Effects of hydrothermal-alkali and freezing-thawing pre-treatments on modification of corn starch with octenyl succinic anhydride

Pre-treatments by freezing/thawing (F/T) and hydrothermal-alkali (HA) were used in the modification of starch with octenyl succinic anhydride (OSA). In comparison with OSA-modified starch prepared without pre-treatment (degree of substitution, DS = 0.0172; reaction efficiency, RE = 73.9%), HA pre-treatment increased the DS of OSA-starch and RE of subsequent OSA modification (0.0185 and 79.7%, respectively). In contrast, F/T pre-treatment gave the opposite results (0.0152 and 65.5%, respectively). OSA modification markedly increased the viscosities but decreased the gelatinization parameters of native starch. Esterification of starch by OSA was confirmed with Fourier transform infrared and Raman spectroscopy, which indicated markedly decreased short-range molecular orders of native starch. The present study showed that HA pre-treatment before OSA modification is an efficient way to improve the reaction efficiency of OSA with starch and thereby to modify the pasting properties of starch. F/T pre-treatment did not increase the reaction efficiency of starch with OSA.