Gamma radiation influences pasting, thermal and structural properties of corn starch

• Gelatinization temperatures decreased with increasing irradiation dose.
• Starch crystallinity was not affected by gamma radiations, until a dose of 50 kGy.
• Gamma radiation caused a depolymerization within the amorphous regions.

Irradiation is one of the effective methods able to change starch structure and its functional properties. In this research, the effect of γ-radiation (3, 5, 10, 20 and 50 kGy) on the pasting, thermal, structural and morphological properties of corn starch was studied. Brabender viscoamylograph test showed that the maximal consistency of the starch paste and its corresponding temperature decreased significantly with increasing irradiation dose. Differential scanning calorimetry also showed a decrease in gelatinization temperatures (TOnset, Tp, TOffset) with increasing irradiation dose. Fourier transform infrared spectroscopy spectra showed that the irradiated starch displayed a significant decrease in the intensity of O–H stretch, C–H stretch, bending mode of water and bending mode of glycosidic linkage. No modification in the shape and intensity of X-ray diffraction peaks was observed after irradiation. These results suggested that until 50 kGy, γ- radiation would affect the starch granule membrane and the amorphous zone rather than the crystalline one.