Baking powder is baking soda (sodium bicarbonate), corn starch and creme of tartar mixed together. Can anyone tell me what the effect of these different ingredients have (and have on each other) and how they work together to leaven baked goods? Like- why cornstarch? I understand it being used as a thickener and to coat things to keep them from clumping, but how does it help leavening? Or is it just to keep the creme of tartar and baking soda from reacting to each other or mixing unevenly?
Baking powder is like a fast-acting yeast; it is used to infuse air into baking mixtures by way of carbon dioxide bubbles, created by a base reacting to an acid. Baking power is made of three different parts:
- An acid
- A base
- A filler
All three need to be dry powders that can be mixed together, common ingredients are cream of tartar (acid), baking soda (base) and corn starch (filler). The role of the acid and the base are to combine together to produce carbon dioxide bubbles when reacting with water or other liquids. The filler helps keep the baking powder dry, so that it remains free-flowing and so that the base and acid don't get moist and interact in the container.
- This article explains the reaction process in further detail: http://recipes.howstuffworks.com/tools-and-techniques/baking-powder.htm
- This piece provides further insight on different types of baking powder, it's history, substitutes, etc.: http://m.cooksinfo.com/edible.nsf/MobilePages/baking-powder