Whipped cream

For cream to be whipped successfully, it must contain a minimum of 30 percent fat. This is the reason you can not whip whole milk or half-and-half, for example, as they contain 4 and 18 to 20 percent fat, respectively. As air is beaten into the cream, tiny bubbles of air and fat become encased in a thin film of water. This is an example of an emulsion.

As more air is incorporated, the coating of water around each bubble of air and fat becomes progressively thinner. Eventually, the water coating becomes so thin that the fat globules break through and start to stick together. At this point, the cream starts to become thicker and firmer. If this process is taken to the extreme, all of the fat particles become attached to one another to the point where most of the air and water are forced out; the result is a solid mass of fat, also known as butter.