The firmest noodles are made from starches high in the straight-chain amylose form (p. 457). Where ordinary long-grain rice is 21–23% amylose, special noodle rices are 30–36%, and mung-bean starch is 35–40% amylose. Starch noodles are made by first cooking a small amount of dry starch with water to make a sticky paste that will bind the rest of the starch into a cohesive dough. The paste is mixed with the rest of the dry starch and more water to make a dough with 35–45% moisture, and the dough is then extruded through small holes in a metal plate to form noodles. The noodles are immediately boiled to gelate all the starch and form a continuous network of starch molecules throughout, and then are drained and held at the ambient temperature or chilled for 12–48 hours before being air-dried. During the holding period, the gelated starch molecules fall into a more orderly arrangement, or retrograde. The smaller amylose molecules cluster together to form junctions in the network, crystalline regions that resist disruption even by boiling temperatures. The dried noodles are thus firm and strong, but the less orderly parts of the network readily absorb hot liquid and swell to become tender without the need for active cooking.