cream of tartar (not tartar sauce

Cream of tartar is potassium bitartrate (potassium hydrogen tartrate), an acidic byproduct of wine fermentation that crystallizes on the interior walls of wine barrels. It is a fine, white crystalline powder with a slightly acidic taste and no discernible odor. The compound forms naturally when tartaric acid, present in grape juice, reacts with potassium ions during the winemaking process. Commercial cream of tartar is harvested, purified, and ground into a uniform powder suitable for culinary applications.

In its pure form, it is essentially flavorless and functions primarily as a chemical leavening agent and stabilizer in cooking and baking.

Cream of tartar serves as an essential ingredient in baking and cooking as a leavening agent, acid regulator, and stabilizer. When combined with baking soda, it produces carbon dioxide gas, creating lift in cakes, cookies, and quick breads—particularly in recipes predating modern double-acting baking powders. It stabilizes egg white foams in meringues, angel food cakes, and soufflés by lowering pH and preventing overbeating. Additionally, it prevents sugar crystallization in frostings, fondants, and fudges; inhibits vegetable discoloration during cooking; and aids in clarifying broth. The ingredient appears in snickerdoodle coatings and is sometimes used in homemade cleaning preparations.