Gamma irradiation induced structure changes of corn starch: a combined effects of amylose and moisture contents

Gamma irradiation is a common physical method used for starch modification to alter its physiochemical properties. Most studies have focused on the effects of moisture or amylose content independently on the gamma irradiation of starches. However, the hydration of starch granule was significantly influenced by the amylose content and its location. A comprehensive understanding of the synergistic effects of amylose and moisture content on the gamma irradiation of starches is of fundamental importance.

The waxy, normal and high amylose corn starches were treated with gamma radiation at moisture contents of 12%, 31% and 50% (w/w), respectively. The radial swelling of the starch granule played the key role in starch destruction under gamma irradiation treatments. The damages emerged in the sequence of crystalline lattice, semi-crystalline and amorphous growth rings following the locations of the water distribution in starch granule. An increase in moisture content made the amorphous region expand, which resulted in a better rearranged amylopectin side chains. Accordingly, the destruction of glycosidic bonds located in amorphous region by gamma irradiation makes the rearranged crystalline layer stay in situ. Consequently, the repeat distance of semi-crystalline lamellae and the relative crystallinity of waxy, normal and high amylose corn starch increased with an increase in moisture content after gamma irradiation.

Amylose restricted the radially and tangentially swelling of the starch granule, such that the damage to starch granules induced by gamma irradiation decreased with the increase in amylose content. Meanwhile, the locations of water and amylose simultaneously determined the destruction degree of starch granules by gamma irradiation. © 2025 Society of Chemical Industry.