The Ionic Silver Lining

Researchers at the University of Arkansas starved Listeria cells for 196 days and then tested their effectiveness in killing a target population of mouse cells. While healthy Listeria cells effectively killed 90 percent of the target mouse cell population within two hours, the starved and damaged cells had the strength to kill 60 percent of the population within six hours, and 90 percent within eight hours. Based on these results, the researchers concluded that inadequate disinfecting procedures could leave some bacteria alive and virulent with the ability to regroup and contaminate.

Even if conventional disinfectants and sanitizers are used to successfully eradicate Listeria and other bacteria on floors and below the surface, they cannot control bacterial populations over an extended period of time. Conventional cleaners are based on an “instant kill” approach. When sprayed or wiped onto a surface, they kill existing microbes but do little to combat new microbes that can build up during daily use. For instance, a disinfectant could kill bacteria on a plant floor, but as soon as someone walks across that floor with shoes carrying Listeria or other problematic microbes, it is contaminated again.

Additionally, many commonly used disinfectants are only effective if they remain on a surface for a prolonged period before they are wiped away. According to the National Institutes of Health (NIH) a contact time of 20 to 30 minutes may be required to inactivate microorganisms, especially on items that are difficult to clean because of narrow channels or other areas that can potentially harbor microorganisms. In a busy food processing environment, it can be a considerable challenge to comply with these time-intensive disinfection procedures.

The longer bacteria thrive on – and below – the surface of plant flooring, the greater the risk of transmission. Shoes, vehicles, dirty equipment, hoses that lay or are dragged across floors, aeration and atomization, and even employees’ clothing have all been shown to harbor and transmit problematic bacteria. This ultimately increases the risk of food contamination.

During a six-month study conducted by Queen’s University of Belfast, United Kingdom, researchers isolated 289 Listeria strains from a poultry-processing environment and from poultry products to pinpoint sources of contamination within the plant. The analysis revealed that Listeria strains that had originated with the incoming birds had been broadly transmitted to food contact surfaces, floors and drains.

A Silver-Based Flooring Solution

The USDA has passed strict regulations that require the RTE food processing industry to develop and report procedures to prevent product adulteration by Listeria. Unfortunately, in many cases, conventional cleaning products fail to meet the needs of plant operators and sanitation professionals. Therefore, new solutions must be developed to control populations of Listeria and other bacteria on plant flooring.

One potential solution comes in the form of ionic silver. New self-cleaning coatings that contain a silver-based antimicrobial are currently being developed to help protect flooring from damage and provide a defense against problematic bacterial. These resin-rich, epoxy-based coatings are impervious to chemicals, moisture and corrosion, and shield the floor from everyday wear and tear. Since they are thermally compatible with concrete, they are not prone to the failure mechanisms of traditional epoxies, such as thermal shock and delamination. These coatings must undergo review by the Environmental Protection Agency (EPA) as part of the development process prior to introduction into the market, but surfaces treated with ionic silver have shown efficacy against a wide range of bacteria in laboratory tests, including the bacteria of greatest concern to RTE processors today.

These coatings can be used to protect floors and other food processing plant surfaces, such as walls, ceilings and overhead piping. They seal off these surfaces and protect them from damage, and the resiliency of the epoxies minimizes the formation of cracks and crevices that can harbor problematic bacteria. The added antimicrobial also prevents biofilm formation in and around surface irregularities and reduces bacterial build-up between cleanings, making it easier to remove surface microorganisms.