods in discovering new tastants from structural and chemical features of molecules and proposes an efficient implementation for industrial applications.

Bitter peptide prediction using graph neural networks

Bitter taste is an unpleasant taste modality that affects food consumption. Bitter peptides are generated during enzymatic processes that produce functional, bioactive protein hydrolysates or during the aging process of fermented products such as cheese, soybean protein, and wine. Understanding the underlying peptide sequences responsible for bitter taste can pave the way for more efficient identification of these peptides. This paper presents BitterPep-GCN, a feature-agnostic graph convolution network for bitter peptide prediction. The graph-based model learns the embedding of amino acids in the bitter peptide sequences and uses mixed pooling for bitter classification. BitterPep-GCN was benchmarked using BTP640, a publicly available bitter peptide dataset. The latent peptide embeddings generated by the trained model were used to analyze the activity of sequence motifs responsible for the bitter taste of the peptides. Particularly, we calculated the activity for individual amino acids and dipeptide, tripeptide, and tetrapeptide sequence motifs present in the peptides. Our analyses pinpoint specific amino acids, such as F, G, P, and R, as well as sequence motifs, notably tripeptide and tetrapeptide motifs containing FF, as key bitter signatures in peptides. This work not only provides a new predictor of bitter taste for a more efficient identification of bitter peptides in various food products but also gives a hint into the molecular basis of bitterness.Scientific ContributionOur work provides the first application of Graph Neural Networks for the prediction of peptide bitter taste. The best-developed model, BitterPep-GCN, learns the embedding of amino acids in the bitter peptide sequences and uses mixed pooling for bitter classification. The embeddings were used to analyze the sequence motifs responsible for the bitter taste.

A Drosophila computational brain model reveals sensorimotor processing

The recent assembly of the adult Drosophila melanogaster central brain connectome, containing more than 125,000 neurons and 50 million synaptic connections, provides a template for examining sensory processing throughout the brain1,2. Here we create a leaky integrate-and-fire computational model of the entire Drosophila brain, on the basis of neural connectivity and neurotransmitter identity3, to study circuit properties of feeding and grooming behaviours. We show that activation of sugar-sensing or water-sensing gustatory neurons in the computational model accurately predicts neurons that respond to tastes and are required for feeding initiation4. In addition, using the model to activate neurons in the feeding region of the Drosophila brain predicts those that elicit motor neuron firing5—a testable hypothesis that we validate by optogenetic activation and behavioural studies. Activating different classes of gustatory neurons in the model makes accurate predictions of how several taste modalities interact, providing circuit-level insight into aversive and appetitive taste processing. Additionally, we applied this model to mechanosensory circuits and found that computational activation of mechanosensory neurons predicts activation of a small set of neurons comprising the antennal grooming circuit, and accurately describes the circuit response upon activation of different mechanosensory subtypes6–10. Our results demonstrate that modelling brain circuits using only synapse-level connectivity and predicted neurotransmitter identity generates experimentally testable hypotheses and can describe complete sensorimotor transformations.

Connectomic analysis of taste circuits in Drosophila.

Our sense of taste is critical for regulating food consumption. The fruit fly Drosophila represents a highly tractable model to investigate mechanisms of taste processing, but taste circuits beyond sensory neurons are largely unidentified. Here, we use a whole-brain connectome to investigate the organization of Drosophila taste circuits. We trace pathways from four populations of sensory neurons that detect different taste modalities and project to the subesophageal zone (SEZ). We find that second-order taste neurons are primarily located within the SEZ and largely segregated by taste modality, whereas third-order neurons have more projections outside the SEZ and more overlap between modalities. Taste projections out of the SEZ innervate regions implicated in feeding, olfactory processing, and learning. We characterize interconnections between taste pathways, identify modality-dependent differences in taste neuron properties, and use computational simulations to relate connectivity to predicted activity. These studies provide insight into the architecture of Drosophila taste circuits.

