Refrigeration and Listeria monocytogenes

Cooling is one of the most important hygiene measures. Without refrigeration, food will spoil in no time with all the possible consequences. Fresh fruit and vegetables generally remain good for ten to fourteen days at 0 – 2 °C (32 – 36 °F). In the refrigerator, where a temperature of 5 – 7 °C (42 – 45 °F) prevails with a properly adjusted refrigerator, perishable food will last for an average of four to six days. The same food stored at room temperature would be spoiled after just a few days.

Refrigerator temperature

However, some bacteria can still grow at refrigerator temperatures and be present in the product in such large numbers at the end of the shelf life that we get sick from it. One of these bacteria is Listeria monocytogenes which can still grow at temperatures of 3 °C (37 °F).  The first report of foodborne infections caused by this bacterium dates back to 1983 in Canada and was caused by eating contaminated coleslaw. This bacterium causes a foodborne infection called Listeriosis. The bacterium enters the body through the gastrointestinal tract and settles in the organs (such as the spleen and liver) to multiply further. For high-risk groups (children, the elderly and the sick) with insufficient immunity, this can lead to life-threatening situations. In pregnant women, an infection with Listeria monocytogenes can lead to miscarriage. It is estimated that worldwide 23.000 people get Listeriosis every year, of which about 5.000 people die.

Listeria in food

Foods associated with Listeriosis include raw milk, soft cheeses, raw milk cheeses, fresh sliced vegetables, fresh and smoked fish, poultry, fermented sausages, pâtés, and ice cream. Listeria is regularly found in raw milk and soft cheeses in particular. Therefore, pregnant women are not recommended to consume these products. To prevent growth, fresh, raw food is best stored at temperatures below 3 °C (37 °F).  When heated, the risk of Listeria is reduced to zero, because at a temperature of 75 °C (167 ³F) the bacteria are killed.


Published: 07-06-2024