Why does bread rise?
Bread rises because tiny living fungi called yeast eat sugar and breathe out bubbles of gas.
These gas bubbles get trapped inside a stretchy protein called gluten. As the yeast produces more gas, the gluten stretches like a balloon and makes the dough grow larger. This process creates the small holes you see in a slice of bread.
Nerd's Section
The specific fungus used in baking is called Saccharomyces cerevisiae. When mixed into dough, it breaks down starches from the flour into simple sugars. The yeast then eats these sugars to get energy. This process is called fermentation.As the yeast eats, it releases carbon dioxide gas and a small amount of alcohol. Wheat flour contains two proteins called glutenin and gliadin. When you add water and stir or knead the dough, these proteins link together to form gluten. Gluten is a strong and elastic network that holds the gas bubbles inside.When the dough goes into the oven, the heat makes the gas bubbles expand even more. This is called oven spring. The yeast works very fast until the temperature reaches about 140°F (60°C), which is when the yeast dies. The heat eventually hardens the gluten and starches to keep the bread's shape.Humans have used this biological process for thousands of years. Evidence shows that people in Ancient Egypt were making leavened bread as early as 3000 BCE. Today, scientists still study yeast to understand how it turns sugar into energy so efficiently.
Verified Fact
FP-0003807 · Apr 14, 2026