Identification of a novel umami peptide in tempeh (Indonesian fermented soybean) and its binding mechanism to the umami receptor T1R

Flavor effect, application status, and research trend of umami peptides based on microbial fermentation in food

Umami peptides are important non-volatile compounds produced by protein degradation, contributing to food umami flavor and enhancing product quality. Microbial fermentation promotes the production of taste peptides, including umami peptides, which act as key flavor substances and precursors. Microbial-derived umami peptides are cost-effective, easy to produce, and a major source of umami peptide production. Although microbial fermentation of umami peptides has been extensively studied in preparation, screening, and evaluation, a systematic review of microbial fermentation is still lacking. Therefore, this paper aims to address the following aspects: (1) umami peptide taste characteristics, influencing factors, and preparation methods; (2) microbial sources of umami peptides; (3) the current application status of microbial fermentation-derived umami peptides in various foods; and (4) future directions for microbial fermentation of umami peptides. Consequently, this literature review seeks to offer insights for advancing microbial fermentation in umami peptide production.

Identification and taste presentation characteristics of umami peptides from soybean paste based on peptidomics and virtual screening

This research concentrated on soybean paste fermented with Tetragenococcus halophilus, employing peptidomics and machine learning methodologies to screen for novel umami peptides. Taste characteristics of umami peptides were evaluated through sensory evaluation and electronic tongue analysis. The mechanism of taste presentation of the umami peptides was investigated through T1R1/T1R3 molecular docking techniques. Four peptides were identified: LLYGKVVKKT, DKKVSVGT, TRKQALLN, and QKNSHQ, with umami thresholds ranging from 0.02 to 0.14 mmol/L. Hydrogen bonds and electrostatic interactions are the key forces between umami peptides and receptors, and the length of hydrogen bonds is between 2.94 and 3.30 Å. Molecular docking analyses revealed that electrostatic and hydrogen bonding interactions are crucial, with ARG 248 and ALA 282 serving as key binding sites on T1R1 and T1R3 receptors, significantly influencing umami intensity. These findings aid in further understanding the flavor properties of umami peptides in soybean paste.

Studying the release of soybean taste-active peptides prepared by proteases derived from different fungi through Peptidomics

This study investigated the release of taste-active peptides from soybean isolate catalyzed by proteases from Aspergillus flavus strains. The frequent presence of Leu at the C-terminus and the hydrophilic amino acids at the N-terminus related to bitterness and umami taste of hydrolysates, respectively. Detailly, H40650 demonstrating high umami, low bitterness, and a high peptide yield. During the hydrolysis of H40650, umami taste changes were associated with the content of peptides <1 kDa and 28 umami peptides, while bitterness was linked to the content of peptides <3 kDa and 30 bitter peptides. Additionally, most taste-active peptides were derived from the 7S globulin α subunit and 11S globulin G2. The protease produced by CGMCC 40650 has marked specificity for the region of 281-333 amino acids in protein P0D15, which contained 24.53 % umami amino acids. These findings could offer new insights into the preparation of taste-active peptides.

Identification, characterization and molecular docking study of umami peptides from Spanish mackerel head enzymatic hydrolysate and Maillard reaction products

Umami peptides were screened and identified from the enzymatic hydrolysate of Spanish mackerel head and its Maillard reaction products using ultrafiltration, gel chromatography, and LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry). The umami properties of these peptides were subsequently evaluated and characterized using electronic tongue analysis and molecular docking. This study is the first to employ enzymatic hydrolysis combined with Maillard reaction for the preparation of umami peptides from Spanish mackerel head. Following this approach, a total of nine novel umami peptides were identified, including five from enzymatic hydrolysate (YDDKIY, ITPDEKGTTF, DAITTDDAGK, LEDGYPKEIQE, DAITPDEKGTTF) and four from Maillard reaction products (KDEGSDV, TPDEKGT, TEKAKGEP, FDAITPDEKGTTF). Sensory evaluation and electronic tongue analysis confirmed their distinct umami properties, with taste recognition thresholds ranging from 0.125 to 0.25 mg/mL. Molecular docking analysis revealed that these peptides interact with the T1R1/T1R3 umami receptor through hydrogen bonding and hydrophobic interactions, with key binding residues identified as Ser150, Ser256, and Glu128. This study provides a novel methodology for screening umami peptides from seafood by-products and lays the groundwork for their application as natural umami enhancers in the food industry.

Insights from traditional fermented legumes towards the innovation of modern plant-based meat analogues

There has been a major growth in the development of plant-based meat alternatives (PBMA) in recent years. However, current PBMA often contain ultra processed ingredients and numerous additives to be able to mimic animal-based meat (ABM) including the meaty (umami) flavour, characteristic firm/chewy structure and juicy mouthfeel. In this review, the potential of ancient fermentation techniques as a minimally processed alternative to ABM and current PBMA are explored. Fermented foods including tempeh, natto, dawadawa and ugba are naturally high in protein and umami flavours. The nutritional, aroma, flavour and techno-functional properties are provided and discussed in the context of ABM and PBMA. The fermented foods have potential to be used as whole foods ingredients, or their constituents can be used as ingredients in plant-based foods. Particularly the umami flavours and high protein content combined with the naturally occurring high water holding capacity (WHC), solubility and other material properties make fermented legume foods suitable candidates for use in high-protein plant-based foods. Understanding the sensory characteristics and material properties generated during legume fermentation and their similarities to ABM can aid in stimulating innovations in food technology to obtain a new generation of less-processed PBMA with limited additives.

