Characterization of water-soluble extracts from hot-pressed poplarBestimmung der wasserlöslichen Extrakte von heißgepresstem Pappelholz

Thermal modification of wood constituents occurs upon hot-pressing of flakes during consolidation of oriented strand board (OSB). Hence, the effects of hot-pressing of hybrid poplar on water-soluble extractives were studied. Poplar veneers were pre-conditioned to 0 or 8 % moisture content and subsequently hot-pressed at 150, 200 or 250 °C. Aqueous extracts were characterized by conventional chemical methods in conjunction with chromatography (HPLC and SEC), mass spectrometry (ESI–MS) and spectroscopy (FTIR) analysis. Water-soluble fractions were markedly influenced by thermal compression treatment at 250 °C compared to the lower temperatures. Chromatographic results indicate that water-soluble extractives content increases with temperature while the degree of polymerization decreases with detection at low temperature levels. FTIR spectroscopic analysis indicates changes in aqueous-extracts composition of wood monosaccharides (hemicelluloses), meanwhile ESI–MS detected xylo-oligosaccharides. These results clearly show that heat treatment dictated the changes in each water-soluble extractive component and they respond independently with different treatment.