Sucrose, NaCl, and citric acid suppress the metallic sensation of FeSO4

Metallic sensation is often described as unpleasant and can reduce acceptance of foods and beverages and compliance with medication. Masking and suppressing aversive sensations can help to improve acceptance of these products, with many successful strategies identified for bitterness. However, there are few studies investigating effective strategies for suppressing metallic sensation. This study aims to assess the effectiveness of mixture suppression to reduce the metallic sensation elicited from ferrous sulfate and examine whether individual differences in metallic sensation are associated with the effectiveness of suppression strategies. To achieve this, participants (n = 121) reported the intensity of suprathreshold concentrations of ferrous sulfate alone and in binary mixtures with three tastants, specifically, sucrose, citric acid, and sodium chloride. The results revealed that metallic sensation ratings were significantly lower for every binary mixture tested compared to ferrous sulfate presented in isolation. For 0.3 mM ferrous sulfate, sucrose was identified to be the most effective compound in suppressing metallic sensation, followed by citric acid and sodium chloride. For the 1.0 mM ferrous sulfate solutions, all tastants were equally effective at suppressing metallic sensation. In addition, there is a significant interaction between the perceived metallic intensity and the effectiveness of each strategy. These findings suggest that sucrose, citric acid, and sodium chloride have the potential to be effective in suppressing metallic sensation.

Sensory Flavor Profile of Split Gill Mushroom (Schizophyllum commune) Extract and Its Enhancement Effect on Taste Perception in Salt Solution and Seasoned Clear Soup

Edible mushroom has attracted increasing attention as a natural flavor enhancer. This research studied sensory flavor profiles and identified umami taste-related compounds in split gill mushroom extract (SGME) using descriptive analysis and chemical analysis, respectively. The effects of SGME on taste enhancement as perceived by trained descriptive panelists and general consumers were evaluated in salt solutions and clear chicken soups. The results showed that SGME had mushroom, bitter aromatic, dark brown, meaty, and musty flavor notes and salty and umami tastes. Glutamic acid, aspartic acids, adenosine 5'-monophosphate (5'-AMP), and guanosine 5'-monophosphate (5'-GMP) contributed to SGME's umami taste. As perceived by trained panelists, saltiness enhancement caused by SGME in aqueous solutions occurred only at relatively low salt concentrations (0.3 and 0.5%), while its umami enhancement effect was more pronounced. When SGME was added into reduced-salt seasoned clear chicken soups, it helped to enhance both the salty and umami tastes of the soups. The 20-31.25% reduced-salt soups with 12.5% of SGME were rated as salty as (p > 0.05) the control soup with regular salt content as perceived by both trained panelists and general consumers. The results suggest that SGME could be used as a natural flavor enhancer in the development of reduced-salt foods.

A Transcription Factor Etv1/Er81 Is Involved in the Differentiation of Sweet, Umami, and Sodium Taste Cells

Taste cells are maintained by continuous turnover throughout a lifetime, yet the mechanisms of taste cell differentiation, and how taste sensations remain constant despite this continuous turnover, remain poorly understood. Here, we report that a transcription factor Etv1 (also known as Er81) is involved in the differentiation of taste cells responsible for the preference for sweet, umami, and salty tastes. Molecular analyses revealed that Etv1 is expressed by a subset of taste cells that depend on Skn-1a (also known as Pou2f3) for their generation and express T1R genes (responsible for sweet and umami tastes) or Scnn1a (responsible for amiloride-sensitive salty taste). Etv1CreERT2/CreERT2 mice express Etv1 isoform(s) but not Etv1 in putative proprioceptive neurons as comparable to wild-type mice, yet lack expression of Etv1 or an isoform in taste cells. These Etv1CreERT2/CreERT2 mice have the same population of Skn-1a-dependent cells in taste buds as wild-type mice but have altered gene expression in taste cells, with regional differences. They have markedly decreased electrophysiological responses of chorda tympani nerves to sweet and umami tastes and to amiloride-sensitive salty taste evoked by sodium cation, but they have unchanged responses to bitter or sour tastes. Our data thus show that Etv1 is involved in the differentiation of the taste cells responsible for sweet, umami, and salty taste preferences.

