Soda vs Powder…?

I’ve had this conversation so many times before. The differences between baking soda and baking powder, so when this conversation came up in the lab I was super ready for a response… sort of.

I mean baking soda was just sodium bicarbonate and powder had… some sort of acid added to make it bubble without anything else? Wait, so why do some recipes only require baking soda then? And why do we add both to some? Can’t we just use baking powder for all the baking, why not cover all our bases and have it react on its own.

Why did I only use baking soda in my banana bread, but I needed baking powder for some of my cookies. Heck, why did I need baking powder for some cookies but baking powder for other cookies? I was starting to think these recipes I’ve seen are just completely arbitrary and just picked whatever the baker had on hand.

Of course, this called for some research. I realized super quickly that there’s about a million and two sites (100% not an exaggeration, you should trust 100% of the statistics you see online) that will tell you that baking soda is sodium bicarbonate and that baking powder is sodium bicarbonate with cream of tartar (tartaric acid). Then they’ll tell you that baking powder will react on its own once liquid is added and make bubbles and make your stuff puff up.

Well, sure, but that still doesn’t explain when to use what and why we use both. So, I decided to dig deeper.

Acids and Bases

Before we can move on to discussing the details of this, here’s a quick primer on the acids and bases.

The way we measure acids and bases is using a pH scale. It stands for power of Hydrogen, but I won’t go too deep into that. It is a scale from 0-14, with 7 (the middle) being completely neutral. This is based on plain water, water is neutral, pH 7.0. Lower numbers are acidic, high numbers are basic.

phscale

There’s a quick guide to common things that are acidic or basic. But as a very simple and basic rule of thumb, most acidic things taste sour to us, basic things taste bitter to us.

Now if you look, baking soda sits around 8.5, higher than 7, making it a base.

Very basically (pun fully intended), bicarbonate, a base, reacts with an acid and forms CO2, carbon dioxide. This is a gas, and when it tries to escape from liquids into the air, it’ll form bubbles. CO2 is what makes soda pop fizzy, and also what makes your baked good puff up. This is also the reaction with the classic baking soda and vinegar volcanoes.

Image result for bicarbonate reaction

If you look to the very right, the HCO3- is the bicarbonate from baking soda. the H+ is the acid, any acid. If you look to the very left, the carbon dioxide is in gas form, this tries to escape from the liquid and as it does so, it makes little bubbles of gas. Now you’re an expert in chemistry.

 

What about baking?

Baking and cooking is really just chemistry. Lots of delicious chemical reactions go on, and then you have a meal. Yum.

But in terms of baking, which one you use will depend on several things:

  • How much do you want it to rise or fluff up? (Will this be a cookie or cake?)
  • What ingredients are in it (Are those ingredients mostly basic or acidic?)

Easy right? Let’s go back to what’s in baking soda and baking powder:

Baking soda: sodium bicarbonate

Baking powder: sodium bicarbonate, acid, corn starch (to stop the other two from reacting, kinda like the third wheel in the relationship, the really awkward kind)

Baking powder actually comes in two forms, most of the time you see the double acting kind. Which means they have TWO acids instead of one. One of the acids act during room temperature, the second one reacts when it goes into the oven.

How much you want it to rise

So the important thing to keep in mind is, we want to have a balance of acids and bases to get this reaction going. And the total amount of each will dictate how much leavening (puffiness) will happen. You put in more base and acid together, you get more CO2, more bubble, more rising.

Now what happens when the balance is out of whack? If you have more base than acid, then your product will taste bitter. Remember when I said bases taste bitter? Well leftover un-reacted baking soda is really bitter. Same thing goes with the other end, too much acid, then you’ll get leftover un-reacted acid, though this isn’t as bad as the bitter baking soda.

What other ingredients are present?

Different ingredients in the recipe might also be acidic. This would be why you would add baking soda > baking powder, there’s already acids in the ingredients. Some examples of acidic ingredients are: honey, lemon juice, yogurt, buttermilk, and bananas.

In recipes where you don’t have acidic ingredients, you’ll often just use baking powder. In recipes where you want it to rise a ton and there’s some, but not a lot of acidic ingredients, you’ll likely use both. It’s simply that, balance the acid and base and increase/decrease based on how puffy you want the thing.

Conclusions and tl;dr

So there really is a method to this madness that goes into recipe development. Experienced bakers are able to tell what kind of leavening agent to use based on the other ingredients they put in, and how much they want their product to rise. Even then though, they go through many trials to make sure they get everything just right. It takes some time to really understand the ratios and exactly how much you need, and it’ll really change based on what you’re trying to make. If you’re just starting to bake a highly recommend following recipes specifically and make sure you find trusted recipes. (Cookbooks and highly popular blogs are usually the way to go)

If you’re ever missing one or the other, there are ways to substitute other ingredients for it. If you need baking powder but only have baking soda, you can cut down the amount and add some acid (cream of tartar, vinegar, buttermilk, lemon juice, etc.). If you need baking soda but only have baking powder, then just add more baking powder (since baking powder is a combination, there’s less baking soda in it).

 

tl;dr

Baking soda is a base that reacts with acid to make gas bubbles that make baked goods rise. Baking powder is a mix of baking soda, and an acid.

If other ingredients are acidic, people use baking soda. If other ingredients are neutral, people use baking powder. If you need something to really puff up, but there’s only a little bit of acidic ingredients, you use both. (Enough baking soda to neutralize the acid, then extra baking powder)

 

References

pH image: https://www.minichemistry.com/ph-scale-indicators.html

http://sallysbakingaddiction.com/2015/06/11/baking-powder-vs-baking-soda/

https://en.wikipedia.org/wiki/Baking_powder

My chemistry classes

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