A white, powdered substance, also referred to as potassium salt, that is the residue (by-product) from the tartaric acid remaining in wine casks after the fermented grapes have been removed. Cream of tartar is a key ingredient added to baking soda in order to produce baking powder. It is also often added to egg whites to stabilize the whites as they are beaten and then folded into cake batters or for use in preparing meringues, souffles or angel food cakes. Similarly, cream of tartar is useful in the preparation of sugar syrups for making candies to prevent them from crystallizing. It may also be used as a whitener to enhance the white colors of foods such as boiled potatoes, cauliflower or white cakes.