Cream of Tartar or Food Science 101.
Cream of tartar has come up all week at the store. So I guess it is high time that we talk about it, what it is, and where it comes from. Potassium bitartrate crystallizes in wine barrels during the fermentation of grape juice into wine. In wines bottled before they are fully ripe, the solid cream of tartar will come out of the wine on the side of the bottle in a sort of crust, thus forming what is called “crusted wine”. Cream of tartar occurs when tartaric acid is partly neutralized with potassium hydroxide, transforming it into a salt. Grapes are the most significant natural source of tartaric acid, and cream of tartar is obtained from sediment produced in the process of making wine. It is an acid salt that has a number of uses in cooking. Don’t freak out about the thought of cooking with acid, since lettuce, brown sugar, steak, plums, and just about every other food we eat is acidic. In fact, egg whites, baking soda, and milk are some of the few non-acidic (alkaline) foods we eat.
Cream of tartar is best known for helping stabilize and give more volume to beaten egg whites. It is the acidic ingredient in some brands of baking powder. It is also used to produce a creamier texture in sugary desserts such as candy and frosting. It is used commercially in some soft drinks, candies, bakery products, and gelatin desserts. Cream of tartar can also be used to clean brass and copper cookware.
If you are beating egg whites and don’t have cream of tartar, substituting white vinegar can work (in the same ratio as cream of tartar, generally 1/8 teaspoon per egg white). It is a little more difficult to substitute for cream of tartar in baking. White vinegar or lemon juice, (3 times the amount of cream of tartar called for, will provide the right amount of acid for most recipes). But that amount of liquid will most likely cause other problems in the recipe. Bakers have found that cakes made with vinegar or lemon juice have a more coarse grain and are more prone to shrinking. In the kitchen, cream of tartar is used to stabilize egg whites, increase their heat tolerance and volume, prevent sugar syrups from crystallizing, and reduce discoloration of boiled vegetables. It is frequently combined with baking soda (which needs an acid ingredient to activate it) in creating baking powder. Cream of tartar is commonly used in combination with potassium chloride in sodium-free salt substitutes.
To make your own home made baking powder, mix 1/2 teaspoon cream of tartar and 1/4 teaspoon each baking soda and cornstarch.