Factors Affecting the Direct Microscopic Clump Count of Nonfat Dry Milk

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Abstract
The relationship between the DMC of raw skim milk and the DMC of the NDM made from it was found to vary widely within days and seasons of the year. The DMC/g of the NDM ranged from 1.9 times to 71.0 times the DMC/ml of the skim milk on 44 trials. The average increase was 9.1 times. Factors which were found to influence this relationship were: (a) The effect of breaking up of clumps due to agitation; (b) the removal of bacterial cells during the separation of the whole milk and subsequent clarification of the skim milk; (c) the amount of heat treatment given the skim milk during processing; (d)the length of time of cold storage of condensed milk prior to drying; and (e) the effect of drying. Because of the variations in the relationship between the DMC of the raw milk and the DMC of the NDM, and because of the many factors which may affect this relationship, the DMC of NDM does not appear to be a reliable method for evaluating the bacterial population of the raw milk from which the NDM was made.