Enzymatic enrichment of conjugated linoleic acid isomers and incorporation into triglycerides

A method was developed for the enrichment of either the cis 9, trans 11 or the trans 10, cis 12 isomer of conjugated linoleic acid (CLA) from a synthetic CLA mixture consisting predominantly of these isomers in equal amounts. Lipases were screened for their ability to selectively esterify one isomer at a significantly greater rate than the other isomer. An immobilized lipase from Rhizomucor miehei was nonselective, but a lipase from Geotrichum candidum esterified the cis 9, trans 11 isomer more rapidly than the trans 10, cis 12 isomer. This selectivity was exploited at the kilogram scale to prepare an ester fraction with a content of 91% cis 9, trans 11 CLA and an unreacted free fatty acid fraction consisting of 82% trans 10, cis 12 CLA, based on total CLA content. The components of the reaction mixture were separated by molecular distillation. Each enriched fraction was then incorporated into palm oil triglycerides by interesterification with the non‐selective lipase from R. miehei . Two triglyceride fats resulted, which were enriched in either cis 9, trans 11 CLA (26.5% cis 9, trans 11 and 1.7% trans 10, cis 12) or trans 10, cis 12 CLA (3.5% cis 9, trans 11 and 22.9% trans 10, cis 12).