When the term salt is used in reformulation literature it is specifically sodium chloride – common table salt – which is being referred to. Consumption of sodium has been linked with a range of cardiovascular health risks, notably hypertension and stroke.
There are a number of approaches to reducing the amount of sodium chloride in food. First, simply reduce the salt content and allow the product to taste less salty. Alternatively, a sodium-free replacement can be used or a salt-enhancing ingredient added.
As salt not only serves to flavour a product, other impacts on the product related to shelf-life and stability, have to be considered. Salt is used, for instance, to support microbiological stability and extend shelf-life, to control water content, to moderate the action of the yeast in the manufacture of bread, and in the case of meat products, to influence protein structure.
Sodium chloride can be replaced – or partially replaced – in food products with various compounds of other elements. The most common salt replacements are potassium chloride, potassium lactate, magnesium sulphate and calcium chloride.
Another possibility is to add a salt enhancer which works by activating receptors in the mouth and throat to compensate for the salt reduction. Commonly used enhancers include amino acids, monosodium glutamate, yeast products and other flavourings.
A third option has been to alter the physical form of the salt to lower the level at which the flavour is detected, allowing less salt to be used. Cargill’s Alberger brand of flake salt would be an example. Companies are also researching the use of nanotechnology in salt reduction and sea salt which has naturally lower levels of sodium.
The most commonly used salt replacer is potassium chloride but even this is not an ideal replacement in food due to its pronounced bitter, chemical, metallic taste and aftertaste. Typically, sodium reduction is achieved by substituting a proportion of the sodium chloride with potassium chloride. However, masking the undesirable sensory attributes associated with potassium chloride remains a problem.
The primary technical challenge has therefore been to try to eliminate the undesirable bitter and metallic tastes. Most commonly, potassium chloride is combined with monosodium glutamate (MSG), chlorine, ammonium chloride, magnesium sulphate and amino acids.
A number of products using combinations of sodium chloride and potassium chloride are available on the market, such as LoSalt, Salt Balance and Pansalt.
Potassium lactate can be used to reduce the amount of sodium chloride while retaining an acceptable level of perceived salty taste. It is most commonly used in the processed meat sector. In this area, salt is used to help control water content and thus plays a key role in the microbial stability of the products.
Potassium lactate is derived from organic lactic acid, a component which is already naturally present in meat and other food products. This means it is not declared as a preservative but as an acidity regulator or an antioxidant. One example of a product currently on the market which uses this method is Purasal HiPure.
At low concentrations, magnesium sulphate provides a salty taste but at higher levels the taste is bitter.
Over the last couple of decades, magnesium sulphate has been included in a number of different patents relating to salt replacement where it has been used in conjunction with other salts to reduce the level of sodium present.
It has also been suggested that the addition of magnesium sulphate to salt mixtures has potential health benefits, such as reducing blood pressure.
Calcium chloride is often described as having a bitter, sour or even sweet taste at low concentrations but at higher concentrations is described as bitter, salty and sour. It is also found to have a metallic taste and can cause both astringency and irritation in a similar way to hot products such as Tabasco.
However, when it is used in combination with sodium chloride, it has been found that the salty properties of calcium chloride are enhanced while its other less palatable taste attributes diminish. Sucrose and citric acid also have a generally suppressive effect on calcium chloride. These effects potentially enhance the viability of calcium salts as fortifying agents. However, while calcium chloride has potential for use in reduced sodium blends, it is unlikely to be used alone.
Glycine ester has been found to compensate for salt taste in products with a 30% reduction in their salt content. It has been most successful in crisps but can also add a sour taste. In the other products it has been found to result in some sourness or bitterness and add an ‘umami’ savoury flavour to the profile.
Monosodium Glutamate (MSG)
Even though MSG is not in itself salty, using it in certain savoury foods can help in reducing sodium content. MSG dissolves easily in water, absorbs no moisture, causes no agglomeration and gives food a characteristic umami savoury taste. As it contains only one third of the amount of sodium in table salt and is used at much lower levels its use can reduce the sodium level in a finished recipe by as much as 30%.
Trehalose is a non-reducing disaccharide. Examples of products currently on the market containing trehalose include Cargill’s Ascend brand, which is marketed as a flavour enhancer in ready-to-eat meat and poultry products.
Natural ingredients using yeast-based technology are marketed as a means of reducing the sodium content in foods, particularly in bread. For example, DSM’s Maxarite range, which contains non-sodium salts and a yeast extract, is claimed to reduce sodium content in bread and cereals, as well as in processed cheese and cottage cheese, by as much as 50%.
Altering the physical form of salt
Altering the physical form of the salt can lower the threshold at which saltiness is detected and therefore reduce the amount of salt required.
For example, Cargill has modified the salt crystal for its Alberger brand flake salt. The crystals are shaped like hollow pyramid shells, with a larger and more irregular surface, which makes them cling to foods and any other spices more readily, but dissolve faster in the mouth.
Reducing crystal size has important applications in reducing the salt content of chips or biscuits where the salt is applied as a surface coating.
Research into the use of nanotechnology for salt reduction continues. The idea is to use nanosized salt crystals to increase the surface area and achieve a faster blast of flavour. Some suggest using ‘nanosalt’ could eventually achieve reductions of 50% in salt levels in chips and snacks.
In contrast to the application of cutting-edge nanotechnology, which carries with it an element of controversy, other researchers are looking at the most naturally occurring forms of salt for technical solutions. Research is continuing into how to optimise the use of sea salt which has a naturally low sodium content.
Meanwhile, Senomyx has claimed that it has identified the individual protein responsible for salt perception in the taste buds. The identification of this protein, which Senomyx is calling SNMX-29, could enable it to develop screening assays to track down more potential salt substitutes and salt enhancers.
While research into salt replacements continues, there has been an increasing trend in packaged food manufacturing towards simply reducing salt levels per se and adjusting recipes accordingly by adding other flavours.
Research has shown that palates quickly become accustomed to accepting a less salty taste but at first the foods will taste bland. This facet of how we taste salt has been helpful in persuading people to try adding less salt to their food but as around 80% of the salt we consume is already in the food, it requires a concerted effort across the industry for blanket salt reduction to work.
There are two important requirements for this approach to work. First, it has to be fairly gradual. If salt levels suddenly plummeted people would be likely to start adding more salt to their food. Secondly it is only likely to be effective with a strong element of consensus across the industry. Efforts in the UK led by the Food Standards Agency and supported by campaigners and industry appear to have had some success at this concerted approach.
just-food gratefully acknowledges the assistance of Leatherhead Food Research in the preparation of this article.
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