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Researchers Linked Listeria Outbreak to Caramel Apples

Olivia Finger1 year ago

After seven people died and 28 others were infected with listeriosis, FOX News reports that researchers are now aware of the source.

Illnesses Linked to Contaminated Caramel Apples

Listeria monocytogenes, otherwise known as Listeria, is known to cause infections in humans through the ingestion of contaminated food. The bacteria were found in caramel apples, but until today it had been a mystery as to how the apples acquired it.

Since apples are acidic, they provide an inhospitable breeding ground for these disease-causing bacteria. Thus confusing researchers about its origins.

Researchers then came to the conclusion that the problem “had to be from damaging the apple”, Kathleen Glass, the associate director of the University of Wisconsin-Madison's Food Research Institute and lead author on the study said.

The source ended up being the stick inserted into each apple, according to the new finding. The sticks were inserted to turn the apple into a hand held caramel treat.

How Apples Came to be Contaminated

It is suspected that when the stick is poked into the apple, juices come out and become trapped between the apple and the caramel coating, Glass stated. The caramel, which is nonacidic, creates a superior breeding ground for bacteria.

A test was done to determine if this was the exact cause of Listeria growth. Researchers purchased 12 dozen apples and contaminated them with a mixture of four strains of Listeria, then proceeded to turn them into caramel apples.

Half of the apples had sticks, the others without. All apples were dipped into caramel.

“Anything on the surface [of the apples] will die from the hot caramel,” Glass said. The real issue comes from the spots on the apples that don’t touch the caramel; for instance, the end of the apple and the stem.

There was significant amount of Listeria growth on the apples with sticks in them, after only three days. The apples without sticks saw Listeria growth after seven days. Apples that were refrigerated saw bacteria growth after three weeks, the study concluded.

Glass said that it is unnecessary for people to stop eating caramel apples, but retailers should be aware of the shelf life of a caramel apple.

Producers of caramel apples are now trying new ways to sanitize the apples so that no part may become contaminated. 


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