Changes in the Starch Fraction During Extrusion‐cooking of Corn

Abstract

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.