Molecular and Cellular Mechanisms of Salt Taste

Salt taste, the taste of sodium chloride (NaCl), is mechanistically one of the most complex and puzzling among basic tastes. Sodium has essential functions in the body but causes harm in excess. Thus, animals use salt taste to ingest the right amount of salt, which fluctuates by physiological needs: typically, attraction to low salt concentrations and rejection of high salt. This concentration-valence relationship is universally observed in terrestrial animals, and research has revealed complex peripheral codes for NaCl involving multiple taste pathways of opposing valence. Sodium-dependent and -independent pathways mediate attraction and aversion to NaCl, respectively. Gustatory sensors and cells that transduce NaCl have been uncovered, along with downstream signal transduction and neurotransmission mechanisms. However, much remains unknown. This article reviews classical and recent advances in our understanding of the molecular and cellular mechanisms underlying salt taste in mammals and insects and discusses perspectives on human salt taste.

Effect of Addition of Umami and Sour Components on NaCl Taste in Humans

We investigated the effects of adding umami and sour components to the taste characteristics of NaCl (75 mM and 100 mM) using sensory evaluation. Here, we employed a mixture of 1 mM monosodium glutamate (MSG) and 0.5 mM inosine 5'-monophosphate (IMP) as the umami component and 3 mM citric acid as the sour component. We confirmed that the addition of MSG+IMP significantly enhanced the salty taste intensity of the NaCl solutions. In addition, the addition of MSG+IMP increased the total taste intensity and percentage of participants who sensed umami. The addition of citric acid increased the salty taste intensity of 100 mM NaCl. The addition of citric acid also increased the total taste intensity, a greater percentage of participants discerned a sour taste. Furthermore, we observed the taste characteristics when adding lemon flavor, which evokes sourness, to the citric acid and NaCl mixture. Although the addition of lemon flavor did not affect the salty taste intensity, the number of participants who perceived a sour taste increased compared to those given only citric acid with the NaCl, and improvement in palatability was also observed. These results suggest that the addition of MSG+IMP and citric acid complicates the taste of NaCl solutions, and that they may enhance the salty taste.

Salty and Savoury Snacks Compliance with 2016 and 2019 Sodium Content Targets-Durban Market, South Africa

South Africans consume a significantly high amount of sodium from salty snacks. The study aimed to evaluate savoury snacks (ready-to-eat savoury snacks, flavoured potato crisps and flavoured ready-to-eat, savoury snacks and potato crisps-salt and vinegar only) for compliance with the June 2016 and 2019 target date for sodium reduction as set out by the Department of Health in Regulation 214. It also looked at low-sodium claims made by the evaluated products. The study's research problem is located at the confluence of three critical trends: increasing consumption of sodium-containing salty snacks, increasing sodium-related disease burden and deaths and attempts to regulate sodium intake through regulation as a response. A total sample of 90 products belonging to the above categories was considered. Sodium content information was collected from the selected product packages. The study also applied the Association of Official Analytical Chemists' (AOAC) official method 984.27 in laboratory tests to verify low-sodium claims on the sampled products. The study showed that out of the 90 selected snacks, 26% of the snacks did not meet their 2019 targets, while 4% did not meet their 2016 targets. Fisher's exact tests showed that no snack category had a better inclination toward meeting 2019 tests than others. The laboratory tests showed that 4.4% of the products made a compliant low-sodium content claim (sodium levels below 120 mg Na/100 g), while one made a non-compliant sodium content claim. Among other things, the study recommended increased product compliance monitoring and evaluation, using standardised, rigorous sodium testing and measuring systems, using more consumer-friendly labels and consumer education on sodium labelling.

