Caramel Apples Are Potentially Ripe For Listeria Growth, Scary Research Shows

The sticks inserted into caramel apples to make them easier to enjoy at fall harvest festivals, carnivals, and Halloween haunted houses, also makes them more susceptible to listeria exposure, a frightening study has found.

Published in mBio, a journal from the American Society for Microbiology, listeria growth within a "caramel-coated apple microenvironment" was well-documented, especially at room temperature.

Researchers noted that, "neither caramel nor apples are a food where the pathogenic bacterium Listeria monocytogenes should grow, as caramel does not contain enough free water and apples are too acidic." Despite this, a listeria outbreak linked to caramel-covered apples killed five people and sickened at least 28 people across 10 states last year.

The team found, however, that when sticks were inserted into listeria-treated apples, the juice released from the apples provided "a more hospitable environment than either component alone." In trials, researchers found that, without sticks inserted, refrigerated caramel apples treated with listeria did not see any growth of the bacteria. In both refrigerated and unrefrigerated caramel apples with sticks, however, bacteria growth was noted — especially at room temperature.