Physicochemical, Rheological Properties and Structure of Commercial Octenyl- Succinic Anhydride Modified Potato Starch

This study focuses on commercial potato starch modified by esterification with octenyl succinic anhydride (OSA) and investigates its physicochemical rheological properties and structure. The degree of substitution (DS) was found to be 0.012. The 1H-NMR analysis confirmed the structure of OSA-modified starch, revealing new absorption bands. The 13C-NMR spectra showed that octenyl succinic (OS) groups were mostly substituted at the O-2 and O-3 positions of glycosyl units. Scanning electron microscopy (SEM) showed that OSA potato starch had a compact structure with blade-like perforations and small grains of varying sizes. The zeta potential was -37 ± 8.06 mV, indicating good stability. Conductimetry and surface tension were used to determine the critical micellar concentration (CMC), which was found to be 0.04% (w/v). Dynamic light scattering showed an increase in size of OSA-modified potato starch granules, the average diameter ranged from 68.4 μm to 144.4 μm. Rheological properties of OSA potato starch at wide intervals of concentrations ranging from 0.01 to 10% (w/v) showed that viscosity was concentration-dependent. OSA potato starch was characterized as having a gel-like structure with a storage modulus (G') significantly higher than the loss modulus (G'') for all samples.