The review, titled “Enhancing saltiness perception through food structure design: multi-scale mechanisms and strategies,” brings together findings from sensory physiology, food physics, materials science and computational modeling to map how the microscopic and macroscopic organization of food controls the way sodium reaches our taste receptors. The central insight is deceptively simple: saltiness is not determined solely by the total amount of sodium in a product, but by how efficiently that sodium is delivered to taste receptors on the tongue during chewing. Food structure, from the molecular arrangement of proteins and polysaccharides up to the visible organization of emulsions, gels, foams and porous solids, acts as the gatekeeper of that delivery.

At the finest scale, the authors examine the chemistry of sodium ions and their interaction with the saliva and mucus layer that bathes the tongue. Before a sodium ion can activate the epithelial sodium channels responsible for salt taste, it must diffuse through a hydrated matrix, be released from whatever food component binds it, and reach the receptor surface at a sufficiently high local concentration. Binding interactions with proteins such as caseins, with charged polysaccharides, or with lipids can slow that release, while free, unbound sodium in the liquid phase of a food reaches receptors almost immediately. This means two products with identical sodium content can produce markedly different saltiness ratings depending on how strongly the matrix holds on to its ions.

The review then scales up to the mesoscopic level of droplets, particles and networks. Here, the concept of localized salt pockets becomes crucial. Studies summarized in the review show that concentrating salt into heterogeneously distributed compartments—surface coatings, layered inclusions, or dissolved phases within oil-in-water emulsions—can produce bursts of intense saltiness during chewing even when the average sodium concentration is significantly reduced. Human sensory panels evaluating such structurally designed products frequently report equivalent or near-equivalent saltiness compared with conventionally salted controls, because the tongue responds to transient peaks in sodium concentration rather than to a diluted but uniform level. The physics of this strategy relies on controlled phase separation and on engineering which phase of a multiphase food carries the salt.

Moisture and water activity emerge as another powerful lever. Sodium ions migrate with water, and foods with higher water content or with water deliberately redistributed toward the surface release salt more readily into saliva during the first seconds of mastication, when salt perception is at its sharpest. Conversely, dry or tightly bound matrices such as crackers hold sodium in a form that is released slowly and perceived weakly, prompting manufacturers to compensate with more salt. By re-engineering moisture distribution—through humectants, through modified cooking and drying protocols, or through laminated structures that concentrate brine in specific layers—designers can increase apparent saltiness while cutting total sodium.

The review also devotes significant attention to mechanical breakdown behavior, the way a food fractures, melts or erodes in the mouth. Time-resolved sensory techniques such as temporal dominance of sensations show that the perceived intensity of saltiness depends on the rate at new sodium-laden surfaces are exposed during chewing. Soft gels that dissolve quickly can deliver their sodium payload in a brief, high-intensity pulse, whereas brittle structures that shatter into fine particles create many fresh surfaces at once, releasing salt rapidly and boosting the taste signal. Porous aerated structures, common in breads and snacks, provide internal surfaces that saliva can penetrate, effectively pre-dissolving salt before it reaches the receptor field. Matching food breakdown kinetics to the temporal sensitivity of human taste is presented as a design principle in its own right.

Beyond the tongue itself, the authors highlight multisensory and cognitive mechanisms that modulate saltiness. Aroma compounds can enhance perceived saltiness through cross-modal interaction, a phenomenon exploited by adding savory volatiles that trick the brain into expecting more sodium than is physically present. Texture cues also matter: crispness, juiciness and perceived moistness are subconsciously associated with saltiness, and visual expectations of a well-seasoned product can bias ratings before the first bite. Sound contributes as well, with louder, crunchier mastication sounds reported to increase intensity judgments. These psychological pathways offer sodium reduction routes that involve no reformulation of ionic content at all, only a reshaping of the context in which taste is constructed.

Turning mechanisms into strategies, the review organizes practical approaches into families. Surface salting and coatings concentrate sodium where it matters most, at the interface with saliva. Emulsion and gel engineering shifts salt into the continuous aqueous phase or into dispersed droplets that rupture during chewing. Encapsulation technologies, including liposomes and hydrogel beads, can protect sodium from premature interactions and release it on demand under mechanical shear. Porosity engineering uses aeration and freeze-drying to multiply surface area. Substitution strategies, replacing part of the sodium chloride with potassium chloride or other salts, are made more palatable when combined with structural delivery, because bitterness from potassium can be masked by optimized release timing and aroma pairing. The authors stress that no single tactic suffices; the most effective sodium reduction combines several structural approaches tuned to a specific product matrix.

