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

TMC4 receptor binding properties and interaction mechanisms of salty mushroom peptides

The transmembrane channel-like protein 4 (TMC4) has been identified as a receptor for anionic salty compounds. However, whether salty peptides can activate TMC4 remains unresolved, and the underlying interaction mechanism between these peptides and the receptor is also unclear. In this study, we analyzed the binding properties and interaction mechanisms of salty mushroom peptides with the TMC4 receptor. A spontaneous, enthalpy-driven specific binding reaction was observed, with TMC4 binding to 2 molecules of the salty peptide KSWDDFFTR and 4 molecules of the peptide RIEDNLVIIR. The intracellular amino acid residues in pocket 1 of the receptor primarily recognized KSWDDFFTR, whereas the extracellular amino acid residues in pocket 4 predominantly bound to RIEDNLVIIR. Notably, the TMC4 receptor can be activated by the salty peptides, and the receptor specifically recognized uncharged peptides. Insights into the interaction between salty peptides and TMC4 may pave the way for the development of novel food additives.

Identification of novel umami peptides from oyster hydrolysate and the mechanisms underlying their taste characteristics using machine learning

Excessive sodium consumption poses considerable health risks, prompting the exploration of umami peptides as potential alternative for reducing sodium intake. This research investigated umami peptides (PQFAPEED, EEHPVLLTEA and DQAIPNKPEE) using machine learning, determining sensory thresholds to be 0.24, 0.30 and 0.29 mg/mL. Molecular docking studies revealed hydrogen bonds and hydrophobic interactions are vital for their binding to umami receptors T1R1/T1R3, with key residues identified as Val714, Leu852, Gln853 and Glu855. Combination of DQAIPNKPEE with 3 mg/mL sodium chloride (NaCl) closely mimicked the salinity perception of 5 mg/mL NaCl. Additionally, DQAIPNKPEE and PQFAPEED were recognised as salt-enhancing peptides, with Ala283, Glu284, Glu286, Arg294, Arg330 and Arg583 identified as critical amino acid residues of human transmembrane channel-like 4 (TMC4). These peptides substitute chloride ions to activate TMC4, resulting in sensation of saltiness. This study highlights efficacy of machine learning in rapid identification of umami peptides from oysters and taste receptors interactions.

Identification, saltiness-enhancing effect, and antioxidant properties of novel saltiness-enhancing peptides from peanut protein

In order to reduce the use of traditional salt (NaCl), this study aimed to rapidly identify novel peptides with salt-reducing effects from peanut protein. Four potential peptides were identified through virtual screening and molecular docking. The sensory evaluation and electronic tongue confirmed that the peptides SPDIY, DPSPR, QPGDY, and SPPGER had significant saltiness-enhancing effects, with saltiness enhancement thresholds ranging from 0.16 to 0.64 mmol L-1. Among them, DPSPR exhibited the most pronounced effect in enhancing saltiness, capable of replacing approximately 56.7% of NaCl. Molecular docking and dynamics simulation studies indicated that amino acid residues Arg272, Glu161, Gln279, Arg168, and Ser165 were found to play key roles in ligand-receptor binding. Additionally, antioxidant activity assays demonstrated that the peptide QPGDY contributed to free radical scavenging in a dose-dependent manner through the hydrogen atom transfer mechanism. The combination of virtual screening technology and experimental validation greatly improved the efficiency and accuracy of peptide discovery and functional characterization, offering a promising strategy for the development of low-sodium foods with antioxidant properties.

Identification and molecular mechanism of novel salt-enhancing peptide in crocodile hemoglobin: a combined E-tongue, molecular docking, and dynamic simulation

BACKGROUND

This study aimed to reduce salt intake without compromising food sensory properties. Novel salt-enhancing peptides were identified from crocodile hemoglobin via virtual screening and evaluated for their salt-reducing effects using molecular docking, electronic tongue analysis, and molecular dynamics simulations.

RESULTS

A total of 24 water-soluble and non-toxic peptides were obtained by virtual enzymolysis. The protein structure of human transmembrane channel-like 4 (TMC4), a novel salt taste receptor, was constructed using AlphaFold2 and applied as a receptor. The salt-reducing effect of these peptides was verified using electronic tongue analysis, in which the peptide SSDDK had a significant salt-reducing effect. Molecular docking results showed that the main force for peptide binding to the TMC4 receptor was conventional hydrogen bonding, and Arg 583, Arg330, and Glu284 were the key amino acid residues for its binding. Molecular dynamics simulations also verified the stability of peptide-receptor binding.

CONCLUSION

This study demonstrates that the peptide SSDDK, derived from crocodile hemoglobin, can be used to enhance salty taste and reduce sodium salt use. © 2025 Society of Chemical Industry.