Refinement of flavour substance intake estimates using probability of addition: A proposed method based on sales data

AbstractMost dietary intake estimates used in the regulatory risk assessment of flavouring substances assume that the flavouring substance is present in all foods at a given concentration. They do not account for the use of alternate flavouring substances for the same taste modality, nor do they consider the use of differing concentrations within a particular food category. This highly conservative assumption leads to an over‐estimation of exposure. To refine this assumption in exposure models, the probability of addition can be utilised. In this study, a methodology to estimate the probability of addition was developed, using the volume of a flavouring substance sold for flavours created for a particular food category against its total volume sold for all flavouring use. The method was trialled, as a proof of principle, using historical data sets of two test flavouring substances, benzaldehyde (a large volume/use material) and bornyl acetate (a low volume/use material), and the impact on dietary exposure assessment was assessed. The resulting exposure estimates for both flavouring substances were shown to be significantly lower than those without the incorporation of probability of addition, demonstrating that current methods are overly conservative and that the use of probability of addition provides a more realistic estimate of exposure of flavouring substances present in foods.

Tastant-receptor interactions: insights from the fruit fly.

Across species, taste provides important chemical information about potential food sources and the surrounding environment. As details about the chemicals and receptors responsible for gustation are discovered, a complex view of the taste system is emerging with significant contributions from research using the fruit fly, Drosophila melanogaster, as a model organism. In this brief review, we summarize recent advances in Drosophila gustation and their relevance to taste research more broadly. Our goal is to highlight the molecular mechanisms underlying the first step of gustatory circuits: ligand-receptor interactions in primary taste cells. After an introduction to the Drosophila taste system and how it encodes the canonical taste modalities sweet, bitter, and salty, we describe recent insights into the complex nature of carboxylic acid and amino acid detection in the context of sour and umami taste, respectively. Our analysis extends to non-canonical taste modalities including metals, fatty acids, and bacterial components, and highlights unexpected receptors and signaling pathways that have recently been identified in Drosophila taste cells. Comparing the intricate molecular and cellular underpinnings of how ligands are detected in vivo in fruit flies reveals both specific and promiscuous receptor selectivity for taste encoding. Throughout this review, we compare and contextualize these Drosophila findings with mammalian research to not only emphasize the conservation of these chemosensory systems, but to demonstrate the power of this model organism in elucidating the neurobiology of taste and feeding.

Demystifying wine expertise through the lens of imagination: Descriptions and imagery vividness across sensory modalities

For most untrained novices, talking about wine or imagining the smells and flavours of wine is difficult. Wine experts, on the other hand, have been found to have better imagery for wine, and are also more proficient in describing wine. Some scholars have suggested that imagery and language are based on similar underlying processes, but no conclusive evidence has been found regarding mental imagery and language production. In this study, we examined the relationship between imagery and language use in both novices and experts. In an online experiment, wine experts and novices were asked to imagine the colour, smell, taste and mouthfeel of wines in different situations, and were asked to rate the vividness of the imagined experience as well as describe it with words. The results show that experts differ from novices on a number of linguistic measures when describing wine, including the number of words used, the type of words used, the concreteness of those words, and the adjective to noun ratio. Similarly, imagery for wine was more vivid in wine experts compared to novices in the modalities of smell, taste, and mouthfeel, in alignment with previous work. Surprisingly, we found that no single linguistic variable significantly predicted the reported vividness of wine imagery, neither in experts nor in novices. However, the linguistic model predicted imagery vividness better using data from experts compared to novices. Taken together, these findings underscore that imagery and language are different facets of wine cognition.

Structural basis for sugar perception by Drosophila gustatory receptors.

Insects rely on a family of seven transmembrane proteins called gustatory receptors (GRs) to encode different taste modalities, such as sweet and bitter. We report structures of Drosophila sweet taste receptors GR43a and GR64a in the apo and sugar-bound states. Both GRs form tetrameric sugar-gated cation channels composed of one central pore domain (PD) and four peripheral ligand-binding domains (LBDs). Whereas GR43a is specifically activated by the monosaccharide fructose that binds to a narrow pocket in LBDs, disaccharides sucrose and maltose selectively activate GR64a by binding to a larger and flatter pocket in LBDs. Sugar binding to LBDs induces local conformational changes, which are subsequently transferred to the PD to cause channel opening. Our studies reveal a structural basis for sugar recognition and activation of GRs.

