Purification of Monoacylglycerol with Conjugated Linoleic Acid Synthesized through a Lipase-Catalyzed Reaction by Solvent Winterization

Abstract

Monoacylglycerol of conjugated linoleic acid (MAG-CLA) is synthesized efficiently by esterification of a free fatty acid mixture of CLA (FFA-CLA) with glycerol using Penicillium camembertii lipase. However, the reaction mixture contained 3-7 wt% FFAs (the acid value, 6-14 mg KOH/g), although the acid value of MAG, which can be used as a food additive, is prescribed to be <6 mg KOH/g (the content of FFAs, < about 3 wt%). Hence, the removal of FFAs in the reaction mixture by winterization was attempted. After the enzyme reaction, the reaction mixture was separated to the oil and glycerol layers. The oil layer (referred to as Rmix[MAG]) included 21.6 wt% glycerol, and its oil part was composed of 5.2 wt% FFAs, 87.0 wt% MAGs, and 7.8 wt% diacylglycerols (DAGs). Here, oil part means FFAs, MAGs, and DAGs in Rmix[MAG]. Rmix[MAG] was first dissolved in 4 mL hexane per 1 g of the Rmix, and the mixture was kept at 0°C for 24 h. The crystallized materials were recovered by centrifugation at -20°C. The content of FFAs in the precipitates decreased from 5.2 to 2.0 wt%, and the content of MAGs increased from 87.0 to 95.8 wt%. To further remove FFAs, solvent winterization of the precipitates was conducted similarly, resulting in a decrease of the content of FFAs from 2.0 to 0.9 wt% and increase of the content of MAGs from 95.8 to 98.4 wt%. The recovery of MAGs through a series of procedures was 84.7% of the initial content of MAGs in the reaction mixture. These results showed that solvent winterization is very effective for purification of MAG-CLA from the reaction mixture obtained by lipase-catalyzed esterification of FFA-CLA and glycerol. © 2006, Japan Oil Chemists' Society. All rights reserved.