Advances in Reducing Salt Content in Processed Meats with Basic Amino Acids

Basic amino acids have emerged as a pivotal area of research in efforts to decrease the sodium content in meat products, primarily due to their ability to enhance flavor, improve taste, and effectively replace sodium salts. This review synthesizes current strategies for sodium reduction in meat products and offers an overview of previous studies examining the role of basic amino acids in such applications, including their impact on sensory attributes and structural alterations. Furthermore, the implications of these strategies on product quality are examined, addressing aspects such as protein hydrolysis, oxidation, color, and textural changes, as well as potential underlying mechanisms. Additionally, future challenges and trends in the utilization of basic amino acids in processed meats are explored. Overall, basic amino acids exhibit significant potential as sodium salt substitutes, particularly at low NaCl concentrations. Their combinations with chloride salts, yeast extracts, and other salts have been explored as alternative sodium reduction strategies. However, challenges remain in their application to meat products, including high production costs, consumer acceptance, and stability during large-scale production. Future research should focus on optimizing the use of basic amino acids, enhancing their economic feasibility, and addressing technical hurdles.

Umami and saltiness enhancements of textured pea proteins by combining protease- and glutaminase-catalyzed reactions

Plant-based meat analogs (PBMAs) have attracted attention owing to their various advantages, however, their taste limits their application, requiring improvement of the umami and saltiness levels while meeting clean-label requirements. Enzymatic treatments for food processing are effective strategies for developing clean-label food products because enzymes are not considered food additives. In this study, we aimed to enhance the umami and saltiness intensity of PBMA patties by combining protease- and glutaminase-catalyzed reactions. For the production of extrudates to construct PBMA patties, enzymatically hydrolyzed pea proteins (eHPP) were produced via enzyme catalysis combinations, followed by the preparation of eHPP-mixed textured pea protein (eTPP) from eHPP and starch. Sensory evaluation revealed that the umami, kokumi, and saltiness levels of the eTPP-based patties containing 0.5% NaCl were significantly higher than those of the control patties containing 0.5% NaCl. Notably, the eTPP-based patties exhibited a 20% salt reduction. By screening for saltiness-enhancing amino acids and peptides released from eTPP-based patties in artificial saliva, the combination of Glu, Arg, Lys, and the separated peptide 3 was determined important in enhancing the saltiness intensity of NaCl. Moreover, it was revealed that the saltiness-enhancing peptide 3 may be a Maillard-induced peptide, based on the Lys residues in Glu-Gly-Lys-Gly and 5-hydroxymethylfurfural condensed from Glucose in starch during the extrusion process. Our findings suggest that the combination of proteases and glutaminases could be an attractive approach to enhance the umami and saltiness levels of PBMA products while meeting clean-label requirements.

Molecular Characteristics and Thermal Stability of Salty/Saltiness-Enhancing Peptides from Enzymatic Hydrolysates of Agaricus bisporus

Agaricus bisporus peptides with a saltiness-enhancing effect (24%) were obtained through favorable enzymatic hydrolysis conditions. To identify the molecular characteristics of saltiness-enhancing peptides, A. bisporus protein was extracted and hydrolyzed under the selected optimal conditions. The resulting peptides were further separated through ultrafiltration and gel chromatography and characterized by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular docking was then performed with the transmembrane channel-like 4 (TMC4), leading to the identification of four key peptides: WDDVRGW, GRGGYFDEF, ARSIGVS, and WDEVRGE. The synthetic WDDVRGW was proved to be a salty peptide and saltiness-enhancing peptide. The aqueous solution of 0.05% WDDVRGW displayed a saltiness of 3.66 ± 0.13, and 0.005% WDDVRGW with 0.4% NaCl solution presented a saltiness of 4.93 ± 0.05, showing a saltiness enhancement of 11.4%. Both synthetic and enzymatic hydrolyzed peptides exhibited higher saltiness-enhancing effects at lower NaCl concentrations. A. bisporus peptides can maintain a high saltiness-enhancing effect (>15%) after the thermal process at 105-125 °C for 120 min, exhibiting desirable thermal stability. The initial pH of 8.0 in the thermal reaction solution was more beneficial to the formation of saltiness-enhancing peptides.

In Slico Screening and In Vitro Identification of Hyperuricemia-Inhibiting Peptides from Trachurus japonicus

Hyperuricemia arises from imbalanced uric acid metabolism, contributing to gout and related chronic diseases. When traditional drugs are used to treat hyperuricemia, side effects are inevitable, which promotes the exploration of new bioactive compounds. Protein hydrolysates and peptides are gradually showing potential in the treatment of hyperuricemia. This study investigated the uric acid inhibitory activity of peptides extracted from Trachurus japonicus using in silico and in vitro methods. We employed in silico virtual enzymolysis and experimental validation to identify bioactive peptides from Trachurus japonicus proteins. Four peptides (DF, AGF, QPSF, and AGDDAPR) were comprehensively screened by molecular docking and database analysis. After solid-phase synthesis, the inhibitory effects of these peptides on hyperuricemia were further verified in vitro and at the cellular level. The results showed that all four peptides have good hyperuricemia-inhibiting activities. Molecular docking and molecular dynamics revealed that peptides DF and AGDDAPR affect the production of uric acid by binding to the active sites of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), and xanthine oxidase (XOD), while peptides QPSF and AGF mainly influence the XOD active site, confirming that it is feasible to rapidly screen hyperuricemia-inhibiting peptides by molecular docking.

