Taste enhancements between various amino acids and IMP

It is well known that a strong synergistic interaction of umami occurs between L-alpha-amino acids with an acidic side chain, such as L-Glu or L-Asp, and 5'-mononucleotides, such as inosine 5'-monophosphate (IMP). We tested taste interactions between various L-alpha-amino acids and IMP by the psychophysical method and found that taste enhancement occurred when IMP was added to several sweet amino acids, such as L-Ala, L-Ser and Gly. The enhanced quality of taste was recognized as umami, and was not blocked by the sweetness inhibitor +/-2-(p-methoxyphenoxy)propanoic acid. The total taste intensities of various concentrations of the amino acid and IMP mixtures were measured using magnitude estimation. The results showed that the potentiation ratios were larger than 1 in the cases of L-Ala, L-Ser and Gly. However, the ratio was approximately 1 in the case of D-Ala, which had an enhanced taste of sweetness. Thus the umami taste enhancement of several sweet L-alpha-amino acids by IMP was synergistic rather than additive as that of acidic amino acids.     

Gustatory sensory cells express a receptor responsive to protein breakdown products (GPR92)

The ingestion of dietary protein is of vital importance for the maintenance of fundamental physiological processes. The taste modality umami, with its prototype stimulus, glutamate, is considered to signal the protein content of food. Umami was thought to be mediated by the heterodimeric amino acid receptor, T1R1 + T1R3. Based on knockout studies, additional umami receptors are likely to exist. In addition to amino acids, certain peptides can also elicit and enhance umami taste suggesting that protein breakdown products may contribute to umami taste. The recently deorphanized peptone receptor, GPR92 (also named GPR93; LPAR5), is expressed in gastric enteroendocrine cells where it responds to protein hydrolysates. Therefore, it was of immediate interest to investigate if the receptor GPR92 is expressed in gustatory sensory cells. Using immunohistochemical approaches we found that a large population of cells in murine taste buds was labeled with an GPR92 antibody. A molecular phenotyping of GPR92 cells revealed that the vast majority of GPR92-immunoreactive cells express PLCβ2 and can therefore be classified as type II cells. More detailed analyses have shown that GPR92 is expressed in the majority of T1R1-positive taste cells. These results indicate that umami cells may respond not only to amino acids but also to peptides in protein hydrolysates.     

Gustatory sensation of l- and d-amino acids in humans

Amino acids are known to elicit complex taste, but most human psychophysical studies on the taste of amino acids have focused on a single basic taste, such as umami (savory) taste, sweetness, or bitterness. In this study, we addressed the potential relationship between the structure and the taste properties of amino acids by measuring the human gustatory intensity and quality in response to aqueous solutions of proteogenic amino acids in comparison to d-enantiomers. Trained subjects tasted aqueous solution of each amino acid and evaluated the intensities of total taste and each basic taste using a category-ratio scale. Each basic taste of amino acids showed the dependency on its hydrophobicity, size, charge, functional groups on the side chain, and chirality of the alpha carbon. In addition, the overall taste of amino acid was found to be the combination of basic tastes according to the partial structure. For example, hydrophilic non-charged middle-sized amino acids elicited sweetness, and l-enantiomeric hydrophilic middle-sized structure was necessary for umami taste. For example, l-serine had mainly sweet and minor umami taste, and d-serine was sweet. We further applied Stevens’ psychophysical function to relate the total-taste intensity and the concentration, and found that the slope values depended on the major quality of taste (e.g., bitter large, sour small).     

(+)-(S)-alapyridaine--a general taste enhancer?

N-(1-Carboxyethyl)-6-hydroxymethyl-pyridinium-3-ol inner salt (alapyridaine), recently identified in heated sugar/amino acid mixtures as well as in beef bouillon, has been shown to exhibit general taste-enhancing activities, although tasteless on its own. Differing from other taste enhancers reported so far, racemic (R/S)-alapyridaine and, to an even greater extent (+)-(S)-alapyridaine, the physiologically active enantiomer, are able to enhance more than one basic taste quality. The threshold concentrations for the sweet taste of glucose and sucrose, for the umami taste of monosodium L-glutamate (MSG) and guanosine-5'-monophosphate (GMP), as well as the salty taste of NaCl, were significantly decreased when alapyridaine was present. In contrast, perception of the bitter tastes of caffeine and L-phenylalanine, as well as of sour-tasting citric acid, was unaffected. Furthermore, alapyridaine was shown to intensify known taste synergies such as, for example, the enhancing effect of L-arginine on the salty taste of NaCl, as well as that of GMP on the umami taste of MSG. The activity of (+)-(S)-alapyridaine could be observed not only in solutions of single taste compounds, but also in more complex tastant mixtures; for example, the umami, sweet and salty taste of a solution containing MSG, sucrose, NaCl and caffeine was significantly modulated, thus indicating that alapyridaine is a general taste enhancer.     

