Whipped cream might be the best friend desserts have ever had. It adds feather-light richness and moisture to every bite, and contributes substantially to any dessert's visual appeal. It's not exactly low calorie, but it's a pleasant alternative to a heavy buttercream when you're decorating a cake in the midsummer heat. Unfortunately, heat and humidity cause whipped cream to break down quickly and lose its fresh color and flavor. You can extend its usable life by using thickeners or stabilizers.
You can whip your cream into froth peaks with anything from a heavy-duty stand mixer to a fork, though if you use a fork you'll need a lot of patience and an arm of steel. Start with very cold cream, because you need the butterfat as thick and cold as you can get it. As you whisk or beat the cream, those globules of butterfat are sheared by the wires of your beater and trap air as they re-establish bonds with each other. As you continue whipping and introducing air, they gradually form a relatively stiff and stable foam.
As its temperature rises, the fats in the cream soften, just like butter does at the table. The soft butterfats flow more easily and start to re-combine into larger globules. It's the same process you see when you shake a vinaigrette, then watch as the fat slowly separates out. In the case of whipped cream, your pretty white peaks slowly sink and darken as liquid cream re-forms at the bottom of your bowl or soaks into your cake. To slow this process, home and commercial bakers can work with a variety of stabilizing products.
Several companies manufacture powdered stabilizers for the home or commercial market. Commercial versions are sold in bulk, and bakers making gallons of whipped cream simply weigh the correct amount and pour it into their mixer. Stabilizers for home cooks usually call for two or three teaspoons of powder to be added to the cream before it's whipped. The powder dissolves in the liquid cream, then gels lightly as the cream sits. The gel binds up much of the liquid cream, slowing the deterioration of the foam.
One of the most effective stabilizers for home use is unflavored gelatin, which you probably already have in your pantry. For every cup of cream you're whipping, sprinkle 1 teaspoon of gelatin over 2 tablespoons of cold water and let it "bloom," or absorb the water. Microwave the gelatin to melt it and let it cool to room temperature as you begin whipping the cream. Once your cream is at the stage of making soft peaks, drizzle the gelatin into the bowl in a thin stream. Keep mixing until it's incorporated and the cream comes to stiff peaks.
You can also thicken and stabilize your whipped cream by folding it with other, thicker substances. For example, you can fold sour cream or creme fraiche into the whipped cream. Both will add a slight tang, which you can counter by increasing the sugar. Marshmallow fluff has the opposite effect, so omit any sugar from the whipped cream. A third option is prepared vanilla pudding, which has its own thickeners. Each of these changes the flavor and appearance of the whipped cream to some extent, so they're less versatile alternatives.