Where Local and Global Appetites Collide

Cooking Science: Baking Soda vs. Baking Powder

When Karyn introduced me a couple of weeks ago, Mary asked me about the difference between baking powder and baking soda.  I gave her a nutshell answer, but promised a full posting with some more info and clarification.

What I initially wrote was, “Baking soda is bicarbonate of soda. In the presence of an acid (vinegar, citrus, etc), it releases carbon dioxide gas causing bubbles. These bubbles leaven whatever it is that you’re baking. Baking powder is basically baking soda mixed with an acid in powdered form. When a liquid is added, you get the same reaction and the same leavening.”.

So let’s back things up a bit.  In my last post about beer, we talked about yeast metabolism.  When yeast are given a food source in the presence of oxygen, they produce energy and carbon dioxide gas (CO2).  That carbon dioxide gas being trapped within your dough is what causes bread to rise.

Of course, that process generally takes a couple of hours, so isn’t a good option for everything.  If you’re making batters or cookies, you might not want to wait that long and you might not want the yeastiness of baking bread in your chocolate cake.

Baking soda and baking powder are both chemical leaveners.  They undergo a chemical reaction in the presence of the right ingredients or conditions to produce the same CO2 gas.  And you don’t have to wait for hours…

Baking Soda:
Chemically, baking soda is NaHCO3.  In the presence of an acid, it reacts to produce our carbon dioxide gas and some kind of side product.  In the case of the classic science demo the ‘kitchen volcano’, vinegar (acetic acid) is mixed with baking soda, to produce CO2, liquid water, and sodium acetate* to produce lots of frothy, foamy ‘lava’.   It’s the carbon dioxide gas that causes the bubbles to form.

Common acidic ingredients that will produce this reaction are vinegars, buttermilk, yogurt, sour cream, fruit juices, honey, and molasses.

Baking Powder:
As I mentioned in my short answer, baking powder is a mixture of baking soda and an acid in solid form.  It also has a ‘filler’ component, often cornstarch. When you mix baking powder in the presence of a liquid (or heat, for slow-acting BP), the crystalline acid will dissolve and react with the baking soda, giving you the same reaction as above.  This is great for when you’re making a recipe without an acidic liquid ingredient.

The filler serves two purposes, it provides more volume to the powder so that it’s easier to measure (would you want to try to measure 1/16th tsp?), and keeps things dry inside the container.  Imagine what might happen if there was no filler and it was humid inside your pantry…

The dry acid ingredient can vary based on the kind of baking powder we’re talking about.  There are actually three types of BP: fast-acting, slow-acting, and double acting.
•    Fast-acting begins to react to form CO2 as soon as the liquid is added.
•    Slow-acting only starts to react in the presence of heat, so nothing happens until you pop whatever you’re making into the oven.
•    Double-acting has both types of acids, so you get a hit of reaction upon addition of your liquid ingredient and then another once the temperature starts to rise.  Most likely, the BP in your kitchen is double-acting.

If you’re out of baking powder, you can improvise using the following ratios to make the amount of BP the recipe calls for: 1 part baking soda, 1 part cornstarch, and 2 parts cream of tartar (the acid).  For example, if your recipe calls for 1 t. baking powder, you’d use 1/4t. baking soda, 1/4t. cornstarch, and 1/2t. cream of tartar.

If you’re out of baking soda, go to the store and buy some more baking soda.  Unfortunately, you can’t use BP to replace the soda because of the additional acid that it contains.  Too many acid byproducts can affect taste, texture, and color.

Extra credit:
I don’t know about you, but I couldn’t tell you when I bought the baking powder or soda in my pantry.  Because they rely on a chemical reaction to cause leavening, and chemicals can break down over time, you might want to test them out next time you reach for them (especially if company’s coming).  Here’s how:
•    Baking soda: ¼ t + 2t white vinegar should cause immediate foaming
•    Baking powder: 1t + ½ c hot water should do the same.
If they don’t, or if they’re sort of lethargic about it, you might want to think about replacing them.

Mary (and everyone else!), I hope this was more helpful in answering your question!

*Sodium acetate is edible in the quantities we’re talking about, and is even used as a flavoring agent.  It’s also what’s commonly used in heating pads to give off heat, but that’s another story altogether!

Tucson Food Dude
Tucson Food Dude

  1. Why, then, if they are essentially the same things do some recipes call for both (why not just use the powder and be done with it, especially since as you say most powder is double-acting)? Does that little extra boost from the straight soda in the initial mix really do that much good? Or is this an artifact left over from the days of single-acting powders and we continue to do this out of habit?

  2. Hi Jennifer,

    I had a feeling that someone would ask this pretty quickly! It’s not just habit – the upshot is that there is a finite amount of CO2 that will be produced by baking soda in the presence of X amount of an acid. If that reaction runs its course but you still need more leavening, you add baking powder with your baking soda.

    For example, let’s say you’re making a lemon cake that calls for (and I’m just making this up) 1 t. baking soda and 1T lemon juice. If that reaction doesn’t make enough CO2 to give your cake rise, you’d add baking powder as well. You could just add more lemon juice and/or more baking soda, but that may throw off the texture or consistency of the finished product.

    Does that make sense?

