What is Leavening?

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What is leavening? You’ve heard the term but what is it? In this post, I will briefly explain what leavening is and how it works in your recipes.

When cooking a “bread” type of food (basic breads, quick breads, cookies, cakes, pancakes, waffles, etc.) there are three main components. The flour that gives it structure, the liquids that pull it together, and the leavening agents that provide the air.

These are the most common sources of leaven: Yeast, Baking Powder, and Baking Soda.




Yeast is a very small, single-celled fungus. There are several kinds of yeast out there. Fresh yeast which comes in refrigerated blocks (compressed or cake.) Then there is dry yeast. Dry comes as “Active Dry Yeast” and as a “Rapid Rise” or “Instant” dry yeast. Active Dry yeast must be dissolved in water prior to using, and takes longer for your breads to rise. Rapid Rise or Instant Yeast rise much faster (sometimes half that of Active Dry) and can be mixed right in with the rest of the ingredients, without prior dissolving.

When you bake with yeast, you essentially “wake up” the dormant yeast, and create an environment for that yeast to live and grow in. It requires liquid, and warmth and food. When working with yeast, it is important to make sure that your environment is warm, but not hot or cold. Cold yeast will not grow, and a too hot environment will kill the yeast. When you wake up the yeast, it begins to grow. As it grows, it produces gasses, which create the air in your bread.

Some people find yeast to be very intimidating. I think it is simply because it does take a little more work, and people envision all sorts of problems. It does take a little practice to master, and even a seasoned baker sometimes has a “flop” of a batch of bread. It happens to the best. But once you get the hang of it, the possibilities are endless. There is nothing like fresh bread right out of the oven!

Yeast should be kept in a cold, dry, air-tight place. I use the above kind of yeast, but it is a large package. A container of yeast generally does not last a long time after opening, often only two weeks. I have a dark brown yeast jar from some yeast I bought a long time ago. When I open the large pack of yeast, I fill the jar, and then use my vacuum-sealer to seal the back shut again. I store them both in the refrigerator. As I empty the jar, I just re-fill it from the pack, and re-vacuum seal it. This keeps both portions of the yeast fresh, and keeps it from going to waste.

Baking Soda


Baking soda is sodium bicarbonate.

Baking soda works by reacting with the liquids and the acid in a food to create carbon dioxide. Baking soda reacts immediately with these ingredients, and must be baked immediately after mixing. If you let a food sit a while, the reaction will have ended and the bubbles it created may dissipate, leaving you with a very flat bread. This is why pre-heating your oven is very important in baking. The oven should be at the right temperature, waiting for you to put your goods in as soon as they are ready.

Baking Powder


Baking Powder is a combination of baking soda, two acids, and some cornstarch. The cornstarch keeps the acids from reacting to the baking soda in the container. Most baking powder is what is called “Double Acting.” This means that the leaven agent reacts when it hits the liquid, creating air bubbles, and then it reacts again when it is exposed to the heat of cooking. So it “acts” twice.

Many brands of baking powder are out there, and many of them actually contain aluminum. I’m not going to go into a health lesson here, but I don’t find consuming aluminum to be a healthy thing, so I always read the label.

Finally, if you have a recipe that calls for baking powder, and you have run out, here is an easy substitute if you ever find yourself in a pinch.


1 teaspoon of baking powder can be substituted with 1/2 teaspoon baking soda and 1/4 teaspoon cream of tartar.

or 1/2 tsp baking powder = 1/4 tsp baking soda + 1/8 tsp cream of tartar

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