Monosodium Glutamate Solution Research Articles

Multienzyme-Mediated Dual-Channel Magnetic Relaxation Switching Taste Biosensor (D-MRSTB) for Simultaneous Detection of Umami Compounds and Synergistic Enhancement in Food.

Umami substances play a significant role in the evaluation of food quality, and their synergistic enhancement is of great importance in improving and intensifying food flavors and tastes. Current biosensors available for umami detection still confront challenges in simultaneous quantification of multiple umami substances and umami intensities. In this study, an innovative dual-channel magnetic relaxation switching taste biosensor (D-MRSTB) was developed for the quantitative detection of representative umami substances. The multienzyme signal of D-MRSTB specifically catalyzes the umami substances of interest to generate hydrogen peroxide (H2O2), which is then used to oxidate Fe2+ to Fe3+. Such a valence-state transition of paramagnetic ions was utilized as a magnetic relaxation signaling switch to influence the transverse magnetic relaxation time (T2) within the reaction milieu, thus achieving simultaneous detection of monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP). The biosensor showed good linearity (R2 > 0.99) in the concentration range of 50-1000 and 10-1000 μmol/L, with limits of detection (LOD) of 0.61 and 0.09 μmol/L for MSG and IMP, respectively. Furthermore, the biosensor accurately characterized the synergistic effect of the mixed solution of IMP and MSG, where ΔT2 showed a good linear relationship with the equivalent umami concentration (EUC) of the mixed solution (R2 = 0.998). Moreover, the D-MRSTB successfully achieved the quantitative detection of umami compounds in real samples. This sensing technology provides a powerful tool for achieving the detection of synergistic enhancement among umami compounds and demonstrates its potential for application in the food industry.

Can humans smell tastants?

Although studies have shown that olfaction may contribute to the perception of tastant, literature is scarce or circumstantial, especially in humans. This study aims to (i) explore whether humans can perceive solutions of basic prototypical tastants through orthonasal and retronasal olfaction and (ii) to examine what volatile odor compounds (VOCs) underlie this ability. Solutions of 5 basic tastants (sucrose, sodium chloride, citric acid, monosodium glutamate [MSG], quinine) dissolved in water, and 2 fatty acids (oleic and linoleic acid) dissolved in mineral oil were prepared. Triangle discrimination tests were performed (n = 41 in duplicate) to assess whether the tastant solutions can be distinguished from blanks (solvents) through ortho- and retronasal olfaction. Participants were able to distinguish all tastant solutions from blank through orthonasal olfaction. Only sucrose, sodium chloride, oleic acid, and linoleic acid were distinguished from blank by retronasal olfaction. Ethyl dichloroacetate, methylene chloride, and/or acetone were identified in the headspace of sucrose, MSG, and quinine solutions but not in the headspace of water, sodium chloride, and citric acid solutions. Fat oxidation compounds such as alcohols and aldehydes were detected in the headspace of the oleic and linoleic acid solutions but not the mineral oil. We conclude that prototypical tastant solutions can be discriminated from water and fatty acid solutions from mineral oil through orthonasal olfaction. Differences in the volatile headspace composition between blanks and tastant solutions may have facilitated the olfactory discrimination. These findings can have methodological implications for future studies assessing gustatory perception using these prototypical taste compounds.

Identifying Umami Peptides Specific to the T1R1/T1R3 Receptor via Phage Display.

Umami peptides are small molecular weight oligopeptides that play a role in umami taste attributes. However, the identification of umami peptides is easily limited by environmental conditions, and the abundant source and high chromatographic separation efficiency remain difficult. Herein, we report a robust strategy based on a phage random linear heptapeptide library that targets the T1R1-Venus flytrap domain (T1R1-VFT). Two candidate peptides (MTLERPW and MNLHLSF) were readily identified with high affinity for T1R1-VFT binding (KD of MW-7 and MF-7 were 790 and 630 nM, respectively). The two peptides exhibited umami taste and significantly enhanced the umami intensity when added to the monosodium glutamate solution. Overall, this strategy shows that umami peptides could be developed via phage display technology for the first time. The phage display platform has a promising application to discover other taste peptides with affinity for taste receptors of interest and has more room for improvement in the future.

