Question

MBRT of properly pasteurized milk shall not be less than

• A. 5 hours
• B. 3 hours
• C. 2 hours
• D. 1 hour

Hint:

For the MBRT, remember: {Longer time = Better quality}. Raw milk might be graded as "Good" if it takes 3-5 hours, but for pasteurized milk, the standard is much stricter, requiring the longest time bracket, which is 5 hours.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
MBRT stands for the Methylene Blue Reduction Test. It is a rapid, indirect method to assess the microbiological quality of milk. The time it takes for the blue dye to become colorless (reduced) is an indicator of the bacterial load.
Step 2: Detailed Explanation:
The principle of the test is based on the metabolic activity of bacteria. When bacteria grow in milk, they consume oxygen and lower the oxidation-reduction potential of the milk. Methylene blue is a redox indicator that is blue in an oxidized state and colorless in a reduced state.
High bacterial count: The oxygen is used up quickly, the potential drops, and the methylene blue is reduced (decolorized) in a short time.
Low bacterial count: The metabolic activity is low, and it takes a long time for the dye to be reduced.
Properly pasteurized milk should have a very low count of viable bacteria. Therefore, its MBRT time should be very long. According to food safety standards (like FSSAI in India), the Methylene Blue Reduction Time for properly pasteurized milk must not be less than 5 hours. This long time indicates that the pasteurization was effective in killing most of the bacteria.
Step 3: Final Answer:
The MBRT time for properly pasteurized milk shall not be less than 5 hours.