Insights on modulators in perception of taste modalities: a review

Sweet-bitter taste interactions in binary mixtures of sweeteners: Relationship between taste receptor activities and sensory perception

This study investigated the effects of various binary sweetener mixtures on sweetness enhancement and their interactions with sweet or bitter taste receptors, focusing on sensory perception and receptor activity. Acesulfame K or saccharin was mixed with allulose, aspartame, erythritol, fructose, glucose, or sucrose to match a target sucrose sweetness. The effects of the mixtures on sweet and bitter taste receptors (in the human embryonic kidney -293 cells) and sensory taste intensities were evaluated. Sweetness enhancement at the sweet taste receptor level was observed in some cases, with several monosaccharides reducing the acesulfame K- or saccharin-induced bitter taste receptor activity. Combining acesulfame K or saccharin with any of the six sweeteners perceptually enhanced sweetness (60% ∼ 100% in 50:50 ratio), correlating with a reduction in inherent bitterness (-35% ∼ -63% in 50:50 ratio). This finding suggests that sweetness perception likely increased because the monosaccharides mitigate the activation of bitter receptors caused by high-potency sweeteners.

Isolation and Identification of Novel Taste-Modulating N2-Guanosine 5'-Monophosphate Derivatives Generated by Maillard-Type Reactions

Several compounds with taste-modulating properties have been investigated, improving the taste impression without having a pronounced intrinsic taste. The best-known representatives of umami taste-modulating compounds are ribonucleotides and their derivatives. Especially the thio derivatives showed high taste-modulating potential in structure-activity relationship investigations. Therefore, this study focuses on the formation of guanosine 5'-monophosphate derivatives consisting of Maillard-type generated compounds like the aroma-active thiols (2-methyl-3-furanthiol, 3-mercapto-2-pentanone, 2-furfurylthiol) and formaldehyde to gain insights into the potential of combinations of taste and aroma-active compounds. One literature-known (N2-(furfurylthiomethyl)-guanosine 5'-monophosphate) and three new derivatives (N2-(2-methyl-1-furylthiomethyl)-guanosine 5'-monophosphate, N2-((5-hydroxymethyl)-2-methyl-1-furylthiomethyl)-guanosine 5'-monophosphate, N2-((2-pentanon-1-yl)thiomethyl)-guanosine 5'-monophosphate) were successfully produced using green natural deep eutectic solvents and isolated, and their structures were completely elucidated. Besides the intrinsic taste properties, the kokumi and umami taste-modulating effects of the four derivatives were evaluated via psychophysical investigations, ranging from 19 to 22 μmol/L.

Progress in Multisensory Synergistic Salt Reduction

Excessive salt intake, primarily from sodium chloride prevalent in modern food processing, poses a significant public health risk associated with hypertension, cardiovascular diseases and stroke. Researchers worldwide are exploring approaches to reduce salt consumption without compromising food flavor. One promising method is to enhance salty taste perception using multisensory synergies, leveraging gustatory, olfactory, auditory, visual, tactile and trigeminal senses to decrease salt intake while preserving food taste. This review provides a comprehensive overview of salt usage in foods, mechanisms of salty taste perception and evaluation methods for saltiness. Various strategies for reducing salt consumption while maintaining food flavor are examined, with existing salt reduction methods' advantages and limitations being critically analyzed. A particular emphasis is placed on exploring the mechanisms and potential of multisensory synergy in salt reduction. Taste interactions, olfactory cues, auditory stimulation, visual appearance and tactile sensations in enhancing saltiness perception are discussed, offering insights into developing nutritious, appealing low-sodium foods. Furthermore, challenges in current research are highlighted, and future directions for effective salt reduction strategies to promote public health are proposed. This review aims to establish a scientific foundation for creating healthier, flavorful low-sodium food options that meet consumer preferences and wellness needs.