Fusion Street Food Trend in Urban Indian Cities Surpassing the Conventional Taste Modalities: Discussion and Word Cloud Analysis

Fusion Street Food Trend in Urban Indian Cities Surpassing the Conventional Taste Modalities: Discussion and Word Cloud Analysis

Labeled Hedonic Scale for the Evaluation of Sensory Perception and Acceptance of an Aromatic Myrtle Bitter Liqueur in Consumers with Chemosensory Deficits

Spices and herbs improve sensory perception and acceptance of foods in subjects with chemosensory deficits. Our study demonstrated that aromatic spices/herbs greatly influenced the sensory perception of an aromatic myrtle bitter liqueur (Mirtamaro) in consumers with olfactory and gustatory deficits. Mirtamaro was obtained by infusion of myrtle leaves/berries and a blend of Mediterranean herbs/plants. We initially evaluated differences in gustatory and olfactory perception of pure stimuli in controls (n = 158), subjects with hyposmia (n = 111 participants), and hypogeusia (n = 34). Subjects with hyposmia and hypogeusia showed a marked reduction in odor threshold, discrimination, and identification, while a noticeable compromise in the perception of basic taste modalities (bitter, salty, sour, and sweet) was detected in participants with hypogeusia. Then, in a subpopulation (n = 111) we evaluated differences in the perception of odor and taste pleasantness, intensity, and familiarity of Mirtoamaro. No significant differences emerged, by a labeled hedonic Likert-type scale, in the perception of Mirtamaro odor and taste in subjects with hyposmia and hypogeusia compared to controls. All groups described similar bitter liqueur sensory attributes, qualifying the use of aromatic herbs/plants as a strategy to enhance sensory perception and acceptance of foods in subjects with chemosensory deficits.

The effect of visual deprivation on basic taste modalities

AbstractIn this pilot study, the effects of temporary visual deprivation on sensitivity to the basic tastes in normal sighted subjects were assessed. The sip‐and‐spit method to assess taste recognition thresholds was applied. The recognition thresholds of five basic tastes were assessed in two conditions: when the participants were blindfolded and when their blindfolds were removed and their eyes were open. In the blindfolded condition, the recognition threshold for sweet taste (saccharose) was lower than in the eyes open condition (means: 2.49 g/L vs. 3.80 g/L, p = .046). For bitter taste, a similar tendency was observed, but the difference did not reach statistical significance (means: 0.11 g/L vs. 0.13 g/L, p = .078). No difference in taste recognition thresholds between these two conditions were noted for salty, sour, and umami. Thus, the impact of temporary visual deprivation on taste experience seems stronger for sweet than for other taste modalities.Practical ApplicationsOur pilot study suggests potential applications, for example, re‐evaluating sugar content in foods served in dim/dark environments, like cinemas or blind cafés where food is consumed in total darkness. The sweet taste recognition threshold for saccharose being lower by 1.3 g/L in dark surroundings than in lit environments may become an incentive for beverages/snacks/desserts producers to lower sugar content. Coco‐Cola Original Taste has 10.6 g of sugar/100 mL, and a 1‐L Coca‐Cola serving (one of the cinema‐sized beverages) contains 106 g of sugar (22 teaspoons). An appropriate reduction of sugar in such beverages should not change their taste/palatability, and may benefit consumers and producers (Valicente et al., 2023, Journal of Sensory Studies, 38(1), e12803). For instance, Coca‐Cola/Coke is produced by mixing a relevant syrup with water and adding CO2 (Coca‐Cola Original Taste/Zero Sugar/Cherry, etc.); producing an additional syrup with lower than original sugar content seems feasible for a company regularly introducing new products to the market.

Temporal patterns in taste sensitivity.

