Matching the nano- to the meso-scale: measuring deposit–surface interactions with atomic force microscopy and micromanipulation

Many researchers have studied the effects of changing the surface on fouling and cleaning. In biofouling the 'Baier curve' is a well-known result which relates adhesion to surface energy, and papers on the effect of changing surface energy to food fouling can be found more than 40 years ago. Recently the use of modified surfaces, at least at a research level, has been widespread. Here two different ways of studying surface-deposit interactions have been compared. Atomic force microscopy (AFM) is a method for probing interactions at a molecular level, and can measure (for example) the interaction between substrate and surfaces at a nm-scale. At a μm-mm level, we have developed a micromanipulation tool that can measure the force required to remove the deposit; the measure incorporates both surface and bulk deformation effects. The two methods have been compared by studying a range of model soils: toothpaste, as an example of a soil that can be removed by fluid flow alone, and confectionery soils. Removal has been studied from glass, stainless steel and fluorinated surfaces as examples of the sort of surfaces that can be found in practice. AFM measurements were made by using functionalized tips in force mode. The two types of probe give similar results, although the rheology of the soil affects the measurement from the micromanipulation probe under some circumstances. The data suggests that either method could be used to test candidate surfaces

Populating the cleaning map: can data for cleaning be relevant across different lengthscales?

AbstractOne of the major challenges in minimising the environmental impact of food processes is minimising the waste and cost associated with cleaning. Cleaning is necessary because of the rapid formation of fouling deposit inside process plant and the need to changeover between products. We have recently [1] suggested a classification of cleaning in which the costs of cleaning are mapped against the types of deposit. The aim of this work is to identify how to relate the cleaning of one material to that of another, since at present the design of cleaning processes is largely empirical. A series of experimental studies are described in which the cleaning of three types of deposit are studied to identify the critical factors which in each case lead to a finally clean surface. Suggestions for the development of the work are given