Ultrasound effects on the acetylation of dioscorea starch isolated from Dioscorea zingiberensis C.H. Wright

The objective of current work is to investigate the intensification of starch towards acetylation by acetic anhydride after ultrasound treatment. Native dioscorea starch (NDS) slurry was ultrasonically treated to produce ultrasound-treated dioscorea starch (UTDS). The effects of ultrasound-treated conditions of NDS on degree of substitution (DS) of ultrasound-treated dioscorea starch acetate (UTDSA) were examined. The influences of different acetylation conditions such as reaction time, reaction temperature and the molar ratios of H2SO4 to starch on the DS of starch acetate (SA) were also investigated by comparing the DS of UTDSA with NDSA's. The results demonstrate that a higher DS value is always observed for the acetylation of UTDS sample under the same reaction conditions. Moreover, using UTDS or NDS as material, the SAs with same DS value (0.55 and 1.75) were synthesized, and their chemical structure, crystalline structure, thermal stability, and morphological properties were characterized by the Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques.

Dioscorea starches were treated by ultrasound, a significant change in starch granule morphology, and the holes or channels were formed both on the surface and inside the granules of starch after ultrasound treatment. As a result, the surface area of starch particles is increased, which may result in an increase in the reaction efficiency. The application of ultrasound-treated dioscorea starch was found to have a positive effect on acetylation with reduced reaction time and temperature, but higher DS value.Figure optionsDownload as PowerPoint slideHighlights
► The native dioscorea starch slurry treated by ultrasound.
► The ultrasound-treated dioscorea starch was obtained.
► The holes or channels were formed on the surface of starch granules after ultrasonic treatment.
► The acetylation efficiency of starch was increased.