Discovery of novel saltiness-enhancing peptides from yeast extract and evaluation of their bidirectional saltiness regulation effects

This study was undertaken to uncover peptides from yeast extract that can enhance the perception of saltiness and to explore their effects on saltiness enhancement. Utilizing nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS) analysis, we identified peptides present in yeast extract. Through a virtual screening strategy, we selected fourteen candidate peptides with potential to enhance saltiness, along with two arginyl dipeptides. Molecular docking indicated that these peptides primarily interact with salt taste receptors via hydrogen bonding, with key binding sites identified as Arg583, Glu 326, and Tyr487, Arg491 for the taste receptors TMC4 and TRPV1, respectively. Sensory evaluation demonstrated that the saltiness-enhancing peptides (ADWPR, GDVDPF, NVDPF, WPEMDAL, LR, and VR) not only intensified the saltiness of a 0.30 % sodium chloride (NaCl) solution but also extended the duration of the saltiness sensation. Sigmoid curve analysis confirmed that these peptides could either synergistically or additively boost the saltiness of the salt solution. Interestingly, ADWPR and WPEMDAL were observed to reduce and moderate the saltiness intensity in high-concentration NaCl solutions, indicating a bidirectional regulatory effect. These findings reveal the potential mechanisms by which yeast extract can modulate saltiness and lay the groundwork for developing strategies to reduce salt content in food products, potentially leading to healthier dietary options.

Identification of novel saltiness/saltiness enhancing peptides in egg proteins: Molecular docking, action mechanism and in vitro activity validation

In this study, novel saltiness/saltiness enhancing peptides VESQTNGIIR, NQITKPNDVY, and DEDTQAMP were identified from the hen egg proteins via virtual enzymatic, molecular docking, and electronic tongue analysis. Their saltiness enhancement effect was analyzed by e-tongue analysis. Saltiness enhancement rates of saltiness peptide VESQTNGIIR were 47.24 %, 95.28 % and 105.94 %, and those of the saltiness peptide NQITKPNDVY were 32.40 %, 70.16 %, and 71.25 % at the salt reduction concentrations of 25 %, 35 % and 45 %, respectively. Saltiness enhancement rates of saltiness enhancing peptide DEDTQAMP were 5.83 % and 11.24 % at 25 % and 35 % salt reduction concentrations, respectively. Molecular docking demonstrated that Glu286, Arg330, Arg424, and Arg583 may be the key amino acids interacting with TMC4, whereas that carbon hydrogen bond, conventional hydrogen bond, and attractive charge interactions were important forces in peptides-TMC interactions. The study indicated that the peptides VESQTNGIIR and NQITKPNDVY may be ideal saltiness/saltiness enhancing peptides.

The ENaC taste receptor's perceived mechanism of mushroom salty peptides revealed by molecular interaction analysis

The ENaC receptor acts as a taste receptor to recognize and perceive salty substances. This study explored the mechanisms by which the ENaC taste receptor recognizes and binds mushroom-derived salty peptides using molecular interaction and molecular simulation. The three subunits α, β, and γ of the ENaC taste receptor (SCNN1α, SCNN1β, and SCNN1γ) showed different recognition characteristics for the salty peptide. The salty peptide binding to the SCNN1α receptor was an entropy-driven reaction, while to SCNN1β and SCNN1γ was an enthalpy-driven reaction. With the salty peptide spatial resistance increasing, salty peptides bind to the ENaC taste receptor shifted from receptor pockets binding to receptor surface binding, with salty octapeptide ESPERPFL preferentially binding to amino acid residues in the receptor pockets 2, 3, and 4, salty nonapeptide KSWDDFFTR and decapeptide RIEDNLVIIR binding to amino acid residues in the pockets 2, 4 and on the surface of the receptor, and salty undecapeptide GQEDYDRLRPL preferentially binding to the atoms on the surface of the receptor. Receptor extracellular arginine, glutamate, aspartate, and lysine residues were the critical amino acid residues recognized to bind salty peptides. The salty peptide-ENaC receptor binding complex was stable around 0.3 nm, and the tight and multisite binding was the main reason the ENaC receptor sensed the salty peptide, enabling it to exert its taste effect. This research can provide a theoretical basis for understanding the taste properties of salty peptides recognized and perceived by the ENaC taste receptor.

