Question

when we cut an apple why it turns black what is this process called

Answer 1

When an apple is cut (or bruised), oxygen is introduced into the injured plant tissue. When oxygen is present in cells, polyphenol oxidase (PPO) enzymes in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colorless precursors to brown-colored secondary products.

Answer 2

The apple reacts with oxygen and it turns black in colour.