What Makes Bread Rise?

I don't know if your mind does this, but mine occasionally locks onto something and simply won't let go until it has its answers. This happened to me one day as I was standing in the warm aromatic store front of my favorite bakery. One moment I was devouring a sumptuous selection of pastries, cookies, cakes and loaves with my eyes closed when my mind suddenly seized upon the wonder of yeast and other leavening agents.

What causes rising?

Now, I imagine that most of you, unless you have a culinary school education, are thinking that yeast or baking soda are what makes baked goods rise. In a way, this is indeed the truth. One or more of these agents are needed for baked goods to rise. However, it is the leavening itself or the air, steam or carbon dioxide that causes baked goods to rise. It is the job of certain ingredients or processes which put these bubbles of gasses into our baking. Since yeast is the primary leavening agent used in bread-making, let’s focus on that first.

What is yeast?

Hold onto your seats and please don't over-react. Yeast is, in fact, a single cell fungus. I know, I know! For all of our distaste at finding mold on bread and our tendency to immediately toss it in the composter, we find that a fungus is what makes bread what it is in the first place.

How does yeast work?

When you mix bread dough, an enzyme in the yeast causes the starch in the flour to break down into a simple sugar. The yeast feeds on the sugar in the dough and excretes carbon dioxide and ethyl alcohol, which is contained in pockets of air in the dough and causes the dough to puff or "rise." In this day and age of educated consumers, it does not require chef's school to be familiar with gluten. Knowing what causes it and exactly what it does is a bit different, however. When flour and water is combined, glutenin and gliadin (proteins in flour) mix with the water and make the strong elastic substance that we call gluten. Gluten's purpose in bread-making is to provide a strong, expandable casing for the carbon and alcohol produced by the yeast's consumption of the sugars. If the dough is not high in gluten, it will not be strong enough to hold onto the gasses and the bread will not rise properly.

Does yeast do anything else?

As we mentioned before, when yeast consumes sugars it exhumes carbon dioxide and ethyl alcohol. It is the production of alcohol that we refer to when we speak of fermentation. Fermentation benefits bread in that it increases the flavor. When larger, more complex molecules are broken down into their more simple forms, they become more flavorful. For example, when flour is broken down into starches and the starches are broken down into sugars, they become tastier. The alcohol is what aids the larger molecules to break down. The longer a substance has to ferment, the more flavorful it becomes. When dealing with the fermentation of bread, the heat that is typically the environment it is worked on inhibits some of the flavor building processes. All of you without culinary school experience may need to hold onto your tummies again Bacteria are the source of a large amount of the flavor our food has. Yes, I know that bacteria can be dangerous but it can also be beneficial and helpful as well. When yeast is highly active, it is voracious and eats the sugars in the dough as fast as they are produced. Bacteria also like to consume and thrive on sugars as well. How do we allow beneficial bacteria to grow? Well, yeast, unlike bacteria, slows down in cooler temperatures as long as fermentation in refrigerated conditions can allow the "seasoning" bacteria to flourish. This is the process which gives us such delicious varieties such as sourdough bread.

Other leavening agents...

Now that we have looked closely at how and why yeast does what it does so well, perhaps you are wondering about other methods of leavening. I know that I remained curious about what causes cookies and cakes to rise, even cakes such as angel food. Chef's school graduates will know instantly that angel food cake has no baking powder or soda. So, how does this rising occur? It is in the beating of the batter that air is infused into the mix. During baking, when the trapped air expands, the cake rises. Cooked batter, containing a high concentration of flour which is very strong, is strong enough to maintain the walls of the bubbles when the air cools and condenses. I'm sure that anyone who has baked such a cake knows that the process can be very tricky. A lack of beating of the batter will result in too little air and the cake will not rise. On the other hand, too much beating will result in too many bubbles and not enough batter surrounding each to hold the air in and the cake will not rise.

About the Author

Angelique Gervais owns and operates a graphic design business serving rural areas in Northern Saskatchewan, Canada. She recently completed editing and compiling an anthology for her local writers' group, of which she is an active member. Angelique holds a degree in Biblical Studies, and she is currently expanding her education in the areas of psychology and human development at the Masters level.

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