Interactions of chitin nanocrystals with β-lactoglobulin at the oil-water interface, studied by drop shape tensiometry

Particle stabilized emulsions have been gaining increasing attention in the past few years, because of their unique interfacial properties. However, interactions between food grade particles and other surfactants at the interface still need to be understood. In this research, the interfacial properties of chitin nanocrystals (ChN) were studied in the presence of a surface active milk protein, beta-lactoglobulin (beta-lg), often used to stabilize oil-in-water emulsions. ChN were prepared by acid hydrolysis of chitin. At low pH (pH 3), ChN and beta-lg do not interact, as demonstrated by light scattering measurements, and both components carry positive charge. The properties of the interface were tested using drop shape tensiometry. Addition of ChN or beta-lg to the aqueous phase reduced the interfacial tension, and beta-lg adsorption was characterized with an increase in the interfacial elasticity. When beta-g was added to a solution containing 0.1% ChN, the film elasticity increased first and then decreased with increasing beta-lg concentration. The mixed film elasticity was the highest at a combination of 0.1% ChN + 0.01% beta-lg, when both molecules were simultaneously added to the aqueous phase. On the other hand, when beta-lg was added after ChN, the protein did not affect the properties of the interface, indicating that the ChN (0.1%) equilibrated film was stable and that protein protein interactions, normally resulting in an increase in the film elasticity, did not occur. (C) 2013 Elsevier B.V. All rights reserved.