Susceptibility of Various Starch Granules to Amylases as Seen by Scanning Electron Microscope

Starch granules were observed by a scanning electron microscope in order to provide information concerning the types and extent of damage of the surface and internal structure of starch granules attacked by amylases. Granules resistant to the action of amylases, namely, potato, yamanoimo, and high‐amylose maize starches showed shapes and surfaces similar to the intact granules after the action of either Rhizopus glucoamylase or crystalline bacterial α‐amylase. Granules susceptible to amylases, namely, normal, waxy, soft starch, and soft starch opaque‐2 maize starches showed numerous pin holes on the surface layer and pores penetrated into the inner layers of the granules during the attack with amylases. In the case of α‐amylolysis, it is apparent that once the enzyme has penetrated into the inner layers of a granule, the layers are more readily attacked than the peripheral layers.