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

Correlation analysis of taste phenotype and Gynostemma pentaphyllum saponins using computer virtual screening and UPLC-(HR)MS/MS metabolomics

Gynostemma pentaphyllum, a popular tea ingredient, can be categorized into bitter, sweet, and tasteless varieties based on flavor. However, the metabolic causes of these disparities remain unclear. In this paper, sensory evaluation, untargeted metabolomic analysis using UPLC-QTOF-MS/MS, molecular docking and e-tongue testing were conducted to reveal and verify the structural characteristics and mechanisms underlying these different flavor substances. Component analysis indicated sweet saponins were characterized by glucose chains and protopanaxadiol-type aglycones featuring diagnostic ions m/z 459/475/491 in MS2- spectra; whereas bitter saponins typically featured at least one terminal rhamnose and the higher unsaturated sapogenins with diagnostic ions m/z 473/489/521. Virtual screening on T2R14 and e-tongue testing consistently validated gypenosides with more terminal rhamnoses or higher unsaturated aglycone tended to be more bitter. Docking analysis revealed PHE 172, TYR 159 and ALA 77 were the key amino residue sites in bitterness conduction via hydrophobic and hydrogen bonding interactions.

Decoding of novel umami peptides from corn fermented powder and its mechanism via multisensory techniques, virtual screening, and molecular simulation approaches

This study aimed to identify umami peptides in corn fermented powder (CFP) and investigate their umami enhancing effect. Ultrafiltration and ethanol precipitation was used to separate the umami peptides in CFP. Dynamic sensory evaluations were used to identify the peptide fraction with the intense umami taste, and the peptides in the fraction were identified by nano-liquid chromatography-tandem mass spectrometry. Subsequently, ten umami-enhancing peptide candidates were screened using an integrated virtual screening strategy. Molecular docking revealed that Ser382, Ser104, Leu334, Glu338 and Glu148 of the T1R1 and T1R3 taste receptors are important amino acid residues for binding of the ten umami peptides. Three umami peptides (VDW, WGDDP, and WPAGE) exhibited the stronger binding affinity with the umami receptors. Moreover, molecular dynamics simulation revealed that the T1R1/T1R3 formed stable complexes with the three umami peptides during the simulation. Sensory evaluation indicated that the three peptides exhibited diverse taste characteristics (detection thresholds:0.0315-0.0625 mg/mL). The sigmoid curve analysis further confirmed peptides were identified as synergistically (VDW and WGDDP) or additively (WPAGE) enhancing the umami of 3 mg/mL MSG solution. This study uncovers the mechanism of umami-peptide-driven taste in fermented corn products.

Screening and identification of novel umami peptides from yeast proteins: Insights into their mechanism of action on receptors T1R1/T1R3

This study aimed to unravel the peptide profiles of six distinct yeast protein samples and identify novel umami peptides within them. Peptide characteristics analysis support the proposition that yeast protein peptide pools represent exceptional reservoirs of umami peptides. Nine potential umami peptides were screened using the iUmami_SCM, UMPred-FRL, Umami_YYDS, Umami-MRNN, Innovagen, Expasy-ProtParam, and ToxinPred tools. Peptides AGVEDVY, LFEQHPEYRK, AFDVQ, GPTVEEVD, NVVAGSDLR, ATNGSR, and VEVVALND (1 mg/mL) were confirmed to possess umami taste, and the first five peptides exhibited significant umami-enhancing effects on 0.35 % monosodium glutamate. Molecular docking indicated that peptide residues His, Arg, Tyr, Asp, Gln, Thr, Ser, and Glu primarily bound to His71, Ser107/109/148, Asp147/218, and Arg277 of T1R1 and Ser104/146, His145, Asp216, Tyr218, and Ala302 of T1R3 through hydrogen bonds. This study enriches the umami peptide repository for potential food additive use and establishes a theoretical foundation for exploring taste compounds in yeast proteins and their broader applications.

Novel umami-enhancing peptides of beef M. Semimembranosus hydrolysates and interactions with the T1R1/T1R3 taste receptor

The taste mechanisms of beef umami and umami-enhancing peptides are not well understood. Therefore, novel umami and umami-enhancing peptides from beef M. semimembranosus hydrolysates were explored. Beef hydrolysates treated with Flavourzyme® showed an overall strong umami intensity compared to those treated with Alcalase®, papain, or Protamex®. The peptides were isolated via consecutive separation processes, and 31 potential umami peptides were identified. Molecular docking results showed that WGSEPIRIQ and TERGYSF had considerably low docking energies with the T1R1/T1R3 taste receptor through potential key binding sites for hydrogen bonding, including Ser48, Gly49, and Gln278 in T1R1, and Ser67, Asn68, and Arg247 in the T1R3 subunit. The taste of the identified peptides dissolved in ultrapure water was dominated by sourness. Instead, they demonstrated an umami-enhancing effect in the presence of monosodium glutamate. These results broaden our understanding of the taste mechanisms of beef umami-enhancing peptides and their potential applications as flavoring agents.

Efficient screening and discovery of umami peptides in Douchi enhanced by molecular dynamics simulations

In this study, a partial least squares discriminant analysis (PLS-DA) discriminant model for umami peptides was constructed based on molecular dynamics simulation data, achieving a R 2 value of 0.949 and a Q 2 value of 0.558. Using this novel model and bioinformatics screening methods, five new umami peptides (EALEATAQ, SPPTEE, SEEG, KEE, and FEE, with umami taste thresholds of 0.139, 0.085, 0.096, 0.060, and 0.079 mg/mL, respectively) were identified in Douchi. Molecular docking revealed that the residues ASN150 of T1R1, as well as SER170, GLU301 and GLN389 of T1R3, might be key amino acid residues for the binding of umami peptides to T1R1/T1R3. Molecular dynamics simulations revealed significant differences in the root-mean-square fluctuation (RMSF) values between the two complex systems of umami peptides-T1R1/T1R3 and non-umami peptides-T1R1/T1R3. The newly constructed umami peptide discriminant model can improve the accuracy of umami peptide screening and enhance the efficiency of discovering new umami peptides.

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

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

Identification of a novel peptide with anti-inflammatory activity from Binglangjiang buffalo fermented milk and its potential inhibitory mechanism in lipopolysaccharide-stimulated RAW264.7 cells

Binglangjiang buffalo fermented milk (BBFM) is rich in bioactive peptides and exhibits significant immunomodulatory activity, although the specific components and effects are not well understood. In this study, we investigated the anti-inflammatory activity peptides from BBFM using peptidomics and proteomics. A total of 769 peptides were identified using LC-MS/MS. Among these, a novel peptide (GPGAPADPGRPTG (GG13)), was screened out using LPS-stimulated RAW264.7 cells. The molecular weight of peptide GG13 was 1149.56 Da, and it exhibited high in-vitro safety and thermal stability. Furthermore, ELISA and Western blot analysis showed that peptide GG13 significantly inhibited the secretion of pro-inflammatory cytokines NO and TNF-α, as well as the expression of proteins iNOS and TNF-α in LPS-stimulated RAW264.7 cells, and proteomics analysis showed that peptide GG13 significantly down-regulated the protein expression of STAT1, NOS2, COX2, and CD40. The study provides a basis for further explore the development of health fermented milk products.