Individuals vary in their ability to taste, and some individuals are more sensitive to certain tastes than others. Taste sensitivity is a predictor of various factors, such as diet, eating behavior, appetite regulation, and overall health. Furthermore, taste sensitivity can fluctuate within an individual over short to long periods of time: for example, in daily (diurnal) cycles, monthly (menstrual) cycles (in females), and yearly (seasonal) cycles. Understanding these temporal patterns is important for understanding individual eating habits and food preferences, particularly in the context of personalized and precision nutrition. This review provides a summary of the literature on taste sensitivity patterns across 3 temporal dimensions: daily, monthly, and yearly. Good evidence for diurnal patterns has been observed for sweet taste and fat taste, although the evidence is limited to rodent studies for the latter. Obese populations showed limited variation to sweet and fat taste sensitivities over a day, with limited variation in sweet taste sensitivity being linked to insulin resistance. There were mixed observations of temporal variation in sensitivity to sour and umami tastes, and there were no patterns in sensitivity to bitter taste. Menstrual patterns in sweet taste sensitivity were consistent with patterns in food intake. Other taste modality investigations had mixed findings that had little agreement across studies. Hormonal changes in females influence taste sensitivity to some degree, although the overall patterns are unclear. Seasonal patterns have been less well studied, but there is weak evidence that sweet, salty, and bitter taste sensitivities change across seasons. Differences in seasonal taste patterns have been observed in subgroups susceptible to mental health disorders, requiring further investigation. Patterns of taste sensitivity are evident across multiple temporal dimensions, and more research is needed to determine the influence of these patterns on food intake. Dysregulation of these patterns may also be a marker of certain diseases or health conditions, warranting further investigation. Notably, the alimentary tastes (umami, fat, and carbohydrate) are underrepresented in this research area and require additional investigation.

Taste receptors influencing effective modalities in human health - A cutting edge update on TAS1R and TAS2R receptor polymorphisms in taste perception and disease risk.

Background: Taste is the characteristic sensory modality of the gustatory system associated with dietary intake. The ability of humans to perceive different tastes is predisposed by the activity of taste receptors. The expression of TAS1R family of genes enables the detection of sweetness and umaminess, whereas TAS2R enables the detection of bitterness. The varying levels of expression of these genes within different organs of the gastro-intestinal tract, regulates the metabolism of biomolecules including carbohydrates and proteins. Variations in the gene encoding for taste receptors might affect its binding affinity to tastant molecules and thereby pertain to varying degrees of sensation to taste among individuals. Aim: The goal of this review is to highlight the significant role of TAS1R and TAS2R as a potential biomarker to identify the incidence of morbidities and its probable onset. Method: We thoroughly investigated the SCOPUS, PubMed, Web of Science and Google Scholar databases for literature relating to the association between TAS1R and TAS2R receptors in highlighting the genetic variation during various health morbidities. Results: It has been shown that the abnormalities in taste perception restrain an individual from consuming the adequate amount of food. Taste receptors not only influence the dietary habits but also determine different aspects of human health and well-being. Conclusion: According to the available evidence the dietary molecules conferring varying taste modalities are observed to have therapeutic significance apart from its nutritive value. The taste associated incongruous dietary pattern is a risk factor for various morbidities including obesity, depression, hyperglyceridaemia, and cancers.

Interactions between Beer Compounds and Human Salivary Proteins: Insights toward Astringency and Bitterness Perception

Beer is one of the most consumed beverages worldwide with unique organoleptic properties. Bitterness and astringency are well-known key features and, when perceived with high intensity, could lead to beer rejection. Most studies on beer astringency and bitterness use sensory assays and fail to study the molecular events that occur inside the oral cavity responsible for those perceptions. This work focused on deepening this knowledge based on the interaction of salivary proteins (SP) and beer phenolic compounds (PCs) and their effect toward these two sensory attributes. The astringency and bitterness of four different beers were assessed by a sensory panel and were coupled to the study of the SP changes and PC profile characterization of beers. The human SP content was measured before (basal) and after each beer intake using HPLC analysis. The beers' PC content and profile were determined using Folin-Ciocalteu and LC-MS spectrometry, respectively. The results revealed a positive correlation between PCs and astringency and bitterness and a negative correlation between SP changes and these taste modalities. Overall, the results revealed that beers with higher PC content (AAL and IPA) are more astringent and bitter than beers with a lower PC content (HL and SBO). The correlation results suggested that an increase in whole SP content, under stimulation, should decrease astringency and bitterness perception. No correlation was found between the changes in specific families of SP and astringency and bitterness perception.

Isolated Insular Stroke: An Interesting Report of Two Cases.

Isolated Insular Stroke: An Interesting Report of Two Cases.

Selective integration of diverse taste inputs within a single taste modality.

