The gluten in wheat is elastic and expands when baked, allowing breads, cakes, cookies and dough to maintain their shape without falling or crumbling. However, since the flours used in gluten-free baking do not contain gluten, something must be added as a binder to create these same elastic qualities and help goods hold their shape.
There are ingredients and methods for preparing gluten-free baked goods that can add structure and keep baked goods tender. You can build structure without gluten. Gluten-free baking has evolved over the past few years, ever since dedicated bakers discovered new tricks. Because gluten plays such a critical role in the structure of baked goods, replacing it can be difficult.
Gluten is the stretchy protein that forms when wheat flour is exposed to water and is manipulated, either through beating or kneading. This protein forms a literal web that traps air, creating the crumb, or texture, of breads, cookies, cakes, and pastries.
Since the start of gluten free baking there have been two gluten substitutes that have reign supreme, xanthan gum and guar gum. They are used to bind, thicken and emulsify gluten-free ingredients.
Xanthan gum is a corn-based, fermented product. It's made by fermenting corn sugar with a microbial called "Xanthomonas campestris." It's used extensively in the food industry to make products thicker and it's a common ingredient in gluten-free recipes. Using too much xanthan gum in a recipe will produce a heavy, gummy or even slimy texture in your baked goods.
Guar gum comes from the seed of bean-like (legume) plant, sometimes referred to as the Indian tree. It is high in soluble fiber. Guar Gum has eight times the thickening power as cornstarch. Like xanthan gum, measure carefully when using guar gum in gluten-free recipes or you may end up with heavy, stringy baked goods.
Gums form a stretchy web when mixed with water, which replicates gluten’s structure. But xanthan gum is expensive, and some people who are sensitive to gluten are also sensitive to xanthan gum. Both xanthan gum and guar gum have laxative properties, which can cause digestive distress in some people. Also these substances have their limitations in baking, they have no nutrient value and they don't provide flexibility or strength in your final baked good.
The latest incarnations of gluten-free breads, cakes, and cookies use no gums, gelatin, or artificial structure-makers at all. Gluten-free bakers have found that using a combination of gluten-free flours and starches and using more natural gluten imitators helps mimic the structure provided by wheat flours. This knowledge, combined with new weighing and mixing methods, has revolutionized the gluten-free baking world.
If you want to avoid gums or other artificial add-ins, you need to combine gluten-free flours and starches. No single gluten-free flour has the characteristics, protein content, and starch content to single handedly replicate wheat flour.