A novel directed enzymolysis strategy for the preparation of umami peptides in Stropharia rugosoannulata and its mechanism of taste perception

This study aimed to explore the effect of directed enzymolysis on the umami characteristics of S. rugosoannulata, clarify the flavour formation mechanism of umami peptides. We expressed a new aminopeptidase (DNPEP) and obtained the umami peptides of S. rugosoannulata by alkaline protease and DNPEP. The optimal enzymolysis conditions were temperature 55 °C, solid-liquid ratio 1:20 (g/mL), alkaline protease enzymolysis (60 min, 0.5 %, pH 9.0), and DNPEP enzymolysis (80 min, 0.3 %, pH 8.0). The umami peptide components were separated by ultrafiltration and gel filtration chromatography. Six umami peptides (EEAKFN, KAELDLH, LADVEEDK, LKEAHDVA, AHLDYGDGK, and LGKSEDDVSK) were identified by LC-MS/MS and virtual screening, and the umami thresholds of the peptides were 0.15-1.09 mmol/L. Molecular simulations revealed that the amino acid residues Glu301, Ser217, Asp218, and Arg277 were crucial in the binding of the umami peptide to the T1R1/T1R3. Therefore, this study provides a theoretical basis for the development of mushroom condiments.

Identification and characterization of umami-ACE inhibitory peptides from traditional fermented soybean curds

Fermented soybean curds (FSC) are popular because of its umami taste. Its bioactivities are of interest. Peptides in FSC were identified using nano-HPLC-MS/MS, and 11 candidate peptides showing potential umami and ACE inhibitory activities were screened using various databases. Pharmacophore model analysis showed their high probability of ACE inhibition with fit values >2, which showed the peptides bound to umami receptors and ACE mainly through hydrogen bond, and electrostatic and hydrophobic interactions. Additionally, their docking and interaction energy were independent of the peptide length. Three high umami-ACE inhibitory peptides (VE, FEF, and WEEF) were synthesized. Their umami thresholds were WEEF (0.32 mM) < FEF (0.55 mM) < VE (1.10 mM), while their IC50 were WEEF (85 ± 2 μM) < FEF (170 ± 10 μM) < VE (205 ± 5 μM). NO and ET-1 production were dose-dependent with WEEF showing the best ACE inhibitory activity. The results allowed identification of effective umami agents and ACE inhibitory peptides from fermented soybean products. It could also be useful method for screening potential umami-ACE inhibitory peptides.

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.

Characterization and peptide identification of umami fractions from rusip-a traditional fermented anchovy product

Rusip is a spontaneously fermented anchovy product originating from Bangka Belitung province in Indonesia, used as umami seasoning. This study investigated the characteristics of rusip and its umami fractions to reveal umami peptides in rusip. Six commercial rusip samples from Bangka were analyzed for their proximate composition, pH, total titratable acids, NaCl, total sugars, free glutamic acid, nucleotide (adenosine monophosphate), and total amino acid composition. Umami taste intensity of water-soluble extracts (WSE) was analyzed by a sensory panel. Total plate count and total lactic acid bacteria were also analyzed to assess the microbial variations between the samples. Stepwise ultrafiltration on the highest umami intensity WSE was conducted to obtain three fractions: >5 kDa, 3-5 kDa, and <3 kDa, followed by chromatography fractionation of fraction <3 kDa by Sephadex G-15 gel to acquire umami fractions (F1-F4). Protein (28.94%-44.53% dry weight basis [db]) and NaCl (30.86%-55.73% db) were the major solids of rusip. Concentrations of free glutamic acid (5.79%-8.99% db) in rusip are related with umami intensities of WSE. F1 was the umami fraction with its residual umami amino acids higher than its free ones; therefore, F1 was also a peptide fraction. It contained peptides of 3-12 residues within the highest relative area. Their sequences contained those of umami peptides listed in BIOPEP database. Some of these peptides were also associated with bioactivities. This information could broaden the insight of umami peptides and their bioactivities in fermented foods. PRACTICAL APPLICATION: Rusip is used as a source of umami ingredient in food. The characteristics of product quality of rusip were reported in this study. In addition, the chemical and sensory characteristics as well as peptides of its umami fraction were also described. This information is important for the exploration of umami peptides from fish fermented products.

