Wet foam flow: A suitable method for improving surface hygiene in the food industry

Abstract

In the food industry, the cleaning of contaminated surfaces requires new strategies to be adopted which can provide greater cleaning efficiency with minimal energy and water consumption. The use of wet foams was proposed to clean stainless steel surfaces contaminated by droplets containing Bacillus spores. Methods such as polarography, conductimetry and foam structure identification were used. Foam flow conditions with varying wall shear stresses and bubble sizes were observed to measure their impacts on surface contaminant removal kinetics. Compared to conventional cleaning-in-place method, foam flow more effectively removed both hydrophilic and hydrophobic spores. The combination of high shear stress and small bubble sizes (<0.2 mm) showed promise for improving the cleaning efficiency of the foam. Mechanisms such as fluctuation in local stresses, or in the liquid film thickness between the bubbles and the steel wall induced by bubble passage, foam imbibition and liquid film drainage were then investigated.