Identification of cohesive and adhesive effects in the cleaning of food fouling deposits

Abstract Cleaning of process plants is costly and time consuming. It is important to understand the removal of fouling deposits. Deposits form by adhesion to the surface and cohesion between elements of the deposit. Cleaning can result from either or both adhesive and cohesive failure. Micromanipulation experiments have measured the adhesive/cohesive strength of deposits in terms of the work required to remove them from the surface. Different food deposits have been studied. Tomato paste, bread dough and egg albumin deposits have a lower adhesive than cohesive strength, whilst others (whey protein) have a lower cohesive than adhesive strength. A range of coated surfaces has been used to study the effect of surface energy on the force required for removal of tomato deposits. Minima are found, as predicted by theory. A simple material model has been developed and used to analyse the results in terms of the work required to remove the deposit per unit surface area and volume. Industrial relevance Cleaning is a ubiquitous and poorly understood operation in the food industry. Poor cleaning endangers product safety, lowers run length and generates excess effluent. Better understanding of the processes of cleaning is beneficial both in ensuring food safety and in increasing the manufacturing efficiency of process plant.