Progress in stabilization and transport phenomena of double emulsions in food applications

Multiple emulsions are complex systems of emulsion within an emulsion, where the droplets of the dispersed phase themselves contain even smaller dispersed droplets. The two major types are water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O) double emulsions. Double emulsions are unstable thermodynamic systems, which tend to cream, flocculate and coalesce. Much effort has been made to develop methods of 'better sealing' in the inner and outer interfaces and to reduce the droplet size of the emulsion. In addition, dissolved or dispersed compounds in the inner phase of double emulsions tend to be released to the outer phase primarily via a reverse micellar transport (which is diffusion controlled) or through the thin lamellae of a surfactant phase migrating to the outer phase via the outer interface. It is difficult to control the release of the solutes unless macromolecules are used to improve stabilization (steric stabilization) forming a rigid surfactant-polymer complex at the interfaces. The text will describe recent achievements in the use of BSA, casein, gelatin and other natural occurring macromolecules together with monomeric-amphiphilic molecules for possible future applications in food systems.