Question

A ‘Milk clarifier' DOES NOT remove the following from raw milk:

• A. Leucocyte
• B. Bacteria
• C. Dust and dirt
• D. Fiber

Hint:

A standard milk clarifier removes somatic cells (leucocytes), hair, and dirt, but cannot remove bacteria due to their minute size. Bacteria removal requires a specialized Bactofuge.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Centrifugal clarification of milk is a pre-treatment process used to remove solid impurities from raw milk using centrifugal force.
A milk clarifier separates particles based on differences in density between the milk plasma and the foreign matter.

Step 2: Detailed Explanation:
A milk clarifier is highly effective at removing dense, large particulate matter suspended in milk:
- Dust and dirt: Soil and environmental debris have a high density ($> 2.0\text{ g/cm}^3$) compared to milk ($1.03\text{ g/cm}^3$) and are quickly forced into the sludge space of the clarifier bowl. (Removed)
- Fiber: Animal hair, fodder fragments, and straw fibers are large and dense enough to be separated efficiently. (Removed)
- Leucocytes: Somatic cells and epithelial cells from the udder are dense cells that form a major portion of the "clarifier slime" or sludge. (Removed)
- Bacteria: Although bacteria have a slightly higher density than milk plasma, their extremely small size ($< 1\text{ }\mu\text{m}$) means the centrifugal force in a standard milk clarifier is insufficient to separate them from the milk phase.
To remove bacteria centrifugally, specialized high-force centrifuges called bactofuges must be used.
Therefore, a standard milk clarifier does not remove bacteria from raw milk.

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