Effect of agitation intensity during the formation of whey protein aggregates on breakage rate under subsequent turbulent flow transportation

The flow field characteristics during the formation of aggregates and floes have a major influence on particle size, microstructure and strength. It was found that aggregates formed under different agitation speeds have different breakage rates when they are subjected to comparatively high levels of turbulence as they are transported via pipeline during post- formation processing. Protein aggregates formed at different impeller speeds were propelled through a straight pipe at different flow velocities (turbulent flow). The dispersions were recycled several times to study the particle size reduction along with exposure time. Particles formed at lower agitation have higher breakage rates, especially during the initial recycles than those formed at higher agitation, although the apparent "stable" size (particle diameter after extended exposure times when very little size reduction is observed) is bigger for particles formed at lower agitation. As breakage occurs the aggregates lose their fractal nature and a strong core is revealed. It is suggested that particles with a larger core are formed at low agitation. A breakage model relating particle size reduction to energy dissipation rate within the pipe is proposed.