The reason that we have been hearing more about skim milk powder lately is because the United States is becoming a larger player in the world market for milk powders, and skim milk powder is the commodity that is most often traded on world markets.

There are small but important distinctions between nonfat and skim milk powders to the users of these powders. Both products are typically made from spray drying skim milk, and there are product specifications for each of them such as “Moisture content not more than 4 percent” and “Milkfat content not more than 1.25 percent,” etc. The difference between the two products is that skim milk powder also has a standard for protein content—“Not less than 34 percent.”

Nonfat dry milk is made from drying skim milk, but the resulting product usually has a protein content that can vary between 34 and 37 percent. Because this process can result in a protein content of the powder of greater than the minimum 34 percent, this sometimes means the manufacturer is not paid more for a product that has a higher protein content. As a result, nonfat dry milk is often dry blended with (lower-cost) lactose powder to bring the protein content down to 34 percent.

Alternatively, a process known as ultra-filtration is used on skim milk to take out much of the lactose, minerals, and water. This “permeate” may be blended back into the skim milk stream before drying to dilute the protein in the dried product to a level of 34 percent.

More generally, ultra-filtration is one example of developments in processing technologies that can be used to create valuable ingredients from milk, often because of their specific properties when used in food products.

Mark Stephenson, Cornell Program on Dairy Markets and Policy