Trans fatty acids: Definition and occurrence in foods

Abstract

Most of fatty acid double bonds are in cis configuration, but some processes may isomerise double bonds from cis to trans configuration and from their naturally occurring positions in the carbon chain. Since some fatty acids with trans double bond(s) are suspected to have adverse effects, several countries have regulated the inclusion of trans fatty acid (TFA) content labelling. The French governmental authorities requested AFSSA to propose recommendations regarding food labelling. This first article summarises the discussion on a regulatory TFA definition and reviews the occurrence and origins of TFA in foods. From a chemical point of view, a TFA is any kind of fatty acid that has one or more double bond(s) in trans configuration, but restricted TFA definitions have been proposed for food labelling purposes. These definitions exclude fatty acids with conjugated double bonds on different criteria which are commented on in this paper. Taking into account the goal of TFA labelling and the potential harmful properties of some trans conjugated fatty acids, the working group proposes the chemical definition for TFA labelling purposes. The main TFA natural origin is ruminal biohydrogenation, and therefore TFA are present in dairy products and ruminant meat. TFA are also found in domestically or industrially processed foods due to hydrogenation or heat treatment effects on oils and fats. Although the TFA molecules produced by both natural and industrial processes are often quite similar, TFA distribution profiles and levels are very different from one case to another.

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

“…. While the naturally occurring isomers have mainly cis configuration, trans fatty acids appear naturally in milk [1,2] and can be artificially produced by heating and hydrogenation of vegetable oils [3]. Investigation of function and possible adverse effects of trans fatty acids on human health have been carried out extensively in recent years [4,5].…”

Should the pharmacological actions of dietary fatty acids in cardiometabolic disorders be classified based on biological or chemical function?

“…The major rTFA derived from bovine milk fat include C18:1t11 (~25% of total TFA; 27 vaccenic acid), C18:1t10 (~20% of total TFA), C18:1t12 (~20% of total TFA) and c9, t11 28 CLA (~10% of total TFA; rumenic acid) [237]. However, iTFA from partially hydrogenated 29 vegetable oils contains 85-95% of trans-MUFA and 5-15% of trans-PUFA, about 85% of 30 which included two geometric LA isomers (C18:2c9,t12 and C18:2t9,c12) [228]. Of the total represent up to 85-95% [238].…”

“…1 TFA are unsaturated fatty acids with at least one double bond in the trans configuration 2 [227]. Depending on the source and the fatty acid composition of the starting oil, TFAs may 3 include series of trans-MUFA and trans-PUFA which are geometric and positional isomers 4 of palmitoleic, oleic, linoleic, α-linolenic and γ-linolenic acids [31,228]. 5…”

Effect of Frying Temperature and duration on the Formation of Trans Fatty Acids in Selected Fats and Oils

“…Thermal treatments of fats and oils such as deodorization, cooking, and frying, generate trans fatty acids isomers with limited double bond migration along the carbon chain. Unlike partial hydrogenation, heating induces the formation of mainly trans 18:2 and trans-18:3 [18]. …”