Enzymatic Preparation, Identification by Transmembrane Channel-like 4 (TMC4) Protein, and Bioinformatics Analysis of New Salty Peptides from Soybean Protein Isolate

To address the public health challenges posed by high-salt diets, this study utilized pepsin and flavourzyme for the continuous enzymatic hydrolysis of a soy protein isolate (SPI). The separation, purification, and identification of salt-containing peptides in SPI hydrolysate were conducted using ultrafiltration (UF), gel filtration chromatography (GFC), and Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS). Subsequently, a molecular docking model was constructed between salt receptor protein transmembrane channel 4 (TMC4) and the identified peptides. Basic bioinformatics screening was performed to obtain non-toxic, non-allergenic, and stable salt peptides. After the enzymatic hydrolysis, separation, and purification of SPI, a component with a sensory evaluation score of 7 and an electronic tongue score of 10.36 was obtained. LC-MS/MS sequencing identified a total of 1697 peptides in the above component, including 84 potential salt-containing peptides. A molecular docking analysis identified seven peptides (FPPP, GGPW, IPHF, IPKF, IPRR, LPRR, and LPHF) with a strong theoretical salty taste. Furthermore, residues Glu531, Asp491, Val495, Ala401, and Phe405 of the peptides bound to the TMC4 receptor through hydrogen bonds, hydrophobic interactions, and electrostatic interactions, thereby imparting a significant salty taste. A basic bioinformatics analysis further revealed that IPHF, LPHF, GGPW, and IPKF were non-toxic, non-allergenic, and stable salt-containing peptides. This study not only provides a new sodium reduction strategy for the food industry, but also opens up new avenues for improving the public's healthy eating habits.

UmamiPreDL: Deep learning model for umami taste prediction of peptides using BERT and CNN

Taste is crucial in driving food choice and preference. Umami is one of the basic tastes defined by characteristic deliciousness and mouthfulness that it imparts to foods. Identification of ingredients to enhance umami taste is of significant value to food industry. Various models have been shown to predict umami taste using feature encodings derived from traditional molecular descriptors such as amphiphilic pseudo-amino acid composition, dipeptide composition, and composition-transition-distribution. Highest reported accuracy of 90.5 % was recently achieved through novel model architecture. Here, we propose use of biological sequence transformers such as ProtBert and ESM2, trained on the Uniref databases, as the feature encoders block. With combination of 2 encoders and 2 classifiers, 4 model architectures were developed. Among the 4 models, ProtBert-CNN model outperformed other models with accuracy of 95 % on 5-fold cross validation data and 94 % on independent data.

Current trends and perspectives on salty and salt taste-enhancing peptides: A focus on preparation, evaluation and perception mechanisms of salt taste

Long-term excessive intake of sodium negatively impacts human health. Effective strategies to reduce sodium content in foods include the use of salty and salt taste-enhancing peptides, which can reduce sodium intake without compromising the flavor or salt taste. Salty and salt taste-enhancing peptides naturally exist in various foods and predominantly manifest as short-chain peptides consisting of < 10 amino acids. These peptides are primarily produced through chemical or enzymatic hydrolysis methods, purified, and identified using ultrafiltration + gel filtration chromatography + liquid chromatography-tandem mass spectrometry. This study reviews the latest developments in these purification and identification technologies, and discusses methods to evaluate their effectiveness in saltiness perception. Additionally, the study explores four biological channels potentially involved in saltiness perception (epithelial sodium channel, transient receptor potential vanilloid 1, calcium-sensing receptor (CaSR), and transmembrane channel-like 4 (TMC4)), with the latter three primarily functioning under high sodium levels. Among the channels, salty taste-enhancing peptides, such as γ-glutamyl peptides, may co-activate the CaSR channel with calcium ions to participate in saltiness perception. Salty taste-enhancing peptides with negatively charged amino acid side chains or terminal groups may replace chloride ions and activate the TMC4 channel, contributing to saltiness perception. Finally, the study discusses the feasibility of using these peptides from the perspectives of food material constraints, processing adaptability, multifunctional application, and cross-modal interaction while emphasizing the importance of utilizing computational technology. This review provides a reference for advancing the development and application of salty and salt-enhancing peptides as sodium substitutes in low-sodium food formulations.

Sensoproteomic Characterization of Lactobacillus Johnsonii-Fermented Pea Protein-Based Beverage: A Promising Strategy for Enhancing Umami and Kokumi Sensations while Mitigating Bitterness

This study investigated the mechanism underlying the flavor improvement observed during fermentation of a pea protein-based beverage using Lactobacillus johnsonii NCC533. A combination of sensomics and sensoproteomics approach revealed that the fermentation process enriched or generated well-known basic taste ingredients, such as amino acids, nucleotides, organic acids, and dipeptides, besides six new taste-active peptide sequences that enhance kokumi and umami notes. The six new umami and kokumi enhancing peptides, with human recognition thresholds ranging from 0.046 to 0.555 mM, are produced through the degradation of Pisum sativum's storage protein. Our findings suggest that compounds derived from fermentation enhance umami and kokumi sensations and reduce bitterness, thus improving the overall flavor perception of pea proteins. In addition, the analysis of intraspecific variations in the proteolytic activity of L. johnsonii and the genome-peptidome correlation analysis performed in this study point at cell-wall-bound proteinases such as PrtP and PrtM as the key genes necessary to initiate the flavor improving proteolytic cascade. This study provides valuable insights into the molecular mechanisms underlying the flavor improvement of pea protein during fermentation and identifies potential future research directions. The results highlight the importance of combining fermentation and senso(proteo)mics techniques in developing tastier and more palatable plant-based protein products.

