Umami Substances Research Articles

A review of the alleged health hazards of monosodium glutamate.

Monosodium glutamate (MSG) is an umami substance widely used as flavor enhancer. Although it is generally recognized as being safe by food safety regulatory agencies, several studies have questioned its long-term safety. The purpose of this review was to survey the available literature on preclinical studies and clinical trials regarding the alleged adverse effects of MSG. Here, we aim to provide a comprehensive overview of the reported possible risks that may potentially arise following chronic exposure. Furthermore, we intend to critically evaluate the relevance of this data for dietary human intake. Preclinical studies have associated MSG administration with cardiotoxicity, hepatotoxicity, neurotoxicity, low-grade inflammation, metabolic disarray and premalignant alterations, along with behavioral changes. Moreover, links between MSG consumption and tumorigenesis, increased oxidative stress and apoptosis in thymocytes, as well as genotoxic effects in lymphocytes have been reported. However, in reviewing the available literature, we detected several methodological flaws, which led us to conclude that these studies have limited relevance for extrapolation to dietary human intakes of MSG risk exposure. Clinical trials have focused mainly on the effects of MSG on food intake and energy expenditure. Besides its well-known impact on food palatability, MSG enhances salivary secretion and interferes with carbohydrate metabolism, while the impact on satiety and post-meal recovery of hunger varied in relation to meal composition. Reports on MSG hypersensitivity, also known as 'Chinese restaurant syndrome', or links of its use to increased pain sensitivity and atopic dermatitis were found to have little supporting evidence. Based on the available literature, we conclude that further clinical and epidemiological studies are needed, with an appropriate design, accounting for both added and naturally occurring dietary MSG. Critical analysis of existing literature, establishes that many of the reported negative health effects of MSG have little relevance for chronic human exposure and are poorly informative as they are based on excessive dosing that does not meet with levels normally consumed in food products.

4.うま味は生体恒常性維持の担い手 : 味覚・内臓感覚・食欲・体重調節( おいしさのシグナルと肥満(ダイエット)の科学)

4.うま味は生体恒常性維持の担い手 : 味覚・内臓感覚・食欲・体重調節( おいしさのシグナルと肥満(ダイエット)の科学)

Monosodium glutamate ingestion during the development period reduces aggression mediated by the vagus nerve in a rat model of attention deficit-hyperactivity disorder

We used an umami substance, monosodium glutamate (MSG), as a simple stimulant to clarify the mechanism of the formation of emotional behavior. A 60 mM MSG solution was fed to spontaneously hypertensive rats (SHR), used as a model of attention-deficit hyperactivity disorder, from postnatal day 25 for 5 weeks kept in isolation. Emotional behaviors (anxiety and aggression) were then assessed by the open-field test, cylinder test and social interaction test. MSG ingestion during the developmental period resulted in a significant reduction in aggressive behavior but had few effects on anxiety-like behavior. Several experiments were performed to identify the reason for the reduced aggression with MSG intake. Blood pressure in the MSG-treated SHR was comparable to that of the controls during development. Argyrophil III staining to detect the very early phase of neuronal damage revealed no evidence of injury by MSG in aggression-related brain areas. Assessment of plasma amino acids revealed that glutamate levels remained constant (∼80 μM) with MSG ingestion, except for a transient increase after fasting (∼700 μM). However, lactate dehydrogenase assay in an in vitro blood-brain barrier model showed that cell toxicity was not induced by indirect MSG application even at 700 μM, confirming that MSG ingestion caused minimal neuronal damage. Finally, vagotomy at the sub-diaphragmatic level before MSG ingestion blocked its effect on aggressive behavior in the isolated SHR. The data suggest that MSG ingestion during the developmental period can reduce aggressive behavior in an attention deficit-hyperactivity disorder model rat, mediated by gut-brain interaction.

Calcium Homeostasis Modulator 1-Like Currents in Rat Fungiform Taste Cells Expressing Amiloride-Sensitive Sodium Currents.

