Question

The enzyme responsible for enzymatic browning in cut fruits is .................

• A. Catalase
• B. Peroxidase
• C. Polyphenol oxidase (PPO)
• D. Lipase

Hint:

To stop PPO, one can: 1. Lower pH (use lemon juice). 2. Remove oxygen (submerge in water). 3. Inactivate enzyme with heat (blanching). 4. Use reducing agents (Ascorbic acid).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
Enzymatic browning is a common discoloration in fruits like apples, bananas, and potatoes when they are cut or bruised. The question asks for the specific enzyme that catalyzes this reaction.

Step 2: Detailed Explanation:

• Polyphenol Oxidase (PPO): This enzyme, also known as tyrosinase or catecholase, is found in the plastids of plant cells. When the fruit is cut, the cell structure is disrupted, and PPO comes into contact with its substrates (phenolic compounds) and atmospheric oxygen.

• The Reaction: PPO catalyzes two reactions:
- Hydroxylation: Monophenols $\rightarrow$ Diphenols.
- Oxidation: Diphenols $\rightarrow$ Quinones.
The quinones are highly reactive and spontaneously polymerize to form brown, black, or red pigments called melanins.

• Catalase (A) and Peroxidase (B): These are involved in oxidative stress management and the breakdown of peroxides. While Peroxidase can contribute to browning, PPO is the primary enzyme responsible for the rapid darkening of fresh-cut produce.

• Lipase (D): This enzyme breaks down lipids into fatty acids and is not involved in pigment formation.

Step 3: Final Answer:
Polyphenol oxidase (PPO) is the primary enzyme responsible for enzymatic browning.