Protein fouling in microfiltration has a large impact on the permeate flux and observed retention of the proteins despite the fact that the protein molecule is several times smaller than the average pore size in microfiltration membranes. This is due to adsorption and deposition of protein molecules and aggregates. The effect of membrane configuration upon protein fouling was investigated in crossflow filtration with asymmetric membranes either in a normal mode or in a reverse mode. It was observed by Jonsson et al.  that beer filtration in a reverse mode results in a smaller decrease in the flux compared to beer filtration in a normal mode. Similar results for protein filtration were observed by Bowen et al. . One possible way to avoid fouling is the novel backshock technique (see Jonsson et al. ). The effect of backshock on protein filtration was investigated using a hollow fiber module.