Why are apples that have been boiled after they are peeled, do not change colour to brown?

See the explanation below.

Explanation:

A freshly cut apple eventually turns brown after being exposed to air because its cells contain an enzyme called polyphenol oxidase. When this comes in contact with oxygen present in the environment, it turns the phenolic compounds present in the apple tissues into brown-colored products, imparting a brownish tinge to the freshly cut apple.

In fact, coating an apple with lemon juice not only affects its oxygen supply, but also impacts the function of enzymes. Lemon juice brings down the pH of the environment of the apple, thereby attacking the efficiency of PPO (Polyphenol Oxidase).

A surefire way to stop apples from turning brown is to apply heat to them, either by cooking or briefly blanching them in water.