Novel Umami Peptides from Mushroom (Agaricus bisporus) and Their Umami Enhancing Effect via Virtual Screening and Molecular Simulation.

This study aimed to identify novel umami peptides in Agaricus bisporus and investigate their umami enhancing effect. We virtually screened 155 potential umami peptides from the ultrasound-assisted A. bisporus hydrolysate according to Q values, iUmami-SCM, Umami_YYDS, and Tastepeptides_DM models, and molecular docking. Five peptides (AGKNTNGSQF, DEAVARGATF, REESDFQSSF, SEETTTGVHH, and WNNDAFQSSTN) were synthesized for sensory evaluation and kinetic analysis. The result showed that the umami thresholds of the five peptides were in the range of 0.21-0.40 mmol/L. Notably, REESDFQSSF, SEETTTGVHH, and WNNDAFQSSTN had low dissociation constant (KD) values and high affinity for the T1R1-VFT receptor. The enhancing effect of the three peptides with MSG or IMP was investigated by sensory evaluation, kinetic analysis, and molecular dynamics simulations. In stable complexes, ARG_277 in T1R1 played a major role in umami peptide binding to T1R1-VFT. These results provide a theoretical basis for future screening of umami peptides and improving the umami taste of food containing mushrooms.

Umami taste evaluation based on a novel mouse taste receptor cell-based biosensor.

Umami, a taste sensation known for its savory and delicious properties, has garnered considerable attention from both consumers and the food industry. However, current understanding and evaluation of umami characteristics remain limited, presenting a long-standing issue. To address this challenge, we have developed a self-assembled biosensor based on matured taste receptor cells (TRCs), obtained through isolation and culture of taste stem cells. TRCs, as the recognition element, were mounted onto the surface of a glassy carbon electrode (GCE) treated with gold nanoparticles (AuNPs) and poly-L-lysine (PLL). Key parameters including the cell incubation time and concentration were optimized to ensure the optimal performance of the TRCs-based biosensor. AuNPs were deposited onto the GCE surface via 90 s electrochemical reduction. TRCs concentration of 106 cells/mL and incubation time of 12 h were chosen by electrochemical characterization. Using this novel, rapid, and sensitive TRCs-based biosensor, we successfully detected L-monosodium glutamate (MSG) and other umami substances, demonstrating a good linear relationship within the range of 10-9 - 10-5 M between response signals and concentration of MSG stimuli. Our results provide insights into taste signal transduction mechanisms and suggest the potential for biomimetic sensors in intelligent perception applications.

A novel umami electrochemical biosensor based on AuNPs@ZIF-8/Ti3C2 MXene immobilized T1R1-VFT.

The bioelectronic tongues based on taste receptors have been emerging with human-like taste perception. However, the practical applications of the receptor-based biosensors were restricted by their narrow and low dynamic ranges. Here, a novel immobilization strategy based on AuNPs@ZIF-8/Ti3C2 MXene was developed to immobilize the umami ligand binding domain (T1R1-VFT), to fabricate an umami biosensor for umami substances detection. Through the synergic effect of AuNPs@ZIF-8 and Ti3C2 MXene, the capacity to load T1R1-VFT was effectively increased, and the response signal was also amplified by approximately 3 times. The proposed biosensor showed an ultrawide dynamic range of 10-11-10-3 M, and a high upper limit of detection, which was closer to the human taste threshold and suitable for detecting foods rich in umami substances. Additionally, the biosensor was successfully applied to detect real samples and analyze the synergistic effects of binary umami substances.

Exploring the relationships between perceived umami intensity, umami components and electronic tongue responses in food matrices.

Umami intensity promotes food flavor blending and food choice, while a universal quantification procedure is still lacking. To evaluate perceived umami intensity (PUI) in seven categories of foods, modified two-alternative forced choice (2-AFC) method with monosodium glutamate as reference was applied. Meanwhile, we explored whether equivalent umami concentration (EUC) by chemical analysis and electronic tongue (E-tongue) are applicable in PUI quantification. The results indicated that EUC was appropriate in quantifying PUI of samples from meat, dairy, vegetable and mushroom groups (r = 1.00, p < 0.05). Moreover, models with a good prediction capacity for PUI and EUC (R2 > 0.99) were established in separated food categories by back propagation neural networks, where E-tongue data were set as input. This study explored the effectiveness of the three methods in evaluating the PUIs of various foods, which provides multiple choices for the food industry.

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.

Human-like performance umami electrochemical biosensor by utilizing co-electrodeposition of ligand binding domain T1R1-VFT and Prussian blue.

