Quantitative proteomics and SWATH-MS to elucidate peri-receptor mechanisms in human salt taste sensitivity

Research Progress in Saltiness Perception and Salty Substitutes

Salty taste in foods is a key sensory attribute for appetite enhancement, however, consumption of a high salt diet is associated with a high risk of hypertension, stroke, and heart diseases. To address this issue, the World Health Organization (WHO) has recommended reducing the global per capita salt consumption by 30% by 2025, with adults optimally consuming less than 5 g/day of salt. Therefore, the search for new salty substitutes to reduce salt intake in foods has become a research hotspot. Despite the ongoing endeavors of global research, multiple studies have focused on the application of a single category of salty alternatives or food processing quality (such as preservative effects and process characteristics), and there is still little comprehensive evaluation of these alternatives in terms of nutritional value, health impact, and consumer acceptance in the literature. This review will first outline the urgency of global salt reduction, followed by thorough discussion of salty substitutes and associated mechanisms from the perspective of human salty taste perception. Second, the present review will explore the potential application of salty substitutes and highlight the interaction between taste and odor in foods. Additionally, the potential impacts of salty substitutes on human health will be discussed. The present review will provide a scientific basis for the development of low salt products by food industry.

Decoding of the saltiness enhancement taste peptides from Jinhua ham and its molecular mechanism of interaction with ENaC/TMC4 receptors

This study focused on unlocking the potential of Jinhua ham-derived peptides (JHP) for enhancing saltiness. JHP (<3 kDa) was obtained through ultrafiltration and desalting, reducing the salt content by 96 %. Four peptide fractions (JHP-P1/P2/P3/P4) were isolated using Sephadex G-25 gel filtration and anion-exchange chromatography. Sensory evaluation and electronic tongue analysis revealed that JHP-P2 (0.5 mg/mL) exhibited the highest saltiness which could replace four-fold NaCl salinity. Three peptides (DL, FMSALF, and HVRRK) identified by UPLC-QTOF-MS/MS were simulated with salty taste receptors ENaC/TMC4. Results indicated that Ser84 and Phe89 of ENaC and Asn404 and Lys567 of TMC4 are crucial for peptide docking related to salty taste. Molecular dynamics simulations showed that the three peptides bind to the TMC4 and ENaC through van der Waals forces, electrostatic interactions, and hydrogen bonds. These findings establish a robust theoretical foundation for salt reduction strategies and provide novel insights into the potential applications of Jinhua ham.

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

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

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.

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.

Odor and taste characteristics, transduction mechanism, and perceptual interaction in fermented foods: a review

Fermentation is a critical technological process for flavor development in fermented foods. The combination of odor and taste, known as flavor, is crucial in enhancing people's perception and psychology toward fermented foods, thereby increasing their acceptance among consumers. This review summarized the determination and key flavor compound screening methods in fermented foods and analyzed the flavor perception, perceptual interactions, and evaluation methods. The flavor compounds in fermented foods could be separated, purified, and identified by instrument techniques, and a molecular sensory science approach could identify the key flavor compounds. How flavor compounds bind to their respective receptors determines flavor perception, which is influenced by their perceptual interactions, including odor-odor, taste-taste, and odor-taste. Evaluation methods of flavor perception mainly include human sensory evaluation, electronic sensors and biosensors, and neuroimaging techniques. Among them, the biosensor-based evaluation methods could facilitate the investigation of the flavor transduction mechanism and the neuroimaging technique could explain the brain's signals that relate to the perception of flavor and how they compare to signals from other senses. This review aims to elucidate the flavor profile of fermented foods and highlight the significance of comprehending the interactions between various flavor compounds, thus improving the healthiness and sensory attributes.

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

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

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.

A secret of salivary secretions: Multimodal effect of saliva in sensory perception of food

Saliva plays multifunctional roles in oral cavity. Even though its importance for the maintenance of oral health has long been established, the role of saliva in food perception has attracted increasing attention in recent years. We encourage researchers to discover the peculiarity of this biological fluid and aim to combine the data concerning all aspects of the saliva influence on the sensory perception of food. This review presents saliva as a unique material, which modulates food perception due to constant presence of saliva in the mouth and thanks to its composition. Therefore, we highlight the salivary components that contribute to these effects. Moreover, this review is an attempt to structure the effects of saliva on perception of different food categories, where the mechanisms of salivary impact in perception of liquid, semi-solid, and solid foods are revealed. Finally, we emphasize that the large inter-individual variability in salivary composition and secretion appear to contribute to the fact that everyone experiences food in their own way. Therefore, the design of the sensory studies should consider the properties of volunteers' saliva and also carefully monitor the experimental conditions that affect salivary composition and flow rate.

