Quantitative characterization of unsaturated and trans fatty acids in ewe’s milk fat

Ewe's milk fat obtained from the milk of five different herds were studied to characterize main and minor fatty acids using a combination of gas chromatography and mass spectrometry. In order to assess monounsatured trans fatty acids content, fatty acid methyl esters (FAME) were fractionated by silver ion thin-layer chromatography prior to gas chromatography analysis. Trans fatty acids (TFA), including conjugated linoleic acid, represented 4.9% of the total FAME; most of them belonged to C18:1 trans isomers (2.9%) with a small range of variation (2.5-3.2%). The distribution profile of trans-C18:1 molecules indicated that more than half were trans-11, whereas the proportion of potentially unhealthy compounds (trans-10 and trans-9 C18:1) was less than 10%. Mean trans-C16:1 content was 0.25% of total FAME. The sum of the different trans-C18:2 isomers (excluding conjugated linoleic acid) was 0.88% and C18:3 trans isomers represented 0.16%.