Thermodynamic analysis of the isothermal fractionation of palm oil using a novel method for entrainment correction

The crystallisation kinetics of individual triacylglycerols (TAGs) were studied during the isothermal fractionation of palm oil. On filtration, entrainment of liquid olein within the stearin cake was found to significantly affect measured solid stearin compositions. These could be corrected for entrainment using a mass balance based method along with the assumption that triunsaturated TAGS did not crystallise. These calculations indicated high olein entrainment levels of similar to 57-59% within the stearin cake, with typically only similar to 10% of the palm oil crystallising. These values were validated using pulsed NMR solid fat content measurements. The corrected stearin compositions revealed that diunsaturated TAGs were also virtually absent in the solid phase. Crystallisation was initially dominated by trisaturated TAGS, and later by the monounsaturated TAGs once the trisaturates had depleted from the liquid. The time-course of individual TAG crystallisation rates correlated well with chemical potential driving forces based on temperature and composition information, assuming ideal behaviour.