In order to obtain more information on the structure of corn starch granules, normal and waxy corn starches were both isolated and hydrolysed with a-amylase and amyloglucosidase. Sephadex G-50 gel-permeation chromatography of the a-glucan of normal and waxy corn starches was performed directly and after successive enzymatic digests with pullulanase and b-amylase. The results showed differences in the residues of the waxy and normal corn starches treated with a-amylase and amyloglucosidase. The elution patterns of the waxy corn starch residue showed two fractions at 290 and 350 ml (peak II and III) respectively, which were not susceptible to the a-amylase and amyloglucosidase attack indicating that these fractions took part in the waxy starch cristalline areas. These fractions also took part in normal starch cristalline areas. However, in addition to two chains not susceptible to hydrolysis, the presence of the peak V at 390 ml on the a-glucan of the normal corn starch suggested the existence of another fraction that also took part in normal corn starch cristalline areas forming tightly associated cristalline network. The presence of this peak at 390 ml suggested the distinct cristalline arrangement between the waxy and normal corn starches.
starch; structure; corn
