Heterogeneous Nucleation Effects of Talc Particles on Polymorphic Crystallization of Cocoa Butter

Abstract

Polymorphic crystallization of cocoa butter (CB) in a bulk system was examined for the influence of adding talc particles at different concentrations (0.1%-5%). While the system was cooled from the melt and subsequently heated, changes in the heat flow and crystal structure of CB were analyzed using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD). Synchrotron radiation microbeam X-ray diffraction (SR-µ-XRD) was employed to determine lamellar-plane directions of CB crystals occurring with talc addition. At any cooling rates (0.1-15 °C/min) applied, talc promoted CB crystallization to elevate the onset crystallization temperature logarithmically with the increasing concentration of talc; this effect became more prominent at higher cooling rates. Talc also acted as a polymorphic stabilizer, so that CB crystallized in more stable forms even when cooled at the highest rate of 15 °C/min. Moreover, a highly ordered lamellar-plane direction was extensively observed for CB crystals occurring with 0.1% talc addition, which was disturbed by 0.5% talc addition probably due to the spatial dispersion of densely populated talc particles in their randomized orientation. These heterogeneous nucleation effects indicate the potential of talc particles to be used for quality and productivity control of CB-based products.