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United States Department of Agriculture

Agricultural Research Service

Title: Light Scattering Molecular Weights and Intrinsic Viscosities of Processed Waxy Maize Starches in 90% Dmso-H2o

Authors
item Millard, Merle
item Dintzis, Frederick
item Willett, Julious
item Klavons, Jerome

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 1997
Publication Date: N/A

Interpretive Summary: Starch is a major component of foods and is used extensively in industry as a paper sizing agent and in the pharmaceutical industry as a binding agent. The way in which starches are prepared by cooking, or pasting, is important in obtaining desired properties of the cooked material. This work examined the effects of preparing waxy corn starch in different ways upon the molecular weight and intrinsic viscosity of the processed starch. By knowing how these two basic properties of starch molecules are affected by different treatments, industrial starch processors will be able to produce their starch containing products more efficiently and with improved properties.

Technical Abstract: Waxy maize starch was treated by a variety of gentle and severe methods: direct dispersion/solubilization into 90% DMSO-H2O solvent, extrusion followed by dispersion/solubilization of the ground exudate into solvent, or jet-cooking or stirred autoclaving of an aqueous starch slurry followed by transfer into solvent. Intrinsic viscosities and multi-angle light scattering measurements were made in 90% DMSO-H2O. A Mark-Houwink relation, [eta] = (0.28 to 1.2) Mw**0.29+/0.04, was obtained over a molecular weight range of about 30 to 700 million Daltons. However, there was a large amount of scatter in the data when intrinsic viscosities were greater than 140 mL/g. The following power law relationship: Rg alpha Mw**0.41+/0.04, was noted between radii of gyration and molecular weights. We infer from our data that over the entire range of molecular weight distributions the amylopectin existed in solution as relatively compact molecules/aggregates and that in the higher molecular weight region the size and possibly the shape of the "dissolved" amylopectin was highly sensitive to the method of dispersal and treatment.

Last Modified: 12/19/2014
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