Comparative peptidomics analysis in the discovery of umami peptides from Chinese Douchi

Douchi is a kind of traditional Chinese fermented soybean product with outstanding umami taste. Besides the umami amino acids in Douchi, peptides were also considered as an important contributor for the umami taste of Douchi. Peptides with molecular weight below 0.66 kDa accounted for more than 50 % in all samples except for TongChuan Douchi, and a total of 421 peptides were identified from the ten kinds of Douchi samples by using LC-MS/MS. Combined with sensory evaluation results, 19 peptides containing Glu, Asp or known umami peptide sequences were chosen as potential umami peptides via PLS-DA and RDA analysis. Among them, 17 soluble peptides exhibited obvious umami taste and the threshold of 7 peptides were lower than MSG solution. Especially, the VD was detected with a minimum umami taste threshold at 0.16 mg/mL. The results indicated that the umami peptides might be the important components affecting the umami taste of Douchi.

Plant Protein-Derived Active Peptides: A Comprehensive Review

Active peptides are a class of physiologically active protein fragments, which can be prepared from different sources. In the past few decades, the production of peptides with various effects from different plant proteins continues to receive academic attention. With advances in extraction, purification, and characterization techniques, plant protein-derived active peptides continue to be discovered. They have been proven to have various functional activities such as antioxidant, antihypertensive, immunomodulatory, antimicrobial, anti-inflammatory, antidiabetic, antithrombotic, and so on. In this review, we searched Web of Science and China National Knowledge Infrastructure for relevant articles published in recent years. There are 184 articles included in this manuscript. The current status of plant protein-derived active peptides is systematically introduced, including their sources, preparation, purification and identification methods, physiological activities, and applications in the food industry. Special emphasis has been placed on the problems of active peptide exploration and the future trend. Based on these, it is expected to provide theoretical reference for the further exploitation of plant protein-derived active peptides, and promote the healthy and rapid development of active peptide industry.

Microbiology of fermented soy foods in Asia: Can we learn lessons for production of plant cheese analogues?

The food industry is facing the challenge of creating innovative, nutritious, and flavored plant-based products, due to consumer's increasing demand for the health and environmental sustainability. Fermentation as a unique and effective tool plays an important role in the innovation of food products. Traditional fermented soy foods are popular in many Asian and African countries as nutritious, digestible and flavorful daily staples or condiments. They are produced by specific microorganisms with the unique fermentation process in which microorganisms convert the ingredients of whole soybean or soybean curd to flavorful and functional molecules. This review provides an overview on traditional fermented food produced from soy, including douchi, natto, tempeh, and sufu as well as stinky tofu, including the background of these products, the manufacturing process, and the microbial diversity involved in fermentation procedures as well as flavor volatiles that were identified in the final products. The contribution of microbes to the quality of these five fermented soy foods is discussed, with the comparison to the role of cheese ripening microorganisms in cheese flavor formation. This communication aims to summarize the microbiology of fermented soy foods in Asia, evoking innovative ideas for the development of new plant-based fermented foods especially plant-based cheese analogues.

Identification, Characterization, and Receptor Binding Mechanism of New Umami Peptides from Traditional Fermented Soybean Paste (Dajiang)

Dajiang, a traditional Chinese condiment, is made from fermented soybeans. It is highly popular among consumers as a result of its delicious umami flavor, which mainly originates from umami peptides. To examine the mechanism of umami taste in Dajiang, we selected Dajiang samples with strong umami taste and subjected them to purification and identification analysis using ethanol precipitation, gel chromatography, reversed-phase high-performance liquid chromatography, and ultraperformance liquid chromatography-tandem mass spectrometry. Subsequently, on the basis of toxicity and umami prediction analysis, we screened, synthesized, and characterized three novel bean umami peptides in Dajiang: TLGGPTTL, 758.4174 Da; GALEQILQ, 870.4811 Da; and HSISDLQ, 911.4713 Da. Their sensory threshold values were 0.25, 0.40, and 0.17 mmol/L, respectively. Furthermore, molecular docking results showed that hydrogen-bonding and hydrophobic interactions are important interaction forces in the binding of umami peptide to taste receptors. Ser147 and Glu148 of the T1R3 taste receptor are important amino acid residues for binding of the three umami peptides. This study uncovers the mechanism of umami-peptide-driven flavor in fermented soybean products.

Recent advances in taste transduction mechanism, analysis methods and strategies employed to improve the taste of taste peptides

Taste peptides are oligopeptides that enhance both aroma and taste of food, and they are classified into five categories based on their taste characteristics: salty, sour, umami, sweet, bitter, and kokumi peptide. Recently, taste peptides have attracted the attention of several fields of research in food science and commercial applications. However, research on taste receptors of taste peptides and their taste transduction mechanisms are not clearly understood and we present a comprehensive review about these topics here. This review covers the aspects of taste peptides perceived by their receptors in taste cells, the proposed transduction pathway, as well as structural features of taste peptides. Apart from traditional methods, molecular docking, peptidomic analysis, cell and animal models and taste bud biosensors can be used to explore the taste mechanism of taste peptides. Furthermore, synergistic effect, Maillard reaction, structural modifications and changing external environment are employed to improve the taste of taste peptides. Consequently, we discussed the current challenges and future trends in taste peptide research. Based on the summarized developments, taste peptides derived from food proteins potentially appear to be important taste substances. Their applications meet the principles of "safe, nutritious and sustainable" in food development.