Structural Feature of Salty/Saltiness-Enhancing Peptides Derived from Coprinus comatus and Their Stability during Subsequent Thermal Treatment and Maillard Reaction

Through a quantitative analysis of saltiness perception, favorable enzymatic hydrolysis parameters were confirmed for the preparation of saltiness-enhancing peptide mixtures from Coprinus comatus. The enzymatic hydrolysate was fractionated into four fractions (F1-F4) by gel chromatography, with F3 exhibiting the strongest saltiness-enhancing effect (22% increase). LC-MS/MS analysis of F3 identified 36 peptides, and their secondary structures and interactions with the TMC4 receptor were examined through circular dichroism spectroscopy and molecular docking. Molecular docking analysis revealed Asn588, Ser165, Asp5, and Arg168 as key amino acid residues, with the peptide GDNVGF showing the lowest binding energy. Synthetic GDNVGF (0.01%) in 70 mmol/L NaCl enhanced saltiness by 17%. When 0.7% GDNVGF was added to the aqueous solution, its saltiness was equivalent to that of 36.89 mmol/L NaCl, which suggested that GDNVGF functions both as a saltiness-enhancing peptide and a salty peptide. The taste changes of peptides during thermal reactions were further investigated. The thermal stability of Coprinus comatus peptides was good, but their saltiness-enhancing effect slightly reduced due to thermal degradation. The Maillard reaction further diminished this effect, though the umami level remained satisfactory, offering new insights into using Coprinus comatus peptides as low-sodium salt substitutes.

Insight into the correlation of taste substances and salty-umami taste from Monetaria moneta hydrolysates prepared using different proteases

To prepare dual-functional seasoning ingredients with a salty-umami taste, five proteases were applied to hydrolyze Monetaria moneta proteins, preparing enzymatic hydrolysates. Their taste compounds along with the salty-umami taste, were investigated. The results revealed that enzymatic hydrolysis facilitated the release of taste compounds from M. moneta. The whiteness and < 3 kDa peptides of enzymatic hydrolysates significantly increased. Moreover, flavorzyme and protamex, with high DHs, could thoroughly hydrolyze the proteins, generating the enzymatic hydrolysates abundant in taste compounds (e.g., amino acids, nucleotides) that synergistically provided a strong salty-umami taste. Saltiness and umami posed a strong positive correlation, with a correlation coefficient exceeding 0.90, resulting in the highest levels of equivalent salty intensity (ESI = 80.05 gNaCl/L) and equivalent umami concentration (EUC = 84.56 gMSG/100 g) in the flavorzyme-treated hydrolysate, followed by the protamex-treated hydrolysate. In summary, these findings offer novel insights into preparing dual-functional seasoning ingredients with a salty-umami taste, ideal for use in low-salt food production.

Exploring the salty peptides of enzymatically hydrolyzed Volvariella volvacea protein: Structural analysis and taste perception insights

This study aimed to prepare and screen salty peptides and elucidate the factors triggering their saltiness properties and saltiness-enhancing effects. Electronic tongue results indicated that samples treated with Alcalase (AJ) exhibited the highest saltiness intensity (5.05 ± 0.11) and greater saltiness-enhancing compared to those treated with Flavourzyme (AF), Neutrase (AZ), and Papain (AM). Peptides identified by LC-MS/MS were docked to the TMC4 receptor, resulting in 23 peptides with good docked results. The key amino acid residues (Thr431, Arg433, Phe440, Phe432, and Ser273) were discovered. The salty peptides WPGFK (633.75 Da), YFDWPGFK (1059.17 Da), and YFDWPGFKT (1160.27 Da) were selected for salt reduction and molecular characterization studies. Electronic tongue results showed that the 0.01 % WPGFK solution matched the saltiness of the 0.24 % NaCl solution and demonstrated superior saltiness-enhancing compared to YFDWPGFK and YFDWPGFKT. Primary sequence analysis of three salty peptides suggested that the WPG amino acid segment might play a crucial role in generating saltiness. Circular dichroism (CD) analysis of the secondary structure indicated that increased random coil and decreased β-turn contents resulted in higher saltiness perception and increased random coil content led to greater saltiness-enhancing ability.

Screening of novel umami peptides with saltiness enhancement effect using molecular docking and structure-activity analysis

In this study, to explore a healthier and safer alternative method for reducing salt intake, new umami peptides were identified from the hydrolysate of Ruditapes philippinarum through structure-activity relationship and molecular docking. The impact of these peptides on enhancing salty taste was examined using a sensory test and an electronic tongue evaluation. The mechanism of salt reduction was investigated through molecular docking. In addition, eight new umami peptides: LEDKVE, DEELNKLK, DLKEKL, LEER, AEKEEEFENT, EQEEYKK, EFDKK, and GEDFDNKLV, extracted from the hydrolysate of Ruditapes philippinarum, were identified, and their taste thresholds ranged from 0.12 to 0.24 mmol/L. When new umami peptides were mixed with 3 g/L of NaCl, the saltiness of NaCl was enhanced. Among the umami peptides studied, LEDKVE had the most significant impact on improving saltiness, achieving a perception of salty taste equivalent to 5 g/L of NaCl in a solution of 3 g/L of NaCl. Molecular docking revealed that the umami peptide interacted with transmembrane channel-like protein 4 (TMC4) through hydrogen bonds, and the key active sites, including Lys568, Trp145, Tyr565, Arg151, and Gln155, potentially played a crucial role in taste perception. This study offers valuable insights into the development of flavorful and nutritious seasonings that can enhance nutritional quality.

