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Title: TWO-DIMENSIONAL FT-RAMAN CORRELATION SPECTROSCOPY DETERMINATION OF THE GLYCOSIDIC LINKAGES IN AMYLOSE AND AMYLOPECTIN

Author
item LIU, YONGLIANG - UNIV OF GEORGIA
item HIMMELSBACH, DAVID
item BARTON II, FRANKLIN

Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2004
Publication Date: 6/1/2004
Citation: Liu, Y., Himmelsbach, D.S., Barton Ii, F.E. 2004. Two-dimensional ft-raman correlation spectroscopy determination of the glycosidic linkages in amylose and amylopectin. Journal of Applied Spectroscopy. 58 (6): 745-749.

Interpretive Summary: Amylose and amylopectin are two major carbohydrates in cereal and cereal food products. Both of these polysaccharides have complex conformations that affect their physical, chemical, and biological activities. One of the greatest challenges in the cereal industry is to obtain accurate information about amylose component at many stages along the production process, ultimately providing the quality guaranteed cereal products for the consumers. Existing chemical analysis in cereal quality assessment can provide reliable chemical content information, however, it is destructive, time consuming, and environmentally unfriendly. The development of fast, non-destructive, accurate, and on-line / at-line techniques is desired. Vibrational spectroscopy, including near-infrared (NIR), mid-infrared (IR) and Raman, could form the basis for such technique due to its speed, ease of use and indicative of structural determination. In addition, the use of Fourier transform (FT) method and an NIR excitation laser provides precise wavenumber measurement and good-quality Raman spectra by reducing the interference from the fluorescence and photodecomposition. The present results demonstrated the usefulness of two-dimensional (2D) FT-Raman correlation spectroscopy in determining the glycosidic linkages in amylose and amylopectin, which is not readily obtainable from conventional one-dimensional spectra. It suggested that the 954 and 938 cm-1 Raman bands be assigned to symmetric C-O-C stretching modes involving the alpha-D-(1-->4)-linkages and alpha-D-(1-->6)-linkages in amylose and amylopectin, respectively. Researchers working on IR/Raman spectroscopy, food and cereal products as well as model developments will benefit from the findings of this research.

Technical Abstract: Generalized two-dimensional (2D) correlation analysis of amylose-dependent FT-Raman spectra (980 - 820 cm-1) was performed to determine the glycosidic linkages in amylose and amylopectin. Synchronous 2D Raman spectrum revealed that there are at least one band at 954 cm-1,whose intensity increasing, and two bands around 938 and 850 cm-1, whose intensity decreasing, with the amylose amount. The corresponding asynchronous spectrum indicated that that the spectral intensity reduction of the 938 and 850 cm-1 bands occurs before the intensity increase of the 954 cm-1 band. It suggested that that the 954 and 938 cm-1 bands be assigned to symmetric C-O-C stretching modes involving the a-D-(1-->4)-linkages and a-D-(1-->6)-linkages in amylose and amylopectin, respectively, while the 850 cm-1 band to symmetric C-O-C vibrations (ring breathing) in glucose unit. In addition, several close and separated bands appearing around 954 938, and 850 cm-1 wavenumber could be a result of changes in the molecular environment of C-O-C portions.