Why Cream Rises

• Cream rises to the top of fresh or nonhomogenized milk because fat particles are larger and lighter than the particles in the milk. These fatty cream particles float on top of the milk. Before 1932, when homogenization was introduced as a way to create creamy milk with a smooth consistency, cream rose to the top of all milk. Although federal laws require pasteurization of milk sold for human consumption, homogenization is not required. However, nearly all milk sold at grocery outlets is homogenized.

Cream "Shrinking"

• Cream continues to rise from the milk for as long as the milk is stored, but gives the illusion that the amount of cream decreases. Because the fat particles of cream squeeze together at the top of the milk, the cream becomes densely packed. Although the layer then takes up less volume at the top of the milk, it actually contains more particles of cream. This equates to the terms heavy, medium and light cream, which refers to the density of the cream, not its volume.

Amount of Cream in Fresh Milk

• The amount of cream cow’s milk contains depends on several factors: the breed of cow, the stage of lactation and the season. Jersey cows lead the pack in producing the highest amount of cream in their milk, followed by Shorthorns, Guernseys and Holsteins. Cows produce more cream in the milk the longer time goes on since calving. They also produce more cream during cooler weather, and produce the most during the winter. On average, cows produce between 1 and 1 1/2 quarts of cream per gallon of milk.

Getting Cream from Milk

• Cream rises naturally in fresh milk. Scooping or pouring the cream from the top of the milk is how people collect the cream from fresh milk at home. Commercial producers separate cream from milk mechanically before homogenizing it to meet the desired fat content. Because homogenization breaks down the fat globules and blends them with the remainder of the milk, cream cannot be separated from homogenized milk.