Proteins are considered as surface active substances. On the basis of experimentally measured rheological parameters of interfacial layers, protein accumulation at an interface between two immiscible liquids, isotherms of interfacial tension, accounting theoretical ideas elaborated for multicomponent systems, the formation of interfacial layers was referred to phase transition. The property of proteins to stabilize emulsions supposedly is connected with the formation of middle phases of lamellar structure. The correlation between elastic properties of interfacial layers and a phase transition of the middle phase upon addition of salts or lipids has been shown. Lipids being added as cosurfactants lead to the transition from lamellar to other structures, which does not provide emulsion stabilization.
Izmailova, V. N., & Yampolskaya, G. P. (2000). Rheological parameters of protein interfacial layers as a criterion of the transition from stable emulsions to microemulsions. Advances in Colloid and Interface Science, 88(1–2), 99–128. https://doi.org/10.1016/S0001-8686(00)00042-7