B02006: Cold Jet - A novel technique for cleaning and decontaminating food processing areas, equipment, carcasses and foods.

Study Duration: February 1999 to January 2002

Contractor: Microchem Bioscience Limited

Modern food operations use a variety of methods for cleaning and disinfecting surfaces and equipment which comes into contact with foods during handling and preparation. Often food processing factories have to conduct an initial clean up of dirt and debris, and although this may leave surface and equipment looking clean, this does not disinfect those surfaces. Cleaning and disinfection in food processing operations go hand in hand, as a visibly clean surface may not be free of microorganisms, in particular those micro-organisms that can cause food poisoning. Microorganisms such as salmonella, listeria and E. coli are well known to the public as causes of food poisoning. Foodborne illness due to consumption of foods contaminated with these micro-organisms can vary from sickness and diarrhoea through to severe illness, with the possibility of long term illness or even death. Thus, as well as obtaining surfaces that are visibly clean, food-processing operations must be disinfect those surfaces and equipment that comes into contact with foods.

Methods used for cleaning include using high pressure water hoses, compressed air, steam, cloths and abrasives, whilst methods used to disinfect include the use of chemicals (e.g. bleach), steam and other high temperature/pressure systems. Chemical disinfectants may not be effective if incorrect concentrations are used or insufficient time is allowed for the chemical to work, etc. Thus it was decided to investigate blasting when dry ice as a means of both cleaning and disinfecting food processing equipment and areas.

The means of applying dry ice to food processing surfaces was the Cold Jet system, a patented system for dispensing pellets of dry ice by mixing them with compressed air and blasting them from a nozzle at carefully controlled rates. The objectives were to determine whether the Cold Jet system could both clean and disinfect the types of surface typically found in food processing operations, e.g. ceramic tiles, stainless steel, food grade plastics.

Examples of the type of surfaces used in food processing operations will be obtained and deliberately contaminated with cultures of Salmonella enteritidis, Escherichia coli and Listeria monocytogenes. They will be blasted with dry ice pellets using the Cold Jet system. Various parameters of the Cold Jet system such as air flow rate, blast pressure, dry ice pellet flow rate, etc will be optimised to give the greatest possible 'kill' effect on these microorganisms.

The Cold Jet system will be tested in an animal feed production facility in order to determine its suitability for use in a food environment and its suitability for decontaminating animal carcasses and food evaluated.

Food processing operations use a variety of methods for cleaning and disinfecting surfaces and equipment which come into contact with foods during handling and preparation.

Surfaces used in food processing operations were contaminated with micro-organisms and then blasted with dry ice pellets using the Cold Jet system. Various parameters were assessed to determine the best decontamination method.

The Cold Jet system effectively decontaminated surfaces of Salmonella enteritidis, Escherichia coli and Listeria monocytogenes such that these microorganisms were not detectable using conventional microbiological methods after a defined Cold Jet treatment. Decreases in target bacterial populations of four orders of magnitude or more were obtained, and this was due to the combined application of dry ice pellets and compressed air.

The parameters for optimum application of the Cold Jet system to surfaces were determined, including diameter of dry ice pellets, pellet flow rates, blast pressure, air flow rate, blasting time (time of application of dry ice pellets to surfaces).

Some surfaces were found to be either too brittle or too fragile for the application of the Cold Jet system, e.g. certain grades of plastics changed shape and appearance, or cracked or peeled, but the majority of food grade plastics tested withstood the treatment.

The Cold Jet system has been shown to be effective in decontaminating and disinfecting various food grade surfaces. It has an advantage over conventional cleaning and disinfection techniques in that there are no chemical residues left behind after treatment, and no chemical wastes to treat and dispose of. Further investigation is required to integrate the Cold Jet system into food processing lines.

Final report is available from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk,
Dr Elsie Widdowson Library and Information Services, Food Standards Agency, (tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk).

Contact: For any enquiries concerning this research project, please contact the relevant Programme contact or email science@foodstandards.gsi.gov.uk