More aroma, less salt

‘More aroma, less salt’ - this straightforward formula is the result of a French study in which European Sensory Network researchers examined a simple new method by which the salt levels in food products could be reduced without it negatively effecting the consumer’s taste perception.

Doctors and nutritionists continually complain that we use too much salt. The World Health Organization (WHO) states that ,ideally, a person should consume no more than 5 g salt a day. Too much salt in the diet substantially heightens the risk of high blood pressure and heart disease. Thus ‘salt reduction’ has become an important goal for the food industry.

In practice, this is easier said than done; because of salt’s properties as a taste enhancer, products with lower salt content are often not accepted by consumers. To overcome this problem, the industry has been experimenting with salt substitutes and taste enhancers, as well as optimising the physical form of the salt so that it reaches the taste receptors more effectively.

ESN scientists from the Centre for Nutrition and Taste Research INRA in Dijon, along with ESN industry partners Unilever in Vlaardingen, Holland, have another suggestion: the well-selected use of tasteless odorants that are reminiscent of such salty foodstuffs as bacon, sardines, soy sauce, peanuts and cheese.

Study leader Génica Lawrence explains the basic idea behind this effort: “odour-taste interaction and integration occur at the neural level. This interaction depends on the association between both stimuli. The perceived taste impressions of a food are the results of a variety of sensory signals that are perceived simultaneously and melded in the brain into a general impression. These impressions will be closely linked together in the memory.” Once this has happened, this memory can be triggered simply by the smell of a food that is perceived as salty; thus the senses are ‘tricked’ into relating the taste to the original memory.

Cross-modal interactions

Such exchanges between various sensory modalities are termed cross-modal interactions. In an experiment using lightly salted and variously aromatised water, the researchers investigated which aroma best evokes salty taste impressions. It was shown that samples with the same salt content were perceived as markedly saltier when they were combined with sardine or bacon aroma than was the case with the aroma of comté cheese or soy sauce or in a control condition without added aroma.

In a second study the researchers investigated whether the respective effects could not only be shown in watery solutions but also in complex foods. Here the situation is more complicated, since the taste and smell impressions respond to other perceptible characteristics such as the products’ consistence (texture, rheological parameters) and how well the aroma and the product match. To be able to systematically vary these factors, the researchers developed a test product that included variations of a simple, neutral-flavour mozzarella-like soft cheese with different grades of fat-content and dry-matter levels.

Twenty-seven French consumers aged 19-61 with no previous experience in sensory analysis graded a total of 16 different cheese samples under two separate conditions using a rating scale of 0-10. In a first stage, they wore nose clips and rated the intensity of the four basic taste qualities of sour, salty, bitter and sweet, and texture (firmness, moistness and granularity), along with their particular preferences. Using factor analysis, it was possible to show that the aromas actually did not stimulate taste receptors.

Odour-induced saltiness enhancement

In the second stage without nose clips, the same procedure was carried out. In this test, odour intensity and odour-taste congruence were also rated.

It was shown that, under test conditions without nose clips, the products produced differentiated texture perceptions. While the addition of aroma had no impact on the perception of texture, a marked difference was observed in the taste of the models.

In the condition without the nose clips, the cheese samples with sardine and comté-flavoured products were perceived as saltier than the unflavoured and carrot-flavoured products. The authors call this effect odour-induced saltiness enhancement (OISE). This effect was not the same in all the models, but it was especially pronounced in most models with high fat content. As was expected, the testers found that the comté aroma was more congruent (compatible) with the taste of the cheese than were the sardine and the carrot aromas. However, the sardine aroma did not have a negative effect on the liking of the models, whereas the carrot aroma was clearly less appreciated.

The researchers concluded from these results that only aromas that are associated with saltiness are able to enhance the perception of saltiness in foods. Whether or not the aroma was a ‘good match’ to the food was less important than the intensity of the ‘salty’ aroma.

Génica Lawrence stated that, “Our study suggests that the measured addition of such aromas could be an effective new strategy for food manufacturers in counterbalancing the sensory shortcomings of salt-reduced foods.”

She could also envision situations in which aromas could be used to modify other tastants or food ingredients that are undesirable for health reasons, such as excess sugar or fat. “Aromas might be used to replace missing ingredients or limit undesirable sensory dimensions. For instance, the carrot odour in our study reduced the perception of saltiness.” Since it is acknowledged that sweetness can compensate for bitterness, it would be worth investigating whether aromas associated with sweetness, such as vanilla, have similar effects and could thus contribute to the development of a product in which little or no sugar is needed.”