Vanda Oliveira

Cork as a building material: a review

This review focuses on cork as a natural, renewable and sustainable construction raw-material. Cork has an unusual combination of properties making it suitable for application in buildings and infrastructures, for example insulation, wear-resistance and durability. The material properties combined with a favourable ecological footprint allow designers, architects and engineers to meet some of the Green Building demands. A summary on cork production, structure, chemistry and properties was made. The processing into cork-based products, for example cork agglomerates and composites, is detailed as well as their properties and applications in construction. The aptitude of cork-based products for compliance with sustainability and energy efficiency criteria is also addressed.

Kinetics of Oxygen Ingress into Wine Bottles Closed with Natural Cork Stoppers of Different Qualities

The kinetics of oxygen ingress into bottles closed with natural cork stoppers was investigated by a nondestructive colorimetric measurement method using the oxidation of an indigo carmine solution. In order to encompass the natural variability of cork regarding its oxygen ingress into the bottle, 600 natural cork stoppers from different quality classes and produced from cork planks of different calipers were analyzed. The kinetics of oxygen transfer was similar in all cases and could be adjusted to logarithmic models. A significant variability was found for oxygen ingress into the bottles closed with natural cork stoppers: ingress at 12 months ranged from 0.3 to 4.8 mg; 21% of the stoppers reached the limit of oxygen quantification along the experiment. The results suggest that the variation of oxygen ingress is a consequence of the natural differing features in the cell dimensions and air volume within the stopper’s structure.

Cork structural discontinuities studied with X-ray microtomography

Abstract Cork is a natural cellular material with a rather unique set of properties, and its best known application is as stopper for wine bottles. The cork tissue contains structural discontinuities, for example, lenticular channels (LCh), that influence the in-use performance of cork products. X-ray microtomography, in combination with image analysis, has been used for cork characterisation and provided new insights into the three-dimensional location of discontinuities, which are hidden for a visual inspection. It was demonstrated that the presence of LCh is positively correlated with cork density, and the void fraction of LCh in the lower part of a cork stopper is strongly related to the oxygen ingress in the bottle during the first month after bottling. The results contribute to better understanding the natural variation of cork properties.

Effect of a Drought on Cork Growth Along the Production Cycle

Cork oak (Quercus suber L.) grows in the western Mediterranean region for which the most recent climatic scenarios predict higher temperatures and lower precipitation than usual values. Cork, the tree’s outerbark, is obtained under a sustainable management system and has a considerable economic importance for forest producers and industry. Cork’s specific set of properties allows multiple usages, from cork stoppers to insulating materials. This paper presents the first results of a dendroclimatological exploratory study about the effect of a severe drought in different moments of the cork 9-year production cycle, e.g. beginning, middle or end of the cycle. The results showed that the response of the phellogen (cork cambium) to the severe drought of 2004–2006 is independent of its age. In a mitigating strategy for the impact of the forthcoming more frequent drought events, and since cork growth decreases due to the reduction of water availability, forest managers should extend cork growth cycles and/or water cork oak stands. This is a way to ensure the production of cork with enough thickness to produce stoppers, thereby contributing to the overall sustainability of the cork sector in a climate change context.