Statutorily designated (UK) milk test in which 10 ml of milk (from a sample stored overnight at a temperature not above 70°F) must not completely decolorize 1.0 ml of a standardized methylene blue solution with which it is mixed in a 152 x 16 mm (reductase) tube. The tube is incubated for 30 minutes, and the extent of the decolorization at this time is an index of bacterial content in the sample.