Why Does Bread Rise?

Recently I wrote a blog post that answers the question “what is food fermentation?” I learned SO much from that massive guide and loved having a better understanding of the scientific process that is involved with fermenting foods.

Today I am baking bread and attempting my first cinnamon swirl bread, and it got me thinking. I’ve made bread countless times in the past but I don’t think I’ve ever really taken the time to understand why bread rises.

What is happening when I add the yeast and watch my dough ball double in size? How does sugar help the process? Why is it important to let your dough rise before tossing it in the oven?

I. Am. Curious. I want to know the answer to the question why does bread rise? I am certain the more that I understand the science behind bread-making the better baker I will be.

I love learning new things, and I’m taking you with me. Let’s learn together and answer why does bread rise?

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Why Does Bread Rise? (The Short Answer)

Bread rises because of yeast, of course! But what is yeast, and how does it work?

Yeast is actually a…fungus. A living single-celled organism that is hungry. Hungry for sugar.

The yeast eats the sugar found in your bread dough and they “burp” out carbon dioxide. The carbon dioxide reaction is what causes the yeast to become foamy when you add it to warm water and sugar.

Gluten has sort of developed a bad reputation over the past few years because there have been so many people who have been discovered to be gluten-intolerant or who suffer from something called celiac disease. Many people feel that they feel better in general when they avoid food products with gluten in it.

However, for those who are not allergic or sensitive to gluten, it actually plays a really special role in making bread (non-gluten-free bread that is). Gluten is a protein that makes the bread dough elastic and baked bread chewy. It also helps make the bread dough rise by trapping the carbon dioxide expelled by the yeast in little bubbles throughout the dough.

This process is called fermentation! Little did I know that I had been practicing fermentation all these years when making regular yeasty breads.

Where Does Yeast Come From?

Where does yeast come from historically? Well, no one knows for sure. An article in the Atlantic suggests that yeast originated in China. An article in Scientific American said there were traces of yeast in the tomb of an Egyptian ruler named Scorpian. A ruler who was buried over 7,000 years ago. The article said Egypt probably wasn’t the first location of yeast in the world. In fact, the same article states,

Yeasts are naturally found floating in air and on just about every surface on Earth, including every opened cheese in your fridge (upon which they will form small cream-colored colonies if left long enough) and on grape skins. It’s not a long stretch to go from grape juice to wine if said juice is left sitting around for a bit, which is no doubt how the first wine got going.

Scientific American

So how have manufacturers harnessed this yeast into the little packets you pick up at the grocery store?

Well, the yeast is everywhere but manufacturers usually try to maintain some consistency and will do their best to guard their source by keeping it isolated. They make yeast found in jars and packets in the grocery store from previous batches.
Here’s a fun video that talk’s about yeast that I found very informative (and it’s only about 4 minutes long).

What Are the Different Types of Yeast You Can Buy at the Store?

As you walk through your local supermarket you may have noticed that there are different types of yeast available. You may also have noticed that different recipes call for different types of yeast. So what’s the difference?

Here’s a quick rundown to help you with your yeast shopping needs.

Types of Baker’s Yeast

Baker’s yeast is any type of yeast that’s used for — well baking. The most popular types of baker’s yeast are:

• Active dry yeast. Active dry yeast is the most commonly used yeast in bread recipes. While most recipes ask for you to “proof” your yeast by adding it to warm water before incorporating it into the flour, it’s not 100% necessary to do so if your yeast is fresh. If you do add this yeast to warm water beforehand (frankly I do believe it gets the best results this way) make sure the temperature isn’t too hot or too cold. 110 degrees is about the temperature you’re trying to achieve.
• Instant yeast. Instant yeast is very similar to active dry yeast, but it’s usually finer and dissolves more quickly. It will sometimes be called bread machine yeast, and it doesn’t need to be proofed in order to work. It can be added “instantly” to dry ingredients.
• Fast-acting yeast. RapidRise is a particular branded name of yeast from Fleishmann’s and the Red Star equivalent is Quick Rise. Either one is a form of instant yeast that is meant to give one good strong rise as opposed to two rises.
• Fresh yeast or cake yeast. You’ll find this type of yeast in a compressed block. It only lasts a few weeks in the refrigerator and it only makes sense to purchase if you’re going to do a lot of baking. Some bakers say the flavor is better with using this, but it’s not a good option if you’re only going to bake every once in a while.

