Demystifying Baking Powder: The Only Guide You Need (Plus How to Test Leavening Agents for Freshness)

Picture this: You’re in baking mode, and you reach into the cabinet for the baking powder – but what’s the difference between this type of leavening and others (like bicarbonate of soda)? And what should you do if it’s past its “best by” date – is it still okay to use?

You're halfway through a recipe when you realize your baking powder is past its expiration date- what to do? Learn how to test it for freshness with our tips:

Baking powder is a chemical leavening agent made of an acid and bicarbonate of soda, aka sodium bicarbonate, or baking soda.

Yikes! Sounds like high school chemistry.

But keep this in mind: cooking is not just an art, but a fascinating science.

Let’s explore leavening agents together, and when the kids ask why the muffins rise, you’ll be glad you persevered.

What’s It All About?

Did you know that when you add baking powder to moist batter or dough, a chemical reaction takes place that neutralizes acid and produces tiny bubbles of carbon dioxide?

This infusion of air is responsible for creating volume, a porous texture, and balanced flavor.

In addition to leavening with powder and soda, we can also use yeast, physical actions like whisking and folding, and steam, to produce air pockets and achieve light, fluffy results.

Three Ways to Raise

The somewhat mysterious leavening ingredient in question comes in three types, and is typically used in alkaline recipes that lack acidic ingredients. Sometimes it’s also used in conjunction with bicarbonate of soda.

Types of leavening to use in baking without yeast |

We’ll talk more about that later. First, let’s look at the big three:

Single-Acting Tartrate

The first contains bicarbonate of soda (aka “bicarb,” a familiar term among those of you living in the UK as well as all fervent Great British Bake-Off fans) and cream of tartar, or the potassium salt of tartaric acid.

I know, that’s a mouthful. Keep this in mind: It reacts once, when it touches liquid.

When using this type, you must act quickly when getting your batter into the oven, or it will not rise successfully.

Single-Acting Monocalcium Phosphate or Sodium Acid Pyrophosphate

The second single-action type is made of bicarbonate of soda and monocalcium phosphate, or MCP.

It also reacts once, upon contact with liquid, forming gas bubbles that expand when heated. Again, bakers need to move quickly.

Double-Acting Sodium Aluminum Phosphate + Monocalcium Phosphate

And finally, there is the double-acting kind. This is the version that’s most commonly used today, and that you’re most likely to find at the grocery store.

It consists of bicarb and two types of acid, sodium aluminum sulfate, or SAS, and monocalcium phosphate, or MCP.

What’s nice about this type is that reactions take place twice – once during prep, when it’s first introduced to liquid, and again in the oven. This allows bakers to work at a more relaxed pace.

It’s practically foolproof!

Argo Baking Powder |

Argo Baking Powder, 12 Ounces

Today’s recipes generally call for double-acting, but some of Grandma’s baked goodies may call for the single-action types we’ve discussed above, or even an antiquated ammonium carbonate variety called “hartshorn.” But, don’t worry, you may use double-acting successfully wherever a recipe calls for baking powder.

And, you’ll have no metallic undertones, and none of the potential risks associated with aluminum consumption, when you buy a product like Argo’s gluten- and aluminum-free baking powder, available on

A Note on Starch

Have you noticed that some baking powder products contain cornstarch? Let’s talk about why.

The reason cornstarch appears on the labels of some types is because it absorbs moisture, and prevents a premature reaction of the bicarbonate of soda and acid components.

It’s not an active ingredient, but it performs an important function.

Yeast, Manipulation, and Steam

And, while baking powder is the norm for cookie doughs, quick bread batters, and the like, it’s yeast that rules when it comes to bread dough.

Yeast comes in granules and cakes, and produces carbon dioxide by fermentation. It’s the secret to high-rising loaves that bake to tender perfection with a gorgeous crumb.

And then there are two agents that involve neither chemicals nor fermentation: manipulation and steam.

Our Gluten-Free Lactose-Free Mandarin Orange Sponge Cake is an example of a recipe that calls for no leavening agents.

Gluten-Free Orange Sponge Cake for Dessert |
Photo by Felicia Lim.

Mandarin Orange Sponge Cake – Get the Recipe Now

But how does it rise?

Egg whites are beaten until they are filled with air, light and fluffy. More air is introduced when the whites are folded gently into the batter, inflating it to voluminous heights.

And, did you know that dumplings achieve their plumpness without any leavening products? They inflate during the cooking process, when steam fills their pores and expands.

Pretty amazing, huh?

Put It to the Test

Leavening is an essential cooking process when it comes to creating light, fluffy batters and doughs.

To prepare your pantry stash so you’re able to tackle any delicious baked recipe that comes your way, it’s a good idea to keep baking powder, bicarbonate of soda, cornstarch, cream of tartar, and granular yeast on hand.

Four types of leavening to use in baking |
Leavening agents produce an infusion of air that increases volume, and improves texture and taste.

Tightly sealed cornstarch lasts indefinitely, but the others will typically have best by or expiration dates on the packaging. Using expired leavening products may be fine, or it may yield disappointing results, like cookies that spread out like pancakes.

But how do you know if you’re about to bake with ingredients that have lost their “oomph?”

You can test them!

Here’s how to test leavening agents for freshness:

Test Your Baking Powder or Bicarbonate of Soda

Add 1/4 teaspoon baking powder to 1 tablespoon of vinegar.

Combine baking powder with vinegar to test it for freshness. |

If it fizzes with gusto, you’re in business. Do the same with baking soda.

