Variability of suberin composition of reproduction cork from Quercus suber throughout industrial processing

The chemical composition of suberin was studied in cork planks fromthree different trees of Spanish Quercus suber at four different stagesof the industrial processing of first transformation: stripping (a),first rest (b), boiling followed by open air rest (c1) and boilingfollowed by store-room rest (c2). The monomeric composition wasdetermined by gas chromatography/mass spectrometry in the product ofdepolymerization of the free of extractives cork with sodiummethoxide-methanol. The average concentrations of the main monomerswere: 1-alkanols (C-20-C-26) 4.17 %; alkanoic acids (C-20-C-26) 5.99%; alpha, omega-alkanedioic acids (C-16-C-24) 6.20 %;omega-hydroxy-alkanoic acids (C-20-C-26) 29.41 %; erythro- and threo-9,10-dihydroxyoctadecanedioic acids 6.76 %, erythro- andthreo-9,10,18-trihydroxyoctadecanoic acids 9.50 %,9,10-epoxy-18-hydroxyoctadecanoic acid 2.72 % and9,10-epoxy-octadecanedioic acid 2.93 % and ferulic acid 5.05 %.Significant differences were observed between samples taken at thestripping and after boiling with store room rest, and both groups ofsamples differed from those picked after the other two processingstages. Ten components were selected as providing the greatestdiscrimination among stages: 9-octadecenedioic,18-hydroxy-9-octadecenoic, eicosanedioic and9,10-epoxy-18-hydroxy-octadecanoic acids, tetracosanol, and fiveunidentified components.