Whole Milk Powder

Whole milk powder (WMP) is obtained by removing water from pasteurized, homogenized whole milk through evaporation and spray drying processes. It possesses all the appealing qualities of milk and, in its dry form, is an important ingredient in the manufacture of a remarkable range of food products.

WMP has a shelf life of about 6 months. Since the product contains a high level of milkfat, deterioration in taste, caused by the tendency of fat to oxidize, can be prevented by introducing a nitrogen or carbon dioxide atmosphere or vacuum sealing at time of packaging. WMP should be kept in a cool, dry storage room and should not be exposed to direct sunlight or strong odours. The product should not come into contact with walls or floors.

Whole milk powder must contain no less than 95percent milk solids and must not exceed 5percent moisture. The milk fat content must be no less than 26 percent. Vitamins A and D may be added and the emulsifying agent lecithin may also be added in an amount not exceeding 0.5 percent.

Strict microbiological requirements are placed on the quality of the raw milk that is used in the manufacture of milk powders. Accordingly, WMP should be free from bacteria of the genus Salmonella and antibiotics. One gram of powder must not contain more than 10,000 bacteria as measured by the Standard Plate Count, 10 coliforms and 100 Staphylococcus aureus. These counts correspond respectively to about 1000, 1 and 10 per liter of reconstituted product, provided that contamination does not occur after manufacture.

• Appearance: WMP must be reasonably uniform in composition, white- or cream-coloured, free of graininess on reconstitution and free of burnt particles. It possesses a sweet, pleasant flavour and may have a slight degree of cooked flavour but no off-flavours.
• Varieties: Two types of WMP are manufactured in Canada: regular WMP and instant WMP. Although soluble, the milk powder does not dissolve easily in water. The reconstitution of milk from powder requires lukewarm water (30-50 EC) and mechanical stirring. However, if milk powder is to dissolve quickly, as is advantageous for household uses, it must be instantized. Instantized WMP is prepared by the addition of an emulsifier, lecithin (up to 0.5 percent), which mixes with the very thin layer of fat and makes the powder wet. The "instantization" allows it to dissolve quickly in water without stirring or mixing.

For further processors, the major components of milk, i.e. milkfat, proteins and the milk sugar, lactose, are probably of greatest importance since most of the functional properties reside with theses constituents. However, this is not to say that other components, such as calcium and phosphate, are not functionally important. Thus, several desirable properties are achieved by adding whole milk powder to food formulations.