For many of the world’s cultures the sound of a popping cork is synonymous with good food, good times and good company. But we seldom give a thought to where that cork came from or how it was made. The members of the Rotary Club Estoi Palace International recently visited the cork processing factory, Novacortiça, near Sao Brás to discover the answers.
We were welcomed to the factory by our guide Gianluca Pereyra who gave us a short presentation before we toured the factory floor. Ginaluca told us that cork is the outer bark of the cork oak tree (Quercus suber) which flourishes around the Mediterranean basin in Portugal, Spain, France, Italy, Algeria, Morocco and Tunisia.
The bark of the cork tree has a unique honeycomb structure composed of tiny 14-sided cells and each of those cells is filled with air. Since air makes up almost 90% of the substance of the bark it means that cork is extremely lightweight.
Cork is also watertight and airtight and as a result it does not rot. These qualities make it one of the best seals for wine bottles. As well, the cell structure of cork makes it extremely flexible and elastic. This means cork will return to its original shape after being compressed under pressure, which explains why cork became an indispensable material for making bottle stoppers.
Cork trees live for approximately 200 years. The trees are not harvested until they reach about 25 years old, then the bark is stripped from the trunks just once every nine years. The bark is harvested during the spring and summer, as this is the time of year the trees experience rapid growth and the new cork cells break away from the inner cambium easily with little damage to the tree. The process is temporarily debilitating but the outer bark quickly re-forms and the trees recover.
Stripping cork is a delicate job that is still done by hand with traditional tools and methods. So far no mechanized or automated process has been as successful as traditional harvesting techniques. Portugal harvests approximately 184,000 tons of cork per year.
At the Novacortiça factory the cork is boiled for 1 hour at 100 Celsius to disinfect it, to kill any micro-organisms, and to remove tannins which could change the flavour of wine.
Much of the cork that arrives at the factory is turned into small disks approximately 4 cm in diameter. These disks are subject to stringent quality control and are eventually sorted into three grades: Extra, Superior and Medium.
We watched as a machine punched out flat round disks which will later become wine corks.
The approximately 4 cm disks move along a conveyor belt through a quality control area, where malformed disks are discarded. The disks are then sorted by density by machines enhanced by lasers. The machines determine how much light can penetrate a disk and then grade that disk accordingly, the less light that penetrates the disk the higher its quality.
Finally, the disks move past a group of women who sort the disks looking for any signs of fungi which will show up as green or yellow spots on the disks. Because the cork has been boiled the fungi is no longer active, but it is considered unsightly and so those disks are removed from production. Testing has proved that the human eye is actually more accurate than machines at detecting the discolorations on the disks.
Once the sorting is completed the disks are packed into large sacks for storage and delivery. Each sack contains approximately 40,000 disks and Novacortiça produces approximately 1.5 million disks per day.
The packaged disks are shipped to clients in Spain, France and Italy, the world’s largest producers of sparkling wines.
It was extremely interesting to watch the process from beginning to end and I believe we all came away from our morning tour not only educated about cork, but much more appreciative about the work and care involved in making every cork that we had previously taken for granted.
The Novacortiça factory is happy to arrange tours. They can be reached through their website http://www.novacortica.pt.
