Flux Decline in Microfiltration of Beer and Related Solutions of Model Foulants through Ceramic Membranes

Clarification and stabilization of beer as well as recovery of beer from surplus yeast are subjects of great interest. Microfiltration through ceramic membranes could address both these applications if the economy of this process is improved. The aim of the present work was an experimental study of the flux decline in cross flow microfiltration of the filtered beer and aqueous solutions of model foulants. Ceramic membranes with two mean pore sizes of 200 and 500 nm were used. The used microfiltration stand enabled the cleaning of the membrane by back-flushing with the permeate. For better understanding of the fouling process and for identifying of the fouling capacity of individual foulants, the runs were conducted with aqueous solutions of selected model foulants as a- and β-amylase, catechin, commercial α-bitter acids, mixture of maltose and sucrose and washed beer yeast suspension. The concentration of the model foulants was similar as in beer. The suspension of the purified beer yeast (four times washed yeast with a physiological solution) was studied as well. A rapid flux decline was observed during the first two-three minutes. The membrane with larger pores, of 500 nm, exhibited lower steady flux than the more dense membrane with 200 nm pores. Repeated rinsing of the fouled membrane with water after microfiltration recovers only a small part of the initial flux. The order of model foulants with increasing flux decline capacity is: mixture of maltose and sucrose < amylase <pure beer yeast < α-bitter acids < catechin