New insights on the formation of colloidal whey protein particles

This paper describes the formation and properties of whey protein particle suspensions having different particle sizes and different abilities to form S–S bridges. Simple shear flow was used to control the protein particles size. The ability to form S–S bridges was steered by blocking the reactive thiol groups of the whey proteins with N-ethylmaleimide. Microscopy and light scattering showed that simple shear flow applied during the formation of whey protein particles give irregularly shaped particles. Especially small particles aggregated into particle clusters. Microscopy and rheological measurements (strain and shear rate sweeps) showed that the protein particle clustering was favoured by the ability of the protein to form S–S bridges and to a lesser extend by a smaller particle size. From the study, it can be concluded that the formation of S–S bridges has no effect on the formation process of protein particles, but S–S bridges are important for the ability of the whey protein particles to form particle clusters.