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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Processing Conditions on Intrinsic Viscosity of Extruded Cornstarch

Author
item Cunningham, Raymond

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 1996
Publication Date: N/A

Interpretive Summary: Additional information is needed about the breakdown of starch in a twin- screw extruder when conditions are varied. This study aids in determining the optimal operating conditions for the reactive extrusion of corn products. Not only food products but many nonfood materials can be prepared in an extruder. The physical effects on cornstarch extruded under rconditions relating to the thickness of the starch slurry, speed of extruder screw, and temperature are evaluated. The sizes of the starch particles in the extruded materials are compared with the size of the untreated cornstarch. All samples treated at the lowest consistency (35%) retained two-thirds of their original physical integrity. In this study, the most favorable temperature for treatment was 100 deg C with a screw speed of 200 or 300 rpm. The acquired information allows for the selection of conditions in the extruder to modify yet protect the physical integrity of the structure of cornstarch.

Technical Abstract: Unmodified cornstarch from dent corn was used in this study to determine the effect of twin-screw extrusion conditions on the intrinsic viscosity of this polysaccharide and water. The study focused on the intrinsic viscosity of the cornstarch as a function of the key variables and as a relative indicator of the molecular weight of the starch. Primary variables examined were temperature (75, 100, and 125 deg C), starch concentration or consistency (35, 50, and 65%), and screw speed (100, 200, and 300 rpm) during the extrusion processing. The most favorable conditions examined were the extrusion of the cornstarch at 35% consistency, 100 deg C, and 200 rpm. Two-thirds of the original intrinsic viscosity of the unmodified starch was retained upon extrusion at 35% consistency at all temperatures and the screw speeds (200 and 300 rpm) examined. Also, similar values were observed at 50% consistency for 75 deg C at 100 and 200 rpm and for 100 deg C at all three screw speeds.

Last Modified: 7/22/2014
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