Today’s recipe for Butterscotch Wafers reminds me how much of cooking is chemistry. Why, you ask? Well, this recipe calls for cream of tartar. Many recipes that use egg whites also call for cream of tartar, but many of us don’t know why. It’s just something about making the egg whites rise nicely, right? So I did a little searching, and as it turns out, cream of tartar is a really interesting compound. The chemical name is potassium bitartrate and is a byproduct of wine making and the processing of grape juice. It has been called “wine diamonds” in the past as the crystalized potassium bitartrate would cling to the underside of a cork in certain conditions. Cream of tartar is derived from these crystals. In baking, cream of tartar is an acid that can help to stabilize egg whites or whipped cream when beating, or even be used as a household cleaner when mixed with something acidic such as lemon juice. The cream of tartar changes the ph of egg whites just enough to stabilize the proteins when egg whites are whipped into a foam, thereby allowing the oxygen that has been beaten into the whites to remain sturdy. The resulting baked items (angel food cake, merengues, etc) will be more glossy, white, and airy. Be sure to click through the links after the recipe for more information.
I find it really funny after that chemistry lesson to read that the recipe does NOT have you mix the cream of tartar into the egg mixture, but instead add it to the dry ingredients. I wonder how it would be different if you made that switch. I suspect however, that it is being used to prevent the sugars from crystalizing during baking, which is another use of cream of tartar.
2 c brown sugar
3/4 c shortening
1 teas soda
1 teas cream of tartar
3/4 teas salt
3 c flour
Cream shortening. Work in sugar gradually. Beat in eggs. Continue beating until fluffy. Sift dry ingredients. Add to first mixture. Shape into 2 rolls about 2 inches in diameter. Place in ice box over night. When ready to bake, cut in thin slices. Bake at 350 degrees F (moderate oven) for about 10 minutes.
What is cream of tartar via slate.com
Potassium bitartrate via wikipedia
What is it and how to use it via allrecipes.com
If you don’t have cream of tartar and you’re beating egg whites, you can substitute a little vinegar or lemon juice; it will do the same thing. Thanks for the very detailed explanation!