Gluten is a mixture of two proteins present in cereal grains, like wheat, barley, and rye which is responsible for the elastic texture of dough. Gluten also shows up in many whole grain foods related to wheat, including bulgur, farro, kamut, spelt, and triticale (a hybrid of wheat and rye). Because gluten is able to stretch elastically, it is desirable to have a higher gluten flour for yeast-raised products, which have doughs that are stretched extensively; like pizza, most breads, and bagels. For pie crusts, cookies, and pastry to be short and crumbly, a lower protein flour is better. Protein levels range from 7% in pastry and cake flours to as high as 15% in high-gluten bread flour. Protein in wheat flour indicates the amount of gluten available in the flour.
Gluten free grains still have high protein content (depending on the grain) but do not have the gluten proteins.
When regular flour is mixed with water, gluten is released and when you work the dough, the gluten gets more and more elastic. With bread and pasta you want a well worked dough to be as elastic as possible, but with pastry this is the opposite. When making a short crust pastry you want as little gluten elasticity as possible, which is why wheat and gluten-free pastry isn’t so difficult to get right. Butter and flour are the main ingredients in short crust pastry.
Working with gluten-free flour in baking is both an art and a science. It’s not a matter of simply swapping an equal amount of a single gluten-free flour for the amount of all-purpose or cake flour called for in a recipe. There are several types of gluten free flour, and even commercial gluten-free flour blends typically include several kinds of non-wheat derived flour in one mix. Some flours provide protein, some provide texture, some provide flavour. Coming up with the perfect mix for baking cakes that are gluten free but still perfectly light and fluffy without the benefit of gluten can prove somewhat tricky.
From above, gluten is what gives baked goods their structure. Without the gluten, foods are more likely to fall apart. By adding gums, such as xanthan gum or guar gum, you can replace some of that structure.
