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: Concept Overview:
The Methylene Blue Reduction Test (MBRT) is a rapid, indirect method for assessing milk's microbiological quality. The time for methylene blue to decolorize reflects the bacterial load.
Step 2: Detailed Explanation:
The test relies on bacterial metabolic activity. Bacteria in milk consume oxygen, lowering its oxidation-reduction potential. Methylene blue, a redox indicator, is blue when oxidized and colorless when reduced.
High bacterial count: Rapid oxygen depletion quickly lowers the potential, leading to fast methylene blue reduction (decolorization).
Low bacterial count: Slow metabolic activity results in a longer time for dye reduction.
Properly pasteurized milk has a minimal number of viable bacteria, resulting in a long MBRT time. Food safety standards, such as FSSAI in India, specify a minimum MBRT of 5 hours for properly pasteurized milk. This extended time confirms effective pasteurization.
Step 3: Conclusion:
The minimum acceptable MBRT for properly pasteurized milk is 5 hours.