Contribution to the understanding of fouling build-up during microfiltration of wines

The aim of the present study was to investigate the respective impact of wine dissolved constituents, colloids and particles on the fouling of an organic microfiltration membrane. Microfiltration runs with a crude and centrifuged red wine, with model solution of particles recovered from centrifugation and with permeates from microfiltration experiments were thus compared. Particle concentration and size distribution were determined by Coulter-counter analyses while colloidal size-range constituents were evidenced by means of dynamic light scattering (DLS) experiments. Examination of fouling kinetics, along with scanning electron microscopy (SEM) observations of the membrane surface, evidenced that microfiltration performances were governed by colloids and small particles. These constituents induced sharp initial flux declines, related to both internal and external fouling. The evolution of the overall membrane resistance during wine processing was governed by external fouling. It was mainly reversible and attributed to polarisation of the retained species on the membrane front face. In accordance with previous works, a substantial irreversible fouling also developed. Membrane fouling by large particles and permeates set-up in a quite different way. With large particles, fouling developed due to the formation of a coherent cake, which was resistant to re-dispersion. Processing of the permeates led to the formation of a surface cake of aggregated organic matter. These whole results were discussed with the aim to better understand mechanisms implied in the fouling build-up during microfiltration of wine. (C) 2002 Elsevier Science B.V. All rights reserved.