What is a leavener?
Leaveners or leavening agents are substances that are used to make bread and other baked goods -- such as cakes, cookies and muffins -- rise.
Bread rises thanks to yeast, a fungus that ferments when mixed with dough, converting sugar and starch into ethanol and carbon dioxide that allows it to rise. Yeast comes in fresh or dry forms.
Pure sodium bicarbonate, baking soda will not only fluff up your muffins, it can also put out a grease fire, clean your teeth and deodorize your carpet. When you cook with baking soda, you need to balance it out with an acid like lemon juice or buttermilk. Otherwise, your muffins may have a bitter, soapy flavor.
A combination of baking soda and a few other ingredients, most notably cream of tartar, a dry acid, baking powder usually comes in a can. Out of baking powder? Make your own by mixing one part baking soda with two parts cream of tartar.