2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Density-gradient ultracentrifugation has been widely used for the fractionation of biomacromolecules such as protein and nucleic acid, but not for starch. Ultracentrifugation has an advantage over size exclusion chromatography in separating macromolecules because it is more effective without size limitation in column. In this study, starches of different origins were fractionated in Nycodenz, a gradient media, by their buoyant density using an ultracentrifugation, and the fractons were analyzed by phenol-sulfuric acid method and blue value. Amylopectin, which is uniform in shape and highly branched structure, showed very sharp peak at a relatively high density region (~1.26), whereas amylose, relatively linear molecules, appeared in broad and lower density region (1.12-1.21). This result may indicate that amylose is heterogeneous in its structure. The optimum centrifugal conditions for the separation of amylopectin and amylose were established, and the relationship between the density profile and chain conformation reported in literatures was discussed.