Why does cut apple turn brown?

-Karthik Gurumurthy

It doesn’t have to be just apple. Most of the cut/bruised fruits turn brown. Why is that?

Chemical compounds in the fruit are oxidized when the skin of the fruit – and hence the walls and membrances of the cells within the fruit- is ruptured, allowing oxygen in. These compounds react with oxygen, usually incorporating into their molecular structure. Many of the resulting oxidized compounds have a brown color. Citric acid is very easily oxidized and can be used to steal oxygen to keep the fruit from turning brown. This is the reason why sliced apples will remain white for a longer period if they are dipped in lemon juice.