Xanthan gum is a binder that improves the quality of a gluten-free product. It prevents the cookies from spreading, helps with the crumbling problem, and improves elasticity. What IS it? A polysaccharide resulting from carbohydrate fermentation by a naturally occurring bacterium, Xanthomonas campestris (it's from corn; a strain of bacteria used during the fermentation process).
Use 3/4 teaspoon per cup of flour for muffins, biscuits, or scones. Use 1 teaspoon per cup of flour for cookies, cakes, pie crust, and pizza dough.
Guar Gum is another binding agent that can be used in place of xanthan gum for corn sensitive individuals (guar gum is actually guar seeds dehusked, milled and screened). Use half as much guar gum to replace xanthan gum. Guar gum contains fibre and can irritate very sensitive intestines.