Production of specific-structured triacylglycerols by lipase-catalyzed interesterification in a laboratory-scale continuous reactor

A laboratory-scale continuous reactor was constructed for production of specific structured triacylglycerols containing essential fatty acids and medium-chain fatty acids (MCFA) in the sn-2 and sn-1,3 positions, respectively. Different parameters in the lipase-catalyzed interesterification were elucidated. The reaction time was the most critical factor. Longer reaction time resulted in higher yield, but was accompanied by increased acyl migration. The concentration of the desired triacylglycerol (TAG) in the interesterification product increased significantly with reaction time, even though there was only a slight increase in the incorporation of MCFA. Increased reactor temperature and content of MCFA in the initial reaction substrate improved the incorporation of MCFA and the yield of the desired TAG in the products. Little increase of acyl migration was observed. Increasing the water content from 0.03 to 0.11% (w/w substrate) in the reaction substrate had almost no effect on either the incorporation or the migration of MCFA, or on the resulting composition of TAG products and their free fatty acid content. Therefore, we conclude that the water in the original reaction substrate is sufficient to maintain the enzyme activity in this continuous reactor. Since the substrates were contacted with a large amount of lipase, the reaction time was shorter compared with a batch reactor, resulting in reduced acyl migration. Consequently, the purity of the specific structured TAG produced was improved. Interesterification of various vegetable oils and caprylic acid also demonstrated that the incorporation was affected by the reaction media. Reaction conditions for lipase-catalyzed synthesis of specific structured TAG should be optimized according to the oil in use. Presented in part at Food Science Conference, Copenhagen, Denmark, January 30–31, 1997.