Caramel apples, a popular treat for Halloween and fall parties, can make someone very sick if they have not been refrigerated and contain dipping sticks, researchers warn in a new study.
Listeria monocytogenes bacteria and dipping sticks are the culprits. Because caramel has a low amount of water and apples are acidic, neither are normal breeding grounds for listeria, explained study author Kathleen Glass, associate director of the Food Research Institute at the University of Wisconsin-Madison.
However, piercing an apple with a dipping stick causes a bit of apple juice to leak out and become trapped under a layer of caramel, creating an environment that aids the growth of listeria already present on the apple's surface, Glass explained.
When listeria is already present, it can survive refrigeration and even freezing. But both methods for storage can help prevent listeria from developing when it is not present.
Researchers studied the growth of the listeria bacteria on caramel apples that were stored at room temperature versus caramel apples that were refrigerated. They found that the amount of listeria on unrefrigerated apples with sticks increased 1,000-fold, while listeria growth on unrefrigerated apples without sticks was delayed, the investigators found.
Refrigerated apples with sticks had no listeria growth for a week, but then had some growth over the next three weeks. Refrigerated apples without sticks had no listeria growth over four weeks, the findings showed.
To be safe, you should buy refrigerated caramel apples or eat them fresh, Glass advised.
Packaged caramel apples were responsible for a serious Listeriosis outbreak in 2014 in which 35 people in 12 states were infected and seven died, the researchers said.
If caramel apples are a favorite in your family, make sure they are either eaten right away after being made or refrigerated. If you purchase them, make sure they come from a refrigerated compartment and have not been sitting out in the store at room temperature.
Symptoms such as fever, muscle aches, nausea and diarrhea may begin a few days after you've eaten contaminated food, but it may take as long as two months before the first signs and symptoms of infection begin.
If the listeria infection spreads to your nervous system, signs and symptoms may include headache, stiff neck, confusion or changes in alertness, loss of balance or convulsions.
Seek emergency care if you experience any of these symptoms and you believe you may have eaten contaminated food.
Healthy people can usually tolerate a listeria infection, but the disease can be fatal to unborn babies and newborns. People who have weakened immune systems also are at higher risk of life-threatening complications. Prompt antibiotic treatment can help curb the effects of listeria infection.
Source: Robert Preidt, http://www.webmd.com/food-recipes/food-poisoning/20151014/caramel-apples-can-harbor-listeria-study-finds