The Effects of Apocynin on Monosodium Glutamate Induced Liver Damage of Rats

Monosodium glutamate (MSG) is found in refined foods. Apocynin (APO) is a selective NADPH oxidase (NOX) inhibitor. The aim of this experimental study was to investigate possible effects of MSG and the curative effects of APO in rats. Twenty-eight male Sprague-Dawley rats were randomly divided into four groups (Normal control, APO, MSG and MSG + APO, n:7 for each group). The MSG and MSG + APO groups received 120 mg/kg MSG solution orally for 28 consecutive days. The APO and MSG + APO groups received 25 mg/kg APO solution orally for 5 days until the end of the experiment. At the end of the experiment, all rats were sacrificed and liver tissue and blood samples were taken for histological, ultrastructural, and biochemical analyses. In the MSG group, vacuolization and loss in glycogen content in the hepatocytes, leukocyte infiltration and fibrosis in the liver parenchyme and portal triads, were observed. Terminal deoxynucleotidyl transferase dUTP (TUNEL)-positivity and NADPH oxidase (NOX)-2-positivity were higher in the MSG group compared with the other experimental groups. The concentrations of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total bilirubin, malondialdehyde (MDA), and myeloperoxidase (MPO) were higher, whereas albumin, glutathione (GSH), and superoxide (SOD) levels were lower in the MSG group. All these data has been reversed in MSG + APO group. The histological and biochemical criteria indicated the prominent ameliorating effect of APO on MSG -induced liver injury.

Identification of Novel Umami Peptides in Chicken Breast Soup through a Sensory-Guided Approach and Molecular Docking to the T1R1/T1R3 Taste Receptor.

Ultrafiltration combined with nanoliquid chromatography quadrupole time-of-flight mass spectrometry (nano-LC-QTOF-MS) and sensory evaluation was used to separate and identify umami peptides in chicken breast soup. Fifteen peptides with umami propensity scores of >588 were identified from the fraction (molecular weight ≤1 kDa) using nano-LC-QTOF-MS, and their concentrations ranged from 0.02 ± 0.01 to 6.94 ± 0.41 μg/L in chicken breast soup. AEEHVEAVN, PKESEKPN, VGNEFVTKG, GIQKELQF, FTERVQ, and AEINKILGN were considered as umami peptides according to sensory analysis results (detection threshold: 0.18-0.91 mmol/L). The measurement of point of subjective equality showed that these six umami peptides (2.00 g/L) were equivalent to 0.53-0.66 g/L of monosodium glutamate (MSG) in terms of umami intensity. Notably, the sensory evaluation results showed that the peptide of AEEHVEAVN significantly enhanced the umami intensity of the MSG solution and chicken soup models. The molecular docking results showed that the serine residues were the most frequently observed binding sites in T1R1/T1R3. The binding site Ser276 particularly contributed to the formation of the umami peptide-T1R1 complexes. The acidic glutamate residues observed in the umami peptides were also involved in their binding to the T1R1 and T1R3 subunits.

Salty and umami tastes perception in hypertensive patients and its relationship to dietary sodium intake

