Carbon-13 nuclear magnetic resonance studies of chemically modified waxy maize starch, corn syrups, and maltodextrins. Comparisons with potato starch and potato maltodextrins
1991
Mora-Gutierrez, A. | Baianu, I.C.
Comparative studies of corn syrups, maltodextrins, chemically modified waxy maize starch, and corn starch were carried out by carbon-13 NMR techniques. Spectral assignments were made for all materials studied and were checked against independent assignments by proton-carbon correlation spectroscopy. Degrees of branching and polymerization were estimated for maltodextrins from corn starch and were compared with those of potato maltodextrins in relation to the observed difference in the gelling behavior and functionality of corn and potato maltodextrins, respectively. Chemical shifts were found to be similar among maltodextrins from corn and potato, as well as wheat amylopectin and amylopectin B. A comparison of solid-state 13C NMR spectra of corn, wheat, and potato starches reveals their polymorphism, terms of the number of glucose rings in the "unit cell" of the amylopectin crystalline regions of starch granules. Gelatinization causes changes in the symmetry of the crystalline regions of amylopectins inside waxy maize starch granules and/or increased mobility of branches in such regions. A broad band in the anomeric region of the solid-state 13C NMR spectra of waxy maize starch is assigned to the disordered regions of amylopectin in the starch granule structure. Carbon-13 NMR is shown to be a valuable, noninvasive tool for comparative, structural studies of corn starches and products derived from starch. Structural details were obtained that are relevant to gelatinization and gelling mechanisms. For corn maltodextrins structural details were obtained concerning the degrees of branching and polymerization, as well as the anomers; such details were compared between corn and potato starch maltodextrins and found to be significantly different.
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