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.

Identification of salty peptides from enzymolysis extract of oyster by peptidomics and virtual screening

Salty peptide as an important sodium substitute, which could reduce the risk of cardiovascular disease caused by excessive sodium intake. In this study, novel salty peptides were prepared and identified from enzymolysis extract of oysters by peptitomic identification, virtual screening and solid phase synthesis. Additionally, molecular simulation was used to study the taste mechanism of salty peptides. 316 peptides were identified in the enzymatic hydrolysates of oysters. 6 peptides, selected through virtual screening, were synthesized using solid-phase synthesis, and EK, LFE, LEY and DR were confirmed to possess a pleasing salty taste through electronic tongue evaluation. Molecular docking results indicated that these 4 peptides could enter the binding pocket within the transmembrane channel-like 4 (TMC4) cavity, wherein salt bridges, hydrogen bonds and attractive charges were the main binding forces. This study provides a rapid screening method for salty peptides in sea food products but possibly applied for other sources.

A comprehensive review of plant-derived salt substitutes: Classification, mechanism, and application

The diseases caused by excessive sodium intake derived from NaCl consumption have attracted widespread attention worldwide, and many researchers are committed to finding suitable ways to reduce sodium intake during the dietary process. Salt substitute is considered an effective way to reduce sodium intake by replacing all/part of NaCl in food without reducing the saltiness while minimizing the impact on the taste and acceptability of the food. Plant-derived natural ingredients are generally considered safe and reliable, and extensive research has shown that certain plant extracts or specific components are effective salt substitutes, which can also give food additional health benefits. However, these plant-derived salt substitutes (PSS) have not been systematically recognized by the public and have not been well adopted in the food industry. Therefore, a comprehensive review of PSS, including its material basis, flavor characteristics, and taste mechanism is helpful for a deeper understanding of PSS, accelerating its research and development, and promoting its application.

Advancements in production, assessment, and food applications of salty and saltiness-enhancing peptides: A review

Salt is important for food flavor, but excessive sodium intake leads to adverse health consequences. Thus, salty and saltiness-enhancing peptides are developed for sodium-reduction products. This review elucidates saltiness perception process and analyses correlation between the peptide structure and saltiness-enhancing ability. These peptides interact with taste receptors to produce saltiness perception, including ENaC, TRPV1, and TMC4. This review also outlines preparation, isolation, purification, characterization, screening, and assessment techniques of these peptides and discusses their potential applications. These peptides are from various sources and produced through enzymatic hydrolysis, microbial fermentation, or Millard reaction and then separated, purified, identified, and screened. Sensory evaluation, electronic tongue, bioelectronic tongue, and cell and animal models are the primary saltiness assessment approaches. These peptides can be used in sodium-reduction food products to produce "clean label" items, and the peptides with biological activity can also serve as functional ingredients, making them very promising for food industry.

The complexities of salt taste reception: insights into the role of TMC4 in chloride taste detection

Although salt is an essential substance vital to life, excessive salt intake could cause various health issues. Therefore, new technologies and strategies should be developed to reduce salt intake without compromising taste. However, the underlying physiological mechanisms of salt taste reception is complex and not completely understood. Sodium chloride is a typical salty substance. It is widely believed that only sodium is important for the generation of salty taste. On the other hand, from a psychophysical perspective, the importance of chloride in salty taste has been indicated. Thus, understanding the mechanisms of both sodium- and chloride-tastes generation is necessary to completely comprehended the fundamentals of salt taste reception. However, the mechanism for detecting chloride taste has remained unclear for many years. Recently, we have identified transmembrane channel-like 4 (TMC4) as the first molecule that mediates the reception of chloride taste. TMC4 functions as a voltage-dependent chloride channel and plays an important role in the reception of the chloride taste by detecting chloride ions. In this mini-review, we first introduce the known reception mechanism of salty taste, and then discuss the roles of TMC4 in the salt taste reception. The finding of TMC4 may serve as a basis for developing new technologies and formulating strategies to reduce salt intake without compromising taste.

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.

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.

Advances in flavor peptides with sodium-reducing ability: A review

Condiments (such as sodium chloride and glutamate sodium) cause consumers to ingest too much sodium and may lead to a variety of diseases, thus decreasing their quality of life. Recently, a salt reduction strategy using flavor peptides has been established. However, the development of this strategy has not been well adopted by the food industry. There is an acute need to screen for peptides with salty and umami taste, and to understand their taste characteristic and taste mechanism. This review provides a thorough analysis of the literature on flavor peptides with sodium-reducing ability, involving their preparation, taste characteristic, taste mechanism and applications in the food industry. Flavor peptides come from a wide range of sources and can be sourced abundantly from natural foods. Flavor peptides with salty and umami tastes are mainly composed of umami amino acids. Differences in amino acid sequences, spatial structures and food matrices will cause different tastes in flavor peptides, mostly attributed to the interaction between peptides and taste receptors. In addition to being used in condiments, flavor peptides have also anti-hypertensive, anti-inflammatory and anti-oxidant abilities, offering the potential to be used as functional ingredients, thus making their future in the food industry extremely promising.

