Effect of γ-radiation on physico-chemical, morphological and thermal characteristics of lotus seed (Nelumbo nucifera) starch.

Native and gamma (γ) irradiated lotus seed starches were studied for their physicochemical, thermal, pasting and morphological properties. Upon gamma irradiation of 5, 10, 15 and 20 kGy, amylose content of starches was decreased as the dose of irradiation was increased. Lotus seeds starch granules had bimodal size distribution varying in size from small to large. Observation under scanning electron microscope (SEM) showed that at low dose of irradiation (5, 10kGy), no significant changes were observed in shape and size. However, minor alterations were notice during treatment of 15kGy and 20 kGy, which included roughness. Irradiation significantly decreased the pasting properties (peak, trough, final and setback viscosities) of the starch. For native starch, To, Tp, and Tc of 137.44 °C, 138.29 °C and 143.21 °C and 169.51 °C, 169.72 °C, and 177.73 °C respectively was observed for first and second peak. Upon irradiation, the gelatinization temperatures were decreased. The irradiated starch showed no change in diffraction pattern compared to native lotus seed starch but a dose-dependent decrease in relative crystallinity was observed.