Background: Reducing the dietary sodium intake is one of the most important factors for controlling blood pressure. The changes that occur in perceiving saltiness and umami tastes in people with hypertension can be associated with the level of sodium intake. The aim of this study was to investigate the gustatory perception of these two tastes in patients with hypertension and its association with the level of dietary sodium consumed by these patients. Material and methods: In this case control study, 40 patients with hypertension and 40 healthy individuals were chosen. The blood pressure was measured for both groups. The power of perceiving saltiness and umami tastes was investigated using sodium chloride and monosodium glutamate solutions respectively both with concentrations of 200 mmol/lit. The individuals specified the power of each taste along a 10-number criterion. Based on the compounds of foods in Iran, the level of sodium consumed per day was calculated by food frequency questionnaire. The data were analyzed by Mann-Whitney, Pearson, Spearman tests. Results: The mean saltiness perception in the control and case group was 5/8 and 6/6 respectively(p < 0/05) and the mean umami perception the control and case group was 5/5 and 7/6 respectively (p < 0/05). There was an inverse relationship between the level of sodium intake and perceived intensity of saltiness perceptionin case group (p < 0.05).The level of sodium intake had no relationship with perceived intensity of umami taste in none of the groups (p > 0.05). There was also a direct relationship between blood pressure and intensity of perceiving umami taste in case group (p < 0.05).However, no significant relationship was found between blood pressure and the intensity of perceiving saltiness (p > 0.05). Conclusion: Perceived intensity of saltiness perception in case group higher than control group also perceived intensity of umami perception in case group higher than control group. With increase in the blood pressure, the power of perceiving saltiness and umami increases; with increase in sodium intake, saltiness perception diminishes, but umami perception is left unaffected.

A portable device based on an electrical conductivity sensor for the detection of monosodium glutamate (MSG) in soupy foods

In everyday life, food is made with various taste images, including the savory taste obtained from monosodium glutamate (MSG). Although it is allowed as a food ingredient, excessive use of MSG and continuous consumption will have adverse effects on health. The effects of consuming MSG excessively on the body's organs include brain, ovarian, testicular, liver, kidney, heart, and respiratory disorders. MSG detection using technology is needed to control the consumption of MSG in the body. Hence, this study was focused on creating a portable device for detecting monosodium glutamate (MSG) in soupy foods: meatball soup and chicken soup. 3 mg of MSG was applied to each solution sample and four MSG brands, including SS, MW, AM, and MR. The concept of this prototype is based on the conductivity value and total dissolved solids (TDS) in the MSG solution. These solutions can produce an electrolyte because there is a sodium salt content in the MSG solution and water. The electrolyte solution can conduct electricity. An electrical conductivity sensor was installed in this prototype and these sensors included two electrode plates, a positive electrode (anode) and a negative electrode (cathode) with a distance of ± 1 cm. The conductivity sensor begins by starting a sensor into an electrolyte solution and, given an electric voltage input, changes to the value of the electric voltage. The sensor can be read and detect the MSG level in the solution. Then, the data are received and recorded in the DRF analog which is to process the signal from the sensor into analog form, and the data is sent to the Arduino Nano as a microcontroller. From the experiment result, the average conductivity value and TDS value of meatball soup are 21.98 mS and 7.91 Mg/I, while the average conductivity value and TDS value of Chicken Soto are 16.92 mS and 6.08 mg/I. This prototype was successfully created and implemented for the MSG detection in soupy foods.

Sucrose Inclusion in Gestating and Lactating Diets of Sows Modifies the Feeding Behavior of Post-Weaning Pigs for Sweet Solutions.

Pigs display an innate preference for sweet taste compounds such as sucrose. However, the influence of sucrose supplementation into maternal diets has not been examined in pigs. We tested the hypothesis that sucrose inclusion into sows’ diets would modify the feeding behavior of post-weaning pigs for sweet and umami solutions. Twenty-two sows (85 days of gestation) were used. They randomly received a gestational and lactating diet with or without 50 g/kg of sucrose. Different sucrose and monosodium glutamate solutions were offered to the progeny to analyze different intake behavior measurements during nursery. Pigs born from treated sows presented a higher sucrose threshold than control animals (15 mM vs. 0.1 mM, p = 0.032) and displayed decreased sensory-motivated intake for this disaccharide (p < 0.023). Sucrose consumption decreased (p < 0.021) in pigs born from treated sows, as well as the consumption patterns for the less concentrated solutions (p < 0.014). The inclusion of sucrose into maternal diets (gestation and lactation) could modified pigs’ feeding behavior after weaning when offered sweet solutions, which speaks against the practicality of this supplementation in pig production systems.

