methylene blue dye-reduction test

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methylene blue dye‐reduction test When the dye methylene blue or resazurin is added to milk, the bacteria present take up oxygen and change the colour of the dye; methylene blue loses its colour; resazurin changes from blue‐purple to pink. The speed of the change indicates the bacterial content. Pasteurized milk must not reduce dye in less than half an hour.

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