Hydrodynamics of rising air bubbles in mixture of proteins with non-ionic surfactants to declare their interaction at the air-water interface

Evaluation of behaviour of adsorbed layers of protein-surfactant mixture at the air-water interfaces have recently received great attention due to their wide applications in food and pharmaceutical industries. In this research, qualitative study of surface activity of two kinds of proteins, Beta- Lactoglobulin (BLG) and Beta-Casein (BCS), nonioinic surfactant of C10DMPO, and the mixtures of them in different concentrations at the air-water interface is investigated using rising bubble method. The similarity between measured local velocity profiles can be due to the fact that all mentioned materials are surface-active one and could create the Marangoni effect and develop a dynamic adsorption layer. As there is no significant interaction between the protein and surfactant molecules, stable complex structures cannot be formed in the protein-C10DMPO mixture. The mixture velocity profile is more similar to that of the surfactant which is a result of replacement of protein molecules or complexes with free surfactant at the bubble interface. It is found that the mixture of non-ionic surfactant with BCS has a bit synergetic effect while for its mixture with BLG, a negative synergy is observed which is resulted from the shape of protein.