Methylene Blue Reduction Test (MBRT) is conducted to know the efficiency of?

🔑Key Points:
Methylene Blue Dye Reduction Test, commonly known as MBRT test is used as a quick method to assess the microbiological quality of raw and pasteurized milk.
The Methylene Blue Reduction Test is based on the fact that in the presence of oxygen the methylene blue solution forms blue color, and it will lose the color as the oxygen is depleted.
The bacteria present in the milk will ferment lactose (milk sugar) to form lactic acid, during this fermentation process the oxygen is used up, which causes in depletion of oxygen in milk, and electrons are released. 
These electrons react with the methylene blue solution.  As a result, it decolorizes the methylene blue.
Grading of milk based on MBRT as per BIS standard

• MBR Time and Quality of Raw Milk:
5 hours and above: Very good
3 to 4 hours: Good
1 to 2 hours: Fair
1/2 hour and below: Poor

🛑Important Points:
 Whole milk – Milk derived from animals without altering the composition is termed as whole milk. Cow whole milk contains fat not less than 3.5%, SNF not less than 8.5%.  Buffalo whole milk contains fat not less than 6%, SNF not less than 9%. 
Standardized milk – Contain minimum 4.5% fat and 8.5% SNF 
Toned milk – Milk obtained from the addition of water and skim milk powder to whole milk. Toned milk should contain a minimum of 3% fat and 8.5% SNF.
Double toned milk – As per rules double toned milk should contain a minimum of 1.5% fat and 8.7-9% SNF. 
Reconstituted milk – Milk prepared by dispersing whole milk powder into water approximately in proportion of one-part powder to 7 to 88 parts of water. 
Recombined milk – A milk product obtained when butter oil, Skim milk powder and water are combined in the correct proportion to yield fluid milk.