Competitive adsorption of egg white proteins at the air-water interface: Direct evidence for electrostatic complex formation between lysozyme and other egg proteins at the interface

The competitive adsorption of five major egg white proteins, viz., ovalbumin, ovotransferrin, ovaglobulins, ovomucoid, and lysozyme, from a bulk solution having relative protein concentration ratios similar to those in egg white to the air-water interface has been studied at low and high ionic strengths. At 0.1 ionic strength, only ovalbumin and ovoglobulins adsorbed to the interface, and ovotransferrin, ovomucoid, and lysozyme were essentially excluded from the interface. Notably, the surface concentration of lysozyme was essentially zero, indicating that at 0.1 ionic strength it was not electrostatically associated with the other egg white proteins at the interface. However, at 0.002 ionic strength, a significant amount of lysozyme adsorbed to the interface along with the other egg white proteins. Evidence is provided which suggests that at row ionic strength lysozyme forms binary or ternary electrostatic complexes with the other proteins and thus its adsorption to the interface is facilitated by the adsorption of other proteins.