HOW TO BAKE: WHY DO WE NEED TO KNEAD?
Bread dough needs to be elastic in order to capture the gases created by the yeast, stretch as bubbles form in the dough, expand, and rise. Without that elasticity, bread would not have the open texture we enjoy nor would bread be chewy. But what creates that elasticity?
The endosperm of the wheat contains two important proteins, glutenin and gliadin. When wheat flour is mixed with water, these two proteins link with the water molecules and crosslink with each other as they are physically manipulated by kneading. It takes a certain amount of physical manipulation to bring these molecules into contact and create strong links. As the kneading continues and these molecules create stronger bonds, gluten is formed. It is gluten that gives the dough elasticity.
If you watch the dough being mixed with the bread hook in your stationary mixer, you will see changes occur in the dough as the kneading takes place. First the dough will stick to the sides of the bowl. As the bonds become stronger and the dough more elastic, it pulls away from the sides into a drier ball. The sides should become clean. Within four or five minutes at medium speed, the dough will change even more and become elastic as the gluten is completely formed. After you have watched this process a few times, you will be able to recognize the changes in the dough as the gluten forms. If you pinch a portion of the dough and stretch it, it should pull to a thin layer before it breaks. Without that elasticity, bread isn't good bread.
Courtesy of the Prepared Pantry - www.preparedpantry.com