Question

Which one of the following oils has higher iodine value?

• A. Coconut oil
• B. Rapeseed oil
• C. Soyabean oil
• D. Fish oil

Hint:

Fats and oils with high iodine values (like fish oil and linseed oil) are highly susceptible to oxidative rancidity because the double bonds are highly reactive with atmospheric oxygen, producing off-flavors and free radicals.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The iodine value (or iodine absorption number) is a chemical index used to measure the degree of unsaturation (presence of double bonds) in fats and oils.
A higher iodine value indicates a higher number of double bonds present in the fatty acid chains.

Step 2: Detailed Explanation:
Let us compare the typical iodine values of the listed oils:
- Coconut oil: Predominantly saturated fatty acids (\(\approx 90\%\)), resulting in an extremely low iodine value of \(6\text{--}10\).
- Rapeseed oil: Monounsaturated-rich, with an iodine value of \(94\text{--}120\).
- Soybean oil: Polyunsaturated-rich, with an iodine value of \(120\text{--}140\).
- Fish oil: Contains very high concentrations of long-chain Highly Unsaturated Fatty Acids (HUFAs) such as EPA (5 double bonds) and DHA (6 double bonds), yielding an exceptionally high iodine value of \(120\text{--}200\) (often exceeding \(150\)).

Step 3: Final Answer:
Therefore, fish oil has the highest iodine value among the options, corresponding to option (D).