Lipids occur in almost all foodstuffs, and most of them (more than 90%) are in the
form of triglycerides, which are esters of fatty acids and glycerol. These natural fatty acids
contain straight-chain even-numbered aliphatic carboxylic acids, which may be saturated or
unsaturated with up to six double bonds. The latter are normally arranged along the chain,
separated from each other by methylene groups and with cis conformations. It has been well
established that the carbon chain length and the degree of saturation of the fatty acids are
most critical in determining the oxidative stability of the lipids. In addition to triglycerides,
foods also contain other types of lipids such as phospholipids, Glycolipids, Sphingolipids,
lipoproteins, sterols, and hydrocarbons.