Question

Bitterness in carrots during cold storage is often due to the synthesis of ______.

• A. Isocoumarin
• B. Solanine
• C. Lycopene
• D. Anthocyanin

Hint:

Never store carrots in the same cold room as ethylene-producing fruits like apples. Ethylene triggers carrots to synthesize isocoumarin, making them extremely bitter.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the specific chemical compound synthesized in carrots during cold storage that is responsible for causing a bitter off-flavor.

Step 2: Detailed Explanation:

• Post-Harvest Stress in Carrots: Carrots are susceptible to physiological stress during post-harvest handling and storage. Exposure to trace levels of ethylene gas ($C_2H_4$) in cold storage rooms (often co-released by other ripening fruits like apples or bananas) triggers stress-induced metabolic pathways.

• Synthesis of 6-Methoxymellein: This ethylene-induced stress stimulates the synthesis of phenolic compounds, specifically a phytoalexin called 6-methoxymellein, which belongs to the chemical class of isocoumarins.

• Sensation of Bitterness: This compound accumulates in the peel and core of the carrots and is highly bitter. Its presence makes the carrots unpalatable, representing a major quality defect.

• Why Other Options are Incorrect:

• Solanine: A toxic glycoalkaloid found in nightshade plants like potatoes, not carrots.

• Lycopene: A red carotenoid pigment found in tomatoes, not related to bitterness.

• Anthocyanin: A water-soluble red-purple vacuolar pigment found in berries and purple carrots, not associated with bitterness.

Step 3: Final Answer:
The accumulation of the bitter compound isocoumarin (specifically 6-methoxymellein) causes bitterness in carrots during cold storage, corresponding to option (A).