Over the past decades, due to the desire for artificial umami flavors, apparatuses for detecting the umami taste have constantly been developed. Nevertheless, most information on umami is still acquired through human sensory assessment, which makes it difficult to establish an umami standard or quantify the umami flavor. In this study, the ligand binding domain called venus flytrap (VFT) domain of the umami taste receptor protein T1R1 was used as a recognition element, and an electrochemical biosensor based on a double-signal amplification strategy was constructed using single-walled carbon nanotubes (SWCNTs) and Prussian blue (PB). Moreover, the umami taste of four representative umami substances, inosine-5'-monophosphate (IMP), monosodium L-glutamate (MSG), beefy meaty peptide (BMP), and sodium succinate (WSA), were successfully quantitatively measured using differential pulse voltammetry (DPV) at an electrochemical workstation. Based on an equation (S/N = 3), the low detection limits (LODs) of IMP, MSG, BMP, and WSA were 0.1, 0.1, 0.1, and 0.01 pM, respectively. Meanwhile, a normalized signal intensity of more than 90% was kept for 4 days. The results showed that the biosensor could be used to detect umami substances with high sensitivity and selectivity, and was shown to have human-like performance. To develop the T1R1-VFT biosensor using the above-mentioned method, we utilized the ligand binding domain of the human umami receptor, rather than the entire umami receptor protein, which had a complex structure, having the following advantages: volume reduction, simplicity, and stability. This method has great potential for the detection of umami tastes, instead of using sensory evaluation, and for the development of new artificial flavorings.

Comparison of physicochemical and umami characterization of aqueous and ethanolic Takifugu obscurus muscle extracts.

Most umami substances were developed in aqueous extracts. In this study, we compared the molecular weight distributions and sensory characteristics of ethanol and aqueous Takifugu obscurus muscle extracts, and assessed their taste-related metabolites and peptide profile (<3 kDa) using nuclear magnetic resonance and nano liquid chromatography-mass spectrometry. The potential antioxidant peptide in ethanolic fraction was screened using Peptide Ranker, BIOPEP and quantum chemical simulations. The results indicated that 60% ethanolic extract fraction (60%-F) had the highest umami intensity and more palatable overall taste among all pufferfish extracts. It can be caused by more umami enhancing components such as Asp, Asn, Ala and 5'-AMP, and considerable umami-potential smaller peptides in 60%-F. 60%-F also showed an antioxidant activity, and several antioxidant peptides was screened. The present study indicated the relationship between extract solution and taste characterization, which provided more possibility for the exploitation of umami substances and screening potential activity peptides.

Seven novel umami peptides from Takifugu rubripes and their taste characteristics.

Pufferfish is worldwide known for its umami taste. Previous studies showed that umami peptide played a key role in taste perception of pufferfish. In order to more explain the umami taste of pufferfish in details, this study was aimed to identify more umami peptides from pufferfish. The extraction of Takifugu rubripes (T. rubripes) muscle after heating and ultrasound treatment was isolated by consecutive chromatography combined with sensory evaluation. The results showed that seven umami peptides from 300 to 3000 Da molecular weight range fractions were firstly identified by nano-liquid chromatography quadrupole time of flight mass spectrometry (Nano-LC/Q-TOF-MS), and peptide sequences are HLQLAIR, DPLRGGYY, AGLQFPVGR, LLLPGELAK, AGFAGDDAPR, GYSFTTTAER and DAGVIAGLNVLR. The taste characteristics of seven peptides were analyzed based on sensory evaluation, and their umami thresholds were in the ranges of 0.06-0.27 mM. Peptide sequences source analysis found that actin was one important taste-active precursor of the umami peptides in T. rubripes.

Characterization of Jinhua ham aroma profiles in specific to aging time by gas chromatography-ion mobility spectrometry (GC-IMS).

A rapid method for analyzing of Jinhua ham samples in different aging time was created based on gas chromatography-ion mobility spectrometry (GC-IMS). The GC-IMS chromatograph provided information regarding the identities and intensities of 37 volatile flavor compounds, including both monomers and dimers. Principal component analysis (PCA) effectively distinguished the variation in the aroma of the Jinhua hams specific to aging time. Alcohol (octanol, 2-methylbutanol), ketones (2-butanone, 2-hexanone, 2-heptanone, acetoin, gamma-butyrolactone), aldehydes (butanal, 3-methylbutanal), ester (propyl acetate) and carboxylic acids (3-methylbutanoic acid) were considered as the main volatile compounds in the Jinhua ham samples. This GC-IMS method, then, proved to be feasible for the rapid and comprehensive detection of volatile compounds in Jinhua hams, and multivariance analysis (i.e.: PCA) was able to provide information related to aging time.

Quantitative analyses of the umami characteristics of disodium succinate in aqueous solution.

Disodium succinate (WSA) contributes to umami taste in seafoods and it is abundantly found in scallops. However, the actual application of WSA in foods is limited due to a lack of understanding of its taste characteristics and stability. In this study, two-alternative forced choice method was used to determine the relative umami intensity of WSA compared to monosodium glutamate, as well as the relative umami intensity under different conditions (pH and temperature). WSA concentration-taste intensity curve was established, which fitted well with a logarithmic-linear regression (R2 = 0.96). WSA exhibited the strongest umami intensity at 25 °C, 0.1% Na+ addition, and pH 7.5. It also had a good thermal stability, which met the needs of high temperature heating during food processing. In conclusion, this research provided useful information on umami characteristics of WSA and the results widen the application of WSA in the food industry.