What arrowroot powder means
Arrowroot powder is the form in which arrowroot is sold and used in the kitchen. It is a fine, silky, bright white starch, extracted from the roots of the arrowroot plant, washed, dried and ground. You will also see it called arrowroot starch or arrowroot flour, which are the same product. Because it is pure starch, it behaves very differently from wheat flour, and it is used mainly as a thickener rather than as the main ingredient in a bake.
Like other starches, arrowroot powder needs to be mixed with a little cold liquid first, to make a smooth paste called a slurry, before being stirred into a hot sauce. If it is sprinkled straight into hot liquid, it forms lumps. It thickens quickly and at a relatively low heat, giving a clear, glossy result that suits fruit sauces, pie fillings, glazes and stir-fry sauces. Overheating or prolonged boiling can make it thin again, so it is usually added towards the end.
It is less successful in sauces made with milk or cream. In baking, a little arrowroot powder is sometimes mixed with flours to lighten cakes and biscuits. It should be stored in an airtight container away from damp. You will see it in sauce, glaze and pie recipes.