Apples contain some phenolic compounds containing iron. When you peel an apple or dice it, the surface of the cut fruit comes into contact with air. Air has oxygen in it. Oxygen oxidizes these phenolic compounds and turns them brown. The enzyme responsible for this is polyphenol oxidase. The brown phenols form a layer on the exposed surface and that is how apples turn brown.
It is actually possible to prevent browning. You can try to cut off its contact with oxygen by covering the fruit, putting it in a sealed air proof bag or immersing it in water. Putting a little lemon juice on it can also help.
It is actually possible to prevent browning. You can try to cut off its contact with oxygen by covering the fruit, putting it in a sealed air proof bag or immersing it in water. Putting a little lemon juice on it can also help.