Identification and taste characteristics of novel umami peptides from Yanjin black bone chicken hydrolysates and their binding mechanism with umami receptor

This study aimed to obtain umami peptides from Yanjin black bone chicken and to investigate the formation mechanism of umami taste. The umami peptides were purified from the enzymatic hydrolysate of chicken using ultrafiltration (UF), gel filtration chromatography (GFC), and reversed-phase high-performance liquid chromatography (RP-HPLC). Potential novel umami peptides were then identified by nano-scale liquid chromatography-tandem mass spectrometry (nano-HPLC-MS/MS). Based on the predictions of iUmami-SCM and BIOPEP-UWM databases, five umami peptides (EELK, EEEIK, EELMK, LEEEIK, DELDKYS) with high umami scores were synthesized. Sensory evaluation revealed that these umami peptides exhibited a threshold ranging from 0.12 mg mL-1 to 0.36 mg mL-1. Circular dichroism (CD) analysis indicated the presence of β-sheet structures in the umami peptides that could be associated with taste formation. In addition, molecular docking and molecular dynamics (MD) were employed to investigate the binding mechanisms between umami peptides and the umami receptor T1R1/T1R3. The findings reveal that Lys155, Arg255, and Gln250 of T1R1/T1R3 potentially play critical roles in umami peptide binding. Taken together, our results lay a foundation for researching flavor substances and for developing flavor products from Yanjin black bone chicken.

Enzymatic synthesis of N-succinyl-L-phenylalanine and exploration of its potential as a novel taste enhancer

N-succinyl-L-phenylalanine (SP) has been identified as a taste-active contributor in an array of foods. Despite its recognized importance, the understanding of its synthesis and taste enhancement properties remains rudimentary. The study examined the enzymatic synthesis of SP with 45.58 ± 1.95% yield. This was achieved under optimized conditions: 0.3 mol/L L-phenylalanine, 0.9 mol/L succinic acid, 30,000 U/L of the AY 50C, pH 4 and 55 °C for 24 h. Sensory evaluation and electronic tongue revealed that the incorporation of a mere 1 mg/L SP substantially increased the kokumi, umami, and saltiness intensities, indicating the potential of SP as a potent taste enhancer. Moreover, time-intensity (TI) results demonstrated a significant increase of umami duration in samples containing 1 mg/L of SP (210.0 ± 0 s), a significant extension compared to the control group (150.0 ± 0 s). Notably, the intensity of umami and saltiness in the SP sample were consistently higher than that of control group. The sigmoid curve analysis further confirmed that SP exhibited a synergistic effect on umami and saltiness perceptions. Moreover, the study also illuminated interaction of SP with T1R1, T1R3, TMC4, TRPV1, and CaSR receptors, resulting in significant enhancement in umami, saltiness, and kokumi.

Based on green synthesis, multisensory evaluations and molecular simulation approaches: Exploring the taste-enhancing characteristics and mechanisms of N-succinyl-L-leucine

N-Succinyl amino acids (N-Suc-AAs) are increasingly recognized for their potential as taste-active compounds. However, research into the green synthesis, taste-enhancing properties, and mechanisms of N-succinyl-L-leucine (N-Suc-Leu) remains limited. This study employed an enzymatic synthesis method, catalyzed by protamex and pancreatin, to produce N-Suc-Leu, with its structure confirmed. Multiple sensory techniques demonstrated that N-Suc-Leu markedly enhanced the umami, saltiness, and kokumi intensity, and prolonged the duration of umami by 25%. Sigmoid curve analysis further revealed the synergistic enhancement of N-Suc-Leu on the perceptions of umami and saltiness. Molecular docking and dynamics simulations revealed that N-Suc-Leu could bind with T1R1, T1R3, TMC4, and CaSR, enhancing the sensations of saltiness, umami, and kokumi, and bound closely to these receptors without altering their overall conformation. These findings offered a systematic explanation of the potential and mechanism of enzymatically synthesized N-Suc-Leu in enhancing taste and provided novel insights into potential strategies for the development and innovation of taste enhancers and food flavors.

Exploration of Bioactive Umami Peptides from Wheat Gluten: Umami Mechanism, Antioxidant Activity, and Potential Disease Target Sites

Umami peptides have the ability to enhance food flavours and have potential health benefits. The objective of this study was to conduct a comprehensive investigation into the umami intensity, taste mechanism, and antioxidant activity of six umami peptides derived from wheat gluten hydrolysates (WGHs) and fermented WGHs. The e-tongue analysis demonstrated that the peptides exhibited a direct proportionality in terms of umami value and concentration, and were capable of enhancing the umami of commercially available condiments. The molecular dynamics simulations demonstrated that the peptides interacted with T1R1/T1R3 receptors via hydrogen bonds, hydrophobic interactions, ionic interactions, and water bridges, thereby producing umami. Furthermore, the DPPH, ABTS, hydroxyl radical-scavenging, and FRAP assays demonstrated that the six peptides exhibited antioxidant activity in vitro. Ultimately, the network pharmacology and molecular docking results indicated that AKT1, JUN, and CASP3 may serve as the core targets for the peptides in the treatment of oxidative diseases. In conclusion, this work offers novel insights into the use of bioactive umami peptides, emphasising their prospective applications in the food and health supplement industries.

A review of taste-active compounds in meat: Identification, influencing factors, and taste transduction mechanism

Poultry and livestock meat are important parts of the human diet. As living standards have improved, food taste has become a major influence on consumer quality assessment and meat purchasing choices. There is increasing research interest in meat taste and meat taste-active compounds, which include free amino acids, flavor nucleotides, taste-active peptides, organic acids, soluble sugars, and inorganic ions. Taste component research is also an important part of sensory science. A deeper understanding of the meat taste perception mechanism and interactions among different taste compounds will promote the development of meat science and sensory evaluation. This article reviews the main taste compounds in meat, factors influencing their concentrations, and the identification and measurement of taste-active compounds, as well as summarizing the mechanisms of taste sensing and perception. Finally, the future of scientific taste component evaluation is discussed. This review provides a theoretical basis for research on meat taste and an important reference for the development of the meat industry.

