Physical Methods for Cleaning and Disinfection of Surfaces

Cleaning and disinfection are important operations in food processing because of the significant contributions to product hygiene and food safety. The transfer of residues from surfaces into a product and the contamination with adhering microorganisms must therefore be avoided with sufficient certainty. Traditional methods for the removal of adherents and inactivation of microorganisms are based on thermal, mechanical, or chemical principles and are known to be time- and energy-consuming. This has resulted in a search for alternative methods that show prospective potential for their use in food-processing plants. This review gives an overview on such methods, which are based on physical principles. In dry-ice cleaning, for example, carbon dioxide snow pellets are blasted onto a surface to remove adherents through a combined action of thermal and mechanical effects, followed by dissolution of these adherents. Ice-pigging is a procedure where an ice/water mixture is forced through pipes, heat exchangers, or other equipment to carry off adhered substances. Another method for physical cleaning, mainly described in context with membrane filtration, is to use vibration in the ultrasonic frequency domain to reduce fouling and to stabilize permeate flux. Radiation from various sources (UV lamps, radionuclides, X-ray tubes) differs in its applicability and disinfection efficiency because of differences in energy and penetration depth. Cold plasma treatment is another promising technology that is currently under investigation for cleaning and disinfection of surfaces of inorganic and organic materials.