Starch is composed of amylose and amylopectin. Amylose is a straight chain and Amylopectin molecule is tufted. The ratio depends on the type of starch. In general, the more starch include amylose the more it is easy to age.
Starch containing no amylose is called Waxy rice starch in the case of rice and Waxy cornstarch in the case of corn.
Amylose and amylopectin are molecule of glucose connected.