According to a new report published in the journal mBio, wooden sticks poked into caramel-coated apples lets out enough juice to provide a nourishing location for the growth of the Listeria bacteria. In fact, the research team from the University of Wisconsin-Madison notes that their discovery could very well explain last winter’s Listeria outbreak which was linked to caramel apples and caused approximately three dozen people to become ill.
Kathleen Glass, of the University of Wisconsin-Madison, and her colleagues report: “The outbreak took producers, public health officials, and food safety experts by surprise: caramel-coated apples are not a food on which Listeria monocytogenes should grow.”
According to the investigative team, apples themselves are too acidic to allow the bacteria to survive. Their initial question though was if putting a wooden stick into apples would let enough juice escape in order to create a moist location for Listeria to thrive.
The researchers put Listeria bacteria on several on Granny Smith apples which they report had been the kind implicated in the Listeria outbreak. They stuck sticks into half of their apples and left the other half without sticks. Finally, they dipped all the apples into hot caramel.
The research team wrote: “No growth of L. monocytogenes occurred on refrigerated caramel apples without sticks, whereas slow growth was observed on refrigerated caramel apples with sticks. In contrast, significant pathogen growth was observed within three days at room temperature on caramel apples with sticks inserted.”
Listeria may only cause a terrible stomachache for some. However, it can actually kill infants, senior citizens and anyone with a weak immune system. Furthermore, it can cause stillbirth and miscarriage.
This Halloween the research team suggests that while leaving the sticks out would be “an obvious solution”, the caramel apples would then be nigh impossible to eat. They concluded that apples used to make the Halloween treats should be additionally disinfected and then refrigerated.
Have Listeria With Your Caramel Apples This Halloween?