This is not only a phenomenon that you can notice on apples, also pears, eggplant and banana turn brown when they are cut or bruised. This always might seem a little unappetizing but the fruit most of the time still almost tastes the same and the spots are harmless. Nevertheless, the question about this unfortunate characteristic pops up, and I am going to tell you the answer to that,- just keep reading!
‘Enzyme browning’ is what this biochemical reaction is called. As soon as the inside of the apple is exposed to oxygen, when the apple is cut or insured, inside the plant tissue an enzyme is triggered. Oxidized polyphenols or short PPO happens in the apple’s flesh. This results in new chemicals which then react with amino acids to produce brown-colored melanins. You might also have noticed that some apples brown faster than others,- this is because of the different amounts of initial enzyme and the polyphenols they contain. Thus they turn brown at different rates.
As already mentioned enzymatic browning is not unique to apples. Also, other fruits turn brown fairly quickly when cut. Moreover, also the dark color of coffee, black tea and cocoa originates from this chemical reaction. In contrast to apples the dark color here is desirable, but if you don’t want your apple slices to get brown there are also some reasonable solution approaches. First off, there is lemon or pineapple juice. Coat the slices with it and the process gets slowed down because of the acids and antioxidants these juices contain. These retard the process of oxidation and thus the exposure of apples to oxygen is not that bad. Storing the already cut slices in the refrigerator slows down the browning as well. Coating everything in sugar, honey or caramel also helps since the syrup blocks their exposure to oxygen. Heating can also be used to deactivate PPO enzymes; apples can be blanched in boiling water for four to five minutes to nearly eliminate PPO activity. But obviously, then the apple slices are not the ones you had before and the texture will be completely different. Moreover, Scientists are working to genetically engineer apples that do not produce the PPO enzyme. Arctic apples are that kind of apples. When these apples get cut or injured they remain their original color. Scientists practiced gene silencing and reduced thereby the expression of polyphenol oxidase (PPO). In the US (2015) and Canada(2017) they are generally approved for commercial sale. The Food Agencies in these counties approved and concluded that Arctic apples are as safe and nutritious as conventional apples. So maybe also in Europe fruits that look unappetizing and brown soon will belong to the past. Imagine you cut yourself apple slices in the morning and when you open your lunchbox later in school everything just looks like you left it. For me, this is a little bit of a weird image, but I think it could be a nice thing to get used to.
However, don’t forget that brown apples might not look very appetizing but that they can be eaten without a second thought. These patches are completely natural and additionally, they tend to have a little bit of a nutty flavor. So don’t be afraid to eat them, even if they are brown. And if you don’t like it, keep an eye up for Attic apples or use methods to prevent them from getting brown. In the end, there is no better way to finish this article than to underline how healthy apples are and to say what everyone knows: ”An apple a day keeps the doctor away!”- even if they have brown patches:)
Sources:
https://www.britannica.com/story/why-do-sliced-apples-turn-brown
https://www.scientificamerican.com/article/experts-why-cut-apples-turn-brown/
https://en.wikipedia.org/wiki/Arctic_Apples