Enzymatic synthesis and sensory evaluation of the novel kokumi compound N-butyryl phenylalanine

In this study, food-grade glutamine transaminase (TGase) was utilized for the green-catalyzed preparation of N-butyryl amino acids. For improving the reusability of the enzyme preparation, immobilized TG enzyme (94.23% immobilization rate) was prepared. Furthermore, the yield of N-butyryl phenylalanine (BP) synthesized by TGase was obtained as 20.73% by one-factor experiment. The BP synthesis yield of immobilized TGase was 95.03% of that of TGase and remained above 60% of the initial enzyme activity after five runs. The sensory evaluation and E-tongue results showed that the addition of BP significantly increased the umami, saltiness, and richness intensities of the samples, and decreased the intensities of sourness, bitterness, and aftertaste-B. The molecular docking results indicated that hydrogen bonding dominated the binding of BP to taste receptors in the taste presentation mechanism of BP. These results confirmed the potential of BP as a flavor enhancer with promising applications in the food industry.

Identification and screening of umami peptides from skipjack tuna (Katsuwonus pelamis) hydrolysates using EAD/CID based micro-UPLC-QTOF-MS and the molecular interaction with T1R1/T1R3 taste receptor

In this study, the enzymatic hydrolysates of skipjack tuna, Katsuwonus pelamis, were purified by ultrafiltration and further identified through micro-ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (micro-UPLC-QTOF-MS). The potential umami peptides were identified using both conventional collision-induced dissociation (CID) and novel electron-activated dissociation (EAD) fragmentation techniques. Nine novel umami peptides with iUmami-SCM > 588 were screened. Sensory evaluation and electronic tongue analysis were performed to confirm the taste characteristics of the umami peptides, indicating that these umami peptides all exhibited varying degrees of umami taste. Molecular docking and molecular dynamics simulation were utilized to investigate the interaction with T1R1/T1R3 taste receptors. The docking results revealed that Asp234, Ser23, Glu231, and Ile237 appeared most frequently in all docking sites and formed stable complexes through hydrogen bonding and electrostatic interactions. Furthermore, molecular dynamics simulation allowed for a more comprehensive analysis of their interactions within a dynamic environment, providing a deeper understanding of the umami perception mechanism involving umami peptides and receptors.

Molecular simulation screening and sensory evaluation unearth a novel kokumi compound with bitter-masking effect: N-lauroyl-L-tryptophan

N-lauroyl-L-tryptophan (LT), which has the strongest potential flavor-presenting activity, was skillfully screened from numerous N-Lau-AAs docked to different taste receptors by molecular simulation techniques. Subsequently, LT was synthesized employing food-grade commercial enzymes and structurally characterized, the optimized yields of LT could reach 69.08%, 76.16%, and 50.40%, respectively. Sensory and E-tongue evaluations showed that LT at 1 mg/L significantly benefited the performance of different taste sensations and exhibited different bitter taste masking effects: L-Ile (68.42%), L-Trp (68.18%), D-salicylic acid (48.48%) and quinine (35.00%). The molecular docking results illustrated that LT had a high affinity for various taste receptors, dominated by hydrogen bonding and hydrophobic interactions. This work provided a rare systematic elucidation of the potential and mechanism of enzymatically synthesized LT in enhancing taste properties. It provides novel insights into the directions and strategies for the excavation and innovation of flavor enhancers and food flavors.

High-throughput discovery of umami peptides from pork bone and elucidation of their molecular mechanism for umami taste perception

This study endeavored to high-throughput identify umami peptides from pork bone. Pork bone protein extracts were hydrolyzed using proteinase K and papain, enzymes selected through computational proteolysis of pork type I collagen under the controlled conditions predicted by umami intensity-guided response surface analysis. Peptide sequences (GVNAMLRK, HWDRSNWF, PGRGCPGN, NLRDNYRF, PGWETYRK, GPGCKAGL, VAQWRKCL, GPTAANRM) in hydrolysates were virtually screened as potential umami peptides. Sensory evaluation confirmed that six of these peptides demonstrate a progressive increase in umami intensity. Molecular docking revealed that hydrophilic amino acids in umami peptides predominantly formed hydrogen bonds with T1R1/T1R3. Specifically, residues Thr, Asn, Lys, Ser and Glu of peptides mainly interacted with Ser107/148/276 of T1R1, and residues Tyr, Arg and Asp played crucial roles in binding to the Ser104/146 and His145 of T1R3. This study offers insights into the high-value utilization of pork bones and guides the development of umami peptides in various food proteins.

Identification of Novel Umami Peptides from Yeast Protein through Enzymatic, Sensory, and In Silico Approaches

This study aimed to rapidly develop novel umami peptides using yeast protein as an alternative protein source. Yeast protein hydrolysates exhibiting pronounced umami intensity were produced using flavorzyme under optimum conditions determined via a sensory-guided response surface methodology. Six out of 2138 peptides predicted to possess umami taste by composite machine learning and assessed as nontoxic, nonallergenic, water-soluble, and stable using integrated bioinformatics were screened as potential umami peptides. Sensory evaluation results revealed these peptides exhibited multiple taste attributes (detection threshold: 0.37 ± 0.10-1.1 ± 0.30 mmol/L), including umami. In light of the molecular docking outcomes, it is inferred that hydrogen bond, hydrophobic, and electrostatic interactions enhanced the theoretically stable binding of peptides to T1R1/T1R3, with their contributions gradually diminishing. Hydrophilic amino acids within T1R1/T1R3, especially Ser, may play a particularly pivotal role in binding with umami peptides. Future research will involve establishing heterologous cell models expressing T1R1 and T1R3 to delve into the cellular physiology of umami peptides. Peptide sequences (FADL, LPDP, and LDIGGDF) also had synergistic saltiness-enhancing effects; to overcome the limitation of not investigating the saltiness enhancement mechanism, comprehensive experiments at the molecular and cellular levels will also be conducted. This study offers a rapid umami peptide development framework and lays the groundwork for exploring yeast protein taste compounds.

Insight into the correlation of key taste substances and key volatile substances from shrimp heads at different temperatures

This study aimed to investigate taste substances of shrimp heads stored at 20 °C, 4 °C, -3 °C, and - 18 °C, and the correlation between taste substances and 25 key volatile substances. Notably, samples stored at 20 °C showed significant changes in bitter amino acids and hypoxanthine, and quickly deteriorated. Samples stored at 4 °C for 14 d or - 3 °C for 30 d facilitated the development of umami amino acids, sweet amino acids, and IMP. Furthermore, samples stored at -18 °C for 30 d demonstrated no significant changes in taste profile. Changes in taste substances through quantitative analysis were consistent with changes in taste profile through e-tongue analysis. Based on the results of O2PLS (VIP > 1), Cys, Arg, Glu, Ser, Val, Ala, Ile, ADP, and IMP were correlated with 25 key volatile substances. This study provides fundamental data for the storage, transportation, and value-added utilization of shrimp heads.

