Question

Polyphenol oxidase is responsible for:

• A. Maillard browning
• B. Enzymatic browning
• C. Caramelization
• D. Lipid oxidation

Hint:

Cut apple turns brown due to PPO + oxygen. Prevent it using acid (lemon juice) or refrigeration.

Answer 1

The Correct Option is B

Concept: Polyphenol oxidase (PPO) is an enzyme widely present in fruits and vegetables. It catalyzes the oxidation of phenolic compounds into quinones, which then polymerize to form brown-colored pigments. This process is known as enzymatic browning.

Step 1: Understanding enzymatic browning.
When fruits or vegetables are cut or damaged:
• Cellular compartments are disrupted
• Enzymes come in contact with oxygen
• Polyphenols are oxidized This leads to browning of the exposed surfaces.

Step 2: Role of polyphenol oxidase.
Polyphenol oxidase catalyzes:
• Conversion of phenols to o-quinones
• Subsequent polymerization into brown pigments (melanins)

Step 3: Evaluating options.

• Option (A): Maillard browning — Non-enzymatic reaction between amino acids and reducing sugars. Not related to PPO.
• Option (B): Enzymatic browning — Directly catalyzed by PPO. Correct.
• Option (C): Caramelization — Thermal decomposition of sugars. No enzyme involved.
• Option (D): Lipid oxidation — Involves fats, not PPO. Final Conclusion:
Polyphenol oxidase is responsible for enzymatic browning in fruits and vegetables. Hence, the correct answer is option (2).