Heat-Induced Color-Intensity Change in Coastal Douglas-Fir and White Spruce
Keywords:Pseudotsuga menziesii, Picea glauca, reflectance spectrophotometry, activation energy, kinetics, chromophore, dihydroquercetin
AbstractIn a previous study, it was found that to reach the same degree of surface inactivation, Douglas-fir attained a much higher heat-induced color intensity at 520 nm than white spruce. To explain the heat-induced color-intensity change as a function of the above species, the present study measured the thermally induced spectral changes in the visible wavelength region for these species. The differential reflectance spectra for the sapwood and heartwood of coastal Douglas-fir and white spruce showed a peak in the 410- to 430-nm region, but only coastal Douglas-fir showed a second peak at 550 nm. Comparison of rate data for extracted and unextracted coastal Douglas-fir showed that its extractives contributed significantly to the heat-induced color-intensity change. Dihydroquercetin, a major phenolic extractive in coastal Douglas-fir upon heating produced a powerful chromophore group.
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