Put That Cream of Tartar to the Test

Cream of tartar that is fresh has a light scent and is snowy white. So, if yours is off-color or has absolutely no smell, you probably should to toss it out.

How to Test the Freshness of Yeast

The folks at Red Star recommend testing granular yeast as follows:

Using a 1-cup measuring cup, dissolve 1 teaspoon sugar in 1/2 cup of warm tap water (110-115°F). Add 2 1/4 teaspoons (one envelope) of room temperature granular yeast. Set a timer for 10 minutes.

Learn how to test yeast for freshness, and more about different types of leavening for baking:

By the time the ten minutes is up, the mixture should be bubbly, and should have risen to the 1-cup mark.

To avoid waste, you may use this yeast in your recipe, provided you deduct the cup of liquid used here. Otherwise, you can be confident that another packet from the same batch is fresh and ready to use.

Test active dry yeast with this simple trick |

But what do you do when these leavening agents fail the test?

Creative Substitutions

If your recipe calls for the powder type, and yours just failed the test, don’t panic.

While it would be tempting to just substitute bicarb and call it a day, this is not the best idea.

Remember: A recipe that calls for powder requires not just its base component, bicarbonate of soda, but its acid component, as well. Without this acid, baked goods are going to turn out flatter, denser, and maybe even a little metallic-tasting.

So… why not make your own?

Here’s how to make homemade baking powder:

Simply mix two parts cream of tartar with one part bicarbonate of soda and one part cornstarch.

For example, if your recipe calls for 1/2 teaspoon of powder, use 1/4 teaspoon cream of tartar, 1/8 teaspoon bicarb, and 1/8 teaspoon cornstarch.

Arm & Hammer Baking Soda, 16 oz, 2 pk

At this point, you may be wondering what to do if you have the opposite problem – if you need bicarb but you only have baking powder.

This is tricky, because there’s about 1/4 teaspoon of bicarbonate of soda in 1 teaspoon of baking powder.

So, to get a full teaspoon of bicarbonate of soda, you will need 3 to 4 teaspoons of the acid- and starch-containing alternative. However, too much powder may result in over-inflation and collapse, and/or an off-taste somewhere between metallic and soapy.


It’s better to avoid this substitution, and purchase another box. Home delivery is a simple solution, and these are readily available via Amazon.

What’s that? You have another question?

Oh, of course!

“Can I substitute another leavening agent for yeast?”

Do you know why certain leavening agents are used to make different types of baked goods? We'll teach you this and more! Read our article now:

I really wish you wouldn’t. But if you’re feeling adventurous, opt for the powder.

If you just add bicarbonate of soda, you’ll also have to add an acid, like lemon juice. And then the question is, “How much of each?”

If you add baking powder, at least you have both components of the reaction already there, the bicarbonate of soda and acid. However, the question remains, “How much?”

The truth is, since baking is a science and the chemical reactions involved rely on precise measurements of various ingredients, there simply is no true substitute for yeast in a recipe that calls for it. Though other options will give your batter or dough some leaving power, they just won’t turn out the same.

Sometimes it’s best to wait until you can get what you need!

Those Tiny Bubbles

Thanks for sticking with me to the end. You’ve certainly earned a reward! How about whipping up something tasty and nutritious?

I’m thinking you’ll enjoy a healthy batch of Sue’s Savory Muffins, a treat that calls for both baking powder and soda.

Why both?

That’s a reasonable question. While the oven preheats, let’s talk about it.

Homemade Savory Muffins |
Photo by Lorna Kring.

Sue’s Savory Muffins – Get the Recipe Now

Remember when we started our discussion, and we said that baking powder is used when a recipe calls for no acidic ingredients?

Well, other recipes contain acidic ingredients like brown sugar, citrus, natural cocoa, honey, vinegar, or yogurt. In this muffin recipe, the acid comes from buttermilk and tomato.

So, if there’s already acid in the mix, why don’t we just use a bit of bicarb? Sounds simple enough, and like it might work…

But wait, stop right there! We need more volume.

You see, the bicarbonate of soda neutralizes the acidic ingredients in the mixing bowl, creating those magical gas bubbles, but that’s where its action in the recipe would end. Our cookies would undoubtedly be dense and flat.

When we also add baking powder, two things happen:

First, it contains soda, which means more neutralization of acid, and more gas infusion into the dough in the mixing bowl.

And second, assuming we’re using the double-acting variety, we can look forward to another release of dough-raising gas bubbles in the oven.

Back to the Basics in Baking

There you have it – all you ever wanted to know (and maybe more!) about baking powder and leavening. Enjoy the muffins, and the amazed looks on the kids’ faces when you tell them about the bubbles.

But hold on one second – I just want to mention one more thing before you go:

Are you familiar with self-rising flour? It already contains baking powder, which sounds convenient.

However, in addition to the fact that it may not suit your recipes, it may lose its “oomph” before you use up the full bag of flour. Food for thought.

For even more ideas, see our article, 15 Tips and Tricks to Improve Your Baking Routine. And leave us a message in the comments! We’d love to know what you’re cooking up in your kitchen.

Photos by Nan Schiller, recipe photos by Lorna Kring and Felicia Lim, © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photos via Argo and Arm & Hammer.

About Nan Schiller

Nan Schiller is a writer from southeastern Pennsylvania. When she’s not in the garden, she’s in the kitchen preparing imaginative gluten- and dairy-free meals. With a background in business, writing, editing, and photography, Nan writes humorous and informative articles on gardening, food, parenting, and real estate topics. Having celiac disease has only served to inspire her to continue to explore creative ways to provide her family with nutritious locally-sourced food.

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