Umami the Fifth Basic Taste: History of Studies on Receptor Mechanisms and Role as a Food Flavor

Involvement of GPR91 in the perception of the umami-like shellfish taste of succinate

Succinate is a key component of the characteristic umami-like taste of shellfish, which is similar to the umami taste elicited by glutamate, but is slightly more persistent and astringent. The taste receptors involved in the perception of succinate currently remain unknown. Therefore, we herein attempted to identify the taste receptors for succinate. We investigated whether cells heterologously expressing receptors associated with umami taste or succinate were activated by succinate and selected GPR91 as a candidate receptor. To verify the contribution of GPR91 to taste perception, the relationship between GPR91 activation and sensory activity was assessed using receptor assays and sensory evaluations. Our results suggest that the taste of succinate depends on the activation of GPR91. We propose that GPR91 functions as a gustatory receptor involved in the perception of the umami-like shellfish taste of succinate.

Thermodynamic binding properties of a novel umami octapeptide K1ADEDSLA8 and its mutational variants p.A2G, p.D5E, and p.A2G + p.D5E (BMP) in complex with the umami receptor hT1R1/hT1R3

Umami taste properties of a novel octameric peptide K1ADEDSLA8 and its mutants p.A2G, p.D5E, and BMP (KGDEESLA, beef meaty peptide) were assessed by molecular docking, and molecular dynamics (MD) (>1 μsec), MM-PBSA, and Mutational Affinity Prediction (MAP) methods. 3D-structure of the human umami taste receptor (hT1R1/hT1R3) was homology modeled and refined MD. Docking studies yielded three primary binding sites (PBS) for K1ADEDSLA8 and BMP, one on hT1R1 and two on hT1R3. Upto 1200 nsec of MD studies revealed that K1ADEDSLA8 binds only to Venus Flytrap Domains (VFTD) region of hT1R1 at high affinity (ΔGo = -11.94 kcal/mol), while BMP does not exhibit affinity towards hT1R1/hT1R3 in the absence of glutamate. MAP analysis for p.A2G (ΔGo = -7.77 kcal/mol) and p.D5E (ΔGo = -2.88 kcal/mol) strongly suggest that A2 and D5 in KA2DED5SLA increase the affinity and specificity of binding, posing great potential for the development of a novel umami peptide in future studies.

Enhancing Vietnamese Students' Acceptance of School Lunches Through Food Combination: A Cross-Over Study

BACKGROUND/OBJECTIVES

Vegetable leftovers constitute more than half of Vietnamese school lunch waste, partly due to limited ingredient variety, which may reduce meal acceptance.

METHODS

This cross-over study assessed the impact of diversifying vegetable options on intake and satisfaction among 40 students at a suburban Vietnamese primary school. Five new menus were developed by redistributing a 100 g vegetable portion into smaller servings of multiple vegetable types, combining them creatively with protein-rich foods or rice while maintaining nutritional value and cost. Students alternated between current and new menus over four weeks. Sensory evaluations using a 5-point hedonic scale and food weighing were conducted daily.

RESULTS

Most students increased vegetable intake during the new menu period. Mean intake was significantly higher with new menus (81.5 g; 95%CI: 77.1-85.9) compared to current menus (71.1 g; 95%CI: 65.2-75.1) (p < 0.001).

CONCLUSIONS

These findings demonstrate that enhancing vegetable variety in combination can significantly improve intake and sensory characteristics without additional costs. This scalable strategy offers a practical solution for schools to foster healthier eating habits among students.

Development of Vegetable Creams Enriched with Different Microalgae Species: A Study on the Physicochemical and Sensory Stability over Time

Vegetable creams are a popular food with sensory characteristics (intense color, smooth texture, rich flavor) suitable for the inclusion of microalgae ingredients. Limited examples of vegetable creams reformulation with microalgae are reported in the literature, and no research has focused on their stability. This study evaluates the quality parameters of heat-treated, high-protein vegetable creams formulated with Spirulina, Tetraselmis chui, and four different Chlorella vulgaris strains over an 8-month period. The investigation examines changes in physicochemical properties (color, moisture, consistency, pH, °Brix, syneresis), microbiological parameters, and sensory profile. Physicochemical results showed enhanced homogenization effects of microalgae, suggesting valuable technological applications. The sensory analysis highlights a general enhancement of umami and salty perception, with differences depending on the species considered. Yellow chlorellas were the least impactful in terms of flavor but require further investigation regarding their pronounced color influence. Tetraselmis chui altered the most the sensory profile with a strong fishy and shellfish flavor. Over time, color variation deserves attention since slight browning phenomena, with possible negative effects on consumer perception, were observed. Regarding sensory aspects, limited and no detrimental effects were detected over time in texture, taste, and smell. No adverse impact on shelf life was observed, suggesting applications in long-term storage foods.

Comparison of Meat Quality, Including Fatty Acid Content and Amino Acid Profile, and Transcriptome Profile among Hanwoo, Korea Black Cattle, and Jeju Black Cattle

This study aimed to compare the meat quality, including fatty acid content, amino acid profile, and transcriptome profile, among three Korean cattle breeds: Hanwoo, Korean black cattle (KBC), and Jeju black cattle (JBC). We analyzed fatty acid compositions, revealing that Hanwoo had higher levels of saturated fatty acids such as pentadecanoic acid, palmitic acid, and margaric acid than other cattle breeds. In contrast, KBC showed higher levels of linolenic acid, which is one of the omega-3 polyunsaturated fatty acids. Free amino acid profiles showed that Hanwoo and JBC had significantly higher levels of glutamic acid, glycine, and phenylalanine compared to KBC. KBC had a significantly higher arginine content, while Hanwoo had a significantly higher serine content compared to the other two breeds. Regarding constituent amino acid content, JBC had a higher glutamic acid content, which is associated with umami, and exhibited a lower level of valine, arginine, isoleucine, and phenylalanine compared to the other breeds. RNA transcriptome analysis identified key differentially expressed genes involved in lipid metabolism and energy homeostasis, including MOGAT1, ANGPTL8, and SLC38A4. Network analysis highlighted substantial differences in muscle system processes, fat cell differentiation, and other pathways between the breeds. These findings provide foundational data for genetic selection programs aimed at enhancing meat quality and offer valuable insights into preserving the unique characteristics of Korean indigenous cattle.

Key saltiness-enhancing substances in Maillard reaction products derived from chicken breast hydrolysate: Identification, saltiness-enhancing ability and mechanism

This work employs a saltiness-guided separation combined with UPLC-QTOF-MS to identify the key saltiness-enhancing substances in Maillard reaction products derived from chicken breast hydrolysate (CBH-MRPs). Thirteen compounds in the U3 fraction exhibited significant saltiness-enhancing abilities, which increased the saltiness intensity of NaCl (3 g/L) from 2.80 to 3.35-3.88. Interactions between the compounds and NaCl were evaluated using the S-curve method. The results showed that five compounds (5'-GMP, 5'-IMP, L-glutamic acid, L-lactic acid, and L-carnosine) and one compound (glutamine) exhibited synergistic and additive effects with NaCl, respectively, at tested concentrations. Notably, 5'-GMP/5'-IMP/glutamine and L-carnosine/L-lactic acid demonstrated better saltiness-enhancing abilities at their suprathreshold and subthreshold levels, respectively. Molecular docking results showed that hydrogen bonding was the key force for docking. Residues Cys475, Glu378, and Trp236 were the primary binding sites of the transmembrane channel-like protein 4 (TMC4). These results contribute to a better understanding of the saltiness modulating mechanisms of CBH-MRPs.

