Emulsion Separation, Classification and Stability Assessment
An emulsion is a dispersed system consisting of at least two immiscible liquids, one of which is an internal or dispersed phase (dispersed as globules) within the external or continuous phase (other liquid phase), generally stabilized by an emulsifying agent. Emulsions have been widely used in many areas including petroleum, agriculture, food, pharmaceuticals and cosmetics, however, consumers highly appreciate emulsions for dermal application. Emulsions can be classified on the basis of their type or droplet size. The physical stability can be evaluated by two accelerated aging methods discussed i.e. storage of emulsions at different temperatures and measurement of creaming process by centrifugation. A stable emulsion is one in which there is a uniform distribution of the dispersed globules throughout the continuous phase. Major types of physical instabilities are discussed in this review including flocculation, creaming, coalescence and breaking and this review will concentrate on methods of improving emulsion stability in practice.