Salt reception by taste cells is still the less understood transduction process occurring in taste buds, the peripheral sensory organs for the detection of food chemicals. Although there is evidence suggesting that the epithelial sodium channel (ENaC) works as sodium receptor, yet it is not clear how salt-detecting cells signal the relevant information to nerve endings. Taste cells responding to sweet, bitter, and umami substances release ATP as neurotransmitter through a nonvesicular mechanism. Three different channel proteins have been proposed as conduit for ATP secretion: pannexin channels, connexin hemichannels, and calcium homeostasis modulator 1 (CALHM1) channels. In heterologous expression systems, these channels mediate outwardly rectifying membrane currents with distinct biophysical and pharmacological properties. I therefore tested whether also salt-detecting taste cells were endowed with these currents. To this aim, I applied the patch-clamp techniques to single cells in isolated taste buds from rat fungiform papillae. Salt-detecting cells were functionally identified by exploiting the effect of amiloride, which induces a current response by shutting down ENaCs. I looked for the presence of outwardly rectifying currents by using appropriate voltage-clamp protocols and specific pharmacological tools. I found that indeed salt-detecting cells possessed these currents with properties consistent with the presence, at least in part, of CALHM1 channels. Unexpectedly, CALHM1-like currents in taste cells were potentiated by known blockers of pannexin, suggesting a possible inhibitory action of this protein on CALMH1. These findings indicate that communication between salt-detecting cells and nerve endings might involve ATP release by CALMH1 channels.

Effect of deamidation-induced modification on umami and bitter taste of wheat gluten hydrolysates.

Bitter taste is the main limiting factor for various applications of protein hydrolysates. Frequently used physicochemical methods for debittering protein hydrolysates come with some undesired side effects. Deamidation-induced modification would be a very promising technique to improve the flavor of wheat gluten hydrolysates (WGHs). This study was designed to determine the effect of deamidation with certain enzymes or acid treatment on the chemical composition, bitterness and umami properties of WGHs. The difference between umami peptide and free glutamic acid on the suppression of bitterness is emphatically discussed. The optimal scheme is proposed based on the flavor of WGHs and the yield of peptides. The generation of umami substances suppressed bitter signal transduction. When the content of umami substances was relatively high, the umami-enhancing properties of umami peptides were obviously effective. The intensity of umami taste was high enough to further suppress bitter taste in the course of neurocognitive functioning. When WGHs were treated with Glutaminase for 180 min, the umami taste score increased from 1.62 to 4.27 and the bitter taste score decreased from 1.33 to 0.65. © 2016 Society of Chemical Industry.

Novel Umami Ingredients: Umami Peptides and Their Taste.

Umami substances are very important for food seasoning and healthy eating. In addition to monosodium glutamate and some nucleotides, recent investigations have revealed that several peptides also exhibit umami taste. In recent years, 52 peptides have been reported to show umami taste, including 24 dipeptides, 16 tripeptides, 5 octapeptides, 2 pentapeptides, 2 hexapeptides, 1 tetrapeptide, 1 heptapeptide, and 1 undecapeptide. Twenty of these peptides have been examined for the present of umami taste. In this review, we have listed these umami peptides based on their category, source, taste, and threshold concentration. The evidence for peptides showing umami taste, the umami taste receptors on the human tongue, and the peptides whose umami taste is controversial are also discussed.