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.

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.

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.

Novel salty peptides derived from bovine bone: Identification, taste characteristic, and salt-enhancing mechanism

Excessive sodium intake is a major contributor to the incidence of cardiovascular diseases. The objective of this study was to prepare, isolate, and characterize peptides from bovine bone protein and investigate the salty/salt-enhancing mechanism of peptides. 1032 peptides were identified in the enzymatic hydrolysates of bovine bone protein and were further screened by the composition of amino acid residues and molecular docking analysis. 5 peptides were finally selected for solid-phase synthesis, and KER showed a better salty taste by sensory verification. Moreover, the synergistic effect of KER in NaCl and MSG solution could enhance the salty intensity by 65.26 %. The binding of KER to the salty receptor (TMC4) was driven by hydrogen bonding and electrostatic interactions with a binding energy of -88.0734 kcal/mol. This work may provide a new approach to efficiently screen salty peptides from natural food materials, which were expected as a taste enhancer used in salt-reducing foods.

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.

Exploring of multi-functional umami peptides from Stropharia rugosoannulata: Saltiness-enhancing effect and mechanism, antioxidant activity and potential target sites

Umami peptides enhance flavor and offer potential health benefits. We analyzed the taste-value profiles of five novel umami peptides from Stropharia rugosoannulata using E-tongue, exhibiting significant saltiness characteristics. While the peptides PHEMQ and SEPSHF exhibited higher saltiness, their mixture with salt did not enhance saltiness compared to individual peptides. Surprisingly, SGCVNEL, which was initially weak in saltiness, showed remarkably enhanced saltiness when mixed with salt, possibly due to have strong binding with receptors. Molecular docking elucidated the salt-forming mechanism of TMC4, highlighting the P2-domain and hydrogen bonds' role in the composite structure stability. Evaluation of the antioxidant activity evaluation demonstrated dose-dependent effects primarily through free radical scavenging via the single-electron transfer potential mechanism for SGCVNEL, EPLCNQ, and ESCAPQL. Docking experiments with antioxidant targets revealed varied binding stabilities, indicating diverse antioxidant effects of the peptides. These findings provide valuable insights into the exploration and application of versatile bioactive flavor peptides.

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.

Novel kokumi peptides from yeast extract and their taste mechanism via an in silico study

Yeast extract, a widely utilized natural substance in the food industry and biopharmaceutical field, holds significant potential for flavor enhancement. Kokumi peptides within yeast extracts were isolated through ultrafiltration and gel chromatography, followed by identification using liquid chromatography tandem mass spectrometry (LC-MS/MS). Two peptides, IQGFK and EDFFVR, were identified and synthesized using solid-phase methods based on molecular docking outcomes. Sensory evaluations and electronic tongue analyses conducted with chicken broth solutions revealed taste thresholds of 0.12 mmol L-1 for IQGFK and 0.16 mmol L-1 for EDFFVR, respectively, and both peptides exhibited kokumi properties. Additionally, through molecular dynamics simulations, the binding mechanisms between these peptides and the calcium-sensing receptor (CaSR) were explored. The findings indicated stable binding of both peptides to the receptor. IQGFK primarily interacted through electrostatic interactions, with key binding sites including Asp275, Asn102, Pro274, Trp70, Tyr218, and Ser147. EDFFVR mainly engaged via van der Waals energy and polar solvation free energy, with key binding sites being Asp275, Ile416, Pro274, Arg66, Ala298, and Tyr218. This suggests that both peptides can activate the CaSR, thereby inducing kokumi activity. This study provides a theoretical foundation and reference for the screening and identification of kokumi peptides, successfully uncovering two novel kokumi peptides derived from yeast extract.

Identification novel salt-enhancing peptides from largemouth bass and exploration their action mechanism with transmembrane channel-like 4 (TMC4) by molecular simulation

The purpose of this study was to screen and verify salt-enhancing peptides that can effectively reduce sodium consumption from Largemouth bass myosin through virtual hydrolysis, molecular simulation, and sensory evaluation. The human transmembrane channel-like 4 (TMC4) was constructed using Alphafold2, with 93.3 % of amino acids falling within allowed regions. A total of 19 peptides were predicted through virtual hydrolysis and screening. DAF, QIF, RPAL, and IPVM significantly enhanced the saltiness perception, and QIF exhibited the most pronounced effect in enhancing saltiness (P < 0.05). The residues Ala258, Ser546, Ser603, Phe259, Cys265, Glu539, Lys278 and Ser585 were identified as key binding sites. The TMC4-DAF complex achieved stability after 20, 000 ps, exhibiting an average RMSD value of 0.84 nm. DAF consistently displayed fluctuations at approximately 3.05 nm, and the number of hydrogen bonds varied between 3 and 5. These results suggested that Alphafold2 modelling can be used for predicting salt-enhancing peptides.