Spent Brewer's Yeast Lysis Enables a Best Out of Waste Approach in the Beer Industry

Yeasts have emerged as an important resource of bioactive compounds, proteins and peptides, polysaccharides and oligosaccharides, vitamin B, and polyphenols. Hundreds of thousands of tons of spent brewer's yeast with great biological value are produced globally by breweries every year. Hence, streamlining the practical application processes of the bioactive compounds recovered could close a loop in an important bioeconomy value-chain. Cell lysis is a crucial step in the recovery of bioactive compounds such as (glyco)proteins, vitamins, and polysaccharides from yeasts. Besides the soluble intracellular content rich in bioactive molecules, which is released by cell lysis, the yeast cell walls β-glucan, chitin, and mannoproteins present properties that make them good candidates for various applications such as functional food ingredients, dietary supplements, or plant biostimulants. This literature study provides an overview of the lysis methods used to valorize spent brewer's yeast. The content of yeast extracts and yeast cell walls resulting from cellular disruption of spent brewer's yeast are discussed in correlation with the biological activities of these fractions and resulting applications. This review highlights the need for a deeper investigation of molecular mechanisms to unleash the potential of spent brewer's yeast extracts and cell walls to become an important source for a variety of bioactive compounds.

Molecular characterization and computational analysis of a highly specific L-glutaminase from a marine bacterium Bacillus australimaris NIOT30

An alkaline active L-glutaminase (BALG) producing bacterium was screened and identified from seamount sediment samples of the Arabian Sea. The isolate was confirmed to be Bacillus australimaris NIOT30 based on morphological characteristics and 16 S rRNA gene sequencing. The glutaminase gene, balg was PCR amplified, cloned and expressed in E. coli BL21 (DE3) host. The molecular weight of purified BALG was estimated to be 36 kDa and the enzyme showed a specific activity of 507 ± 27 Umg-1 against L-glutamine under optimal assay conditions of pH 7.0 and temperature at 37 °C for 15 min. The enzyme showed maximum activity at pH 7 and retained 95% activity at pH 10. BALG retained a relative activity of about 82% and 45% at 45 °C and 60 °C respectively. The kinetic parameters of BALG, Km and Kcat/Km were determined to be of 210 ± 11 mM and 4.4 × 102 M s-1 respectively. Homology modeling and substrate ligand interaction studies revealed the stability of the enzyme-substrate complex. The present study highlights the characterization of a highly active L-glutaminase from B. australimaris NIOT30. Further, mutational analyses of ligand binding residues would show insights into the affinity of L-Glutaminase.

L-Glutamate Regulates Npy via the mGluR4-Ca2+-ERK1/2 Signaling Pathway in Mandarin Fish (Siniperca chuatsi)

Metabotropic glutamate receptor 4 (mGluR4) is widely regarded as an umami receptor activated by L-glutamate to exert essential functions. Numerous studies have shown that umami receptors participate in food intake regulation. However, little is known about mGluR4's role in mediating food ingestion and its possible molecular mechanism. Mandarin fish, a typical carnivorous fish, is sensitive to umami substances and is a promising vertebrate model organism for studying the umami receptor. In this study, we identified the mGluR4 gene and conducted evolutionary analyses from diverse fish species with different feeding habits. mGluR4 of mandarin fish was cloned and functionally expressed to investigate the effects of L-glutamate on mGluR4. We further explored whether the signal pathway mGluR4-Ca2+-ERK1/2 participates in the process in mandarin fish brain cells. The results suggest that L-glutamate could regulate Neuropeptide Y (Npy) via the mGluR4-Ca2+-ERK1/2 signaling pathway in mandarin fish. Our findings unveil the role of mGluR4 in feeding decisions and its possible molecular mechanisms in carnivorous fishes.

VmmScore: An umami peptide prediction and receptor matching program based on a deep learning approach

Peptides, with recognized physiological and medical implications, such as the ability to lower blood pressure and lipid levels, are central to our research on umami taste perception. This study introduces a computational strategy to tackle the challenge of identifying optimal umami receptors for these peptides. Our VmmScore algorithm includes two integral components: Mlp4Umami, a predictive module that evaluates the umami taste potential of peptides, and mm-Score, which enhances the receptor matching process through a machine learning-optimized molecular docking and scoring system. This system encompasses the optimization of docking structures, clustering of umami peptides, and a comparative analysis of docking energies across peptide clusters, streamlining the receptor identification process. Employing machine learning, our method offers a strategic approach to the intricate task of umami receptor determination. We undertook virtual screening of peptides derived from Lateolabrax japonicus, experimentally verifying the umami taste of three identified peptides and determining their corresponding receptors. This work not only advances our understanding of the mechanisms behind umami taste perception but also provides a rapid and cost-effective method for peptide screening. The source code is publicly accessible at https://github.com/heyigacu/mlp4umami/, encouraging further scientific exploration and collaborative efforts within the research community.

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.

Rapid Acidification and Off-Flavor Reduction of Pea Protein by Fermentation with Lactic Acid Bacteria and Yeasts

Pea protein is widely used as an alternative protein source in plant-based products. In the current study, we fermented pea protein to reduce off-flavor compounds, such as hexanal, and to produce a suitable fermentate for further processing. Laboratory fermentations using 5% (w/v) pea protein suspension were carried out using four selected lactic acid bacteria (LAB) strains, investigating their growth and acidification capabilities in pea protein. Rapid acidification of pea protein was achieved with Lactococcus lactis subsp. lactis strain LTH 7123. Next, this strain was co-inoculated together with either the yeasts Kluyveromyces lactis LTH 7165, Yarrowia lipolytica LTH 6056, or Kluyveromyces marxianus LTH 6039. Fermentation products of the mixed starter cultures and of the single strains were further analyzed by gas chromatography coupled with mass spectrometry to quantify selected volatile flavor compounds. Fermentation with L. lactis LTH 7123 led to an increase in compounds associated with the "beany" off-flavors of peas, including hexanal. However, significant reduction in those compounds was achieved after fermentation with Y. lipolytica LTH 6056 with or without L. lactis LTH 7123. Thus, fermentation using co-cultures of LAB and yeasts strains could prove to be a valuable method for enhancing quality attributes of pea protein-based products.