Umami Characteristics and Taste Improvement Mechanism of Meat

Taste is one of the five senses that detect vital information about what we are eating. Comprehending taste is crucial for enhancing the flavor of foodstuffs and high-protein foods like meat. Umami has global recognition as the fifth elementary taste, alongside sweetness, sourness, saltiness, and bitterness. Umami compounds are known to enhance the sensation of recognized flavors such as salty, sweet, bitter, and others. This could end up in greater food consumption by consumption by consumers. With the rising global population, meat consumption is rising and is projected to double by 2025. It is crucial to comprehend the umami mechanism of meat and meat products, identify novel compounds, and employ laboratory methodologies to gather varied information. This knowledge will aid in the development of new consumer products. Although very limited information is available on umami taste and compounds in meat through research data. This article discusses recent advancements in umami compounds in other foodstuff as well as meat to aid in designing future research and meat product development. Moreover, another objective of this review is to learn present techniques in foodstuffs to enhance umami taste and utilize that knowledge in meat products.

Suppression of sweet taste-related responses by plant-derived bioactive compounds and eating. Part I: A systematic review in humans

The taste of food plays a crucial role in determining what and how much we eat. Thus, interventions that temporarily block sweet taste receptors offer a promising approach to addressing unhealthy behaviours associated with sugary foods. However, the relationship between reduced sweet taste response and food consumption remains unclear, with contradictory findings. Certain studies suggest that a diminished perception of sweetness leads to a sense of fullness and results in reduced food intake, while others suggest the opposite effect. To shed some light, our systematic review looked into the relationship between diminished sweet taste response and food consumption by examining the effects of bioactive compounds that experimentally inhibit sweetness in healthy individuals. This review was registered in the International Prospective Register of Systematic Reviews and conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Scottish Intercollegiate Guidelines Network, and covered original papers included in Web of Science, PubMed, Scopus, Food Science Source and Food Science and technology abstracts. We identified 33 peer-reviewed English-language studies that fit the topic and met the inclusion criteria. The current literature predominantly focuses on the immediate impact of oral gymnemic acids, failing to provide preliminary evidence in support of the specific threshold hypothesis, above which food consumption decreases and below which the opposite effect occurs. Additionally, there was inconsistency in the findings regarding the short-term desire to eat following sweetness inhibition. Considering the downstream effects on energy intake and their clinical applications, further research is needed to clarify both the acute within-session effects (i.e., not wanting any more now) and the longer-term effects (i.e., deciding not to start eating) linked to oral sweet-taste-suppressing compounds.

TastePeptides-EEG: An Ensemble Model for Umami Taste Evaluation Based on Electroencephalogram and Machine Learning

In the field of food, the sensory evaluation of food still relies on the results of manual sensory evaluation, but the results of human sensory evaluation are not universal, and there is a problem of speech fraud. This work proposed an electroencephalography (EEG)-based analysis method that effectively enables the identification of umami/non-umami substances. First, the key features were extracted using percentage conversion, standardization, and significance screening, and based on these features, the top four models were selected from 19 common binary classification algorithms as submodels. Then, the support vector machine (SVM) algorithm was used to fit the outputs of these four submodels to establish TastePeptides-EEG. The validation set of the model achieved a judgment accuracy of 90.2%, and the test set achieved a judgment accuracy of 77.8%. This study discovered the frequency change of α wave in umami taste perception and found the frequency response delay phenomenon of the F/RT/C area under umami taste stimulation for the first time. The model is published at www.tastepeptides-meta.com/TastePeptides-EEG, which is convenient for relevant researchers to speed up the analysis of umami perception and provide help for the development of the next generation of brain-computer interfaces for flavor perception.

Exercise modifies fatty acid perception and metabolism

AIM

Obesity is a major public health issue, which is associated with several chronic diseases. In rodents, voluntary wheel running (VWR) is a type of exercise that influences ingestive behavior. This study aims to investigate the possible function of VWR activity in the perception of fat taste and if it mitigates the immediate effects of fatty acid (FA) ingestion.

METHODS

Male C57BL/6 mice were arbitrarily assigned to either a sedentary (SED) lifestyle or free access to a running wheel after 5 weeks of dietary regimen. Later these mice groups were used in the investigations on fat preference, metabolic tolerance, and electrophysiology. Diet-induced alterations in CD36 and GPR120 expression that are related to fat perception and the capacitative calcium signaling caused by FA in taste bud cells (TBCs) were also examined.

