Physical and Molecular Properties of Starch Acetates Extruded with Water and Ethanol

Abstract

Starch acetate with degrees of substitution of 2 and 3 was extruded with either water or ethanol in a single screw extruder. Properties of the extrudates such as unit and solid density, specific mechanical energy, water absorption and water solubility indices, and molecular degradation and degree of substitution (DS) of the starch were measured. The samples extruded with water had lower spring indices, lower water absorption, and higher solid density than acetylated starch extruded with ethanol. The samples with DS of 2 required less specific mechanical energy and had higher solid density and water absorption indices than starch with DS of 3. Both independent variables influenced unit density and water solubility indices. A slight decrease in the average molecular weight was registered as a result of the extrusion processing.