• Sara Thompson

How Do You Like Them Apples?

By Sara Thompson

Special to the Enterprise


2 halves of an apple with sliced face showing
Sliced Apples; by Marius Lordache, from Wikimedia Commons

Apples are rich in vitamins and antioxidants, making them a healthy snack for all ages. Depending on the variety and where they are grown, apples are generally ripe between July and November, making them plentiful right now. Apples can be eaten in a variety of ways, including baked, poached, grilled, or eaten as is. When you bite into an apple or slice it, you may notice the flesh begins to turn brown within a few minutes. This is called oxidation and is common in many fruits and vegetables. But why does this happen and how can we avoid it?


The browning in an apple is caused by a chain reaction in the flesh of the apple when you expose it to air. Inside the tissue cells of an apple is an enzyme called polyphenol oxidase. The enzyme reacts with the oxygen in the air and create a new chemical called o-quinones. The chain reaction continues with the o-quinones reacting with amino acids in the apple, producing melanin, which gives the cut apple its brown look. Different varieties of apples have different levels of the polyphenol oxidase enzyme, and therefore the browning reaction can vary from apple to apple.


Scientists are looking into ways to prevent the browning in apples by genetically altering the amount of polyphenol oxidase in apples to reduce or prevent the reaction. Until then, there are some simple ways to slow down the browning at home. The polyphenol oxidase enzyme works best at room temperature, so changing the temperature of the apple can slow down the reaction. You can carefully place the sliced apples in boiling water for up to five minutes to slow the reaction, or place the apple slices in ice water to achieve the same slowing. Cooking or soaking the apple slices can change the apple texture, however. Lemon juice lowers the pH of the apple causing the polyphenol oxidase to become less active. Coating apples slices in sugar or syrup can also slow the exposure of the apple tissue to oxygen, but you also increase the level of sugar and sweetness to the apples.


No matter how you slice it, apples will eventually brown due to the exposure to oxygen in the air. There are several ways to slow it down, but eating browning apples will not harm you unless they have been left out in the open long enough to begin decomposing. Try some of the different ways to stop the browning at home and discover what works best for you, and remember to enjoy your healthy snack after your experiments.


 

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