Phase Behavior of Cocoa Butter in a Two-Step Isothermal Crystallization

Abstract

Different analytical techniques (differential scanning calorimetry, pulsed nuclear magnetic resonance, and real-time X-ray diffraction using synchrotron radiation) were used to study the isothermal cocoa butter crystallization at temperatures between 19 and 23 °C. In this temperature range, the crystallization was shown to consist of two steps. In the first step, part of the melt crystallizes into the α polymorph, while in the second step α crystals transform into β‘ crystals via a solid−solid transition. This second step starts before the melt-to-α transition is complete if crystallization is conducted at low temperatures. In the late stage of this solidification process, the α crystallization stops and only the polymorphic transition from α into β‘ is observed. No β‘ crystals are formed directly from the melt after the conversion has come to an end since an isosbestic point appears in the small-angle X-ray scattering patterns during the late stage of solidification that lasts until the very end of the β‘ crystal formation.