Exp. No. 2 Milk quality test – MBRT

 

Exp. No. 2 Milk quality test – MBRT

Introduction

            Lager number of bacteria present in milk indicates the poor methods of production or handling. From the time the milk leaves the udder, until it is dispensed into container, everything which come in contact with potential sources the oxygen present in the sample thus lowering oxidation –reduction potential due to the exhaustion of dissolved oxygen when methylene blue is mixed with contaminated milk; it loses its colour. The colour disappearance of methylene blue is directly proportional to the number of bacteria present in the sample.

Aim

To determine the quality of the given milk sample by methylene blue reductase test.

Materials and Methods

Methylene blue (1:2500), Milk sample, screw cap tube, pipettes, etc.,

Procedure

·       The raw milk sample was collected in a sterile conical flask.

·        Transferred 10 ml of milk sample to sterile screw cap tube.

·        1ml of methylene blue solution was added to all screw capped tubes.

·        The tubes were closed with rubber stopper and gently inverted thrice to mix all contents.

·        Control tube with dye also maintained.

·        Incubated all the tubes in water bath at 35⁰C for up to eight hours.

·        The tubes were observed for colour change during every half an hour.  Quality of milk sample was assessed on the basis of standard given in table.

Class	Interpretation
I	Excellent – not discolorized up to 9 hours
II	Good – Discolorize after 6 hours but within 8 hours
III	Fair – Discolorize after 2 hours but within 6 hours
IV	Poor – discolorize within 2 hours

 

 

 

 

 

Observation

S. No	Sample	Time of discoloration (in minutes)															Milk Quality
		30	60	90	120	150	180	210	240	270	300	330	360	390	420	480
1	A
2	B
3	C
4	D
5	Control 1
6	Control 2

 

 

Result

The given milk was found to be good as it decolourises after 6hrs but within 8hrs.