The investigation of the effects of monosodium glutamate on healthy rats and rats with STZ-induced diabetes

Monosodium glutamate (MSG, E621) is a flavor-enhancing food additive used widely in the food preparation industry and consumed regularly. It is considered that long-term consumption of MSG causes metabolic syndrome and obesity. Diabetes mellitus (DM) is a chronic metabolic disease characterized by high blood sugar, polyuria, polydipsia, and polyphagia, in which insulin secreted from pancreatic β cells is inadequate for maintaining blood glucose homeostasis. Rats were application 65 mg/kg streptozotocin (STZ) solution intraperitoneally and a diabetes model was created. For this purpose, freshly prepared STZ was injected into the peritoneum. Tumor necrosis factor-α, interleukin (IL)-10, IL-6, and IL-1β levels in STZ, MSG, and STZ + MSG groups were found to be significantly increased in inflammation parameters measured on the 28th day of administration when compared to the Control Group (p < 0.001). Also, although malondialdehyde (MDA) levels increased significantly in the STZ + MSG group when compared to the control group (p < 0.001), glutathione (GSH), and superoxide dismutase (SOD) levels were significantly decreased in the STZ, MSG, and STZ + MSG groups when compared to the control group (p < 0.001). Also, although glucose levels increased significantly in STZ and STZ + MSG at the end of the 28th day (p < 0.01), insulin levels decreased in STZ, MSG, and STZ + MSG groups when compared to the control groups (p < 0.01). As a result, it was found that STZ and MSG application significantly increased cytokine production, increased MDA, which is an oxidant parameter in pancreatic tissue, and decreased antioxidants (GSH and SOD) when compared to the control groups. It was also found that MSG disrupted the normal histological structure in pancreatic cells, and the damage was much more in both exocrine and endocrine pancreatic areas in the STZ + MSG group when compared to the STZ and MSG groups. It was considered that with the increased use of MSG, the susceptibility to DM might increase along with tissue damage significantly in diabetic groups, therefore, MSG must be used in a limited and controlled manner.

Ribonucleotides differentially modulate oral glutamate detection thresholds

The savory or umami taste of the amino acid glutamate is synergistically enhanced by the addition of the purines inosine 5'-monophosphate (IMP) and guanosine 5'-monophosphate (GMP) disodium salt. We hypothesized that the addition of purinergic ribonucleotides, along with the pyrimidine ribonucleotides, would decrease the absolute detection threshold of (increase sensitivity to) l-glutamic acid potassium salt (MPG). To test this, we measured both the absolute detection threshold of MPG alone and with a background level (3 mM) of 5 different 5'-ribonucleotides. The addition of the 3 purines IMP, GMP, and adenosine 5'-monophosphate (AMP) lowered the MPG threshold in all participants (P < 0.001), indicating they are positive modulators or enhancers of glutamate taste. The average detection threshold of MPG was 2.08 mM, and with the addition of IMP, the threshold was decreased by approximately 1.5 orders of magnitude to 0.046 mM. In contrast to the purines, the pyrimidines uridine 5'-monophosphate (UMP) and cytidine 5'-monophosphate (CMP) yielded different results. CMP reliably raised glutamate thresholds in 10 of 17 subjects, suggesting it is a negative modulator or diminisher of glutamate taste for them. The rank order of effects on increasing sensitivity to glutamate was IMP > GMP> AMP >> UMP// CMP. These data confirm that ribonucleotides are modulators of glutamate taste, with purines enhancing sensitivity and pyrimidines displaying variable and even negative modulatory effects. Our ability to detect the co-occurrence of glutamate and purines is meaningful as both are relatively high in evolutionarily important sources of nutrition, such as insects and fermented foods.

Inosine 5'- monophosphate derived umami taste intensity of beef determination by electrochemistry and chromatography

The umami sensation contributes to beef taste and acceptability. Inosine 5'- monophosphate (IMP), the most abundant 5'-ribonucleotide in meat, is known to impart an umami taste without the undesired side effects commonly associated with glutamate. Nevertheless, the investigation of IMP's role in beef flavor has thus far been overlooked. Traditional methods for detecting IMP have relied on liquid chromatography coupled with ultraviolet spectroscopy or mass spectrometry techniques. However, these methods are not practical for production settings due to the complexity and resource demands of sophisticated laboratory techniques. Alternative methods like cyclic voltammetry might offer more practical solutions for rapidly detecting IMP. The objectives of this study were to evaluate the efficiency of using electrochemistry and chromatography on differentiating beef strips spiked with different IMP contents. The IMP threshold was 0.30 mM determined by a trained panel using the Best Estimates Threshold method. Beef strip steaks of USDA Prime, Choice, and Select were spiked at 0.30 and 0.60 mM of IMP, based on green weight and an estimated moisture content of 65%. In this study, differences in the IMP content of steaks were not detected by liquid chromatography-mass spectrometry. However, the cyclic voltammetry approach differentiated IMP concentrations at 0.50 mM or above in aqueous solutions and subsequentially meat extracts from the buffered blank solutions. In conclusion, cyclic voltammetry holds potential as a rapid and effective approach for detecting IMP in beef and other meat products, offering promising applications for future research.

Identification and Verification of Novel Umami Peptides Isolated from Hybrid Sturgeon Meat (Acipenser baerii × Acipenser schrenckii)

To explore the umami mechanism in sturgeon meat, five peptides (ERRY, VRGPR, LKYPLE, VKKVFK, and YVVFKD) were isolated and identified by ultrafiltration, gel filtration chromatography, and UPLC-QTOF-MS/MS. The omission test confirmed that the five umami peptides contributed to the umami taste of sturgeon meat. Also, the peptides had the double effective role of enhancing both umami and saltiness. The threshold of ERRY was only 0.031, which exceeded most umami peptides in the last 3 years. Molecular docking results showed that five peptides could easily bind to Gly167, Ser170, and Try218 residues in T1R3 through hydrogen bonds and electrostatic interactions. Furthermore, molecular dynamics simulations indicated that hydrogen bonds and hydrophobic interactions were the main intermolecular interaction forces. This study could contribute to revealing the umami taste mechanism of sturgeon meat and provide new insights for effective screening of short umami peptides.

Application of Umami Tastants for Sodium Reduction in Food: An Evidence Analysis Center Scoping Review

BACKGROUND

Sodium chloride intake far exceeds the guidelines from health and regulatory agencies. Acknowledging the positive relationship between sodium intake and blood pressure, interest in substances that assist in sodium reduction, while contributing a savory taste such as umami, are highly investigated.

OBJECTIVE

The objective of this scoping review was to identify and characterize studies investigating umami tastants on sodium reduction in food, with the goal of informing future research.

METHODS

A literature search was conducted in Ovid MEDLINE, Ovid Embase, Ovid Cochrane Database of Systematic Reviews, EBSCO PsycInfo, PROSPERO, National Institutes of Health RePORTER, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform and completed in March 2022 to identify peer-reviewed publications among adults (18 years and older) with interventions focusing on umami tastants to reduce sodium content.

RESULTS

The literature search identified 52 studies, among which monosodium glutamate was the most studied umami tastant or food. Furthermore, most of the research on umami was represented through cross-sectional sensory studies to determine acceptability of foods with part of the original sodium chloride replaced with umami tastants. Only 1 study investigated the use of an umami tastant on overall daily sodium intake.

CONCLUSIONS

To assist individuals in adhering to sodium reduction intake goals set forth by regulatory agencies and their guiding policies, these findings indicated that additional research on umami tastants, including systematic reviews and prospective trials, is warranted. In these prospective studies, both intermediate outcomes (ie, dietary pattern changes, daily dietary intake of sodium, and blood pressure) and hard outcomes (ie, incidence of hypertension or stroke, as well as cardiovascular composite outcomes) should be considered.

