Changes in the Starch Fraction During Extrusion-cooking of Corn

Authors

  • M.H. GOMEZ,

    1. Author Gomez is affiliated with the Food Protein Research & Development Center, Texas A&M Univ., College Station, TX 77843. Author Aguilera, formerly with Texas A&M Univ., is now with the Dept. of Chemical Engineering, Catholic Univ., Santiago, Chile.
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  • J.M. AGUILERA

    1. Author Gomez is affiliated with the Food Protein Research & Development Center, Texas A&M Univ., College Station, TX 77843. Author Aguilera, formerly with Texas A&M Univ., is now with the Dept. of Chemical Engineering, Catholic Univ., Santiago, Chile.
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  • Author Gomez acknowledges financial support from the Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina. Technical assistance of Mr. M. Kazemzadeh in the use of the light and scanning electron microscopes is deeply appreciated. This research was supported in part by the Center for Energy and Mineral Resources, Texas A&M University.

ABSTRACT

Whole ground corn was extruded at 23.7, 18.5, 15.4,13.9 and 7.6% moisture contents (EMC). Decreasing EMC resulted in increases in water solubility index (WSI), enzyme susceptibility (ES), degree of gelatinization and blue values, while water absorption index and water insoluble carbohydrates decreased. ES and WSI of several blends prepared by combining raw (R), gelatinized (G), and dextrinized (D) corn were compared to those of extruded products. Corn extrudates had properties similar to blends containing G and D corn only. The relative proportion of D corn increased from about 10 to 60%, as EMC decreased. “Dextrinization” appears to become the predominant mechanism of starch degradation during low-moisture, high-shear extrusion. Viscoamylographs, scanning electron and light photomicrographs support these findings.

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