Gamma irradiation induced modification of bean polysaccharides: Impact on physicochemical, morphological and antioxidant properties

• Radiation processing increased solubility and water absorption capacity of bean starches.
• Decrease in swelling index can improve texture and reduce syneresis of frozen foods.
• Decrease in viscosity reduced the tendency of starches to retrograde.
• Irradiation increased the proportions of rapidly digestible and enzyme resistant starch.
• Irradiation caused significant enhancement in antioxidant potential of bean starches.

In the present study starches from four bean varieties viz. red, yellow, black and white, were gamma irradiated in the dose range of 5–25 kGy to investigate the effect of radiation processing on physicochemical, morphological and antioxidant properties. Studies revealed positive correlation between gamma irradiation and solubility (r = 0.91), irradiation and water absorption capacity (r = 0.82) and negative correlations between irradiation and swelling power (r = −0.92), irradiation and pasting properties (r = −0.91) and irradiation and thermal properties (r = −0.89). Microscopic observation under scanning electron microscope indicated the development of surface cracking and fractures on the surface of starch granules with increase in dose. X-ray diffractometry revealed no significant change in diffraction patterns between control and irradiated starches, except a decrease in relative crystallinity. Irradiation increased the proportions of both rapidly digestible starch and enzyme resistant starch of bean starches and significantly prevented the retrogradation of bean starches during storage. Results of the DPPH radical scavenging activity and ferric reducing power indicated significant (p ≤ 0.05) increase in antioxidant activity of all irradiated bean starches with increase in dose.