CHAPTER EIGHT

It is clear that protein adsorption at oilwater or airwater interfaces is basically thermodynamically driven. The thermodynamics of proteinwater interactions in the bulk solution, as well as within the interfacial phase, plays a crucial role: that is, during adsorption there is a reduction in the thermodynamic activity (i.e., concentration) of water molecules in the interfacial region (Damodaran, 2004). It is commonly envisaged that the process of forming an adsorbed protein layer involves four main stages, each one contributing significantly to the change in the overall free energy of the system (Graham and Phillips, 1979a,b; Miller et al., 1993; Dickinson and McClements, 1995; Murray, 2002; Damodaran, 2004; Wilde et al., 2004). The four stages are set out below.