Decoding of Salty/Saltiness-Enhancing Peptides Derived from Goose Hemoglobin and the Interaction Mechanism with TMC4 Receptor

Amid the growing concern for health-oriented food choices, salt reduction has received widespread attention, particularly in the exploitation of salt alternatives. Peptides with a saltiness-enhancing effect may provide an alternative method for salt reduction. The objective of this study was to isolate and extract novel peptides with salt-reducing effects by fermenting goose blood using a Lactobacillus plantarum strain. Five potential target peptides were screened by a virtual database prediction and molecular docking. Sensory evaluation and E-tongue analysis showed that five peptides (NEALQRM, GDAVKNLD, HAYNLRVD, PEMHAAFDK, and AEEKQLITGL) were identified as target peptides. Particularly, the results of E-tongue showed that GDAVKNLD can increase the saltiness intensity (2.87 ± 0.02) in the complex system. The sensory evaluation results also indicated an increase in saltiness intensity (46.67 ± 4.67 mmol/L NaCl) after adding GDAVKNLD. The results of molecular dynamics simulation indicated that five peptides have good ability to bind tightly to TMC4 receptor, thereby stimulating it to exert an active effect. And these peptides interacted with the TMC4 receptor via hydrogen bonding, hydrophobic interactions, and electrostatic interactions. This research lays a theoretical foundation for discovering novel salty/saltiness-enhancing peptides and provides meaningful contributions to efforts in salt reduction.

A Novel Compound with Kokumi Properties: Enzymatic Preparation and Taste Presentation Evaluation of N-Lauroyl Phenylalanine

To satisfy the demands of the food industry, innovative flavor enhancers need to be developed urgently to increase the food flavor. In our work, N-lauroyl phenylalanine (LP) was prepared from phenylalanine (l-Phe) and lauric acid (Lau) in water through the use of commercial enzymes (Promatex, Sumizyme FP-G, and Trypsin), and its flavor-presenting properties and mechanism were investigated. The highest LP yields obtained under one-factor optimized conditions were 61.28, 63.43, and 77.58%, respectively. Sensory assessment and an e-tongue test revealed that 1 mg/L LP enhanced the kokumi, saltiness, and umami of the simulated chicken broth solution and attenuated the bitterness of the l-isoleucine solution. The molecular simulation results suggested that the mechanisms of LP enhancement of kokumi and umami were related to hCaSR and hT1R1-hT1R3, and that hydrophobic forces and hydrogen bonds were involved in the binding of LP to taste receptors. The results implied that LP is a potential flavor enhancer for food applications.

Characteristics of saltiness-enhancing peptides derived from yeast proteins and elucidation of their mechanism of action by molecular docking

This study aimed to identify saltiness-enhancing peptides from yeast protein and elucidate their mechanisms by molecular docking. Yeast protein hydrolysates with optimal saltiness-enhancing effects were prepared under conditions determined using an orthogonal test. Ten saltiness-enhancing peptide candidates were screened using an integrated virtual screening strategy. Sensory evaluation demonstrated that these peptides exhibited diverse taste characteristics (detection thresholds: 0.13-0.50 mmol/L). Peptides NKF, LGLR, WDL, NMKF, FDSL and FDGK synergistically or additively enhanced the saltiness of a 0.30% NaCl solution. Molecular docking revealed that these peptides predominantly interacted with TMC4 by hydrogen bonding, with hydrophilic amino acids from both peptides and TMC4 playing a pivotal role in their binding. Furthermore, Leu217, Gln377, Glu378, Pro474 and Cys475 were postulated as the key binding sites of TMC4. These findings establish a robust theoretical foundation for salt reduction strategies in food and provide novel insights into the potential applications of yeast proteins.

Investigation of umami peptides and taste mechanisms in Agrocybe aegerita: based on sensory evaluation and molecular docking techniques

In the present study, sensory orientation and instrumental analysis were employed to separate, purify, and identify umami peptides in Agrocybe aegerita hydrolysate. Using UPLC-ESI-Q-TOF MS, 11 potential umami peptides (EY, EG, EV, ENG, PEG, DEL, ECG, DDL, PEEL, EDCS and DGPL) were identified from the screened fractions. Moreover, sensory evaluation and E-tongue results showed that the identified umami peptides had umami attributes, within an umami threshold range of 0.0625-0.25 mg mL-1. In addition, DDL and DEL exhibited the highest umami flavor intensity. Molecular docking analysis further showed that 4 umami peptides (namely, EY, EG, ECG, and DGPL) entered the T1R1 cavity of the umami receptor. Additionally, 4 umami peptides (namely, EV, ENG, DEL, and EDCS) could be embedded in the binding pocket of the T1R3 cavity. Furthermore, 3 umami peptides (PEG, DDL, and PEEL) strongly interacted with T1R1/T1R3. Thus, the findings collectively indicated that the predominant interacting forces between umami peptide and umami receptor are hydrogen bonding and hydrophobic interactions. Finally, it was shown that the primary binding sites of T1R1 were residues Ser109, Gln52 and Ser148, while the primary binding sites of T1R3 were residues Ser172, Arg277 and Ala170. The study identified the umami peptides in A. aegerita for the first time, which provided more information for the umami research of A. aegerita and provided the theoretical basis for the further development and utilization of A. aegerita.

Study on the saltiness-enhancing mechanism of chicken-derived umami peptides by sensory evaluation and molecular docking to transmembrane channel-like protein 4 (TMC4)

The previously obtained chicken-derived umami peptides in the laboratory were evaluated for their saltiness-enhancing effect by sensory evaluation and S-curve, and the results revealed that peptides TPPKID, PKESEKPN, TEDWGR, LPLQDAH, NEFGYSNR, and LPLQD had significant saltiness-enhancing effects. In the binary solution system with salt, the ratio of the experimental detection threshold (129.17 mg/L) to the theoretical detection threshold (274.43 mg/L) of NEFGYSNR was 0.47, which had a synergistic saltiness-enhancing effect with salt. The model of transmembrane channel-like protein 4 (TMC4) channel protein was constructed by homology modeling, which had a 10-fold transmembrane structure and was well evaluated. Molecular docking and frontier molecular orbitals showed that the main active sites of TMC4 were Lys 471, Met 379, Cys 475, Gln 377, and Pro 380, and the main active sites of NEFGYSNR were Tyr, Ser and Asn. This study may provide a theoretical reference for low-sodium diets.