Aquafeed fermentation improves dietary nutritional quality and benefits feeding behavior, meat flavor, and intestinal microbiota of Chinese mitten crab (Eriocheir sinensis)

Normally, proper fermentation can be an efficient and widely used method to improve feed quality in animal rearing; however, the studies on crustaceans, especially Eriocheir sinensis, remain limited. This study aimed to investigate whether feed fermentation could meliorate dietary nutritional value and benefit E. sinensis rearing. First, non-fermented feed (NFD) and fermented feed (FD) were produced and assessed, respectively. Then, the "Y" maze feed choice behavior test (180 times; 30 times, 6 rounds) was conducted to assess the attractiveness of these 2 feeds for crabs. Finally, a total of 80 crabs (44.10 ± 0.80 g) were randomly assigned into 2 groups with 4 replicates, and fed the experimental diets for 8 weeks to evaluate the effects of each feed on growth, antioxidant capacity, meat flavor, and intestinal microbiota. In this study, FD showed higher levels of crude protein (P < 0.01), soluble protein (P < 0.01), amino acids (P < 0.05), lactic acid (P < 0.001), and lower levels of crude fiber (P < 0.05) and antinutritional factors (agglutinin, trypsin inhibitor, glycinin, and β-conglycinin) (P < 0.001) than NFD. Additionally, FD was more attractive to crabs than NFD (P < 0.01) and it stimulated the appetite of crabs more than NFD (P < 0.05). The growth performance, feed efficiency, and digestive enzyme activity of FD-fed crabs were significantly higher than those of NFD-fed crabs (P < 0.05). The electronic sensory measurements and free amino acid profiles revealed that the FD diet had positive impacts on the meat flavor of crabs, particularly in "sweet" and "umami" tastes. Moreover, the antioxidant capacity of FD-fed crabs was significantly higher than that of NFD-fed crabs (P < 0.05). Fermented feed also affected the diversity and composition of intestinal microflora. The functional prediction of microbial communities showed that crabs fed FD had a better microecological environment in the intestine. In conclusion, the fermentation of aquafeed could be an effective approach to enhance feed quality and therefore benefit E. sinensis rearing.

Bedside Examination Technique for Taste

Taste disorders are uncommon and frequently unrecognised during neurological and even oral examinations. Nevertheless, understanding taste pathway, its disorders, as well as assessment of taste are crucial as it can reveal various oral, systemic and neurological pathologies that manifest as an alteration of taste. Multiple taste examination techniques have been described in the literature; however, certain techniques are complicated and may not be feasible. This paper describes the adoption of a relatively simple technique for taste assessment that can be performed at the bedside. The bedside detection of taste disorders will allow examiners to assign the patient for more detailed and invasive taste assessments.

Fractionation, identification and umami characteristics of flavor peptides in natural brewed soy sauce

To investigate the umami mechanisms and characteristics of soy sauce flavor peptides, four fractions from natural brewed soy sauce were separated using ultrafiltration and Sephadex G-15 gel filtration chromatography. Sensory and ligand-receptor interaction tests showed that the umami strengths of the fractions were related as follows: U1 > U2, G3 > G2, and G3 > U1. Peptide identification revealed that the < 550-Da peptides might be the major contributors to the umami taste of U1 and G3. The higher umami strength of G3 might be attributable to its higher content of umami peptides. G3's concentration-relative umami intensity curve was plotted using a two-alternative forced choice test. It was also revealed that less sourness, higher saltiness and cool (4 ℃) and hot (50 ℃) serving conditions were conductive to the umami perception of G3. The results could provide a reference for the application of soy-sauce flavor peptides in food.

Sodium Replacement with KCl and MSG: Attitudes, Perception and Acceptance in Reduced Salt Soups

Sodium intake is linked to multiple negative health outcomes, particularly hypertension, the leading cause of premature death globally. Sodium intake levels in human populations are high, due in part to our desire for palatable salty-tasting foods. Two leading salt replacement strategies are the use of potassium chloride (KCl) and monosodium glutamate (MSG), the latter of which still contains some sodium, but both of which can replace some salty taste in foods while reducing net sodium levels. In this report, we employed a trained descriptive sensory panel to optimize saltiness in sodium-reduced aqueous samples using various concentrations of KCl and MSG. Following this, we assessed consumer attitudes to sodium-reduction strategies in a model food, canned soup, known to typically be high in sodium. Finally, in a large consumer test, we verified that these optimized levels of KCl and MSG did not lead to a drop in liking for the reduced-sodium soups with saltiness subsidized in this manner. Our results showed that sodium can be readily reduced in soups by 18% while actually scoring higher in liking, and in some cases being perceived as even more salty tasting, but that consumers are more open to sodium reduction in this manner when sodium replacements are not specifically highlighted, and when percentage sodium reduction is stated over absolute levels.

Development of sensitive and stable electrochemical impedimetric biosensor based on T1R1 receptor and its application to detection of umami substances

Umami substances can provide a palatable flavour for food. In this study, an electrochemical impedimetric biosensor was developed for detecting umami substances. This biosensor was fabricated by immobilising T1R1 onto AuNPs/reduced graphene oxide/chitosan which was in advance electro-deposited onto a glassy carbon electrode. The evaluation by the electrochemical impedance spectrum method showed that the T1R1 biosensor performed well with low detection limits and wide linear ranges. Under the optimised incubation time (60 s), the electrochemical response was linearly related to the concentrations of the detected targets monosodium glutamate and inosine-5'-monophosphate within their respective linear range of 10^-14 to 10^-9 M and 10^-16 to 10^-13 M. The low detection limit of monosodium glutamate and inosine-5'-monophosphate was 10^-15 M and 10^-16 M, respectively. Moreover, the T1R1 biosensor exhibited high specificity to umami substances even in the real food sample. The developed biosensor still retained 89.24% signal intensity after 6-day storage, exhibiting a desirable storability.

Effect of monosodium glutamate on fetal development and progesterone level in pregnant Wistar Albino rats

Monosodium glutamate (MSG) is a widespread flavor enhancer and stabilizer in manufactured or packaged foods that possess myriad adverse effects. This study aimed to evaluate the effect of MSG on placental progesterone receptors and fetal development. Thirty pregnant Wistar Albino rats were divided into three groups (ten/each). The control group (G1) gavaged distilled water only, low-dose treated group (G2) gavaged 3 g/kg MSG, and high-dose treated group (G3) gavaged 6 g/kg MSG from 1st to 18th days of gestation, and all pregnant rats were sacrificed on the 19th day of gestation. The effect of MSG on fetal weights, crown vertebral length (CVL), placental weight, placental ghrelin expression, and fetal skeleton examination were estimated. MSG induced a significant decrease in fetal weights, CVL lengths, placental weight, and ghrelin expression in both treatment groups compared to the control group. Several parts of the fetal skeleton showed incomplete ossification and delayed chondrification in which high-dose maternally treated fetuses were more affected. Many degenerative changes were detected in both maternal and fetal liver and kidney tissues in MSG-treated groups. Moreover, MSG caused a significant increase in serum ALT, ALP, and creatinine levels in pregnant rats' blood. Serum progesterone was only elevated in G3 on the 19th day of gestation. This study showed that the administration of MSG during pregnancy adversely influences fetal growth and skeletal development and caused several biochemical and histological changes in the maternal and fetal liver and kidney tissues which assure the toxic and teratogenic effects of MSG.

