Arrowroot is a starch obtained from the rhizomes (rootstock) of several tropical plants, traditionally Maranta arundinacea, but also Florida arrowroot from Zamia integrifolia, and tapioca from cassava (Manihot esculenta), which is often labelled as arrowroot. Japanese arrowroot, Pueraria lobata, also called kuzu, is used in similar ways.
Arrowroot tubers contain about 23% starch. They are first washed, and then cleaned of the paper-like scale. The scales must be carefully removed before extracting the starch because they impart a disagreeable flavor. After removing the scale, the roots are washed again, drained and finally reduced to a pulp by beating them in mortars or subjecting them to the action of a wheel rasp. The milky liquid thus obtained is passed through a coarse cloth or hair sieve and the pure starch, which is insoluble, is allowed to settle at the bottom. The wet starch is dried in the sun or in a drying house. The result is a powder, the “arrow root” of commerce, that is quickly packed for market in air-tight cans, packages or cases.
Arrow root starch has in the past been quite extensively adulterated with potato starch and other similar substances. Pure arrow root, like other pure starches, is a light, white powder (the mass feeling firm to the finger and crackling like newly fallen snow when rubbed or pressed), odorless when dry, but emitting a faint, peculiar odor when mixed with boiling water, and swelling on cooking into a perfect jelly, which can be used to make a food that is very smooth in consistency—unlike adulterated articles, mixed with potato flour and other starches of lower value, which contain larger particles.