Principle:
This test is based on the principle that methyl blue (an oxidation-reduction dye or indicator) which is blue in its oxidized state, is reduced to colorless compound (leuco form) as a result of the metabolic activities of bacteria in milk. When a solution of dye is added, the organisms present in milk consume the dissolved oxygen and lower O-R potential to a level where methyl blue or similar indicators are reduced or decolorized.
Reagent Required:
Methylene Blue Reduction Dye
MBRT Procedure:
- Prepare a standard methylene blue solution by dissolving one tablet of methylene blue thiocyanate in 200 ml of sterile water.
- Add this to 10 ml of milk, shake well and keep in water bath.
- Note the time taken for the blue color to change to white.
- The total time gives MBRT time.
MBRT Test result and interpretations:
|
MBRT TEST RESULTS |
5 hrs and above | Very Good |
| 3 – 4 hrs | Good | |
| 1 – 2 hrs | Fair | |
| Half an hour | Poor |
Does this experiment distinguish between beneficial bacteria and those which are contaminants
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