Arrowroot by John Spottiswood.

arrowroot starch = arrowroot powder = arrowroot = arrowroot flour This starch thickener has several advantages over cornstarch. It has a more neutral flavor, so it's a good thickener for delicately flavored sauces. It also works at a lower temperature, and tolerates acidic ingredients and prolonged cooking better. And while sauces thickened with cornstarch turn into a spongy mess if they're frozen, those made with arrowroot can be frozen and thawed with impunity. The downside is that arrowroot is pricier than cornstarch, and it's not a good thickener for dairy-based sauces, since it turns them slimy.