Turns out it's not jagged razors in apples that kids have to watch out for this Halloween. It's caramel apples—and the dangerous part is the stick.
Not because the stick will be used as some sort of improvised shiv, so get your mind out of that particular gutter. Instead, a study by scientists at the University of Wisconsin-Madison, just published in mBio, says that the sticks in caramel apples help to promote the growth of listeria—the nasty bacteria that causes a particularly virulent type of food poisoning. Late last year, listeriosis killed seven people, caused one miscarriage, and hospitalized dozens more.
The scientists had an inkling that there was something about the process of making caramel apples that fostered the spread of listeria. So, they inoculated some apples with listerial monocytogenes and then dipped them in caramel coating. Some apples had sticks inserted into them before the dipping and others did not. Some were refrigerated and others left at room temperature.
Guess what happened? There was no growth of listeria monocytogenes on the refrigerated caramel apples without sticks, and only slow growth on the refrigerated caramel apples with sticks. However, the caramel apples with sticks that were not refrigerated? Not good: "Significant pathogen growth was observed within 3 days at room temperature on caramel apples with sticks inserted," the study says.
Given that many caramel apples eaten around Halloween have sticks and are kept with little-to-no refrigeration for significant periods of time, scientists are warning that caution is required during the approaching holiday season.
The piercing of the apple with the stick may be what triggers the problem. Juice from the apple is released, which drips into the caramel. The space under the apple skin provides a nice place for listeria to grow. And, evidently, the bacteria prefer a room-temperature environment.
In the words of the authors, "Insertion of a stick into the apple accelerates the transfer of juice from the interior of the apple to its surface, creating a microenvironment at the apple-caramel interface where Listeria monocytogenes can rapidly grow to levels sufficient to cause disease when stored at room temperature."
The 2014 listeria outbreak was linked to apples produced and distributed by Bidart Brothers, which recalled all of their Granny Smith and Gala apples after testing showed the presence of listeria at their apple-packing plant. Three companies—Happy Apple, California Snack Foods, and Merb's Candies—ended up recalling their caramel apples because the treats were made with Bidart fruit.
Listeriosis causes all sorts of awful symptoms—before it kills you, which it does some of the time. We're talking diarrhea, fever, muscle aches… you know, the whole gamut. It can also cause meningitis, but is treatable with antibiotics if caught early.
The weird thing about listeria poisoning, however, is that although most people show symptoms within two to three weeks of eating bacteria-laded food, others don't get sick until several months later.
So kids, this Halloween, take our advice. Stay away from "healthy" fruit-based treats and, instead, stick with the ubiquitous packaged-and-processed, industrially produced, corn-syrup-laden delights of the season.
That, or eat caramel apples that don't have sticks.