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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of Mid-Versus Near-Infrared Diffuse Reflectance Spectroscopy for the Determination of Protein in Ground Wheat Samples

Authors
item Reeves Iii, James
item Delwiche, Stephen

Submitted to: Eastern Analytical Symposium
Publication Type: Abstract Only
Publication Acceptance Date: November 18, 1996
Publication Date: N/A

Technical Abstract: It is commonly believed that it is not possible to quantitatively determine the composition of cellulosic type samples (such as ground wheat) using mid-infrared spectra obtained on non-KBr diluted (neat) samples. The objective of this study was to determine if mid-infrared diffuse reflectance spectroscopy could be used in the same manner as near-infrared diffuse reflectance spectroscopy (NIRS) to quantitatively determine the protein content of ground wheat samples. One hundred and thirty hard red winter wheat samples were assayed for protein by combustion and scanned in the near-infrared and mid-infrared. Samples (UDY ground) were scanned neat in the near-infrared from 1100 nm (9091 cm-1) to 2498 nm (4003 cm-1) on a scanning monochromator and in the mid-infrared from 4000 cm-1 (2500 nm) to 400 cm-1 (25,000 nm) on a Fourier transform spectrometer at 4 and 16 cm-1 resolutions. Protein content varied from a low of 8.98% to a high of 18.70% (average of 12.86% with a SD of 1.66%). Calibrations developed using PLS gave R2 and RMSD of 0.997 and 0.098 for the near- infrared (Data from 1108 to 2492 nm used) and 0.981 and 0.227 for the mid-infrared (Entire spectra used at 4 cm-1 resolution). Calibration results based on mid-infrared spectra, while not as good as those using near-infrared spectra, were nevertheless quite good. These results demonstrate that it is possible to develop satisfactory calibrations for protein in ground wheat using mid-infrared spectra without the need for sample dilution with KBr.

Last Modified: 8/31/2014