Occurrence of C16:1 isomers in milk fats from ewes fed with different dietary lipid supplements

The trans as well as the cis C16:1 isomer profiles were established in 43 ewe milk fats supplemented with different dietary lipid sources representative of the variety of unsaturated fatty acids found in nature such as olive, sunflower, linseed and fish oils. Fractionation by silver-ion solid phase extraction facilitated a rapid separation of the trans, cis and saturated FA before gas chromatography analysis took place. C16:1 isomers with a double bond in positions 7, 9 and 13 in the cis group and 8 and 9 in the trans fraction were the most abundant. Dietary lipid supplementation produced a noticeable increase in the total trans C16:1 content and elevated correlations were observed between trans-8 C16:1 and trans-10 C18:1 as well as trans-9 C16:1 and trans-11 C18:1. These results support the idea that altering the trans C18:1 profile affects trans C16:1 isomer composition consistent with the β-oxidation products from the trans C18:1 isomers.