Hydrolysis of granular corn starch with controlled pore size

Native corn (Zea mays L.) starch granules were hydrolyzed using glucoamylase at 50 °C for 1–8 h. The degree of hydrolysis over time was analyzed by the concentration of glucose released into solution. The pore sizes of hydrolyzed starch granules increased gradually with the degree of hydrolysis, as evidenced by scanning electron micrographs. It was deduced that every pore on the surface of granules was formed by hydrolysis of one enzyme molecule, so the size of pores distributed on the surface of starch granules was almost homogeneous for the same hydrolysis time. The specific surface area (S_BET), porosity, adsorptive capacity and mean pore radius of porous starch granules were determined to analyze the effect of digestion time on granule properties.