Breads that use yeast are different from all other baked goods. It takes several steps to bake bread, and one step is to put the dough in a warm place and wait for it to rise. But why is that step so important—and why does bread dough rise, anyway?
What Causes the Dough to Rise?
Yeast! Recipes like our Basic Homemade Bread all call for “active dry yeast.” You may be surprised to know that yeast is a living thing. It needs to eat, like anything that’s alive, and it loves sugar. In a process called fermentation, the yeast feasts on any sugar in the bread dough and then burps! In the bread world, burping isn’t rude—the yeast is creating air bubbles in the bread dough.
(To wake up the yeast and get it ready for baking, you “proof” it. Here’s how that works.)
What Keeps the Air Bubbles in the Bread
The stretchy part of bread that holds the gas is called gluten. Gluten is formed when the proteins in flour come in contact with water, and as the two ingredients are kneaded, more and more gluten forms. This stretchy molecule traps air bubbles inside the dough.
Why Does Bread Dough Rise?
Bread rises because yeast eats sugar and burps carbon dioxide, which gets trapped by the bread’s gluten. The more sugar your yeast eats, the more gas that gets formed, and the higher the bread rises!
Most recipes call for the dough to rise at least twice; this gives the yeast extra time to eat sugar and produce gas bubbles. The yeast keeps eating even as the bread is shaped into a pans and put in the hot oven. When it’s done baking, you’re left with a solid, well-risen loaf created by that hard-working yeast. What an amazing (and delicious) process.