Milk protein fractionation by spiral-wound microfiltration membranes in diafiltration mode - Influence of feed protein concentration and composition on the filtration performance

Washing steps by adding diafiltration medium are needed to completely fractionate caseins and whey proteins from skim milk by microfiltration. The amount of diafiltration medium and the fractionation performance depend on the feed concentration factor (CF). However, an investigation on the optimum process conditions during fractionation by spiral-wound membranes (SWMs) has not been carried out yet. At the optimum transmembrane pressure, CF 2 performed best with regard to the whey protein mass flow. The protein concentration in the permeate and the flux were limiting factors at lower and higher CFs, respectively. Regarding industrial plants with multiple stages for the fractionation, the casein to whey protein ratio varies in each stage. Since no changes in the length-dependent filtration behaviour was observable with the casein to whey protein ratio at a constant axial pressure drop, the optimisation of SWMs regarding length dependency can be conducted independently of the stage.