Use of enzymatic transesterified palm stearin-sunflower oil blends in the preparation of table margarine formulation

Palm stearin–sunflower oil (PS:SO) blends, formulated by mixing 40 to 80% palm stearin in increments of 10% (w/w), were subjected to transesterification catalysed by lipases from Pseudomonas sp. and Rhizomucor miehei (Lipozyme 1M 60). The physical properties of the transesterified products were evaluated by slip melting point (SMP), differential scanning calorimetry (DSC), solid fat content (SFC) and X-ray difflaction (XRD) analyses. SMP results indicate that Pseudomonas lipase caused a bigger drop in SMP (33%) in the PS–SO (40:60) blend than the R. miehei-lipase-catalysed reaction blend (13%). The Pseudomonas-catalyzed blends of PS-SO, at 40:60 and 50:50 ratios, showed complete melting at 37 and 40°C, respectively, while the R. miehei-catalyzed PS–SO blend at 40:60 ratio had a residual SFC of 3.9% at 40°C. Pseudomonas lipase also successfully changed the polymorphic form(s) in the unreacted PS–SO mixture from a predominantly β form to a predominantly β′ form in the transesterified blends. However, no changes in polymorphic forms were observed after transesterification with R. miehei lipase (as against to the unreacted PS–SO blends). These results suggest that the Pseudomonas lipase caused a greater randomization and diversification of fatty acids, particularly palmitic acids, in palm stearin with the unsaturated fatty acids from sunflower oil than did R. miehei lipase. Based on the physical characteristics, the Pseudomonas-catalyzed 40:60 and 50:50 PS:SO blends would be the two most suitable blends to be used as table margarine formulations.