Effects of Tripalmitin and Tristearin on Crystallization and Melting Behavior of Coconut Oil

We investigated the crystallization behavior of coconut oil (CO) with tripalmitin (PPP) and tristearin (StStSt) as additives. The effects of cooling rates (2°C, 5°C, and 10°C min⁻¹) and triacylglycerol concentrations (0.3–10 wt.%) on crystallization and melting behavior of CO were studied using differential scanning calorimetry (DSC) and optical microscopy. The polymorph was also examined using synchrotron radiation X-ray diffraction (SR-XRD). From the DSC results, two exothermic peaks for CO crystallization indicated two compositions in CO. From the SR-XRD results, the α form crystallized first at a high crystallization temperature (HTc) followed by β′ crystallization at low temperature (LTc), after which both HTc-α and LTc-β′ transformed into the β′ form of CO (CO-β′) solid solution during heating. Although the addition of PPP increased crystallization temperature of CO, it did not change its polymorphic pattern. However, during slow cooling with the StStSt additive, CO-β′ crystallization was induced from the melt directly. Moreover, under isothermal conditions, the crystallized StStSt spherulites induced nucleation of CO more than did PPP. Therefore, PPP increased the crystallization temperature of CO in both HTc and LTc fractions without changing the polymorph of CO, while StStSt promoted crystallization of CO directly into CO-β′.