Characteristics of umami peptides identified from porcine bone soup and molecular docking to the taste receptor T1R1/T1R3

To study the umami peptides derived from porcine bone soup, ultrafiltration fractions with molecular weight less than 1 kDa were screened by sensory analysis which showed higher umami intensity. Four potential umami peptides were identified from the screened fractions by Nano-LC-Q-TOF-MS/MS, among which FSGLDGAK, FAGDDAPR and FSGLDGSK were proved to have dominant umami taste by sensory evaluation and electronic tongue. The threshold of the three peptides ranged from 0.1 mM to 0.89 mM. In addition, FSGLDGSK had the highest umami intensity and exhibited a significant umami-enhancing effect in a 0.35% monosodium glutamate solution. The results of molecular docking simulation showed that the key binding sites of taste receptor type 1 member 1 (His71, Asp108 and Glu301) and taste receptor type 1 member 3 (Glu48, Ser104 and His145) were crucial to the interaction with the umami peptides. Besides, electrostatic interaction and hydrogen bond mainly contributed to the mechanism of umami taste.

Additive Effects of L-Ornithine on Preferences to Basic Taste Solutions in Mice.

In addition to the taste receptors corresponding to the six basic taste qualities—sweet, salty, sour, bitter, umami, and fatty—another type of taste receptor, calcium-sensing receptor (CaSR), is found in taste-bud cells. CaSR is called the ‘kokumi’ receptor because its agonists increase sweet, salty and umami tastes to induce ‘koku’, a Japanese word meaning the enhancement of flavor characters such as thickness, mouthfulness, and continuity. Koku is an important factor for enhancing food palatability. However, it is not well known whether other kokumi-receptors and substances exist. Here, we show that ornithine (L-ornithine but not D-ornithine) at low concentrations that do not elicit a taste of its own, enhances preferences to sweet, salty, umami, and fat taste solutions in mice. Increased preference to monosodium glutamate (MSG) was the most dominant effect. Antagonists of G-protein-coupled receptor family C group 6 subtype A (GPRC6A) abolished the additive effect of ornithine on MSG solutions. The additive effects of ornithine on taste stimuli are thought to occur in the oral cavity, and are not considered post-oral events because ornithine’s effects were confirmed in a brief-exposure test. Moreover, the additive effects of ornithine and the action of the antagonist were verified in electrophysiological taste nerve responses. Immunohistochemical analysis implied that GPRC6A was expressed in subsets of type II and type III taste cells of mouse circumvallate papillae. These results are in good agreement with those reported for taste modulation involving CaSR and its agonists. The present study suggests that ornithine is a kokumi substance and GPRC6A is a newly identified kokumi receptor.

An ultra-robust fabric-embedded PVDF membrane fabricated by NTIPS method and its application for monosodium glutamate concentration in membrane distillation

This study proposed a novel strategy to fabricate highly permeable and robust supported membranes for membrane distillation, via a nonsolvent thermally induced phase separation method. Different from traditional supported membranes cast on non-woven fabrics, a well-integrated fabric-embedded PVDF (FE-PVDF) membrane was successfully obtained using polyamide 66 gauze supports. The optimal FE-PVDF membrane PA-120 exhibited an interesting structure with pseudo Janus function, which entailed hydrophobic bulk membrane property but a pseudo hydrophilic bottom surface due to the presence of water-filled “50 μm grade” pores. The PA-120 exhibited a DCMD flux of 68.5 kg.m−2.h−1 at 70 °C with synthetic saline solution and exceptional tensile strength of 21 MPa (lateral)/21 MPa (longitudinal), which was 1.4-fold and 23-fold higher than that of the unsupported benchmark, respectively. The concentration of 10 wt% monosodium glutamate solution with PA-120 was demonstrated at 70 °C up to 55 wt% when crystallization was observed, The flux showed a minor decrease by 16.3% until 40 wt% and a subsequent decline towards 55 wt%. Repeated concentration cycles were conducted with intermediate membrane rinsing by fresh feed, demonstrating highly recoverable performance. This preliminary study brings new perspectives towards pushing the limits of current lab-made MD membranes.

