The difference between baking soda and baking powder

The difference between baking soda and baking powder
This is what happens when baking soda and acid (in this case vinegar) interact. Credit: Kate Ter Haar, via Wikimedia Commons.

What's the difference between baking soda and baking powder? Short answer: acid. But it can make a big difference for baked goods, so let's explain.

Baking soda has only one ingredient: . Sodium bicarbonate is a base that reacts when it comes into contact with acids, like buttermilk, yogurt or vinegar. This reaction produces carbon dioxide (CO2) in the form of bubbles, like a liquid foam (think of the grade school experiments involving fake volcanoes, vinegar and ). When making baked goods, the process is called "chemical leavening," because the trapped CO2 gas makes the dough or batter rise.

But when baking soda comes into contact with an acid, it pretty much reacts immediately. And that's a problem.

For many baking recipes, you want an extended reaction, so that the rising doesn't take place all at once.

Baking powder addresses this problem because it is "double acting" – it has different ingredients that create CO2 gas at different stages of the baking process.

All baking powders contain sodium bicarbonate (just like baking soda). But baking powder also contains two acids. One of these acids is called monocalcium phosphate. Monocalcium phosphate doesn't react with the sodium bicarbonate while it's dry. But as soon as the baking powder is stirred into a wet dough or batter, the two ingredients begin to react, releasing bubbles of CO2 and causing chemical leavening.

But to extend the chemical leavening process, baking powder also contains a second acid, either sodium acid pyrophosphate or sodium aluminum sulfate. Neither of these acids react with sodium bicarbonate until they are both: A) wet (i.e., stirred into the batter) and B) hot.

In other words, sodium acid pyrophosphate and sodium aluminum sulfate won't start reacting with the sodium bicarbonate until after you've put the dough or batter in the oven. This means that the batter rises for a longer period of time, making lots of bubbles (and a fluffier cake, muffin, or whatever).

At some point during the baking process, the liquid foam of rising batter becomes a solid foam, because the batter "sets." This is one reason eggs are so common in recipes.

The proteins in eggs become irreversibly denatured when exposed to heat (i.e., the proteins unfold and cannot refold into their original shape). These altered egg proteins essentially give the liquid foam a solid structure, allowing it to hold its shape.

By comparison, in recipes that use yeast as a leavening agent, the gluten proteins in flour serve a role similar to that of egg proteins in most chemically-leavened in the sense that they help to trap air bubbles until the dough sets. (That's why bread flour has more protein than cake flour.)

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User comments

May 22, 2014
I don't understand the point of this article, and it's wrong anyways.

Plain sodium bicarbonate reacts with heat just the same, releasing CO2 and steam when heated above 100 degrees C because it breaks down into sodium carbonate.

Plain soda is used when you don't want the batter to start rising until it's in the oven, whereas baking powder is the one that starts bubbling away immediately when you mix it in the moist dough. When plain soda is used, the batter is usually not acidic enough to cause an immediate reaction, so the article gets it the wrong way around.

You make pretzels and cookies with baking soda, and muffins and pancakes with baking powder, because the slower reaction of the plain soda would leave the muffins flat, and the faster reaction of the baking powder would make your cookies swell up into formless blobs.

May 22, 2014
Furthermore, many brands of baking powder don't necessarily contain any of these fancy acids. Some have just sodium bicarbonate and a bit of powdered citric acid mixed with corn starch.

That's because the point of baking powder is to dissolve lots of CO2 into the liquid, which is then rapidly driven off by the heat in the oven, which causes the swelling of the cake, whereas the plain soda releases much less CO2 and does it slower at a higher temperature, leaving you with a denser foam.

Often the baking powder in receipes can be substituted with carbonated bottled water, or even carbonated mineral water if you don't mind the taste.

May 22, 2014
I don't understand the point of this article,

Obviously it is a wake up call for the need to ban or tax these evil CO2 producing chemicals. Once the climate scientist begin to account for the effects of baking bread and grade school volcanoes into their models it's clear our future will be doomed.

May 22, 2014
I don't understand ... this article.

There, I fixed it for you.

May 24, 2014
I don't understand ... this article.

There, I fixed it for you.

What is there to understand in an article that provides false information?

The article is completely misrepresenting the mechanism of action and use of baking soda and baking powder compared to actual baking. But yes, please try to use baking powder insted of soda to make cookies because you now think it's the slower acting of the two.

What you'll get is cookie dough that balloons up tremendously as you try to work it, and then goes flat and rock hard in the oven because all the sodium bicarbonate has reacted before you put it in the oven.

May 24, 2014
Here is the correct explaination of the difference between baking soda and powder:


Baking powder is available as single-acting baking powder and as double-acting baking powder. Single-acting powders are activated by moisture, so you must bake recipes which include this product immediately after mixing. Double-acting powders react in two phases and can stand for a while before baking. With double-acting powder, some gas is released at room temperature when the powder is added to dough, but the majority of the gas is released after the temperature of the dough increases in the oven.

Plain baking soda when mixed in an acidic dough works the same as single acting baking powder, whereas a double acting baking powder works much the same as plain baking soda in a non-acidic dough.

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