Effect of acetylation treatment on surface modified tapioca starches

Abstract

Surface modified tapioca starch was developed by enzyme treatment (using STARGEN™ 002 enzyme) and alcohol-enzyme treatment. The effects of acetylation treatment on surface modified tapioca starches were evaluated for acetyl content (Ac%), degree of substitution (DS), morphology using scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FTIR), thermal properties, and X-ray diffraction (XRD) patterns. After acetylation treatment, Ac% and DS value of the samples were significantly increased for acetylated (0.67% and 0.03), enzyme-acetylated (1.13% and 0.04), and alcohol-enzyme acetylated (1.76% and 0.07). The acetylation treatment led to the formation of a few starch granules due to the introduction of hydrophilic groups of acetyl molecules into starch granules. The incorporation of acetyl groups into starch molecules also was shown at peak 1750 cm-1, 1369 cm-1, and 1230 cm-1 in the FTIR spectra. The enzyme-acetylated and alcohol-enzyme acetylated starch granules retained the A-type crystalline structure with decreased in the gelatinization enthalpy (ΔH) after acetylation.