Morphology of modified starches prepared by different methods

Morphologies of modified starches prepared using different methods were examined by scanning electron microscopy (SEM). These SEM micrographs provide the following results. To begin with, starch granules underwent a series of changes which resulted in the morphology of modified starch quite different from the native starch with different the methods during the process of modification. For example, hollows emerge on the granules of maltodextrin with low value of dextrose equivalent (DE) prepared by means of spray-drying, but they fell to pieces with the increasing value of DE. The granules of pregelatinized starches manufactured with extrusion technology also showed irregular stone shapes and holes within them while those produced by means of drum-drying presented irregular laminar structure. Furthermore, the granules of granulated cold water soluble (GCWS) starch obtained from alcoholic-alkaline treatment had indented appearance and larger volume than those of the original native granules. The conclusion can be safely drawn that the granule structure of slight modified starches did not change but the surface of the granule was porous.