Some of the most primitive questions in baking revolve around baking powder and baking soda. Are they one and the same thing? When to use baking powder? When to use baking soda? When to use both? Can the baking powder and soda be replaced with each other?

Let's try to understand what each of them does in a recipe and then I will tell you why most baking recipes call for both of these.

But first, we have to know that both baking powder and soda are leavening agents.

What is a leavening agent?

A leavening agent is something that reacts with other ingredients in a batter or dough and produces gas (carbon dioxide) during the mixing and baking process. The gas so produced when escapes from the batter pushes the batter upwards and lifts it along. In short, leavening agents lead to the rising of cakes and other baked goods.

Types of Leavening Agent used in food

1. Yeast - generally used in breads for fermentation.
2. Steam - Used in puffs.
3. Chemicals like Baking Soda and Baking Powder which we will be discussing in this post.

What is Baking Soda?

Baking soda (aka sodium bicarbonate) is an alkaline substance (pH>7) that reacts with acidic elements in a batter to form CO2. This CO2 when escapes through the batter leads to the rising of the cake.

If the baking soda does not get enough acidic elements in the batter it will not react properly and the cake will fall flat. Unreacted baking soda leaves a metallic and soapy taste in the baked goods.

Since the Baking soda reacts immediately to the acidic element, for best results, the cake should be baked immediately once the mixing is done. Otherwise, the peak reaction of baking soda might be missed and proper leavening will not be achieved.

What all acidic ingredients Baking Soda reacts to?

• Buttermilk
• Brown Sugar
• Yogurt
• Natural Cocoa Powder (not dutch process)
• Lemon Juice
• Vinegar
• Cream of Tartar
• Sour Cream
• Molasses
• Honey

What is Baking Powder?

Baking powder is a mixture of baking soda and an acidic element called Cream of Tartar and also cornflour. These are mixed together in the dry state when they will not react together. However, when baking powder comes in contact with any liquid element, both these two react together to produce CO2.

Baking powder also continues to react with heat when the cake is baking in the oven.

Since both alkaline and the acidic element is already present in baking soda, it can be used in recipes where there are no acidic ingredients are used.

Are Baking Soda & Baking Powder Interchangeable?

In one word - No.

While baking powder does contain baking soda, only 1/3 of baking powder is baking soda and the rest is the cream of tartar and cornflour. This means if we replace 1 teaspoon of baking soda with 1 teaspoon of baking powder, in effect, we're using only 1/3 teaspoon baking soda in our batter. Thus would mean that we will not achieve the proper leavening needed.

Using thrice the amount of baking powder would significantly increase the acidic elements in the batter leading to an acidic pungent aftertaste.

Similarly, if we replace 1 teaspoon baking powder with 1 teaspoon baking soda, the leaving agent will be too strong and in the absence of enough acidic agents, this would leave a soapy aftertaste as described above.

Therefore, in most cases (especially if you are just starting out) it is not advisable to interchange the two.

Why do most baking recipes call for both?

Baking soda as we talked about reacts immediately to acidic elements and gives immediate leavening effect. The baking powder keeps reacting with the heat to give a leavening boost while the baked goods are in the oven.

A combination of both these leavening agents gives the best leavening for most cake recipes.

Also when we're making something like Lemon Muffins where the lemony flavor is desirable, if only the baking soda is used, it will react with all the lemon in the batter leaving no flavor in the final baked muffin.

In such cases when the acidic flavor is needed, both baking powder and soda are used to give the necessary leavening while keeping the flavor intact.

My advice would be to stick to the recipe you are following. If it calls for both then use both or go for the one mentioned.

You will be able to decide on your own only when you would have developed a sense of proportions and leavening after you have tried enough.

Different examples of using Baking Soda and Powder in recipes

In our muffin batter recipe, we had used both baking soda(0.25 tsp) and powder(1.5 tsp). We had used buttermilk(milk + lemon) as the acidic agent. Since we wanted to retain a slight lemony flavor we have used less baking soda and more powder.

In the brownie recipe, we had used only baking soda. In the case of brownie, fudginess is more desirable than leavening. Though the baking soda reacts with acidic elements like cocoa powder and brown sugar, it gives a little rise without making it cakey.   

In our chocolate cake recipe, we have used 1 tsp baking soda and 0.5 tsp baking powder. Similar to the muffin recipe, we have used buttermilk in this recipe as well. However, in chocolate cake, we don't need the lemony taste so we're using more baking soda which will react fully with the buttermilk and give the necessary rise. The baking powder in this recipe is just for the additional boost while the cake is baking in the oven.