Bacteriological Changes During the Manufacture of Nonfat Dry Milk

Abstract

Summary Three media were used to assess the bacteriological changes during the manufacture of spray-dried nonfat milk in two processing plants. The plants differed in the equipment and practices employed and in the quality and quantity of milk processed. The plant processing raw milk of the lower grade and maintaining better control of the drying procedure produced nonfat dry milk of higher bacteriological quality than the plant processing raw milk of higher grade but using less efficient equipment and less controlled industrial practices. In the plant using less efficient equipment and practices, multiplication of coagulase-positive staphylococci occurred at one stage of processing. Multiplication was extensive in one trial. The nonfat dry milk produced at both plants met the bacteriological standard for Extra Grade powder. This indicates that a low total bacterial count for nonfat dry milk may be misleading as an indication of the safe quality of the product.