Probing crystallization of cocoa butter via thermal and X-ray techniques: solving polymorphic transitions using independent components analysis

Abstract Cocoa butter (CB), a natural lipid, is widely used in the food and pharmaceutical industries. However, it is characterized by a polymorphism which significantly affects its physicochemical properties under varying temperatures. Because synthesis, storage and transportation may occur under varying temperatures conditions, understanding its thermal behavior is a crucial step for its characterization and final product quality. In this study, the crystalline structure of CB was analyzed using differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS), focusing on developed procedures to isolate form II using variations in heating/cooling rates. DSC curves were deconvoluted using Gaussian curve shapes and the results revealed clear coexistence of polymorphs in the raw material. However, different heating/cooling rates showed different behavior. Recording DSC data with cooling at 10 K min −1 affected the crystallization since the crystal memory was not completely erased, while slower rates of 2–5 K min −1 allowed more time for crystallization and organization. At these heating rates, it was possible to isolate form II at 14–15 °C. To deconvolute the peaks and trace the polymorphic transitions during the cooling step, the SAXS data were evaluated using independent components analysis (ICA). In-situ SAXS provided detailed insight into the crystallization process, demonstrating that the cooling/heating rate and the isotherm time at 0 °C were critical factors. At the same time, ICA helped to isolate signals of the different forms and allowed a direct comparison of different temperature conditions, highlighting the potential of this methodology for characterizing CB and its products.