Submitted to: Eastern Analytical Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2005
Publication Date: 11/1/2005
Citation: Himmelsbach, D.S. 2005. Determination of branching ratios in starch of intact flours by gel-state 1H MAS NMR spectroscopy [abstract]. Eastern Analytical Symposium. Paper No. 498 p. 62.
Technical Abstract: 1H MAS NMR was employed to determine the ratio of alpha 1-4 to alpha 1-6 branching in the starch of rice flour. Samples investigated were exchanged (2X) in D2O with freeze drying, gelatinized with 90/10 percent DMSO/ D2O freeze dried again, finally moistened with D2O, and placed in a spherical 4 mm MAS rotor inserts. Data was collected employing a 4 mm CP/MAS probe, adapted with a deuterium lock channel, at 300 MHz under MAS (5 kHz) rotation at 353 deg K. The use of gel-state rather than solution-state experiment allows for improvement in S/N while retaining the resolution advantage over the actual solid-state experiment. Integration of signals at 5.4 and 5.0 ppm provided data consistent with amylose iodine affinity determinations. The method provides a primary method by which to chemometrically calibrate more rapid vibrational spectroscopic methods. The method is shown to be viable for both low or waxy (0-1 percent) and high (30 percent) amylose content rice flours. This technique negates the need to isolate rice starch from its natural matrix and the requirement to solubilize it for this determination.