The Cork process – from Bark to Bottle
Amorim is the world’s largest Cork manufactuer. This came about by a very fortunate friendship between Américo Amorim and the Soviet Ambassador for Portugal during the 1970’s. In 1974 Portugal went through the ‘Carnation’ revolution – a relatively peaceful military coup and created the Estado Novo (New State). This involved nationalization of many private businesses and workers ‘liberating’ land from their wealthy employers. These new landowners immediately went to work determined to make as much profit from their fortune as possible. Cork trees were harvested too soon, pesticides and insecticides were used and previously off-limits areas of the bark were removed. In general the quality of the cork was greatly reduced. The Kremlin was a support for the new administration and so the Soviet Ambassador became a very powerful man and he made sure Amorims land was not taken away from the family.
With 730,000ha of cork forests in Portugal it’s by far the biggest grower of cork trees in the world and the Alentejo region NE of Lisbon is the main source. Here the Quercus Suber oak tree has its bark harvested on a strict 9 year cycle – the bark grows into thick cork to protect the tree from the heat of the region and any occasional forest fires. There are many landowners who sell bark to the cork processing companies but the best grow their trees organically and encourage biodiversity and sustainability by using the land to grow wild herbs and eucalyptus trees for the pulp/paper industry, which also gives their workers an income all year round rather than just through the cork harvest from May-July.
TCA or 2-4-6-Trichloroanisole is the main anisole that can effect wines (although tetrachloroanisole and tribromoanisole found in chemical sprays/treatments can also be responsible) and can cause a taste defect when present in tiny quantities of Nano grams or parts per trillion. The level detectable is thought to be around 5Ng which is the equivalent to 1 second in 320 centuries, a grain of wheat in 100,000 tonnes or the same as throwing 2 sugar cubes in Lake Geneva and having it taste sweet.
The cork companies in Portugal are the first to admit that during the 80’s and 90’s they were the villain’s of the wine world and handled the situation regarding TCA problems very poorly. Often blaming poor bottling, poor winemaking, infected winery equipment or problems with the transportation of the corks; but seldom admitting the cork itself was the problem (while increasing their prices year upon year!). There was no competition and therefore no replacement, winemakers and consumers just had to take the risk.
Finally, enough was enough and out of this situation came alternative closures – screwcaps, plastics and even glass stoppers. Screwcaps had been around for quite sometime but always had a negative reaction from consumers, but with a movement headed by Clare Valley Riesling producers, much of Australia and virtually all of New Zealand were turned into screwcap lovers in a space of 10 years.
Although around 75% of the closure market is still cork (screwcap is slowing and plastics are declining) the Portuguese cork industry has inaugurated a new paradigm of industrial management improving every aspect of the process from forest to final product. In recent years around 400 million Euros have been spent on modernization and new technologies for the industry. Amorim alone spend 50 million Euros on Research and Development every year.
Some of the methods of prevention include –
- Greater control of the forests – FSC certification for higher levels foresty stewardship.
- Cork lot traceability – damper more shaded areas of forest may be more prone to TCA.
- Storage of bark – it is stored for nine months in the open air, previously on the bare earth or wooden palettes – now on concrete.
- Removal of moulds from bark and areas closer to the ground, cutting off the bottom areas of the cork bark.
- Boiling system – previously bark was washed in water that was seldom changed and chlorines were added to bleach the bark. Now rapid boil washing in self-cleaning filtered water and if bleached then peroxides are used.
- Drying bark rapidly – previously it could take 3 weeks for the washed bark to dry out. This was the ideal condition for mould to grow.
Chlorine products such as wood treatments, pesticides or flame-retardants contain Trichlorophenols and through biomethylation of these, caused by penicillium moulds, TCA is created. Reducing any chemical contact and avoiding mould growth reduces this risk.
Decontamination systems and volatilization methods using water steaming can reduce TCA by 40-90% and processes such as ROSA used by Amorim (high pressure, high temperature steam cleaning) will not affect the corks integral structure. TCA has a volatility threshold of 60% and therefore in the right conditions can be ‘distilled’ out of the cork fragments. Oeneo produces closures using the diamant process (DIAM) where cork granules are blasted with super-critical CO2 (high temperature, high pressure) to remove TCA. Furthermore, research into ionization, micro-waves, symbios and enzymic actions along with gas chromatography technology will soon make TCA contamination in wine closures totally detectable and almost extinct with the ambition of bringing TCA levels down to a minimum of 2Ng. Amorim carries out around 300 tests per day on random batches of cork.
But whatever the advances in TCA prevention are, the stigma of corked wine will still hang with the Portuguese cork companies for many years to come. There are still plenty top quality wines, that normally should go the distance and last 30-40 years, waiting to be opened on a special occasion, that are lying in cellars and thick with TCA contamination. Corkiness wine is the ‘go-to’ fault for any wine that does not taste great, even though oxidation is far more a common problem. It will take many years for the cork industry to be forgiven but at least the percentage of TCA problems from now will be minimal.
Amorim – www.amorincork.com
Oeneo – www.oeneo.co.uk
George Taber – the author of Judgement of Paris – has a book called To Cork or Not To Cork. It gives a fascinating history of all closures and a great insight into the production and politics of this industry.