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.

Identification of novel α-glucosidase and ACE inhibitory peptides from Douchi using peptidomics approach and molecular docking

In this study, the effect of Douchi extract (DWE) on α-glucosidase and angiotensin-converting enzymes (ACE) were investigated, and several novel peptides with inhibitory activity against α-glucosidase and ACE were identified using peptidomics approach based on UPLC-MS/MS. The average inhibition rates of DWE on α-glucosidase and ACE were 73.75-78.10% and 4.56-27.07%, respectively. In the DWE, a total of 710 peptides were detected. Two novel peptides with potential inhibitory activity against α-glucosidase were identified using the correlation analysis, database alignment and molecular docking methods. They were DVFRAIPSEVL and DRPSINGLAGAN, with the IC50 values of 0.121 and 0.128 mg/mL, respectively. Also, four novel peptides with potential inhibitory activity against ACE were identified: PSSPFTDLWD, EEQDERQFPF, PVPVPVQQAFPF and PSSPFTDL, with IC50 values of 1.388, 0.041, 0.761 and 0.097 mg/mL, respectively. These results indicated that combining peptidomics and molecular docking is an effective alternative strategy for rapidly screening numbers of novel bioactive peptides from foods.

Identification of umami peptides from Wuding chicken by Nano-HPLC-MS/MS and insights into the umami taste mechanisms

Wuding chicken is popular with consumers in China because of its umami taste. This study aimed to identify novel umami peptides from Wuding chicken and explore the taste mechanism of umami peptides. The molecular masses and amino acid compositions of peptides in Wuding chicken were identified by nano-scale liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). The taste characteristics of the peptides synthesized by the solid-phase method were evaluated by sensory evaluation combined with electronic tongue technology. The secondary structure of the peptides was further analyzed by circular dichroism (CD), and the relationship between the structure and taste of the peptides was elucidated by molecular docking. The results showed that eight potential umami peptides were identified, among which FVT (FT-3), LDF (LF-3), and DLAGRDLTDYLMKIL (DL-15) had distinct umami tastes, and FT-3 had the highest umami intensity, followed by LF-3 and DL-15. The relative contents of β-sheets in the three umami peptides were 55.20%, 57.30%, and 47.70%, respectively, which were the key components of Wuding chicken umami peptides. In addition to LF-3 embedded in the cavity-binding domain of the TIR1, both FT-3 and DL-15 were embedded in the venus flytrap domain (VFTD) of the T1R3 to bind the umami receptor T1R1/T1R3. The main binding forces between the umami peptides and the umami receptor T1R1/T1R3 relied on hydrogen bonds and hydrophobic interactions, and the key amino acid residues of the combination of umami peptides and the umami receptor T1R1/T1R3 were Glu292, Asn235, and Tyr262.

Revealing the Secret of Umami Taste of Peptides Derived from Fermented Broad Bean Paste

To understand the umami taste of fermented broad bean paste (FBBP) and explore the umami mechanism, eight peptides (PKALSAFK, NKHGSGK, SADETPR, EIKKAALDANEK, DALAHK, LDDGR, and GHENQR) were separated and identified via ultrafiltration, RP-HPLC, and UPLC-QTOF-MS/MS methods. Sensory experiments suggested that eight novel peptides showed umami/umami-enhancing and salt-enhancing functions. Significantly, the threshold of EIKKAALDANEK in aqueous solution exceeded that of most umami peptides reported in the past 5 years. The omission test further confirmed that umami peptides contributed to the umami taste of FBBP. Molecular docking results inferred that all peptides easily bind with Ser, Glu, His, and Asp residues in T1R3 through hydrogen bonds and electrostatic interactions. The aromatic interaction, hydrogen bond, hydrophilicity, and solvent-accessible surface (SAS) were the main interaction forces. This work may contribute to revealing the secret of the umami taste of FBBP and lay the groundwork for the efficient screening of umami peptides.

Molecular dynamic simulations identifying the mechanism of holoenzyme formation by O-GlcNAc transferase and active p38α

O-N-Acetylglucosamine transferase (OGT) can catalyze the O-GlcNAc modification of thousands of proteins. The holoenzyme formation of OGT and adaptor protein is the precondition for further recognition and glycosylation of the target protein, while the corresponding mechanism is still open. Here, static and dynamic schemes based on statistics can successfully screen the feasible identifying, approaching, and binding mechanism of OGT and its typical adaptor protein p38α. The most favorable interface, energy contribution of hotspots, and conformational changes of fragments were discovered. The hydrogen bond interactions were verified as the main driving force for the whole process. The distinct characteristic of active and inactive p38α is explored and demonstrates that the phosphorylated tyrosine and threonine will form strong ion-pair interactions with Lys714, playing a key role in the dynamic identification stage. Multiple method combinations from different points of view may be helpful for exploring other systems of the protein-protein interactions.

