Cereal Chem 54:256 - 265. | VIEW
Near Infrared Diffuse Reflectance Spectra of Wheat and Wheat Components.
D. P. Law and R. Tkachuk. Copyright 1977 by the American Association of Cereal Chemists, Inc.
Near infrared diffuse reflectance spectra between 1.0 and 2.5 microns were recorded for wheat, gluten, starch, pentosans, lipid, and water. The spectral absorption bands were assigned to various overtone and combination vibrations of C-H, N-H, O-H, and C=O bonds. The spectrum for wheat was determined largely by the carbohydrate components. The type of wheat had no effect on the position of reflectance peaks. Major peaks in the gluten spectrum occurred at 1.19, 1.50, 1.73, 1.98, 2.05, 2.18, 2.29, and 2.47 microns. The absorption peak at 1.98 microns is characteristic of gluten and is due to the high concentration of primary amide groups in gluten. The spectra for starch and pentosans were similar, with major peaks at 1.20, 1.45, 1.54, 1.93, 2.09, 2.32, and 2.49 microns. The position of peaks associated with hydroxyl groups was determined, in part, by the degree of hydrogen bonding. The lipid spectrum was characterized by intense absorption due to CH2 groups. Bands at 1.17, 2.14, and 2.17 microns were due to the C-H vibrations associated with cis double bonds, while absorption at 1.41 and 2.07 microns was due to OH groups. Liquid water had absorption peaks at 1.445 and 1.928 microns, while water in undried wheat, gluten, starch, and pentosan samples exhibited absorption at slightly longer wavelengths. This was probably due to hydrogen bonding.