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Title: COMPOSITIONAL DIFFERENTIATION OF MAIZE HYBRID STOVERS USING ANALYTICAL PYROLYSIS AND HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Author
item GALLETTI, G. - CNR, ITALY
item Reeves Iii, James
item BOCCHINI, P. - CNR, ITALY
item MUSCORELLA, C. - CNR, ITALY

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Near infrared spectroscopy (NIRS) is a non-destructive method using light to determine the composition and quality of materials. It has been widely applied to agricultural products such as hays, but its application to materials with a high moisture content, such as silages (fermented grass), has shown that while it can be used, accuracy does not match that obtained with dry materials. The objective of this work was to determine how the presence of water affects spectra (graphical representation of how light interacts with the material in question) in part of this region (lower part of near-infrared) where the interaction of light with water is less. Since materials such as silages are very complex mixtures and subsequently difficult subjects to study, this study concentrated on simple mixtures of water and single, pure materials, such as alcohol. Examination of spectra showed the spectra of various compounds to be altered by water in ways previously seen in other spectral regions. However, it was found that while some materials may show the same spectral effects due to water in one spectral region (type of light used, i.e., red, green, invisible), they may or may not behave similarly in other regions. These and previous results indicate that the changes induced by water in the spectra of various materials are very complicated and would require extensive work to characterize as to origin in anything more than a superficial manner. They also show that the spectral region best suited to a particular application is likely to be found only by extensive testing.

Technical Abstract: The spectral region from 10,000 to 8000 cm-1 is often used for the analysis of high moisture systems and for fiber optic systems due to its low absorption by hydroxy groups. The objectives of this work were: 1. to determine the effects of water on the spectra of various types of materials, and 2. to determine the origin/nature of spectral effects/artifacts seen in the spectral region from 14,000 to 11,500 cm-1 when water was added to gums and proteins (increases in peak intensities and shifts in position do to the presence of water). Spectra were obtained by diffuse reflectance and transmission using a Fourier transform spectrometer for a variety of organic liquids, liquid/water solutions, solids, wet solids, etc. The results showed that the effects seen in other spectral regions (mid-infrared, and upper near-infrared were also common in the lower near-infrared (i.e., peak shifts, loss of spectral features, etc.). For example, in the other spectral regions, sugars, such as sucros and glucose, were distinctively different as crystalline solids, but very similar in solution. While the lower near-infrared spectra of crystalline glucose and sucrose lacked spectral features often seen in the other spectral ranges, the two sugars were distinctively different as crystalline solids, but very similar when in solution. Changes in the spectra of other materials, such as acetone, pyridine and ethanol were very similar in nature to those previously found in the near-infrared from 5000 to 4000 cm- 1 (2000 to 2500 nm). Finally, detailed examination of spectra in the region from 10,000 to 8000 or 6000 cm-1 did not show any spectral effects similar to those seen in gums and proteins in the 14,000 to 11,500 cm-1 region. Thus, the nature of these effects is thus still unknown.