1-Allyloxy-2-hydroxy-propyl-starch:: Synthesis and characterization

New reactive unsaturated starch derivatives, 1-allyloxy-2-hydroxy-propyl-starches (AHP-starches), were synthesized by the reaction of waxy maize starch (WMS) and amylose-enriched maize starch (AEMS) with allyl glycidyl ether in a heterogeneous alkaline suspension containing NaOH and Na2SO4. The degree of substitution (DS) was determined by H-1 NMR spectroscopy, and a DS of 0.20 +/- 0.01 was found for both AHP-WMS and AHP-AEMS, respectively. The AHP derivatives of WMS and AEMS were further characterized with H-1 and C-13 NMR. It was shown that the AHP substitution was located on the C-6 hydroxyl group of the glucose residues in the starch. The substitution pattern of the AHP groups along the polymer chain was randomly clustered, as determined by enzymatic digestion using pullulanase, a-amylase, and amyloglucosidase, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of the digestion products. With X-ray diffraction and scanning electron microscopy, no changes in the granular morphology and crystallinity between the unmodified starches and AHP-starches were detected. (c) 2007 Wiley Periodicals, Inc.