Rancidity: Rancidity is the process of oxidation of fats and oils present in food items, leading to a change in their smell and taste (they become stale or unpleasant). This occurs when food items containing fats and oils are exposed to air (oxygen) for a long period.

Prevention of Rancidity: Rancidity can be prevented by several methods:
1. Adding antioxidants: Antioxidants are substances that prevent oxidation. They are added to fat and oil-containing foods. E.g., BHA (Butylated Hydroxyanisole) and BHT (Butylated Hydroxytoluene).
2. Packing in nitrogen gas: Food items like potato chips are flushed with nitrogen gas in their packets. Nitrogen is an inert gas and prevents the oxidation of fats and oils.
3. Refrigeration: Keeping food in a refrigerator slows down the oxidation process because chemical reactions are slower at lower temperatures.
4. Storing food in airtight containers: This reduces the exposure of food to oxygen.
5. Storing food away from light: Light can accelerate the oxidation process, so storing food in dark places can help prevent rancidity.