Tartaric acid is a white crystalline organic acid that occurs
naturally in many plants, most notably in grapes. Its salt,
potassium bitartrate, commonly known as cream of tartar, develops
naturally in the process of winemaking. It is commonly mixed with
sodium bicarbonate and is sold as baking powder used as a leavening
agent in food preparation. The acid itself is added to foods as an
antioxidant and to impart its distinctive sour taste.