From tree to table – a visit with Amorim, the world’s largest cork stopper producer

The cork oak tree - since 2011, officially Portugal's national tree

The cork oak tree – since 2011, officially Portugal’s national tree

The science of wine closures and, indeed, how wine develops in bottle (irrespective of the closure) is complex.  It’s a topic which has been under the microscope over the last decade or so when the cork versus screwcap debate has raged, generating lots of research and development, marketing campaigns and column inches in its wake.  Fellow writer Jamie Goode followed the closure debate from the outset and rehearses the arguments in detail here (which links to a special section of his website dedicated to the issue).

This week I had the opportunity to experience first-hand how aspects of this research and development have been implemented when I visited with cork manufacturer Amorim, the world’s largest producer of cork stoppers (which represent 58% of its business). The Portuguese company is nine times bigger than its next competitor.

The cork harvest takes place between mid-May & mid-August

The cork harvest takes place between mid-May & mid-August when the tree is producing fragile new cells, making it easier to remove the bark.

Following through the process from the highly skilled cork harvest (which can only be done by hand – see my video here) to packaging of the finished product, I thought I’d share with you how Amorim has acknowledged and tackled the most pressing criticism about cork, the risk of 2,4,6-trichloroanisole (TCA) contamination, which results in corked wines/cork taint.

Reducing the risk of  2,4,6-TCA

Following harvesting, the lower part of the bark nearest the soil, which can harbour naturally occurring TCA precursors (fungi), is removed.

During the outdoor seasoning process, which takes 6-9 months, cork bark is now stored on tarpaulin or concrete to protect it from contact with the soil which can harbour TCA precursors.

Last year's seasoned cork in the background; this year's crop to the fore

Last year’s seasoned cork in the background; this year’s crop to the fore

Cork bark is boiled in water sourced from a well, not municipal water which may contain chlorophenol compounds which combine with the fungi to produce TCA.

Being boiled

Being boiled

The boiled cork is stored on stainless steel pallets as opposed to the (cheaper) wooden pallets of old, which can harbour TCA precursors.

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Premium bark suitable for wine stoppers (its most profitable application) is hand-selected – apparently only around 30% of the cork processed makes it into bottle; yellow or green spotted bark (a sign of TCA precursors) is rejected.

Yellow spotting - a reject

Yellow spotting – a reject

Each batch of cork stoppers and discs for twin tops are subjected to “statistically relevant” gas chromotography (“GC”) tests (over 14,000/month) which identify TCA. Amorim introduced its first gas chromotography machine in 2001 and now has 12 units. These days they operate faster, analysing more. Research to accelerate the process continues and, ultimately, Amorim’s aim is to analyse all natural stoppers. As for the latest model, it incorporates an olfactory port (pictured), which additionally allows for sensory (human) as well as chemical analysis.

GC olfactory port

As a curative measure, cork stoppers and granules for agglomerated cork stoppers are heated via ROSA® machines (developed by Amorim and introduced to the production line from 2003), whose steam distillation process volatises TCA within the cork cells, which is then separated off via a chimney.

During the finishing process, all stoppers are bleached/disinfected using peroxide (as opposed to chlorophenol compounds which combine with fungi to produce TCA).

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Technical corks (agglomerates) and natural corks range in price from 2.5 cents to 2 euros – quite a difference!

The finished product is sealed in polyethylene bags containing sulphur dioxide, which is a preservative and has anti-bacterial properties.


It was a thought-provoking visit, which took me back to my days as a commercial litigation lawyer, prompting reflections about causation. I also reflected on my personal preference for screwcap, which stems from having experienced far fewer faults in wines bottled under this form of closure.

This contrast between the performance of cork and screwcap has been particularly stark (and disappointing) at regular tastings which I present of Australian wines (typically bottled under screwcap) and Portuguese wines (typically bottled under cork).  Not just vis-a-vis TCA, but random oxidation too, which can result in bottles of the same wine showing different levels of development and, it follows, a less consistent flavour profile.

That said, it’s important to acknowledge that most of the wines which I have tasted under screwcap are relatively young. Screwcap cannot yet boast cork’s track record for ageing wines over decades.  Though a new generation of screwcaps allow for (controlled) oxygen transmission similar to cork stoppers whose 800 million microscopic cells are oxygen pockets, we cannot yet say for sure whether screwcap would have preserved the 1924 Ramos Pinto Vintage Port I tasted recently as well as its cork.

Portugal is the world's biggest cork producer

Portugal is the world’s biggest cork producer

Perhaps my preference is also informed by the fact that Australian winemakers might be expected to be masters of screwcap (itself subject to criticism about sulphide reduction), having been at the vanguard of its use and development.  What’s more, renowned for their fastidious winery hygiene and intolerance of faults, they might also be more effective gatekeepers of TCA precursors at the winemaking stage.  So the less fastidious or more recent adopters of screwcap might not share the Australians’ track record for fault free wines and, conversely, some countries may have better results with cork.

As for the faulty corks, to date I haven’t investigated who produced them. However, as Amorim’s Director of Marketing and Communication Carlos de Jesus quite reasonably pointed out, it’s important to differentiate between cork manufacturers where “not everyone has the same resources or is doing the right thing.” He estimates that Amorim has invested c. €5m/annum in R & D over the last decade or so.

The problem here for end consumers is that most stoppers don’t disclose the marque of their manufacturer so, at the point of discovery of the fault, one cannot usually tell who produced the offending cork.  Why not add Amorim’s marque as well as that of the wine producer to all its stoppers to differentiate Amorim from others?  Where it’s a brand management issue for negotiation with individual wine producers perhaps that’s unrealistic but, for my part at least, going forward I shall endeavour to identify the manufacturer of any faulty corks to see what patterns may emerge.

While the debates about which is the optimum closure rattle on, what is beyond doubt is that the fight for market share between competing closures has been highly beneficial in terms of product improvement and innovation.  For example, where the cork industry has trumpeted its eco credentials (owing to cork forests’ sustainability, recyclability and bio-degradability – click here for details), this year’s European Aluminium Foil Association’s “Aluminium Closures – Turn 360?” campaign is highlighting the recyclability of aluminium screwcaps.

Harvest is strictly regulated.  The perimeter must be 70cm before first harvest (which is typically when the tree is 20-25 years old).  After that, it can only be harvested at minimum 9 year intervals.  It's a long term game, only producing a return on investment after 70 years!

Harvest is strictly regulated. The tree’s perimeter must be 70cm before first harvest (which is typically when the tree is 20-25 years old). After that, it can only be harvested at minimum 9 year intervals and, in height, only up to three times the perimeter measurement can be removed. It’s a long term game, only producing a return on investment after 70 years!

On the other hand, where the convenience factor (no corkscrew required/resealability) has worked in screwcaps’ favour, Amorim has just launched a twist open (and shut) cork (pictured) in collaboration with glass manufacturer O-I, aimed at fast turnaround wines (click here for full details).

Amorim's new twist off & on cork

Amorim’s new twist off & on cork

The new bottle’s neck features a helix-shaped groove into which the innovative twist to open cork naturally aligns for a snug, air-tight fit.  And it gets the last word (okay sound) too – it re-produces cork’s traditional “pop” on opening!

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