“Listeria is a group of bacteria that is found in cold, wet environments,” said Fadi Aramouni, extension specialist and professor of food science. “What’s unusual about this type of bacterium is they actually grow and multiply under refrigerated conditions.”
Listeria is typically found in ready-to-eat deli meats and hot dogs, refrigerated meat spreads, unpasteurized milk and dairy products, soft cheese made with unpasteurized milk, refrigerated smoked seafood, and raw sprouts. According to the Food and Drug Administration, 16 different food products potentially containing listeria have been recalled since March, including products like hummus, frozen spinach, smoothie kits and most notably, ice cream.
“A listeria contamination in ice cream hasn’t happened for a very long time because the pasteurization process kills the pathogen,” Aramouni said. “However, listeria may survive in the environment if there are not good sanitation procedures in place. Because it survives in cold, wet environments, it can be found in drains or other areas of condensation within a plant, such as the ceiling or light fixtures.”
He says the listeria in ice cream also could be coming from the added ingredients.
“One of the things people may not know about ice cream is that it is not pasteurized after the inclusions are put in,” he said. “After they pasteurize the milk and make the ice cream, they add things like cookie dough or pecans. The ice cream is then placed in the freezer and does not go through any other type of pasteurization, so if the additional products are contaminated, listeria may survive that process.”
Unfortunately, there is no way for consumers to tell if their product is contaminated with listeria. But Aramouni says not to panic. Instead, pay close attention to recalls and return the product or throw out the product if it has been recalled, because consuming the product can be dangerous.
“This bacterium can be deadly, especially for older adults, pregnant women, young children and people with weakened immune systems” he said. “About 75 percent of these individuals who get listeriosis end up in the hospital and about 25 percent of them die, so it is quite virulent for this group. Don’t take chances. Anytime there’s a recall, respect that recall and do not consume the food.”