Whipped cream

Whipped cream is simply whipping cream that has been agitated in order to form a stable foam. Before the advent of mechanical cream separation (through centrifuges), whipped cream was a herculean task, requiring cream to be whipped for hours, and the resulting foam pulled off the top and left to drain. Once mechanical separation boosted cream's fat content above 30 percent, whipped cream became much easier to make.

Whipped cream is nothing more than air stabilized by fat molecules. As the whisk shears these molecules, they form a skin around introduced bubbles of air. After a few minutes of work, there are enough stabilized bubbles to turn liquid into a semi-solid foam. 

One of the most important things to be aware of when whipping cream is that everything should be refrigerator-cold. Cream should be chilled for at least 12 hours before whipping, as this promotes crystals of butterfat to form in solution, which gives maximum volume and more stability. It is also helpful to very slightly acidify the cream with lemon juice, which makes it easier to shear away fat membrane protiens. 

While whipped cream can be produced in many ways (hand-whipping, in an ISI whipper, or in a machine), the nitrous oxide in an ISI whipper makes the lighest and finest whipped cream, followed by hand-whipping.