Why do bananas turn brown?

Bananas turn brown because their cells change as they ripen. When the cell walls weaken, an enzyme can meet natural fruit chemicals and start a reaction that makes brown pigment. At the same time, starch turns into sugar, so the banana grows softer and sweeter.

That brown color is made from melanin, a pigment your child may also hear about in skin and hair. The speckles on a ripe banana are not dirt or bruises by themselves; they are signs of busy chemistry inside the fruit.