Membrane fouling during microfiltration of fermented beverages

Microfiltration is considered to be a promising alternative to the traditional fining methods in the food industry. Unfortunately, the efficiency of this process is hindered by membrane fouling, which is mainly caused by the colloidal constituents of the filtered media. For this reason, the use of microfiltration as a fining method is limited. Previous studies have mainly focused on membrane fouling caused by simple model solutions, and do not take into account the complexity of systems of biological origin. The aim of this work is to study how the initial characteristics of two fermented beverages (two wine and two beer samples), as well as the presence of macromolecular fractions with a molecular weight >100 kDa, affect the kinetics of membrane fouling. The microfiltration experiments were carried out in a stirred cell using 0.2 mu m cellulose acetate and polycarbonate membranes under constant pressure and agitation. The experiments with raw beer and wine assessed the influence of the initial characteristics (macromolecular concentration and turbidity) on membrane fouling, while experiments with beverages that had previously been micro- and ultrafiltered assessed the influence of the particles, molecule aggregates, cell debris and macromolecular fractions with a macromolecular weight >100kDa. The results indicate that differences in the fouling of the two raw beer samples studied (B1 and B2) may be due to their initial macromolecular concentration, since the initial turbidity of the two beer samples was similar, while their initial macromolecule concentration was different. The different fouling behavior shown by the two raw wine samples studied (W1 and W2) may be due to their initial degree of turbidity, since their initial macromolecular content was similar. A micro- and ultrafiltration treatment of W2 wine reduced its turbidity to the same levels as raw W1 wine and this led to a reduction in total resistance. However, the final total resistance of treated W2 wine was still much higher than that of raw W1 wine. The difference in the final total resistance may be due to the different polyphenol concentrations of the two wine samples. (C) 2000 Elsevier Science B.V. All rights reserved.