Taste Mechanism of Umami Molecules from Fermented Broad Bean Paste Based on In Silico Analysis and Peptidomics

In this study, in silico analysis and peptidomics were performed to examine the generation mechanism of the umami taste of fermented broad bean paste (FBBP). Based on the information from peptidomics, a total of 470 free peptides were identified from FBBP, most of which were increased after fermentation. Additionally, the increase of the content of umami peptides, organic acids, and amino acids during fermentation contributed to the perception of umami taste in FBBP. Molecule docking results inferred that these umami molecules were easy to connect with Ser, Glu, His, and Gln in the T1R3 subunit through hydrogen bonds and electrostatic interaction force. The binding sites His145, Gln389, and Glu301 particularly contributed to the formation of the ligand-receptor complexes. The aromatic interaction, hydrogen bond, hydrophilicity, and solvent-accessible surface (SAS) played key roles in the receptor-peptide interaction. Sensory evaluation and electronic tongue results showed that EDEDE, DLSESV, SNGDDE, DETL, CDLSD, and TDEE screened from FBBP had umami characteristics and umami-enhancing effects (umami threshold values ranging from 0.131 to 0.394 mmol/L). This work provides new insight into the rapid and efficient screening of novel umami peptides and a deeper understanding of the taste mechanisms of umami molecules from FBBP.

Electronic tongue, proton-transfer-reaction mass spectrometry, spectral analysis, and molecular docking characterization for determining the effect of α-amylase on flavor perception

The effects of α-amylase on of flavor perception were investigated via spectrum analysis, electronic tongue, on-line mass spectrometry, and molecular docking. Aroma release results showed that α-amylase exhibited variable release patterns of different aroma compounds. Electronic tongue analysis showed that the perception of bitterness, sweetness, sour, and saltiness was subtly increased and that of umami was significantly increased (p < 0.01) along with the increasing enzyme activity of α-amylase. Ultraviolet absorption and fluorescence spectroscopy analyses showed that static quenching occurred between α-amylase and eight flavor compounds and their interaction effects were spontaneous. One binding pocket was confirmed between the α-amylase and flavor compounds, and molecular docking simulation results showed that the hydrogen, electrostatic, and hydrophobic bonds were the main force interactions. The TYP82, TRP83, LEU173, HIS80, HIS122, ASP297, ASP206, and ARG344 were the key α-amylase amino acid residues that interacted with the eight flavor compounds.

From Molecular Dynamics to Taste Sensory Perception: A Comprehensive Study on the Interaction of Umami Peptides with the T1R1/T1R3-VFT Receptor

The research on the umami receptor-ligand interaction is crucial for understanding umami perception. This study integrated molecular simulations, sensory evaluation, and biosensor technology to analyze the interaction between umami peptides and the umami receptor T1R1/T1R3-VFT. Molecular dynamics simulations were used to investigate the dissociation process of seven umami peptides with the umami receptor T1R1/T1R3-VFT, and by calculating the potential mean force curve using the Jarzynski equation, it was found that the binding free energy of umami peptide is between -58.80 and -12.17 kcal/mol, which had a strong correlation with the umami intensity obtained by time intensity sensory evaluation. Through correlation analysis, the dissociation rate constants (0.0126-0.394 1/s) of umami peptides were found to have a great impact on umami perception. The faster the dissociation rate of umami peptides from receptors, the stronger the perceived intensity of the umami taste. This research aims to elucidate the relationship between the umami peptide-receptor interaction and umami perception, providing theoretical support for the exploration of umami perception mechanisms.

Identification, screening and taste mechanisms analysis of two novel umami pentapeptides derived from the myosin heavy chain of Atlantic cod (Gadus morhua)

Umami peptides are new ingredients for the condiment and seasoning industries, with healthy and nutrition characteristics, some of which were identified from aquatic proteins. This study aims to further explore novel umami peptides from Atlantic cod (Gadus morhua) by combining in silico, nano-HPLC-MS/MS, sensory evaluation, and electronic tongue analysis. Two novel peptides, Leu-Val-Asp-Lys-Leu (LVDKL) and Glu-Ser-Lys-Ile-Leu (ESKIL), from the myosin heavy chain of Atlantic cod (Gadus morhua), were screened and confirmed to have strong umami tastes with the thresholds of 0.427 mM and 0.574 mM, respectively. The molecular docking was adopted to explore the interactions between the umami peptides and the umami taste receptor T1R1/T1R3, which showed that the umami peptides interacted with T1R1/T1R3 mainly by electrostatic interaction, hydrogen bond interaction, and hydrophobic interaction. Furthermore, the physicochemical properties of the peptides were investigated by in silico methods and cell viability experiments. This study will provide a better understanding of the umami taste in Atlantic cod and will promote the development of condiments and seasonings.

Flavor Characteristics of Umami Peptides from Wuding Chicken Revealed by Molecular Dynamics Simulation

Wuding chicken is famous for its delicious meat, and HLEEEIK, LDDALR, and ELY were jointly extracted from different processing stages of Wuding chicken. However, whether these peptides can be used as umami supplements is unclear. The sensory evaluation tests were used to study the taste characteristics. The secondary structure of the peptides and their interaction with T1R1/T1R3 were predicted by the circular dichroism spectrum and molecular dynamics simulation. The umami threshold was 0.03125 to 0.06250 mg/mL, all of which could increase umami, saltiness, sweetness, and mask bitterness. Compared with HLEEEIK, the frequency of umami active fragments and the improvement rate of the umami score of EEE increased by 133.35% and 40.09%, respectively. Peptides were dominated by umami taste according to sensory analysis, among which EE-3 (3.18) has the highest umami intensity followed by LR-4 (2.58), HK-7 (2.13), and EY-3 (1.82). The main secondary structure of umami peptides was β-folding, and Tyr74, Arg323, Arg272, and Gln35 were the key amino acid residues for binding of umami peptides to the receptor. This study further elucidated that the umami intensity of the peptides could be altered by changing the sequence composition of the peptides, which enhanced our understanding of the complex flavor properties of umami peptides.

Virtual screening and characteristics of novel umami peptides from porcine type I collagen

This study aimed to rapidly and precisely discover novel umami peptides from porcine type I collagen using virtual screening, sensory evaluation and molecular docking simulation. Porcine type I collagen was hydrolyzed in silico and six umami peptide candidates (CN, SM, CRD, GESMTDGF, MS, DGC) were shortlisted via umami taste, bioactivity, toxicity, allergenicity, solubility and stability predictions. The sensory evaluation confirmed that these peptides exhibited umami taste, with CRD, GESMTDGF and DGC displaying higher umami intensity and significant umami-enhancing effects in 0.35% sodium glutamate solution. Molecular docking predicted that Ser 276/384/385 of T1R1 and Asn68, Val277, Thr305, Ser306, Leu385 of T1R3 may also play critical roles in binding umami peptides. The umami taste of peptides may be perceived mainly through the formation of hydrogen bonds with the hydrophilic amino acids of T1R1/T1R3. This work provided a robust procedure and guidance to develop novel umami peptides from food byproducts.

