Question

The enzyme responsible for production of bad smelling aldehyde in vegetables is:

• A. Polyphenol Oxidase
• B. Amylase
• C. Protease
• D. Lipo-oxidase

Hint:

Blanching (short heat treatment) is done before freezing vegetables primarily to inactivate lipoxygenase and prevent these bad smells.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
Off-flavors or "bad smells" in unblanched or stored vegetables often come from the breakdown of lipids. The question asks for the enzyme responsible for this.
Detailed Explanation:

• Lipo-oxidase (Lipoxygenase):
This enzyme catalyzes the oxidation of polyunsaturated fatty acids (like linoleic acid) that contain a cis,cis-1,4-pentadiene system.

• Formation of Off-Flavors:
The reaction produces hydroperoxides, which are unstable and break down into various volatile compounds, including aldehydes (like hexanal) and ketones.
These compounds are responsible for the "hay-like," "painty," or generally rancid off-flavors and smells in vegetables like peas and green beans.

• Other enzymes:
Polyphenol Oxidase (PPO): Responsible for browning (not necessarily bad smells).
Amylase: Breaks down starch to sugar.
Protease: Breaks down proteins.

Step 2: Final Answer:
Lipo-oxidase (Lipoxygenase) is the enzyme responsible for producing volatile aldehydes that cause off-odors in vegetables.