Analysis of the Differences in Muscle Nutrition among Individuals of Different Sexes in Redclaw Crayfish, Cherax quadricarinatus

Redclaw crayfish (Cherax quadricarinatus) was introduced to China many years ago. In recent years, a breeding boom for C. quadricarinatus has been set off in China due to a breakthrough in key technology of seedling breeding. The size and growth rate of C. quadricarinatus vary greatly between female and male individuals, usually the size and growth rate of male individuals are bigger than that of female individuals. There is usually a certain linkage relationship between the sex traits of crustaceans and their own nutrition. In order to explore the linkage relationship between the sex traits of C. quadricarinatus and its nutritional components, this study measured and analyzed the muscle nutritional components of female and male individuals. The results showed that the meat yield rate of male individuals was significantly higher than that of females (p < 0.05), and the crude fat content was significantly lower than that for females (p < 0.05). The ratios of essential amino acids to total amino acids for females and males were 39.61% and 38.49%, respectively. The ratios of essential amino acids to non-essential amino acids were 79.69% and 75.66%, respectively, which far exceed FAO/WHO standards and both belong to high-quality protein. The total amount of flavor amino acids of male individuals was significantly higher than that of female individuals (p < 0.05). The total amount of polyunsaturated fatty acids and the polyunsaturated fatty acid eicosapentaenoic acid of males are both significantly higher than that of females (p < 0.05). Studies have shown that there are certain differences in nutrition between male and female individuals. Compared with female individuals, the meat yield rate, crude protein content, and edible value of the muscles of male individuals is higher.

Phytochemicals and Inflammation: Is Bitter Better?

The taste of a herb influences its use in traditional medicine. A molecular basis for the taste-based patterns ruling the distribution of herbal (ethno) pharmacological activities may not be excluded. This study investigated the potential correlations between the anti-inflammatory activity (AIA) and the phytocompound taste and/or its chemical class. The study relies on information gathered by an extensive literature (articles, books, databases) search and made public as PlantMolecularTasteDB. Out of a total of 1527 phytotastants with reliably documented taste and structure available in PlantMolecularTasteDB, 592 (for each of which at least 40 hits were found on PubMed searches) were included in the statistical analysis. A list of 1836 putative molecular targets of these phytotastants was afterwards generated with SwissTargetPrediction tool. These targets were systematically evaluated for their potential role in inflammation using an international databases search. The correlations between phytochemical taste and AIA, between chemical class and AIA, and between the taste and the number of inflammation related targets were statistically analyzed. Phytochemical taste may be a better predictor of AIA than the chemical class. Bitter phytocompounds have a higher probability of exerting AIA when compared with otherwise phytotastants. Moreover, bitter phytotastants act upon more inflammation related targets than non-bitter tasting compounds.

Crossmodal correspondences between basic tastes and visual design features: A narrative historical review

People tend to associate abstract visual features with basic taste qualities. This narrative historical review critically evaluates the literature on these associations, often referred to as crossmodal correspondences, between basic tastes and visual design features such as color hue and shape curvilinearity. The patterns, discrepancies, and evolution in the development of the research are highlighted while the mappings that have been reported to date are summarized. The review also reflects on issues of cross-cultural validity and deviations in the matching patterns that are observed when correspondences are assessed with actual tastants versus with verbal stimuli. The various theories that have been proposed to account for different classes of crossmodal correspondence are discussed, among which the statistical and affective (or emotional-mediation) accounts currently appear most promising. Several critical research questions for the future are presented to address the gaps that have been identified in the literature and help validate the popular theories on the origin and operations of visual-taste correspondences.

Behavioural Nudges, Physico-Chemical Solutions, and Sensory Strategies to Reduce People’s Salt Consumption

This narrative historical review examines the wide range of approaches that has been trialled/suggested in order to reduce the consumption of salt. While sodium is an essential micronutrient, there is widespread evidence that high levels of consumption are leading to various negative health outcomes. This review summarises the evidence relating to the various approaches that have been put forward to date to help reduce salt consumption over the years, while also highlighting a number of important questions that remains for future research. Solutions to reducing salt consumption include everything from the gradual reduction in salt in foods through to the reduction in the number/size of holes in saltshakers (what one might consider a behavioural nudge). Physico-chemical solutions have included salt replacers, such as monosodium glutamate (MSG) through to the asymmetric distribution of salt in processed (e.g., layered) foods. A wide range of sensory approaches to modulating expected and perceived saltiness have also been suggested, including the use of salty aromas, as well as suggesting the use of colour cues, sonic seasoning, and even textural primes. It is currently unclear whether different salty aromas can be combined to increase odour-induced taste enhancement (OITE) effectiveness. In the years ahead, it will be interesting to assess how long such solutions remain effective, as well as whether different solutions can be combined to help reduce salt consumption without having to compromise on taste/flavour

The soil bacterium, Corynebacterium glutamicum, from biosynthesis of value-added products to bioremediation: A master of many trades

Ever since its discovery in 1957, Corynebacterium glutamicum has become a well-established industrial strain and is known for its massive capability of producing various amino acids (like L-lysine and L-glutamate) and other value-added chemicals. With the rising demand for these bio-based products, the revelation of the whole genome sequences of the wild type strains, and the astounding advancements made in the fields of metabolic engineering and systems biology, our perspective of C. glutamicum has been revolutionized and has expanded our understanding of its strain development. With these advancements, a new era for C. glutamicum supremacy in the field of industrial biotechnology began. This led to remarkable progress in the enhancement of tailor-made over-producing strains and further development of the substrate spectrum of the bacterium, to easily accessible, economical, and renewable resources. C. glutamicum has also been metabolically engineered and used in the degradation/assimilation of highly toxic and ubiquitous environmental contaminant, arsenic, present in water or soil. Here, we review the history, current knowledge, progress, achievements, and future trends relating to the versatile metabolic factory, C. glutamicum. This review paper is devoted to C. glutamicum which is one of the leading industrial microbes, and one of the most promising and versatile candidates to be developed. It can be used not only as a platform microorganism to produce different value-added chemicals and recombinant proteins, but also as a tool for bioremediation, allowing to enhance specific properties, for example in situ bioremediation.

Characterization of Peanut Protein Hydrolysate and Structural Identification of Umami-Enhancing Peptides

Umami peptides are naturally found in various foods and have been proven to be essential components contributing to food taste. Defatted peanut powder hydrolysate produced by a multiprotease (Flavorzyme, Alcalase, and Protamex) was found to elicit an umami taste and umami-enhancing effect. The taste profiles, hydrolysis efficiency, amino acids, molecular weight distribution, Fourier transform infrared spectroscopy (FT-IR), and separation fractions obtained by ultrafiltration were evaluated. The results showed that peanut protein was extensively hydrolyzed to give mainly (up to 96.84%) free amino acids and peptides with low molecular weights (<1000 Da). Furthermore, β-sheets were the major secondary structure. Fractions of 1−3000 Da and <1000 Da prominently contributed to the umami taste and umami enhancement. To obtain umami-enhancing peptides, these two fractions were further purified by gel filtration chromatography, followed by sensory evaluation. These peptides were identified as ADSYRLP, DPLKY, EAFRVL, EFHNR, and SDLYVR by ultra-performance liquid chromatography (UPLC), and had estimated thresholds of 0.107, 0.164, 0.134, 0.148, and 0.132 mmol/L, respectively. According to the results of this work, defatted peanut powder hydrolysate had an umami taste and umami-enhancing effect, and is a potential excellent umami peptide precursor material for the food industry.

