Particles deposition during the cross-flow microfiltration of red wines-incidence of the hydrodynamic conditions and of the yeast to fines ratio

The aim of the present study was to investigate the respective impact of wine particles, i.e. Saccharomyces cerevisiae yeast and fines (lactic bacteria and colloidal aggregates), on the performances of cross-flow microfiltration under different permeate flux rate/wall shear stress conditions. Yeast were grown in a synthetic red wine and their surface properties characterized. The cells exhibited a hydrophilic character and were uncharged in the wine conditions. Yeast and fine behaviors were first investigated separately and then compared to that of their mixture. The shear induced diffusion theory well accounted for the whole evolution of the performances under the application of different hydrodynamic conditions. These performances were related to the deposit structure, which reversibility was experienced by alternating high and low TMP steps, and by SEM observations of the membrane surface. Yeast alone always formed reversible deposits, in relation with their surface properties. By contrast, fines formed a coherent and adherent cake above a given TMP. When yeast and fines were processed together, the TMP stepping mode strongly influenced the composition, final resistance and reversibility of the deposit.