Outer shell, inner blocklets, and granule architecture of potato starch.

Potato starch was heated in distilled water and acetic acid solution (pH = 1.5), respectively, then washed with anhydrous ethanol and dried. After cooked in water with certain program, high-resolution scanning electron micrographs (SEM) of broken granules showed isolated outer shells. After treatment with acetic acid, SEM images of dissilient granules exhibited outer shells with randomly assembled spherical inner blocklets. A refined blocklet model was proposed for potato starch granule, the smaller blocklets were compacted densely to form the stiffer outer shell, and the larger blocklets were packed loosely to form the inner shells.