Researchers from the Food Research Institute of Wisconsin warn us: studies show caramel coated apples cause listeria.
The study was published in journal mBio, on October 13 and was conducted by the lead researcher, Dr Kathleen Glass, which says that the coated apples can cause listeria depending on how they are stored, but she admits that we need more research on this topic.
The paper affirms that 34 people have reported severe symptoms and were admitted to hospital, but seven of them died of listeria.
144 Granny Smith were bought for the study. They chose Granny Smith because of their high level of acidity, which makes bacteria harder to grow. After that, researchers inserted wooden sticks into half of the apples to see how the stick affects the apple pH and favorizes bacterial growth.
Apples were infected with several strains of listeria monocytogenes. Half of the apples were stored for three days at 25 degrees temperature, while the other half was stored at 7 degrees Celsius. It has been proven that the highest level of listeria was found in the apples with the wooden stick. Listeria grew after 7 days in the unrefrigerated apples without sticks.
After this study, researchers warn retailers about possible danger, suggesting them to keep coated apples in the refrigerator, making sure they respect all consumer security norms.
NHS ( National Health Service) states that only a proper food hygiene can prevent the risk of listeria contamination.
Previously, scientists considered that listeria cannot grow and develop in caramel apples because of the acid pH which is not suitable for the bacteria. This is true only if the apples don’t have the wooden stick. Once we insert the wooden stick, before caramelizing the apples, the whole biochemical environment changes. They found that apple juice which comes in contact with caramel and gets neutralised by it, leads to a very hospitable climate for Listeria monocytogenes.
Listeria is a serious and dangerous infection which is usually caused by eating contaminated food and can be deadly.
Symptoms include diarrhoea, vomiting, headache and fever and it can pass in three days if it is not very severe. Sometimes the infection can spread to various organs of the body and cause severe complications.
Special blood tests are most common for the listeria diagnostication.
It is mandatory to respect the consumer safety by respecting all processing and storage conditions, making sure that refrigerator temperature is kept at or below 4 degrees Celsius.
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