Physical properties of lipase-catalyzed transesterified blends of palm stearin and anhydrous milk fat

Palm stearin (PS) and anhydrous milk fat (AMF) blends, formulated by mixing 40 to 80% PS in increments of 10% (w/w), were subjected to transesterifica tion catalyzed by lipases from Pseudomonas sp. and Rhizomucor miehei (Lipoz yme IM60). The physical properties of the transesterified products were eva luated by slip melting point (SMP), differential scanning calorimetry (DSC) , solid fat content (SFC) and X-ray diffraction (XRD) analyses. SMP results indicated that the Pseudomonas sp. lipase caused a bigger drop in SMP (15. 6%) for a PS:AMF (40:60) blend compared to 12.5% reduction when R. miehei l ipase was used. The same blend, when reacted with either of the lipases, ha d a residual SFC of 7.1% at 40 degrees C. Generally, for all other ratios o f PS:AMF blends, the % of reduction in SMP was higher in the Pseudomonas li pase-catalysed blends compared to the R. miehei lipase-catalysed blends. Ps eudomonas lipase also successfully changed the polymorphic form of unreacte d PS:AMF blends from a mixture of beta and beta' crystals to a predominantl y beta' mixture following transesterification. On the other hand, transeste rification with R. miehei lipase resulted in a product that is beta' domina ting (C) 2000 Elsevier Science Ltd. All rights reserved.