Upon standing, unhomogenized milk naturally separates into two layers: a milk fat–rich cream on top and almost fat-free (or skimmed) milk on the bottom. Commercially, the cream is separated from the milk by centrifugal force. Almost all cream that reaches the market today has been pasteurized. There are many varieties of cream, all categorized according to the amount of milk fat in the mixture. Heavy cream, also called heavy whipping cream, is whipping cream with a milk fat content of between 36 and 40 percent. It's usually available only in specialty or gourmet markets. Whipping cream will double in volume when whipped. Light cream, also called coffee or table cream, can contain anywhere from 18 to 30 percent fat but commonly contains 20 percent. Light whipping cream, the form most commonly available, contains 30 to 36 percent milk fat and sometimes stabilizers and emulsifiers.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.