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Excessive salt intake, primarily from sodium chloride prevalent in modern food processing, poses a significant public health risk associated with hypertension, cardiovascular diseases and stroke. Researchers worldwide are exploring approaches to reduce salt consumption without compromising food flavor. One promising method is to enhance salty taste perception using multisensory synergies, leveraging gustatory, olfactory, auditory, visual, tactile and trigeminal senses to decrease salt intake while preserving food taste. This review provides a comprehensive overview of salt usage in foods, mechanisms of salty taste perception and evaluation methods for saltiness. Various strategies for reducing salt consumption while maintaining food flavor are examined, with existing salt reduction methods’ advantages and limitations being critically analyzed. A particular emphasis is placed on exploring the mechanisms and potential of multisensory synergy in salt reduction. Taste interactions, olfactory cues, auditory stimulation, visual appearance and tactile sensations in enhancing saltiness perception are discussed, offering insights into developing nutritious, appealing low-sodium foods. Furthermore, challenges in current research are highlighted, and future directions for effective salt reduction strategies to promote public health are proposed. This review aims to establish a scientific foundation for creating healthier, flavorful low-sodium food options that meet consumer preferences and wellness needs.

The variety of taste sensations, including sweet, umami, bitter, sour, and salty, arises from diverse taste cells, each of which expresses specific taste sensor molecules and associated components for downstream signal transduction cascades. Recent years have witnessed major advances in our understanding of the molecular mechanisms underlying transduction of basic tastes in taste buds, including the identification of the bona fide sour sensor H+ channel OTOP1, and elucidation of transduction of the amiloride-sensitive component of salty taste (the taste of sodium) and the TAS1R-independent component of sweet taste (the taste of sugar). Studies have also discovered an unconventional chemical synapse termed “channel synapse” which employs an action potential-activated CALHM1/3 ion channel instead of exocytosis of synaptic vesicles as the conduit for neurotransmitter release that links taste cells to afferent neurons. New images of the channel synapse and determinations of the structures of CALHM channels have provided structural and functional insights into this unique synapse. In this review, we discuss the current view of taste transduction and neurotransmission with emphasis on recent advances in the field.

The mammalian tongue contains gustatory receptors tuned to basic taste types, providing an evolutionarily old hedonic compass for what and what not to ingest. Although representation of these distinct taste types is a defining feature of primary gustatory cortex in other animals, their identification has remained elusive in humans, leaving the demarcation of human gustatory cortex unclear. Here we used distributed multivoxel activity patterns to identify regions with patterns of activity differentially sensitive to sweet, salty, bitter, and sour taste qualities. These were found in the insula and overlying operculum, with regions in the anterior and middle insula discriminating all tastes and representing their combinatorial coding. These findings replicated at super-high 7 T field strength using different compounds of sweet and bitter taste types, suggesting taste sensation specificity rather than chemical or receptor specificity. Our results provide evidence of the human gustatory cortex in the insula. Previous research shows how taste types are represented across regions of the brain in non-human animals. Here, the authors examine how four basic tastes are represented in the human brain, showing evidence of the human gustatory cortex in the insula.

“Salty taste” sensation is evoked when sodium and chloride ions are present together in the oral cavity. The presence of an epithelial cation channel that receives Na+ has previously been reported. However, no molecular entity involving Cl− receptors has been elucidated. We report the strong expression of transmembrane channel-like 4 (TMC4) in the circumvallate and foliate papillae projected to the glossopharyngeal nerve, mediating a high-concentration of NaCl. Electrophysiological analysis using HEK293T cells revealed that TMC4 was a voltage-dependent Cl− channel and the consequent currents were completely inhibited by NPPB, an anion channel blocker. TMC4 allowed permeation of organic anions including gluconate, but their current amplitudes at positive potentials were less than that of Cl−. Tmc4-deficient mice showed significantly weaker glossopharyngeal nerve response to high-concentration of NaCl than the wild-type littermates. These results indicated that TMC4 is a novel chloride channel that responds to high-concentration of NaCl.

Taste is a sensory modality crucial for nutrition and survival, since it allows the discrimination between healthy foods and toxic substances thanks to five tastes, i.e., sweet, bitter, umami, salty, and sour, associated with distinct nutritional or physiological needs. Today, taste prediction plays a key role in several fields, e.g., medical, industrial, or pharmaceutical, but the complexity of the taste perception process, its multidisciplinary nature, and the high number of potentially relevant players and features at the basis of the taste sensation make taste prediction a very complex task. In this context, the emerging capabilities of machine learning have provided fruitful insights in this field of research, allowing to consider and integrate a very large number of variables and identifying hidden correlations underlying the perception of a particular taste. This review aims at summarizing the latest advances in taste prediction, analyzing available food-related databases and taste prediction tools developed in recent years.