The association between changes of gustatory function and changes of salivary parameters: A pilot study

OBJECTIVE

The aim of the pilot study was to explore which of the salivary parameters best reflects improvement or deterioration of taste function.

METHODS

A total of 14 patients were included. Taste ability was measured using taste strips and patients rated their symptom strength using visual analogue scales. Salivary parameters (flow rate, total proteins, proteolysis, catalase, total anti-oxidative capacity [TAC], carbonic anhydrase VI [caVI], and pH) were determined and the Beck Depression Inventory (BDI) was administered. All these parameters were measured twice with a one-year interval to acquire the changes of data.

RESULTS

Patients with decreased taste function exhibited a decrease in salivary proteolysis and caVI, and an increase in salivary total protein. Patients with increased taste function also showed an increase in salivary total protein. Δ Salivary flow rate was negatively correlated with Δ taste strip scores. Δ Salivary pH was significantly lower in patients with increased taste function compared to patients with decreased taste function. Δ BDI was positively correlated with both Δ symptoms ratings. Across all patients, symptom ratings decreased while salivary total protein increased; salivary flow rate, proteolysis and caVI decreased significantly compared with baseline.

CONCLUSIONS

The present longitudinal results suggest that changes of both taste function and taste complaints were accompanied by changes in salivary parameters, indicating that salivary parameters have the potential to be useful in the diagnosis of patients with qualitative taste disorders.

Does ENaC Work as Sodium Taste Receptor in Humans?

Taste reception is fundamental for the proper selection of food and beverages. Among the several chemicals recognized by the human taste system, sodium ions (Na⁺) are of particular relevance. Na⁺ represents the main extracellular cation and is a key factor in many physiological processes. Na⁺ elicits a specific sensation, called salty taste, and low-medium concentrations of table salt (NaCl, the common sodium-containing chemical we use to season foods) are perceived as pleasant and appetitive. How we detect this cation in foodstuffs is scarcely understood. In animal models, such as the mouse and the rat, the epithelial sodium channel (ENaC) has been proposed as a key protein for recognizing Na⁺ and for mediating preference responses to low-medium salt concentrations. Here, I will review our current understanding regarding the possible involvement of ENaC in the detection of food Na⁺ by the human taste system.

Mass spectrometry-based metabolomics of volatiles as a new tool for understanding aroma and flavour chemistry in processed food products

BACKGROUND

When foods are processed or cooked, many chemical reactions occur involving a wide range of metabolites including sugars, amino acids and lipids. These chemical processes often lead to the formation of volatile aroma compounds that can make food tastier or may introduce off-flavours. Metabolomics tools are only now being used to study the formation of these flavour compounds in order to understand better the beneficial and less beneficial aspects of food processing.

AIM OF REVIEW

To provide a critical overview of the diverse MS-based studies carried out in recent years in food metabolomics and to review some biochemical properties and flavour characteristics of the different groups of aroma-related metabolites. A description of volatiles from processed foods, and their relevant chemical and sensorial characteristics is provided. In addition, this review also summarizes the formation of the flavour compounds from their precursors, and the interconnections between Maillard reactions and the amino acid, lipid, and carbohydrate degradation pathways.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides new insights into processed ingredients and describes how metabolomics will help to enable us to produce, preserve, design and distribute higher-quality foods for health promotion and better flavour.

Saliva and Flavor Perception: Perspectives

This paper reports the main trends and perspectives related to the current understanding of the relationships between saliva and flavor perception. Saliva is a key factor in flavor perception and controls the transport of flavor molecules to their receptors, their adsorption onto the mouth surfaces (i.e., oral mucosa), their metabolism by enzymatic modification, and the friction force in the oral cavity. The proteins in free saliva or in the mucosal pellicle contribute to flavor perception by interacting with or metabolizing flavor compounds. Most of these reactions were observed when using fresh whole saliva; however, they were absent or less frequently observed when using artificial saliva or depleted/frozen whole saliva. There is a need to better understand the role of protein aggregates in flavor perception. Within humans, there is great interindividual variation in salivary composition, which has been related to differences in flavor perception. However, the relative role of salivary proteins and the microbiota should be deeply investigated together with the impact of their composition on individual perception during life. Finally, future results must also consider cross-modal interactions at the brain level.