Characterization of remaining granules of acetylated starch after chemical surface gelatinization

One acetylated waxy potato starch and three acetylated normal potato starch samples were treated with aqueous calcium chloride (4 mol/L) for surface gelatinization. The remaining granules after removal of gelatinized starch were investigated on size distribution and level of acetylation. Their crystal structure, thermal property and morphological change were studied with X-ray diffractometry, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Greater proportions of the acetyl groups were present at the periphery than at the core of the granule. Remaining granules obtained after higher degree of gelatinization showed greater relative crystallinity and gelatinization temperature. Morphology of gelatinized starch and remaining granules differed for acetylated waxy and normal potato starch samples. The results suggest that structural divergence exists not only between acetylated waxy and normal potato starches, but also within one granule.