Comparative evaluation of alteration in taste perception among Gutkha chewers with and without OSMF and healthy subjects: A prospective case-control study

Context and Aim

The major afflictions such as odynophagia (painful swallowing) and trismus that occur in patients with oral submucous fibrosis (OSMF) are well documented, but the impairment of gustatory functions has not received much consideration in the past. The present study was planned with a similar intent to assess and compare the alteration in taste perception among gutkha chewers with and without OSMF and healthy subjects.

Materials and Methods

The present study was designed as a prospective case-control study comprising 90 individuals within an age range of 15-50 years who were divided into three groups with Group A consisting of 30 patients who were gutkha chewers with OSMF, Group B consisting of 30 individuals who were gutkha chewers but without OSMF and Group C consisting of 30 healthy subjects who were included as normal controls. The taste intensity response scores for the four basic tastes were recorded and the results obtained were, then, subjected to statistical analysis.

Statistical Analysis Used

The data were analyzed using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). Comparison of the said parameters was done using Chi-square test, analysis of variance and Tukey's post-hoc test. P < 0.05 was considered statistically significant.

Results

The findings of the present study suggested that all taste sensations were affected more in Group A patients than the Group B and Group C individuals.

Conclusion

The results obtained in the present study were found to be encouraging as it was demonstrated that taste perception varied significantly among the patients with OSMF as against those having habit of betel nut/gutkha chewing but those who did not develop OSMF and the normal healthy controls and this data, though, initial, might be used on a scientific basis to improve the quality of life in the affected patients as well as to prevent the further progression of the disease process.

Molecular insights into human taste perception and umami tastants: A review

Understanding taste is key for optimizing the palatability of seaweeds and other non-animal-based foods rich in protein. The lingual papillae in the mouth hold taste buds with taste receptors for the five gustatory taste qualities. Each taste bud contains three distinct cell types, of which Type II cells carry various G protein-coupled receptors that can detect sweet, bitter, or umami tastants, while type III cells detect sour, and likely salty stimuli. Upon ligand binding, receptor-linked intracellular heterotrimeric G proteins initiate a cascade of downstream events which activate the afferent nerve fibers for taste perception in the brain. The taste of amino acids depends on the hydrophobicity, size, charge, isoelectric point, chirality of the alpha carbon, and the functional groups on their side chains. The principal umami ingredient monosodium l-glutamate, broadly known as MSG, loses umami taste upon acetylation, esterification, or methylation, but is able to form flat configurations that bind well to the umami taste receptor. Ribonucleotides such as guanosine monophosphate and inosine monophosphate strongly enhance umami taste when l-glutamate is present. Ribonucleotides bind to the outer section of the venus flytrap domain of the receptor dimer and stabilize the closed conformation. Concentrations of glutamate, aspartate, arginate, and other compounds in food products may enhance saltiness and overall flavor. Umami ingredients may help to reduce the consumption of salts and fats in the general population and increase food consumption in the elderly.

Umami and Other Taste Perceptions in Patients With Parkinson's Disease

Objective

Studies of taste perceptions in Parkinson’s disease (PD) patients have been controversial, and none of these studies have assessed umami taste. This study aimed to assess umami, along with the other 4 taste functions in PD patients.

Methods

Participants were tested for gustation using the modified filter paper disc method and olfaction using the modified Sniffin’ Stick-16 (mSS-16) test (only 14 culturally suitable items were used). A questionnaire evaluated patients’ subjective olfactory and gustatory dysfunction, taste preference, appetite, and food habits.

Results

A total of 105 PD patients and 101 age- and sex-matched controls were included. The body mass index (BMI) of PD patients was lower than that of controls (PD = 22.62, controls = 23.86, p = 0.028). The mSS-16 score was 10.7 for controls and 6.4 for PD patients (p < 0.001) (normal ≥ 9). Taste recognition thresholds (RTs) for sweet, salty, sour, bitter and umami tastes were significantly higher in PD, indicating poorer gustation. All taste RTs correlated with each other, except for umami. Most patients were unaware of their dysfunction. Patients preferred sweet, salty and umami tastes more than the controls. Dysgeusia of different tastes in patients was differentially associated with poorer discrimination of tastes, an inability to identify the dish and adding extra seasoning to food. BMI and mSS-16 scores showed no correlation in either patients or controls.

Conclusion

PD patients have dysgeusia for all five tastes, including umami, which affects their appetite and diet. Patients preferred sweet, salty and umami tastes. This information can help adjust patients’ diets to improve their nutritional status.

Research progress in the screening and evaluation of umami peptides

Umami is an important element affecting food taste, and the development of umami peptides is a topic of interest in food-flavoring research. The existing technology used for traditional screening of umami peptides is time-consuming and labor-intensive, making it difficult to meet the requirements of high-throughput screening, which limits the rapid development of umami peptides. The difficulty in performing a standard measurement of umami intensity is another problem that restricts the development of umami peptides. The existing methods are not sensitive and specific, making it difficult to achieve a standard evaluation of umami taste. This review summarizes the umami receptors and umami peptides, focusing on the problems restricting the development of umami peptides, high-throughput screening, and establishment of evaluation standards. The rapid screening of umami peptides was realized based on molecular docking technology and a machine learning method, and the standard evaluation of umami could be realized with a bionic taste sensor. The progress of rapid screening and evaluation methods significantly promotes the study of umami peptides and increases its application in the seasoning industry.

Sodium Reduction in Bouillon: Targeting a Food Staple to Reduce Hypertension in Sub-saharan Africa

Bouillon cubes are a staple ingredient used in Sub-saharan African countries providing flavor enhancement to savory foods. Bouillon has been identified as a vehicle for fortification to overcome micronutrient deficiencies in Sub-saharan Africa. However, bouillon has a high sodium content (and in addition with other foods) contributes to dietary sodium intake above recommended guidelines. High dietary sodium intake is a key risk factor for hypertension and cardiovascular disease (CVD). Africa has the highest rates of hypertension and CVD globally with nearly half the adult population above 25 years affected. This review presents current state of research on sodium reduction strategies in bouillon. The key challenge is to reduce sodium levels while maintaining optimal flavor at the lowest possible production cost to ensure bouillon continues to be affordable in Sub-saharan Africa. To produce lower sodium bouillon with acceptable flavor at low cost will likely involve multiple sodium reduction strategies; direct reduction in sodium, sodium replacement and saltiness boosting flavor technologies. Efforts to reduce the sodium content of bouillon in Sub-saharan Africa is a worthwhile strategy to: (i) lower the overall sodium consumption across the population, and (ii) deliver population-wide health benefits in a region with high rates of hypertension and CVD.

Study on the distribution of umami receptors on the tongue and its signal coding logic based on taste bud biosensor

Taste signals are uniformly encoded and transmitted to the brain's taste center by taste buds, and the process has not been systematically studied for several decades. The aim of this work was to investigate the distribution of umami receptors on the tongue and its signal coding logic based on the taste bud biosensors. Taste bud biosensors were constructed by immobilizing the taste bud tissues from different tongue regions of the rabbit to the glassy carbon electrode surface; The Shennong information equations were used to analysis the pattern of umami receptors to encode ligands information; The signal amplification capabilities of two types umami receptors (T1R1/T1R3 and mGluRs) were analyzed for the two ligands (L-monosodium glutamate (MSG) and disodium 5'-inosinate (IMP)). The results showed that each taste bud biosensor could sense MSG and IMP with different response currents based on enzyme-substrate kinetics. There was only a small fraction of a great quantity of metabotropic glutamate receptors (mGluRs) could be activated to encode MSG signal. Importantly, T1R1 was more expressed in the rostral tongue cells whose sensitivity to MSG was nearly 100 times stronger than that of caudal tongue cells. The method we proposed made it possible to reveal the distribution and signals coding logic of umami receptors for ligands, which showed great potential to explain the interaction mechanism of umami substances with their receptors more accurately and to develop of artificial intelligent taste sensory.

