Gamma Irradiation–Induced Structural Modification of Sorghum Flour and Its Impact on the Physicofunctional, Rheological, and Thermal Properties of Extracted Starch

This study is aimed at determining how gamma irradiation (5, 10, and 15 kGy) of sorghum flour affects the physicochemical, functional, pasting, and thermal characteristics of sorghum starch. The pattern of Fourier-transform infrared spectroscopy (FTIR) spectra and X-ray diffraction (XRD) intensity confirmed that starch structure and granules integrality were mostly preserved. Both native and irradiated starches revealed an A-type XRD pattern, with the irradiated starches showing lower crystallinity. However, scanning electron microscopy showed that the irradiation dose enhances the development of fissures and surface cracking on elliptical, irregular, and spherical starch granules. Starch impurities such as protein and fat decreased with increasing irradiation dose. Furthermore, the increased dosages were associated with increased solubility and syneresis. The flour also showed a remarkable improvement in the absorption of water (1.19 to 1.52 g/g) and oil (1.24 to 1.58 g/g) as the doses increased. Gamma irradiation–induced depolymerization and reduced crystallinity in sorghum starch also resulted in significant reductions in viscosity and changes in gelatinization temperatures, reflecting altered pasting properties and thermal characteristics. Overall, gamma irradiation at higher doses transformed the functional and structural properties of sorghum starch, suggesting potential applications in food and industrial sectors, where reduced retrogradation or viscosity is beneficial.