In 2020, we have witnessed a sudden growth of home bakers. Banana bread, burnt cheesecake (intentionally or not), sourdough bread, you name it, they’ve done it. While we all know the reason behind the rise in the number of home bakers, we might not know the reason behind the rise in their bakes. And yes! You guessed it! We will be making the oh-so-fun baking activity oh-so-boring by talking about the chemistry behind the 2 common baking ingredients — baking soda, also known as bicarbonate of soda, and baking powder. Yay! Who knows, you might be able to trade this knowledge with your neighbour home baker in exchange for a lil’ treat because who wouldn’t want to know more about the chemistry of the ingredients, especially when they can just follow the recipe and be able to bake a scrumptious dessert even without knowing the science behind it.
Now, let’s roll.
Baking Soda
Starting with the simpler ingredient of the two, baking soda, also commonly referred to as bicarbonate of soda. Baking soda contains only one compound, sodium bicarbonate.
Sodium bicarbonate is a base. Without looking at the next line, can you guess what reaction it could possibly undergo? If reaction with acid is one of your answer, you’re a smart cookie! 🙂 Yes, sodium bicarbonate can react with acid in the presence of moisture (do you know why moisture is necessary?). Now can you deduce what might be the products of this reaction? (the answer will be revealed later in this post)
Clue #1: It is something you have learned in the acids and bases topic.
Clue #2: One of the products helps the baking to rise!
Baking Powder
Like baking soda, baking powder also contains sodium bicarbonate. That and the fact that baking powder is also a rising agent as a baking ingredient is where their similarities ends. On top of sodium bicarbonate, baking powder also contain an acid (commonly cream of tartar) and cornstarch. The addition of these 2 substances make the action of the baking powder slightly different from the soda.
Cream of tartar is an acidic compound. As such, unlike baking soda, baking powder does not require any acidic ingredient in the recipe for it to undergo a reaction. However, there is still one more component required for baking powder and cream of tartar to react. Can you deduce what it is? (Psst, it was mentioned earlier when we were talking about baking soda.) If your answer is water/moisture, you just earned some brownie points! This brings us to the purpose of having cornstarch in baking powder, which is to help keep away any moisture so as to prevent a reaction between the sodium bicarbonate and acid from starting before the baking even begins! That also explains why recipes always calls for the dry ingredients and wet ingredients to be mixed separately first before combining them right before baking! Just like how you combine logic and chemistry knowledge. 😉
Now back to the reaction that sodium bicarbonate can undergo. Sodium bicarbonate reacts with acid to produce water, carbon dioxide and sodium ion. Does the reaction ring a bell yet?
The carbon dioxide produced is what cause the dough/batter/mixture to rise during baking!
So da soda or da powder?
So now that we know what baking soda and baking powder are, do you think it is possible to substitute one for the other in a recipe? Would you know what situations calls for which rising agent?
Since baking soda does not contain acid, it is often used in recipes that contain an acidic ingredient such as buttermilk, yogurt, chocolate, honey, citrus juice, brown sugar, sour cream etc. This allows the baking soda to react with the acid to produce carbon dioxide needed for the rise.
On the other hand, baking powder needs only moisture, which is provided by the wet ingredients and it will be able to do its job is lifting the dough/batter/mixture. As such, baking powder is often used in recipes that do not contain any acidic ingredients so that carbon dioxide can be produced even without any acidic ingredient added.
If you are wondering, why do some recipes call for both baking powder and baking soda, you are 1) a seasoned baker and 2) asking the right question!! In such recipes, baking powder is used for its reliability in ensuring that there will be a rise as you can be sure that the amount of sodium bicarbonate and acid in the baking powder will be sufficient to cause a reaction. The addition of baking soda alongside baking powder, is to react with any acidic ingredients added. Also, since the same measurement of baking soda and baking powder gives a higher concentration of sodium bicarbonate in baking soda, the action of baking soda is also much greater than baking powder. This means that adding baking soda alongside baking powder allows the reduction of baking powder needed to create a greater rise. This is important since too much rising agent will result in a metallic taste in the baked goods 🙁
Now, with this chemistry knowledge about baking soda and baking powder, all you need to be the next home baker is still the same as before you read this post! But maybe the chem is less cheem now 🙂