Enhanced voltammetric response of monosodium glutamate on screen-printed electrodes modified with NiAl layered double hydroxide films

Cyclic voltammetry preliminary studies carried out on commercial carbon screen-printed electrodes (SPEs) confirmed an irreversible reduction process of glutamate in aqueous solutions of monosodium glutamate (MSG). Modified carbon SPEs coated with Ni3Al-CO3 layered double hydroxide (NiAl-LDH) film were prepared by pulse laser deposition (at 1064, 532, 355 and 266 nm wavelength). Also, carbon electrodes were covered with NiAl-LDH film and NiAl LDH + graphene composite film by matrix assisted pulsed laser evaporation (at 266 nm). Both prepared LDH powder used as laser target and LDH films were characterized by XRD. LDH and LDH-composite films were characterized by FTIR spectroscopy, SEM, AFM and contact angle measurements. All cyclic voltammograms recorded at 0.08 V/s on bare carbon screen-printed electrode and modified electrodes coated with different LDH films exhibited a linear dependence for cathodic peak current vs. MSG concentration. Compared to the slope value (2.563±0.262 μAcm−2μM−1) obtained in the case of bare carbon screen-printed electrode, the sensitivity performances of the modified electrodes were substantially increased. The best results were recorded under optimum conditions for graphene composite film, namely a value of 8.567±0.565 μAcm−2μM−1. Cyclic voltammetry tests of modified electrodes prepared by laser technique with addition of radiofrequency plasma indicated a negative effect on surface electroactivity, with drastically reducing the quality of MSG cathodic voltammetric signal.

Immunobiochemical Repercussions of Prednisone Treatment in Wistar Rats in a Model of Transgenerational Obesity

Prednisone is used as immunosuppressive and anti-inflammatory, and its use may trigger several adverse effects, especially in obese individuals and their next generations. The objective was to evaluate the interaction between obesity and immunobiochemical parameters in rats treated with prednisone in a transgenerational obesity model. Obesity was neonatally induced by monosodium glutamate solution administration in female Wistar rats (MSG), while in other females was administered saline solution (SAL). After 90 days, rats were classified as obese according to the Lee Index and then mated to obtain the next generation. The male offspring rats from SAL dams were classified as control group (NOb/SAL), while obese male offspring from MSG dams were separated into two groups: non-obese (NOb/MSG) and obese (Ob/MSG), all n=12, following the Lee Index score. After 90 days of life, rats were exposed to daily oral prednisone treatment (1.25mg/Kg/day) for 21 days, where the Oral Tolerance Test Glucose (OGTT) was performed on the 1st and 20th days of treatment and body weight measured weekly. On the last day, blood samples were collected for leukogram, immunoglobulins and biochemical measurements. The OGTT showed higher transaminases and glucose levels in NOb/MSG and Ob/MSG groups, especially at 60’ and 120’ and the area under the curve from OGTT. These groups also decreased the leukocyte and immunoglobulin G; and a triglycerides reduction only in Ob/MSG group. We can conclude the use of prednisone in transgenerational obesity evidenced the occurrence of glucose intolerance, hepatotoxicity, and immunosuppressive effect, suggesting caution in its use under these conditions.

The Effect of Giving Red-fleshed Watermelon Juice (Citrullus lanatus (Thunb.)) on Pregnant White Mice (Mus Musculus) Exposed by Monosodium Glutamate (MSG) Orally on the Number and Morphology of Fetus

