The Basics of Gluten:
Gluten is a combination of the natural proteins found in wheat, and to much a lesser extent, in rye and barley. Gluten molecules are activated when flour is moistened and then either kneaded or mixed. When this happens, the glutens literally stretch out.
Then, the gases produced by yeast or another leavening agent inflate these gluten molecules like little balloons, which is what permits doughs to rise. Finally, when the dough is baked, the gluten hardens, giving the bread its structure.
Gluten in Flour:
There are different varieties of wheat, each with its own gluten content. Flours made from high-gluten wheats are called strong flours and are used for making bread, bagels, pasta and pizza crusts. Flours made from softer, low-gluten wheats are called weak flours, and are used for making cakes and delicate pastries.
All-purpose flour is formulated to have a medium gluten content of around 12 percent or so. This makes it a good middle-of-the-road flour that can be used for a whole range of baking.
Gluten in Baking:
Without gluten, baked goods won't hold their shape. That's why wheat flour is used in baking. When the glutens in wheat are stretched out through the kneading or mixing process, they form little pockets which can then be inflated by the gases released by the leavening agent. When these air pockets inflate, the dough expands or rises.
And since gluten is a protein, it hardens when it is heated — just like the protein in an egg hardens when we cook it. This hardening of the gluten molecules is what allows the bread to hold its shape, and gives it its firm texture.
The more the dough is mixed or kneaded, the more the glutens develop. That's why we mix the dough for cakes or pastries for a shorter time than for crusty French rolls.
Gluten and Fats:
In baking, fats interfere with gluten development process. Cookies are more crumbly than bread because they've got more fat in them. What happens is that the fat molecules surround and literally shorten the strands of gluten so that they can't stretch out as much. That's where we get the name "shortening" as well as shortbread cookies.
Gluten in Other Foods:
Gluten is also a key component in foods that aren't baked, like pasta. The gluten is what gives the pasta its firm texture. Strong flours such as those made from durum wheat are good for making pasta because of their high gluten content. Pasta made from low-gluten flour would be too soft and mushy.
Baking Without Gluten:
Gluten provides structure and chewiness, but it's also the only way to create light, airy baked goods. That's because without gluten, breads won't rise. This is why, if you've ever tried gluten-free breads, they're so heavy and dense. They're really just lumps of starch.
That doesn't mean that grains that have little or no gluten aren't used in baking. It's just that they need a little help — in the form of wheat flour. Rye bread typically contains more wheat flour than rye flour. Corn also lacks gluten, which is why corn bread is made from about half cornmeal, half wheat flour.