Baking powder is a leavening agent used in baking to create airy dough and to improve the texture and flavor of baked goods. Before the invention of baking powder, bakers used baking soda in combination with an acidic ingredient, such as buttermilk, vinegar or lemon juice, to leaven breads and baked goods. In 1843, chemist Alfred J. Bird invented baking powder in an attempt to create leavening to replace yeast in breads to accommodate his wife’s allergies to yeast. Baking powder does not require the addition of acidic ingredients to activate rising.
It's All in the Ingredients
Baking powder consists of sodium bicarbonate, referred to as baking soda, and acidic salts, called carbonic acids, and other inert ingredients, such as cornstarch and calcium carbonate. The inert ingredients, which prevent the baking powder from clumping, absorb moisture to prevent a chemical reaction from occurring during storage. The baking soda and acidic salts are responsible for causing the dough to rise.
When Chemicals React
When the baking soda and acidic salts are combined with a liquid and exposed to heat, a chemical reaction occurs that releases carbon dioxide gas bubbles. These bubbles fill the dough with air and cause it to rise. The number of bubbles that are released depends on the amount of baking soda used in the recipe, which directly relates to how well the dough rises.
Doubling the Action
Double-acting baking powder contains two separate acids responsible for rising. One acid reacts when water or liquid is added to the baking powder and begins to release gas bubbles almost immediately. The second acid does not dissolve until it is exposed to heat. This means your dough gets a second burst of bubbles as it bakes.
Putting It in Practice
As a rule, baked goods require 1 to 1 ¼ teaspoons of baking powder per cup of flour. However, when baked goods contain an acidic ingredient, such as lemon juice, you need to add baking soda with your baking powder to offset the increased acidity in the recipe. Because baking soda is four times as effective as baking powder, use ¼ teaspoon of baking soda to replace 1 teaspoon of baking powder. For example, when altering a recipe and adding lemon juice or buttermilk -- both acidic ingredients -- for the liquid in the recipe, substitute baking soda for half of the baking powder, but don’t forget to follow the ratio of ¼ teaspoon of baking soda for 1 teaspoon of baking powder.