Effects of the degree of substitution of octenyl succinic anhydride on the physicochemical characteristics of adlay starch

Impact of octenyl succinic anhydride (OSA) esterification on the structural, thermal, pasting, and emulsifying characteristics of adlay starch was investigated. The degree of substitution (DS) increased significantly from 0.008 to 0.025 with increasing OSA quantity, and the bands intensity at 1724 cm-1 and 1572 cm-1 in Fourier transform infrared spectroscopy increased with increasing DS. OSA modified starch showed unaltered orthorhombic diffraction pattern and morphological structure in native adlay starch, but gelatinization temperatures and enthalpy decreased significantly. Higher DS values lowered iodine binding capacity (from 1.37 to 0.77) and a shift in the maximum absorbance wavelength toward the shortwave direction was observed (from 530 nm to 510 nm). Significant increases were observed in peak, through, breakdown and final viscosities upon OSA esterification, while the pasting temperature decreased. Furthermore, contact angles increased significantly from 27.4° to 73.4° with increasing DS, and OSA-starch exhibited superior emulsion stability. Therefore, esterification with OSA effectively modified adlay starch to meet industrial demands and enhance its functional properties.