PARTIAL COALESCENCE IN OIL-IN-WATER EMULSIONS .2. INFLUENCE OF THE PROPERTIES OF THE FAT

The influence of the properties of the fat in oil-in-water (o/w) emulsions on partial coalescence was investigated. As a surfactant either sodium dodecyl sulphate (SDS) or a protein was used. The presence of crystals in the fat globules of an o/w emulsion can tremendously enhance the instability of the emulsion. It was observed that in emulsions exhibiting partial coalescence a continuous fat network is present throughout the globules. The formation of such a network depends on the size of the crystals and of the globule: the larger the crystals and/or the smaller the globule the higher the solid fat content needed for a continuous fat network to be formed. Consequently, in most cases partial coalescence considerably increased with increasing solid fat content. Above a certain solid fat content, the rate of partial coalescence decreased again. The optimum solid fat fraction for partial coalescence depended both on the properties of the fat and on the velocity gradient to which the emulsion was subjected: the higher the velocity gradient, the lower the solid fat content at which the partial coalescence rate started to decrease again.