This paper presents the first part of our study on ultrafiltration (UF) of polyphenolic compounds which is relevant to many industrial food and beverage feed streams. Two commercial polyethersulfone (PES) membranes with different cut-off (10 and 100 kg/mol) and one stabilized cellulose (cellulosic) membrane (10 kg/mol) were used. Membrane-solute interactions (adsorptive fouling) and membrane-solute-solute interactions (UF fouling) as well as the effects of pH, foulant concentration and ionic concentration of the solution on fouling were investigated in order to elucidate the fouling mechanism. Significant water flux reductions and changes in membrane surface properties were observed after static adsorption for all membranes. The possible mechanisms for the attractive interactions between polyphenolic compound and membrane are discussed. Results from UF experiments indicate that both reversible and irreversible fouling have contributed to the overall fouling. (C) 2008 Elsevier Ltd. All rights reserved.