Today's column answers a question from a reader that I thought others might be interested in too. She was looking through her recipes and was going to bake a product that called for cream of tartar and wondered what role cream of tartar played in the baking and cooking process. She wondered if it was a leavening agent and if it was similar to other leavening agents, like baking soda and baking powder.
The chemical name for cream of tartar is potassium hydrogen tartarate. It's an acid salt and is obtained when tartaric acid is half neutralized with potassium hydroxide, transforming it into a salt. Cream of tartar is most often used as a stabilizer in our baking and cooking processes. It gives more volume to beaten egg whites and it produces a creamier texture in sugary desserts such as candy and frosting because it inhibits the formation of crystals. If you are baking or cooking and don't have cream of tartar, you could substitute white vinegar, however you may not be satisfied with the results, since the substitution of a liquid for a dry ingredient may not work in some recipes.
Cream of tartar is also the acidic ingredient in some brands of baking powder. That leads to another question, is there a difference between baking powder and baking soda? The answer to that is "yes." Baking powder contains sodium bicarbonate, the acidifying agent (cream of tartar) and also a drying agent to keep it from clumping and reacting until you are ready to use it. Baking powder becomes active when moisture is incorporated into it.
Baking soda, on the other hand, is pure sodium bicarbonate. When baking soda is combined with moisture and an acidic ingredient (such as yogurt, chocolate, buttermilk, honey), the resulting chemical reaction produces carbon dioxide, which expands with heat and causes baked goods to rise. The reaction begins immediately upon mixing the ingredients, so you need to bake the product right away, or it will not rise properly.
You can substitute baking powder for baking soda, although you will need more baking powder and it may affect the taste). You can't substitute baking soda when a recipe calls for baking powder, though, because baking soda lacks the acidity. You can make your own baking powder though by combining baking soda and cream of tartar. Mix two parts of cream of tartar with one part of baking soda to make baking powder.
So, there's your food science tidbit for the day! Happy baking! Thank you reader for an interesting question.