Question

Enzymatic browning in tea is due to the oxidation of phenols by -

• A. Phenolase
• B. Catalase
• C. Orthoquinones
• D. Tyrosinase

Hint:

Green tea processing bypasses enzymatic browning because the freshly harvested leaves are immediately steamed or pan-fired (heated) to irreversibly denature and deactivate the phenolase enzyme, preserving the green color and catechins.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Enzymatic browning is a chemical process involving polyphenol oxidases that occurs during the processing of black and oolong teas, contributing to their characteristic color and flavor.

Step 2: Detailed Explanation:
During the rolling and "fermentation" (oxidation) stages of black tea manufacturing, the green tea leaves are crushed to disrupt the plant cells.
This releases the enzyme polyphenol oxidase (commonly called phenolase) from the plastids, allowing it to contact its substrates, the catechins (polyphenols) located in the vacuoles.
Phenolase catalyzes the oxidation of these catechins into highly reactive ortho-quinones.
These quinones then spontaneously undergo non-enzymatic condensation to form the complex pigments: theaflavins (orange-yellow) and thearubigins (reddish-brown), which define the color and body of black tea.

Step 3: Final Answer:
The enzyme responsible is Phenolase, which corresponds to option (A).