Identification and modelling of different removal modes in the cleaning of a model food deposit

All food process plant must be cleaned to ensure hygienic operation, but cleaning is not well understood. Micromanipulation probes have been developed which can measure the force required to disrupt and remove deposits from surfaces. Here, the forces required to remove a tomato paste deposit at different heights xx from the surface have been measured. At small xx, the work needed to remove the deposit increases with height and is a function of the nature of the surface, whilst at larger xx the work needed decreases with increasing xx and is not a function of the surface. Two simple models have been developed which fit the data and observations of cleaning; these are based (i) at small xx, on the fracture of the deposit and motion across the surface, and (ii) at larger xx, on the fracture of deposit–deposit bonds and removal of a uniform layer.