Physical properties of lipase-catalyzed interesterification of palm stearin with canola oil blends

Interesterified blends of hard palm stearin (IV of 11) and canola oil (hPS/CO) in ratios of 20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 were prepared using immobilized Thermomyces lanuginosus lipase (Lipozyme TL IM). Comparison of physical properties was carried out between non-interesterified and enzymatically interesterified products by monitoring their slip melting point (SMP), solid fat content (SFC), melting thermogram and polymorphism behavior. The Lipozyme TL IM-catalyzed interesterification significantly modified the physical properties of the hPS:CO blends. The results showed that all the interesterified blends had lower SMP and SFC than their unreacted blends. The SMP result showed that the interesterified blends of hPS/CO 40 : 60, 50 : 50 and 60 : 40 could be useful for stick margarine and shortening applications, respectively. From the SFC analysis, the interesterified blends of hPS/CO 40 : 60 have SFC curves similar to vanaspati. The interesterified blends of hPS/CO 50 : 50 and 60 : 40 have SFC curves similar to margarines, puff pastry margarine and shortening. Interesterification had replaced the higher- and lower-melting triacylglycerols by the middle-melting triacylglycerols, yielding mixtures of lower SMP and SFC, compared to the original palm stearin. X-ray diffraction analysis indicated the appearance of beta' crystals in all the interesterified hPS/CO blends from predominantly P-type oils.