Physicochemical properties of brown rice as influenced by gamma irradiation, variety and storage

Effects of gamma irradiation, variety and storage on physicochemical properties of brown rice from three Louisiana rice varieties: Mars, a medium grain variety, Lemont and Tebonnet, long grain varieties, were determined. Cooking time was significantly reduced in Mars and Lemont at doses of 200 and 300 Krads. Irradiation increased cooking rate, water uptake at 80 degree C, water uptake ratios, total solids content in residual cooking liquid and starch damage from 100 to 300 Krad samples. Water uptake at 96 degree C generally decreased with increasing dose levels. Evidence indicated alterations in the rice grain structures and composition. The component drastically affected by gamma irradiation was starch as shown by reduced cooking time, increased water uptake, increased amounts of starch and protein in residual cooking liquid, reduced volume expansion, increased damage starch and changes in amylographic pasting characteristics. Scanning electron microscopy showed more simple starch granules in irradiated samples than in nonirradiated samples. Structural changes in the bran layer due to gamma irradiation were not evident from electron micrographs