POSITIONAL AND GEOMETRICAL-ISOMERS OF LINOLEIC-ACID IN PARTIALLY HYDROGENATED OILS

The geometrical and positional isomers of linoleic acid of a partially hydrogenated canola oil-based spread were isolated and identified. Through partial hydrazine reduction and mass spectral studies, cis-9,trans-13 octadecadienoic acid was identified as the major isomer. Other quantitatively important isomers characterized were cis-9,trans-12; trans-9,cis-12 and cis-9,cis-15. These four were also the major isomers in margarine based on common vegetable oils. A number of minor isomers were detected and some structures identified were trans-9,trans-12; trans-8,cis-12; trans-8,cis-13; cis-8,cis-13; trans-9,cis-15; trans-10,cis-15 and cis-9,cis-13. The proportions of the various isomers are given for some margarines in the Canadian retail market. The amounts of trans-9,trans-12 isomer in Canadian margarines were generally below 0.5% of the total fatty acids.