Fouling in microfiltration of wine: The influence of the membrane polymer on adsorption of polyphenols and polysaccharides

Microfiltration (MF) is a frequently used to clarify wine, but the fouling of the membranes is the main limiting factor for the overall process capacity. In this work, data from MF clarification of a white wine are presented which show that membranes made from polypropylene (PP) yield significantly higher fluxes and through-put than membranes made from polyarylsulfone, both having the same cut-off pore size (0.2 μm). The aim of this study was then to pursue the hypothesis that different membranes (based on PP or polyethersulfone, PES) exhibit different levels of adsorption of typical foulants in wine such as polyphenols and polysaccharides, to link the level of adsorption to polymer characteristics and to correlate membrane fluxes with these findings. A model solution for wine (“synthetic red wine”) has been established by using a commercial red grape marc extract (from grapes after fermentation). It was found that polyphenols and polysaccharides are only marginally adsorbed by PP but strongly adsorbed by PES membranes. Comparison between data for individual model substances for polyphenol or polysaccharide and their mixtures with data for “synthetic red wine” support the hypothesis that aggregates of polyphenols and polysaccharides present in red wine have a strong contribution to adsorptive fouling, and that the interaction between polyphenols and the membrane surface is the main driving force. In consequence, the low adsorption tendency of wine ingredients to PP membranes results in higher fluxes and longer service life of the respective filtration modules in wine clarification.