DESTABILIZATION OF O/W EMULSIONS CONTAINING FAT CRYSTALS BY TEMPERATURE CYCLING

The behaviour of model triglyceride oil-in-water emulsions during and after a temperature cycle was studied. As a surfactant either sodium dodecyl sulphate (SDS) or a protein was used. The behaviour appeared to be the same as in the case of (recombined) cream. The emulsions, though stable during storage at 5-degrees-C, exhibit considerable thickening when warmed to a temperature where most of the fat was melted and subsequently cooled again. From the results of microscopic observations, determination of the change in the globule size, and observations on the effect of dilution with deflocculating agents it was concluded that partial coalescence is the cause of thickening. A theory is developed to explain the role of the fat crystals. Nucleation plays a key role. It appeared essential that the temperature treatment causes significant changes in the state of crystallization of the fat, without fully melting it.