​​Why do Apple’s bruise when dropped?

A bruise is an indicator of cellular damage. When you ding an Apple or a Banana, it can compromise the ability of the skin or the peel to keep Oxygen away from the fruit, and Oxygen breaks down the cellular walls and membranes. As they feed on the fruit’s exposed innards, the cells multiply rapidly.
In general, bruised apples and pears are fine to eat. There are a few things you should check to make sure your fruit isn’t rotten or moldy. If there is discoloring on the skin of the fruit, peel the skin off this area.