RESULTS

In obese groups, VWR temporarily reduced body weight, demonstrated improvement in preference scores for FA, and recovered from a deterioration in glucose homeostasis. In CD36-positive TBCs, electrophysiological investigations showed alterations in [Ca2+ ]i caused by FA. Further, in the TBCs of circumvallate papillae, there are differences in the expression of the genes CD36 and GPR120 between the active and SED controls. Obese mice also show lower incentive salience for long-chain fatty acids (LCFA) and adapted to the reward system of VWR which may lead to improved incentive salience accredited to wheel running.

CONCLUSION

In conclusion, this study provides the first evidence that VWR causes orosensory adaptations to fat and appears to alter taste preference for LCFAs.

Sex Differences in the Bitterness Perception of an Aromatic Myrtle Bitter Liqueur and Bitter Compounds

We evaluated sex differences in the perception of bitter compounds and an aromatic bitter herbal liqueur (Mirtamaro) obtained by the infusion of myrtle leaves/berries together with a mixture of Mediterranean herbs/plants as flavoring/bittering ingredients. In a healthy population (n = 231 participants), using bivariate correlations and multivariate linear regression analyses, significant sex differences emerged in quinine bitterness perception, with women showing a higher bitter taste intensity rating than men. Among all participants, 40 subjects (subpopulation) were randomly selected for the evaluation of sex differences in Mirtamaro gustatory and olfactory perception using a hedonic Likert-type scale. Women showed higher ratings in Mirtamaro aroma (odor intensity) and bitterness (taste intensity) perception than men, with a superior capacity to perceive/describe its sensory attributes. 1,8-Cineole and methyl chavicol were the main contributors to the bitter liqueur aroma. A significant correlation (r = 0.564, p < 0.01) between Mirtamaro odor pleasantness/taste pleasantness was observed in women, indicating a positive contribution of aromatic herbs to bitter taste acceptability. Moreover, a higher bitter intensity rating of 6-n-propylthiouracil was evidenced in women than men. Our results highlighted sex differences in bitter taste acuity and the role of aromatic herbs/plants in modulating bitter taste acceptance, which is useful information in the field of precision nutrition and medicine.

Genetic variation in sweet taste receptors and a mechanistic perspective on sweet and fat taste sensation in the context of obesity

Taste sensation enables humans to make nutritionally important decisions such as food preference and consumption. It functions as deterministic factors for unpropitious eating behavior, leading to overweight and obesity. The hedonistic feeling on consumption of fat and sugar-rich meals, in particular, has a negative influence on health. In addition, impairment in the taste receptors alters the downstream signaling of taste transduction pathway. Hence, genetic polymorphism in typical taste receptors is a predictor of taste sensitivity variance across individuals. The present review summarizes the effect of a single nucleotide polymorphism (SNP) in sweet taste receptors (T1R2/T1R3) on taste perception among individuals of various body mass index (BMI). Furthermore, in the context of obesity, we discussed the possibility of crosstalk between fat and sweet receptors as well as taste dysfunction in diseased individuals. In overall, a greater understanding of the physiological relationship between taste receptors, altered taste sensitivity, and genetic polymorphisms should lead to more effective obesity prevention approaches.

Investigating the Influence of Different Umami Tastants on Brain Perception via Scalp Electroencephalogram

Three types of tastants are known as perceptually associated with umami taste: monosodium glutamate (MSG), disodium succinate (WSA), and disodium inosine monophosphate (IMP). While these tastants were confirmed to be perceptually similar in a sensory study, they could be discriminated (p < 0.05) by electroencephalogram (EEG) analysis on a time scale of 5-6 s. In comparison of the EEG responses of the participants, the brain could partly distinguish (p < 0.05) between different sensory intensities of MSG, WSA, or IMP. The EEG data indicated that the brain is partially sensitive to perceiving different sensory intensities (L, low; M, medium; and H, high) of the same umami stimuli; i.e., for MSG in μV²/Hz, L, 2.473 ± 0.181; M, 3.274 ± 0.181; and H, 3.202 ± 0.181. However, brain responses of perceptually equi-umami intensities could partially be discriminated, suggesting that the brain could partially discriminate (p < 0.05) MSG, WSA, and IMP, despite similar sensory intensities. Moreover, umami tastants were also found to significantly enhance (p < 0.05) the α wave activity, with the most responsive being at 10 Hz, particularly in the frontal and parietal and occipital regions of the brain (p < 0.001). This study shows the potential of EEG to investigate brain activity triggered by umami stimuli.