Umami taste receptor functions as an amino acid sensor via Gαs subunit in N1E-115 neuroblastoma cells

The sensing of the nutritional level of the body fluid is pivotal for maintaining homeostasis in animals. However, it is not yet understood how the cells detect nutritional levels. In the present study, we examined the function of umami taste receptor, which has a dimeric protein structure composed of Tas1r1 and Tas1r3, as amino acid sensor in the cells. We found that deprivation of amino acids induced neurite outgrowth in N1E-115 cells. The neurite outgrowth was inhibited by almost all of the amino acids tested. To investigate the involvement of the umami taste receptor, siRNA against each of Tas1r1 or Tas1r3 was administered, resulting in suppression of the inhibitory effects of amino acids on neurite outgrowth. In addition, inosine 5'-monophosphate, which potentiates the response to amino acids in the taste cells, enhanced the inhibitory effect of glutamine on neurite outgrowth. These results suggest that Tas1r1 + 3 functions as an amino acid sensor in N1E-115 cells. Because glutamine increased intracellular cAMP concentration, we investigated the involvement of the Gαs subunit of the heterotrimeric G protein in signal transduction. The treatments to inhibit the Gαs subunit significantly suppressed the increase of intracellular cAMP concentration induced by glutamine and the inhibitory effect of amino acids on neurite outgrowth. In addition, the reagents for increasing intracellular cAMP concentration inhibited neurite outgrowth induced by deprivation of amino acids. We concluded that Tas1r1 + 3 functions as an amino acid sensor and activates the intracellular signaling pathway through the Gαs subunit in N1E-115 cells.     

Identification and Quantitation of New Glutamic Acid Derivatives in Soy Sauce by UPLC/MS/MS

Glutamic acid is an abundant amino acid that lends a characteristic umami taste to foods. In fermented foods, glutamic acid can be found as a free amino acid formed by proteolysis or as a non‐proteolytic derivative formed by microorganisms. The aim of the present study was to identify different structures of glutamic acid derivatives in a typical fermented protein‐based food product, soy sauce. An acidic fraction was prepared with anion‐exchange solid‐phase extraction (SPE) and analyzed by UPLC/MS/MS and UPLC/TOF‐MS. α‐Glutamyl, γ‐glutamyl, and pyroglutamyl dipeptides, as well as lactoyl amino acids, were identified in the acidic fraction of soy sauce. They were chemically synthesized for confirmation of their occurrence and quantified in the selected reaction monitoring (SRM) mode. Pyroglutamyl dipeptides accounted for 770 mg/kg of soy sauce, followed by lactoyl amino acids (135 mg/kg) and γ‐glutamyl dipeptides (70 mg/kg). In addition, N‐succinoylglutamic acid was identified for the first time in food as a minor compound in soy sauce (5 mg/kg).     

Modulation of Sweet Taste by Umami Compounds via Sweet Taste Receptor Subunit hT1R2

Although the five basic taste qualities—sweet, sour, bitter, salty and umami—can be recognized by the respective gustatory system, interactions between these taste qualities are often experienced when food is consumed. Specifically, the umami taste has been investigated in terms of whether it enhances or reduces the other taste modalities. These studies, however, are based on individual perception and not on a molecular level. In this study we investigated umami-sweet taste interactions using umami compounds including monosodium glutamate (MSG), 5’-mononucleotides and glutamyl-dipeptides, glutamate-glutamate (Glu-Glu) and glutamate-aspartic acid (Glu-Asp), in human sweet taste receptor hT1R2/hT1R3-expressing cells. The sensitivity of sucrose to hT1R2/hT1R3 was significantly attenuated by MSG and umami active peptides but not by umami active nucleotides. Inhibition of sweet receptor activation by MSG and glutamyl peptides is obvious when sweet receptors are activated by sweeteners that target the extracellular domain (ECD) of T1R2, such as sucrose and acesulfame K, but not by cyclamate, which interact with the T1R3 transmembrane domain (TMD). Application of umami compounds with lactisole, inhibitory drugs that target T1R3, exerted a more severe inhibitory effect. The inhibition was also observed with F778A sweet receptor mutant, which have the defect in function of T1R3 TMD. These results suggest that umami peptides affect sweet taste receptors and this interaction prevents sweet receptor agonists from binding to the T1R2 ECD in an allosteric manner, not to the T1R3. This is the first report to define the interaction between umami and sweet taste receptors.     

