Impact of different aqueous phases on casein micelles: Kinetics of physicochemical changes under variation of water hardness and diafiltration conditions

Besides deionised water, tap or softened water could be used as diafiltration media for separation and purification of the casein fraction from milk by means of membrane technology. The effect of compositional differences on key properties of casein micelles was investigated with these media and simulated milk serum as reference at laboratory scale under conditions mimicking typical industrially applied diafiltration processes. Evaluation of zeta-potential, particle size distribution, voluminosity as well as casein and calcium composition revealed marked differences of micellar attributes at temperatures of 10 and 50 °C depending mainly on the medium hardness. While tap water induced a slight micellar contraction, dehardened water types differently fostered a swelling that was followed by partial disintegration over contact time especially at 50 °C. Results demonstrate that water composition impacts micellar properties in typical DF conditions, which can, in consequence, be crucial for processing efficiency and product functionality of obtained casein products.