alkali [al–kuh-lahy] noun
A substance that neutralizes acidic ingredients. Baking soda, also known as bicarbonate of soda, is the most common alkali we use in the baking kitchen. When combined in a batter, dough or mixture that contains an acid (such as buttermilk, sour cream, natural cocoa, etc.), the alkaline releases carbon dioxide gas and creates bubbles that encourage the mixture to rise. This results in a desirable, light texture in the finished baked good. Without this substance, the baked item would be heavy with a very dense crumb.