Have you ever wondered about the difference between baking soda and baking powder? They seem almost the same, yet recipes call for one or the other—and sometimes a combination. So if you do any sort of baking, you need to have both. But why?
How they’re similar
In one sense, they’re similar—they’re both leavening agents. That is, they’re used to create leavening, or lift, in baked goods, making them lighter and airier. Much like yeast does in bread.
And they both do it in the same way—through a chemical reaction that produces carbon dioxide, a gas. When those gassy bubbles get into the oven, they expand, causing your cakes, cookies, and quickbreads—these glorious Morning Glory Muffins, for example—to rise.
They aren’t kidding when they say baking is chemistry!
(What else makes for lift in baked goods? Egg whites, for one. Beaten stiff and full of air that expands when it gets into the oven, egg whites create puffy souffles and angel food cakes.)
How they’re different
Baking soda, aka sodium bicarbonate, is an alkaline powder. When it comes into contact with an acid, the result is the reaction that produces the carbon dioxide.
Since baking soda needs acid to do its job, recipes using only baking soda will also include acidic ingredients like buttermilk, yogurt, or lemon juice. (Other baking ingredients are acidic too, like brown sugar, but typically not acidic enough to allow a recipe to use baking soda alone.)
But what if there’s no buttermilk, yogurt, or lemon juice in your recipe?
Enter baking powder, which is baking soda plus the acid it needs for a reaction, typically cream of tartar. The reaction happens when baking powder comes into contact with liquid, again producing carbon dioxide.
(If baking powder is baking soda + cream of tartar, does that mean you can make your own? Yes it does. Here’s how—but note this will be single-acting baking powder. What’s single acting backing powder? Read on.)
Why do some recipes have both?
Some recipes might have acid, but not enough to provide all the lift that you need or want. So there’s some baking soda that gets activated by that acid, but also some baking powder to make for even more of a reaction.
What’s the deal with double-acting baking powder?
Double-acting means that the baking powder is formulated such that it’ll have two reactions—one when combined with a liquid, aka you combine your wet ingredients with your dry ones, and then another reaction to heat, aka when you put your muffins in the oven.
There is such thing as single-acting baking powder, but you’re unlikely to find it at the supermarket. Should you run into it or decide to make your own baking powder, note that since the only reaction that happens is when the wets meet the drys, you want to get your batter into the oven relatively quickly before the gas bubbles deflate. Don’t stress about it—just be ready to put the batter in the pan and bake once you’ve combined all your ingredients.
Baking soda by its very nature is single-acting, so batters using soda, especially only soda, should also get into the oven without a lot of dilly-dallying.
How to tell if they’re fresh
Baking soda and baking powder can lose their efficacy—in other words, expire. If you suspect yours might have been sitting in the cupboard for too long, here’s how to check.
To test baking soda, because it’s activated by acid, just mix it with vinegar or lemon juice and see if it produces gas—in other words, fizzes. Half a teaspoon of soda to a tablespoon or so of vinegar or lemon juice will do the trick.
Because baking powder is activated it by liquid, just mix it with water to see if it fizzes—equal parts powder and hot water.
How to use them, or a little further down the rabbit hole for the chemistry and/or baking nerds
As a general rule of thumb, it takes 1/4 teaspoon of baking soda or 1 whole teaspoon of baking powder to leaven 1 cup of flour. Why different proportions? Because baking soda is pure sodium bicarbonate while baking powder is sodium bicarbonate plus other ingredients. In other words, by volume baking soda is much stronger.
So a cake recipe that has 2 cups of flour might have 1/2 teaspoon of baking soda if its liquid is buttermilk. And it might have 2 teaspoons of baking powder if its liquid is milk.
Does that mean you can substitute milk for the buttermilk and use 2 teaspoons of baking powder instead of 1/2 teaspoon of baking soda? Technically yes, and that’d be a place to start. But only a place to start because, well, baking. It’s chemistry and changing one factor can affect others.
You’ll also notice that quite often the 1/4 teaspoon baking soda:1 teaspoon baking powder:1 cup flour rule goes out the window. It could be because there are other goodies in the batter, like fruit or nuts—my Morning Glory Muffins have tons of both—so the recipe needs more leavening to get that heavy batter to rise. And that’s just one of the many reasons the proportions could be purposefully increased.
On the other hand, sometimes increased leavening can be the reason your muffins don’t rise. Too much can cause air bubbles that get too big, float to the top, and pop. And there goes your lift. (Thank you for teaching me that, Shirley Corriher.)
Too much baking soda can also leave un-reacted-to, in other words un-neutralized, soda in your baked goods. Which can give them a metallic and/or soapy taste.
Baking!
Further still for the even nerdier
Say you come across a recipe that includes buttermilk, yogurt, lemon juice, or something else acidic but it uses only baking powder, no baking soda. In other words, the recipe is acidic, but it’s not using the leavener that’s activated by those acids. Why would that be?
Think about it. If the recipe used baking soda, the acidic ingredient’s acid would be neutralized, or at least somewhat neutralized, by the chemical reaction that makes the carbon dioxide. But baking powder doesn’t need that acid to make carbon dioxide—it has its own. So with baking powder, the acid of the acidic ingredient stays intact, resulting in a more acidic final product. The recipe developer wanted those pancakes or muffins to be a little tangy!
(Or they didn’t know what they were doing and the recipe tasted good so—amen.)
There are other reasons to use baking soda and baking powder in seemingly illogical ways and proportions. One example—baking soda helps promote browning. So if you’re looking for more of that, you might want to increase the proportion of soda to powder in your recipe.
Baking soda can also delay the time it takes for a batter to set. So if you want less spread in your cookies, for example, you might want to decrease the proportion of soda to powder in your recipe so they’ll set sooner.
It’s a deep rabbit hole!
The bottom line
Long story not very short, baking soda and baking powder are both leavening agents—they help make your baked goods rise and become light and airy. The difference between them is in what triggers that leavening—with baking soda, it’s acid. With baking powder, no acid is needed. Which is why sometimes a recipe uses one, sometimes the other, and sometimes both.
How they’re finessed, in combination with the rest of the ingredients in a recipe, can make a difference, sometimes a big one, in the resulting cake, cookie, or muffin.
Unless you know what you’re doing and/or don’t mind an experiment or twelve that doesn’t turn out well, when it comes to baking, follow the recipe.
Because—baking!
Recipes for appreciating baking soda and baking powder:
Morning Glory Muffins
Strawberry Rosemary Muffins
Chocolate Muffins
Banana Walnut Muffins
Rustic Gruyere Chive Scones
Ginger Orange Scones
Maple Oat Pecan Scones
Raspberry Vanilla Bean Scones
The World’s Best Chocolate Chip Cookies
Lavender Butter Cookies
Lemon Poppyseed Butter Cookies
Salted Cherry Almond Oatmeal Cookies
Mexican Chocolate and Cherry Brownies
Easy Orange Marmalade Bars
Lemon Bars with Cardamom
Nana’s Honey Cake
Buttery, Sweet, Bright, Thoroughly Delicious Plum Cake