Multiple Types of Taste Disorders among Patients with COVID-19

Objective Based on the increasing incidence of smell and taste dysfunction among coronavirus disease 2019 (COVID-19) patients, such issues have been considered an early symptom of infection. However, few studies have investigated the type of taste components that are most frequently affected in COVID-19 patients. This study investigated the difference in frequencies of the types of taste component disorders among hospitalized COVID-19 patients. Methods In this retrospective, single-center, observational study, patients' background characteristics, clinical course, laboratory and radiological findings, and details on taste and/or smell disorders were collected and analyzed from medical records. Patients A total of 227 COVID-19 patients were enrolled, among whom 92 (40.5%) complained of taste disorders. Results Multiple types of taste disorders (hypogeusia/ageusia and hypersensitivity, or hypersensitivity and changing tastes) were reported in 10 patients. In particular, 23 patients reported hypersensitivity to at least 1 type of taste, and 2 patients complained of a bitter taste on consuming sweet foods. Impairment of all taste components was found in 48 patients (52.2%). The most frequent taste disorder was salty taste disorder (81 patients, 89.0%). Hypersensitivity to salty taste was most frequently observed (19 patients, 20.9%). Conclusion Patients with COVID-19 develop multiple types of taste disorders, among which salty taste disorder was the most frequent, with many patients developing hypersensitivity to salty taste. As smell and taste are subjective senses, further studies with the combined use of objective examinations will be required to confirm the findings.

Sweet, Salty, and Umami Taste Sensitivity and the Hedonic Perception of Taste Sensations in Adolescent Females with Anorexia Nervosa

OBJECTIVE

The aim of this study was to perform analysis of sensitivity to sweet, salty, and umami tastes based on three measurement methods and of the hedonic perception of taste sensations in adolescent females with anorexia nervosa (AN). The aim of the research was to confirm the results of other authors in terms of the perception of sweet and salty taste in patients with AN, and then develop knowledge about the perception of umami taste, which is still insufficiently studied.

METHOD

A total of 110 females with an age ranging from 13 to 19 years, including 50 newly diagnosed patients with a restrictive subtype of AN and 60 healthy controls participated in gustatory research involving analyses of taste perception (recognition thresholds, ability to identify the taste correctly, taste intensity, and hedonic response) applying the sip and spit method.

RESULTS

Females with AN showed reduced sensitivity to salty taste and increased sensitivity to umami taste and, more often than healthy controls, wrongly classified the taste of solutions with a low sucrose concentration. Patients with AN assessed the sodium chloride and monosodium glutamate tastes less negatively than did control participants, and they did not show differences in their hedonic assessment of sucrose.

CONCLUSIONS

The taste sensitivity alterations in females with AN demonstrated in this paper do not entail decreased hedonic assessment of taste experiences. Based on our results, we cannot consider the observed variation in taste sensitivity in patients with AN to be a factor that increases their negative attitude toward food consumption.

Piece of Cake: Coping with COVID-19

To limit the spread of coronavirus disease 2019 (COVID-19), many individuals were instructed to stay at home, and teleworking became commonplace. Meanwhile, many others were laid off or worked reduced hours, and some front line workers were required to work longer hours. Concurrently, a surge in reports of “pandemic baking” suggested a cascade effect on eating behaviors, which may be an inadvertent strategy to cope with stress. We conducted an online survey of people living in Canada or the United States (N = 680) to assess how employment change may have been experienced as stressful and linked to a shift in food choices. Regression models suggested that reduced hours and being laid off were associated with greater stress appraisals, avoidant- and emotion-focused coping responses, and negative affect. In turn, negative affect was associated with eating to cope and unhealthy snack choices, like salty or sweet treats. Our study emphasizes that under stressful conditions, such as those experienced during the COVID-19 pandemic, some coping strategies may contribute to the greater vulnerability to downstream effects, particularly those relating to eating choices and nutritional balances.

