Variability of the Chemical Composition of Cork

Abstract

The chemical composition of cork was determined, following a sampling that covered the whole production area in Portugal (29 provenances from six regions) with samples taken at cork stripping. To analyse between population variations, a more intensive sampling was made in two locations. The overall mean chemical composition of cork was: extractives 16.2% (dichloromethane 5.8%, ethanol 5.9%, water 4.5%), suberin 42.8% (long-chain lipids 41.0%, glycerol 3.8%), and lignin 22.0% (Klason 21.1%, acid soluble 0.9%). The suberin compositional ratio of long chain lipids to glycerol, LCLip:Gly, was 11.3. The proportion of neutral sugars in the polysaccharides was: glucose 46.1%, xylose 25.1%, arabinose 18.0%, mannose 3.0%, galactose 7.3%, and rhamnose 0.5%. The range of values was large and the variation between individual trees seemed to be the major factor of the differences. Geographical location of cork production was statistically significant only in a few cases when considering site and not when considering regions. The population variation in two sites was important and the absolute difference between the site mean values was small. This research covers the natural variability of cork's chemical composition and discusses the contribution of the structural compounds to the variation of cork properties.

Cork Liquefaction for Polyurethane Foam Production

“…Table 1 presents the chemical characterization of the cork sample used in this work. The extractive percentage (14.1) was comparable to the average percentage reported by Pereira (2013). There was a similar percentage of water and ethanol extracts, higher than dichloromethane.…”

“…There was a similar percentage of water and ethanol extracts, higher than dichloromethane. The suberin content was smaller than the average (42.8%) reported by Pereira (2013). Nevertheless, it was clearly in the interval reported (23.1 to 54.2%).…”

“…The chemical composition of cork, with its high levels of lipophilic extractives and suberin (Pereira 2013), has great potential as the starting raw materials for polyurethane production, which has been investigated in previous studies using depolymerized suberin (Cordeiro et al 1998). Liquefaction of cork is a recent research subject, and most of the work is based on the cork dust from the cork stoppers industry.…”

Oxidative stress proteins as an indicator of a low quality of eucalyptus clones for the pulp and paper industry

“…In studies with eucalyptus, a strong positive correlation between the pulp yield and cellulose content and negative correlation with lignin content have been observed. Pereira (1988) observed variability in chemical composition, mainly for pulp content, between trees of Eucalyptus globulos in the same location and different geographic locations, a fact that corroborates the differences in the profile of proteins found among clones of this study.…”

Comparison of Py-GC/FID and Wet Chemistry Analysis for Lignin Determination in Wood and Pulps from Eucalyptus globulus

“…It is known that such amplitude of values is due to different factors such as wood origin (Miranda and Pereira 2002b;Poke et al 2006) or age of the tree (Miranda and Pereira 2002c). The values of soluble lignin observed for wood material (3.9% and 4.0%, Table 1) are comparable with the reported 3.6% (Pereira 1988) and are in the range of 4.4% to 8.1% (Poke et al 2006). The values of Klason lignin (21.4 % and 21.8 %) were observed to be in the range of 18.9% to 25.5% reported by Poke et al (2006) and near the reported 19.8% (Rencoret et al 2011).…”