Enzymatic transesterification of palm stearin: anhydrous milk fat mixtures using 1,3-specific and non-specific lipases

The physical characteristics of a palm stearin:anhydrous milkfat (40:60) mixture, enzymatically transesterified in a solvent-free system, was investigated by monitoring changes in the slip melting point (SMP), solid fat content (SFC) and melting characteristics. The enzymes used were 1,3-specific lipases from Aspergillus niger, Rhizomucor miehei, Rhizopus javanicus, Rhizopus niveus, Alcaligenes sp. and non-specific lipases from Pseudomonas sp. and Candida rugosa. Results indicated that Pseudomonas lipase-catalyzed mixtures produced the highest degree of transesterification (33.9%) and rate of transesterification (50.0/h), followed by R. miehei lipase at 32.3% and 27.1/h. The highest % free fatty acid (FFA) liberated was also from the reaction mixture catalyzed by Pseudomonas (2.6 1%) lipase followed by Alcaligenes (2.56%) and R. miehei (2.88%) lipases. The SMP of all the transesterified PS:AMF mixtures underwent only slight reductions, ranging from 0.5 to 2.5°C with reactions catalyzed by Pseudomonas and R. miehei lipases, producing the biggest drop in SMP values.