白化和黄化茶树品种绿茶游离氨基酸、儿茶素类及咖啡碱差异分析

为探究以白化和黄化茶树品种鲜叶为原料制成的绿茶滋味品质和代谢物差异,对广德市6个白化品种绿茶(奶白茶)和14个黄化品种绿茶(黄金芽茶)进行感官审评和代谢物分析。结果表明,奶白茶滋味鲜爽而收敛性略弱;黄金芽茶滋味收敛性强而鲜度低于奶白茶。游离氨基酸总量以及呈现鲜味、甜味的游离氨基酸在奶白茶中的含量显著高于黄金芽茶,而贡献收敛性的儿茶素类化合物和没食子酸含量以及呈现苦味的咖啡碱含量在奶白茶中显著低于黄金芽茶。偏最小二乘法判别分析(PLS-DA)表明导致两种绿茶滋味差异的标志性化合物有7种,分别是茶氨酸、精氨酸、谷氨酸、天冬氨酸、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯和咖啡碱。味觉活性值(Dot)最高的EGCG在黄金芽茶中的呈味贡献显著高于奶白茶。因此,游离氨基酸、儿茶素类化合物、没食子酸和咖啡碱含量差异导致白化和黄化茶树品种绿茶滋味不同。     

Genetic and Molecular Basis of Individual Differences in Human Umami Taste Perception

Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 and TAS1R3, is proposed to function as its receptor. However, little is known about genetic variation of TAS1R1 and TAS1R3 and its potential links with individual differences in umami sensitivity. Here we investigated the association between recognition thresholds for umami substances and genetic variations in human TAS1R1 and TAS1R3, and the functions of TAS1R1/TAS1R3 variants using a heterologous expression system. Our study demonstrated that the TAS1R1-372T creates a more sensitive umami receptor than -372A, while TAS1R3-757C creates a less sensitive one than -757R for MSG and MSG plus IMP, and showed a strong correlation between the recognition thresholds and in vitro dose - response relationships. These results in human studies support the propositions that a TAS1R1/TAS1R3 heterodimer acts as an umami receptor, and that genetic variation in this heterodimer directly affects umami taste sensitivity.     

L-Amino Acids Elicit Diverse Response Patterns in Taste Sensory Cells: A Role for Multiple Receptors

Umami, the fifth basic taste, is elicited by the L-amino acid, glutamate. A unique characteristic of umami taste is the response potentiation by 5’ ribonucleotide monophosphates, which are also capable of eliciting an umami taste. Initial reports using human embryonic kidney (HEK) cells suggested that there is one broadly tuned receptor heterodimer, T1r1+T1r3, which detects L-glutamate and all other L-amino acids. However, there is growing evidence that multiple receptors detect glutamate in the oral cavity. While much is understood about glutamate transduction, the mechanisms for detecting the tastes of other L-amino acids are less well understood. We used calcium imaging of isolated taste sensory cells and taste cell clusters from the circumvallate and foliate papillae of C57BL/6J and T1r3 knockout mice to determine if other receptors might also be involved in detection of L-amino acids. Ratiometric imaging with Fura-2 was used to study calcium responses to monopotassium L-glutamate, L-serine, L-arginine, and L-glutamine, with and without inosine 5’ monophosphate (IMP). The results of these experiments showed that the response patterns elicited by L-amino acids varied significantly across taste sensory cells. L-amino acids other than glutamate also elicited synergistic responses in a subset of taste sensory cells. Along with its role in synergism, IMP alone elicited a response in a large number of taste sensory cells. Our data indicate that synergistic and non-synergistic responses to L-amino acids and IMP are mediated by multiple receptors or possibly a receptor complex.     

