Positional and geometrical isomers of linoleic acid in partially hydrogenated oils

Abstract

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.