Morphology and microstructure of maize starches with different amylose/amylopectin content

The morphology and microstructure of maize starches with different amylose/amylopectin ratios (waxy: 0/100; normal maize: 23/77; Gelose 50: 50/50; Gelose 80: 80/20) were studied by microscopy with ordinary and polarized light, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Generally, the granules of the amylopectin-rich starches were more regular in shape than those of the amylose-rich starches, but the surfaces of the amylose-rich starches were smoother than those of the amylopectin-rich starches. The birefringence and particle size of the granules were waxy > normal maize > G50 > G80, which also corresponds with the trend of molecular weight. Waxy and normal maize starches showed typical A-type patterns, while G50 and G80 show B-type patterns. Crystallinity increases with increasing the amylopectin content.