Study of octenyl succinic anhydride-modified waxy maize starch by nuclear magnetic resonance spectroscopy

Granular waxy maize starch was reacted with two levels (3 and 15% based on the weight of starch) of octenyl succinic anhydride (OSA) Structure of the OSA and modified starches was studied by one-dimensional (1D) H-1 and C-13 and two-dimensional (20) homonuclear correlation and heteronuclear correlation nuclear magnetic resonance (NMR) spectroscopy The modified starches were converted to a-limit dextrins prior to NMR analysis By applying the 1D and 2D NMR techniques complete assignments of H-1 and C-13 NMR spectra of the OSA reagent were achieved and the position of the double bond and ratio of trans to cis isomers were determined As level of OSA substitution increased the peak (approximate to 5 38 ppm) for the anomeric proton of internal alpha-14-D-glucosyl units became broader in H-1 NMR spectra suggesting that substitution occurred at the O-2 position Compared with the C-13 NMR spectrum of the native starch the modified starches gave additional signals at the C-4 peak region and broadening of the C-1 C-2 C-3 and C-4 resonances but not of the C-6 signal Those results further suggest that the OS groups were substituted at the O-2 and O-3 positions but not at the O-6 position (C) 2010 Elsevier Ltd All rights reserved