INTERESTIFICATION OF BUTTERFAT BY LIPASE FROM RHIZOPUS-NIVEUS IN REVERSE MICELLAR SYSTEMS

Butterfat was interesterified in phosphatidylcholine reverse micellar systems containing hexane at different ratios of water per mol surfactant (W-0), with a commercial lipase (Lipase N, Amano). The amount and composition of free fatty acids were found by gas-liquid chromatography. Triacylglycerols were separated from interestified butterfat by column chromatography on a Supelclean LC-SI column. The purified triacylgylcerols were separated analytically by high-pressure liquid chromatography. The positional distribution of fatty acids was identified by enzymatic deacylation with commercial pancreatic lipase. The addition of up to 2.2% water ( W-0 = 17.4) to the reaction mixture had little effect on the interesterification yield, but shifted the reaction equilibrium in favor of hydrolysis by 4-fold. Further additions of water up to 4.4% (W-0 = 34.8) resulted in maximum yield, with a decreased degree of hydrolysis, from 2.2 to 1.8 mmol of free fatty acids per gram of butter. The interesterified butterfat triacylglycerols had an increased amount of palmitic acid (C16:0) at the sn-2 position with a decrease in the proportions of small. chain fatty acids (C4-C10).