Effect of gamma radiation processing on the quality characteristics of anthocyanin rich ethnic rice cultivars

Rice (Oryza sativa L.) is one of the most important cereal crops that serve as staple food of more than 50% of the world population. In recent years great interest has been shown in pigmented & colored rice due to its culinary interest as well as associated health benefits. However, post harvest qualitative and quantitative losses in rice during storage through pests are significant; therefore strategies that are aimed at minimizing losses in the supply chain can have significant socio-economic impact as it may strengthen ‘Food Security’. Fumigation is quite often employed but it is being gradually phased out owing to health and environmental concerns. In the current investigation, effect of different doses of gamma radiation (0.25-1.0 kGy) on the quality attributes (gel consistency, water uptake, total anthocyanin content, phenolics, protein and antioxidant activity) of different prominent ethnic pigmented rice cultivars (5 types) from the state of Manipur, India was evaluated. The cultivars displayed significant variation in their physical quality attributes including dehusked grain color, grain weight and length/breadth ratio. No significant difference was observed in the gel consistency profile of these rice cultivars upon gamma radiation processing (0.25-1.0 kGy). A wide variation was observed in the total anthocyanin content (0.17-4.90 mgCy-3-glu/g in non-irradiated samples) for these pigmented rice cultivars and radiation processing was also observed to exert differential impact on the anthocyanin content (0.24-3.96 mgCy-3-glu/g in irradiated samples) in different cultivars. Total phenolics content (0.22-2.46 mgGAE/g in non-irradiated samples) marginally increased (0.32-2.47 mgGAE/g in irradiated samples) in all the rice cultivars upon radiation processing. Rice cultivars also displayed prominent antioxidant capacity (DPPH scavenging: 20.5-80.5% in non-irradiated samples) and this functional health protective property was found to be retained (DPPH scavenging: 20.8-80.7% in non-irradiated samples) upon gamma irradiation.