Xanthan Gum is used to thicken liquids liquids, such as sauces, cream, juices, soups, pastes. It it essentially works like a more traditional starch or flour, yet it takes only a very small amount of xanthan gum to thicken, and as such, it does not affect the true flavor of the sauce by making it too starchy tasting. In molecular gastronomy, it is also used to thicken and stabilize suspensions and emulsions. The viscosity does not vary for hot or cold applications. Xanthan gum has the wonderful ability to thicken acid based solutions or alcohol. Another property of xanthan gum thickened mixtures is that they seem somewhat firm until you pour them, at which point they are very free flowing. As with agar and lecithin, the concentration used is a very low ration. 0.5 percent by weight, more than this affects the texture. Xanthan gum is actually glucose that has been fermentated with the a bacterium called Xanthomonas campestris.
Vegan and gluten free cooks will find xanthan gum particularly helpful, as it can aid in the rising of baked goods and give them a tender crumb.