Brewer’s Yeast

Brewer’s yeast is used to make beer and is a slow-rising yeast. Although it’s not usually marketed as baking yeast, you can use it to make bread. The flavor will be quite different from baker’s yeast and is likely to give your bread a bittery taste.

Nutritional Yeast

Nutritional yeast, sometimes called “Nooch” is a deactivated form of yeast. You won’t be able to make bread rise with this type of yeast because it’s formulated to not rise.

A lot of people eat this because of its health benefits such as vitamins, minerals, and antioxidants. From what I can tell, most of the nutrients in nutritional yeast are added (fortified) rather than found naturally in the yeast, but many people (and particularly vegans) enjoy nutritional yeast because they can flavor foods with it. The flavor it adds is sometimes called “cheesy” and one could use it to substitute parmesan cheese, for example.

The Difference Between Sourdough Yeast and Storebought Yeast

You’ve probably heard of a sourdough starter before. Sourdough bread is made from something people refer to as “wild yeast.”

As we talked about before, yeast exists everywhere in our environment, and people who make sourdough bread have learned to harvest that yeast to make it at home rather than buy it in a store.

In my other post about fermentation, we learned that fermentation is the process in which microorganisms break down carbohydrates and convert them into acid or alcohol. Sourdough bread is made when naturally occurring yeast and bacteria are used to make bread rise.

Here’s a video that describes the science behind why bread rises with sourdough bread.

Many people prefer sourdough starters over storebought yeast because they believe it is a healthier more natural process. Sourdough starters are a bit more involved than storebought yeast, and it does take longer to make bread using this method.

Why Does Bread Dough Need to Rise Twice?

When bread dough grows during its first rise, the yeast does an excellent job of pushing the bread dough outward. You’ll notice it grow and even double in size. During this process, the yeast separates itself from the dough and if the gluten (the elasticity part of the dough) is pressed too far it will become weak and collapse. Think of a baked bread that falls in the middle.

By punching it down the second time, it strengthens the gluten in the dough ball and returns the yeast back to its food source.

When it rises the second time (usually shaped and ready to go into the oven) it’s more prepared to hold up during the baking process.

Why Do You Add Sugar to Bread Recipes?

Sugar can be added to bread to make it sweeter, but it is also often included to help the bread rising process. Bread can rise without adding sugar, but it gives it an extra boost in the process. That’s why you’ll often find recipes that tell you to proof the yeast by adding the yeast to warm sugar water.

Why Do You Knead Dough?

Bakers knead dough to give the dough structure and strength and to increase the gluten in the bread. Max Bernstein from Serious Eats writes, “The purpose of kneading any dough is to develop gluten, and incorporate micro bubbles into the mass of the dough which will inflate during proofing and baking. The more a dough is kneaded, the tighter and more regular a baked loaf’s crumb will become. Sandwich breads are kneaded more.”

It’s an important part of helping bread rise because it well-developed gluten does a better job holding on to the carbon dioxide bubbles released from the yeast.

What is the Best Location to let Bread Rise?

Bread dough rises best when it has the right temperature. When the temperature is too low, your dough won’t rise. That’s why you can put it in the refrigerator to slow down the rising process.

If the temperature is too high the bread will rise quickly or even begin baking. The flavor is developed through the rising process, so you want to find a location that is warm enough to rise but not so warm that it rises very quickly or begins to bake.

The ideal temperature is between 75 and 78 degrees. You can achieve this temperature best by:

• Turning on the oven for a few minutes and then turning it off. Once the oven reaches the right temperature, place the bread dough in the oven and let it rise.
• Boiling water in the microwave and then waiting 30-45 minutes until the temperature has become low enough. Put bread dough in the microwave for a warm humid environment.
• Placing the bread dough on top of the refrigerator where heat rises and where the appliance creates heat.
• Placing it on a heating pad set to the correct temperature.
• Placing it close to another heat source like a radiator.
• I’ve also seen people suggest putting it in a warm car, but I have trouble imagining this going well in my family.

Personally, I usually just let my dough rise on my counter and I haven’t had trouble with that. If your house is kept cool you may have more trouble getting your bread to rise and the above options may be more necessary.

Now You Know the Answer: Why Does Bread Rise?

We finally answered the question “why does bread rise?”, but now it’s time to put that information to good use. Making bread is not a hard process, and it’s rewarding and delicious! You can use my bread recipe to get you started if you don’t know where to begin.

Did we answer all your questions? Do you feel like you understand why bread rises better now?

Do you love baking bread? We’d love to hear from you in the comments below!