Distribution of low-molecular lipophilic extractives beneath the surface of air- and kiln-dried Scots pine sapwood boards

PLoS One. 2018 Oct 10;13(10):e0204212. doi: 10.1371/journal.pone.0204212. eCollection 2018.

Abstract

During industrial wood drying, extractives migrate towards the wood surfaces and make the material more susceptible to photo/biodegradation. The present work provides information about the distribution, quantity and nature of lipophilic substances beneath the surface in air- and kiln-dried Scots pine (Pinus sylvestris L.) sapwood boards. Samples were taken from knot-free sapwood surfaces and the composition of lipophilic extractives, phenols and low-molecular fatty/resin acids layers at different nominal depths below the surface was studied gravimetrically, by UV-spectrometry and by gas chromatography-mass spectrometry (GC-MS). The concentration of total extractives was significantly higher in kiln-dried than in air-dried samples and was higher close to the surface than in the layers beneath. The scatter in the values for the lipophilic extractives was high in both drying types, being highest for linoleic acid and slightly lower for palmitic, oleic and stearic acids. The amount of fatty acids was low in kiln-dried boards, probably due to a stronger degradation due to the high temperature employed. The most abundant resin acid was dehydroabietic acid followed by pimaric, isopimaric, and abietic acids in both drying types. It is concluded that during kiln-drying a migration front is created at a depth of 0.25 mm with a thickness of about 0.5 mm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Gas Chromatography-Mass Spectrometry
  • Industry
  • Linoleic Acid / analysis
  • Lipids / analysis*
  • Oleic Acids / analysis
  • Palmitic Acids / analysis
  • Pinus sylvestris / chemistry*
  • Plant Extracts / analysis
  • Wood / analysis*

Substances

  • Lipids
  • Oleic Acids
  • Palmitic Acids
  • Plant Extracts
  • Linoleic Acid

Grant support

This work received support from the Swedish Research Council for the Environment, Agricultural Sciences and Spatial Planning (FORMAS) project “Experimental studies of capillary phenomena in bio-based materials” 942-2016-64, “Fungal growth on modified wood-based products under subarctic conditions” 2017-00419, PI-Dr. Olov Karlsson; COST Action FP1407 “ModWoodLife” project “Understanding wood modification through an integrated scientific and environmental impact approach” PI-Prof. Dick Sandberg.