daily · FOLLOW YOUR CURIOSITY
Where do the holes in bread come from?
A slice of bread preserves the outline of tiny gas pockets. Its structure begins before the dough enters the oven.
Explore the interactive discovery →
Start with what you see
In yeast-raised wheat bread, yeast consumes sugars and produces carbon dioxide. The dough needs to retain gas to rise. Hydrated flour proteins form a gluten network that can stretch around expanding pockets.
What is happening?
Baking expands the pockets and sets the surrounding structure. After cooling, the spaces remain as holes in the crumb. Gas production and gas retention are different jobs; both shape the loaf. Other breads can use different grains or leavening methods.
Try a concrete example
Imagine a gas bubble inside a soft material. Making more gas is only useful for expansion if the surrounding material can retain it. This separates gas production from the structure that holds the bubbles. A dough that rises and a finished loaf are also different states: heating changes the structure as baking proceeds. The holes visible in a slice are a record of that process, but their size alone cannot tell you every ingredient or every step of the recipe.
AN IDEA TO TAKE WITH YOU
A light loaf needs both a source of gas and a structure that holds it.
Follow a connection
How can tiny animals build a reef? →
Yeast helps shape a loaf. Coral polyps build a much larger structure through a different biological process.
Sources and transparency
Exploratorium · Bread Science 101
Accessed: 2026-10-31
Journal of Food Science Education · The Science of Pizza
Accessed: 2026-10-31
Illustrations explain an idea. Sources are available above.