Why does an apple turn brown on being cut?
● Apples, and other fruits like pears, bananas, peaches, potatoes, contain an
The enzyme (called polyphenol oxidase or tyrosinase) reacts with oxygen, and
iron-containing phenols that are also found in the apple.
● The oxidation reaction forms a sort of rust on the surface of the fruit.
You see the browning when the fruit is cut or bruised because these actions
damage the cells in the fruit, allowing oxygen in the air to react with the enzyme
and other chemicals.
● These enzymes do all of the work necessary for the cell to live its life. Once you
Cut the fruit, you open up some of the cells. The enzyme then has access to
oxygen in the air and it does its thing, turning the fruit brown.
● This is the same thing that causes brown spots in apples when you drop them. It
is believed that this reaction, called enzymatic browning, is a form of plant
defense against pests and pathogens.
● The easiest way to prevent browning is to put the sliced apples in water so that
the enzyme does not have access to oxygen. You can also heat the apples to
denature the enzyme.