Enrichment of CLA isomers by selective esterification with l -menthol using Candida rugosa lipase

Commercially available preparations of CLA are composed of almost equal amounts of 9- cis ,11- trans (9 c ,11 t )-CLA and 10- trans ,12- cis (10 t ,12 c )-CLA. Each isomer was fractionated and enriched, for availability as a food supplement, by a process comprising selective esterification with l -menthol by Candida rugosa lipase, distillation, and n -hexane extraction. The first selective esterification of CLA isomers was conducted with an equimolar amount of l -menthol of 30°C. The oil phase of the reaction mixture was fractionated into an l -menthyl ester fraction (9 c ,11 t -CLA rich) and an FFA fraction (10 t ,12 c -CLA rich) by distillation. The FFA fraction was esterified again with an equimolar amount of l -menthol to enrich 10 t ,12 c -CLA. The 10 t ,12 c -CLA preparation was obtained as the resulting FFA fraction by distillation. 10 t ,12 c -CLA was enriched to 91% with 40% recovery. To enrich 9 c ,11 t -CLA, the l -menthyl ester fraction in the first esterification was chemically hydrolyzed, and the resulting FFA were esterified again with an equimolar amount of l -menthol. The 9 c , 11 t -CLA preparation was obtained by chemical hydrolysis of the resulting l -methyl ester fraction, followed by n -hexane extraction. 9 c ,11 t -CLA was enriched to 94% with 42% recovery. This effective process for purification of CLA isomers using l -methol is applicable to the production of food supplements.