Question

Which test detects urea adulteration in milk?

• A. Diacetyl test
• B. p-Dimethylaminobenzaldehyde test
• C. Molisch test
• D. Benedict test

Hint:

Urea adulteration is checked using DMAB because of the rapid, distinctive chromogenic reaction resulting in a yellow complex.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the chemical test that specifically detects the presence of added urea in milk.

Step 2: Key Formula or Approach:
Urea is an adulterant added to synthetic or diluted milk to artificially elevate the non-protein nitrogen levels, which misleads testing for crude protein content.
Urea undergoes a rapid condensation reaction with p-Dimethylaminobenzaldehyde (DMAB) in an acidic environment to form a yellow-colored compound.

Step 3: Detailed Explanation:

• p-Dimethylaminobenzaldehyde (DMAB) Test: Also referred to as the parade test. In the presence of concentrated acid, DMAB reacts with urea to yield a stable, distinct yellow color. Normal milk yields only a very pale, standard color under similar conditions.

• Diacetyl test: Used to check for the presence of diacetyl, which is a butter-aroma compound, and does not react with urea.

• Molisch test: A general chemical test used to confirm the presence of carbohydrates in a solution.

• Benedict test: A copper-reduction test used specifically to detect reducing sugars like lactose or glucose.

Step 4: Final Answer:
Therefore, the p-Dimethylaminobenzaldehyde test is the correct chemical method.