Fast field cycling NMR relaxometry studies of molten and cooled cocoa butter

Abstract

ABSTRACTDue to its relevance in the confectionery industry, cocoa butter (CB) has been extensively studied. However, most studies focus on its crystallisation properties, whilst studies of its liquid state are lacking. Here, and for the first time, a study of the self-diffusion of CB at different temperatures is presented, using fast field cycling (FFC) nuclear magnetic resonance (NMR) further validated using pulsed field gradient stimulated echo (PGSTE) NMR. Measurements were performed upon heating CB to either 50°C or 100°C and cooling it to 22°C. No hysteresis was found between the different thermal treatments. However, the activation energy (28.7 kJ/mol) estimated from the cooling protocol of the 100°C treatment, was the closest to that reported in the literature for similar systems. This suggests that measurements using a wider range of temperatures, and starting with a liquid material are advisable. Additionally, samples were measured during isothermal crystallisation at 22°C, showing that the region below 1 MHz is the most sensitive to phase changes.