The review does not shy away from the obstacles ahead. Sensory results from model systems do not always translate to complex real foods, where heat treatment, freezing, storage and ingredient interactions can reorganize structure over time. Manufacturing scale-up, cost, labeling and consumer acceptance all impose constraints, and regulatory ambiguity around novel salt substitutes complicates reformulation. Measuring sodium release kinetics in realistic chewing conditions requires sophisticated in vitro and in vivo methods, from dynamic saliva simulation to real-time monitoring in human subjects, and the field still lacks standardized protocols for comparing across studies. Standardization, the authors suggest, would accelerate progress by making multi-scale data comparable across laboratories.

Looking forward, the authors identify computational structure design as an emerging frontier. Machine learning models trained on compositional, structural and temporal sensory datasets could one day predict saltiness trajectories for new formulations before any panel is convened, shortening development cycles for reduced-sodium products. Coupled with high-resolution imaging of food microstructure and physics-based simulations of salivary release, such tools would turn sodium reduction from an empirical craft into a quantitative engineering discipline. The public health stakes are considerable: even a modest population-wide reduction in sodium intake is projected to prevent large numbers of hypertension-related deaths annually. If the tongue can be satisfied by smarter structure rather than more salt, the review concludes, the food industry gains a path to healthier products that consumers actually want to eat—an outcome in which physics, physiology and flavor converge on the same side.

Subject of Research: Food structure design to enhance saltiness perception for sodium reduction

Article Title: Enhancing saltiness perception through food structure design: multi-scale mechanisms and strategies

Article References: Meng, W., & Miao, S. (2026). Enhancing saltiness perception through food structure design: multi-scale mechanisms and strategies. npj Science of Food. https://doi.org/10.1038/s41538-026-01123-9

Image Credits: AI Generated

DOI: 10.1038/s41538-026-01123-9

Keywords: salt reduction, saltiness perception, food structure, sodium, taste receptors, food science, sensory science, emulsions, food texture, food microstructure, public health, npj Science of Food

The review, conducted by Margarida Bica, Jessica Renzella, Asha Kaur and Mike Rayner of the University of Oxford, drew on both peer-reviewed literature and the often-overlooked grey literature of government regulations, technical manuals and policy documents. The researchers systematically searched for nutrient profile models specifically developed or applied to front-of-pack nutrition labelling systems, characterising each model according to the type of labelling scheme it supported, the nutrients and food components it restricted or encouraged, and the evidence of its scientific validation. The scope matters, the authors argue, because the sheer proliferation of NPMs now poses a practical challenge for policymakers: with dozens of options available, choosing an appropriate model for a national labelling policy has become a non-trivial scientific and political decision.

The taxonomy that emerged from the analysis mirrors the main families of front-of-pack labelling in use today. Fifteen of the 42 identified models were developed for warning-label schemes, the approach pioneered in Chile and now dominant across much of Latin America, in which products exceeding thresholds for nutrients of concern carry prominent black octagons declaring them high in sugar, sodium or saturated fat. Eleven models underpinned nutrient-specific systems, including the traffic-light labelling familiar to British shoppers, which displays colour-coded indicators for individual nutrients. Another 11 models supported health endorsement schemes, such as the Nordic Keyhole or Singapore’s Healthier Choice Symbol, which positively certify foods deemed healthier choices. Four models drove summary scores, exemplified by France’s Nutri-Score and Australia’s Health Star Rating, which condense a food’s overall nutritional quality into a single graded mark. One model served other system types.

Beneath this structural variety, the review found striking common ground on which nutrients matter most. Every one of the 42 models limited the content of sugar, reflecting the strength of the scientific evidence linking excess sugar intake to obesity, type 2 diabetes and dental disease. The vast majority also placed restrictions on sodium and saturated fat, the two other nutrients most consistently associated with non-communicable disease burden. This convergence suggests that, despite institutional and regional differences, the underlying nutritional science has produced a broadly shared view of which dietary components should trigger concern on the front of a package. Sweeteners, energy density, protein, fibre, fruit and vegetable content appeared in more variable combinations across models, reflecting differing philosophies about whether labels should simply flag harmful nutrients or also reward beneficial ones.