Noteworthy Consensus Effects of D/E Residues in Umami Peptides Used for Designing the Novel Umami Peptides

Aspartic acid (D) and glutamic acid (E) play vital roles in the umami peptides. To understand their exact mechanism of action, umami peptides were collected and cut into 1/2/3/4 fragments. Connecting D/E to the N/C-termini of the fragments formed D/E consensus effect groups (DEEGs), and all fragments containing DEEG were summarized according to the ratio and ranking obtained in the above four situations. The interaction patterns between peptides in DEEG and T1R1/T1R3-VFD were compared by statistical analysis and molecular docking, and the most conservative contacts were found to be HdB_277_ARG and HdB_148_SER. The molecular docking score of the effector peptides significantly dropped compared to that of their original peptides (-1.076 ± 0.658 kcal/mol, p value < 0.05). Six types of consensus fingerprints were set according to the Top7 contacts. The exponential of relative umami was linearly correlated with ΔGbind (R2 = 0.961). Under the D/E consensus effect, the electrostatic effect of the umami peptide was improved, and the energy gap between the highest occupied molecular orbital-the least unoccupied molecular orbital (HOMO-LUMO) was decreased. The shortest path map showed that the peptides had similar T1R1-T1R3 recognition pathways. This study helps to reveal umami perception rules and provides support for the efficient screening of umami peptides based on the material richness in D/E sequences.

Characterization and sweetness-enhancing effect of peptides from yeast extract based on sensory evaluation and molecular docking approaches

Yeast extract (YE) is derived from the soluble component in yeast cells, which is rich in peptides and has been used as a sweet-enhancing agent. It has the potential to be utilized to produce natural sweet-flavored peptides or sweet-enhancing peptides. To study the synergistic effect and mechanism of sweetness-enhancing peptides derived from YE, ultrafiltration fraction with molecular weight less than 1 kDa was screened according to sensory analysis, which showed a synergistic sweetening effect in stevioside and mogroside solution. Twenty potential taste peptides were identified from the screened fractions, among which EV, AM, AVDNIPVGPN and VDNIPVGPN showed sweetness-enhancing effects on both stevioside and mogroside. The sweetener-receptor-peptide complex was constructed to investigate the interaction of stevioside and mogroside to taste receptor type 1 member 2 accompanied by these peptides. The results of the molecular docking indicated that new hydrophobic interactions (Leu 279, Pro 308, Val 309, etc.) and hydrogen bonds (Ser 40, Ala 43, Asp 278, etc.) were formed between sweeteners and active sites in the venus flytrap domain. In conclusion, the presence of sweetness-enhancing peptides from YE improved the binding stability of sweeteners and receptors by increasing the binding interaction, especially the hydrophobic interactions, which contribute to the synergistic effect of sweetness-enhancing peptides.

Odorants Identified in Chinese Dry-Cured Ham Contribute to Salty Taste Enhancement

Jinhua dry-cured ham (JDH) is a traditional fermented Chinese meat product. We studied the dynamic sensory and emotional profiles of JDHs obtained by five preparation methods and the corresponding release of sodium ions (Na+), potassium ions (K+), and volatile organic compounds (VOCs) during oral processing. The VOCs with salty taste enhancement abilities were screened based on the correlations of VOCs with salty flavor and concentration of Na and K ions with salty flavor. A trained sensory panel evaluated the saltiness enhancements of selected VOCs by using static and dynamic sensory methods. The results revealed that Na+, K+, and selected VOCs were mainly released during 0-10 s of the chewing process. The release of Na+ and K+ in JDH residue samples exhibited consistently decreasing trends, while in saliva, their concentrations increased. The VOCs showing a high correlation with Na+ and K+ and salty flavor have saltiness enhancement abilities in both NaCl solutions and NaCl + MSG mixtures. Odor-induced saltiness was pronounced at low salt concentrations (0.2% NaCl). The investigation demonstrated 16 VOCs exhibiting saltiness enhancement abilities, including 4 pyrazines, 5 acids, 4 sulfur-containing compounds, and 3 other compounds. The sensory evaluation suggested pyrazines and sulfur-containing compounds as good saltiness enhancers. 2-Furfuryl mercaptan significantly enhanced the salty sensation in the NaCl + MSG solutions when compared with MSG alone (p < 0.05). This research provides evidence that certain odorants identified in JDHs exhibit salty-enhancing properties, indicating their potential for salt reduction at the industrial level.

Peptidomics Screening and Molecular Docking with Umami Receptors T1R1/T1R3 of Novel Umami Peptides from Oyster (Crassostrea gigas) Hydrolysates

In this study, novel umami peptides were prepared from oyster (Crassostrea gigas) hydrolysates, and their umami mechanisms were investigated. Umami fractions G2 and G3 were isolated by gel filtration chromatography (GFC) and sensory evaluation. The umami scores of the G2 and G3 fractions were 7.8 ± 0.12 and 7.5 ± 0.18, respectively. 36 potential umami peptides with molecular weights below 1500 Da, E and D accounting for >30% of the peptides and iUmami-SCM > 588 were screened by peptidomics. Peptide source analysis revealed that myosin, paramyosin, and sarcoplasmic were the major precursor proteins for these peptides. The electronic tongue results demonstrated that the synthetic peptides DPNDPDMKY and NARIEELEEE possessed an umami characteristic, whereas SIEDVEESRNK and ISIEDVEESRNK possessed a saltiness characteristic. Additionally, molecular docking results indicated that the umami peptide (DPNDPDMKY, NARIEELEEE, SIEDVEESRNK, and ISIEDVEESRNK) binds to H145, S276, H388, T305, Y218, D216, and Q389 residues in the T1R3 taste receptor via a conventional hydrogen bond and a carbon-hydrogen bond. This research provides a new strategy for the screening of umami peptides.

