Baking soda (sodium bicarbonate) needs to be activated by a sufficient amount of acid in a recipe so that carbon dioxide gas is released. These bubbles of gas are what actually causes the leavening reaction of baking soda, as the gas pushes against the batter or dough, making it expand while it bakes.
The old-fashioned way of working with baking soda is to buttermilk, sour cream, or yogurt, all of which contain acid, to neutralize the alkaline of the soda and cause the reaction. It normally takes about one cup of buttermilk for one teaspoon of baking soda. Other acid containing ingredients can help, such as lemon or other citrus juice; or even molasses, chocolate, or honey. But there is normally an insufficient amount of them to do the job.
Baking powder is a mixture of baking soda and various other dry ingredients, like cream of tartar (tartaric acid), calcium sulfate, monocalcium phosphate, sodium acid pyrophosphate, or sodium aluminum sulfate, that take the place of buttermilk or other acidic ingredients in a recipe.
Some of these acid ingredients react to liquid and others to heat, and most modern commercial baking powders contain a combination of both. This combination makes them double acting baking powders.
When liquid ingredients are mixed with the baking powder, some of the acids will be activated by the liquid and cause a reaction with the baking soda, releasing carbon dioxide bubbles even before you begin baking. This is why you might notice bubbles rising to the top of your pancake batter after you mix it. Other acid ingredients do not react right away, but are held in reserve until the batter reaches a certain temperature, usually 140° F, at which time they begin reacting to release more gas. This second reaction, which is at the later stages, produces an even taller and lighter product.
You can make your own homemade baking powder mixture, but it will be single acting. This means that the reaction will begin taking place immediately when the wet ingredients are introduced, with no second stage later on the baking process. This will not produce baked goods that are as light and fluffy as commercial baking powders, but will still perform fairly well. No commercial single action baking powders are sold today.
Since the baking powder you make will be single action, it is only useful in recipes that are going to be baked immediately. You cannot let the batter sit for a long time or the reaction will finish and the gas will not remain trapped in the batter, meaning your cake or other baked product will fail to rise. Items that will be cooked quickly, like pancakes, are the best use for your single action baking powder. The reaction might happen too quickly for many baked goods. Also, the best use for your homemade baking powder is in recipes that call for baking powder and when it is not possible to use baking soda, instead. For instance, rather than using a homemade baking powder for pancakes and biscuits, you might want to bake buttermilk pancakes or biscuits, along with baking soda. The acid in the buttermilk will activate the baking soda, so you do not need baking powder. Remember that any time you replace regular milk with buttermilk in a recipe that calls for baking powder, you will need to replace some or all of the baking powder with baking soda, or else the alkaline and acid ingredients will not be in the proper proportions. Basically, you are adding acid, so you need to add baking soda. If buttermilk or another acidic liquid is the only liquid used, then baking soda alone should suffice, but go by your recipes instructions, when substitutes are provided. The advantage of baking powder, whether homemade or not, is that it can be stored for a very long time in a dry cabinet.
Homemade Baking Powder
Homemade baking powder is made by mixing cream of tartar, baking soda, and cornstarch in a 2:1:1 ratio. This means there are two parts of cream of tartar of one part each of baking soda and cornstarch. If you are going to make a small amount of baking powder and use all of it immediately, you can leave out the corn starch. Examples follow:
- 1 tsp baking powder: 1/2 tsp cream of tartar, 1/4 tsp baking soda, 1/4 tsp cornstarch
- 2 tsp baking powder: 1 tsp cream of tartar, 1/2 tsp baking soda, 1/2 tsp cornstarch
- 4 tsp baking powder: 2 tsp cream of tartar, 1 tsp baking soda, 1 tsp cornstarch
- 2 tsb baking powder: 1 tsb cream of tartar, 1 1/2 tsp baking soda, 1 1/2 tsp cornstarch
- 8 tsp baking powder: 4 tsp cream of tartar, 2 tsp baking soda, 2 tsp cornstarch
Gluten Free Homemade Baking Powder?
Due to the self-diagnosed gluten sensitivity epidemic, many people seem to be searching for “gluten free baking powder without cornstarch.” The above recipe for homemade baking powder is gluten free because cornstarch is gluten free, not to mention the other ingredients.
Usually, a starch is used in baking powder products to absorb moisture and stabilize the mixture. This is done to keep the acids and baking soda from reacting with each other prematurely. The reason for this is that it is not only liquid in your recipe that can cause a reaction between the baking soda and the acids, but moisture in the air, being absorbed into the powder, can cause them to start reacting. A starch serves to both mechanically separate the ingredients from each other, at least somewhat, and to absorb this moisture and help keep it from affecting the active ingredients. Sometimes, as well, other ingredients may be used to coat the starch granules and help keep them free-flowing.
It would seem that starch has no real active role in baking powder chemistry, but keep in mind, though, if you leave the corn starch out, your baking powder will be a stronger strength as the corn starch is “diluting” the ingredients a bit. Therefore, we include the standard recipe for baking powder rather than have the confusing mess of different recipes.
Most commercial baking powders also use corn starch as the starch. Therefore they are gluten free, as well. Sometimes another starch might be used, such as one derived from wheat but this is unusual. In the US, 95% of “starch” is made from corn. Check ingredient listing to be sure.