Preparation and Physicochemical Properties of Glutaric Acid Waxy Corn Starch Ester
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Abstract:
Native waxy corn starch was used as the raw material to prepare glutaric acid starch ester (EGAS), with glutaric anhydride (GA) as the esterifying agent and ethanol as the solvent. The structural characteristics and physicochemical properties of the samples were determined by Fourier transform infrared (FT-IR) spectroscopy), Brabender viscoamylography, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results indicated that two new absorption peaks of EGAS appeared at 1730 cm-1 and 1565 cm-1, which were attributed to the stretching vibration of C=O and antisymmetric stretching vibration of free -COO-, respectively. The findings above indicated that the ester carbonyl group was successfully introduced into starch molecules. Changes in the surface morphology of starch granules before and after modification demonstrated that the reaction occurred not only on the surface of starch granules, but also within the granules. XRD revealed that the modified starch still exhibited an A-type diffraction pattern, confirming that the reaction mainly occurred in the amorphous region. Brabender viscoamylography indicated that the peak viscosity of the modified starch (degree of substitution [DS]=0.0450) was increased by 2.33 times compared with that of native starch. The freeze-thaw stability and shear force of EGAS were higher than those of native starch, and paste transparency was improved.
