Question

Given below are two statements:
Statement I: The rapid darkening of the cut surface of the apple, brinjal, and potato indicate they are good sources of Iron
Statement II: When the cut surface of the fruit is exposed to air, phenoloxidase enzyme released at the surface act on polyphenols present, oxidize them to form brown pigment
In light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Enzymatic Browning: Polyphenol Oxidase (PPO) $+ \text{Oxygen} + \text{Polyphenols} \rightarrow \text{Brown Melanins}$. Inhibited by Ascorbic acid (Vitamin C), blanching, or low pH.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Enzymatic browning in sliced fruits and vegetables is catalyzed by polyphenol oxidases, not elemental iron oxidation.
Key Formula or Approach:
\[ \text{Polyphenols} + \text{O}_2 \xrightarrow{\text{Polyphenol Oxidase (PPO)}} \text{o-Quinones} \longrightarrow \text{Melanin Pigments (Brown)} \]

Step 2: Detailed Explanation:
1. Statement I: The popular lay misconception that sliced apples or brinjals turn dark because of 'high iron rusting' is chemically incorrect. Enzymatic browning is independent of mineral iron content. Hence, Statement I is incorrect.
2. Statement II: When cellular plant tissues are cut, latent Polyphenol Oxidase (PPO Phenoloxidase Tyrosinase) enzymes come into contact with vacuolar phenolic substrates and atmospheric oxygen, catalyzing the oxidation of monophenols/o-diphenols into brown melanin polymers. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Statement I is incorrect but Statement II is true, matching option (D).