To replace 1 teaspoon of baking powder mix 1/2 teaspoon Cream of Tartar to 1/4 teaspoon each of baking soda & corn starch. The potassium salt of tartaric acid is used to stabilize egg whites in baking.
Used for creamier frostings and to make homemade baking powder. Also used as a souring agent, a stabilizer for whipped eggs such as in meringues.
Potassium Bitartrate (E336i) (also known as Potassium Acid Tartrate or Rochelle Salt).