Finally, it may be noted that the bilayer concept is not limited to just protein + hydrocolloid systems: it can be applied also to the case of electrostatic interaction between an adsorbed ionic surfactant in the primary layer and an oppositely charged hydrocolloid in the secondary layer (Nilsson & Bergenståhl, 2007b). Furthermore, the concept can be extended to more complex multilayer systems containing three (or even more) different layers (e.g., surfactant–protein–polysaccharide) (Bergenståhl et al., 1995 and Guzey and McClements, 2006). Further research activity on the properties of these mixed and bilayer formulations can be confidently anticipated over the next few years