Xanthan gum orignates from a polysaccharide produced by the bacteria Xanthomas campestris, which, evidently, is where it got its name from. This bacteria produce a slimy substance that is responsible for the black spots formed on vegetables such as broccoli and cauliflowers. The United States Department of Agriculture discovered xanthan gum by combining Xanthomas campetris with corn sugar, to develop the colourless slime thickening agent similar to corn starch and guar gum.
The primary useful property xanthan gum has is its ability to act as a thickening agent and a stabilizer. Xanthan gum can increase the viscosity of liquids with very small concentrations. This increase in viscosity will be affected with higher shear rates, a phenomenon called pseudoplasticity. In other words, when the xanthan gum solution is experiencing mixing, shaking, or chewing, the solution will thin out and become more liquid, but once the shear forces are removed, the solution will thicken up again. For this reason, xanthan gum is a perfect agent to be added to salad dressings and sauces. For example, xanthum gum would be able to create a homogenous mixture with no clumps and all ingredients evenly spread out in a salad dressing. In addition, the salad dressing will thin out under shaking or mixing making it easier to pour. Once it has been poured, it thickens up and has a tendency to cling to the salad instead of sinking to the bottom of the dish or bowl. As for sauces, xanthum gum helps to prevent oil separation by not acting as an emulsifier, but as a stabilizing agent. Other uses include helping to keep a smooth texture in ice cream and toothpaste. In gluten-free baking, the gluten is replaced by xanthan gum in wheat to give the dough the “stickness” that it originally had before gluten was removed. Xanthan gum is added to a lot of other foods and beverages because it does not change the taste or the color.
Some people are found to be allergic to xanthan gum. They often have symptoms of diarrhea, temporary high blood pressure, and headaches. Because the bacteria that produce xanthan gum is often fed corn sugar, people allergic to corn may be allergic to xanthan gum as well.
References: (1) http://en.wikipedia.org/wiki/Xanthan_gum
