Baking soda vs. Baking powder

Can you substitute baking soda for baking power? Or maybe the other way around? The simple answer is no, but there is more to that. In this article I will tell you a little more about the science behind baking soda and baking powder, after which I’ll explain the difference and when you can substitute one for the other. Keep reading for a little at home lab experiment.

The Science

Both baking soda and baking powder have been around for a long time. They actually came to the market between 1830- 1850[1] , that’s nearly 200 years ago! You add baking soda and baking powder to batters and doughs to leaven them, which is why both are called “chemical leavening agents”. To explain the chemical reaction we have to start with diving a little bit into the world of acids, alkalines and pH.

The pH is a scale to indicate the acidity of a liquid, which goes from 0 – 14. A sollution with a pH of 7 is referred to as neutral. Everything below a pH of 7 is acidic and above 7 is alkaline. Keep in mind though: the pH does not solely determine whether something tastes sour or not. A few examples of acidic and alkaline foods:

Acidic foods

  • Lemon juice
  • Vinegar
  • Yoghurt
  • Cocoa powder*
  • Honey
  • Cake flour
  • Brown sugar
  • Molasses
  • Buttermilk

Alkaline foods

  • Baking soda
  • Egg whites
  • Dutch cocoa*

*Note: There are different types of cocoa powder. Dutch processed cocoa powder is alkalized. So if your recipe calls for natural cocoa and baking soda, that’s because it relies on those two reacting. If you do use Dutch cocoa it won’t react. So remember: if there is baking soda, use natural cacao powder.

Acidic and alkaline solutions can react with eachother, which is what is essential for baking soda/ baking powder to do their jobs. But what happens? Well, in this case the reaction results in gas bubbles (CO2). Exactly what you need for your fluffy pancakes or a beautifully risen cake. Let’s go into more detail.

Baking soda

Baking soda

I think most people know baking soda from the orange box from Arm & Hammer. Baking soda is actually a mineral and can also be called bicarbonate or sodiumbicarbonate. It has E- number E500 and can be used in all sorts of foods. When dissolved in water it has a pH above 7, which means it is alkaline and it needs an acid to form gas bubbles. So when a recipe calls for baking soda you will often also see the inclusion of something like vinegar, lemon juice, yoghurt or another acidic ingredient.

As soon as baking soda comes into contact with an acidic liquid it reacts very quickly. When it is used in combination with acidic powders, like brown sugar, chocolate or cocoa [2] it reacts slower, because the powders need to dissolve first, before they can react with the baking soda.

Baking powder

Baking powder is actually mix of baking soda and an acid. You will probably also see starch listed in the ingredients. This is added to the mix in order to absorb any moisture from the air and it helps prevent the acid and alkaline to react before you want it too. Besides that it also adds some bulk, in other words: it seems more that it actually is. That might sound a bit scammy, but it actually makes it easier to measure [2]. Imagine needing 1/16th of a teaspoon in a recipe.

The acidic component of the baking powder determines how it fast it will react when it is dissolved. If the acid dissolves quickly, the reaction will take place quickly. If it dissolves slowly, or needs some heat to dissolve (like the heat during baking) the reaction will take place much slower. Baking powder can also contain a “fast acid” AND a “slow acid”, in that case it functions like a two step rocket: you have a first launch of bubbles quite quickly after mixing and a second boost after a while, when it is in the oven.

This second boost is great for when you are baking cakes for example. At the start of the baking process, some components in the cake batter form a network which can trap the bubbles. If you only have a fast reaction, the bubbles will have formed before the network is there to capture them in your cake.

Substituting one for the other

As you might have concluded, you can’t just blindly add baking soda instead of baking powder, but if you know what you are doing you actually might! When making cookies, sometimes you can use baking soda (when it contains an acid ingredient, like honey, cake flour, molasses, corn syrups or ingredients mentioned before) but you can also use baking powder if you don’t have any acidic ingredients.

You have to be mindfull when adding/ substituting baking powder and baking soda, if you add too much or don’t mix it through proppely it can give a bit of an off taste. This is one of the reasons why it’s wise to follow baking recipes, because if you don’t get the science just right, it can impact the end result quite a bit.

Home lab

What better way to understand the science than to see for yourself.

What you need

  • 1 tsp baking soda
  • 1 tsp baking powder
  • 2 tbsp water
  • 1 tbsp vinegar/ lemon juice
  • 3 bowls

How to test it

  1. Divide your baking soda over two bowls and add the baking powder to the third. Keep track of which is which!
  2. Add a tablespoon of water to the baking soda. What happens?
  3. Then add a tablespoon of vinegar to the baking soda. What happens?
  4. Now add a tablespoon of water to the baking powder? What happens?

Let me know what you observed in your home lab and tag me on Instagram if you’ve tried! Ready to try them in a recipe? Make some quick vegan oatmeal raisin cookies. Why would we add baking powder here and not baking soda?

Sources

  • [1] McGee, On Food and Cooking, p. 519
  • [2] McGee, On Food and Cooking, p. 534

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