The effect of shear and thermal gradients on the solidification of an edible oil organogel
This thesis is an investigation of the use of shear (during crystallization) and cooling regimes to modify the microstructural characteristics and macroscopic properties of edible oil organogels. This study has shown that varying the cooling rate resulted in different microstructures. In addition, the application of an oscillatory shear resulted in the formation of novel microstructures. The mechanical properties and oil-binding capacity of gels developed under these treatments were examined to ascertain the effect of the microstructural changes on the material properties. A high cooling rate resulted in a material with a lower storage modulus and yield stress compared to a material cooled at a low cooling rate. The application of a controlled-strain oscillatory shear past the gelation point resulted in a material more akin to a liquid dispersion than a gel. The resulting material had relatively low elasticity and poor oil-binding capacity. Changes to the shearing regime were explored in order to prevent the formation of this liquid dispersion. Applying a controlled oscillatory stress, reducing the oscillatory strain and turning off shear prior to gelation all resulted in a gel with properties comparable to a quiescently cooled gel although there were some differences in mechanical properties (such as the yield stress) which indicated that the application of an oscillatory shear can be used to affect the macroscopic properties.