Octenyl succinic anhydride modified early indica rice starches differing in amylose content

Seven early indica rice starches with different amylose contents were modified by octenyl succinic anhydride (OSA) in aqueous suspension systems to evaluate the effect of amylose contents on starch esterification. The crystalline structure and pasting properties of starches were investigated using X-ray diffraction and a Rapid Visco Analyzer (RVA). The results indicated that the amylose content had a positive impact on the OSA modification. As the amylose content increased from 0 to 39.6%, the degree of substitution increased from 0.024 to 0.030 and the reaction efficiency increased from 62.8 to 77.5%. X-ray diffraction scans confirmed that the amylose was mainly present in the amorphous domain of the granule and was highly substituted after the OSA treatment. The RVA profiles demonstrated that the OSA starches had higher viscosities than their native counterparts. Moreover, negative correlations were observed between the amylose content and the major RVA parameters (e.g., peak viscosity, hot paste viscosity, cool paste viscosity, and breakdown viscosity).