In the agrifood industry, salt, or sodium chloride, is a key ingredient that is widely used to structure products and guarantee satisfactory microbiological safety. It also plays a fundamental role in the organoleptic quality of foods. But when it is consumed in excessive quantities, salt acts as a factor favouring the development of cardiovascular diseases. For this reason, health authorities – such as the World Health Organization – are working to achieve a reduction in the salt content of foods so as to reach the nutritional guideline level, which is currently fixed at 5 g/day, or two or three times less than the usual daily amount consumed in some developed countries, including France. Reducing the salt content of foods without affecting their organoleptic and technological properties is now a major challenge for both the agrifood industry and for research, because of the complexity of the underlying scientific questions.
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The INRA researchers sought to understand the mechanisms that trigger the release and perception of salt in the mouth. First of all, sensory and instrumental methods were used to demonstrate the influence of the composition, structure and texture of model dairy gels on the transfer of salt from the product to the saliva, and then on the perception of salty flavour. To achieve this, the scientists recruited a panel of trained tasters to assess the salty taste and perception of texture of the products. Saliva samples were collected from these subjects to measure its salt content during consumption of the products.
Using experimental and mathematical approaches, the second stage consisted in showing that the contact area between the food product and the saliva is a determining parameter to explain the release and perception of a food flavour. This exchange surface depends both on the product (and particularly its ability to fragment) and on the consumer, and more specifically his or her mastication efficiency (ability to break down foods by chewing a given product for a given time). For the study products, it was shown that the presence of fats weakened the structure of the cheese protein network and rendered the product more friable. The exchange surfaces thus generated between the product and the saliva were larger, and the perception of salt more intense.
These findings gave rise to a novel mechanistic model that can describe and quantify those characteristics of a product and an individual that can explain salt release. Although the physiology of a consumer – and particularly mastication efficiency – is a key element in this process, by using this model it might be possible to develop new products for specific groups of individuals, such as the elderly or babies, etc. By modulating the ability of a product to fragment through the production process or formulation, it would become possible to develop foods with lower salt contents while maintaining their salty flavour; for example for the elderly whose mastication efficiency is reduced.
All these results constitute a novel approach to the question of reducing the salt content in foods. They combine several experimental methods, focus in an innovative manner on what occurs in the mouth and concern model products with textures and structures ranging from liquid to solid. They demonstrate that the perception of salt is a multifactorial event that involves physicochemical interactions between constituents in the product matrix, structural and textural properties, physiological processes and perhaps even sensory interactions.
Finally, these findings represent a major advance in our understanding of the perception of salt. They thus open the way to new opportunities for the formulation of low-salt products that will comply with both organoleptic and nutritional criteria. The scientists are now pursuing this work on a bread model. Research is also ongoing on cheese, using a complete model that also takes account of product aromas.
References :
Mechanistic model to understand in vivo salt release and perception during the consumption of dairy gels. Journal of Agricultural Food Chemistry, 2011, 59: 2534.
de Loubens Ca, Saint-Eve Ab, Deleris Ia, Panouillé Mb, Doyennette Ma, Tréléa ICb, Souchon Ia.
Mechanistic model of in vitro salt release from model dairy gels based on standardized beakdowm test stimulation mastication. Journal of Food Engineering, 2011, 105: 161.
de Loubens Ca, Panouillé Mb, Saint-Eve Ab, Déléris Ia, Tréléa ICb, Souchon Ia.
Understanding of the influence of composition, structure and texture on salty perception in model dairy products. Food Hydrocolloids, 2011, 25: 716.
Panouillé Mb, Saint-Eve Ab, de Loubens Cb, Déléris Ia and Souchon Ia
a INRA, UMR 782 GMPA, F-78850 Thiverval-Grignon, France
b AgroParisTech, UMR 782 GMPA, F-78850 Thiverval-Grignon, France
© Joint Research Unit for Food Process Engineering and Microbiology
Top left: microstructure of a non-fat cheese (the protein network is stained green).
Top right: microstructure of a cheese containing fat (the fat is stained red and is intimately linked to the protein network in green).
Bottom: after the application of the same compression force (simulating mastication), it can be seen that the fatty cheese (right) is fragmented more than the fat-free cheese.
The presence of fat in the protein network weakens the matrix and explains this greater fragmentation.
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