The Ionic Silver Lining

Bacterial contamination of plant surfaces is a constant concern for the food processing industry. One specific bacteria, Listeria monocytogenes, accounts for 2,500 cases of illness and 500 deaths annually in the U.S., making it the bacteria of greatest concern for ready-to-eat (RTE) processors today. In 1998, one of the largest outbreaks of Listeria occurred with a large U.S. hot dog manufacturer and resulted in 15 adult deaths, six stillbirths and more than one million pounds of product recalled from the market.

In June 2003, USDA imposed a new rule to reduce Listeria in RTE meat and poultry products. The regulations encourage RTE food processing facilities to employ more effective Listeria control measures and require the facilities to verify the effectiveness of these measures through testing and sharing the results with the Food Safety and Inspection Surface (FSIS).

While USDA reports that these new regulations are having a positive impact on the reduction of Listeria in RTE food products, Listeria outbreaks continue to place the public at risk and result in costly production interruptions, plant shutdowns and significant economic losses. In the past two months, four U.S. companies were forced to recall countless quantities of sausage, sausage and chicken gumbo, chicken salad, ground beef patties, and meatballs due to possible Listeria contamination.

While plant operators and sanitation professionals employ every weapon in their arsenal of cleaning tools to control bacterial proliferation and transmission, new solutions must be developed to assist them in their efforts to keep surfaces clean and reduce the risk of food product contamination.

Floors Foster Contamination

Studies have shown that surfaces in food processing facilities – particularly floors – can harbor and transmit a variety of problem-causing bacteria, including Listeria, and increase the risk of food product contamination. Bacteria are well adapted to food processing environments since they can grow and reproduce in damp, low oxygenated, refrigerated conditions.

High foot and vehicle traffic, the movement of heavy equipment, and cleanings with hot water and harsh chemicals can cause severe damage to a floors. Damaged flooring is an ideal breeding ground for problematic bacteria since it provides a dark, damp refuge that is impervious to commonly employed cleaning techniques, such as disinfectants and sanitizers. Bacteria can live for hours¬ – or even days ¬– within the pits and crevices that can form on a floor’s surface from every day wear and tear.

Last year, researchers from the University of Wisconsin at Madison conducted an audit of 31 RTE meat and poultry processing plants to determine where Listeria contamination was a problem in post-lethality environments. As part of the study, 438 food contact and non-food contact surfaces were sampled for the presence of Listeria. The audit revealed a particularly high incidence of Listeria on floors and drains. Of the 115 floor and drain samples that were taken from these facilities, 27.8 percent tested positive for the bacteria.

When bacteria exist within the cracks and crevices of plant flooring, they are continuously exposed to small amounts of cleaning products without being killed. As bacteria grow and reproduce over time, they develop into organized and structured communities that are highly resistant to cleaners, sanitizers and disinfectants.

Researchers at the University of Georgia conducted a study to assess the ability of Listeria to survive exposure to commercial food processing equipment, cleaning solutions and subsequent treatment with sanitizers or heat. They found that Listeria can not only tolerate exposure to high concentrations of alkaline cleaning solutions, but also develop a resistance to these cleaners.

Studies have also revealed that bacteria commonly found in food processing environments are incredibly resilient. Bacteria starved of nutrients for extended periods of time have the ability to “wake up,” restore their own strength and effectively kill other cells, even if it takes them a bit longer to do it compared with healthy cells.