Question

____________ is nonsaponifiable matter.

• A. Fat
• B. Sterols
• C. Waxes
• D. Phospholipids

Hint:

The unsaponifiable fraction of fats and oils consists of lipid-soluble compounds without ester bonds, primarily sterols, tocopherols (Vitamin E), squalene, and fat-soluble pigments like carotenoids.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Lipids extracted from food materials contain saponifiable and unsaponifiable (or non-saponifiable) fractions.
Saponifiable lipids contain ester linkages (such as triglycerides, phospholipids, and waxes) that can be hydrolyzed by alkalis (like KOH or NaOH) to form water-soluble soaps and glycerol.
Non-saponifiable lipids lack these ester linkages and cannot be converted into soap.

Step 2: Detailed Explanation:
Let us analyze the chemical properties of each option:
- Fats (A): Primarily composed of triglycerides (esters of glycerol and three fatty acids). They are easily saponified by alkalis to form soap and glycerol.
- Waxes (C): Esters of long-chain monohydric alcohols and long-chain fatty acids. Although they are highly resistant to hydrolysis, they contain ester bonds and can be saponified under harsh alkaline conditions.
- Phospholipids (D): Polar lipids composed of glycerol esterified to two fatty acids and a phosphate group. They contain saponifiable ester linkages.
- Sterols (B): Complex, high-molecular-weight polycyclic alcohols (such as cholesterol in animal fats, and phytosterols in vegetable oils).
Because they are structured around a steroid ring system without ester linkages, they cannot be hydrolyzed or converted into soaps by alkaline treatment.
During saponification, sterols remain dissolved in the unsaponifiable lipid fraction and can be extracted using organic solvents like ethyl ether or petroleum ether.
Therefore, sterols are classified as non-saponifiable matter.

Step 3: Final Answer:
Among the listed lipids, sterols are classified as non-saponifiable matter.