Nanoscale effects on oil migration through triacylglycerol polycrystalline colloidal networks

Abstract

The following paper studies the effects of laminar shear on the nano- and meso-scale structure of polycrystalline materials (cocoa butter). Furthermore, the effect of laminar shear on the migration kinetics of stained triacylglycerol (TAG) oil through a polycrystalline colloidal TAG network was characterized and quantified. Several models were used to study this phenomenon. A low diffusion coefficient was observed in cocoa butter crystallized under shear. This suggested that the migration rate of liquid TAGs through a polycrystalline TAG network can be modified using external fields. A lower migration rate was observed in the shear-crystallized samples. These samples had a smaller crystallite size indicating that particles of this size will retard oil migration. The arrangement of the crystalline component also had a strong effect on the oil migration rate (OMR). Liquid oil diffusivity was decreased by about 4.6 to 30 times in samples that exhibited alignment of the crystalline material along a given axis. Moreover, the tortuosity of the diffusive path in the shear-crystallized samples was approximately 4 to 12.5 times higher than that of the static sample. Finally, the relationships between the structural factors (nanoparticle size, domain size, tortuosity and particle distribution) and the permeability coefficients suggest that shear crystallization can retard oil migration by reducing the network's permeability by about a factor of 100.