Creating a yield stress in liquid oils by the addition of crystallisable modifiers

Abstract

The consistency of food and cosmetic products, based on oil systems, can be characterised by some rheological parameters: yield stress, thixotropy and viscosity–shear rate dependence. Microcrystalline waxes – beeswax and ceresin, hard paraffin and hydrogenated fat are used as rheological modifiers of sunflower oil. Yield stress of the modified systems and theirs temperature dependence are discussed. The dependencies of yield stress on the enthalpy of solids for the mixtures are investigated. The results show that the yield stress does not depend only on the enthalpy of fusion of non-melted at test temperature modifier, but much more on the physical crosslinks produced by very small crystallites, which have not contributed significantly to the enthalpy of fusion. Differences between polar and non-polar modifiers are established.