RHIZOPUS-ARRHIZUS LIPASE-CATALYZED INTERESTERIFICATION OF THE MIDFRACTION OF PALM OIL TO A COCOA BUTTER EQUIVALENT FAT

Celite-immobilized lipase from Rhizopus arrhizus was used to intereste rify triacylglycerols of the palm oil midfraction with stearic acid in n-hexane. Under optimum conditions, acyl exchange occurred mainly bet ween the palmitoyl group from the palm oil midfraction and the stearoy l group from the reaction mixture, giving an interesterified product w hose fatty acyl composition was similar to that of cocoa butter. Addit ion of defatted soya lecithin significantly increased the substrate co nversion. This was attributed to the formation of reverse micelles aro und the Celite-immobilized and hydrated enzyme that protected the enzy me from the nonpolar solvent and enhanced substrate and product diffus ion in the enzyme microenvironment. The reverse micelle system exhibit ed higher productivity and operational stability when compared to the Celite-immobilized lipase.