The nasty stickiness of Listeria monocytogenes

Listeria monocytogenes is a nasty critter. Companies that detect contamination sometimes resort to the most absurd measures to get rid of it - disinfecting with a toothbrush, for instance. Once Listeria finds its way into your facility, demolition and reconstruction might seem like the only viable solution to rid yourself of this sticky bacterium.

By the way, Listeria m. is also a troublesome fridge dweller at home, thriving happily at temperatures above 7°C. Meat, raw dairy products, chopped leafy greens, and cabbage are the primary sources of contamination. Keeping your weekly supply of fresh groceries in a fridge that’s running too warm? You’re asking for trouble. Listeriosis can lead to narrowed blood vessels, meningitis, miscarriage, and kidney problems.

What’s another way to ask for misery? Skimping on the grout for your factory floor tiles! This polymer material must have the exact same expansion coefficient as the tile itself. However, cheaper filler materials are often used instead of what the supplier recommends. If Listeria settles into those grout joints, heating the floor becomes the only option. But guess what? The tiles are not designed to handle that. At this point, demolition has essentially begun. Poorly designed shaft seals in mixing machines, especially vacuum mixers and kettles, are another persistent contamination source. Replacing these with hygienically designed equipment is the only solution.

Listeria thrives particularly on rough materials. Tiny cracks in stainless steel caused by metal fatigue, material stress, or sloppy welding are a contamination hotspot, as are weathered plastic surfaces. Plastic is naturally water-repellent, which means cleaning agents can’t penetrate deeply enough. On the bright side, hairline cracks are relatively easy to detect. Coat the surface with vitamin B2 or a luminescent powder. Shine UV-C light on the area, and the cracks will light up clearly.

In short, there are more affordable alternatives to tearing everything down. Make active use of approved disinfectants like active chlorine, peracetic acid, quaternary ammonium compounds (quats), 70% alcohol, or UV-C light (switch alcohol to isopropanol if you produce HALAL-certified products). Always choose high-quality materials and replace them when necessary. And, please, stick to hygienically designed equipment.

IJsbrand Velzeboer

Curative Food Technologist
Scienta Nova