3.3.2.3 Fats and oils Typeit

Fats and oils are built of a glycerol ‘head’ to which chains of fatty acids are attached. The atoms of carbon in them are bonded together by either single bonds or double bonds. This determines whether a fat is solid or liquid at temperature – generally, saturated fats (which have only single bonds) are and unsaturated fats (in which double bonds are present) are liquid and are, therefore, called . The chemical structure of a fat or oil is important because it determines its consistency, its melting temperature and, therefore, its usage in cooking.

Plasticity of fats means their ability to be reshaped and to melt at different temperatures (they have different points). A good example is butter and lard. They are solid while in the fridge, become soft and greasy at room temperature and melt to an oil during cooking. There are certain types of margarine which are spreadable in low temperatures – you can say that they have plasticity.

When mixed with starch, fats create a layer around starch particles, and, therefore, prevent from forming. This is called and is used to obtain crunchy, crumbly pastries, as in biscuits.

Emulsion is a mixture of and water. Depending on the amount of ingredients used, we can distinguish emulsions, e.g. butter (notice how it ‘sweats’ when taken out of the fridge) and oil-in-water emulsions, e.g. milk (usually fat molecules are spread evenly in the liquid, but when boiled, they will form a coat on top). Since fat is , the particles of fat and water will repel each other, leading to dissection of the emulsion into layers. To prevent that and make the mixture more stable, are used. One of the most popular emulsifiers is lecithin, naturally present in . Emulsions are used not only in cooking, but also in the cosmetic industry. When put in water, fat particles will turn their hydrophilic heads towards it, creating droplets of fat. Emulsifiers will attach to oil droplets keeping them dispersed and making the mixture more stable.