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Modification of starch by extrusion and extrusion of modified starches
Abstract
Modified starches find specialty uses in both food and industrial applications. In this study, starch esters were synthesized by extruding 70% amylose starch with fatty acid anhydrides and sodium hydroxide (catalyst) in a single screw extruder. Acetic, propionic, heptanoic, and palmitic anhydrides were used at 0.01, 0.02, and 0.03 mol levels to obtain different degrees of substitution (DS) in the starch. Physical properties of the extrudates such as unit and solid density, specific mechanical energy, water absorption and water solubility indices, as well as molecular degradation and DS of the starch, were measured. DS increased as the level of anhydride increased. Lower molecular weights and higher levels of anhydride resulted in the greatest reduction in starch molecular weight. Modified starches also were produced in a batch process and then extruded. Starch acetate with degrees of substitution of 2 and 3 were extruded with either water or ethanol in a single screw extruder. Starch acetate with degree of substitution of 3 was extruded with either 16 or 18% (db) ethanol in a single screw extruder at 120 and 160°C. Physical properties of the extrudates such as unit and solid density, specific mechanical energy, water absorption and water solubility indices, as well as molecular degradation and degree of substitution (DS) of the starch, were measured. It was established that samples extruded with organic solvent such as ethanol, and at higher temperatures, had mechanical properties closer to commercial foam materials than samples extruded with water and samples extruded at lower temperatures. In the ranges studied, the DS and the alcohol content had limited effects on the properties of greater interest such as molecular degradation, water solubility, spring index and compressibility.
Subject Area
Food science
Recommended Citation
Miladinov, Vesselin Danailov, "Modification of starch by extrusion and extrusion of modified starches" (1998). ETD collection for University of Nebraska-Lincoln. AAI9917848.
https://digitalcommons.unl.edu/dissertations/AAI9917848