Synthesis of taste active γ-glutamyl peptides with pea protein hydrolysate and their taste mechanism via in silico study

Pea (Pisum sativum L.) protein hydrolysate (PPH) has a bitter taste, which has limited its use in food industry. γ-Glutamylation is used to debitter PPH. Results showed that the bitterness of PPH was decreased significantly due to the formation of γ-glutamyl peptides, including 16 γ-[Glu](n=1/2)-amino acids (AAs) and 8 newly discovered γ-glutamyl tripeptides (γ-Glu-Asn-Phe, γ-Glu-Leu-Val, γ-Glu-Leu-Tyr, γ-Glu-Gly-Leu, γ-Glu-Gly-Phe, γ-Glu-Gly-Tyr, γ-Glu-Val-Val, and γ-Glu-Gln-Tyr). Their total production concentrations were 27.25 μmol/L and 77.76 μmol/L, respectively. The γ-Glu-AA-AAs presented an umami-enhancing, salty-enhancing, and kokumi taste when their concentration reached 1.67 ± 0.20 ∼ 2.07 ± 0.20, 1.65 ± 0.25 ∼ 2.29 ± 0.45 and 0.68 ± 0.19 ∼ 1.03 ± 0.22 mmol/L, respectively. The γ-Glu-AA-AAs exhibited a kokumi taste by entering the Venus flytrap (VFT) of the calcium-sensing receptor and interacting with Ser147, Ala168, and Ser170. γ-Glu-AA-AAs can enhance the umaminess of Monosodium Glutamate (MSG) as they can enter the binding pocket of the taste receptor type 1 subunit 3 (T1R3)-MSG complex.

Dynamic changes in the water and volatile compounds of chicken breast during the frying process

The influence of frying times (0, 2, 4, 6, 8, and 10 min) on the continuous changes in the water distribution and the concentrations of key volatile compounds in chicken breast during the frying process were studied. The fried chicken samples could be distinguished by PCA of E-nose and PLS-DA of GC-MS. A total of 40 volatile compounds were identified by GC-MS, and 28 compounds were verified to be the key compounds after further screening by OAVs. The T22 was increased first and then decreased, while the M22 and M23 in fried chicken were considerably decreased and increased with increasing frying time, respectively. The content of the water and the total peak area of LF-NMR in fried chicken samples during the frying process significantly decreased, and the water was transferred from high to low degrees of freedom. In addition, water content, T21, T22, M22 and L* value were positively correlated with most alcohols and aldehydes, and were negatively correlated with pyrazines, while a*, b*, M23 and all amino acids were positively correlated with pyrazines and were negatively correlated with most alcohols and aldehydes. The results may guide the production processes of fried chicken and help produce high-quality chicken products.

Impact of ternary NADES prepared from proline, glucose and water on the Maillard reaction: Reaction activity, Amadori compound yield, and taste-enhancing ability

This study employed proline, glucose, and water to prepare natural deep eutectic solvents (NADES) through heating and stirring. The Maillard reaction was then performed, producing a high yield of Amadori rearrangement product (ARP) and physicochemical properties of NADES were examined for impacts on the reaction. Water had a dual function by promoting the formation of hydrogen bonding networks within the NADES when present at less than 15%, and also working as a diluting agent that could potentially disturb its structure when exceed 15%. These changes further affected the subsequent Maillard reaction, especially the ARP accumulation (reached the highest when water content was 15%). Correlation analysis shows strong positive viscosity-ARP and negative water activity-ARP correlations within a range. Moreover, the product (rich in ARP) remarkably enhanced umami and saltiness. This finding provides insights into modulating the Maillard reaction by adjusting NADES properties, demonstrating feasibility of this approach for flavor enhancer development.

Nutritional Values and Bio-Functional Properties of Fungal Proteins: Applications in Foods as a Sustainable Source

From the preparation of bread, cheese, beer, and condiments to vegetarian meat products, fungi play a leading role in the food fermentation industry. With the shortage of global protein resources and the decrease in cultivated land, fungal protein has received much attention for its sustainability. Fungi are high in protein, rich in amino acids, low in fat, and almost cholesterol-free. These properties mean they could be used as a promising supplement for animal and plant proteins. The selection of strains and the fermentation process dominate the flavor and quality of fungal-protein-based products. In terms of function, fungal proteins exhibit better digestive properties, can regulate blood lipid and cholesterol levels, improve immunity, and promote gut health. However, consumer acceptance of fungal proteins is low due to their flavor and safety. Thus, this review puts forward prospects in terms of these issues.

Identification of Novel Umami Peptides in Termitornyces albuminosus (Berk) Heim Soup by In Silico Analyses Combined with Sensory Evaluation: Discovering Potential Mechanism of Umami Taste Formation with Molecular Perspective

In this study, 24 peptides were identified in Termitornyces albuminosus (Berk) Heim soup, 12 of which were predicted to possess an umami taste based on the BIOPEP-UWM or Umami-MRNN databases. Among these 12 peptides, four peptides (i.e., QNDF, QGGDF, EPVTLT, and EVNYDFGGK) exhibited the lowest affinity energy with the umami receptor type 1 member 1 (T1R1) subunit. Molecular docking and molecular dynamics simulation further confirmed the strong binding of these four umami peptides to the umami receptor T1R1/T1R3, with the EVNYDFGGK forming the most stable complex. After synthesizing the four peptides, their umami taste was validated through sensory and electronic tongue analyses with recognition thresholds ranging from 0.0938 to 0.3750 mmol/L. Notably, the EVNYDFGGK peptide displayed the strongest umami taste (recognition threshold, 0.0938 mmol/L). This study may contribute to the industrial development of T. albuminosus by providing a new understanding of the mechanism of its umami formation.

Comparison of the taste mechanisms of umami and bitter peptides from fermented mandarin fish (Chouguiyu) based on molecular docking and electronic tongue technology

Unclear taste mechanisms of peptides limit rapid screening of taste peptides with high intensity. In this study, the taste mechanisms of umami and bitter peptides from Chouguiyu were compared. After molecular docking of core umami (NWDDMEK, WFKDEEF, EEEKPKF, DFDDIQK, and DGEKVDF) and bitter (VQDVLKL, VELLKLE, LVVDGVK, VVDLTVR, and VVDGVKL) peptides with T1R1/T1R3 and TASR14, respectively, salt bridges and conventional hydrogen bonds were the main interactions in all taste peptides, in which acidic amino acid residues contributed to the interaction with their receptors. The taste intensity of peptides after solid-phase synthesis was further verified using electronic tongue technology. Spearman correlation analysis showed that docking energy was an important factor for the intensity of taste peptides, while interaction energy and the distance between the binding unit (BU) and the stimulating unit (SU) were also responsible for the bitter intensity. This study provides a theoretical basis to screen novel taste peptides with high taste intensity in fermented foods.