Insights into the flavor perception and enhancement of sodium-reduced fermented foods: A review

Salt (sodium chloride, NaCl) is a vital ingredient in fermented foods, which affects their safety, texture, and flavor characteristics. Recently, the demand for reduced-sodium fermented foods has increased, as consumers have become more health-conscious. However, reducing sodium content in fermented foods may negatively affect flavor perception, which is a critical quality attribute of fermented foods for both the food industry and consumers. This review summarizes the role of salt in the human body and foods and its role in the flavor perception of fermented foods. Current sodium reduction strategies used in the food industry mainly include the direct stealth reduction of NaCl, substituting NaCl with other chloride salts, and structure modification of NaCl. The odor-induced saltiness enhancement, application of starter cultures, flavor enhancers, and non-thermal processing technology are potential strategies for flavor compensation of sodium-reduced fermented foods. However, reducing sodium in fermented food is challenging due to its specific role in flavor perception (e.g., promoting saltiness and volatile compound release from food matrices, inhibiting bitterness, and changing microflora structure). Therefore, multiple challenges must be addressed in order to improve the flavor of low-sodium fermented foods. Future studies should thus focus on the combination of several strategies to compensate for the deficiencies in flavor resulting from sodium reduction.

CD36 and GPR120 mediated orogustatory perception of dietary lipids and its physiological implication in the pygmy mouse Mus booduga

Fat taste perception has long been concerned in the regulation of dietary fat intake. Substantial experimental evidence defends fat as a sixth taste modality, but its allied peripheral mechanisms are not yet well established. The present study aimed to analyse the diet-induced changes in fat taste perception and its associated physiological variations in Mus booduga. Four groups of animals were used for the present study and were fed any one of the following diet; normal diet (10% fat), low-fat diet (4% fat), high-fat diet (36% fat), or high-fat diet (HFD) (36% fat) + rapeseed oil (HFRDO) (14%) for 9 weeks. The animals were then subjected to metabolic tolerance, fat preference, and conditioned taste aversion studies. Diet-induced alterations in the expression of genes associated with lipogenesis, inflammation, and fat taste (CD36 and GPR120) were analysed. Capacitative calcium signalling induced by both linoleic acid and grifolic acid in taste bud cells (TBCs) was also analysed. In result, both the HFD and HFDRO groups revealed deterioration in glucose homoeostasis and displayed decreased preference scores for fatty acids, which are associated with lower CD36 expression and increased GPR120 expression in TBCs. Furthermore, change in [Ca²⁺ ]i induced by LA was also compromised in CD36 positive TBCs along with elevated systemic inflammatory and lipidemic responses in both these obese groups. Overall, for the first time, our results support that chronic HFD feeding alters the CD36 and GPR120 mediated fat taste perception in M. booduga.

Sodium glutamate as a booster: Inducing Rhodosporidium paludigenum to enhance the inhibition of Penicillium expansum on pears

AIMS

This research sought to improve the ability of biocontrol yeast to suppress postharvest fungal disease and explore possible mechanisms of action.

METHODS AND RESULTS

The addition of 2% sodium glutamate (SG), which is edible and recognized as safe, enhances the inhibitory effect of Rhodosporidium paludigenum Fell & Tallman on Penicillium expansum in vivo and in vitro. Rhodosporidium paludigenum cells grown in medium with a final concentration of 2% SG, displayed viability under a variety of stress conditions, including sodium chloride (NaCl), calcofluor white (CFW), Congo red (CR) and sodium dodecyl sulphate (SDS). Activity and relative gene expression levels of antioxidant-related enzymes in R. paludigenum, including peroxisomal catalase (CAT), thioredoxin reductase (TrxR), glutathione peroxidase (GSH-PX), glutathione reductase (GR) and superoxide dismutase (SOD) were altered in the presence of SG. Levels of reactive oxygen species (ROS) increased in cells grown in the presence of SG as well as the content of several amino acids.