Discovery of peptides with saltiness-enhancing effects in enzymatic hydrolyzed Agaricus bisporus protein and evaluation of their salt-reduction property

This study aimed to screen peptides with saltiness-enhancing effects from enzymatic hydrolyzed Agaricus bisporus protein and quantify their salt-reduction. The saltiness evaluation standard curve was first established to evaluate salinity. The peptide fractions (U-1, U-2, and U-3) were obtained from enzymatic hydrolyzed Agaricus bisporus protein by ultrafiltration. Quantitative calculations showed that the U-2 fraction (200-2000 Da) had the strongest saltiness-enhancing effect, and its perceived saltiness in 50 mmol NaCl solution was 60.24 ± 0.10 mmol/L. The peptide sequences were identified by liquid chromatography/mass spectrometry (LC-MS/MS). Results suggested that the potential peptides with saltiness-enhancing effects were umami peptides. Molecular docking with the umami receptor T1R1/T1R3 revealed that the key amino acid residues were Asp82, Glu392, Glu270, and Asp269. Furthermore, peptide YDPNDPEK (976.4138 Da), DDWDEDAPR(1117.4312 Da), and DVPDGPPPE (1058.4668 Da) were synthesized for salt-reduction quantification. 0.4 % peptide YDPNDPEK in NaCl solution was found to have a salt-reduction of 30 %, which provided the basic theory and data for the salt-reduction of peptide in enzymatic hydrolyzed Agaricus bisporus protein.

Identification and virtual screening of novel salty peptides from hydrolysate of tilapia by-product by batch molecular docking

Introduction

Tilapia produces a large number of by-products during processing, which contain potentially flavorful peptides.

Methods

The application of PyRx software enabled batch molecular docking andscreening of 16 potential salty peptides from 189 peptides identified in the enzymaticdigestion of tilapia by-products.

Results

According to sensory analysis, all 16 peptides werepredominantly salty with a threshold of 0.256 - 0.379 mmol/L with some sournessand astringency, among which HLDDALR had the highest salty intensity, followedby VIEPLDIGDDKVR, FPGIPDHL, and DFKSPDDPSRH. I addition, moleculardocking results showed these four core peptides with high salt intensity bound to thesalt receptor TRPV1 mainly via van der Waals interactions, hydrogen bonds, andhydrophobic forces; Arg491, Tyr487, VAL441, and Asp708 were the key sites for thebinding of salty peptides to TRPV1. Therefore, the application of batch moleculardocking using PyRx is effective and economical for the virtual screening of saltypeptides.

Utilization of Yeast Extract as a Flavor Enhancer and Masking Agent in Sodium-Reduced Marinated Shrimp

Deepwater pink shrimp (Parapenaus longirostris) has a significantly high catch yield and is a highly important food source for human nutrition in terms of its nutritional value. The reduction of salt content in seafood products while preserving taste poses a significant challenge. The aim of this study is to reduce the NaCl ratio used in the shrimp marination process by substituting it with KCl and masking the resulting bitterness from KCl using natural flavor enhancers, such as yeast extracts. The marinated shrimp were prepared using 50% KCl instead of 50% NaCl. In order to mask the bitter taste caused by KCl and enhance the flavor, two different types of yeast extracts obtained from Saccharomyces cerevisiae were utilized in the formulation. Nutritional composition, Na and K contents, amino acid composition, color measurement, bacteriological quality, pH changes, and sensory evaluations were conducted to assess the impact of salt reduction and yeast extracts on the sensory, chemical, and physical attributes of the products. L-glutamic acid, L-alanine, L-aspartic acid, L-leucine, L-valine, and L-lysine were found to be higher in samples with Levex Terra yeast extract. Despite a 50% reduction in NaCl content, the addition of yeast extract led to an increase in the umami taste due to the elevation of amino acids present. Yeast extracts can offer a promising solution for enhancing the sensory qualities of seafood products with reduced salt content by conducting more detailed sensory development examinations.

Light-Colored Maillard Peptides: Formation from Reduced Fluorescent Precursors of Browning and Enhancement of Saltiness Perception

The browning formation and taste enhancement of peptides derived from soybean, peanut, and corn were studied in the light-colored Maillard reaction compared with the deep-colored reaction. The fluorescent compounds, as the browning precursors, were accumulated during the early Maillard reaction of peptides and subsequently degraded into dark substances, which resulted in a higher browning degree of deep-colored Maillard peptides (MPs), especially for the MPs derived from corn peptide. However, the addition of l-cysteine in light-colored Maillard reaction reduced the formation of deoxyosones and short-chain reactive α-dicarbonyls, thereby weakening the generation of fluorescent compounds and inhibited the browning of MPs. Synchronously, the peptides were thermally degraded into small peptides and amino acids, which were consumed less during light-colored thermal reaction due to its shorter reaction time at high temperature compared with deep-colored ones, thus contributing to a stronger saltiness perception of light-colored MPs than deep-colored MPs. Besides, the Maillard reaction products derived from soybean and peanut peptides possessed an obvious "kokumi" taste, making them suitable for enhancing the soup flavors.

