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United States Department of Agriculture

Agricultural Research Service

Title: Thermomechanical Depolymerization of Dextran

Authors
item Cote, Gregory
item Willett, Julious

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 1998
Publication Date: N/A

Interpretive Summary: New and/or expanded markets for sugar are needed. Dextran is a gum produced from cane or beet sugar that is used in a variety of industrial and biomedical applications. Many of these require a dextran of smaller size (lower molecular weight) than what is naturally produced. Typically, dextran manufacturers accomplish this by degrading the dextran with acid and purifying the correctly-sized dextran from the resulting mixture. We compare in this paper three different mechanical processes for the production of low-molecular weight dextran. Treatment with ultrasound gave the best product, but is presently too expensive for industrial-scale production. Extrusion is probably the cheapest process, but the product has some drawbacks. Jet cooking with high-pressure steam shows promise for producing clean low-molecular weight dextran, and may be useful for the conversion of other gums as well. This will allow for the manufacture of cheaper low-molecular weight gum fractions, opening up new markets for these sugar-derived products. Sugar farmers and processors, American agribusiness (dextran manufacturers), and the consumer should ultimately benefit.

Technical Abstract: Native, high-molecular weight dextran was subjected to ultrasonication at 20kHz and 1.5 MHz, jet-cooking with high pressure steam and twin- screw extrusion under a variety of conditions. All methods reduced the molecular weight and solution viscosity of dextran. The greatest degree of depolymerization occurred with 20 kHz ultrasonication. With extrusion, increasing amounts of specific mechanical energy input resulted in greater degrees of depolymerization. Each of these methods has advantages and drawbacks for the production of reduced-molecular weight dextrans.

Last Modified: 8/27/2014
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