Preparation of Glutaric Acid Starch Ester by Aqueous-phase Method and Its Physicochemical Properties
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Abstract:
Glutaric acid starch ester was prepared from native corn starch by aqueous-phase method, using glutaric anhydride (GA) as the esterifying agent, and distilled water as the reaction solvent. The effects of initial starch slurry concentration, reaction time, reaction temperature, pH value and the amount of glutaric anhydride on the degree of substitution (DS) during the preparation were also investigated. Optimum reaction conditions for GA starch preparation, obtained by single-factor and orthogonal testing were as follows: starch slurry concentration 40% (m/m), reaction time 2 h,reaction temperature 35 ℃ and pH 8.5. The structures of native corn starch and GA starch were characterized and analyzed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). FTIR results showed that two new absorption peaks appeared at 1733 cm-1 and 1555 cm-1, attributed to C=O stretching vibration and free -COO- antisymmetric stretching vibration, respectively, indicating that GA was successfully introduced into the starch molecules. The results of XRD analysis revealed that GA starch still showed a Type-A crystal structure, suggesting that the reaction occurred mainly in the amorphous region.
