Polyunsaturated fatty acids (PUFAs) are

fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an B ...

that contain more than one

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

in their backbone. This class includes many important compounds, such as essential fatty acids and those that give

drying oil A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature. The oil hardens through a chemical reaction in which the components crosslink (and hence, polymerize) by the action of oxygen (no ...

s their characteristic property. Polyunsaturated fatty acids can be classified in various groups by their chemical structure: * methylene-interrupted polyenes * conjugated fatty acids * other PUFAs Based on the length of their carbon backbone, they are sometimes classified in two groups: * short chain polyunsaturated fatty acids (SC-PUFA), with 18 carbon atoms * long-chain polyunsaturated fatty acids (LC-PUFA) with 20 or more carbon atoms

Dietary sources

Types

Methylene-interrupted polyenes

These fatty acids have 2 or more '' cis'' double bonds that are separated from each other by a single methylene bridge (--). This form is also sometimes called a ''divinylmethane pattern''. The essential fatty acids are all omega-3 and -6 methylene-interrupted fatty acids. ''See more at Essential fatty acids—Nomenclature''

Omega-3

Omega-6

Omega-9

Conjugated fatty acids

Other polyunsaturated fatty acids

Function and effects

''The biological effects of the ω-3 and ω-6 fatty acids are largely mediated by their mutual interactions, see

Essential fatty acid interactions The two essential fatty acids are omega 3 and omega 6, which are required for a good human health. However, the effects of the ω-3 (omega-3) and ω-6 (omega-6) essential fatty acids (EFAs) are characterized by their interactions. The interac ...

for detail.''

Thermal degradation

Polyunsaturated fatty acids in culinary oils undergo

oxidative Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

deterioration at temperatures of . The heating causes a

free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabo ...

chain reaction, which oxidizes the PUFAs into

hydroperoxide Hydroperoxides or peroxols are compounds containing the hydroperoxide functional group (ROOH). If the R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. ...

, which further decomposes into a complex mixture of secondary products.

References

Citations

General References

* * * *{{cite journal , author= Heinz, title=Similarities and Differences in Lipid Metabolism of Chloroplasts Isolated from 18:3 and 16:3 Plants , journal=Plant Physiol , volume=72 , issue=2 , pages=273–279 , year=1983 , pmid=16662992 , doi= 10.1104/pp.72.2.273 , last2= Roughan , first2= PG , pmc= 1066223 Fatty acids Nutrition Nutrients pt:Gordura poliinsaturada