FRACTAL AGGREGATION OF WHEY PROTEINS

Heat-induced aggregation of whey proteins is investigated in the intermediate pH regime (pH 4-6). Dynamic light scattering was used to monitor the apparent hydrodynamic radii of the aggregates during aggregation, and static light scattering was applied to study the structure of the aggregates. The structure is characterized by a fractal dimension, D, which depends on pH, electrolyte concentration and temperature of denaturation. In the pH range 4-6 whey proteins agglomerate in fractal flocs, the properties of which are in agreement with predictions of computer simulations for diffusion and reaction-limited aggregation. In addition, rheological data for whey protein gels show that elastic moduli and yield stresses vary with protein concentration according to a power-law. This power-law dependence is also interpreted in the framework of fractal theories, resulting in fractal dimensions which compare very well with those derived from the light scattering data.