Is Raw milk is safe for human consumption.

No. Raw milk is not safe for human consumption.

Raw milk can cause serious illnesses. Raw milk and raw milk products, including soft cheese, ice cream, and yogurt, can be contaminated with harmful bacteria and other germs that can cause serious illness, hospitalization, or death. These harmful germs include Brucella, Campylobacter, Cryptosporidium, E. coli, Listeria, and Salmonella.

Raw milk is milk from any animal that has not been pasteurized to kill harmful bacteria. Raw milk can carry harmful bacteria and other germs that can make you very sick or kill you. While it is possible to get foodborne illnesses from many different foods, raw milk is one of the riskiest of all.

Some people who chose raw milk thinking they would improve their health instead found themselves (or their loved ones) sick in a hospital for several weeks due to infections caused by germs in raw milk. Getting sick from raw milk can mean many days of diarrhea, stomach cramping, and vomiting. Some people who drank raw milk have developed severe or even life-threatening diseases, including Guillain-Barré syndrome, which can cause paralysis, and hemolytic uremic syndrome, which can result in kidney failure, stroke, and even death.

METHYLENE BLUE REDUCTION TEST (MBRT)

INTRODUCTION:-

        Milk is a good medium for the growth of microorganism. A variety of microorganism can be found in both raw and pasteurised milk. These actively growing microorganism reduce the oxidation reduction potential of milk medium due to the exhaust oxidation of microorganism. Normally milk is contaminated with microorganism such as Staphylococcus aureus, Streptococcus progenies etc. Contaminated milk is one of the important source for the transmission of disease from animal to human. The main reason for this contamination is improper handling of milk. Normally milk is contaminated during milking process by the microorganism present in the exterior surface of the animals by place such as udder and adjacent area. Unsterilised dairy utensils such as milking machines and milk cans are also a good source of contamination by the microorganism. The formation of methylene blue reductase is thus becoming a popular tool for determining the quality of milk. 

 

PRINCIPLE:-

         The test is based on the principle that methylene blue (an oxidation-reduction dye or indicator) which is blue in its oxidized state is reduced to colorless compound (Leuko form) as a result of the metabolic reaction in milk. 

Conversion of methylene blue to leucomethylene blue

             Methylene blue is a redox indicator that loose its color under the absence of oxygen and its to be reduced. The bacteria in the milk consume the dissolved oxygen and lower the O-R potential to a level when methylene and similar indicators are reduced. This brings about the change, that the milk gets decolorized. The time taken for the reduction of the dye (MBRT) is influenced by the number and types of organisms present in the milk greater their activity the more rapidly is the dye reduced. The greater is the number of microorganisms in milk, the greater is the metabolic activity and the faster is the reduction of methylene blue. The MBRT thus gives an indication of bacterial numbers and activity in milk. 

 

WHY MBRT IS DONE?

The MBRT test is therefore used for 

    (i)   Judging the hygienic quality of milk and grading raw milk supplies, 

   (ii)   For assessing the quality of the probes of milk,

   (iii)  For detecting post pasteurization contamination in milk.

 

MATERIALS:-

• Thermostatically controlled water bath maintained at 3C +_ 0.5C.
• Sterile test tubes without rim (150x16mm) preferably with marking at 10ml.
• Sterilized rubber rings to fit into the above test tubes. The rubber brings together with forces that are held in boiling water for 10 minutes pricer to use.
• 10.0 ml and 1.0 ml pipettes.
• Clock, watch, or an interval timer.
• Forceps, beaker, and flasks.
• Standards methylene blue solution.
• Two samples of milk in sample bottles (one fresh milk and the other poor-quality sample).

 

METHYLENE BLUE SOLUTION:-

         A standard solution of methylene blue is prepared by dissolving on the tablet of approved methylene blue thiocyanate or chloride (B.D.H or Merck) in 200ml of cold sterile glass distilled water in a sterile flask by gentle heating in a water bath of by allowing the mixture to stand for several hours to facilitate a complete solution and then adding 600ml of sterile glass distilled water. 1 ml of this solution and then adding 600ml of sterile, class distilled water. C ml of this solution mixed with 10 ml of milk result in obtaining a final concentration of 1/300000 for the dye which has been found to be satisfactory for the test. The stock solution must be stored to be a sterile glass stoppered amber-colored bottle in a dark place. The fresh solution must be prepared once in two months.

 

PROCEDURE:

1.   Thoroughly mix the samples of the milk.

2.   Transfer 10ml of each sample of milk into a tube.

3.   Mix the dye and the milk by inverting the tubes twice.

4.   Place the tubes in the water bath.

5.   Observe the test tubes after every 30 minutes and if there is no sign of reduction (decolorization) the tubes are inverted once and returned to the water bath. If the decolorization has commerced the tubes should not be inverted or shaken.

6.   Continue the observation until the complete reduction of the dye (complete decolorization) occurs or the formation of persistent blue rings (0.5mm) at the top.

7.   Record the time taken for the reduction of methylene blue.

8.   Tabulate the results.

 GRADING OF MILK AS PER BIS STANDARDS:-

 

S.No	Reduction Time	Quality
1	More than 8 hours	Excellent
2	6 - 8 hours	Good
3	2 - 6 hours	Fair
4	1 - 2 hours	Poor
5	1/2 and below	Very Poor

 

FACTORS AFFECTING THE MBRT:-

These are factors that affect the MBRT and therefore, the steps of operation should be uniform.

1.  Since, the oxygen content must be used up before the colour disappears; any manipulation that increases the oxygen content affects the test.

Ø Cold milk holds more oxygen than warm milk.

Ø Pouring milk back and forth from one container to another increases the oxygen.

Ø During milking time much oxygen may be absorbed.

2.  The rate of reduction of dye depends on the type of microorganism

Ø Coliforms appear to be the most rapidly reducing microorganisms.

Ø Closely followed by Lactococcus lactis spp. lactis, some of the faecal Streptococci, and certain micrococci.

Ø Psychrotrophs reduce methylene blue very slowly.  

3. Presence of a large number of leucocytes as in mastitic milk will affect the reduction time materially.

4. Light hastens reduction process and therefore, the tests should be carried out in relatively low light.

5. Concentration of dye should be uniform as an increased concentration lengthens the time of reduction.

6. Increasing the incubation temperature augments the activity of the bacteria and therefore shortens the reduction time.

7.  Creaming of milk causes a number of micro-organisms to be removed from of milk and brought to the surface with the rising fat. This factor causes variations in the reduction time, since the bacteria are not evenly distributed.

8. The accuracy of test is increased, reduction time shortened and decolourization more uniform, if the samples are  periodically inverted during incubation.