Why do apples and potatoes turn dark when cut?

You probably learned from school that all cells contain numerous enzymes. These enzymes are essential for the cells to function properly. Apples and potatoes darken due to the enzyme polyphenol oxidase, also known as tyrosinase, found in their cells. This enzyme oxidizes the phenolic compounds in the fruit, causing the darkening of the tissue.

When you cut vegetables or fruits, you damage some of their cells. The enzyme comes into contact with oxygen in the air, causing the fruit to brown. Similarly, bruises on apples darken when they fall from the tree and hit the ground.

The easiest way to prevent produce from browning is to place apples or potatoes in water, preventing them from coming into contact with oxygen. You can also heat them to denature the enzyme.

The human body also contains tyrosinase. It helps create melanin, which causes skin tanning. A lack of tyrosinase in the human body results in albinism. Therefore, the human body needs the enzyme tyrosinase.




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