Managing the control of listeria in a wet processing environment

Steve Tsuyuki (tsuyukst@mapleleaf.ca) of Maple Leaf Consumer Foods and John Weisgerber (jcweisgerber@gmail.com) of Weisgerber Consulting LLC contributed this article.

Efforts to manage ready-to-eat (RTE) meat processing environments and prevent the recontamination of cooked products with Listeria monocytogenes have led most in the meat processing industry to the conclusion that "dryer is better." In fact, there is a "formula" available though the American Meat Institute Listeria Intervention training course that describes the multiple controls needed. It is:

Listeria control = Controlled traffic patterns + dry, uncracked and cleanable floors + effective GMP's + sanitary design of equipment and facility + effective sanitation procedures

Wet environments have three obvious symptoms that could lead to problems:

1. Condensation on overhead structures will create a Listeria risk for exposed product or equipment food contact surfaces.
2. Wet floors will facilitate the transfer of Listeria from a source zone to the food contact surfaces via traffic flows.  
3. Wet floors will create harborage sites (if cracked). By definition, this means that even when a cracked floor is chemically sanitized, Listeria will remain protected by the interstitial water between floor layers.

In many plant processes, certain operations are inherently wet, such as product debagging, loaf knock-out or wiener peeling. In these cases the best that can be done is to control the environment (people and equipment traffic), minimize aerosol generation to the greatest extent possible, and remediate known harborage areas. Some considerations are:

• If water washing is required during operations, use only low-pressure, cold water. This should not be done if adjacent areas are operating. It is also best to perform a flood sanitation step before operations resume if mid-shift cleaning is required. A best practice would be to find alternate methods to perform changeovers that reduce water usage.
• If condensation forms above food contact surfaces, remove it with sanitized wipers before product contact surface are contaminated.
• If product is on wheeled racks, splash guards over the wheels should be installed and product should not be placed on the lowest level of the rack. Clean racks between each use. Identify each rack so when racks are environmentally tested, a positive finding can be traced back to the specific rack for remediation. 
• Do not let standing water form where there is employee traffic or product staging. Remove it with sanitized squeegees directly to a drain.
• Maintain intact unbroken floor coatings. Broken flooring allows water to collect in areas that cannot be cleaned and creates an excellent harborage site.
• Equipment generating water should be connected directly to a drain to avoid water spilling on the floor.
• All equipment must have a periodic intervention developed. For example, peelers should be cooked or steamed in place, as recommended in the AMI Listeria Intervention training program, on a routine frequency (monthly or more often if data proves it is necessary) if they cannot be totally disassembled for cleaning. Hand tools should be cooked weekly to manage harborage sites in the plastic handles. Tables, racks or other equipment with hollow legs should be tent steamed or cooked in a smokehouse until they can be replaced.

Drying out a processing area that had been operated in a wet state (for as long as people could remember) is a big paradigm shift that takes a significant amount of leadership and effort to complete. One plant took on this challenge after months of persistent Listeria environmental positives. The paradigm shift was initiated by management with the goal of eliminating Listeria in the RTE area. Several actions were taken, including:

• Aggressively drying out the floors:
• Eliminated ALL water sources that made the floor wet, such as sterilizing hot water pots and equipment cooling water hoses that drained onto the floor.
• Installed an air desiccant system.
• Stopped all wet mid-shift cleanups.
• Kept the floors dry.
• Condensation and ceiling drips became obvious on the dry floor and were quickly traced to source and corrected.
• Empowered front-line employees embraced the changes since the commitment to food safety by management was visible. A dry environment is also safer to work in, as slips and falls are reduced.

American Meat Institute Training Material January 2010

Tompkin, R.B. 2002 Control of Listeria monocytogenes in the Food-Processing Environment, Journal of Food Protection, Vol. 65, No.4, pages 709-725