Soda or Powder?

“2 tsp of baking powder… or was it baking soda??” Have you ever felt confused deciphering between baking soda or baking powder? Many people confuse the two, but have no fear…a science blog is here!

Purpose of them at all…

Why do we use baking soda or powder at all? The answer is in the lift. Most baked goods require some sort of leavening agent to provide a rise. Without this, it would result in dense end products. There are various types of leaveners, which all have their own way of creating CO₂, but ultimately they all produce a gas in some way. The CO₂ then causes the dough or batter to rise, contributing to the desired texture of the baked good.

Baking Soda

Baking soda, also known as sodium bicarbonate has the chemical formula of NaHCO₃. It retains a white colour in a powder form. Baking soda falls between an 8 or 9 on the pH scale, meaning it is a base.

When in contact with acids, a chemical reaction takes pace and CO₂ is released. You may be familiar with the typical volcano science fair experiment, by pouring vinegar (an acid) onto a baking soda filled volcano, a fizzy eruption occurs. The chemical equation for baking soda and vinegar is: NaHCO₃ + HC₂H₃O₂ → NaC₂H₃O₂ + H₂O + CO₂. The final products contain CO₂, hence the fizzing and bubbles. During baking, while the acidic ingredient may differ from vinegar, it will still produce CO₂, providing a lift to the food.

The source of the acid in the recipe determines how quickly the dough or batter should be baked. Common acidic ingredients used to activate baking soda is: buttermilk, lemon juice, sour cream, molasses and honey.

A dry or wet acid is what determines how long a batter can wait until baked. Wet acids (eg, yogurt or lemon juice) require the batter to be baked promptly. This is because the reaction between wet acids and the baking soda occur immediately. Letting batters sit too long will allow the CO₂ to escape, leaving little gas left to leaven. However, dry acids (eg, cream of tarter or cocoa powder) do not react as quickly, thus allowing batters to be kept longer even after the baking soda is combined.

Another note, any leftover unreacted baking soda creates a bitter soapy taste. Therefore, you only want to add enough baking soda to react with the acidic ingredient.

Baking powder

Take caution, baking powder is not the same as baking soda, but it does contain part baking soda. Baking powder consists of baking soda + acid (in powder form). Since it is not a single substance the chemical formula would be NaHCO₃ + acid (such as cream of tarter, or KC₄H₅O₆). Think of baking powder as the whole package. While baking soda activation requires additional acids, baking powder already contains the acid.

The only thing required for baking powder to react is a liquid. However, there are two different kinds of baking powder: single-acting and double acting. The difference between the two is the kind of cream of tarter (also known as tartaric acid). Manufacturers make it so that there is fast and slow acting tartaric acid. Fast reacting means the reaction takes place at room temperature, while slow reacting tartaric acid reacts in higher temperatures.

Single-acting baking powders are fast reacting. Their tartaric acid release CO₂ when at room temperature and in contact with liquid. Therefore, batters must be baked immediately or the CO₂ will lost, hence the name fast reacting.

Double-acting baking powder works in two steps. The first reaction takes place when the ingredients are mixed together (similar to single-acting). However, a second reaction occurs when there is exposure to higher temperatures (such as an oven), and more CO₂ is produced. In the oven, the CO₂ searches for any pre-existing air pockets and then expands, causing the baked good to puff up. This allows for batters to be kept for longer, since there will be more CO₂ released even after the initial mix.

Together

Some recipes call for the use of both baking soda and baking powder. In these cases, the CO₂ created by the baking soda and acid alone is not enough to leaven the batter. Therefore, the addition of baking powder helps to bring that beautiful rise to the baked goods.

Substitutions

It may seem a little hypocritical to write a paragraphs on the difference between baking soda and baking powder to end it off with saying you can simply substitute one for the other. While the two are different, because baking powder does contain baking soda, if you find yourself with only one of the two, all is not lost.

When substituting baking soda for baking powder, use 1 tablespoon of baking soda for 3 tablespoon of baking powder. When substituting baking powder for baking soda, add one third baking soda (33.3%) and two parts cream of tarter (66.6%).

However, remember that substitutions are not perfect, and may still affect the outcome depending on other components of the recipe. Perhaps you will find a breakthrough to a classic and have your own eureka moment!