  3. Certainly, I was just curious.

    I’ve also found that a lot of recipes that call for cocoa powder call for both powder and soda. Since the majority of modern cocoa powder is alkalized (neutralizing the acid), is it (again) really necessary to have both in the recipe?

    (Again, just curious… it’s been a while since Bakeshop I and I don’t think we went this in-depth!)

  4. Jennifer, that’s a really good question.

    I’ve been doing some research and am finding a little bit of conflicting information. That means one thing: time for an experiment! I’ll try to find some time this weekend to whip up a couple of brownie batches and I’ll post the results when I’m done.

    I definitely appreciate your curiosity!

  5. Is there a kitchen chemistry test you can use to see which baking product you have in your pantry?

    I bought either baking soda or baking power and the found, one I got home, that the box leaked. So I threw away the box and put all the powder in a jar. And neglected to label the jar. Now I’m trying to determine what I have?

    It reacts with both vinegar and hot water but not room temperature water. Do I have baking soda? Would baking power fail to react with the vinegar?

  6. Hi Ashley,

    First off, if it came in a box it was most likely baking soda. Baking powder usually comes in a can that’s easily resealable to keep moisture out.

    Since baking powder is basically baking soda with an acid and filler (which is usually cornstarch), you have to have a test that will detect either the acid or the filler. Unless you have a pH meter or litmus strips, you may not find it easy to test for the acid. You could, however, mix 1T of the powder with 1T of water, add that to 1C boiling water and give it a chance to thicken. If it thickens, you definitely have baking powder since there’s nothing in the baking soda that would act as a thickening agent (but the cornstarch in the BP would).

    A couple of other indicators: baking soda tends to make large hard lumps and baking powder doesn’t as much. Baking powder looks a little more like talcum powder and baking soda looks a little coarser. Baking soda has a strong salt/metallic taste, and baking powder is a little less pronounced (so without a side-by-side comparison these last two may not do you much good).

    At any rate, I hope that helps. Let me know what you figure out!


  7. I just found this site and the baking powder vs baking soda information has been very helpful. I noted your comment about baking soda being lumpier than baking powder. I have found that to be true but have had an issue with “lumpy” baking powder since I have moved to Ohio.

    I use a baking powder brand regularly found at the grocery store. I typically would measure the baking powder and add to my dry ingredients. Since moving here, I have found that the baking powder does not blend into the ingredients well and I have sour tasting surprises in my biscuits. I have had to meansure the baking powder into a fine mesh strainer and use a spoon to stir the powder through the mesh. I end up with tiny beads of baking powder left. Since using the mest stainer, I have not had surprise beads of baking powder in the biscuits.

    I wonder if you would have any idea why this is ocurring. I have never had this happen before. I have used several new cans of baking powder and continue to have to use the mesh strainer.

    Thank you for any insight you might have.

  8. Dear Food Dude,

    I made a zucchini/pineapple bread and it has a distinct metallic taste. I used 2 tsp baking soda and 1/2 tsp baking powder, according to the recipe. Could this have affected the taste? Thanks!

  9. Foodie Dude, you were the first person I thought of when I realized I was confused about flour. What is the difference between all-purpose flour and bread flour? I can tell a difference and I am thinking it could perhaps be “gluten”, but why would some bread recipes call for adding more gluten and why have I heard that “kneading bread” brings out the gluten if it is already there? Could you perhaps start a separate post on it? Thanks.

  10. “Bread flour” is made from hard wheat and has a higher protein content and is then aged (either naturally or chemically) to strengthen the gluten, making it better for breads than a-p flour which is made to be weaker (either by mixing with soft-wheat flours, using the softer parts of the wheat kernel or skipping the aging steps) so that it can be used for either bread or pastry.

    If you think about gluten as a protein, like say beef, and then think about what happens to beef when you over-work it or over-cook it. You’re not increasing the protein content, but it’s being worked and messed with more and more and it becomes tougher. In bread, the fermentation of the yeast makes the gluten more elastic so when you knead it, you’re working those proteins, strengthening them so they hold the necessary shape and volume but not overworking them to the point of them getting heavy and tough like an overcooked steak.

    Just thought I’d chime in since I had my bakeshop textbooks handy 🙂

  11. Hard wheat vs soft wheat… good to know. I’ve been buying some different flours (semolina, rye, etc) and experimenting. My bread machine has regular vs whole wheat settings and I’ve just been using the whole wheat settings for these different flours. I guess I’ll have to research more to see whether they are hard or soft. Thanks!

  12. Great info! My son is doing a science experiment in which he is taking recipes that call for either baking soda or baking powder and making two batches, one with each. When we made brownies which called for baking powder, we found that the baking powder ones were nicer looking and less gooey than the baking soda ones and the baking soda ones sort of sunk in the middle and seemed a bit burned on the top (they were cooked side by side). When we made oatmeal cookies which called for soda (where’s the acidic ingredient in oatmeal cookies, anyway?), we found that they looked and tasted similar except that the baking soda ones were much browner (in a good way) than the baking powder cookies. When we made a cake which called for baking soda (had buttermilk and sour cream in it), we found that the baking soda cake was about twice as high as the powder, which we expected, but was again, much more nicely browned. We understand why the powder one didn’t rise, but why are the things made with baking soda browning better??

    Thanks!! Sarah

  13. Can you tell me if there is a natural way that tea and coffee are decafinated? (Other than chemically decafinated)

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