Sodium-Taste Cells Require Skn-1a for Generation and Share Molecular Features with Sweet, Umami, and Bitter Taste Cells

Taste buds are maintained via continuous turnover of taste bud cells derived from local epithelial stem cells. A transcription factor Skn-1a (also known as Pou2f3) is required for the generation of sweet, umami (savory), and bitter taste cells that commonly express TRPM5 and CALHM ion channels. Here, we demonstrate that sodium-taste cells distributed only in the anterior oral epithelia and involved in evoking salty taste also require Skn-1a for their generation. We discovered taste cells in fungiform papillae and soft palate that show similar but not identical molecular feature with sweet, umami, and bitter taste-mediated Type II cells. This novel cell population expresses Plcb2, Itpr3, Calhm3, Skn-1a, and ENaCα (also known as Scnn1a) encoding the putative amiloride-sensitive (AS) salty taste receptor but lacks Trpm5 and Gnat3 Skn-1a-deficient taste buds are predominantly composed of putative non-sensory Type I cells and sour-sensing Type III cells, whereas wild-type taste buds include Type II (i.e., sweet, umami, and bitter taste) cells and sodium-taste cells. Both Skn-1a and Calhm3-deficient mice have markedly decreased chorda tympani nerve responses to sodium chloride, and those decreased responses are attributed to the loss of the AS salty taste response. Thus, AS salty taste is mediated by Skn-1a-dependent taste cells, whereas amiloride-insensitive salty taste is mediated largely by Type III sour taste cells and partly by bitter taste cells. Our results demonstrate that Skn-1a regulates differentiation toward all types of taste cells except sour taste cells.

Salty Taste: From Transduction to Transmitter Release, Hold the Calcium

Detection of NaCl by the gustatory system is fundamental for salt intake and tissue homeostasis. Yet, signal transduction mechanisms for salty taste have remained obscure. In this issue of Neuron, Nomura et al. (2020) report that the epithelial sodium channel ENaC, which serves as the salty receptor, is co-expressed with the voltage-activated ATP release channel CALHM1/3 in a subset of taste cells and that these cells mediate amiloride-sensitive salty taste.

Kokumi Taste Active Peptides Modulate Salt and Umami Taste

Kokumi taste substances exemplified by γ-glutamyl peptides and Maillard Peptides modulate salt and umami tastes. However, the underlying mechanism for their action has not been delineated. Here, we investigated the effects of a kokumi taste active and inactive peptide fraction (500-10,000 Da) isolated from mature (FII_m) and immature (FII_im) Ganjang, a typical Korean soy sauce, on salt and umami taste responses in humans and rodents. Only FII_m (0.1-1.0%) produced a biphasic effect in rat chorda tympani (CT) taste nerve responses to lingual stimulation with 100 mM NaCl + 5 μM benzamil, a specific epithelial Na⁺ channel blocker. Both elevated temperature (42 °C) and FII_m produced synergistic effects on the NaCl + benzamil CT response. At 0.5% FII_m produced the maximum increase in rat CT response to NaCl + benzamil, and enhanced salt taste intensity in human subjects. At 2.5% FII_m enhanced rat CT response to glutamate that was equivalent to the enhancement observed with 1 mM IMP. In human subjects, 0.3% FII_m produced enhancement of umami taste. These results suggest that FII_m modulates amiloride-insensitive salt taste and umami taste at different concentration ranges in rats and humans.

Basic Taste: A Perceptual Concept

That the perceptual world of human taste is made up of four or five basic taste qualities is commonly accepted in the field of taste perception. Nevertheless, critics identify two issues that challenge this view. First, some argue that the term "basic tastes" cannot be precisely defined and, thus, is scientifically meaningless. Others accept the concept of basic tastes but believe there are many more. I argue here that it is most parsimonious to employ a perceptual definition of basic taste. I conclude that there are indeed four basic tastes (with a potential fifth) that constitute the building blocks of the human taste experience. Evidence cited includes historical writings from Chinese, Indian, and Greek cultures, ethnopharmacological research, and modern biological and psychological investigations. These perceptual "data" provide strong and convincing evidence, collected over thousands of years and from many different cultures, that the human perceptual world consists of the same basic taste qualities.

Association between taste perception and adiposity in overweight or obese older subjects with metabolic syndrome and identification of novel taste-related genes

BACKGROUND

The relation between taste perception, diet, and adiposity remains controversial. Additionally, there is a lack of knowledge on the polymorphisms influencing taste given the scarcity of genome-wide association studies (GWASs) published.