基于游离氨基酸的组分及特征比较四种食用菌与四种果蔬的营养与风味特征

为科学评价食用菌与果蔬两类食材的营养特征与口感风味,本研究选取4种常见食用菌（金针菇、斑玉蕈、香菇、双孢蘑菇）和4种常见果蔬（苹果、香蕉、胡萝卜、番茄）,采用氨基酸自动分析仪测定其游离氨基酸,系统比较了两类食材的游离氨基酸组分比例及呈味特征。主成分和聚类分析表明 4种食用菌和4种果蔬显著分为两类,食用菌类游离氨基酸总量平均是果蔬类的3倍以上,4种食用菌中各游离氨基酸的比例均衡。4种食用菌的必需氨基酸/(必需氨基酸+非必需氨基酸)在40%左右,必需氨基酸/非必需氨基酸接近或大于60%,均接近理想值。4种食用菌所含的呈味氨基酸（鲜味、甜味、芳香族、苦味）均是4种果蔬的2倍以上,TAV值最显著的是：谷氨酸、苯丙氨酸、甘氨酸、苏氨酸、组氨酸、赖氨酸、缬氨酸、精氨酸和丙氨酸。这些氨基酸分属在五大氨基酸家族,在食用菌与果蔬中代谢途径相同;只有赖氨酸在二者中的合成途径不同。结果表明供试的食用菌比果蔬有优质的氨基酸比例和丰富的呈味组分,此差异体现在众多氨基酸的代谢层面,而非个别氨基酸导致。     

Isolation and identification of the umami enhancing compounds in Japanese soy sauce

To clarify the key compounds that account for the umami taste of soy sauce, a typical Japanese soy sauce, Koikuchi Shoyu, was separated by preparative chromatography, and the umami enhancing fractions were screened on the basis of an umami intensity of a 6.0 mM monosodium L-glutamate (MSG) solution. Liquid chromatography-time of flight mass spectrometry (LC-TOFMS), 1D/2D nuclear magnetic resonance spectroscopy (NMR) studies of the umami enhancing fractions led to the identification of N-(1-deoxy-D-fructos-1-yl)pyroglutamic acid (Fru-pGlu), N-(1-deoxy-D-fructos-1-yl)valine (Fru-Val), N-(1-deoxy-D-fructos-1-yl)methionine (Fru-Met), pyroglutamylglutamine (pGlu-Gln), and pyroglutamylglycine (pGlu-Gly). Although all the compounds identified were at sub-threshold concentrations in the soy sauce, a taste reconstitution experiment revealed that they contributed part of the umami taste of the soy sauce.     

Genetic variation of umami taste genes in Koreans

Umami is a pleasant savoury taste imparted by glutamate, a type of amino acid, and ribonucleotides, including inosinate and guanylate, which occur naturally in many foods including meat, fish, vegetables and dairy products. A heterodimer of TAS1R1 and TAS1R3 is known to function as umami taste receptor in humans. To address the association between genetic polymorphism of TAS1R1 / TAS1R3 genes and individual difference in umami taste sensitivity, we have examined the entire coding region of these genes using PCR-mediated direct sequencing analysis. A total of 11 SNPs were identified from 98 unrelated Korean individuals and were in Hardy-Weinberg Equilibrium. Four out of 11 SNPs were found in the exons and two of them were nonsynonymous ones. These coding SNPs (cSNPs), p.A372T in TAS1R1 and p.C757R in TAS1R3 genes, were common in Koreans, so these will be useful resource for further studies to find a functional allele for individual variation to umami taste sensitivity in our population.     

不同培养基质对草菇营养成分及呈味物质的影响

在栽培条件一致的情况下,以5种不同培养基质栽培的草菇子实体为研究对象,测定粗蛋白、水解氨基酸、游离氨基酸、可溶性糖醇、有机酸及5′-核苷酸组成与含量,研究不同培养基质对草菇子实体营养成分及呈味物质的影响。结果表明以棉籽壳为基质栽培草菇,其粗蛋白及水解氨基酸含量及组成最优;以稻草为基质栽培草菇,其可溶性糖醇、有机酸含量最高。综合各种呈鲜成分,等鲜浓度值（equivalent umami concentration,EUC）范围为317.45-708.75g MSG/100g,其中以棉籽壳为基质栽培的草菇子实体EUC值最高,以刺芹侧耳菌渣为基质栽培的草菇EUC次之,以金针菇菌渣为基质栽培的草菇EUC [(317.45±13.67)g MSG/100g]最低,约为棉籽壳样品EUC值的44.79%。因此,培养基质对草菇呈味物质的影响显著,可根据需要的呈味物质选用不同的培养基质栽培草菇。     