Previous studies have shown that the conceptual representation of food involves brain regions associated with taste perception. The specificity of this response, however, is unknown. Does viewing pictures of food produce a general, nonspecific response in taste-sensitive regions of the brain? Or is the response specific for how a particular food tastes? Building on recent findings that specific tastes can be decoded from taste-sensitive regions of insular cortex, we asked whether viewing pictures of foods associated with a specific taste (e.g., sweet, salty, and sour) can also be decoded from these same regions, and if so, are the patterns of neural activity elicited by the pictures and their associated tastes similar? Using ultrahigh-resolution functional magnetic resonance imaging at high magnetic field strength (7-Tesla), we were able to decode specific tastes delivered during scanning, as well as the specific taste category associated with food pictures within the dorsal mid-insula, a primary taste responsive region of brain. Thus, merely viewing food pictures triggers an automatic retrieval of specific taste quality information associated with the depicted foods, within gustatory cortex. However, the patterns of activity elicited by pictures and their associated tastes were unrelated, thus suggesting a clear neural distinction between inferred and directly experienced sensory events. These data show how higher-order inferences derived from stimuli in one modality (i.e., vision) can be represented in brain regions typically thought to represent only low-level information about a different modality (i.e., taste).

The vertebrate sense of taste allows rapid assessment of the nutritional quality and potential presence of harmful substances prior to ingestion. Among the five basic taste qualities, salty, sour, sweet, umami, and bitter, bitterness is associated with the presence of putative toxic substances and elicits rejection behaviors in a wide range of animals including humans. However, not all bitter substances are harmful, some are thought to be health-beneficial and nutritious. Among those compound classes that elicit a bitter taste although being non-toxic and partly even essential for humans are bitter peptides and l -amino acids. Using functional heterologous expression assays, we observed that the 5 dominant human bitter taste receptors responsive to bitter peptides and amino acids are activated by bile acids, which are notorious for their extreme bitterness. We further demonstrate that the cross-reactivity of bitter taste receptors for these two different compound classes is evolutionary conserved and can be traced back to the amphibian lineage. Moreover, we show that the cross-detection by some receptors relies on “structural mimicry” between the very bitter peptide l -Trp-Trp-Trp and bile acids, whereas other receptors exhibit a phylogenetic conservation of this trait. As some bile acid-sensitive bitter taste receptor genes fulfill dual-roles in gustatory and non-gustatory systems, we suggest that the phylogenetic conservation of the rather surprising cross-detection of the two substance classes could rely on a gene-sharing-like mechanism in which the non-gustatory function accounts for the bitter taste response to amino acids and peptides.

The purpose of this study was to determine the influence of age and sex on the taste functions of healthy Taiwanese. Subjects were divided into groups based on their sex and age: 20-39 years, 40-59 years, or [greater than or equal to] 60 years. We evaluated the taste functions of subjects using the whole mouth suprathreshold taste test and the taste quad test. For the whole-mouth test, subjects were instructed to sip and swish sweet, sour, salty, and bitter solutions, each at 5 different suprathreshold concentrations. Each subject was required to indicate the taste quality, and to rate the intensity and unpleasantness/pleasantness of each taste of the solutions. For the quad test, the 4 quadrants of the tongue surface were tested by applying a drop of one concentration of sweet, sour, salty, or bitter solutions 6 times. Subjects then indicated the taste quality and rated the intensity of the solution. We found that in the whole mouth test, the total correct identification score dropped with age, but the ability to identify sweet and salty qualities was not affected by age. No differences were found between males and females, except women scored better than men for sweetness in the 40-59 years age group. The intensity rating scores were higher in the 20-39 years age group, regardless of sex. With regard to the pleasantness of tastants, female subjects in the 20-39 years age group found sweet solution more pleasant than the older subjects did. In the quad test, the total correct identification score decreased with age, but there were no differences between males and females. Thus, our findings showed that both age and sex affected the taste functions of healthy Taiwanese to some extent, and differences were dependent on tongue region and taste quality.

Increasing consumer demand for healthier and tastier food options has spurred interest in identifying novel salty-enhancing peptides. This study aimed to extract novel salty-enhancing peptides from the collagen of sea cucumber. The model of the transmembrane channel-like 4 (TMC4) salt taste receptor was constructed by AlphaFold2 de novo modeling, and the interaction between peptides and salt taste receptor was studied by molecular dynamics (MD) simulation. The results revealed that 99.4% of amino acid residues in the Ramachandran Plot of the TMC4 model resided within the allowed region, thereby substantiating the rationality of the model. The molecular docking results indicated that Gln 279, Glu 92, and Lys 278 may be the key amino acids binding to the TMC4 receptor. The CSRH and KDINNRF showed significant enhancement in saltiness compared to the control group (2.62 ± 0.04), with saltiness values of 3.01 ± 0.00 and 2.86 ± 0.04, respectively. In addition, MD simulation results showed that TMC4 saltiness receptors formed stable RMSD and Rg with salty-enhancing peptides at 0–25 ns simulation time. This study verified that CSRH and KDINNRF are effective salty-enhancing peptides, and also provided a theoretical basis for the discovery of new salty-enhancing peptide resources in marine organisms.

Salty taste is an important sensory attribute in many foods, which stimulates the appetite. But high-salt diets bring many health risks, and salty alternatives should be explored to solve this problem. The salt-reducing agents may impart new odors in food. Therefore, the research should focus on developing a novel agent, which would replace the salt without affecting the taste of the food. Generally, some yeast extracts taste salty and can be used for replacing salts in foods without imparting any additional odor. In this study, we fractionated salty peptides from FA31 (Angel Yeast) by ultrafiltration, gel permeation chromatography, preparative liquid chromatography (pre-HPLC), with the combination of sensory evaluation, and the peptide sequence was identified by ESI-Q-TOF LC/MS as Asp-Asp, Glu-Asp, Asp-Asp-Asp, Ser-Pro-Glu, and Phe-Ile.Graphic abstract