Proteins and polysaccharides are present together in many kinds of food systems, and both types of food macromolecules contribute to the structure, texture and stability of food through their thickening or gelling behaviour and surface properties. Much is now known at the molecular level about the functional properties of individual biopolymers, except the fact that molecular weight polydispersity is rarely taken into account. Nevertheless, our knowledge of the role of protein–polysaccharide interactions, in relation to their functionality in complex multiphasic systems, such as food mixed solutions, emulsions or gels, is still rather limited.