Browning Intensity and Taste Change Analysis of Chicken Protein-Sugar Maillard Reaction System with Antioxidants and Different Drying Processes

Inhibitory effects of several antioxidants on the browning intensity of chicken protein–sugar Maillard reaction system were investigated. The results found that 1% (m/v) addition of NaCl had a certain effect on inhibiting browning, while only 0.5% (m/v) addition of L-cysteine can play a favorable role in browning inhibition. As for MRP samples with L-ascorbic acid, the browning inhibiting effect reaches the max with the L-ascorbic acid content of 0.3% (m/v). The A420 value of samples dried by spray drying process was higher (P < 0.05) than those of chicken protein Maillard peptide and enzymatic hydrolysate dealt by freeze drying process. The electronic tongue analysis indicated that the umami substances of chicken protein Maillard peptide could be easily decompose in the process of storage, while those of enzymatic hydrolysate were stable. However, compared with the spray drying process, freeze drying process can better preserve umami substances. Practical Applications The inhibitory effect of several antioxidants, including NaCl, L-cysteine, polyphenols and L-ascorbic acid, on the browning intensity of chicken protein–sugar Maillard reaction system was identified. In the meantime, the effects of two kinds of drying technologies (spray drying technology and freeze drying technology) on the properties and browning intensity of Maillard peptides were also compared and discussed. Results obtained in this work can provide practical application in food industry.

Flavor Preferences Conditioned by Dietary Glutamate

AbstractOur understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study.

The umami taste: from discovery to clinical use.

In the diversity of the flavor world only five basic tastes have been described. The newest one, umami, has been identified about one hundred years ago by Kikunae Ikeda but widely accepted just in the second half of the twentieth century by international scientific world. There are three umami substances: monosodium glutamate (MSG), inosine-5'-monophosphate (IMP), guanylo-5'-monophosphate (GMP). A real breakthrough in umami history concerned the finding about independent receptors for umami: T1R1 and T1R3 (taste receptors type 1 member 1 and member 3). The palatable, delicious taste of umami and its mechanism determined a lot of research studies on this highlight. Umami substances elicit salivary secretion, enhance appetite and increase food palatability. They are desirable to improve the quality of diet. Moreover, the association between umami substances and the suppression of obesity has been found. Studies suggest that umami is engaged in metabolism but also increases satiety and reduces the post-ingestive recovery of hunger.

Discrimination of edible fungi varieties and evaluation of their umami intensities by using an electronic tongue method

SummaryThe flavour and taste of edible fungi are highly associated with the presence of several umami substances. In this study, the different edible fungi are discriminated by an electronic tongue method. The response data are analysed by the PCA (principal component analysis), DFA (discriminant factor analysis) and PLS (partial least square) method. The results show that the two data analysis methods (PCA and DFA) could successfully distinguish the variety of edible fungi. Moreover, the umami intensities of the edible fungi solutions are evaluated and compared by an electronic tongue analysis with calibration by the responses of different monosodium glutamate (MSG) concentrations. The signals are also used to build up PLS models to estimate and predict the umami intensities of the edible fungi. The results of this study indicate that the electronic tongue has a great potential in qualitative and quantitative analysis of the sensory quality of edible fungi.

Reduction of sodium content in spicy soups using monosodium glutamate

BackgroundExcessive dietary sodium intake causes several diseases, such as hypertension, cardiovascular and renal disease, etc. Hence, reducing sodium intake has been highly recommended. In this study the effect of monosodium glutamate (MSG), as an umami substance, on saltiness and sodium reduction was investigated.Methods and ResultsThe trained panellists were presented with basic spicy soups (curry chicken and chili chicken) containing different amounts of sodium chloride (NaCl) (0–1.2%) and MSG (0–1.2%). They tasted the optimum concentrations of NaCl and MSG for the two spicy soups and the overall acceptability were 0.8% and 0.7%, respectively. There was no significant effect of spiciness level on the saltiness and umami taste of both soups. The optimum levels of combined NaCl and MSG for overall acceptance in the chili and curry soups were 0.3% and 0.7%, respectively. The results showed that with the addition of MSG, it is possible to reduce sodium intake without changing the overall acceptability of the spicy soup. A 32.5% reduction in sodium level is made feasible by adding 0.7% MSG to the spicy soups.ConclusionsThis study suggests that low-sodium soups can be developed by the addition of appropriate amounts of MSG, while maintaining the acceptability of the spicy soups. It was also proven that it is feasible to reduce sodium intake by replacing NaCl with MSG.

