Filtration of lager beer with microsieves: flux, permeate haze and in-linemicroscope observations

Membrane fouling during filtration of lager beer with microsieves was studi ed through in-line microscope observations. It was observed that the main f ouling was caused by micrometre-sized particles, presumably aggregated prot eins. These particles formed flocks covering parts of the membrane surface. Most of the flocks could be removed by a strong temporary increase in cros sflow. Underneath the flocks a permanent fouling layer was formed inside th e pores. This made frequent removal of the flocks crucial in delaying the p rocess of permanent in-pore fouling. Besides the fouling process the influence of pore size on permeate flux and turbidity was investigated. Centrifuged beer appeared to give a significan tly clearer permeate than rough beer. For centrifuged beer and a microsieve with a pore diameter of 0.55 mum a haze of 0.23 EBC was obtained during 10 .5 h of filtration at an average flux of 2.21 x 10(3) l/m(2) h. For a sieve with slit-shaped perforations of 0.70 mum x 3.0 mum a haze of 0.46 EBC was obtained during 9 h of filtration at an average flux of 1.43 x 104 l/m(2) h. This flux is more than two-orders of magnitude higher than is commonly o btained with membrane-filtration of lager beer. Concentration of the beer b y a factor of 12 hardly influenced the magnitude of the flux. (C) 2002 Publ ished by Elsevier Science B.V.