Why do peeled apples turn brown over time?

If we peel an apple and leave it, it will turn brown.
This is because the polyphenol contained in apples combines with oxygen in the air to form a brown pigment.
Apples contain polyphenols and substances called enzymes that oxidize them.
Initially, each is in a different location inside the cell, but when cut, the cells break and come together.
Furthermore, when it comes into contact with air, the enzyme binds polyphenols to oxygen. And a brown pigment is formed.
This is how apples turn brown.
It's okay to eat brown apples. However, it doesn't look good.
To prevent the apples from turning brown, you can peel them off and immediately soak them in dilute salt water.
Salt interferes with the action of enzymes.
We can also sprinkle lemon juice on it.
Vitamin C contained in lemon easily binds to oxygen, which reduces the surrounding oxygen and prevents the oxidation of polyphenols.
In addition, it deprives the browned apple of oxygen and restores its original color.
In addition to apples, there are many other things that turn brown when peeled, such as bananas, avocados, potatoes, burdock roots, and lotus roots.
These are the same as apples, and they turn brown due to the oxidation of polyphenols.