Effect of gamma irradiation on the physicochemical properties of alkali-extracted rice starch

• Irradiation significantly decreased swelling power, syneresis and pasting properties of starch.
• Increase in water absorption capacity, carboxyl content and light transmittance took place with irradiation.
• SEM images revealed surface cracking of starch granules with increasing irradiation dose.
• No significant difference was observed in the X-ray diffraction pattern of irradiated starches when compared with non-irradiated starches.

Starches isolated from two newly released rice varieties (K-322 and K-448) were subject to irradiation at 0, 5, 10, and 20 kGy doses. Comparative study between native (not irradiated) and irradiated starch samples was carried out to evaluate the changes in physicochemical, morphological and pasting properties due to gamma irradiation. Significant decrease was found in apparent amylose content, pH, swelling power, syneresis, and pasting properties, whereas carboxyl content, water absorption capacity, and transmittance were found to increase with the increase in irradiation dose. Granule morphology of native and irradiated starches under scanning electron microscope revealed that granules were polygonal or irregular in shape. The starch granules were somewhat deformed by gamma irradiation. X-ray diffraction pattern showed A type of pattern in native as well as irradiated starches.