IR analyses of lignin in Norway spruce (Picea abies [L.] Karst.)

The purpose of the study is to investigate the variation of the amount and polymer structure of lignin in Norway spruce clones and in individual trees in natural stands. Degradation of the lignocellulose complex in wood was studied by using a white-rot fungus (Coriolus versicolor) which is able to degrade all cell wall components including lignin; and brown-rot fungus (Poria placenta) which breaks down polysaccharides but by which lignin degradation is limited. The amount of lignin was analysed by micro-Klason and the samples were further used in the calibration of FTIR and NIR analyses. A baseline shift in IR spectra during the time of exposure to Poria placenta could be clearly observed. The association between a Fourier transformed mid infrared spectrum and the amount of lignin in a sample was modelled by principal component regression (PCR). In this method, the spectral information is encapsulated in a small number of principal components, which are then used as the explanatory variables in a linear model with the amount of lignin as the response variable. Preliminary results suggest that it is possible to come up with very accurate models with good prediction capability.