Dynamic adsorption of beta-casein at the gas–liquid interface

The dynamic adsorption of beta-casein onto the air–water interface was experimentally studied in terms of the dynamic surface tension using the pendant bubble method. The experimental data was modelled based on two solutions: diffusion towards a planar interface (Ward and Tordai solution) and a new solution for diffusion to a spherical bubble surface. Both modelled predictions can fit experimental data of 10−6 M solution, except the early section where the surface tension remains constant. The similar values of fitting parameters in both models indicated a minimal effect of bubble size on the considered system. The fitting value of adsorption constant (especially in case of 10−7 M solution) demonstrated the limits of current models.