Rheo-NMR and synchrotron X-ray diffraction characterization of nanostructures of triglycerides crystallizing from solutions

Abstract

The characteristics of crystallized fats depend on their solid fraction (SF) and fractal structures, which are affected by shear during crystallization. Binary mixtures of trilaurin (LLL) and trimyristin (MMM) diluted in triolein were used as samples. Pure diluted LLL and MMM were also studied. Samples were examined at different crystallization temperatures either statically or at shear rates of 800, 80, and 8 1/s. The sample cell combined a rheometer with a nuclear magnetic resonance (NMR) device to measure SF value and apparent viscosity. The measurements were compared to equations that describe the dependency of viscosity on solid volume fraction, to understand the effect of crystallites orientation at higher shear rates. Phase transitions during crystallization were observed by time-resolved synchrotron X-ray diffraction under similar conditions. Shear induced a strong reduction in phase onset and transition time and variations in phase distributions and the crystal size.