Food chemistry

Fats and oils

Fat is the general name given to a large number of organic compounds. Such organic molecules belong to a larger group of biological compounds known as lipids.
Lipids are formed from carbon, hydrogen and occasionally oxygen. They are non-polar and therefore not soluble in water.

Margarines contain polyunsaturated  vegetable oils. The polyunsaturated fats are partially saturated to solidify them. Fats and oils are a class of lipids, probably the best known. We come across them in our every day lives. Butter and margarines are examples of fats. Oils are liquids while fats are solids, both however have very similar chemical structures and properties.

A fatty acid molecule with its long non-polar carbon chain and the carboxyl functional group. Saturated fatty acids have no double bonds in their structure and therefore have a relatively straight carbon chain. This allows molecules to pack in close together where dispersion forces can exert a greater influence. This is why solid fats a made of unsaturated fatty acids.

A mono-unsaturated fatty acid has one carbon-carbon double bond. eg Oleic acid

A poly-unsaturated fatty acid has more than one carbon-carbon double bond. eg Linoleic acid

Due to the presence of double bonds, poly-unsaturated fatty acids tend to be more reactive than their saturated cousins. The double carbon-carbon bond also causes the chains to be bent. This prevents close packing of the hydrocarbons and the dispersion forces acting are not able to exert much of an attraction. Therefore, polyunsaturated fatty acids have a lower melting temperature than saturated fatty acids and tend to exist as oils at room temperature.