Antihypertensive Effect, ACE Inhibitory Activity, and Stability of Umami Peptides from Yeast Extract

Bioactive peptides from foods have garnered considerable attention as viable supplements for hypertensive patients. Herein, the antihypertensive effect and mechanism of umami peptides from yeast extract were investigated based on the pharmacophore model, simulated digestion, spontaneously hypertensive rat (SHR) model, and molecular docking. Notably, umami peptide LLLLPKP exhibited favorable angiotensin I-converting enzyme (ACE) inhibitory activity (IC50 = 10.22 μM) in vitro and regulated blood pressure in the SHR model with excellent durability. Remarkably, LLLLPKP showed the highest Fitvalue (4.022) of the pharmacophore model, indicating its similar pharmacological effects as ACE inhibitors. During the simulated gastrointestinal digestion, the ACE inhibition rate of LLLLPKP was merely reduced by 5.89%, but it was enzymatically cleaved into 14 peptide segments. The C-terminal sequence comprising L (4), P (5), K (6), and P (7) exhibited robust stability and a notable presence within the peptide segments postdigestion. Meanwhile, according to molecular docking, these four residues within LLLLPKP were responsible for all interactions with key sites within active pockets S1 and S2 and the active pocket of Zn2+. In light of these findings, LLLLPKP is a highly promising antihypertensive peptide. Developing this umami peptide with antihypertensive effects holds substantial importance for the long-term treatment of hypertension.

Umami-BERT: An interpretable BERT-based model for umami peptides prediction

Umami peptides have received extensive attention due to their ability to enhance flavors and provide nutritional benefits. The increasing demand for novel umami peptides and the vast number of peptides present in food call for more efficient methods to screen umami peptides, and further exploration is necessary. Therefore, the purpose of this study is to develop deep learning (DL) model to realize rapid screening of umami peptides. The Umami-BERT model was devised utilizing a novel two-stage training strategy with Bidirectional Encoder Representations from Transformers (BERT) and the inception network. In the pre-training stage, attention mechanisms were implemented on a large amount of bioactive peptides sequences to acquire high-dimensional generalized features. In the re-training stage, umami peptide prediction was carried out on UMP789 dataset, which is developed through the latest research. The model achieved the performance with an accuracy (ACC) of 93.23% and MCC of 0.78 on the balanced dataset, as well as an ACC of 95.00% and MCC of 0.85 on the unbalanced dataset. The results demonstrated that Umami-BERT could predict umami peptides directly from their amino acid sequences and exceeded the performance of other models. Furthermore, Umami-BERT enabled the analysis of attention pattern learned by Umami-BERT model. The amino acids Alanine (A), Cysteine (C), Aspartate (D), and Glutamicacid (E) were found to be the most significant contributors to umami peptides. Additionally, the patterns of summarized umami peptides involving A, C, D, and E were analyzed based on the learned attention weights. Consequently, Umami-BERT exhibited great potential in the large-scale screening of candidate peptides and offers novel insight for the further exploration of umami peptides.

Sensory-Guided Isolation, Identification, and Active Site Calculation of Novel Umami Peptides from Ethanol Precipitation Fractions of Fermented Grain Wine (Huangjiu)

Huangjiu is rich in low-molecular-weight peptides and has an umami taste. In order for its umami peptides to be discovered, huangjiu was subjected to ultrafiltration, ethanol precipitation, and macroporous resin purification processes. The target fractions were gathered according to sensory evaluation. Subsequently, we used peptidomics to identify the sum of 4158 peptides in most umami fractions. Finally, six novel umami peptides (DTYNPR, TYNPR, SYNPR, RFRQGD, NFHHGD, and FHHGD) and five umami-enhancing peptides (TYNPR, SYNPR, NFHHGD, FHHGD, and TVDGPSH) were filtered via virtual screening, molecular docking, and sensory verification. Moreover, the structure-activity relationship was discussed using computational approaches. Docking analysis showed that all umami peptides tend to bind with T1R1 through hydrogen bonds and hydrophobic forces, which involve key residues HIS71, ASP147, ARG151, TYR220, SER276, and ALA302. The active site calculation revealed that the positions of the key umami residues D and R in the terminal may cause taste differences in identified peptides.

Characterization of the Key Aroma Compounds in Different Yeast Proteins by GC-MS/O, Sensory Evaluation, and E-Nose

The unique odors of yeast proteins (YPs) are decisive for their application in meat substitutes. Sensory evaluation, electronic nose, and gas chromatography-mass spectrometry/olfactory (GC-MS/O) were combined to characterize the aroma profiles and aroma-active compounds of YPs. The sensory evaluation results indicate that the sweaty aroma had the strongest intensity in YP #10, followed by rice bran, sour, and plastic. The electronic nose could effectively distinguish the aroma differences among five YPs. A total of 27 aroma-active compounds in the five YPs were identified by GC-MS/O. The concentration of 2-methyl-propanoic acid (6.37 μg/kg), butanoic acid (47.46 μg/kg), 3-methyl-butanoic acid (22.50 μg/kg), and indole (943.40 μg/kg) in YP #10's aroma was higher than that of the other YPs. The partial least squares regression method results show that o-cresol, (3S)-3,7-dimethyloct-7-en-1-ol, benzyl alcohol, octanal, 2-methyl-propanoic acid, butanoic acid, 3-methyl-butanoic acid, hexanal, heptanal, and indole were predicted as the potential aroma-active compounds significantly contributing to the aroma profiles of the five YPs. Addition experiments confirmed that the overall aroma profile intensities of the five YP samples were extended with the addition of these ten compounds, verifying their significant contributions.

Pungency Perception and the Interaction with Basic Taste Sensations: An Overview

The perception of pungency can be attributed to the combination of pain and heat, and it has critical impacts on food flavor and food consumption preferences. Many studies have reported a variety of pungent ingredients with different Scoville heat units (SHU), and the mechanism of pungent perception was revealed in vivo and in vitro. The worldwide use of spices containing pungent ingredients has led to an increasing awareness of their effects on basic tastes. However, the interaction between basic tastes and pungency perception based on structure-activity relationship, taste perception mechanism and neurotransmission lacks review and summary, considering its brighter prospects in food flavor. Thus, in this review, common pungency substances and pungency evaluation methods, and the mechanism of pungency perception is presented, and the interaction between basic tastes and pungency perception and the possible factors of their interaction are reviewed in detail. Pungent stimuli are mainly transduced through transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential fixed hormone isoform (TRPA1) activated by stimulants. Using modern detection techniques combined with sensory standards, different substances produce different degrees of pungent stimulation, ranging from 10⁴ to 10⁷ SHU/g. Pungent stimuli can affect taste receptor or channel protein conformation and regulate taste bud cell sensitivity by producing neurotransmission products. The products of neurotransmission and taste receptor cell activation in turn act on taste perception. When there are simultaneous effects of taste perception, pungency stimulation may enhance the perception of salty at a certain concentration, with a mutual inhibition effect with sour, sweet, and bitter taste, while its interaction with umami taste is not obvious. However, due to the complexity of perception and the uncertainty of many perceptual receptors or channels, the current studies of interactions are still controversial. Based on the understanding of the mechanism and influencing factors, the availability of pungency substances is proposed in the perspective of food industry in order to achieve new development.