Foam with Thick Walls

Ice Cream, Whipped Cream, Mousse, and Soufflé

Appears in
Mouthfeel: How Texture Makes Taste
Mouthfeel

By Ole Mouritsen and Klavs Styrbæk

Published 2017

  • About
Some foods that are very rich in fats can form a type of foam without help—for example, cream, cheese with a high fat content, and even foie gras. In this type of foam, the fats stabilize the air bubbles, which lie far apart from one another, the opposite of what happens in a real foam. This is the case in whipped cream, ice cream, and whipped butter and margarine, all of which can contain up to 50 percent air.

Whipped cream is more complex than many other types of cream because it is actually a solidly packed network of air bubbles, held together by small spheres of fat that attach themselves to the surface of the air bubbles. Whipped cream can turn out to be just as stiff as a solid. As the fats are what hold the cream together, it is possible to make a stable foam only if the percentage of fat particles in the cream is sufficiently large, at least 30 percent and preferably greater. In addition, the larger fat particles in the cream must be broken up into pieces that are sufficiently small to be captured by the air bubbles. This process also releases the milk proteins from their original fat spheres, which makes them more unstable and increases their tendency to form larger fat particles. That is why the cream needs to be beaten, in fact, whipped to the stage where the fat particles are so small that they do not run together again before the stiff network of air bubbles is in place. This is also why temperature is important—when the cream is cold, it is much harder for the fat particles to coalesce. Whipped cream can also be made with the help of a siphon bottle using nitrous oxide (N2O). In the siphon, the gas is dissolved in the fat spheres of the cream, and when the pressure falls, a creamy foam with a very large number of air bubbles is formed.