Digestibility, physicochemical and structural properties of octenyl succinic anhydride-modified cassava starches with different degree of substitution.

The octenylsuccinylated cassava starch (OSCS) samples with a degree of substitution (DS) in the range of 0.008 to 0.035 were prepared in this study. The structural, physicochemical, and in vitro digestibility properties of OS-starch samples were investigated. Intensities of characteristic peaks at 1724cm-1 and 1572cm-1 increased with increasing DS, which confirmed successful introduction of ester carbonyl groups into starch molecules. The esterification occurred primarily in the amorphous regions and surface of starch granule, and the crystalline pattern did not change. SEM results revealed that the modification had slight effects on the morphological structure of native starch. Differential scanning calorimetry (DSC) thermograms of OS-starch samples showed lower onset temperature, peak temperature, conclusion temperature, and endothermic energy than their native counterpart. This study also showed that esterification with OSA was an effective method for increasing slowly digestible starch and resistant starch contents in starch samples.