Discrimination of Umami Tastants Using Floating Electrode-Based Bioelectronic Tongue Mimicking Insect Taste Systems.

We report a floating electrode-based bioelectronic tongue mimicking insect taste systems for the detection and discrimination of umami substances. Here, carbon nanotube field-effect transistors with floating electrodes were hybridized with nanovesicles containing honeybee umami taste receptor, gustatory receptor 10 of Apis mellifera (AmGr10). This strategy enables us to discriminate between l-monosodium glutamate (MSG), best-known umami tastant, and non-umami substances with a high sensitivity and selectivity. It could also be utilized for the detection of MSG in liquid food such as chicken stock. Moreover, we demonstrated the synergism between MSG and disodium 5'-inosinate (IMP) for the umami taste using this platform. This floating electrode-based bioelectronic tongue mimicking insect taste systems can be a powerful platform for various applications such as food screening, and it also can provide valuable insights on insect taste systems.

The effects of intragastric infusion of umami solutions on amygdalar and lateral hypothalamic neurons in rats.

Previous behavioral studies have suggested that l-glutamate, an umami substance, is detected in the gut, and that this information regarding glutamate is conveyed from the gut to the amygdala and the lateral hypothalamus (LH) through the vagus nerve to establish glutamate preference. In this study, we investigated the roles of the amygdala and LH in the information processing of gut glutamate. We recorded the activity of amygdalar and LH neurons during the intragastric administration of five test solutions (monosodium l-glutamate [MSG, 60 mmol/L]; inosine monophosphate [IMP, 60 mmol/L]; a mixture of MSG and IMP; NaCl [60 mmol/L]; or physiological saline) in intact and subdiaphragmatic vagotomized awake rats. In intact rats, 349 and 189 neurons were recorded from the amygdala and LH, respectively, while in vagotomized rats, 104 and 90 neurons were recorded from the amygdala and LH, respectively. In intact rats, similar percentages of neurons (30–60%) in the amygdala and LH responded to the intragastric infusion of the solutions. Vagotomy significantly altered responses to the MSG and NaCl solutions. In particular, vagotomy suppressed the inhibitory responses to the NaCl solution. Furthermore, vagotomy increased the response similarity between the MSG and NaCl solutions, suggesting that vagotomy impaired the coding of the postingestive consequences of the MSG solution in the amygdala and LH, which are unique for glutamate. The present results provide the first neurophysiological evidence that amygdalar and LH neurons process glutamate signals from the gut.

Does this taste fatty to you?

Taste![Figure][1] Fat, like sweetness, sourness, bitterness, and saltiness, may be a distinct taste PHOTO: DRAGONIMAGES/THINKSTOCK Just as food can be too salty or too sweet, we also complain if food is too oily or fatty. But is that judgement based on the distinct taste of fat, or is it just a mix of other basic tastes and textures? Running et al. now report that our primary taste senses have a previously unknown sibling, dubbed “oleogustus.” They asked 48 volunteers to sort 15 taste samples by quality, and most of them could distinguish long-chained nonesterified fatty acids (NEFAs) such as oleic acid from sweet, sour, salty, bitter, and umami substances, whereas short-chained NEFAs such as citric acid tasted sour. The results may be important to the food industry, such as when selecting fat replacers. Chem. Senses 10.1093/chemse/bjv036 (2015). [1]: pending:yes

Optimization of a sensory evaluation protocol for measuring the umami taste

Umami substances linger in mouth for a long time, making it difficult to achieve an accurate sensory measurement. The objective was to establish a reproducible protocol to accurately measure the intensity of umami taste. Two-alternative-forced choice (2-AFC), ranking, and rating methods were compared for discrimination ability of umami taste intensities of monosodium glutamate solutions. Monadic rating and rank-rating methods were compared for accuracy in measurement of umami intensities since neither 2-AFC nor ranking method generates numerical intensity values. Mouth rinsing protocol efficiencies were investigated for 7 palate cleansing methods during umami intensity evaluation. 2-AFC was the most powerful method, followed by ranking and rating methods, for discrimination of different umami samples. Monadic rating and rank-rating methods both showed similar error rates but monadic rating was slightly more accurate than rank-rating. Crackers, a toothbrush, and water at 45oC were more effective palate cleansers than carrots and water at 18oC.

