Distribution of octenylsuccinic groups in modified waxy maize starch: An analysis at granular level

Abstract This study aimed to report the distribution of octenylsuccinic (OS) groups in waxy maize starch granules. A series of octenylsuccinic anhydride (OSA) substituted starch with degree of substitution (DS) ranging from 0.018 to 0.068 were prepared. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed an integrated granular structure of OSA starch were maintained, and the crystal regions, likewise, were not modified. Fourier transform infrared spectroscopy (FTIR) results suggested that OS groups could be grafted on surface of starch granules. However, Confocal 2D Raman microscopy confirmed that OS groups are located unevenly throughout the starch granule, with an increased intensity in the center. A refined lamellar model was proposed, which indicated that OS groups occurred on each layer of amorphous regions, and further modified the center of the cavity, probably due to the OSA reagent accessibility to hilum by the presence of a large number of channels in each granule.