Reduction Test

Reduction Test

Reduction Test -

This is a rapid test to find relative amount of bacteria in a milk sample. The principle used is that the length of time for a colour change in a specific dye is proportional to the number of bacteria in the sample.

A sample of milk is mixed with the dye solution.(methylene blue or resazurin) and this is incubated.

Due to growth of bacteria and subsequent fermentation of lactose of milk, the electrons released are passed along to the dye molecules, reducing them. The enzyme involved is a reductase.

On reduction, methylene blue loses its colour and resazurin changes from normal slate blue to pink or colorless form.

Good quality milk normally shows minimal colour change even after five to six hours, whereas contaminated milk shows color change rapidly within two hours or so.

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