Impact of γ- irradiation on the physico-chemical, rheological properties and in vitro digestibility of kithul (Caryota urens) starch; a new source of nonconventional stem starch

Kithul (Caryota urense) starch was exposed to gamma irradiation at different doses (0.5 kGy, 1 kGy, 2.5 kGy, 5 kGy, 10 kGy). Its impact on physico-chemical, morphological, rheological properties and in vitro digestibility of kithul starch was studied. Irradiation decreased the pH, swelling index, amylose and moisture content of kithul starch and increased the carboxyl content, acidity, solubility. Free radical-mediated damage developed cracks and fissures on the granular surface of starch. Fourier transform infrared spectra (FT-IR) showed a marked reduction in the hydroxyl (OH) groups after irradiation. Irradiation did not affected to the crystalline pattern of native starch (Type-A pattern) but it decreased the relative crystallinity of kithul starch. Irradiation increased the light transmittance and freeze-thaw stability, but it reduced the syneresis. Pasting viscosity decreased after irradiation treatment. Irradiation made significant changes in the gelatinization properties of kithul starch. In vitro digestibility of kithul starch improved after irradiation and resistant starch followed decreasing trend. Lower value of storage modulus and loss modulus of irradiated kithul starches indicated to its weak gel formation.