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

Abstract

To assess the potential of Magnetic Resonance Imaging (MRI) as a method of detecting water movement during the extrusion of pastes. Plug samples were made from mixtures of model materials and microcrystalline cellulose with two water contents at two different ram speeds to simulate ram extrusion. The extrusion process was stopped at different stages and analyzed for water distribution using MRI to assess the influence of water content and the speed of ram on water movement as the extrusion process progresses. Two types of water movement were detected: vertical and radial. When extruding at the faster ram speed, water moved predominantly in the vertical direction, whereas when extruding at a slower ram speed it moved predominantly in the radial direction. At the beginning of the extrusion process a greater water movement in the wetter formulations was observed. MRI appears to be a useful approach to non-invasive water mapping, and is expected to contribute towards a greater understanding of the role of water in the extrusion of pastes.