Faraday research article. Structure and composition of adsorbed protein layers and the relationship to emulsion stability

Abstract

Factors affecting the stability of oil-in-water emulsions with respect to coalescence, creaming and flocculation are critically reviewed with emphasis on the role of adsorbed protein and free polysaccharide. Crucial differences in structure between adsorbed layers of a disordered protein (β-casein) and a globular protein are described with particular reference to recent results obtained by specular neutron reflectance. Based on parallel experiments in emulsions and at planar oil/water interfaces, information is now becoming available on the structure and composition of layers adsorbed from mixtures of proteins or mixtures of protein + surfactant. Some of the general features of competitive and cooperative adsorption in mixed systems containing protein can be described by a new lattice-based Monte Carlo computer simulation model. In this regard, the statistical description of how covalent linkage to polysaccharide affects the surface and emulsifying behaviour of protein is especially noteworthy.