Amajor food-safety concern is back in the news, the recontamination of ready-to-eat (RTE) foods or foods already cooked after processing has taken place. The pathogen once again largely responsible for this recontamination is Listeria monocytogenes (Lm). It can cause a disease called Listeriosis that is particularly dangerous to infants and young children, pregnant women, the elderly and people with weakened immune systems.

RTE products susceptible to Lm, which can survive even in cold refrigerated environments, include lunch meats, hot dogs, spreads and salads, large-diameter sausages, uncured cooked poultry, jerky and roast, corned and cooked beef.

While USDA has recommended the re-cooking of RTE products or treatment with antimicrobials to prevent these products from becoming recontaminated by Lm, there is another important step to keep Listeria monocytogenes out of meat and poultry processing plants altogether – operating a complete cleaning and sanitation program.

Dr. Catherine Cutter, associate professor and food-safety extension specialist in the Department of Food Science at the Pennsylvania State Univ., acknowledges it may be hard for some plants to control pathogens by investing in new, sanitary design of processing equipment. “Unfortunately, small and very-small plants don’t always have money to invest in new equipment; they’re often using equipment that may have been around the plant for quite some time, or equipment they buy from someone else,” which may have been rolled out before the era of sanitary design. “Lm lurks in many plant harborage sites. Luckily, frequent sanitation and cleaning in the plant assume a much higher level of importance and can play a major role in removing pathogens like Lm,” she says.

A great challenge
Cutter says the challenge becomes greater because some of the postcooking product contact surface areas can become contaminated by Lm including saws, dicers and slicers, shelves, containers, casing peelers, hand tools, packaging equipment, conveyors, and tables if used for raw products and not sanitized properly – and cleaning equipment itself.
There are several potential sources of Lm contamination in meat and poultry processing plants, including the employees and their clothing, and the environment, including airborne bacteria from other work areas. But the main source probably is improperly cleaned and sanitized equipment. (Please see Page 52 of the August 2010 edition of Meat&Poultry for cleaning tips.)

She points out some particular reservoirs of Lm, especially in small processing plants, include floors and drains, ceilings and overhead pipes, standing water in a plant, refrigeration units, cleaning tools, overhead rails, forklifts and pallet jacks, maintenance tools and wood pallets.

Once an RTE product is cooked properly, manufacturing a safe product depends on proper sanitation, limited handling of the product and elimination of cross-contamination in the RTE processing areas.

“Slicers are a huge problem. They’re sharp; crews don’t like to break them apart, especially making sure the blades are clean,” Cutter says. “In fact, any space you can get a piece of paper into, that’s a place for bacteria and other pathogens to hide.” •

Bernard Shire is a free-lance writer based in Lancaster, Pa. He also works as a food safety consultant and writer for Shire & Associates.

M&P’s Sanitation Tips are to be used only as guidelines for cleaning and sanitizing processing facilities. Specific issues and questions should be addressed to a sanitation crew supervisor.