The Act of July 2, 1956 (21 U.S.C. 321c), defines nonfat dry milk as "the product resulting from the removal of fat and water from milk, and contains the lactose, milk proteins, and milk minerals in the same relative proportions as in the fresh milk from which made. It contains not over 5 per centum by weight of moisture. The fat content is not over 11⁄2 per centum by weight unless otherwise indicated.", and defines milk to mean sweet milk of cows.

1956年7月2日的法令（21 U.S.C.321c）将脱脂干奶定义为：除去奶里的脂肪和水分的产品，而乳糖、奶蛋白和矿物质仍保持与鲜奶相同的比例。水分含量不超过总重量的5%。除非另有说明，脂肪含量不超过总重量的2%。另外还定义"奶"指牛的甜奶。