Multiple emulsions are also being investigated as a way to maintain salt taste in sodium- and fat-reduced emulsion products. These emulsions consist of water droplets dispersed in fat droplets that are then dispersed in another outer layer of water that contains salt. The inner layer of water dispersed in the fat droplets can be sodium-free and can replace some of the volume of the product, requiring less of the outer, salted aqueous phase (Figure 3-7). As a result, consumers of these products will continue to enjoy the salt taste of the outer aqueous phase while consuming less total sodium.3
It is possible that the crystal structure of sea salt may be responsible for its pleasing taste profile when used on the surface of foods (Kilcast, 2007). Sea salt usually contains minerals in addition to sodium that impart a variety of tastes that may be desirable in some cases, but may also impart bitter aftertastes. While unsubstantiated reports from trade journals suggest that sea salt may contain as little as 41 percent sodium chloride (Pszczola, 2007), sodium chloride is the main component of most sea salt and thus its composition is similar to table salt.
One approach to reducing salt in the food system would be the development of salt substitutes with the same sensory properties as salt but without the sodium—a sort of aspartame or sucralose but for salt. Alternatively, one might develop a salt taste enhancer, a compound that magnifies the taste of low levels of salt. Adequate substitutes and enhancers for many uses do not yet exist, but one way to attempt to identify such molecules is to use the salt taste receptor to assay for such effects. Unfortunately, the molecular and cellular mechanisms underlying salt taste perception are not fully understood, and this represents a major gap in both our understanding and our ability to efficiently search for salt substitutes and enhancers.
The hypothesized specificity of the salt taste mechanism makes the existence of a true salt taste substitute unlikely, although not impossible. Thus, this differs in principle from a sweet taste, where the receptor mechanisms are more easily mimicked by other molecules; as a consequence, there exist many alternative sweeteners (Beauchamp and Stein, 2008). Many of the alternative sweeteners now used were discovered serendipitously, but no non-sodium, primarily salty-tasting molecule has ever been identified, with perhaps the single exception of potassium chloride.