Study on the relationship between structure and taste activity of the umami peptide of Stropharia rugosoannulata prepared by ultrasound

Through virtual screening, electronic tongue verification, and molecular docking technology, the structure-taste activity relationship of 47 kinds of umami peptides (octapeptide - undecapeptide) from Stropharia rugosoannulata prepared by simultaneous ultrasonic-assisted directional enzymatic hydrolysis was analyzed. The umami peptides of S.rugosoannulata can form hydrogen bond interaction and electrostatic interaction with umami receptors T1R1/T1R3. The amino acid residues at the peptides' N-terminal and C-terminal play a vital role in binding with the receptors to form a stable complex. D, E, and R are the primary amino acids in the peptides that easily bind to T1R1/T1R3. The basic amino acid in the peptides is more easily bound to T1R1, and the acidic amino acid is more easily bound to T1R3. The active amino acid sites of the receptors to which the peptides bind account for 42%-65% of the total active amino acid residues in the receptors. ASP147 and ASP219 are the critical amino acid residues for T1R1 to recognize the umami peptides, and ARG64, GLU45, and GLU48 are the critical amino acid residues for T1R3 to recognize the umami peptides. The increase in the variety and quantity of umami peptides is the main reason for improving the umami taste of the substrate prepared by synchronous ultrasound-assisted directional enzymatic hydrolysis. This study provides a theoretical basis for understanding simultaneous ultrasound-assisted directional enzymatic hydrolysis for preparing umami peptides from S.rugosoannulata, enhancing the flavor of umami, and the relationship between peptide structure and taste activity.

Fish proteins as potential precursors of taste-active compounds: an in silico study

BACKGROUND

Fish protein is a good source of amino acids and peptides with sensory properties. Theoretically, the type of protein affects the taste quality of the protein hydrolysates. To better use fish protein in the food ingredients industry, an in silico approach was adopted to evaluate the potential of fish protein to release taste-active compounds.

RESULTS

Six types of protein from seven commercial fishes were screened from the Uniprot knowledge base. The results showed that a remarkable number of umami fragments presented in myosin and parvalbumin (PB), such as glutamic acid (Glu), aspartic acid (Asp), and Asp- and Glu- containing peptides, whereas sweet amino acids and bitter peptides (e.g., Pro- and Gly- containing peptides) were mainly found in collagen (CGI) in all fish samples. After the in silico proteolysis by papain, a difference in the profile of taste-active fragments was observed among the six types of proteins. Amino acids were the main hydrolysis products of these proteins, especially umami, sweet, and bitter amino acids, significantly contributing to the taste formation of protein hydrolysates. Besides, the myosin and CGI hydrolysates were abundant in taste active peptides both in types and quantities.

CONCLUSION

Myosin is a promising protein source for producing umami fragments, and CGI seems to be a good precursor of sweet and bitter fragments. Different types of protein have an essential effect on the taste of protein hydrolysates. © 2022 Society of Chemical Industry.

Sensory-Guided Identification and Characterization of Kokumi-Tasting Compounds in Green Tea (Camellia sinensis L.)

The chemical substances responsible for the kokumi taste of green tea infusion are still unclear. Here, we isolated the kokumi compound-containing fractions from green tea infusion through ultrafiltration, and the major kokumi compounds were characterized as γ-Glu-Gln and γ-Glu-Cys-Gly (GSH) through ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS). The results indicated that peptides and amino acids were essential compounds in the kokumi-enriched fractions for conducting the sense of kokumi. L-theanine had an enhancing effect on the kokumi taste of green tea infusion, which was confirmed in the sensory reconstitution study. Thus, peptides, especially γ-Glu-Gln and GSH, are the major kokumi compounds in green tea infusion, which has the potential of improving the flavor of tea beverages.

Fermented Soy Products and Their Potential Health Benefits: A Review

In the growing search for therapeutic strategies, there is an interest in foods containing natural antioxidants and other bioactive compounds capable of preventing or reversing pathogenic processes associated with metabolic disease. Fermentation has been used as a potent way of improving the properties of soybean and their components. Microbial metabolism is responsible for producing the β-glucosidase enzyme that converts glycosidic isoflavones into aglycones with higher biological activity in fermented soy products, in addition to several end-metabolites associated with human health development, including peptides, phenolic acids, fatty acids, vitamins, flavonoids, minerals, and organic acids. Thus, several products have emerged from soybean fermentation by fungi, bacteria, or a combination of both. This review covers the key biological characteristics of soy and fermented soy products, including natto, miso, tofu, douchi, sufu, cheonggukjang, doenjang, kanjang, meju, tempeh, thua-nao, kinema, hawaijar, and tungrymbai. The inclusion of these foods in the diet has been associated with the reduction of chronic diseases, with potential anticancer, anti-obesity, antidiabetic, anticholesterol, anti-inflammatory, and neuroprotective effects. These biological activities and the recently studied potential of fermented soybean molecules against SARS-CoV-2 are discussed. Finally, a patent landscape is presented to provide the state-of-the-art of the transfer of knowledge from the scientific sphere to the industrial application.

