Starch

Starch, a carbohydrate that makes up about 70% of flour by weight, also gets in on the act.

When starch granules are attacked by enzymes present in flour, they release the sugars that yeast feeds on.

Starch also reinforces gluten and absorbs water during baking, helping the gluten to contain the pockets of gas produced by the yeast.

Sometimes, a baker will let the dough rise several times, allowing the gluten to develop more completely and the yeast to add more of its flavors.

When the dough is finally cooked—either in an oven, over a fire, or in a steamer, depending on what kind of bread you’re baking—the yeast inside it continues feeding, and the pockets of gas in the dough continue to expand.

As the temperature of the cooking dough rises, the yeast eventually dies, the gluten hardens, and the dough solidifies. Et voilà! Bread!