Ultrafiltration (UF) of sugarcane juice with polysulphone (PS)/poi yethersul phone (PES) membranes is characterized by significant fouling. In our earlier work, a high molecular weight (HMW) component in the juice polysaccharide fraction was observed to interact with the membrane surface. This study focuses on understanding the polysaccharide fouling using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Further, the HMW component in the polysaccharide was isolated and characterized by FTIR and nuclear magnetic resonance (NMR) spectroscopy. The HMW fraction appears to contain arabinogalactan protein, along with phenolics and some lipids. Analysis by the resistance-in-series model indicated cake fouling to be the dominant mechanism. (c) 2007 Elsevier B.V. All rights reserved.