Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 17, 1997
Publication Date: N/A
Technical Abstract: Extrusion cooking technologies are used to produce environmentally benign starch-based foam products. The impact of changes in a myriad of operational variables on performance must be quantified to enable the manufacture of economically competitive industrial packaging and other products. The molecular weight and expansion characteristics of starch-based foams are dependent on many twin-screw processing variables, including moisture and amylopectin content, temperature, screw speed, fill factor and die orifice diameter and L/D ratio. Foams made with 50% amylose starch had the highest volumetric expansion. Its intrinsic viscosity did not decrease during extrusion as much as corn or waxy maize starch, but exhibited the most shear-thinning, pseudoplastic behavior. Molecular weight degradation can be reduced by increasing moisture content or die orifice diameter and reducing die L/D or residence time. Extrusion conditions necessary for molecular weight preservation are usually unfavorable to those needed for expansion. With low residence time, molecular weight degradation of starch extruded under high shear and temperature conditions are minimized. High screw speeds and fill factors and low moisture content reduced residence time.