rusting of apple

The rusting of apple? Most of us love apples,but have you thoughats why does a cut apple turns brown in colour?it is just because when exposed to air,due to the oxidation process which goes on inside the apple as it comes in contract with the air containing oxygen.this brown colour is actually the rust.apples are a rich source of iorn,which when exposed to air reacts with oxygen forming iron oxides.apples skin protects it form this process.