Glutamate: a truly functional amino acid

Glutamate is one of the most abundant of the amino acids. In addition to its role in protein structure, it plays critical roles in nutrition, metabolism and signaling. Post-translational carboxylation of glutamyl residues increases their affinity for calcium and plays a major role in hemostasis. Glutamate is of fundamental importance to amino acid metabolism, yet the great bulk of dietary glutamate is catabolyzed within the intestine. It is necessary for the synthesis of key molecules, such as glutathione and the polyglutamated folate cofactors. It plays a major role in signaling. Within the central nervous system, glutamate is the major excitatory neurotransmitter and its product, GABA, the major inhibitory neurotransmitter. Glutamate interaction with specific taste cells in the tongue is a major component of umami taste. The finding of glutamate receptors throughout the gastrointestinal tract has opened up a new vista in glutamate function. Glutamate is truly a functional amino acid.     

Gustatory responses to amino acids in the chorda tympani nerve of C3H mice

Integrated neural responses to various amino acids were recorded from the chorda tympani (facial) nerve in C3H mice. The basic amino acids hydrochlorides L-Arg-HCl and L-Lys-HCl evoked large magnitude integrated taste responses, similar to that for NaCl, and had estimated electrophysiological thresholds of 0.0001 M. No significant difference was indicated between the response magnitudes for the L- and D-forms of the basic amino acid hydrochlorides; however, responses to the basic amino acid hydrochlorides cross-adapted with NaCl. Responses to neutral L-amino acids (Ser, Ala, Gly), which taste sweet to humans, showed higher thresholds (>0.0003 M), similar to that for sucrose, and did not cross-adapt with basic amino acid hydrochlorides or with NaCl. Responses to the neutral amino acids L-Ser and L-Ala were larger than those to their D-amino acid enantiomers. The acidic amino acids L-Asp and L-Glu showed concentration-response functions different from that for HCl. Both acidic amino acids were more stimulatory than HCl at the same pH, although the responses to them were cross-adapted by HCl, indicating a pH effect. A comparison of the stimulatory effectiveness among amino acid derivatives and analogues suggested that the alpha- amino group is essential for the stimulatory effectiveness of neutral amino acids.      

Taste preference synergy between glutamate receptor agonists and inosine monophosphate in rats

Monosodium glutamate (MSG) elicits a taste called umami and interacts synergistically with nucleotide monophosphates such as 5'-inosine monophosphate (IMP) to potentiate this taste intensity. Indeed, the synergistic interaction of nucleotide monophosphates and MSG is a hallmark of umami. We examined interactions between MSG and other taste stimuli, including IMP, by measuring the lick rates of non-deprived rats during 30 s trials. To control for non-linear psychophysical functions, the concentration of one taste stimulus in a binary mixture was systematically increased while the concentration of the second taste stimulus was decreased (stimulus substitution method). Synergy between two stimuli was detected if the lick rate for a binary mixture exceeded that expected from the sum of the lick rates for each stimulus alone. In initial experiments, taste synergy was observed when rats were presented with mixtures of MSG and IMP but not with mixtures of MSG and sucrose. In subsequent experiments, glutamate receptor agonists other than MSG were presented with IMP to test for taste synergy. No evidence of synergy was seen when rats were presented with mixtures of IMP and kainic acid or IMP and N:-methyl-D-aspartate. However, taste synergy between IMP and L-AP4, a potent agonist at mGluR4 receptors, was observed. These results suggest that a metabotropic glutamate receptor similar to mGluR4 may be involved in the taste synergy that characterizes umami.     

Elucidation of the role of peptide linker in calcium-sensing receptor activation process

