Isotherms are used to quantify the amount of adsorbed protein on a surface at a constant temperature, depending on the concentration of protein above the surface.  Researchers have used a Langmuir-type isotherm model to describe experimental values for protein adsorption.
In this equation 
*  is the amount of adsorbed protein
*  is the surface area per molecule
*  is the partial molar volume of protein
*  is the negative of the Gibbs Free Energy of adsorption per unit area and
*  is the equilibrium protein concentration.
This equation has been applied to a laboratory setting of protein adsorption at temperatures higher than 50 °C from a model solution of protein and water. It is especially useful for modeling protein fouling in milk processing.