You've seen it in your grocery store's spice aisle. You know that it's a necessary ingredient for some baked goods, but the name is still confusing. The substance itself isn't even a cream; in fact, it's a fine white powder. What is it, and why is it called cream of tartar. It's actually an acid that's been transformed into a salt. Its chemical name is potassium bitartrate, and its job is to keep sugar from crystallizing. It's used anywhere chefs want to create sweet-tasting yet smooth substances (think syrup or homemade frosting).
Ingredient #1: Tartaric Acid
Tartaric acid is a plant acid that's found naturally in grapes. This acid is responsible for much of a wine's flavor; wines that are bland have too little, while wines that are sharp or acidic have too much. When grapes are trampled to make wine, there's always a bit of sediment left behind. This sediment is a source for tartaric acid. It is heated and mixed with ingredient #2 to neutralize the acid. Once this chemical reaction takes place, you're left with potassium bitartrate (cream of tartar.)
Ingredient #2: Potassium Hydroxide
Potassium hydroxide is a chemical compound that can be dangerous if not handled properly. It's more commonly known as lye, and sometimes called "caustic potash." An odorless powder that's either white or yellow, it creates a chemical reaction when added to water or put in contact with an acid. When it comes in contact with water, it generates enough heat to produce steam. When mixed with tartaric acid, it neutralizes about half the tartaric acid's acidity and turns it into a salt that's suitable to use in cooking. The resultant white powder is what you'll see in your grocery store's spice aisle.
Uses for Cream of Tartar
Cream of tartar's most common use is in baking. Its natural acid keeps the texture of mixed ingredients smooth-as in meringue, gelatin and frosting. Cooking Light magazine recommends adding 1/8 teaspoon per egg while beating eggs for meringue; it will create the frosty, stiff peaks you want when topping lemon meringue pie, for example. There's another common household use for cream of tartar that you probably didn't expect, as it has nothing to do with baking; use it to polish your copper or brass pots and pans.
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