Why does pineapple juice prevent apples from turning brown?

The browning of fruits and vegetables is caused by a chemical reaction called enzymatic browning. This reaction occurs when the cells of fruits and vegetables are damaged, releasing enzymes that react with oxygen to produce brown pigments.

Pineapple juice contains an enzyme called bromelain, which can break down proteins. However, bromelain does not break down the enzymes responsible for enzymatic browning. Therefore, pineapple juice does not prevent fruits and vegetables from browning.