Physical properties and glycemic index studies of Singaraja white rice grown by conventional and organic methods in Denpasar Bali Indonesia

Abstract

Both Singaraja white rice grown by organic and conventional method showed similar quality and posses glycemic index of 46.8±4.03 and 48.2±4.65 respectively. These values are lesser than the commercial Basmati rice of 50±5.8 which is in the low GI category. The scanning electron macroscopy photomicrograph of the transversal section of both rices show the array of crystalline blocks from the central endosperm area toward the outer part. The blocks are surrounded by polyhedral crystallites of the size between 3-6 microns. The polyhedral crystalline seem to be more dominant in the conventional rice. X-ray difrractograms of the rice indicate about 24% crystallinity with amylose dihydrate exist as polymorph in the organic rice. Elemental analysis data by XRF indicate organic rice contains slightly higher Magnesium and Phosphorus. Other elements detected were K, Al, S, Cl,O, Si, Zn, Ru, Ni, Pd and Fe. However, no iron was detected in the conventional rice . On the other hand no calcium was detected in the organic rice. Thermogravimetric study showed the solid rice is stable up to about 200°C with the loss of water molecules at about 90°C.