Interactions in protein mixtures. Part I: Second virial coefficients from osmometry

The interaction of proteins (ß-lactoglobulin, Bovine Serum Albumin (BSA), gelatins and whey protein isolate (WPI)) in solution was quantified by measuring their second virial coefficient using membrane osmometry. At neutral pH below 20–40 mM ionic strength, electrostatic repulsion dominated the interaction. At higher ionic strength, BSA, WPI and whey protein aggregates (WPA) were well approximated as hard spheres. On the other hand ß-lactoglobulin behaves as an adhesive hard sphere for which the stickiness parameter t (known from the Baxter model for sticky hard spheres) and depth and width of the adhesive part of the interaction potential were calculated