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

Project Code: B02006

31/12/2001

Microchem Bioscience Limited
Millar, I

1.1 Background

Modern 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. Often food processing factories have to conduct an initial clean up of gross dirt and debris, and although this may leave surfaces 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 from viable microorganisms, in particular those microorganisms that can cause food poisoning. Microorganisms such as Salmonella, Listeria, and E. coli are well known to the public as causes of food poisoning, and foodborne illness due to consumption of foods contaminated with these microorganisms can vary from sickness and diarrhoea through to serious health risks to individuals, with the possibility of long term illness, or even death. Thus as well as obtaining surfaces that are visibly clean, food processing operations must disinfect (i.e. sanitise) those surfaces and equipment that come into contact with foods.

Methods used to clean include using diluted detergents, high pressure water hoses, compressed air, steam, cloths, abrasives (manual or mechanical), whilst methods used to disinfect include the use of chemicals (e.g. hypochlorites and other types of chlorine-based chemicals, other proprietary disinfectants), steam and other high temperature/pressure systems. The use of chemical disinfectants can lead to problems, e.g. if the wrong concentration of chemical is used, or if insufficient time is allowed for the chemical to work, or if (through incorrect usage) residues of cleaning and disinfecting chemicals are left on equipment where they can then taint the food, or the danger of using steam in a factory environment, etc. Thus it was decided to investigate the use of blasting dry ice as a means of both cleaning and disinfecting food processing equipment and areas.

1.2 Rationale and Objectives

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 surfaces typically found in food processing operations, e.g. ceramic tiles, stainless steel, food grade plastics.

1.3 Approach

Examples of the types of surfaces used in food processing operations were obtained and deliberately contaminated with cultures of Salmonella enteritidis, Escherichia coli, and Listeria monocytogenes. They were then 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., were optimised to give the greatest possible ‘kill’ effect on these microorganisms.

The Cold Jet system was also tested in an animal feed production facility in order to determine its suitability for use in a food environment (contaminated animal feeds are a significant source of food poisoning microorganisms in foods; Crump et al 2002), and its suitability for decontaminating poultry carcasses and meat portions evaluated.

1.4 Outcome / Key Results Obtained

The Cold Jet system for applying dry ice pellets onto surfaces has been shown to be effective in cleaning and disinfecting various types of surfaces, including stainless steel, ceramic tiles, and food grade plastics and plastic surface coatings.

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 by a factor of 10,000 or more were obtained, and that this was due to the combined application of dry ice pellets and compressed air was shown experimentally.

The parameters for optimum application of the Cold Jet system on surfaces were determined, including diameter of dry ice pellets, pellet flow rate, 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.

Cold Jet was found to be effective in cleaning and disinfecting processing plant after it had received an initial clean to remove gross debris. When Cold Jet was used directly on meat and poultry it did decrease the numbers of microorganisms present, but caused unacceptable tissue damage due to the action of the dry ice pellets and compressed air.

1.5 Conclusions and Possible Future Work

The Cold Jet system has been shown to be effective in cleaning and disinfecting various food grade surfaces. It has a distinct 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. As it stands, the Cold Jet system could be used now to disinfect food processing operations, preferably after an initial removal of gross debris.

The next stage would be to investigate the integration of the Cold Jet system into food processing lines, where certain operations are conducted where a clean and disinfect as-you-go policy is not currently feasible, e.g. poultry defeathering, animal/poultry evisceration, but where there is a high risk of contamination of foods. The Cold Jet system could be built-in as a fixed installation to allow continuous cleaning and disinfection, or else more frequent cleaning and disinfection, of the food processing line.

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