1. Over 100 samples of roller-dried full-cream milk and rather less than 100 samples of spray-dried milk reconstituted and incubated for 20 hr. at 55, 37, 39, 22 and 15·5° C. have been examined by the methylene-blue or resazurin-reduction tests at 37° C. The results have been compared with the plate count at 37 or 30° C. of the freshly reconstituted milk and with the keeping quality at 15·5° C.

2. A range of reduction times suitable for routine use was obtained after incubation at 22° C., but the results showed a very poor correlation with plate count at 37 or 30° C. and with keeping quality.

3. After incubation at 55, 37 and 30° C. the reduction times were too short, often showed delayed end-points, and the milk frequently clotted during examination.

4. Results with resazurin were similar to those using methylene blue and no significant differences resulted from the two different methods of reconstitution.