Interfacial rheology of mixed food protein and surfactant adsorption layers with respect to emulsion and foam stability

Abstract

Interfacial theology is the study of the relationship between interfacial stress and the resultant deformation of the interface. Areas where interfacial rheology is important are very diverse, including for example, drug delivery, lung function and anaesthesia, as well as in typical food emulsions, foams, and solid particle dispersions. The principal food colloids of commercial interest are emulsions and foams. Low-molecular-weight surfactants in foods may be natural components, such as phospholipids, glycerides, fatty acids or synthetic molecules such as the Spans and Tweens. Low molecular-weight surfactants may adsorb strongly or weakly depending on the chemical structure of the surfactant. Because of the higher molecular weight of proteins and the co-operative nature of their adsorption, protein adsorption and desorption tend to be considerably slower than adsorption and desorption of low-molecular-weight surfactants. Most food systems contain mixtures of both proteins and low-molecular-weight surfactants so the competitive adsorption, and any factors that influence it, are of great significance in resolving the relationship between interfacial rheology and the stability of emulsions and foams.