Adsorption of proteins at the polar oil—water interface

Abstract

Abstract Adsorption isotherms of BSA and gelatin at the polar peanut oil—water interface have been studied as a function of biopolymer concentration, ionic strength of the medium, pH, and temperature. For BSA, the maximum amount adsorbed at saturation (Γ p m ) is found to be affected appreciably by the presence of various neutral salts such as KSCN, Na 2 SO 4 , LiCl, and CaCl 2 . Ionic strength has little effect on the isotherms near the isoelectric pH 5.0. Γ p m for BSA is affected by the change in pH, and the extent of adsorption decreases with temperature increase. However, the isotherm for gelatin is insensitive to change in pH and temperature. After initial saturation, Γ p for gelatin further increases sharply without limit even when the equilibrium protein concentration has been brought to 1.6%. The values of the standard free energy change for adsorption have been calculated on the basis of the Gibbs equation. The standard entropy and enthalpy changes calculated therefrom are positive.