Cereal Chem 67:529-532   |  VIEW ARTICLE

Effects of Single-Screw Extrusion Cooking on Starch as Measured by Aqueous High- Performance Size-Exclusion Chromatography.

D. S. Jackson, M. H. Gomez, R. D. Waniska, and L. W. Rooney. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

The water solubilization and apparent molecular weights of starch polymers from extruded corn starch and extruded decorticated sorghum flours were characterized by aqueous high-performance size-exclusion chromatography (HPSEC). Corn starch (25% amylose) was extruded at moisture contents ranging from 11.3 to 32.2%. Decorticated sorghum flours (12, 22, and 27% amylose) were extruded at 18, 32, and 45% moisture. In preparation for HPSEC analysis, extruded corn starch was solubilized in water for 10 min at 35 C. Extruded decorticated sorghums were also treated at 35 C, or boiled 10 min and autoclaved 10 min to solubilize starch. Although no dextrinization of the corn starches was evident, the HPSEC-determined water solubility increased with decreasing extrusion moisture. Decreased water solubility of corn starch, however, was caused by extrusion below 14% moisture content. Water solubility of starch in sorghum extrudates generally decreased as the amylose content increased. Two populations of amylopectin from sorghum were detected by HPSEC analysis. Because raw and extruded sorghum flours still exhibited differences in starch solubility even after both samples were autoclaved in excess water, extrusion cooking modifies starch polymers differently than cooking in excess water.