Introduction: Infertility can occur due to the presence of free radicals. One of the most popular of free radical is monosodium glutamate. Free radicals from monosodium glutamate can be prevented by antioxidant compounds. Red-fleshed-fleshed watermelon is a fruit that contains antioxidant compound such as lycopene. Aim: This research was conducted to see the effect of red-fleshed-fleshed watermelon juice on the fetus including number, morphology, visual abnormalities and body weight of pregnant white mice exposed to monosodium glutamate solution orally. Total of 25 female white mice aged around 2-3 months were used as test animals. Methods: Pregnant white mice were divided into 5 test groups. Group I and II served as negative controls (whithout treatment) and positive controls (exposed to monosodium glutamate solution orally at dose of 1g/kgBW). Group III was given a solution of monosodium glutamate orally at dose of 1 g/KgBW added red-fleshed-fleshed watermelon juice at dose of 1.4 g/kgBW. Group IV was given solution of monosodium glutamate orally at dose of 1 g/KgBW added red-fleshed-fleshed watermelon juice at dose of 4.2 g/kgBW. The research data were processed using the one-way ANNOVA test. Results: The result showed that mice body weight, fetal number and morphology (body weight, body length, tail length, and head diameter) did not significantly influence (p>0.05). However, it significantly affected the weight gain of mice during pregnancy. However, it significantly affected the weight gain of mice during pregnancy day 6 to day 17 of pregnancy (p<0.05) and found abnormalities in the fetus such as low birth weight (LBW) and haemorrhage in group II and III. Conclusion: It can be concluded that watermelon juice at dose of 2.8 g/kgBW and 4.2 g/kgBW are effective in ward offfree radicals from monosodium glutamate orally at dose of 1 g/kgBW.

Influence of monosodium glutamate consumption by albino rats during pregnancy and lactation on their offspring

The consequences of dietary intake of significant amounts of monosodium glutamate (MSG) are the excess body weight; structural and functional disorders of the central nervous system, liver, kidneys. We have not found information about the influence of excessive using of the MSG by a woman during pregnancy and lactation on the fetus and infants. The aim of the study was the experimental evaluation of the MSG consumption consequences during pregnancy and lactation to the offspring health. Material and methods. The offspring of 3-month old pregnant female white Wistar rats, who received 1% MSG solution (200 mg per kg of body weight per day) ad libitum as the source of liquid during the pregnancy and lactation, have been studied (MSG group). The control group included offspring of pregnant female rats that received water as the source of liquid. In 25-day-old offspring histological examination and morphometry of the nucleo-nucleolar apparatus of neurons in the neocortex of the proper parietal lobe, cardiomyocytes of the subendocardial zones of the left and right ventricles have been performed. Gravimetry have been also carried out (body weight and weight of brain, heart, liver, kidney, thymus and spleen); mitotic activity of anterior corneal epithelium has been evaluated, the state of erythrocyte membranes have been analyzed by the method of acid erythrograms; behavioral tests "Open field", "The elevated plus-maze test", "Hanging on a horizontal wire" have been performed. Results. MSG consumption during pregnancy and lactation led to an increase of brain (by 19.1%) and kidneys (by 7.8%) relative masses; masses of thymus and spleen were decreased. Significant decrease of locomotor activity and increase of time of hanging in "horizontal wire test" were registered. A histological study showed an increase in the number of nucleoli in the neurons of the V layer of the neocortex of the proper parietal lobe (control - 1.56±0.09; MSG group - 1.81±0.07, р=0.03); decrease of the nucleolar parameters of cardiomyocytes; increase of mitotic activity of anterior corneal epithelium (control - 4.021±0.612‰; MSG group - 6.985±0.889‰, р=0.019). A decrease of the resistance of erythrocyte membranes to acid hemolysis was also registered. Conclusion. The results obtained indicate the effect of oral consumption of MSG food additive during pregnancy and lactation on the organism of the offspring.

