ANS:B - hydrogenation

The correct answer is: hydrogenation

Explanation:

Rancidity is the process by which fats and oils degrade and develop unpleasant smells and flavors. This typically occurs due to the oxidation of unsaturated fatty acids in the oil, leading to the formation of peroxides and other degradation products.

Methods to Reduce Rancidity:

1. Decoloration: This process removes pigments and impurities but does not significantly affect the oxidation of oils, hence it doesn't effectively reduce rancidity.
2. Hydrogenation: This process involves adding hydrogen to the unsaturated bonds in fatty acids, converting them to saturated fats. Saturated fats are more stable and less prone to oxidation, which reduces rancidity. Hydrogenation is commonly used in the food industry to increase the shelf life of oils and fats.
3. Oxidation: This is actually the process that causes rancidity, so it would increase rather than reduce rancidity.
4. Purification: Purification can remove impurities and contaminants, which might slightly help in reducing rancidity, but it doesn't address the primary cause, which is the oxidation of unsaturated fats.

Hydrogenation is the most effective method for reducing rancidity because it stabilizes the oil by saturating the double bonds in the fatty acids, making them less susceptible to oxidative degradation.