THERMAL-DENATURATION AND GELATION OF BETA-LACTOGLOBULIN AND LACTOFERRIN

Thermal denaturation and gelation of beta-lactoglobulin and lactoferri n in water and in salt environment are investigated by differential sc anning calorimetry and dynamic rheometry. Presence of salt increases t he denaturation temperature of the proteins. A strong interaction is o bserved between the proteins when they are mixed and the denaturation temperature of beta-lactoglobulin in the mixture is decreased by 8 deg rees C in water and by 3 degrees C in salt solution. The interaction i s also found to effect the gel formation process of the proteins. In c ontrast to the individual proteins, the mixture forms a gel at 70 degr ees C in water. Presence of salt increases the gel formation temperatu re and the gel stiffness of the mixture. Gels formed at 90 degrees C h ave more elastic character than those formed at 70 degrees C. The effe ct of the interaction is also noticed to be dependent on the concentra tion. The studied heat effect on beta-lactoglobulin and lactoferrin ar e interpreted mainly in terms of electrostatic attractions between the se proteins.