Techniques
Baking Soda & Baking Powder
Baking soda is a "salt" – the chemical name is sodium bicarbonate.
As such, it has a lot of sodium, about 1200 mg of sodium in a teaspoon of baking
soda.
When baking soda is mixed with an acid (like buttermilk or yogurt) the combination
forms carbon dioxide gas, which is what makes batters and dough rise. The reaction
takes place immediately so the baking soda should be added to the dry ingredients
first and then the liquid ingredients mixed in.
Baking powder is made up of baking soda and cream of tartar. Because baking
soda needs an acid to create the carbon dioxide that helps baked goods rise,
the addition of cream of tartar makes baking powder an easy to use leavening
agent. Single acting baking powder means that the baking powder reacts immediately
when liquid is added. Currently, single acting baking powder is not readily
available in the U.S. Double acting baking powder releases carbon dioxide in
two stages. The first stage occurs after wet ingredients are added and has
a second release when the when the mixture is heated.