Xanthan gum is not the same as tapioca flour. It is a plant-based thickener and is used as a stabilizing or gelling agent. It works as an emulsifier and can be used for thickening. Xanthan gum has very strong thickening properties so when using it as a tapioca flour substitute to thicken liquids, use only an eighth to a quarter of the required amount. Start with a ¼ of a teaspoon and increase the amount slightly if it is not thick enough.