You've probably come across this item in a cabinet or pantry and been like, "cream of what now?" or, "like tartar control toothpaste?" It's not cream or a toothpaste component — the name makes no sense. Not much of a baker? You probably don't need this stuff around. But if you've ever felt the need to break out the spring-form pan and pastry bag and bake your feelings away, pick up a little can of this stuff. You only need a tiny bit.
Cream of tartar is the culinary name for potassium bitartrate, a by-product of winemaking. It's actually a purified form of the residue found in wine fermentation tanks. It's used to stabilize egg whites when beating them to stiff peaks, helping them hold their shape and add volume to meringues. Another useful trait is its ability to keep whipped sugar (like in frosting) from crystalizing, helping to keep it smooth and uniform.
If you run out of baking powder but still have cream of tartar, you might still be able to to churn out that cake. Two parts cream of tartar plus one part baking soda and one part cornstarch equals baking powder.
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