Family 3 G-protein-coupled receptors (GPCRs), which includes metabotropic glutamate receptors (mGluRs), sweet and "umami" taste receptors (T1Rs), and the extracellular calcium-sensing receptor (CaR), represent a distinct group among the superfamily of GPCRs characterized by large amino-terminal extracellular ligand-binding domains (ECD) with homology to bacterial periplasmic amino acid-binding proteins that are responsible for signal detection and receptor activation through as yet unresolved mechanism(s) via the seven-transmembrane helical domain (7TMD) common to all GPCRs. To address the mechanism(s) by which ligand-induced conformational changes are conveyed from the ECD to the 7TMD for G-protein activation, we altered the length and composition of a 14-amino acid linker segment common to all family 3 GPCRs except GABA(B) receptor, in the CaR by insertion, deletion, and site-directed mutagenesis of specific highly conserved residues. Small alterations in the length and composition of the linker impaired cell surface expression and abrogated signaling of the chimeric receptors. The exchange of nine amino acids within the linker of CaR with the homologous sequence of mGluR1, however, preserved receptor function. Ala substitution for the four highly conserved residues within this amino acid sequence identified a Leu at position 606 of the CaR critical for cell surface expression and signaling. Substitution of Leu(606) for Ala resulted in impaired cell surface expression. However, Ile and Val substitutions displayed strong activating phenotypes. Disruption of the linker by insertion of nine amino acids of a random-coiled structure uncoupled the ECD from regulating the 7TMD. These data are consistent with a model of receptor activation in which the peptide linker, and particularly Leu(606), provides a critical interaction for the CaR signal transmission, a finding likely to be relevant for all family 3 GPCRs containing this conserved motif.     

短时微流水处理对池塘养殖鳙鱼肌肉滋味品质的影响

为探究短时微流水处理对池塘养殖鳙鱼(Aristichthys nobilis)肌肉滋味品质的影响, 采用微流水装置对池塘养殖鳙鱼进行处理, 研究处理时间(0、2d、4d、6d、8d和10d)对池塘养殖鳙鱼肌肉中基本营养成分、游离氨基酸、脂肪酸、核苷酸及其降解产物、甜菜碱含量和感官评分的影响, 以期为提升鳙鱼滋味品质提供新方法。结果表明: 随着微流水处理时间的延长, 鳙鱼肌肉中总游离氨基酸含量、甜味氨基酸含量、腺苷酸(Adenosine monophosphate, AMP)含量和甜菜碱含量呈现先增加后降低的趋势, 均在处理6d时含量最高, 较未处理组分别增加了17.74%、39.45%、28.00%和50.16%; 灰分和鲜味氨基酸含量呈现增加的趋势; 粗脂肪、总脂肪酸含量、饱和脂肪酸含量、单不饱和脂肪酸含量、多不饱和脂肪酸含量、苦味氨基酸含量、酸味氨基酸含量、次黄嘌呤核苷(Hypoxanthine riboside, HxR)和次黄嘌呤(Hypoxanthine, Hx)含量则逐渐降低; 粗蛋白含量在处理过程中无显著变化。滋味分析仪(电子舌)和感官评分结果表明, 微流水处理显著提高了鳙鱼肌肉鲜味和甜味, 降低了其咸味、苦味和腥味, 且处理6d时鳙鱼肌肉的滋味、气味、质地和色泽感官评分最高。故短时微流水处理可显著提高鳙鱼的肌肉滋味品质, 不降低营养品质, 适宜的处理时间为6d。     

TASTE PERCEPTION OF UMAMI-RICH DISHES IN ITALIAN CULINARY TRADITION

The aim of this research project was to investigate umami taste properties of recipes based on Italian culinary tradition and prepared with umami-rich ingredients, focusing on the impact of the preparation and ingredient combination. Gustative profiles were prepared for a traditional Italian dish, tender beef bouillon, usually consumed with pasta stuffed with beef. Four different samples were designed by changing the ingredients (with or without integrating Parmigiano cheese) and the preparation (cooking time) of the recipe. Panelists were rigorously trained for umami taste evaluation using monosodium L-glutamate (MSG) aqueous solutions and were then asked to evaluate umami sensation in tender beef bouillon with or without added Parmigiano Reggiano . A majority of the panelists were able to distinguish correctly umami sensations induced by MSG. The level of umami enhancement induced by Parmigiano Reggiano was clearly perceived by the panelists, and this enhancement positively affected also other basic tastes; whereas the cooking time had no clear effect on the gustative perception.

PRACTICAL APPLICATIONS

In western countries, people do not know much about umami. This taste is defined as the "savoriness" of the glutamate. Umami-taste substances are present in several foods, but whereas the taste of monosodium glutamate and 5' nucleotides can be without difficulty identified in water solutions, which are usually employed for panel training, the ability to identify this primary taste decreases enormously in more complex matrices like food. This study describes a procedure for screening and training sensory panels and could serve as a guide in teaching panelists to recognize and quantify the umami taste in a multistimuli matrix like a food recipe or product.
It also provides a practical application in a recipe in which the umami taste is modulated by the culinary preparation and ingredients.