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

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.

Odor-induced saltiness enhancement of volatile compounds screened from duck stewed with chili pepper

Odor-induced saltiness enhancement (OISE) is thought to be a unique salt reduction technique which capitalizes on olfactory-gustatory interaction. Volatile compounds of stewed duck obtained from orthonasal (no-treatment) and retronasal (saliva-treatment) pathways and their capacity on OISE were analyzed by GC-O-MS and molecular simulation in order to ascertain the role of odors in duck stewed with chili pepper on saltiness enhancement. Totally 17 unique volatile compounds were identified in retronasal pathways. Eight salty-congruent volatile compounds were screened from the stewed duck, one of which being E-2-decenal, specific to retronasal volatile compounds following oral enzymatic digestion. These volatile compounds' OISE in NaCl solution was confirmed, and the retronasal pathway effect outweighed the orthonasal one. Molecular docking revealed that volatile compounds interacted with saltiness receptors through hydrogen bonding and hydrophobic force, which may be responsible for its enhanced saltiness. These findings suggest that olfactory pathways and specific odors might simultaneously mediate OISE.

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.

Cleaner preparation of N-lauroyl theanine with taste-enhancing properties and deciphering its taste-presenting mechanism

With the improvement of people's living standards and health awareness, reducing salt, sugar, and fat is gradually becoming the mainstream trend. In this work, we delved into the development of an innovative taste enhancer, N-lauroyl theanine (NLT), and its taste presentation mechanism. NLT was synthesized in the aqueous phase by enzyme-catalyzed and direct-heating methods using food-grade enzymes in yields of up to 64.33 % and 49.11 %, respectively. Sensory evaluation and molecular docking techniques revealed the potential of NLT to enhance salty, umami, sweet, and kokumi taste sensations and its taste presentation mechanism. Results revealed significant taste enhancement of saltiness, umami, sweetness, and kokumi and prolonged their duration in the oral cavity by 0.25-1 mg/L NLT. Molecular docking analyses showed that NLT had a strong binding affinity for a variety of taste receptors. These findings highlight the potential of NLT as a potent taste enhancer for the development of healthier salt/sugar-reduced foods.

Application of multiple dynamic sensory techniques to N-lauroyl amino acids: Exposing the relationship between taste-enhancing properties and chemical structure

This study investigated the taste enhancing effects of N-lauroyl amino acids, including N-lauroyl-phenylalanine, N-lauroyl-tryptophan and N-lauroyl-tyrosine. Sensory results obtained through TDS, TCATA, and TI assessments indicated that all N-Lau-AAs significantly increased the umami intensity and duration of solutions such as simulated chicken broth. Moreover, these compounds masked bitter taste, with LTR showing the most pronounced reduction of bitterness. LP had the effect of enhancing saltiness, whereas LTR and LTY diminished saltiness. Structural analysis revealed a correlation between the chemical structure of N-Lau-AAs and their sensory properties. The presence of carbon‑carbon double bond (CC) was positively correlated with umami intensity and negatively correlated with bitter and salty parameters. Phenolic hydroxyl groups (OH) were negatively correlated with umami intensity and positively correlated with a decrease in bitterness intensity and duration. Overall, this study provides valuable insights into the taste enhancement potential of N-Lau-AAs as taste enhancers in the food industry.

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.

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.

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.

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.

Taste-Active Peptides from Triple-Enzymatically Hydrolyzed Straw Mushroom Proteins Enhance Salty Taste: An Elucidation of Their Effect on the T1R1/T1R3 Taste Receptor via Molecular Docking

The objective of our study was to analyze and identify enzymatic peptides from straw mushrooms that can enhance salty taste with the aim of developing saltiness enhancement peptides to reduce salt intake and promote dietary health. We isolated taste-related peptides from the straw mushroom extract using ultrafiltration and identified them using UPLC-Q-TOF-MS/MS. The study found that the ultrafiltration fraction (500-2000 Da) of straw mushroom peptides had a saltiness enhancement effect, as revealed via subsequent E-tongue and sensory analyses. The ultrafiltration fractions (500-2000 Da) were found to contain 220 peptides, which were identified through UPLC-Q-TOF-MS/MS analysis. The interaction of these peptides with the T1R1/T1R3 receptor was also assessed. The investigation highlighted the significant involvement of Asp223, Gln243, Leu232, Asp251, and Pro254 in binding peptides from triple-enzymatically hydrolyzed straw mushrooms to T1R1/T1R3. Based on the binding energy and active site analysis, three peptides were selected for synthesis: DFNALPFK (-9.2 kcal/mol), YNEDNGIVK (-8.8 kcal/mol), and VPGGQEIKDR (-8.9 kcal/mol). Importantly, 3.2 mmol of VPGGQEIKDR increased the saltiness level of a 0.05% NaCl solution to that of a 0.15% NaCl solution. Additionally, the addition of 0.8 mmol of YNEDNGIVK to a 0.05% NaCl solution resulted in the same level of saltiness as a 0.1% NaCl solution.