In the culinary arts, arrowroot is a form of starch derived from the root of a plant that grows in tropical regions. Processed into a white powder, arrowroot is useful as a thickening agent for soups and sauces.
[Also see: How to Thicken a Sauce]
Arrowroot is sometimes used interchangeably with cornstarch, although there are differences. Arrowroot should not be combined with dairy products, as it can produce an unpleasant texture.
Arrowroot has a more neutral flavor than corn starch, but it tends to break down more easily when heated and can make sauces too elastic. On the other hand, it provides good shine and translucence, which is sometimes desirable, particularly in fruit pie fillings and fruit sauces. It also happens to be more expensive than cornstarch and other starches.
When using arrowroot to thicken a sauce, it would first be combined with a cold liquid to form a slurry, which is then added to the liquid to be thickened. The liquid is heated, which causes the starch in the slurry to expand and thicken the sauce. If it were added directly, without making a slurry first, it would clump up and create a lumpy result rather than a smooth one.