Caramel apples can be magnet for listeria

Lead study co-author Doctor Kathleen Glass, associate director of the University of Wisconsin-Madison’s Food Research Institute in the USA, said neither caramel, because of its low amount of water, nor apples, due to their acidity, are normal breeding grounds for listeria. For four weeks, the apples were either stored at 77° F (around room temperature) or in a fridge at 44.6° F. Those without sticks had no listerial growth over the four weeks they were refrigerated.

Though rare, consuming the Listeria bacteria through infected food is a nightmarish experience; a victim may suffer from a fever, a headache and vomiting – sometimes surfacing weeks after the initial contact. It is believed that when inserting the stick into the apple, inner juice leaks to the surface and creates an ideal microscopic environment between the apple and the caramel where bacteria can grow.

According to a new study, caramel apples, when stored improperly, can be hotbeds for gut-busting bacteria like Listeria monocytogenes, the bacterium responsible for hospitalizing 35 sugar-fiends (31 of whom specifically admitted eating caramel apples) back in 2014. Testing had revealed the presence of Listeria at the company’s apple plant. Caramel apples without sticks had no Listeria growth during four weeks of storage. But it might be worth thinking twice about the origin of a store-bought caramel apple. The study focused on apples with the wooden dipping sticks, which were left out for a few days.The key to the Listeria growth was the sticks inserted into the apples. Caramel apples stored at room temperature can more quickly become contaminated with listeria. By contrast, it took about two weeks for Listeria to grow on the refrigerated apples with sticks.

The hot caramel killed a lot of the surface bacteria, “but those that still survived were the ones that were able to grow”, Glass said.

The researchers said on obvious solution would be to leave the stick out of caramel apples, but noted that would make it nearly impossible to eat them. It’s unique in that it can grow and thrive in cold temperatures, like a refrigerator. The findings were published this week in mBio, an online open-access journal of the American Society of Microbiology.

What does this mean for consumers this fall season?

Perhaps apples used to make the treats should be given extra disinfection, they suggested. Glass recommends eating caramel apples fresh or ones that are refrigerated.