The starch is characterised by a content of about 25% amylose with the remainder being amylopectin and the intermediate fraction (see 3.5 Biochemistry). But these percentages vary among cultivars and with kernel development. For example, amylose percentage ranged from 20 to 36% for 399 cultivars of normal maize.[22][23] There are maize germplasm collected that range from less than 20 to 100% complement of amylopectin.[21] And waxy maize contains 100% amylopectin.[12]
Waxy starch is of main interest because fractionation of normal starch to obtain pure amylose or amylopectin is very costly.
Waxy endosperm is inherently a defect in metabolism, and its low frequency in most maize populations in the face of recurring mutations indicates that it is acted against by natural selection.[5]