CONCLUSIONS

In the presence of 2% SG R. paludigenum inhibited P. expansum and exhibited tolerance to a number of stressful conditions which may involve the upregulation of antioxidant enzymes and amino acids.

SIGNIFICANCE AND IMPACT OF THE STUDY

The ability of culture conditions to enhance the fungal suppressive abilities of yeast has the potential to enhance the management of postharvest disease in fruit.

Mechanisms of umami taste perception: From molecular level to brain imaging

Due to unique characteristics, umami substances have gained much attention in the food industry during the past decade as potential replacers to sodium or fat to increase food palatability. Umami is not only known to increase appetite, but also to increase satiety, and hence could be used to control food intake. Therefore, it is important to understand the mechanism(s) involved in umami taste perception. This review discusses current knowledge of the mechanism(s) of umami perception from receptor level to human brain imaging. New findings regarding the molecular mechanisms for detecting umami tastes and their pathway(s), and the peripheral and central coding to umami taste are reviewed. The representation of umami in the human brain and the individual variation in detecting umami taste and associations with genotype are discussed. The presence of umami taste receptors in the gastrointestinal tract, and the interactions between the brain and gut are highlighted. The review concludes that more research is required into umami taste perception to include not only oral umami taste perception, but also the wider "whole body" signaling mechanisms, to explore the interaction between the brain and gut in response to umami perception and ingestion.

Single nucleotide polymorphism in CD36: Correlation to peptide YY levels in obese and non-obese adults

BACKGROUND & AIMS

Human beings are often driven to exhibit dietary preference according to their hedonic characteristics. Though previous studies proposed that the fat taste preference of an obese individual was associated with BMI, the perception of fat taste differs for every individual. The genetic variation among populations in taste receptor genes such as CD36 may be a contributing factor for this difference. Satiety peptides can also play a role in the regulation of fat taste perception. Generally, this hormone helps us to feel the sense of satiety.

METHODS

We have analysed the relationship among oro-gustatory perception of dietary lipids, salivary peptide-YY and genetic polymorphism in CD36. Oral fatty acid sensitivity analysis was performed by alternative forced choice method. Salivary peptide-YY concentration was analysed by ELISA and single nucleotide polymorphism (SNP) in CD36 gene was determined by Real-Time PCR experiments.

RESULTS

We observed that the SNP at rs1761667 of CD36 and oral detection threshold for linoleic acid (LA) are associated with choice of food, lipid profiles, peptide-YY as well as adiposity parameters in obese population. Obese peoples had significantly low levels of peptide YY than people with BMI less than 25. These factors possibly play a role in preference for energy rich diets, development of obesity and associated complications.

CONCLUSION

This study provides a solid foundation for understanding the alterations in the dietary fat intake and levels of peptide-YY, which are associated with polymorphism in fat taste receptor. This is the first report that shows a significant relationship between the satiety hormone level, SNP in CD36 gene and oral fat detection threshold in human subjects.

Heme as a Taste Molecule

PURPOSE OF REVIEW

The sense of taste has evolved to enable the identification of appropriate substances to consume, to acquire nutrients, and to avoid consuming potential toxins. Five basic taste classes have been recognized, although there may be others, including metallic taste, which have not been well defined. The purpose of this review was to survey available data from diverse sources to determine how much was known about the molecular basis for metallic taste.

RECENT FINDINGS

Metallic taste has been studied in the context of dysgeusia, primarily using non-heme iron as an inducer of metallic taste sensation. However, recent efforts by industry to develop plant-based meat substitutes have suggested that iron in the form of heme may be the main molecule underlying the taste of meat. Little work has been done on heme as a taste molecule. Data support a primary role for heme in metallic taste that may have evolved as part of a means to consume and preserve elemental iron for physiological needs.