Spectroscopic monitoring of biomass modification by light-irradiation and heat treatment

This study discusses the use of near infrared spectroscopy for monitoring of the process by which biomass is modified by light-irradiation and heat treatment. As a change in the colour of wood is closely related to the change in its physicochemical structure, we investigated the relationship between the tristimulus values and the diffusely-reflected near infrared spectra of wood samples during a constrained modification process. Such basic research is required to develop a new method of colouring wood without paint. The change in colour with heat treatment was much greater in light-irradiated wood than in non-irradiated wood. The change in the colour of wood by light-irradiation and heat treatment is related to the degradation of lignin and hemicellulose, which was evident from the variation of absorption bands at 1672 nm for CH in aromatic skeletal and 1724 urn for CH in furanose or pyranose. NIR spectroscopy will become a useful method for the detection of a change in chemical structure of wood caused by light-irradiated and heat treatment.