When fats and oils are oxidized in the presence of air, they become rancid and their smell and taste change. This phenomenon is called rancidity.

Rancidity can be prevented by:

i. Using antioxidants- substances which prevent oxidation are called antioxidants. They are added to foods containing fats and oil.

For example, Nitrogen gas is filled in the packets of chips to prevent them from oxidation.

ii. Keeping food in air tight containers to slow down the process of oxidation.