ARS | Publication request: A method to determine the content, molecular weights, and weight-and molar-based distributions of degree of polymerization of amylose and fine-structure of amylopectin

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2006
Publication Date: January 31, 2007
Citation: Chen, M.H., Bergman, C.J. 2007. A method to determine the content, molecular weights, and weight- and molar-based distributions of degree of polymerization of amylose and fine-structure of amylopectin. Carbohydrate Polymers 69:562-578.

Interpretive Summary: Amylose is the most important grain constituent that influences rice end-use quality. It is also the major determinant used to define rice market classes. However, amylose content does not explain all attributes of rice quality. For instance, the high-amylose class is further divided into two subclasses, those quality types suitable for commercial thermal processing and those that are not. These quality differences within the same amylose class of rice suggested that new methods other than amylose content measurement might be needed. We are presenting here a new method for studying molecular structure of amylose and amylopectin. This method will be used for studying the association between starch molecular characteristics and functionality, as well as in starch-related genetics studies of rice.

Technical Abstract: Cooked rice texture and other aspects of rice starch functionality are influenced by amylose and amylopectin content and structure. A method is described that uses high performance size exclusion chromatography coupled with multiangle laser light scattering and refractive index detectors to determine amylose content, molecular mass of amylose and the weight- and molar-based distributions of degree of polymerization (DP) of amylose and the fine structure of amylopectin. The method is relatively rapid with the coefficient of variation less than 5% for most aspects of the molecular characterization. It should find utility in research programs studying the association between starch molecular characteristics and functionality, and in starch-related genetics studies of diverse botanical sources.