Optimization of temperature for effective cleaning with a novel cleaning rig: Influence of soil and surface types

Abstract

The effect of temperature, soil and surface type on cleaning performance was investigated using newly developed cleaning rig in which the flow characteristic of cleaning solution was a falling film generated by impinging jet. The most common types of foods in dishwashers (spinach, egg yolk, milk, potato puree, minced meat, black tea, and margarine) were studied as soils and the main materials used in household utensils such as stainless steel, glass, porcelain, and plastic were tested as cleaning surfaces. The physicochemical properties of food components and surfaces had a major role in the development of soil-soil associations and the soil-surface interfacial interactions. It was observed that the strength of those interactions was determinant factor of soil removal mechanism which could be resulted in either by cohesive failure or both adhesive and cohesive failure. Regardless of soil type, when the temperature increased, better cleaning scores were obtained since the cleaning solution easily penetrated into soil which led to swelling of soil and reducing interfacial forces. Cleaning performance of soils was modeled using the results of 140 experimental points in Response Surface Methodology (RSM). The optimum temperature was determined for all surface-soil combinations as 56 °C, at which the cleaning scores were the closest to the cleaning performance at 70 °C. Moreover, it was observed that the experimental results of the cleaning at the optimum temperature were similar or better than the values estimated with the model. This study would be useful to develop an understanding on governing factors of cleaning which can be used in optimization of the cleaning process for energy efficient dishwashers.