Xanthan gum is a polysaccharide that's commonly used as a food additive. The name is derived from the strain of bacteria used during the fermentation process that is used to make it, Xanthomonas campestris. This is the same bacteria responsible for causing black rot to form on broccoli, cauliflower and other leafy vegetables. The bacteria form a slimy substance which acts as a natural stabilizer or thickener. It was developed when the United States Department of Agriculture ran a number of experiments involving bacteria and various sugars to develop a new thickening agent similar to corn starch or guar gum.
Xanthan gum is considered a polysaccharide in scientific circles, because it is a long chain of three different forms of sugar. What's important to know is that all three of these natural sugars are present in corn sugar, a derivative of the more familiar corn syrup. The Xanthomonas campestris bacteria eat a supply of this corn sugar under controlled conditions, and the digestion process converts the individual sugars into a single substance with properties similar to cornstarch. This substance is used in dairy products and salad dressings as a thickening agent and stabilizer; it prevents ice crystals from forming in ice creams, and also provides a "fat feel" in low or no-fat dairy products.
Another use for the substance is the stabilization and binding of cosmetic products. One advantage of xanthan gum is that a little goes an incredibly long way; cosmetic manufacturers only have to add a very small amount of xanthan gum to their cream-based products in order to keep the individual ingredients from separating. Despite the use of bacteria during processing, the substance itself is not generally harmful to human skin or digestive systems, though some individuals may find they are allergic to it.
Xanthan gum is often used whenever a gel-like quality is sought. It is used as a substitute for wheat gluten in gluten-free breads, pastas and other flour-based food products. Those who suffer from gluten allergies should look for xanthan gum as an ingredient on the label.
One lesser-known use of xanthan gum is in the oil industry. As a thickener, it can be added to drilling fluid or drilling mud to improve its function. Drilling fluid serves several purposes, including cooling the drill bit, providing hydrostatic pressure, and helping to lift solids out of the borehole and keeping those solids in suspension when drilling stops.