What Kind of Stuff is Dough?
Is dough, in chemical terms, a mixture, a colloid, a solution, or a gel? Once you have added the liquid ingredients to the dry and stirred the mixture sufficiently to make it homogeneous, it is no longer a mixture because there is no mechanical process that can separate the flour, salt, water, and other ingredients back into their starting states. A colloid, also known as a colloidal suspension, consists of chemically distinct particles dispersed evenly throughout a liquid medium. A well-blended vinaigrette, for example, is a colloid; so is mayonnaise. Dough is not because the substances in it don’t aggregate into particles (some gluten-free doughs are exceptions).
Dough made with wheat flour certainly contains a highly concentrated solution of salts, sugars, proteins, fats, and starches, all dissolved in a relatively small amount of water. But the network of tangled gluten proteins that gives dough its elasticity traps minuscule pockets of that solution, like fish in a net. Raw dough is thus a gel, technically speaking. Dough that has risen contains tiny bubbles of gas, which fill with water vapor, carbon dioxide, and air as the dough bakes and solidifies. Proofed dough is a closed-cell foam; bread is an open-cell foam (like a sponge). Fully baked bread, then, is a set foam. Like other solid foams, bread is an insulator that tends to trap heat rather than transmit it, which is one of the reasons it takes over 30 minutes or more for a loaf to reach a modest core temperature when it’s baked.