Fig 1.
SEM micrographs of the cork surface (tangential section) of the reference cork and of cork after outdoor weathering and soil burial for 12 months, at 600X magnification (top row) and at 1500X magnification (bottom row).
Fig 2.
Photographs of the cork surface of the reference cork and of cork samples after 1-year outdoor weathering and soil burial.
Table 1.
CIELAB color parameters of the cork surface: In the reference cork and cork samples after 1-year outdoor weathering and soil burial.
Mean of six samples and standard deviation.
Fig 3.
FTIR-ATR spectra of the original cork surface and cork surfaces after outdoor weathering and soil burial with a spectral enlargement in the fingerprint region (1850 to 800 cm−1).
Table 2.
Chemical composition of the surface layer of the original cork and of the cork samples after outdoor exposure and soil burial, regarding extractives soluble in dichloromethane (DCM), ethanol (EtOH) and water (H2O, in % of the cork samples), and of suberin, lignin and polysaccharides (in % of the extractive-free cork samples) as well as the monomeric composition of the polysaccharides (in % of total monosaccharides).
Table 3.
Chemical composition of the lipophilic extract obtained from dichloromethane solubilization of the surface layer of the original cork (reference) and of the cork samples after outdoor weathering and soil burial, as percentage of the total peak areas of in the GC-MS chromatogram.
Only compounds over 1% at least in one of the samples are included.
Table 4.
Phenolic content (in mg GAE/g extract) of the ethanol and water extracts obtained from the surface layer of the original cork and of the cork samples after outdoor exposure and soil burial.
Mean of three replications and standard deviation.
Table 5.
Suberin composition (in mass percent of extractive-free cork) including total suberin (as determined by mass loss by methanolysis), glycerol, long chain lipid compounds and aromatics solubilized by methanolysis of the surface layer of the original cork (reference) and of the cork samples after outdoor exposure and soil burial.
Table 6.
Suberin composition of the surface layer of the original cork (reference) and of the cork samples after outdoor exposure and soil burial (as percentage of the total peak areas of chromatogram of the methnolysis dichloromethane extract).
Only compounds above 1% in at least one sample are included.
Fig 4.
Pyrograms of extractive-free and desuberinised cork samples from the surface layer of the original cork (reference) and of the cork samples after outdoor exposure and soil burial.
1) 2-oxo-propanal; 4) 1-hydroxy-2-propanone; 10) guaiacol; 15) 4-methylguaiacol; 18) p-4-ethylguaiacol; 19) 4-vinylguaiacol; 24) trans isoeugenol; 26) vanillin; 31) guaiacylacetone; 37) dihydroconiferyl alcohol; 41) trans coniferyl alcohol; 44) ferulic acid methyl ester. The chemical structures of these compounds are given in S2 Fig.
Table 7.
Lignin composition (in % of the total pyrogram peak area) and ratios given by the analytical pyrolysis of extractive-free and desuberinised samples from the surface layer of the original cork and of the cork samples after outdoor exposure and soil burial.