Model of inhibited surface adsorption: Application to foam stabilization and destabilization

A classic statistical mechanical model of surface adsorption of an object that interacts with another component present in a medium was developed in this work. The effective Hamiltonian for the process is proposed and developed here, which takes into consideration the interactions between one of the objects with a surface and the interaction with another object in the medium. This model allowed for the prediction of the binding isotherm for the object. Monte Carlo computer simulations were employed to model the behavior of the system, which was in good agreement with the theory. This model was complemented with an equilibrium kinetic model of the same system and simulations. Qualitative agreement between the two approaches was achieved by introducing a degeneracy in the cooperative interaction between the object and the component, namely simultaneous positive and negative binding cooperativity of the same process. The model developed and the results obtained will help explain the variability in the foamability of barista milk, where free fatty acids are known to inhibit the adsorption of proteins to the air bubble surface. Here, we suggest that the variability observed could be due to the ratio of free fatty acids to protein, which was never considered before.