Identification of novel umami peptides from yeast extract and the mechanism against T1R1/T1R3

Yeast extract was separated by using ultrafiltration, gel filtration chromatography, and preparative high-performance liquid chromatography for analyzing the umami mechanism. 13 kinds of umami peptides were screened out from 73 kinds of peptides which were identified in yeast extract using nanoscale ultra-performance liquid chromatography-tandem mass spectrometry and virtual screening. The umami peptides were found to have a threshold range of 0.07-0.61 mM. DWTDDVEAR exhibited a strong umami taste with a pronounced enhancement effect for monosodium glutamate. Molecular docking studies revealed that specific amino acid residues in the T1R1 subunit, including Arg316, Ser401, and Asp315, played a critical role in the umami perception with these peptides. Overall, the study highlights the potential of natural flavor enhancers and provides insights into the mechanism of umami taste perception.

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.

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.

Prospects and challenges for the application of salty and saltiness-enhancing peptides in low-sodium meat products

A long-term high-sodium diet has been reported to increase the incidence of cardiovascular diseases and other diseases, including osteoporosis, gastric cancer, stomach cancer, and kidney stones. Meat products contain high NaCl content and contribute to approximately 20% of the total sodium intake, so reducing its sodium content has always been the critical focus of industries and researchers. Salty and saltiness-enhancing peptides (SSEP) are a potential salt substitute that exhibits a salt taste or saltiness-enhancing activity. The partial replacement of NaCl by SSEP in low-sodium meat products has been a technological challenge. This review discussed the salt taste transduction mechanism of SSEP. The current studies about preparing SSEP based on different protein sources were summarized. Further, the effects of SSEP combined with other chloride salts, such as KCl and CaCl2, on the sensory properties of meat products were summarized. Finally, the challenges associated with applying the peptide to low-sodium meat products were discussed, focusing on the efficient preparation method and the effect of meat product processing methods and matrices on the efficacy of SSEP.

Preparation of Saltiness-Enhancing Enzymatic Hydrolyzed Pea Protein and Identification of the Functional Small Peptides of Salt Reduction

According to the correlation of saltiness determined by electronic tongue and perceived NaCl concentration, favorable enzymatic hydrolysis parameters were achieved to prepare the saltiness enhancing mixture peptides from pea protein. Six peptide fractions (F1, F2, F3, F4, F5, and F6) were isolated using Sephadex G-10 gel filtration. Among them, fraction F4 (0.1%) exhibited the highest saltiness (5.90 ± 0.03). The amino acid sequences of five main peptides identified by time-of-flight mass spectrometry were Tyr-Trp (367.40 Da), Gly-Glu-His-Glu (470.43 Da), Glu-Arg-Phe-Gly-Pro (604.65 Da), Gly-Ala-Gly-Lys (331.37 Da), and Pro-Gly-Ala-Gly-Asn (414.41 Da). Tyr-Trp (0.01%) in 0.4% NaCl solution had a 20% saltiness-enhancement compared with 0.4% NaCl solution. More salivary aldosterone was secreted after tasting hydrolysate or Tyr-Trp solutions via enzyme-linked immunosorbent assay, reflecting the improvement of human sensitivity to saltiness. Thereby, the saltiness-enhancing effect was confirmed for the small peptides from hydrolyzed pea protein and the main contributor was further identified.

Decoding of the Saltiness Enhancement Taste Peptides from the Yeast Extract and Molecular Docking to the Taste Receptor T1R1/T1R3

The development of saltiness or saltiness enhancement peptides is important to decrease the dietary risk factor of high sodium. Taste peptides in the yeast extract were separated by ultrafiltration and subsequently identified by UPLC-Q-TOF-MS/MS. The 377 identified peptides were placed into the umami receptor T1R1/T1R3. The results showed that eight taste peptides with higher binding energies were screened by molecular virtual docking, and the results revealed that Asp218, Ser276, and Asn150 of T1R1 play key roles in umami docking of peptides. The taste characteristic description and saltiness enhancement effect results suggested that PKLLLLPKP (sourness and umami, 0.18 mM), GGISTGNLN (sourness, 0.59 mM), LVKGGLIP (umami, 0.28 mM), and SSAVK (umami, 0.35 mM) had higher saltiness enhancement effects. The sigmoid curve analysis further confirmed that the taste detection threshold of the GGISTGNLN in the peptide and salt model (157.47 mg/L) was lower than 320.99 mg/L and exhibited a synergistic effect on saltiness perception, whereas SSAVK, PKLLLLPKP, and LVKGGLIP exhibited additive effects on the saltiness perception. This work also corroborated previous research, which indicated that the sourness and umami taste attributes could enhance the saltiness perception.