The Formation of a 12‐Hydroxystearic Acid/Vegetable Oil Organogel Under Shear and Thermal Fields

Abstract

AbstractExternal laminar oscillatory shear applied during crystallization in combination with different temperature fields was used to modify the microstructure and physical properties of edible oil organogels. Crystallization at a high cooling rate (30 °C/min) resulted in a spherulitic microstructure with a higher oil‐binding capacity, lower storage modulus and lower yield stress compared with a material (with a fibrillar microstructure) crystallized at a slow cooling rate (1 °C/min). The application of an oscillatory shear resulted in the formation of novel microstructures depending on the cooling regime used. The application of an oscillatory shear (strain > 500 % and frequency = 1 Hz) resulted in the thickening of fibers observed in the slow‐cooled material and an increased incidence of spherulite nucleation in the rapidly cooled material. Increasing the frequency of the oscillatory shear applied did not change the microstructure for the slow‐cooled gel but further increased the incidence of nucleation for the rapidly cooled gel. The application of controlled‐strain oscillatory shear to the crystallizing gel at either cooling rates resulted in an oily and very soft, paste‐like material. This material had a lower storage modulus and poorer oil‐binding capacity compared with the same gel crystallized statically. Reduction of the oscillatory strain from a maximum of 1500 to 500 % moderately mitigated the loss of mechanical properties and oil‐binding capacity although these properties were in no way comparable to those obtained from static crystallization. The study shows that the application of oscillatory shear and different cooling regimes can be used to tailor a crystalline organogel. However, the application of continuous shear must be done with care as application of excessive shear can result in a complete breakdown in gel structure and large amounts of oil loss.