Rhizopus arrhizus lipase-catalyzed interesterification of the midfraction of palm oil to a cocoa butter equivalent fat

Abstract

Celite-immobilized lipase from Rhizopus arrhizus was used to interesterify triacylglycerols of the palm oil midfraction with stearic acid in n-hexane. Under optimum conditions, acyl exchange occurred mainly between the palmitoyl group from the palm oil midfraction and the stearoyl group from the reaction mixture, giving an interesterified product whose fatty acyl composition was similar to that of cocoa butter. Addition of defatted soya lecithin significantly increased the substrate conversion. This was attributed to the formation of reverse micelles around the Celite-immobilized and hydrated enzyme that protected the enzyme from the nonpolar solvent and enhanced substrate and product diffusion in the enzyme microenvironment. The reverse micelle system exhibited higher productivity and operational stability when compared to the Celite-immobilized lipase.