If the fat content of a product is lowered the emulsion is changed and therefore also the composition of the product. In order to keep the taste the same it is then necessary to add more of one particular flavouring component while adding less of another. This means that a completely different flavouring is required with a different composition, that will have a different application level, and possibly a different colour. If the flavouring is formed during the preparation of the product, as with cheese, then this even means a different production process.

The product composition is also of real importance for the final taste in the case of an improvement in the fatty acid composition (addition of liquid fat). The flavour compound dissolves more easily in a liquid than in a solid.
An example of this is an ice lolly. It is sometimes possible to suck the sugared water with the flavour (the liquid) out of the ice lolly leaving a tasteless and often colourless piece of ice (the solid) behind.

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Factsheet The role of fats in the composition of taste

This factsheet is based on information provided by NIZO Food Research, with thanks to Peter de Kok, Principal flavour scientist at NIZO.

Composition of the product

Changing the fats in a product while keeping the taste the same is a complex process that is dependent on many factors. Both lowering the fat content and changing the fatty acid composition has consequences for the perception of the flavour.

Reduction of fat

An aim shared by many product developers is to reduce the fat content of a product without at the same time changing the perception of the taste. Consider a product that consists of 20% water and 80% oil. There is a certain quantity of flavouring in this product and the consumer is used to this particular taste and its strength. A ‘light’ variant of this product may consist of 80% water and 20% oil. Using the same flavouring in the same quantity will result in this product having a very different taste. Flavourings generally consist of a complex mixture of flavour compounds. Many of these flavour compounds dissolve better in oil than in water.

If you lower the fat content there is less of such a flavouring required to keep the taste the same (see the diagrams below). You might actually expect exactly the reverse to be the case.

A particular flavour component dissolves better in oil than in water:	Only 22 units of this flavouring component are needed for the same taste effect in the equivalent light product:
In this example the total quantity of the flavouring component used in this product is 28 units	This is because given the way in which the flavouring component dissolves in oil compared with water there will always be present a number of 2 units in the waterparts and a number of 3 units in the oil parts. The taste effect of both emulsions is now the same.

But the reverse is true in the case of a flavour compound from the particular flavouring dissolving better in water than in oil. Then there actually will be more of that flavour compound necessary if the fat content is reduced. So if the fat content is reduced it is necessary to alter the composition of the flavouring in order to retain the same taste because of a change of the nature of the emulsion. Thus when determining the taste it is necessary in the first instance to consider the nature of the emulsion, or in other words the composition of the product.

Fatty acid composition

The composition of the product is also of real importance when improving the fatty acid composition. If liquid fats (oils, unsaturated fatty acids) are added to a product at the cost of solid fats (saturated fatty acids) the flavour compounds dissolve better in the whole product so that the concentration drops. This means that it is necessary to add more flavouring in order to compensate for this drop. Flavour compounds dissolve badly in a solid, much less than in a liquid because the flavour molecules do not disperse so easily in the crystal lattice of the solid fat (see the diagram below). A solid fat is a substance in which the droplets of oil are much closer to each other than in a liquid fat. Once again the product composition therefore has consequences for the taste.

Both situations give the same effect in the gas phase.
The flavour molecules are represented by the black dots. The oil droplets, containing the triglycerides*, are represented by the blue dots.

* Triglycerides are fat molecules that are composed from glycerol and 3 fatty acids. More about this can be found in the FACTS ON FATS factsheet ‘What is fat’.