Umami polypeptide detection system targeting the human T1R1 receptor and its taste-presenting mechanism

Umami is one of five basic tastes, the elucidation of its mechanism by the study of the interaction between umami polypeptides and hT1R1 umami receptors is of great significance. However, research on umami peptides targeting human T1R1 receptors is lacking, and the molecular mechanism remains elusive. Here, we successfully established a system to detect umami peptides targeting human T1R1 receptors by fluorescence spectroscopy, Surface Plasmon Resonance (SPR) and computational simulation. The sensory evaluation, calculated Kd value, and experimental affinity results between the four selected umami peptides (GRVSNCAA, KGDEESLA, KGGGGP, and TGDPEK) and glutamate were tested using this system, and all matched well. The maximum Ka value of GRVSNCAA was 479.55 M-1, and the minimum affinity of TGDPEK was 2.67 M-1. Computational simulations showed that the different peptide binding sites in the hT1R1 binding pocket occupied due to conformational changes are important factors for different taste thresholds, and that peptide hydrophobicity plays an important role in regulating affinity. Thus, our study enables rapid screening of high-intensity umami peptides and the development of T1R1 receptor-based umami detection sensors.

Taste peptides derived from Stropharia rugosoannulata fermentation mycelium and molecular docking to the taste receptor T1R1/T1R3

This study identified the peptides in the fermentation mycelia of Stropharia rugosoannulata. The molecular weight of the peptides was below 3,000 Da. Heptapeptides to decapeptides were the main peptides in the fermentation mycelia of S. rugosoannulata. More than 50% of the peptides had salty and umami taste characteristics, and the long-chain peptides (decapeptides to 24 peptides) also played an essential role in the pleasant taste characteristics of mycelium. In the salty and umami peptide of S. rugosoannulata, the distribution of non-polar hydrophobic amino acids and polar-uncharged amino acids accounted for a relatively high proportion, and the proportion of polar-uncharged amino acids further increased, with the extension of the peptide chain. P, F, I, l, V, G, S, T, and D were the amino acids with a high proportion in the peptides. The taste peptides can bind to more than 60% of the active amino acid residues in the cavity-binding domain of the T1R1/T1R3 receptors. Hydrogen bond interaction was the primary mode of interaction between the peptides and the receptor. The first and second amino acid residues (such as S, V, E, K, G, and A) at the C-terminal and N-terminal of the peptides were easy to bind to T1R1/T1R3 receptors. Asp108, Asn150, Asp147, Glu301, Asp219, Asp243, Glu70, Asp218 in T1R1, and Glu45, Glu148, Glu301, Glu48, and Ala46 in TIR3 were the key active amino acid sites of taste peptides binding to T1R1/T1R3 receptors.

Characterization of Peanut Protein Hydrolysate and Structural Identification of Umami-Enhancing Peptides

Umami peptides are naturally found in various foods and have been proven to be essential components contributing to food taste. Defatted peanut powder hydrolysate produced by a multiprotease (Flavorzyme, Alcalase, and Protamex) was found to elicit an umami taste and umami-enhancing effect. The taste profiles, hydrolysis efficiency, amino acids, molecular weight distribution, Fourier transform infrared spectroscopy (FT-IR), and separation fractions obtained by ultrafiltration were evaluated. The results showed that peanut protein was extensively hydrolyzed to give mainly (up to 96.84%) free amino acids and peptides with low molecular weights (<1000 Da). Furthermore, β-sheets were the major secondary structure. Fractions of 1−3000 Da and <1000 Da prominently contributed to the umami taste and umami enhancement. To obtain umami-enhancing peptides, these two fractions were further purified by gel filtration chromatography, followed by sensory evaluation. These peptides were identified as ADSYRLP, DPLKY, EAFRVL, EFHNR, and SDLYVR by ultra-performance liquid chromatography (UPLC), and had estimated thresholds of 0.107, 0.164, 0.134, 0.148, and 0.132 mmol/L, respectively. According to the results of this work, defatted peanut powder hydrolysate had an umami taste and umami-enhancing effect, and is a potential excellent umami peptide precursor material for the food industry.

Identification of novel saltiness-enhancing peptides from yeast extract and their mechanism of action for transmembrane channel-like 4 (TMC4) protein through experimental and integrated computational modeling

Excessive consumption of sodium salt is one of the important inducers of cardiovascular and cerebrovascular diseases. The reduction of physical labor and attention to health make research on low-sodium salt imminent. Ultrafiltration, gel filtration, preparative high-performance liquid chromatography, and liquid chromatography with tandem mass spectrometry were employed for further purification and identification of the salty enhancing peptides in yeast extracts. Moreover, human transmembrane channel-like 4 (TMC4) was constructed and evaluated by computer-based methods, and salt-enhancing peptides were identified based on its allosteric sites. PN, NSE, NE and SPE were further determined to be salty enhancing peptides through sensory evaluation, and their taste mechanism was investigated. The results presented here suggest that silicon screening focused on TMC4 allosteric sites and sensory evaluation experiments can greatly increase the discoverability and identifiability of salty enhancer peptides, and this strategy is the first to be applied to the development of salty enhancer peptides.

