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United States Department of Agriculture

Agricultural Research Service

Title: Two Dimensional Vibration Spectroscopy V: Correlation of Mid and Near Infrared of Hard Red Winter and Spring Wheats

Authors
item Barton Ii, Franklin
item Himmelsbach, David
item Archibald, Douglas

Submitted to: Near Infrared Spectroscopy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 1997
Publication Date: N/A

Interpretive Summary: Spring wheat always brings a premium in the marketplace that is in excess of what one might expect for the small increase in protein content of spring over winter wheat. What is the difference between hard red spring and hard red winter wheat? Near infrared, mid infrared, Raman and 2 dimensional correlation spectroscopy was used to examine hard red winter (HRW) and hard red spring (HRS) wheat and ascertain the differences betwee them. The two dimensional spectroscopy technique developed in this laboratory was used to determine that the two classes of wheat were not only different in their amount of protein, but that the winter wheat protein contained more aromatic amino acids. This information enables breeders to know what characteristics are needed to improve quality and the wheat quality scientists to have new tools to assess quality.

Technical Abstract: Two dimensional correlation spectroscopy across the near infrared (NIR) and mid infrared (MIR) regions have been used to explain the NIR spectra of hard red winter and spring wheat; and provide additional confidence in analytical models developed with empirical data. Recent studies have shown that the major C-H stretching vibrations and some of the aromatic C-H and ring stretching vibrations and the minor vibrations in the "fingerprint" region also are correlated. The technique has been expanded to include Raman spectra. The Raman spectra were enhanced with Maximum Likelihood methods to improve signal-to-noise (S/N) while maintaining resolution. This was necessary to eliminate the effects of fluorescence which degrades S/N. The use of NIR lasers at 1.1 micron generally eliminates fluorescence as a problem, but it is still quite prevalent in agricultural materials. The original study did not show any significant correlations to aromatic functionality. However, the band at 1552 nm correlates to the Raman and not to the MIR. This band has shown up in NIRS models for the determination of lignin, but is not readily observed in MIR. Thus it correlates to a Raman active rather than a MIR active band. The same phenomena are observed for the amide I, II, and III bands for wheat. The interesting features from NIR and MIR are that there are correlations that distinguish winter from spring wheat. These and the Raman spectra of wheat will be shown. These studies show that multiple regions of the electromagnetic spectrum can be and indeed need to be used to adequately interpret the spectral and statistical results we have traditionally obtained in the NIR.

Last Modified: 10/21/2014
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