DE3936798

The invention relates to a microfiltration process, in particular for separating beer from a materials flow which is purged during the fermentation process and which takes along the excess yeast produced during the fermentation, wherein the materials flow containing haze substances to be filtered is passed under pressure through at least one microfiltration module with porous membranes carrying a tangential flow and a filtrate is taken off. According to the invention, the materials flow to be filtered is continuously fed to a circulated retentate flow, and a concentrate flow having a substantially constant concentration of haze substances is taken off from the retentate flow. The flow velocity and the flow pressure drop of the retentate flow are measured and the concentration of haze substances in the retentate flow is determined from the measured data according to a function F (v, DELTA p) which is characteristic of the apparatus and which contains the flow velocity (v) and the flow pressure drop ( DELTA p) as variables. The concentrate flow rate is controlled in accordance with the difference in the concentration of haze substances, resulting from a comparison of actual and set values.