Question

COB test is used for detection of

• A. Urea in milk
• B. Developed acidity of milk
• C. Sugar in Milk
• D. Bicarbonate in milk

Hint:

Remember the common platform tests for milk quality: COB (for developed acidity/heat stability), alcohol test (another test for heat stability), and lactometer reading (for detecting added water).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The COB test, which stands for "Clot on Boiling," is a rapid platform test used in dairy processing plants to assess the heat stability of raw milk.
Step 2: Detailed Explanation:
Fresh milk has a certain natural acidity and is heat-stable. However, if milk is not stored properly, bacteria will grow and ferment the lactose into lactic acid. This is called "developed acidity".
As the acidity increases (and the pH drops), the casein proteins in the milk become less stable. When such milk is heated to boiling, the proteins coagulate and form a clot or curd. The COB test involves simply boiling a small sample of milk.
If the milk remains liquid, it passes the test (COB negative).
If the milk clots or curdles, it fails the test (COB positive), indicating it has high developed acidity and is not suitable for heat processing like pasteurization.
Therefore, the test is a direct indicator of developed acidity. Urea, sugar, and bicarbonate are adulterants that are detected by other specific chemical tests.
Step 3: Final Answer:
The Clot on Boiling (COB) test is used to detect high levels of developed acidity in milk.