Structural and Functional Characteristics of Endosperm Starches From Korean Rice Cultivars.

Rice (Oryza sativa L.) is one of the most important foods in the human diet and the major agricultural crop in most Asian countries. It is rich in genetic diversity, with thousands of varieties being grown throughout the world. Carbohydrates are the most abundant component in rice, which has a starch content of approximately 90 percent of the dry matter. In the present study, by sampling Korean rice cultivars with different amylose content, we examined the starch granule characteristics and functionality of rice endosperm. Amylose content of rice starches was determined by iodine-binding method, and varietal difference in the wavelength of maximum absorbance and the blue value among rice cultivars was exhibited. Rice amylopectins were measured by the high performance anion exchange chromatographic analysis, and the distributions of the amylopectin chain length in all of the samples were classified into four fractions according to chain length. Long chains of DP (degree of polymerization) 25-36 of the inner endosperm starches showed higher proportion than the outer endosperm from rice cultivars. Rice cultivars had different peak height and crystallinity of X-ray diffractions of starch granules, B-type starches had higher proportions of longer amylopectin chains than A-type starches. In the thermal properties of starches, transition temperatures and enthalpies of gelatinization differ significantly among the cultivars. We could also found that the rice cultivars had different levels of the enzymatic hydrolysis rate and TAaGTase-modified starches.