Nanostructure, morphology and functionality of cassava starch after pulsed electric fields assisted acetylation

Pulsed electric fields (PEF) assisted acetylation of cassava starch with a higher degree of substitution (DS) of 0.131 was obtained in the presence of 10% (w/w) acetic anhydride after PEF treatment at 2 kV/cm for 51.0 ms. Fourier-transformed infrared spectroscopy showed a characteristic peak of the acetyl group in modified starch at 1730 cm(-1). The crystalline region of acetylated starch was destroyed and rearranged as confirmed by X-ray diffraction. Small-angle X-ray scattering indicated that the fractal structure was changed from a surface fractal structure to a mass fractal structure with increasing DS probed. Atomic force microscopy showed that PEF assisted acetylation of starch markedly increased the surface roughness. The prominent freeze-thaw stability of PEF-assisted, acetylated starch demonstrated its potential and superior application in frozen food products. (C) 2015 Elsevier Ltd. All rights reserved.