Monosodium glutamate administration early in life alters pineal melatonin nocturnal profile in adulthood

The pineal gland synthesizes melatonin exclusively at night, which gives melatonin the characteristic of a temporal synchronizer of the physiological systems. Melatonin is a regulator of insulin activities centrally and also peripherally and its synthesis is reduced in diabetes. Since monosodium glutamate (MSG) is often used to induce the type 2 diabetic and metabolic syndrome in animal models, the purpose of this work is to evaluate the potential effects of MSG given to neonates on the pineal melatonin synthesis in different aged male and female rats. Wistar rats were subcutaneously injected with MSG (4mg/g/day) or saline solution (0.9%) from the second to eighth post-natal day. The circadian profiles both melatonin levels and AANAT activity were monitored at different ages. Body weight, naso-anal length, adipose tissues weight, GTT, ITT and serum insulin levels were also evaluated. Typical obesity with the neonatal MSG treatment was observed, indicated by a great increase in adipose depots without a concurrent increase in body weight. MSG treatment did not cause hyperglycemia or glucose intolerance, but induced insulin resistance. An increase of melatonin synthesis at ZT 15 with phase advance was observed in in some animals. The AANAT activity was positively parallel to the melatonin circadian profile. It seems that MSG causes hypothalamic obesity which may increase AANAT activity and melatonin production in pineal gland. These effects were not temporally correlated with insulin resistance and hyperinsulinemia indicating the hypothalamic lesions, particularly in arcuate nucleus induced by MSG in early age, as the principal cause of the increase in melatonin production.

Exploring Anhedonia in Kennelled Dogs: Could Coping Styles Affect Hedonic Preferences for Sweet and Umami Flavours?

Simple SummaryKennelled dogs are susceptible to suffer chronic stress when social interactions with conspecifics and spatial needs are long-term restricted. Chronic stress may affect pleasure perception of food and solutions in dogs as observed in several animals, a phenomenon known as anhedonia. However, little information exists on how different coping styles could prevent the onset of anhedonia. Fourteen kennelled Beagle dogs were used to study the acceptability and preference for different dilute palatable sucrose and monosodium glutamate (MSG) solutions. Coping style of animals was previously evaluated through a modified human-approach test. This test consisted in assessing whether or not dogs approached an unfamiliar human when a feeding opportunity was presented, classifying them as close dogs (CD; proactive) or distant dogs (DD; reactive) respectively. It was observed that DD presented a lower intake of both sucrose and MSG dilute solutions compared with CD. Moreover, DD exhibited a higher consumption of MSG than CD at the highest concentrations, supporting that their intake depends on solution palatability. Finally, DD did not prefer sucrose or MSG solutions over water at any dilute solution offered. Together, these results suggest that dogs that are categorized as reactive animals could diminish their ability to perceive dilute palatable solutions reflecting depressive-like behaviours such as anhedonia.Kennelled dogs are at risk of suffering chronic stress due to long-term spatial, social and feeding restrictions. Chronic stress may decrease the dogs’ capacity to feel pleasure when facing hedonic experiences, modifying their perception for palatable ingredients. However, different abilities to cope with environmental stressors could prevent the onset of anhedonia. Fourteen kennelled Beagle dogs were used to study the acceptability and preference for different dilute sucrose and monosodium glutamate (MSG) solutions. Coping style of animals was previously evaluated through a human approach test (HAT) and classified as close dogs (CD; proactive) or distant dogs (DD; reactive) according to whether or not they approached an unfamiliar human when a feeding opportunity was presented. Consumption results were analysed taking into account the sucrose/MSG concentrations, HAT (CD or DD), age, and weight of the animals. DD presented a lower intake of sucrose (p = 0.041) and MSG (p = 0.069) solutions compared with CD. However, DD exhibited a higher consumption of MSG than CD at its highest concentrations, supporting that their intake depends on solution palatability. Finally, DD did not prefer sucrose or MSG solutions over water at any dilute solution offered. Together, these results suggest that dogs that are categorized as reactive animals could diminish their ability to perceive dilute palatable solutions, reflecting depressive-like behaviours as anhedonia.

