Effects of gamma irradiation on aspects of milled rice (Oryza sativa) end-use quality

In China, breeding efforts to create Indica-type rice cultivars with textural and functional properties similar to Japonica-type rice have not been successful. An alternative strategy is to develop a processing method to modify the end-use quality of Indica-type rice. Milled rice samples with low, intermediate and high apparent amylose content (AAC) were treated with Co-60 gamma rays. AAC was impacted only by high doses of gamma rays while gel consistency was significantly increased. Increasing levels of gamma irradiation (GIR) reduced rice flour viscosity and increased the temperature of gelatinization onset. Exposure to gamma rays caused the RVA setback (rice pasting properties) but not the instrumental texture properties of an Indica-type cultivar to become more like that of the Japonica-type rice. GIR of milled rice for human consumption would be limited to between 2 and 4 kGy because of its negative effects at higher doses on rice color and aroma. However, that level will destroy insects and some microorganism and change rice of unacceptable quality for some consumers closer to being acceptable and may also broaden the functionality of rice for industrial uses.