Cream of Tartar, which can be used in cinnamon cookies making them softer, in whipped egg whites stabilizing them, or in a simple syrup preventing it from crystallizing, is the perfect ingredient that we must keep in our cupboard. What is it exactly that makes cream of tartar so special? Cream of Tartar is an amazing natural preservative, while it is also used as acidity regulator and flavoring ingredient. In cooking, cream of tartar is used as stabilizer, or in order to prevent syrups from crystallizing, while it also reduces discoloration of boiled vegetables.
Technically, it is an acid, and more specifically, a tartaric acid. It is a byproduct of winemaking, the residue left on the barrels actually. Most commonly, cream of tartar is used as a leavener, because when combined with baking soda, they produce carbon dioxide gas. This is the same gas produced by yeast in bread baking. When added to egg whites, it enhances the strength of the air bubbles and slows down their natural tendency to deflate. And when added to simple syrup, it prevents the sugar’s natural tendency to form crystals.
Cream of tartar can also be mixed with an acidic liquid, such as lemon juice or white vinegar to make a paste (like toothpaste in texture) which is used as a cleaning agent for metals such as brass, aluminum or copper, or with water for other cleaning applications like the removal of light stains from porcelain.
Cream of tartar, when mixed into a paste with hydrogen peroxide, can be used to clean rust from some hand tools, especially hand files. The paste is applied and allowed to set for a few hours. Then it is washed off with a baking soda/water solution. Another rinse with water, a thorough drying and a light application with oil will protect the files from further rusting.