Abstract: Cassava starch was modified with epichlorohydrin (ECH) and octenyl succinic anhydride (OSA) by a semi-dry process to synthesize hydrophobic lipophilic crosslinked octenyl succinic anhydride-modified starch (COSAS). The synthesis process was optimized by one-factor-at-a-time and orthogonal array design methods. The reaction mechanisms were elucidated. The whiteness of COSAS was determined and structural analysis was carried out using Fourier transform infrared spectrometry and scanning electron microscope (SEM). The results indicates that the optimal synthesis process parameters of COSAS were starch water content of 15%－18%, OSA amount of 3% (based on the dry weight of starch), esterification time of 90 min, pH 9.0, and reaction temperature of 100 ℃. The average degree of substitution (DS) of COSAS prepared using the optimized process parameters was 0.0175, and its whiteness was slightly lower than that of native starch. FTIR spectral analysis revealed that crosslinked bonds and groups in octenylsuccinate were introduced into starch after esterification. SEM observations also showed that the surface of COSAS was rougher than that of native starch although some particles with concaves, gaps and cracks were observed.

Key words: cassava starch, crosslinked octenyl succinic anhydride-modified starch, semi-dry process, reaction mechanism