OBJECTIVES

We studied the relation between perception of the basic tastes, i.e., sweet, salty, bitter, sour, and umami (separately and jointly in a "taste score"), and anthropometric measurements in older subjects with metabolic syndrome (MetS). GWASs were undertaken to identify genes associated with basic tastes and their score.

METHODS

Taste perception was cross-sectionally determined by challenging subjects (381 older individuals with MetS) with solutions (5 concentrations) of the basic tastes with the use of standard prototypical tastants (phenylthiocarbamide and 6-n-propylthiouracil, NaCl, sucrose, monopotassium glutamate, and citric acid, for bitter, salt, sweet, umami, and sour, respectively). Taste perception intensities were expressed on a scale. A total taste score was derived.

RESULTS

The total taste score was inversely associated with body weight, body mass index, and waist circumference (P < 0.05). Subjects having a total taste score higher than or equal to the median (11 points for concentration V) were less likely to be classified as obese than subjects below the median (OR: 0.36; 95% CI: 0.22, 0.59; P < 0.001). Associations were similar, albeit less strong, for some taste qualities. In the GWASs, the highest associations were for bitter taste (rs1726866-TAS2R38, with P = 7.74 × 10-18 for phenylthiocarbamide and P = 3.96 × 10-19 for 6-n-propylthiouracil). For other tastes, several single-nucleotide polymorphisms (SNPs) exceeded the P threshold of 1 × 10-5. However, the top-ranked SNPs independently explained a low percentage of taste variability, hence their use as single proxies for the association between taste perception and adiposity is limited.

CONCLUSIONS

We found a strong inverse association between greater taste perception and body weight, body mass index, and waist circumference in older subjects with MetS and identified some taste-related SNPs. It would be advantageous to identify additional genetic proxies for taste and to develop polygenic scores. Data used in this study were derived from the clinical trial PREDIMED PLUS at baseline, registered at http://www.isrctn.com as ISRCTN89898870.

Type III Cells in Anterior Taste Fields Are More Immunohistochemically Diverse Than Those of Posterior Taste Fields in Mice

Activation of Type III cells in mammalian taste buds is implicated in the transduction of acids (sour) and salty stimuli. Several lines of evidence suggest that function of Type III cells in the anterior taste fields may differ from that of Type III cells in posterior taste fields. Underlying anatomy to support this observation is, however, scant. Most existing immunohistochemical data characterizing this cell type focus on circumvallate taste buds in the posterior tongue. Equivalent data from anterior taste fields-fungiform papillae and soft palate-are lacking. Here, we compare Type III cells in four taste fields: fungiform, soft palate, circumvallate, and foliate in terms of reactivity to four canonical markers of Type III cells: polycystic kidney disease 2-like 1 (PKD2L1), synaptosomal associated protein 25 (SNAP25), serotonin (5-HT), and glutamate decarboxylase 67 (GAD67). Our findings indicate that while PKD2L1, 5-HT, and SNAP25 are highly coincident in posterior taste fields, they diverge in anterior taste fields. In particular, a subset of taste cells expresses PKD2L1 without the synaptic markers, and a subset of SNAP25 cells lacks expression of PKD2L1. In posterior taste fields, GAD67-positive cells are a subset of PKD2L1 expressing taste cells, but anterior taste fields also contain a significant population of GAD67-only expressing cells. These differences in expression patterns may underlie the observed functional differences between anterior and posterior taste fields.

Impacts of in utero and early infant taste experiences on later taste acceptance: a systematic review

BACKGROUND

Dietary behavior exerts a critical influence on health and is the outcome of a broad range of interacting factors, including food and taste acceptance. These may be programmed in utero and during early infancy.

OBJECTIVE

We examined the hypothesis that fetuses and infants exposed to sweet, salty, sour, bitter, umami, or specific tastes show greater acceptance of that same taste later in life.

METHODS

We conducted a systematic review of the literature, using comprehensive searches and following established procedures for screening, data extraction, and quality appraisal. We used harvest plots to synthesize the evidence graphically.

RESULTS

Twenty studies comprising 38 subgroups that differed by taste, age, medium, and duration of exposure were included. Exposure to bitter and specific tastes increased the acceptance of these tastes. Studies on sweet and salty tastes showed equivocal results. Studies on sour tastes were sparse.

