Question

Given below are two statements:
Statement I: Methylene blue reduction test is based on the oxidation-reduction potential of milk
Statement II: Methylene blue chloride is the salt used for Methylene blue reduction test
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

MBRT Principles:
1. Based on Oxidation-Reduction Potential ($E_h$) of milk.
2. Uses Methylene Blue Chloride Thiocyanate salt.
3. Shorter reduction time = Higher bacterial contamination.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bacteriological dye reduction testing: MBRT measures the rate of microbial metabolic electron transfer depressing milk redox potential ($E_h$), utilizing standardized pharmaceutical salts of methylene blue (methylene blue chloride methylene blue thiocyanate tablets).
Key Formula or Approach:
\[ \text{MBRT: Active Microbial Respiration} \implies \text{DO Depletion } + E_h \text{ Drops } (+0.30\text{V} \rightarrow +0.06\text{V}) \implies \mathbf{\text{Methylene Blue (Blue)} \xrightarrow{\text{Reduced}} \text{Leucomethylene Blue (Colorless)}} \]

Step 2: Detailed Explanation:
1. Statement I: The Methylene Blue Reduction Test (MBRT) is a rapid bacteriological grading method based directly on the Oxidation-Reduction Potential ($E_h$) of milk. Growing bacteria consume dissolved oxygen and donate electrons, dropping the redox potential from $+0.30\text{ V}$ to $+0.06\text{ V}$, which reduces colored blue methylene blue to colorless leucomethylene blue. Hence, Statement I is true.
2. Statement II: Standard MBRT tablet formulations (standardized by National Collection of Dairy Organisms Standard Methods) are manufactured using certified Methylene Blue Chloride (or Methylene Blue Thiocyanate salt, $8.8\text{ mg}$ dye/tablet) to prepare standardized $1:25,000$ aqueous working dye solutions. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Both Statement I and Statement II are true, corresponding to option (A).