It is evident from the foregoing results that decreases in count may occur during the storage of milk and whey powders. The extent of this decrease varies, however, with the type of powder and even between different samples of the same type. Further, many samples may show little or no alteration in the numbers of viable organisms surviving storage even for considerable periods.

Nevertheless, it is obviously important that for grading purposes or in relation to plant control a time limit should be fixed within which the plate count of any milk or whey powder should be determined. No data are available to show how rapidly organisms may die out during storage periods of less than 3 months, but it is tentatively suggested that all powders should normally be examined within, say, 14 days of manufacture. Unless such a limit is fixed, those samples in which the count does fall appreciably would reflect too favourably on the conditions of manufacture.