PHYSICAL-PROPERTIES OF PSEUDOMONAS AND RHIZOMUCOR-MIEHEI LIPASE-CATALYZED TRANSESTERIFIED BLENDS OF PALM STEARIN PALM KERNEL OLEIN

The physical properties of Pseudomonas and Rhizomucor miehei lipase-ca talyzed transesterified blends of palm stearin:palm kernel olein (PS:P KO), ranging from 40% palm stearin to 80% palm stearin in 10% incremen ts, were analyzed for their slip melting points (SMP), solid fat conte nt (SFC), melting thermograms, and polymorphic forms. The Pseudomonas lipase caused a greater decrease in SMP (15 degrees C) in the PS:PKO ( 40:60) blend than the R. miehei lipase (10.5 degrees C). Generally, al l transesterified blends had lower SMP than their unreacted blends. Ps eudomonas lipase-catalyzed blends at 40:60 and 50:50 ratio also showed complete melting at 37 degrees C and 40 degrees C, respectively, wher eas for the R. miehei lipase-catalyzed 40:60 blend, a residual SFC of 3.9% was observed at 40 degrees C. Randomization of fatty acids by Pse udomonas lipase also led to a greater decrease in SFC than the rearran gement of fatty acids by R. miehei lipase. Differential scanning calor imetry results confirmed this observation. Pseudomonas lipase also suc cessfully changed the polymorphic forms of the unreacted blends from a predominantly beta form to that of an exclusively beta' form. Both be ta and beta' forms existed in the R. miehei lipase-catalyzed reaction blends, with beta' being the dominant form.