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 NDSAʹs. 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.