When you think about bread, what do you imagine? Soft, fluffy slices that go perfectly with peanut butter and jelly? Warm dinner rolls slathered in butter? A fungus fermenting and producing gas and other by-products?
While the first two suggestions may come to mind, it’s unlikely that many people think of a fungus when they hear the word “bread.” However, without millions and millions of fungi, bakers would not be able to create the delicious breads we enjoy.
Yes, it’s true! If you have ever baked bread at home, you know that patience is required. After mixing all the ingredients together, you must wait for the dough to rise before baking it into delicious bread. But why do you have to wait? What causes the bread dough to expand and rise?
The answers to these questions all revolve around one important ingredient: yeast. You have probably heard of yeast, but may not know exactly what it is. If you have baked bread at home before, you likely know that yeast often comes in small packets available at the grocery store.
Those little packets are filled with billions of single-celled fungi known as Saccharomyces Cerevisiae, or “sugar-eating fungus.” That’s right! One of the key ingredients in most types of bread is a fungus!
Before you say “Ewww!” though, remember that fungi can be very beneficial as well as tasty. The mushrooms on your pizza? Those are fungi! Additionally, certain molds are used to ripen some of your favorite cheeses.
The yeast cells in those packets from the grocery store are living organisms. When packaged, they are in a dormant state, meaning they are inactive. However, when added to warm water, they become alive!
In bread dough, the yeast cells mix with warm water and begin to consume sugars, such as sucrose, fructose, glucose, or maltose, which come from the sugar and flour in the dough. As the yeast cells feed on sugars, they undergo a chemical process called fermentation, producing carbon dioxide gas and ethyl alcohol.
The carbon dioxide gas released during fermentation becomes trapped in the sticky, elastic dough, causing it to expand or rise. This process takes time, which is why patience is necessary when baking bread! Additionally, the ethyl alcohol produced gives the bread its distinct smell and taste.
Heat can accelerate the fermentation process, which is why bread continues to rise in the first few minutes of baking in the oven. However, once the bread becomes too hot, the yeast cells die. The pockets of carbon dioxide gas left behind create small holes throughout the bread, giving it its unique texture and softness.
Give It a Try
Interested in learning more about the science behind puffy pastries? Grab some friends or family members and gain hands-on experience by trying out the following activities. If you have never cooked before, some of these activities may be challenging, but we believe in your ability to succeed!
If you have a balloon, a small plastic bottle, some warm water, a bit of sugar, and a packet of yeast, you can conduct a simple experiment at home to observe the activity of yeast. Just follow the instructions at “Blow Up a Balloon with Yeast”. If you have time, you can also try altering some of the variables to see how they affect the results. For example, what happens when you use more or less yeast? More or less sugar? Hotter or colder water?
You can determine whether yeast is truly alive by following the easy instructions for the “Yeast experiment”. All you need is some dry yeast, warm water, sugar, and a mixing bowl. Make sure to write a journal entry about your observations during the experiment. What do you observe? What conclusions can you draw from your findings?
If you’re ready to try your hand at making bread, you can follow the directions for “Making Bread #2”. Besides enjoying a delicious treat, you’ll also be able to draw conclusions about the impact of sugar in bread recipes. When you make the two loaves of bread according to the given instructions, only one will contain sugar. Compare the two loaves and answer the questions provided on the website. What conclusions can you draw? Do you prefer bread made with or without sugar? Why? Don’t forget to share your findings with your family and friends.
Here are some sources to learn more about yeast:
– http://redstaryeast.com/science-yeast/information-for-students/
– http://www.stufftoblowyourmind.com/blogs/yeast-bread.htm
– http://scienceforkids.kidipede.com/biology/cells/doing/yeast.htm
FAQ
1. Why does dough puff up when you bake it?
When you bake dough, it puffs up due to the action of leavening agents such as yeast or baking powder. These agents release carbon dioxide gas as they react with the dough’s ingredients. The gas gets trapped within the dough’s structure, causing it to expand and rise. As the dough bakes, the heat makes the gas expand further, leading to even more puffing up. The proteins in the dough also coagulate and set during baking, providing structure and stability to the puffed-up shape. This process results in light, airy bread or pastries with a fluffy texture.
2. What happens if you don’t use leavening agents in dough?
If you don’t use leavening agents in dough, it will not puff up during baking. Without the release of carbon dioxide gas, the dough will remain dense and flat. The absence of leavening agents means that the dough’s structure will not expand, resulting in a denser and heavier final product. This is often the case with unleavened bread, such as flatbreads like tortillas or chapatis. These breads are made without yeast or baking powder, and instead rely on other ingredients or techniques to provide texture and flavor.
3. Can you use alternatives to yeast or baking powder for dough to puff up?
Yes, there are alternative ingredients or techniques that can be used to make dough puff up without using yeast or baking powder. One example is using beaten eggs in the dough, which can provide some leavening effect. The proteins in the eggs can trap air bubbles, causing the dough to rise. Another option is using steam during the baking process. As the dough bakes, the steam generated from the moisture within the dough can create pockets of air, resulting in puffing up. However, these alternatives may not provide the same level of puffiness and texture as yeast or baking powder.
4. Does the type of flour used affect how dough puffs up?
Yes, the type of flour used can affect how dough puffs up. Different flours have varying protein contents, and proteins play a crucial role in creating the structure of dough. Flours with higher protein contents, such as bread flour, can create a stronger gluten network when combined with liquid and kneaded. This network can better trap and hold the carbon dioxide gas released by leavening agents, resulting in more puffing up. On the other hand, flours with lower protein contents, like cake flour, may produce a softer and less puffed-up texture in the final product.
5. Does the temperature of the oven affect how dough puffs up?
Yes, the temperature of the oven can affect how dough puffs up. A higher oven temperature can cause the dough to rise and puff up more quickly. The heat causes the leavening agents to release carbon dioxide gas at a faster rate, resulting in rapid expansion of the dough’s structure. However, if the oven temperature is too high, the dough may puff up too quickly and then collapse, leading to a dense and deflated final product. It is important to follow the recommended oven temperature specified in the recipe to achieve the desired puffiness and texture.
6. Can the amount of kneading affect how dough puffs up?
Yes, the amount of kneading can affect how dough puffs up. Kneading helps to develop the gluten in the dough, which is responsible for creating a strong and elastic structure. Properly developed gluten can better trap and hold carbon dioxide gas, resulting in more puffing up during baking. Over-kneading, on the other hand, can lead to excessive gluten development, causing the dough to become too dense and inhibiting proper puffing up. It is important to follow the kneading instructions in the recipe and stop once the dough has reached the desired texture and elasticity.
Leave a Reply