Question

Rosalic acid test is used for detection of ..........adulterant in milk.

• A. Neutralizers
• B. Formaldehyde
• C. Starch
• D. Urea

Hint:

Associate the color indicator "Rosalic acid" with "rose-red/pink", which indicates the alkaline conditions created by "Neutralizers" in milk.
Formaldehyde is detected using Hehner's test, while starch is identified using the iodine test.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Milk adulteration is a major concern in dairy technology.
Adulterants like neutralizers are chemically basic substances added to milk to mask spoilage and artificial extension of shelf life.
Key Principle:
When milk is stored under poor hygienic conditions or at high ambient temperatures, lactic acid-producing bacteria grow and increase the acidity of the milk.
To neutralize this developed acidity and pass quality checks (such as the Clot-on-Boiling test), unscrupulous suppliers add alkaline chemicals like sodium carbote, sodium bicarbote, or sodium hydroxide.

Step 2: Detailed Explation:
The Rosalic acid test is a rapid, colorimetric chemical test designed specifically to detect these alkaline neutralizers.
Rosalic acid (also known as aurin) acts as a pH indicator.
In pure, udulterated milk, which has a slightly acidic to neutral pH of approximately 6.6 to 6.8, the addition of an alcoholic solution of rosalic acid yields a characteristic brownish-pink or orange-yellow color.
However, if alkaline neutralizers have been added to the milk, the pH increases and the carbote/bicarbote ions interact with the indicator.
This reaction results in a distinct, bright rose-red or pink color.
This test is highly sensitive and can detect even trace amounts of added carbotes.

Step 3: Fil Answer
Thus, the Rosalic acid test is used for the qualitative detection of added neutralizers in milk.