Heat induced β-lactoglobulin polymerization: role of the change in medium permittivity

The decrease in medium permittivity due to temperature rise could play an important role in the denaturation/polymerization of heat-treated β-lactoglobulin. The permittivity of a β-lactoglobulin suspension was decreased, either by heat treatment or by adding organic solvent, and the rate of loss of the native β-lactoglobulin was estimated by SDS-PAGE analysis. Setting the permittivity to 63.8 by addition of organic solvent, induced β-lactoglobulin polymerization, but it differed from that induced by change in permittivity upon thermal treatment itself (heating to 70 °C). To explain the protein polymerization process induced by heating, other physical parameters should be taken into account, such as change in water organization around the protein.