Evaluation of Amylose and Amylopectin Structure on Quality of Iranian Rice

This study investigated the influence of type and structure of starch components on the cooking quality of Iranian rice varieties. Six traditional Iranian rice cultivars were harvested, their drying and moisture contents were adjusted, they were milled and their white grains and flour were evaluated in a completely randomized design. The starch properties of amylose content, gelatinization temperature and gel consistency were measured. Characterization of polymeric structure of amylose and amylopectin was evaluated using chromatographic methods. Although there was little difference in amylose content, gelatinization temperature and gel consistency, the results showed significant differences at the 1% level for amylose and amylopectin hot water-soluble components and degree of polymerization. The rice varieties of good quality were Hasansaraee, Tarom and Domsiah; these showed higher hot water-soluble amylose content in results of size exclusion chromatography. The chain length distribution of amylopectin chains and the degree of polymerization were determined by capillary electrophoresis. Selected varieties showed significant differences for A, B1, B2, B3 and longer chains at the 1% level. The results showed that good quality cultivars, such as Domsiah, had more short chains (A) with less polymerization. There was no difference between the B1 and B2 chains by cultivar. The greatest difference was found between short chains (A), B3 and long chains. Differences in the polymeric structure of rice grains also should be considered to obtain more accurate analysis and new insights into quality.