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Title: CALCULATION OF THE PERSISTENCE LENGTH OF SOLUBILIZED STARCHES FROM INTRINSIC VISCOSITY MEASUREMENTS

Author
item Carriere, Craig
item BAGLEY, EDWARD - BRDC

Submitted to: Journal of Rheology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Starch is a commodity polymer that is utilized today in a wide variety of commercial applications, both food and industrial. In terms of new industrial products, there are increasing opportunities under development in which starch is combined with other polymeric materials, both natural and synthetic. Starch offers both economic advantages, due to its low cost, and environmental advantages, due to its being a renewable, biodegradable material. However, properties of these starch-based materials are little understood because of the complex chemical and physical interactions of starch both with itself and with other components or solvents. This study presents some of the first measurements of the stiffness of starch molecules in solution. Four different starches from different botanical sources were studied. By comparing the measured stiffness to the composition of the starch, the effects of the various components on the stiffness were determined. This study is part of a program to develop a starch database essential to the design and processing of starch-based products.

Technical Abstract: The persistence lengths for four starches with different amylopectin/amylose compositions were estimated from intrinsic viscosity measurements. The intrinsic viscosities of the starches were measured at 25 deg C using 90/10 DMSO/water (weight/weight) as the solvent. The calculations were conducted using the equations developed by Yamakawa and Yoshizaki and corrected for polydispersity using the Schultz-Flory distribution. Values for the persistence lengths were 5.6 +/ 0.7, 5.4 +/ 0.6, 15 +/ 1, and 11 +/ 1 nm for waxy maize, normal maize, high amylose potato, and high amylose maize starches, respectively. The low values for normal maize and waxy maize were within experimental error. The higher values obtained for the high amylose potato and maize starches reflect the increased stiffness of the amylose chains in DMSO which could be due to helical confirmation of amylose in the solvent.