Where the consensus frays is in the details of implementation. Thresholds for what counts as high in sugar differ between models; some assess nutrients per 100 grams while others evaluate them per serving or as a proportion of total energy; category-specific rules treat staples such as cheese, oils and beverages differently across schemes. The review documents this heterogeneity in granular detail, showing that two products judged unhealthy under one national scheme may pass cleanly under another. For multinational food manufacturers, this patchwork creates compliance complexity and, critics argue, opportunities to formulate products to game particular algorithms. For policymakers in countries drafting their first labelling laws, the absence of a single validated standard complicates decisions that industry lobbyists are often eager to influence.

Validation emerged as another significant gap. The review assessed whether models had demonstrated convergent validity, meaning agreement with other established measures of nutritional quality, and criterion validity, meaning the ability to predict health-relevant outcomes. Convergent validity was demonstrated for nine of the 42 models, while criterion validity was shown for only three. In other words, the scientific evidence underpinning most front-of-pack labelling algorithms remains thin relative to their policy importance. The authors note that this imbalance reinforces the need for greater regional guidance and alignment, so that new labelling programmes can build on models whose performance has been rigorously tested rather than reinventing criteria from scratch under political pressure.

The policy stakes are considerable. Diet-related non-communicable diseases, including cardiovascular disease, diabetes and several cancers, are among the leading causes of death globally, and governments increasingly view front-of-pack labels as a fast, low-cost intervention that shifts both consumer choice and industry reformulation. Chile’s warning-label law, implemented in stages since 2016, has been associated with reductions in purchases of sugary drinks and prompted widespread product reformulation across the region. The Pan American Health Organization’s nutrient profile model has served as a regional benchmark, while the World Health Organization has issued guiding principles and framework manuals to support member states. The European Union is weighing a harmonised mandatory front-of-pack label, a debate in which the choice between Nutri-Score-style summary scores and other approaches has become intensely contested among member states, scientists and industry groups.

The review also situates nutrient profiling within a broader scientific conversation about what food labels should measure. A growing body of research argues that nutrient-based models, however well calibrated, fail to capture the degree of industrial processing, exemplified by the NOVA classification of ultra-processed foods, which has been independently associated with adverse health outcomes in large cohort studies. Recent work has explored modifying established algorithms, such as Australia’s Health Star Rating, to account for ultra-processing, and examining the complementarity between updated Nutri-Score criteria and NOVA categories. The Oxford review does not resolve this debate, but its systematic inventory provides the evidentiary scaffolding for it, documenting precisely which models exist, what they measure and where their validation evidence stands.

Methodologically, the review followed established systematic review practice, including structured searches across peer-reviewed databases and targeted collection of grey-literature policy documents from national ministries, regional health bodies and regulatory agencies across the Americas, Europe, Asia, Africa and the Eastern Mediterranean. The authors screened studies collaboratively, analysed model characteristics in detail and reported their findings with extensive supplementary tables. The inclusion of grey literature proved essential: many of the 42 models, particularly those embedded in national regulations from Chile and Mexico to Kenya, Samoa and the Gulf states, exist primarily in legal texts and technical manuals rather than scientific journals. Without such searches, the true global diversity of nutrient profiling for labelling would be substantially underestimated.

The review’s central message is ultimately one of opportunity tempered by fragmentation. Front-of-pack nutrition labelling has matured from a handful of voluntary schemes into a global policy movement with real evidence of impact, and the raw material for that movement, a library of 42 nutrient profile models, is now catalogued and characterised. But the heterogeneity the authors document suggests that the field has not yet converged on what constitutes the most appropriate model for labelling purposes, and that validation evidence lags behind deployment. Greater regional guidance and alignment, the authors conclude, would help countries adopt models with demonstrated performance, reduce industry gaming of inconsistent thresholds, and move the world’s food packages toward labels that are not only eye-catching but scientifically defensible. As more governments prepare to legislate, the choice of algorithm beneath the label may prove as consequential as the label itself.

Subject of Research: Nutrient profile models developed and used for front-of-pack nutrition labelling systems to classify foods and support policies against diet-related non-communicable diseases.

Article Title: Systematic review of nutrient profile models for front-of-pack nutrition labelling

Article References: Bica, M., Renzella, J., Kaur, A., & Rayner, M. (2026). Systematic review of nutrient profile models for front-of-pack nutrition labelling. Nature Food. https://doi.org/10.1038/s43016-026-01414-0

Image Credits: AI Generated

DOI: 10.1038/s43016-026-01414-0

Keywords: nutrient profile models, front-of-pack nutrition labelling, food policy, non-communicable diseases, sugar, sodium, saturated fat, warning labels, Nutri-Score, traffic-light labelling, systematic review, public health nutrition