Chemical and Anatomical Characterization of Discoloration in Beach (Fagus orientalis L.) Veneer During Kiln Drying and Aging

Discoloration of wood due to biotic and abiotic factors or combination of both deteriorates the quality of wood، increases production costs and also decreases the quality of end-products. In this study، anatomical variations and topochemical distribution of lignin and extractives before and after drying and aging were investigated using the UMSP method. Chemical analysis was carried out using HPLC method. Results showed that increasing drying temperature up to 180 °C and increasing aging duration up to 6 months، increased extractives amount in vessel lumen and parenchyma cells and as well as lignin concentration in cell wall layers. A direct relationship between intensity of visual discoloration and the amount of UV absorption by extractives could be observed. It means that the higher the visual discoloration، the higher the absorption at 280 nm wavelength. HPLC analysis revealed that with increasing drying temperature and aging duration، higher and clearer discolorations in beach wood texture could be observed. Acetone and methanol extracts of discolored wood showed the presence of different low molecular compounds such as catechin and 2، 6 dimethoxy benzoquinon، which are transformed to high condensation compounds during kiln-drying and aging.