Question

Presence of ____________\in milk is detected by preparation of soap from fat part of milk.

• A. Lard
• B. Mineral oil
• C. Coconut oil
• D. Vanaspathi

Hint:

Mineral oils are hydrocarbons and cannot be saponified. They are easily detected because they fail to form soap and separate out as an oily layer.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Adulteration of milk fat (ghee) with cheap foreign fats or oils is a major quality issue.
Detection of these adulterants relies on differences in their saponification properties when reacted with a strong alkali.

Step 2: Detailed Explanation:
Soap is produced by the saponification of saponifiable lipids (triacylglycerols) with an alkali like potassium hydroxide, yielding glycerol and potassium salts of fatty acids (soap).
Natural animal fats and vegetable oils (including lard, coconut oil, and vanaspathi) are saponifiable because they consist of triacylglycerols.
In contrast, Mineral oil consists of liquid hydrocarbons (paraffins) that lack ester bonds.
Consequently, mineral oil is unsaponifiable and cannot form soap.
When an adulterated fat sample containing mineral oil is boiled with alcoholic potassium hydroxide, the natural milk fat saponifies completely to form a clear, soluble soap solution.
The unsaponified mineral oil remains unchanged and separates as an oily layer on the surface or causes a distinct turbidity upon dilution with water.
This separation of unsaponifiable matter is the basis for detecting mineral oil adulteration in milk fat.

Step 3: Final Answer
The correct option is (B).