Morphological and Rheological Properties of Starches Separated from Cultivars of Rice ( Oryza sativa L.) from North East India

Abstract

Starch granules isolated from different accessions of rice from North East India showed a typical polygonal morphology with size ranging from 3.4 ± 0.8 µm to 6.4 ± 1.2 µm. The apparent amylose content (AAC) of the granules varied from 1.9% to 28.33%. Our results identify starch from IC-583088 as " waxy " and IC-583085, IC-583038, DPRR-168 as " very low " amylo-. The coefficient of resistance to flow (n) for starch pastes from the varieties of rice studied in the present investiga-tion recorded a value of <1.0. The observed " n " value deviates from the Newtonian flow indicating the pseudoplastic nature of starches isolated from these varieties. While starch pastes from the accession IC-583088 recorded the highest ''n'' value of 0.6, that from the accession IC-545197 showed the lowest value of 0.03. The variations in coefficient of resistance to flow clearly revealed a higher ''n'' value for starch pastes from the " waxy " and ''low " amylo-cultivars than the " interme-diate " or ''high " amylo-cultivars. Our results clearly established characteristic rheological proper-ties for starches from the accessions SKY-AK-1608, IC-583035, YS-RC-219, IC-564939 and IC-332963, which exhibited greater resistance to thinning and shearing than other varieties.