Enhancement of saltiness perception by odorants selected from Chinese soy sauce: A gas chromatography/olfactometry-associated taste study

Odor-taste interaction has become a popular salt reduction method. In this study, the odorants associated with saltiness in soy sauce were selected by gas chromatography/olfactometry-associated taste (GC/O-AT), and their ability to induce saltiness/umami enhancement was verified by sensory evaluation. A total of 30 taste-associated odorants were perceived, including 5 saltiness-associated and 2 umami-associated odorants. Among them, 3-(methylthio)propanal, 1-octen-3-ol, 3-(methylthio)-1-propanol, and 2,5-dimethylpyrazine could significantly enhance saltiness of 0.3% NaCl solution (p < 0.05). Furthermore, 3-(methylthio)propanal, maltol, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (HDMF), dimethyl trisulfide, 3-(methylthio)-1-propanol and 1-octen-3-ol could also enhance the umami taste in 0.3% monosodium glutamate solution. Compared with zero or strong-salt-content (0.8%) solution, the saltiness of weak-salt-content (0.3%) was enhanced significantly by adding the odorant. These results suggest that salty food is an efficient source for selecting saltiness-enhancing odorants, which could be used to compensate NaCl reduction in food.

Endogenous opioid dependence after intermittent use of glucose, sodium chloride, and monosodium glutamate solutions.

In 2002, Colantuoni et al described the possibility of dependency in rats after intermittent, excessive consumption of a 25% glucose solution over a one‐week period. We hypothesized that the intermittent consumption of any tasty solution can lead to endogenous opioid dependency. Another aim was to determine whether dependency is connected to the taste of the consumed substance or with its physiological significance. Rats were maintained on chow and cyclic glucose, NaCl, or monosodium glutamate (MSG) solution for 8 days. On day 9, after a 12‐hr deprivation period and administration of intraperitoneally (IP) naloxone, the general withdrawal index was calculated as the sum of teeth chattering, head shaking, forepaw tremors, and wet dog shakes. Motor activity was also documented. After the intermittent consumption of any tasty solution, rats were found to demonstrate signs of endogenous opioid dependence. The development of dependence was not related to taste preferences or the amount of solution consumed. Intermittent use of essential substance with a pleasant taste, as glucose and sodium chloride, leads to the rapid development of endogenous opioid dependence. Withdrawal syndrome following the consumption of MSG solution is associated with the presence of sodium ions in the MSG molecule.

Threshold sensitivity to sodium glutamate receptors («umami taste») and glomerular filtration rate in bronchial asthma

Background. In experimental and clinical medicine, new data and ideas on the role of so-called “ectopic” chemosensory receptors expressed outside their canonical localizations have appeared. As for receptors for umami-substances, to date, certain data have been obtained on both receptors in the tongue and extraoral in the kidneys (monosodium glutamate as the best-known ligand). At the same time, the functions of these receptors are still not completely understood. The aim of the study was to assess the sensitivity of glutamate receptors to monosodium glutamate in bronchial asthma using the threshold measurement and to compare it with the glomerular filtration rate in the same patients. Patients and methods . 54 practically healthy individuals, 55 patients with bronchial asthma were examined. To assess the taste sensitivity to monosodium glutamate, solutions of monosodium glutamate were prepared at concentrations of 0.067; 0.1; 0.2; 0.3; 0.4; 0.5%. The concentration at which the taste of meat broth was felt was considered the threshold concentration of the sensation of umami taste. Glomerular filtration rate (eGFR) by CKD-EPI was calculated. Results. In patients with bronchial asthma, a significant direct correlation was found between the threshold measurement and the estimated glomerular filtration rate (high sensitivity to sodium glutamate correlates with a reduced glomerular filtration rate). Sensitivity to sodium glutamate is also directly related to indicators reflecting inflammation (the content of neutrophils, monocytes in peripheral blood, C-reactive protein, erythrocyte sedimentation rate). Conclusion. In bronchial asthma, the use of gustometry measurement has revealed the phenomenon of high sensitivity to monosodium glutamate, which correlates with a reduced glomerular filtration rate and inflammation ndices. It is suggested that the revealed features of glutamatergic signaling may serve as a common pathogenetic mechanism both in bronchial asthma and chronic kidney disease.