Gliadin and Glutenin

• Two proteins called gliadin and glutenin are contained in wheat. At the start of the kneading process, the dough will have a sticky, crumbly texture without the stretchiness characteristic of bread dough. This is because the gliadin and glutenin proteins have not yet come into contact with water or been mixed together. As kneading begins, they will undergo important changes.

Just Add Water

• Kneading the dough mixes the flour and water together, bringing the gliadin and glutenin molecules into contact with water molecules. When this happens, the proteins bond to the water and to each other, forming a new type of protein composite. This is gluten, which takes the shape of a long strand. Initially, there will be only a small number of these gluten strands, but more will form as kneading progresses.

Stretching the Strands

• As kneading continues, the texture of the dough begins to change, becoming stretchier and smoother. This is the result of more and more gluten strands forming. As kneading brings them into contact, they form longer and longer strands. The network of long, stretched-out molecular chains gives the bread its characteristic stretchiness. This stretchy texture will be important when the dough rises.

Gas and Texture

• Once the gluten strands have formed into a stretchy network, the dough is ready to rise. The yeast in the dough consumes starch and emits a number of waste products, including carbon dioxide gas. As the gas is released, the gluten strands envelop it, holding it in place like a balloon. These pockets of gas are what give bread its light, slightly chewy texture. If the gluten strands aren't present to hold in the gas, it will escape, giving the resulting product a dense, crumbly texture.