Like salmonella and E. coli, listeria is a potentially dangerous foodborne pathogen that can be contained with vigilant cleanliness and killed with heat. Unlike these other bacterium, listeria can even grow in a refrigerated environment. Because of its resistance to cold, it may present a danger in refrigerated foods such as milk, cold cuts, potato salad and soft cheeses — particularly if those cheeses are unpasteurized. Be particularly thorough in your cleaning efforts if you are pregnant, feeding someone with a compromised immune system or a small child.
Store-bought sanitizers, especially sanitizers that contain quaternary ammonia or chlorine solutions, are effective in killing listeria. However, a bleach solution of 1 teaspoon bleach per 1 quart of water is a strong and inexpensive weapon against the pathogen, as long as you change it daily. A bleach solution loses strength rather quickly. Flood food prep surfaces with bleach solution or store-bought sanitizer. Wait 10 minutes before rinsing and then allow the surface to air-dry. Scrub cutting boards with hot soapy water. Regularly wash dish towels and aprons and dry them, using maximum heat.
Killing with Heat
Heat is effective at killing the listeria bacterium. Cook high-risk foods such as hot dogs, lunch meats and sausages to an internal temperature of 165 degrees Fahrenheit. Use a clean meat thermometer to determine whether they are hot enough. Choose pasteurized products if you are pregnant or your immune system is compromised as these types of people are especially vulnerable to listeria infection. Pasteurized foods have been heat-treated to kill foodborne pathogens such as listeria.
Uncrossing Cross Contamination
Listeria spreads from one surface to another, and it can also spread between foods in your refrigerator. Cover leftovers, defrosting meat and dairy products. Wash your hands for 20 seconds after handling foods such as soft cheese or deli meat, which may be contaminated. Clean all refrigerator spills immediately — especially from raw meat or poultry — and wipe down the inside of your refrigerator regularly. Whenever possible, use separate cutting boards for high-risk foods such as chicken, and ready-to-eat foods such as salad vegetables.
An Ounce of Prevention
You won’t have to kill listeria if you avoid getting it in the first place. Refrigerate cooked foods within two hours after cooking. Stay away from products such as raw milk and soft, fresh cheeses — Brie, queso blanco or the blue-veined varieties — that have not been pasteurized. Keep your refrigerator as cold as you can without freezing your food as low temperatures retard listeria growth. Wash fruits and vegetables thoroughly under running water, and scrub root vegetables, melons and cucumbers with a clean vegetable brush. Eat leftovers soon; the longer they sit, the more chance listeria will have to grow.
References and ResourcesFDA: Keep Listeria Out of Your Kitchen
About Listeria: Preventing Listeria Infection
CDC: Listeria: Prevention
USDA: Controlling Listeria Monocytogenes in Small and Very Small Meat and Poultry Plants