What are gluten proteins and what is their role in bread making?

Julien Serere

There are as many as 30 different types of protein in wheat, but only two of them, glutenin and gliadin, form an elastic substance known as gluten when stirred with moisture. Viewed alone, gluten is a tough, elastic substance resembling chewing gum. When wheat flour is moistened and manipulated through stirring, beating and kneading, these two proteins grab water and connect and cross-connect to form elastic strands of gluten. If a flour has a lot of these proteins, it grabs up water faster, making strong and springy gluten. Like a net, gluten traps and holds air bubbles. They later expand from the gas from the leavening when a recipe is baked, causing the dough or batter to rise. During baking, the stretched flour proteins (gluten) become rigid as the moisture evaporates in the heat of the oven, and sets the baked goods structure. The viscoelastic properties of gluten provide the perfect combination of elasticity and rigidity by expanding with the gas while still retaining its shape. No other grain has been able to replace this function of wheat in baking.

See also :

http://www.nutrition.org.uk/upload/Flour%20pdf.pdf