Physico-chemical characterization of starch ferulates of different degrees of substitution

Starch ferulates were prepared by reacting potato starch with ferulic acid chloride, using pyridine as a catalyst in dimethyl sulfoxide. Starch ferulates of different degrees of substitution (DS) were prepared and their formation was confirmed by the presence of the carbonyl signal around 1726 cm−1 in the FT-IR spectra. The thermal characteristics of the native starch and starch ferulates of different degrees of substitution were studied using TGA, DTG and DSC and the studies revealed the starch ferulates to be thermally more stable than the native starch. The starch esters exhibited 50% weight loss at temperatures from 332 to 375 °C while the native starch underwent 50% weight loss at 321 °C. The 1H and 13C NMR studies confirmed the structure of the modified starch. X-ray diffraction studies revealed the loss of the ordered B-type crystalline structure, characteristic of potato starch. The microstructural imaging of the starch esters exhibited a networking which was enhanced with increasing degree of substitution. The starch ferulates also exhibited DPPH radical and ABTS radical cation-scavenging activity.