Magnetic resonance imaging (MRI) as a method to investigate movement of water during the extrusion of pastes

Purpose. To assess the potential of Magnetic Resonance Imaging (MRI) as a m ethod of detecting water movement during the extrusion of pastes. Methods. Plug samples were made from mixtures of model materials and microc rystalline cellulose with two water contents at two different ram speeds to simulate ram extrusion. The extrusion process was stopped at different sta ges and analyzed for water distribution using MRI to assess the influence o f water content and the speed of ram on water movement as the extrusion pro cess progresses. Results. Two types of water movement were detected: vertical and radial. Wh en extruding at the faster ram speed, water moved predominantly in the vert ical direction, whereas when extruding at a slower ram speed it moved predo minantly in the radial direction. At the beginning of the extrusion process a greater water movement in the wetter formulations was observed. Conclusions. MRI appears to be a useful approach to non-invasive water mapp ing, and is expected to contribute towards a greater understanding of the r ole of water in the extrusion of pastes.