First insights into changing cleaning mechanisms based on experimental and numerical investigations

Abstract

Cleaning is a crucial process step within food production, as it has a major impact on food safety and involves considerable resource consumption. There are various approaches to optimize cleaning processes, e.g., i) cleaning experiments on laboratory scale, ii) specific soil characterization methods on laboratory scale and iii) cleaning simulations. This paper shows for the first time how all three methods are combined to understand and model complex behavior during cleaning. To this end, removal of dried ketchup soil layers was studied using aqueous sodium hydroxide at various concentrations (0 – 2 wt%) and temperatures (20 – 55 °C) as cleaning fluid. In cleaning experiments, significantly shorter cleaning times are measured when cleaning is performed with hot 2 wt% sodium hydroxide solution (69 s) instead of pure water at room temperature (167 s). Counterintuitively, micromanipulation and rheological measurements of the soil layer show a solidification when in contact with sodium hydroxide as opposed to water. It is found that this is due to a change of the cleaning mechanism from pure adhesive detachment to combined cohesive separation of an interlayer, followed by adhesive detachment of the remaining soil. A recently developed cleaning model is extended to capture the ongoing phenomena. The model is able to predict the cleaning time correctly with errors smaller than 10 %.