Expression of umami-taste-related genes in the tongue: a pilot study for genetic taste diagnosis.

Expression of taste-related genes in the tongue was analysed to develop a technique for genetic diagnosis of umami taste disorders. Tissue samples were collected from healthy volunteers by scraping the foliate papillae of the tongue. Immunocytochemistry staining of gustducin, a taste-cell-specific G protein, and gene expression analysis by real-time polymerase chain reaction of β-actin, gustducin (GNAT3) and umami receptors (T1R1, T1R3 and mGluR1) were performed. Changes in umami receptor expression following application of umami substances onto the tongue were analysed. Gustducin-positive cells were observed in the samples, indicating the presence of taste cells. Gene expression of β-actin, GNAT3, T1R1 and T1R3 was detected in all seven samples tested, while that of mGluR1 was detected in four samples. Sequence analysis by NCBI Blast showed that each polymerase chain reaction product had a 99% rate of identification of its target sequence. Stimulation of the tongue with monosodium glutamate significantly upregulated the gene expression levels of T1R1 and T1R3, indicating that this method can detect alterations in umami-related gene expression. Evaluation of the expression of the umami receptor genes, T1R1 and T1R3, in the tongue may be clinically useful for objective genetic diagnosis of umami taste disorders.

천연 염미증강제 개발을 위한 완도산 다시마의 열수 추출 조건 최적화 및 염미증강 효능 평가

완도산 다시마를 천연 염미증강제로 개발하기 위하여 다시마로부터 정미성분이 최적으로 추출되는 열수 추출 조건을 평가하였으며, 다시마 추출분말을 이용하여 염미증강 효능과 나트륨 저감화율을 분석하였다. 정미성분 추출에 가장 적합한 완도산 다시마의 수확시기를 선정하기 위하여 5월, 6월, 7월에 수확한 다시마의 일반성분과 유리아미노산을 분석한 결과 정미성분 아미노산(glutamic acid와 aspartic acid)의 함량이 가장 높은 6월 수확 다시마를 추출 원료로 선정하였다. 다시마 열수 추출 온도와 시간 조건을 평가하기 위하여 60°C, 80°C, 100°C에서 1시간, 2시간, 3시간을 각각 추출하여 추출액의 품질 특성을 분석한 결과 100°C 추출 조건에서 가용성 고형분과 조단백의 함량이 35.47~36.93%와 3.75~4.00%로 가장 높게 나타났으며, 점도는 1.96~2.19 cP로 낮게 나타나 추출 온도는 100°C를 선정하였다. 추출 시간 선정을 위하여 100°C에서 추출 시간에 따른 추출액의 정미성분 아미노산 함량과 관능적 특성을 평가한 결과 추출 2시간에서 정미성분 아미노산인 glutamic acid와 aspartic acid의 함량이 각각 275.33 mg%와 121.18 mg%로 가장 높게 나타났으며, 관능적 기호도도 유의적으로 높게 평가되어 다시마로부터 정미성분 추출을 위해 적합한 추출온도와 시간은 100°C, 2시간 조건으로 확인되었다. 정미성분이 최적으로 추출된 다시마의 추출분말을 제조하여 NaCl 용액에 첨가한 후 염미증강 효능을 평가한 결과 짠맛 강도 1, 5, 9의 NaCl 용액이 다시마 추출분말 1% 첨가 후 짠맛 강도 4.25, 10.08, 16.58로 상승하였다. 동일한 짠맛 강도에서 NaCl 용액과 다시마 추출분말이 첨가된 시험용액의 나트륨 함량을 측정하여 나트륨 저감화율을 분석한 결과 12.24~24.33%의 저감화율을 나타내었다. 본 연구를 통하여 감칠맛과 정미성분이 풍부한 다시마 추출물은 조미소재뿐만 아니라 식품에서 나트륨 함량을 줄이기 위한 천연 염미증강제로서 산업적 활용을 기대할 수 있다.

