Physical properties of palm kernel olein-anhydrous milk fat mixtures transesterified using mycelium-bound lipase from Rhizomucor miehei

The transesterification activity of mycelium-bound lipase from Rhizomucor m iehei on palm kernel olein:anhydrous milk fat (PKO:AMF) blends was investig ated. Commercial immobilised R. miehei lipase preparation, Lipozyme IM60 (N ovo Nordisk), was used as a comparison. Mixtures of PKO:AMF, at ratios of 1 00:0, 70:30, 60:40, 50:50 and 0:100, were transesterified using either enzy me in a solvent-free system. The triglyceride (TG) profile? slip melting po int, solid fat content, melting thermogram and the polymorphic form of the unreacted and transesterified mixtures were evaluated. Results indicated th at transesterification by either enzyme was able to produce an oil mixture with new TG profiles, generally lower slip melting points and solid fat con tents. The melting thermograms from differential scanning calorimetry analy sis indicated changes in the triglyceride's crystalline composition and an overall shift to lower melting TG. Although the catalytic activities were s imilar for both lipases, Lipozyme-catalysed mixtures produced higher degree s of transesterification (43-51%) than mycelium-bound lipase-catalysed (22- 34%) mixtures. This study also demonstrated that the transesterified PKO:AM F mixture at 70:30 ratio completely melted at 25C, and this meets the melti ng criteria for Cat used in ice cream formulation. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.