Effect of Supplementation With Selenium-Yeast on Muscle Antioxidant Activity, Meat Quality, Fatty Acids and Amino Acids in Goats

The objective of this study was to observe the effects of selenium-yeast (SY) on growth performance, muscle antioxidant activity, meat quality, fatty acid and amino acid profiles in growing goats. A total of 18 Qianbei-pockmarked goats were assigned to three groups (six duplicates per group) by body weight (25.75 ± 1.75 kg; mean ± standard deviation) according to a completely randomized design: (1) basal diet (CON); (2) CON with 2.4 mg/kg SY (LS); and (3) CON with 4.8 mg/kg SY (HS). The results indicated that goats receiving SY did not show any differences (P &gt; 0.05) in terms of dry matter intake, growth performance, or muscle chemical composition. In addition, dietary treatment did not affect (P &gt; 0.05) the pH values (pH45min and pH24h), percentage of water loss, drip loss, or cooking loss. The HS group showed a significant increase (P &lt; 0.05) in the dressing percentage, eye muscle area and meat color, as well as muscle total antioxidant capacity, glutathione peroxidase and 2,2-diphenyl-1-picrylhydrazyl scavenging activity levels, whereas it showed a significant drop (P &lt; 0.05) in shear force and muscle malondialdehyde levels relative to the control. Feeding 4.8 mg/kg SY led to a significant (P &lt; 0.05) decrease in the levels of C8:0, C14:0, C15:0, C16:0, C17:0, C18:0, C20:0 and total saturated fatty acids, whereas it led to a significant (P &lt; 0.05) increase in C15:1 in comparison with that of the control group. Goats receiving 2.4 mg/kg SY had significantly (P &lt; 0.05) increased C16:1, C17:1, C18:1n7, C18:2n6, C18:3n3, C20:4n6, C22:1n9, and PUFA relative to the control group. Compared with the control group, the treatment groups had higher (P &lt; 0.05) levels of C18:1n9, C22:4, and monounsaturated fatty acids. The inclusion of 2.4 mg/kg SY induced significant (P &lt; 0.05) increases in 4-aminobutyric acid, glutamic acid and umami amino acid concentrations compared to the control. In addition, the feeding of 4.8 mg/kg SY had significantly higher (P &lt; 0.05) muscle serine, valine, isoleucine, leucine, ornithine hydrochloride, methionine, and tyrosine levels than the control group. Collectively, Se supplementation in the diet did not affect growth performance, muscle chemical composition, whereas it could improve meat quality, muscle antioxidant activity, fatty acid and amino acid profiles in Qianbei-pockmarked goats. This showed that the optimal accession SY level was 4.8 mg/kg under the experimental conditions of this study.

Human Oral Sensitivity to and Taste Modulation by 3-Mercapto-2-Methylpentan-1-ol

Introduction

3-Mercapto-2-methylpentan-1-ol (3 M) is a key onion flavor (aroma), but past sensory work has focused primarily on ortho-nasal presentation. A series of experiments was conducted to characterize human sensitivity to oral 3 M solutions, then determine how 3 M impacts perception of basic tastes.

Methods

Detection thresholds were measured for a food grade, racemic mixture using a forced-choice staircase procedure (n = 19). Recognition was measured by presenting a single stimulus per trial (3 M, vanillin, or water), with "onion," "vanilla," or "water" as responses (n = 18). Supra-threshold intensity (n = 20) was measured for various concentrations using the general labeled magnitude scale (gLMS). Odor-taste interactions were studied using mixtures of 3 M and exemplars of basic tastes. Participants rated the intensity of basic tastes, or both taste and aroma, using the gLMS (n ranged from 10 to 15). All stimuli were in aqueous solution.

Results

Participants detected oral 3 M at about 0.90 ppb and recognized 3 M as "onion" at about 5 ppb. Supra-threshold intensity increased roughly as a cumulative logistic function of concentration. 3 M enhanced the rated savory intensity of monosodium glutamate, but did not enhance the dominant qualities of exemplars of the other four basic tastes. Under a response-context more favorable to an analytic approach, savory enhancement was reduced but not eliminated. Savory enhancement was eliminated with nose-clips.

Conclusions

Oral sensitivity was lower than previous retronasal studies would suggest, but roughly consistent with concentrations in cooked allium varieties. Oral 3 M selectively enhanced savory intensity, an effect likely due to retronasal aroma rather than taste or mouthfeel.

Implication

3 M is a promising candidate aroma to enhance or impart a savory flavor.

OUP accepted manuscript

The prototypical stimuli for umami taste is monosodium glutamate (MSG), which is the sodium salt form of glutamic acid. A proportion of the population has a reduced or complete inability to taste l-glutamate independent to the sodium ion. To determine individuals’ umami discrimination status, many studies use a series of triangle tests containing isomolar (29 mM) sodium chloride (NaCl) and MSG, requiring participants to correctly identify the odd sample. Across studies, inconsistent categorization criteria have been applied. The aim of this study was to determine the optimal classification criterion based on the number of tests assessed to ascertain an individual’s ability to discriminate between MSG and NaCl. Thirty-eight participants attended 3 taste assessment sessions, each involving 24 triangle tests (2 blocks of 12 tests) containing 29 mM NaCl and 29 mM MSG, detection and recognition threshold were measured for MSG, monopotassium glutamate (MPG), and sweet (sucrose) tastes. There was no learning, or fatigue trend over n = 24 (P = 0.228), and n = 12 (P = 0.940) triangle tests across each testing session. Twenty-four triangle tests produced the most consistent categorization of tasters across sessions (68.4%). The test–retest correlation across each testing session was highest for n = 24 triangle tests (ICC = 0.50), in comparison to 12 (ICC = 0.37). Overall, conducting n = 24 compared with n = 12 triangle tests provided the optimal classification to determine an individual’s ability to discriminate l-glutamate from NaCl and thus their umami discrimination status, based on the number of tests assessed in this study.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.

Evolution of glutamatergic signaling and synapses

Glutamate (Glu) is the primary excitatory transmitter in the mammalian brain. But, we know little about the evolutionary history of this adaptation, including the selection of l-glutamate as a signaling molecule in the first place. Here, we used comparative metabolomics and genomic data to reconstruct the genealogy of glutamatergic signaling. The origin of Glu-mediated communications might be traced to primordial nitrogen and carbon metabolic pathways. The versatile chemistry of L-Glu placed this molecule at the crossroad of cellular biochemistry as one of the most abundant metabolites. From there, innovations multiplied. Many stress factors or injuries could increase extracellular glutamate concentration, which led to the development of modular molecular systems for its rapid sensing in bacteria and archaea. More than 20 evolutionarily distinct families of ionotropic glutamate receptors (iGluRs) have been identified in eukaryotes. The domain compositions of iGluRs correlate with the origins of multicellularity in eukaryotes. Although L-Glu was recruited as a neuro-muscular transmitter in the early-branching metazoans, it was predominantly a non-neuronal messenger, with a possibility that glutamatergic synapses evolved more than once. Furthermore, the molecular secretory complexity of glutamatergic synapses in invertebrates (e.g., Aplysia) can exceed their vertebrate counterparts. Comparative genomics also revealed 15+ subfamilies of iGluRs across Metazoa. However, most of this ancestral diversity had been lost in the vertebrate lineage, preserving AMPA, Kainate, Delta, and NMDA receptors. The widespread expansion of glutamate synapses in the cortical areas might be associated with the enhanced metabolic demands of the complex brain and compartmentalization of Glu signaling within modular neuronal ensembles.

