Changes in Physicochemical, Structural, and Sensory Properties of Irradiated Brown Japonica Rice during Storage

Brown japonica rice was treated with (60)Co γ irradiation at doses of 0, 0.2, 0.5, 1.0, and 2.0 kGy immediately after harvesting. The effects of irradiation on physicochemical, structural, and sensory properties during long-term storage (18 months) were investigated. The study revealed that the pasting properties, including peak, through, breakdown, final, and setback viscosities, decrease considerably in a dose-dependent manner and vary differently during 18 months of storage. Irradiation reduced the free fatty acid (FFA) content in comparison with unirradiated brown rice with long-term storage (from 12 to 18 months). Scanning electron microscope (SEM) observation showed that the mean range and shape of starch granules did not vary significantly. However, dark spots developed among starch granules and the narrow cracks became wider with increasing irradiation dose and storage time. During sensory evaluation, extremely low scores for odor and overall acceptability were obtained for medium-dose irradiated rice (1.0 and 2.0 kGy); however, no significant difference was found in acceptability between low-dose irradiated rice (0.2 and 0.5 kGy) and the control rice (0 kGy). Overall, low-dose (0.5 kGy or below) irradiation seems to be a promising alternative treatment to increase brown rice shelf life, without affecting the physicochemical and structural characteristics and sensory acceptability.