Question

On treatment with alkali, chlorophyll changes to

• A. Pheophytin
• B. Chlorophyllin
• C. Xanthophyll
• D. Vitamin A

Hint:

Remember the two main reactions of chlorophyll during processing:

\textbf{Acid + Heat} \(\rightarrow\) Removes Mg$^{2+}$ \(\rightarrow\) \textbf{Pheophytin} (olive brown)
\textbf{Alkali} \(\rightarrow\) Removes phytol tail \(\rightarrow\) \textbf{Chlorophyllin} (bright green, water-soluble) \end{itemize}

Answer 1

The Correct Option is B

Step 1: Chlorophyll's structure includes a porphyrin ring complexed with a central magnesium ion, and a phytol tail. The phytol group makes chlorophyll soluble in fat.

Step 2: Alkali treatment (e.g., NaOH or KOH) causes saponification. This process cleaves the ester bond linking the phytol tail to the chlorophyll molecule, thus removing it.

Step 3: The resulting product is chlorophyllin, a salt. Chlorophyllin retains the porphyrin ring and magnesium ion, maintaining a green color. The removal of the phytol tail makes chlorophyllin water-soluble.
Acid treatment, conversely, replaces the magnesium ion with hydrogen, producing pheophytin, a dull olive-brown compound.