Possible Use of Phytochemicals for Recovery from COVID-19-Induced Anosmia and Ageusia

The year 2020 became the year of the outbreak of coronavirus, SARS-CoV-2, which escalated into a worldwide pandemic and continued into 2021. One of the unique symptoms of the SARS-CoV-2 disease, COVID-19, is the loss of chemical senses, i.e., smell and taste. Smell training is one of the methods used in facilitating recovery of the olfactory sense, and it uses essential oils of lemon, rose, clove, and eucalyptus. These essential oils were not selected based on their chemical constituents. Although scientific studies have shown that they improve recovery, there may be better combinations for facilitating recovery. Many phytochemicals have bioactive properties with anti-inflammatory and anti-viral effects. In this review, we describe the chemical compounds with anti- inflammatory and anti-viral effects, and we list the plants that contain these chemical compounds. We expand the review from terpenes to the less volatile flavonoids in order to propose a combination of essential oils and diets that can be used to develop a new taste training method, as there has been no taste training so far. Finally, we discuss the possible use of these in clinical settings.

Classical Food Quality Attributes and the Metabolic Profile of Cambuci, a Native Brazilian Atlantic Rainforest Fruit

The cambuci is a native Brazilian fruit from the Atlantic Forest biome. A soft and astringent pulp, a green color, and a sweet aroma are its main characteristics. Classical food quality attributes (fresh fruit mass, fruit height, diameters, total soluble solid, titratable acidity, and ratio) and the metabolic profile from ten accessions from three different locations were analyzed herein by analytical methods (refractometry and neutralization titration) and nuclear magnetic resonance spectroscopy. Concerning sugar content, sucrose was the predominant compound, with glucose and fructose alternating in second, depending on the accession. Citric acid was the most relevant acid, followed by shikimic and quinic acids in quite variable amounts. These three main acids vary in amounts for each accession. Ascorbic acid content emerges as an important quality attribute and makes this fruit nutritionally attractive, due to values comparable to those contained in citric fruits. The main amino acids identified in cambuci were glutamic acid individually or in comprising the tripeptide glutathione (glutamic acid, cysteine, glycine). The quality diversity of the evaluated accessions suggests the potentiality of cambuci use in future breeding programs.

Glutamate - A multifaceted molecule: Endogenous neurotransmitter, controversial food additive, design compound for anti-cancer drugs. A critical appraisal

One of the most widely used flavour enhancers in the food industry is monosodium glutamate (MSG). MSG consumption has been on an upward trend, worrying in terms of potential toxic effects. This review is focused on the long-term toxicity of MSG and the experimental evidence that supports it. The article's primary purpose was to survey recently published data regarding the consumption of MSG within safe limits. The administered doses in animal models are very varied and have given rise to controversy. Also, the paper comprises pathways to lower MSG toxicity and highlight other underexploited biological effects, as anti-cancer potential. The administration of MSG, combined with various compounds, has been shown benefit against toxic effects. Several recent studies have identified a possible mechanism that recommends MSG and some derivatives as potential anti-cancer agents. New anti-cancer compounds based on the glutamic acid structure must be studied and further exploited. International regulations require harmonization of safe doses of MSG based on current scientific studies. Replacing MSG with other umami flavour enhancers may be a safer alternative for human health in the future. The biological consequences of MSG consumption or therapeutical administration have not been fully deciphered yet.

Determination of flavor-potentiating compounds in different Italian tomato varieties

Umami taste, known as appetizing sensation, is mainly imparted by monosodium glutamate (MSG, the first identified umami factor) in synergistic combination with some 5' ribonucleotides such as inosine 5'-monophosphate, IMP, guanosine 5'-monophosphate, GMP, and adenosine 5'-monophoshate, AMP. The level of free glutamic acid in tomatoes is higher than in other vegetables or fruits and increases with ripening and industrial processing. In addition, due to the presence of bioactive metabolites, tomatoes and tomato-based products are among the most consumed healthy food items. The levels of the major umami compounds of tomato, that is, glutamate and 5'-ribonucleotides (GMP and AMP) were assessed in different parts (skin, outer flesh, and inner pulp) of known tomato varieties from southern Italy: San Marzano Originale, San Marzano 245, Black Tomato, Corbarino Corbara, Corbarino Nocera, and Superpomodoro (tomato hybrid). Such varieties were also investigated for their antioxidant properties through DMPD, DPPH, and ABTS assays, with San Marzano Originale showing the highest antioxidant power both in lipophilic and methanolic fractions. The concentration of umami compounds in tomato differs with the part of the fruit analyzed and is greatly dependent on the variety, being Corbarino Nocera the cultivar richest in glutamate and Superpomodoro in ribonucleotides. As for nutritional aspect, results confirm the great nutraceutical feature of San Marzano tomato, the most known variety used in industrial processes. PRACTICAL APPLICATIONS: This study was planned to develop a method to quantify the major umami compounds that strongly influence the organoleptic properties of many different tomato varieties. It is known that the sensory quality of fruits and vegetables is an important factor in consumer's choice. The analytical methods described here enabled the evaluation of the glutamate and 5'-ribonucleotides contents in six selected varieties of tomato from Campania region, and can be easily used to determine the sensory profile of commercial varieties, for example, those perceived as not very tasteful by consumers.

Flavor and Metabolite Profiles of Meat, Meat Substitutes, and Traditional Plant-Based High-Protein Food Products Available in Australia

Demand for plant-based proteins and plant-based food products is increasing globally. This trend is driven mainly by global population growth and a consumer shift towards more sustainable and healthier diets. Existing plant-based protein foods and meat mimetics often possess undesirable flavor and sensory properties and there is a need to better understand the formation of desirable meat-like flavors from plant precursors to improve acceptance of novel high-protein plant foods. This study aimed to comprehensively characterize the non-volatile flavor metabolites and the volatiles generated in grilled meat (beef, chicken, and pork) and compare these to commercially available meat substitutes and traditional high-protein plant-based foods (natto, tempeh, and tofu). Solid phase microextraction with gas-chromatography mass-spectrometry was used for elucidation of the flavor volatilome. Untargeted characterization of the non-volatile metabolome was conducted using Orbitrap mass spectrometry and Compound Discoverer^TM datamining software. The study revealed greater diversity and higher concentrations of flavor volatiles in plant-based foods in comparison to grilled meat, although the odor activity of specific volatiles was not considered. On average, the total amount of volatiles in plant-based products were higher than in meat. A range of concentrations of free amino acids, dipeptide, tripeptides, tetrapeptides, nucleotides, flavonoids, and other metabolites was identified in meat and plant-based foods.