Whey protein aggregation under shear conditions – effects of lactose and heating temperature on aggregate size and structure

Whey protein concentrates with different lactose contents were heat- and shear-treated in a scraped surface heat exchanger at various temperatures. The properties of the resulting protein aggregates are closely correlated with the denaturation kinetics of β-lactoglobulin and the different mechanisms – unfolding and aggregation – which determine the overall reaction rate. At temperatures below 85 °C, unfolding is slowed down especially if there is a high content of lactose. A loose, porous aggregate structure is formed and the particle size and the serum binding capacity increase. The smallest aggregates are produced when heating takes place between 85 and 95 °C. In the temperature range above 100 °C aggregation is the rate-limiting step and the aggregate structure is very dense and compact. The particle size increases and is no longer dependent on the concentration of lactose.