The rinsing step, in which yoghurt is displaced by water, was monitored in a dairy plant using electrical resistance tomography (ERT), with a new hygienic design of the ERT sensors. The same displacement situation was simulated using computational fluid dynamics (CFD) and showed good agreement with the ERT measurements. CFD was also used to study how different properties, such as flow velocity, wall slip and the rheological properties of the yoghurt, could change the effectiveness of rinsing. (c) 2006 Elsevier Ltd. All rights reserved.