Bioactive peptides of plant origin: distribution, functionality, and evidence of benefits in food and health

The multiple functions of peptides released from proteins have immense potential in food and health. In the past few decades, research interest in bioactive peptides of plant origin has surged tremendously, and new plant-derived peptides are continually discovered with advances in extraction, purification, and characterization technology. Plant-derived peptides are mainly extracted from dicot plants possessing bioactive functions, including antioxidant, cholesterol-lowering, and antihypertensive activities. Although the distinct functions are said to depend on the composition and structure of amino acids, the practical or industrial application of plant-derived peptides with bioactive features is still a long way off. In summary, the present review mainly focuses on the state-of-the-art extraction, separation, and analytical techniques, functional properties, mechanism of action, and clinical study of plant-derived peptides. Special emphasis has been placed on the necessity of more pre-clinical and clinical trials to authenticate the health claims of plant-derived peptides.

A rational tool for the umami evaluation of peptides based on multi-techniques

Umami peptides have become of key interest in the development of flavoring agents. However, the lack of known umami peptides further prevents the understanding of the umami mechanism. The famous pufferfish (Takifugu flavidus) is a great resource for novel umami peptides, and we further analyze the umami characteristics of peptides based on multi-evaluation. In this study, five novel umami peptides, DF9, TK18, AK11, IK10, and GT12 were found; DF9 having the highest umami intensity, followed by AK11. Moreover, biosensor results showed DF9 with the lowest K_a value of 6.85 × 10^-13 mol/L, followed by AK11. These data are mostly in agreement with sensory evaluation and fully reveal the umami mechanism of peptides. Quantum chemical and molecular docking demonstrated active site D in peptides bound with T1R1 receptor. Our results open up new strategies to estimate the taste characteristics of umami peptides and provide rational tools for screening umami peptides in food.

In-silico investigation of umami peptides with receptor T1R1/T1R3 for the discovering potential targets: A combined modeling approach

Umami, providing amino acids/peptides for animal growth, represents one of the major attractive taste modalities. The biochemical and umami properties of peptide are both important for scientific research and food industry. In this study, we did the sequence analysis of 205 umami peptides with 2-18 amino acids, sought the active sites of umami peptides by quantum chemical simulations and investigated their recognition residues with receptor T1R1/T1R3 by molecular docking. The results showed the peptides with 2-3 amino acids accounting for 44% of the total umami peptides. Residues D and E are the key active sites no matter where they are in the peptides (N-terminal, C-terminal or middle), when umami peptides contain D/E residues. N69, D147, R151, A170, S172, S276 and R277 residues in T1R1 receptor were deemed to be the key residues binding umami peptides. Finally, a powerful decision rule for umami peptides was proposed to predict potential umami peptides, which was convenient and efficient.

Novel umami peptides from tilapia lower jaw and molecular docking to the taste receptor T1R1/T1R3

This study aimed to isolate and identify peptides with intense umami taste from tilapia lower jaw. The aqueous extract was separated using ultrafiltration and Sephadex G-15 gel filtration chromatography. The peptide fraction with an intense umami taste was selected by sensory evaluation. The five novel peptides with strong umami taste were VADLMR, STELFK, FVGLQER, DALKKK, and VVLNPVARVE. Electronic tongue analysis and sensory evaluation showed that five peptides had obvious umami taste characteristics, and the recognition thresholds of umami peptides were in the range 0.125-0.250 mg/mL. Molecular docking was used to study the interaction of the peptides and umami taste receptor T1R1/T1R3. The five peptides could perfectly be inserted into the binding pocket of the Venus flytrap domain in the T1R3 subunit. Hydrogen bonding and hydrophobic interaction were the important interaction forces. The five peptides may bind with Asp219, Glu217, and Glu148 in T1R1/T1R3 receptor and produce the umami taste.

Analysis of umami taste substances of morel mushroom (Morchella sextelata) hydrolysates derived from different enzymatic systems

Seven enzyme groups were applied to hydrolyze broken fruiting bodies of morel mushroom (Morchella sextelata) to extract umami substances. Physical-chemical properties, as well as compositions and concentrations of quintessential umami compounds of morel hydrolysates were analyzed. Electronic tongue and electronic nose were used to evaluate the sensory characteristics. The results suggested that peptides below 3 kDa showed the highest correlation with umami taste. Morel hydrolysate obtained from Neutrase-Flavourzyme (NF) combination contained the most contents of small peptides (<3 kDa), free amino acids (224.83 ± 0.87 mg/g), as well as flavor 5'-nucleotides (4.84 ± 0.32 mg/g), giving the best overall flavor properties. The reaction conditions of NF were optimized by response surface methodology (RSM). The highest degree of hydrolysis (DH) was up to 36.64%. An enzymatic hydrolysis approach was established to develop novel flavor products with high umami and low bitter taste from morel mushroom.

Fermented Soy Products: Beneficial Potential in Neurodegenerative Diseases

Fermented soybean products, such as cheonggukjang (Japanese natto), doenjang (soy paste), ganjang (soy sauce), and douchi, are widely consumed in East Asian countries and are major sources of bioactive compounds. The fermentation of cooked soybean with bacteria (Bacillus spp.) and fungi (Aspergillus spp. and Rhizopus spp.) produces a variety of novel compounds, most of which possess health benefits. This review is focused on the preventive and ameliorative potential of fermented soy foods and their components to manage neurodegenerative diseases, including Alzheimer's and Parkinson's diseases.