Temporal design of taste and flavor: practical collaboration between chef and scientist

Recently, many chefs have collaborated with researchers and used scientific techniques in their cooking. These researchers advise chefs from a scientific perspective. However, they do not know what chefs think and what concept they want to express through their dishes. Once scientists understand what motivates chefs in the creation of their new dishes, they would be able to provide chefs with more precise advice. The authors identified culinary success factors (CSFs) from context analysis of a culinary magazine for chefs and visualized the relationships between the CSFs when renowned chefs trained in Japanese and French cuisine create new dishes. The results revealed differences not only in cooking techniques, ingredients, and condiments but also in cognitive structure (pattern of thinking) when creating new dishes. One of the authors (KS) has two Michelin stars for his French restaurant. He believes that umami affects the flavor of the main ingredients, which allows him to feature the intrinsic characteristics of the main ingredients. The chef’s cognitive structure is apparent in his cuisine. Based on the results, the chef is advised to understand the nature of umami substances, how to recognize their tastes or flavors, and create a dish that brings flavor changes temporally. In a demonstration, a new dish is unveiled using an umami ingredient according to such a concept, which fits chef’s cognitive structure.

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

Three umami substances (glutamate, 5′-inosinate, and 5′-guanylate) were found by Japanese scientists, but umami has not been recognized in Europe and America for a long time. In the late 1900s, umami was internationally recognized as the fifth basic taste based on psychophysical, electrophysiological, and biochemical studies. Three umami receptors (T1R1 + T1R3, mGluR4, and mGluR1) were identified. There is a synergism between glutamate and the 5′-nucleotides. Among the above receptors, only T1R1 + T1R3 receptor exhibits the synergism. In rats, the response to a mixture of glutamate and 5′-inosinate is about 1.7 times larger than that to glutamate alone. In human, the response to the mixture is about 8 times larger than that to glutamate alone. Since glutamate and 5′-inosinate are contained in various foods, we taste umami induced by the synergism in daily eating. Hence umami taste induced by the synergism is a main umami taste in human.

Umami–bitter interactions: The suppression of bitterness by umami peptides via human bitter taste receptor

Taste–taste interactions often showed in human psychophysical studies. Considering that each tastant in foodstuffs individually stimulates its responsible gustatory systems to elicit relevant taste modalities, taste–taste interaction should be performed in taste receptor cell-based assay. While umami substances have been proposed to suppress the bitterness of various chemicals in human sensory evaluation, the bitter–umami interaction has not been explored in bitter taste receptors, TAS2Rs. We investigated umami–bitter taste interactions by presenting umami peptides with bitter substance (salicin) on Ca2+-flux signaling assay using hTAS2R16-expressing cells. Five representative umami peptides (Glu-Asp, Glu-Glu, Glu-Ser, Asp-Glu-Ser, and Glu-Gly-Ser) derived from soybean markedly attenuated the salicin-induced intracellular calcium influx in a time-dependent manner, respectively, while Gly-Gly, a tasteless peptide did not. The efficacies of Glu-Glu suppressing salicin-induced activation of hTAS2R16 were higher than that of probenecid, a specific antagonist of hTAS2R16. According to Ca2+-flux signaling assay using the mixtures of salicin and umami peptides, all five umami peptides suppressed salicin-induced intracellular calcium influx in a noncompetitive manner. These results may provide evidence that umami peptides suppress bitter taste via bitter taste receptor(s). This is the first report which defines the interaction between bitter and umami taste in taste receptor level.