Effect of pressurized hot water extraction on the resistance of Scots pine sapwood against mould fungi

Abstract

Abstract The effects of pressurized hot water extraction (HWE) treatment on the mould resistance of wood have not been extensively investigated yet. The activity of the mould fungi is dependent on the availability of nutrients. Therefore, the soluble degradation products produced during HWE treatment could affect the wood’s susceptibility to mould growth. Scots pine (Pinus sylvestris L.) sapwood specimens were treated with HWE at 140 °C for 1–5 h. Afterwards, the degradation products were either removed via leaching or the wood was dried without applying the leaching procedure. The surface layer (1.5 mm) was removed from half of the leached and non-leached specimens. The resistance of the specimens against mould growth was tested in an incubation chamber. HWE treated wood showed a higher susceptibility to mould growth when it was neither leached nor subjected to surface removal. The susceptibility of wood to mould fungi depended on the availability of hemicellulose-based degradation products produced during HWE treatment. These degradation products were removable via a leaching procedure, but also by removing the outermost layer of the wood. The results show the relevance of removing HWE degradation products located on the wood surface in improving resistance against mould growth.