About Xanthan Gum and Guar Gum
Xanthan or Guar Gums are often called for in GF flour mixtures used for baking. They apparently help the texture of the GF baked goods - helping to add "elasticity" into the dough that is missing in GF flours. It helps to make things chewy, rather than fall apart. Most recipes only call for from 1/4 to 1/2 tsp. per cup of flour, so a little goes a long way. Bob's Red Mill Xanthan Gum is sold at stores such as Whole Foods, Henry's, and Jimbo's. But it is also sometimes sold in "regular" grocery stores when they have a large GF section.
The following articles provide more information about these gums:
"How to Use Xanthan Gum and Guar Gum in Gluten-Free Cooking" on About.com.
"Questions & Answers - Zanthan gum, Xanthan Gum, Guar Gum" on What's Cooking America.net
Xanthan Gum information on Wikipedia
Guar Gum information on Wikipedia
Guar Gum information on WebMD
The following are thoughts about xanthan gum and guar gum and their purpose in gluten-free cooking.
Jeanne Jones in "Cook It LIght" Column in San Diego Union Tribune, 9/29
"When using gluten-free flours in baking, it often is necessary to add xanthan gum, which is produced from the fermentation of corn sugar. It makes up for the structure lost by omitting gluten. Without the xanthan gum, baked goods tend to lack texture and structure, and will crumble. Add 1/4 tsp. per cup of flour for cakes, and 1/2 tsp. per cup of flour for cookies, quick breads and muffins."
David to SillyYak site 9/09
"Xanthan gum is a binder that's used in conjunction with GF Flours, partically handy if you bake from 'scratch'.
Most people these days seem to use a pre-made flour blend or Bread / Cake Box Mixes which already have Xanthan or Guar Gum included.
Unless you intend baking from 'scratch' (using seperate flours in a recipe) then the is no other use that I'm aware of for Xanthan Gum."
Chandra to SillyYak site, 9/09
"Xanthan gum is a dried gum substance usually (but not always) derived from corn. Those with severe corn allergies should use guar gum, which I believe is a sort of seaweed derivative (though I could be wrong).
In commercial food products, small amounts of xanthan gum are used for thickening and binding. Xanthan gum is EXTREMELY gummy and slimy. If you ever spill the dry powder, do NOT use a wet towel or sponge to wipe it up, It will just turn into super slime! Get up as much as you can with a whisk broom or small brush before using a barely-damp paper towel to take up the rest without turning it actually wet.
In GF baking, xanthan gum is added in small amounts (usually 1/2 to 1 teaspoon per cup of GF flour) to add stretchiness and "spring" to the baked goods. It is absolutely necessary to add xanthan or guar gum to GF yeast breads so they don't just crumble away to nothingness once they are baked. Most GF baking mixes already have the xanthan gum added, so you only really need to keep it around for scratch baking.
Since you only use a little bit at a time, a package of xanthan gum can last a long long time. So in spite of the high price tag, it is really quite cost-effective. Hope this helps!"