A fundamental question in sensory processing is how different channels of sensory input are processed to regulate behavior. Different input channels may converge onto common downstream pathways to drive the same behaviors, or they may activate separate pathways to regulate distinct behaviors. We investigated this question in the Drosophila bitter taste system, which contains diverse bitter-sensing cells residing in different taste organs. First, we optogenetically activated subsets of bitter neurons within each organ. These subsets elicited broad and highly overlapping behavioral effects, suggesting that they converge onto common downstream pathways, but we also observed behavioral differences that argue for biased convergence. Consistent with these results, transsynaptic tracing revealed that bitter neurons in different organs connect to overlapping downstream pathways with biased connectivity. We investigated taste processing in one type of downstream bitter neuron that projects to the higher brain. These neurons integrate input from multiple organs and regulate specific taste-related behaviors. We then traced downstream circuits, providing the first glimpse into taste processing in the higher brain. Together, these results reveal that different bitter inputs are selectively integrated early in the circuit, enabling the pooling of information, while the circuit then diverges into multiple pathways that may have different roles.

Umami taste perception and preferences of the domestic cat (Felis catus), an obligate carnivore.

The domestic cat (Felis catus) is an obligate carnivore, and as such has a meat-based diet. Several studies on the taste perception of cats have been reported, indicating that their sense of taste has evolved based on their carnivorous diet. Here we propose that umami (mediated by Tas1r1-Tas1r3) is the main appetitive taste modality for the domestic cat by characterising the umami taste of a range of nucleotides, amino acids and their mixtures for cats obtained using complementary methods. We show for the first time that cats express Tas1r1 in taste papillae. The cat umami receptor responds to a range of nucleotides as agonists, with the purine nucleotides having the highest activity. Their umami receptor does not respond to any amino acids alone, however, 11 L-amino acids with a range of chemical characteristics act as enhancers in combination with a nucleotide. L-Glutamic acid and L-Aspartic acid are not active as either agonists or enhancers of the cat umami receptor due to changes in key binding residues at positions 170 and 302. Overall, cats have an appetitive behavioural response for nucleotides, L-amino acids, and their mixtures. We postulate that the renowned palatability of tuna for cats may be due, at least in part, to its specific combination of high levels of inosine monophosphate and free L-Histidine that produces a strong synergistic umami taste enhancement. These results demonstrate the critical role that the umami receptor plays in enabling cats to detect key taste compounds present in meat.

Sweet Taste Preference Status and its Association with Preference for the Four Basic Taste Modalities of Various Food

Sweetness preference is a complex sensation involving multidisciplinary fields and it has been studied extensively. However, there is still limited information on how the status of the sweet preference of individuals influences their preference for other taste modalities. Thus, this study was conducted to observe the difference in the preference for various types of foods based on the four taste modalities, with sweet taste preference (STP) status. This cross-sectional study involved 156 university students in Kelantan, Malaysia. The preference test of tea drink sweetness was determined using the hedonic test. Subjects were grouped into low, medium, and high STP according to their STP level. The preference for the taste modalities of different food groups was determined by using a questionnaire. The results indicated that the majority of subjects were in the medium STP group. Foods categorized under the sweet taste group were mostly correlated with the STP status, followed by salty and sour foods. There was no correlation (p>0.05) between STP status and bitter foods. This result agrees with the principal component analysis (PCA). Two factors were extracted from PCA, in which the first factor explained 56.41% and the second factor explained 20.45% of the variance. Sweetness is related to foods that are categorized under salty and sour tastes, but not related to bitter tastes. This study shows that sweetness preference status is associated with preference for two other basic tastes. The high STP subject not only prefers sweet foods but also favors foods from salty and sour groups.

Toward a general and interpretable umami taste predictor using a multi-objective machine learning approach

The umami taste is one of the five basic taste modalities normally linked to the protein content in food. The implementation of fast and cost-effective tools for the prediction of the umami taste of a molecule remains extremely interesting to understand the molecular basis of this taste and to effectively rationalise the production and consumption of specific foods and ingredients. However, the only examples of umami predictors available in the literature rely on the amino acid sequence of the analysed peptides, limiting the applicability of the models. In the present study, we developed a novel ML-based algorithm, named VirtuousUmami, able to predict the umami taste of a query compound starting from its SMILES representation, thus opening up the possibility of potentially using such a model on any database through a standard and more general molecular description. Herein, we have tested our model on five databases related to foods or natural compounds. The proposed tool will pave the way toward the rationalisation of the molecular features underlying the umami taste and toward the design of specific peptide-inspired compounds with specific taste properties.