CONCLUSION

Our systematic review clearly shows programming of the acceptance of bitter and specific tastes. For other tastes the results were either equivocal or confined to a few number of studies that precluded us from drawing conclusions. Further research should examine the association of salty and sour taste exposures on later preferences of these tastes. Long-term studies and randomized clinical trials on each type of taste are needed.

Genetics of taste receptors

Taste receptors function as one of the interfaces between internal and external milieus. Taste receptors for sweet and umami (T1R [taste receptor, type 1]), bitter (T2R [taste receptor, type 2]), and salty (ENaC [epithelial sodium channel]) have been discovered in the recent years, but transduction mechanisms of sour taste and ENaC-independent salt taste are still poorly understood. In addition to these five main taste qualities, the taste system detects such noncanonical "tastes" as water, fat, and complex carbohydrates, but their reception mechanisms require further research. Variations in taste receptor genes between and within vertebrate species contribute to individual and species differences in taste-related behaviors. These variations are shaped by evolutionary forces and reflect species adaptations to their chemical environments and feeding ecology. Principles of drug discovery can be applied to taste receptors as targets in order to develop novel taste compounds to satisfy demand in better artificial sweeteners, enhancers of sugar and sodium taste, and blockers of bitterness of food ingredients and oral medications.

Do polymorphisms in the TAS1R1 gene contribute to broader differences in human taste intensity?

The TAS1R genes encode heterodimeric receptors that mediate umami (hTAS1R1 + hTAS1R3) and sweet (hTAS1R2 + hTAS1R3) sensations. The question of interest for this study is if TAS1R1 variation associates with differences in overall taste intensity. We leveraged an existing database of adults (n = 92, primarily European American) to test associations between 2 TAS1R1 single nucleotide polymorphisms (SNPs) (intronic rs17492553, C/T and exonic rs34160967, G/A) and intensity of 4 prototypical tastants (NaCl, sucrose, citric acid, and quinine), applied regionally to fungiform and circumvallate loci, and sampled with the whole mouth. Both SNPs were associated with modest shifts in perceived intensities across all taste qualities. Three genotype groups were represented for the intronic SNP-minor allele homozygotes (TT) averaged 40% lower intensities than did CC homozygotes for all regionally applied tastants, as well as whole-mouth NaCl and citric acid. Similar, but less pronounced, intensity differences were seen for the exonic SNP (GG homozygotes reported greater intensities than did the AA/AG group). Our predominantly European American cohort had a low frequency of AA homozygotes, which may have attenuated the SNP-related differences in perceived intensity. These preliminary findings, if replicated, could add TAS1R1 polymorphisms to the repertoire of genotypic and phenotypic markers of heightened taste sensation.

Signal transduction and information processing in mammalian taste buds

The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acid-sensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation.

Intake of ethanol, sodium chloride, sucrose, citric acid, and quinine hydrochloride solutions by mice: a genetic analysis

Mice of the 129/J (129) and C57BL/6ByJ (B6) strains and their reciprocal F1 and F2 hybrids were offered solutions of ethanol, sucrose, citric acid, quinine hydrochloride, and NaCl in two-bottle choice tests. Consistent with earlier work, the B6 mice drank more ethanol, sucrose, citric acid, and quinine hydrochloride solution and less NaCl solution than did 129 mice. Analyses of each generation's means and distributions showed that intakes of ethanol, quinine, sucrose, and NaCl were influenced by a few genes. The mode of inheritance was additive in the case of ethanol and quinine, for sucrose the genotype of the 129 strain was recessive, and for NaCl it was dominant. Citric acid intake appeared to be influenced by many genes with small effects, with the 129 genotype dominant. Correlations of sucrose consumption with ethanol and citric acid consumption were found among mice of the F2 generation, and the genetically determined component of these correlations was stronger than the component related to environmental factors. The genetically determined correlation between sucrose and ethanol intakes is consistent with the hypothesis that the higher ethanol intake by B6 mice depends, in part, on higher hedonic attractiveness of its sweet taste component.