Photo: elana's pantry (Flickr)
Water and flour alone make a gluey mess, but with the heat of the oven, two different components of the flour exchange water molecules and in the process turn the dough into a sturdy, but spongy material we know of as bread.
Starch granules and gluten molecules are both present in the wheat plant and are the two main players in the process of converting flour into bread. At room temperature, the starch in flour is contained in small, hard granules that don’t absorb very much water. Gluten at room temperature consists of long protein molecules curled up and interspersed with water molecules.
Add Some Heat!
But starting at around 140 degrees Fahrenheit, a change occurs.
The protein molecules of the gluten straighten out and bond to each other–squeezing out the water molecules and forming a firm matrix around the starch granules and gas bubbles. At the same time, the starch molecules separate from each other and begin to absorb the water squeezed out of the gluten.
Gluten And Bread
It’s the gluten that gives the dough its strength, but the gluten also gives up water molecules to the starch granules. As the starch absorbs that water, the small, hard granules expand into moist, springy particles that give fresh bread its soft, moist character.
As the bread cools, the starch molecules contract, expelling some of the water, but for a few days, at least, most of the starch molecules stay spread out and hold onto the water. As the starch gives up its water and returns to hard granules, the bread gets stale. But that’s our topic for next time.