Performance of a Graesser contactor in the continuous extraction of whey proteins: mixing, mass transfer and efficiency.

The performance of a Graesser Raining Bucket Contactor in an extraction using aqueous two-phase systems was characterized by axial mixing coefficients and counter current mass transfer for whey protein purification. The influence of rotor speed, phase ratio and phase velocity on the salt phase axial mixing coefficients was determined applying a dispersion model to the residence time distribution experiments. When dissolving whey powder in the salt-rich phase of the system, alpha-lactalbumin was extracted to the polyethylene-glycol-rich phase, whereas beta-lactoglobulin predominantly remained in the bottom phase, making the process suitable for removal of the major allergen beta-lactoglobulin. The mass transfer in the phase system was determined from the steady state data of alpha-lactalbumin extraction. On the basis of a diffusion model, the efficiency of the counter current extraction under different process conditions was calculated from results of the mass transfer experiments.