Discolouration of Sawn Birch (Betula pendula) Timber from Plantation Forests during Drying: The Role of Proanthocyanidins (condensed tannins) in Discolouration of Birch Wofed

摘要

In the previous paper on discolouration of sawn birch timber from plantation forests that had been published in Baltic Forestry, 2004 10 (2), the effect of external factors (growing site, felling season, log storage) was discussed. In this paper, therole of proanthocyanidins in discolouration during drying is investigated. Conventional warm-ah drying gave the highest concentration of proanthocyanidin in the wood. Storage of wood as logs increased the proanthocyanidin concentration in both fresh anddried wood. Proanthocyanidins obviously polymerised and oxidized to coloured compounds during drying, as the proanthocyanidin concentration was found to be lowest in the darkest reddish wood, The combination of drying temperature and prevailing moisturecontent of wood during the drying process seemed to be very important for formation of coloured phenolic compounds.