THERMAL-DENATURATION AND GELATION OF BETA-LACTOGLOBULIN AND LACTOFERRIN

Thermal denaturation and gelation of beta-lactoglobulin and lactoferrin in water and in salt environment are investigated by differential scanning calorimetry and dynamic rheometry. Presence of salt increases the denaturation temperature of the proteins. A strong interaction is observed between the proteins when they are mixed and the denaturation temperature of beta-lactoglobulin in the mixture is decreased by 8 degrees C in water and by 3 degrees C in salt solution. The interaction is also found to effect the gel formation process of the proteins. In contrast to the individual proteins, the mixture forms a gel at 70 degrees C in water. Presence of salt increases the gel formation temperature and the gel stiffness of the mixture. Gels formed at 90 degrees C have more elastic character than those formed at 70 degrees C. The effect of the interaction is also noticed to be dependent on the concentration. The studied heat effect on beta-lactoglobulin and lactoferrin are interpreted mainly in terms of electrostatic attractions between these proteins.