Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2008
Publication Date: September 1, 2008
Citation: Glenn, G.M., Klamczynski, A., Chiou, B., Orts, W.J., Imam, S.H., Wood, D.F. 2008. Temperature Related Structural Changes in Wheat and Corn Starch Granules and Their Effects on Gels and Dry Foam. Starch/Starke. 60(9):476-484. Interpretive Summary: Starch can be processed into microcellular foam with useful commercial properties. However, there have been very few studies on the effect of starch processing on the properties of microcellular foam. This study showed that the heating regime used to prepare the foams does affect it properties. Using a well controlled cooking protocol will improve the ability to make microcellular foam with consistent properties.
Technical Abstract: The effect of processing temperature on structural changes in wheat, corn, and high amylose corn starch granules was investigated and related to the mechanical properties of gels and microcellular foam (MCF). Scanning electron micrographs (SEM) showed that wheat starch granules form ghosts with thicker walls than Dent corn granules. The granule wall was permeable to water and appeared to be at least partially permeable to the solubilized contents of the granule. The ghost walls became visibly porous after heating at 95ºC for 60 min and were completely solubilized by heating to 120ºC. High amylose corn starch (HACS) granules were completely dissolved by heating to 140ºC. Gels made with wheat starch had higher gel strength and dynamic modulus compared to Dent corn starch gels. The density, compressive strength and modulus of MCF were lower in samples cooked for 60 min. The density of Dent corn MCF was higher than that of wheat starch which may have accounted for higher compressive strength and modulus in the corn sample. MCF made from HACS had higher surface area and lower density, compressive strength, and modulus than the other starches tested. There were no significant differences in pore volume or surface area due to extended cooking times.