Archive

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JR's notes:

Cork is one of those subjects which raises strong emotions amongst traditionalists, supporters of plastic-type closures, screwtops, et al. This is a record of a trip which started in France, moved to Spain (in a light aircraft which had a very dodgy time over the Pyrenees) and finished back in France. It is not the whole story about wine-bottle closures, of course, it is merely the story of one company. It has never been published in a publicly-available magazine, but appeared in CIRCLE UPDATE (the journal of the Circle of Wine Writers) in February 2000, which explains the technical nature of some of the text. The Circle of Wine Writers' website is at www.circleofwinewriters.org

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CORKS: Reading Between the Lines

'I thought I knew about cork before I went. I do now' says John Radford

Next time you pull a cork, have a look at the underside - the bit that's been in contact with the wine. If it's a natural cork, you'll see some lines - probably seven to nine of them - and the number of these can tell you a great deal about the cork itself, and the winemaker's attitude to his wines. Every schoolchild will be able to figure out that what we're looking at here is the layers of tree-bark, one for each year of the tree's life. Your seven-line cork will have been punched out of a nine-ring (i.e. nine-year-old) piece of bark, (one line above and one below having been lost in the process) and that's about the minimum acceptable. The finest wines and Vintage Port may have anything up to twenty lines, but it starts getting very expensive once you go beyond nine-ring bark, for reasons which will become apparent in a moment.

South-western Spain and southern Portugal have the biggest cork-oak forests in Europe and, contrary to popular rumour (often emanating from the manufacturers of new-tech plastic closures), they are not about to run out of cork and are, for the most part, extremely well-managed. I visited a forest in the Sierra San Pedro (Badajoz) as guests of Corchos de Mérida and saw the process of cork-farming from, quite literally, its roots. The trees (Quercus suber) are planted 70-100 to the hectare and the ground between them is ploughed up to encourage the growth of natural wild grasses. No fertilisers, sprays or insecticides are permitted, the whole area is fenced off to keep out the kind of animals which would destroy the young trees, and that's the way it stays for twenty years.

Knife Begins at 40

You can take your first harvest after twenty years but, although it will undoubtedly be twenty-ring bark, the diameter of the tree will have started out so small that it's only likely to be good for tiles and other industrial uses. At this time the forest is opened up to the outside world and deer, wild pigs and domestic animals are allowed to wander about at their will. This is, indeed, the area where the fabled Pata Negra semi-wild pigs truffle for acorns and it's about as natural and organic as any managed farming habitat can possible be.

The real business of getting something you can stick in a bottle comes at about forty years old, and you can harvest the tree every nine years. There are seven grades of cork bark, of which grades 1 to 6 can be used for wine bottle corks. Grade seven goes for industrial use.

Corks are made in three diameters and four lengths.

Diameter:

A) ⁷/₈"=222 mm - from 11-13-line bark

B) 1¹_/8"=286 mm - from 13-15-line bark

C) 1³_/8"=349 mm - from 15-20-line bark

Length:

D) 54 mm - these can only be made from Grade 1 bark

E) 49 mm - these are made from Grade 1 and Grade 2 bark

F) 44 mm - these are standard corks and will be made mainly from Grades 3-6 bark

G) 38 mm - these are cut down from imperfect 44 mm corks

So, with three diameters and four lengths to choose from, the price differential between a CxD (above - the biggest) cork made from Grade 1 bark and an AxG (the smallest) cork made from Grade 6 bark is considerable.

Plainly, you're only going to be able to afford the best corks if you're making a fine wine which has to survive in the bottle for a very long time - Vintage Port and Madeira (yes I KNOW you're not allowed to say 'Vintage Madeira' but you know what I mean), the great Clarets and Burgundies, Gran Reserva Riojas from the greatest years and, indeed, wines which can confidently be expected to fetch a high enough price to make the cost of the cork irrelevant.

Even so, with the most careful handling and inspection, about 40% of all the bark harvested is not suitable for even the most basic grade of wine-bottle cork and, in the past, they've tried several ways of coping with this: industrial use for cork tiles, etc. is one and any scrap or diseased bark can be thrown into the boilers to heat the water for washing, steaming, sterilising and all the other processes corks go through after they've been punched out.

All Agglo?

And then there's the agglomerated cork, or agglo, as it's known in the trade. These are the ones made in pressurised moulds from cleaned leftover cork granules held together with some kind of polymer-based adhesive. They looked about right, made the right kind of sound as they came out of the bottle, and they were very cheap indeed. However, as wine-consumption increased logarithmically in the 1970s and 1980s some cork producers were tempted to over-stretch their raw material and relax standards of inspection, and this led to a massive upsurge in cork taint problems. In the mid-1970s I used to teach an evening class and it was so rare that if we ever found a corky bottle I'd save it to show to other groups. By the mid-1980s I was finding a corky wine in almost every case.

The problem, of course, is the Honey Fungus (Armillaria mellea), whose spores lurk in the lignin (woody) part of the cork (the black bits). If there's too much lignin (as in low-grade cork) or if the cork hasn't been properly sterilised, these spores can come to life as soon as they sniff the nutrients in the wine, and they start to grow. Their by-product (I don't like the word 'excreta') is tricholoroanisole (TCA) and it's this which taints the wine. Even agglo corks weren't immune, since there were air spaces between the granules and these, too, were a haven for fungal spores.

Ehi, Amico... Ch'è Sabaté - Hai Chiuso

The problem was cracked by Bernard Sabaté, who has just retired as head of the family firm which bears his name near Perpignan in southern France. Sabaté have been - and still are - a big name in the traditional cork business for many years and Bernard, like most of his colleagues in the industry, had been conducting research on the best way to make use of cork leftovers. Cork consists of two substances, lignin (the black, woody bit which harbours the spores if not properly sterilised) and suberin - the yellow spongy bit which provides that perfect seal against the glass and the natural interface with the wine. He experimented with separating out the suberin and making agglo corks from it with only partial success. The problem of air pockets within the corks and the lack of flexibility of the polymer meant that they still didn't perform as well as natural corks in the three principal areas. He identified these as flexibility, permeability and sterility. A ll of these would have to be as good as or better than natural cork, AND the end product had to be cheaper than the cheapest natural cork - preferably half the price.

The answer turned out to be microspheres. You probably have some of these in your bathroom, as they're used as a foaming agent particularly in shower-gel and shaving cream. In the raw they look like white flour but they're actually tiny hollow spheres made of a plastic-type substance, and filled with liquid isobutane (the inert gas which is replacing CFCs in aerosols and compressors). Bernard then researched a new type of polymer-based bonding agent made without plasticisers, which would avoid the 'hard and shiny' surface of the standard agglo cork. The microspheres would replace the air pockets within the finished cork and the new bonding agent would leave a 'natural' surface of pure suberin on all the outer surfaces.

Sélection des Grains...

The corks are made in moulds of the various sizes, and these moulds are filled with suberin granules (about as fine as grains of sand), microspheres, water and the binding agent, and then heated under compression for 35-40 minutes at 160°C. The liquid in the microspheres turns back to gas - and stays a gas - and, when the process is complete, the finished cork has the same flexibility as natural cork with a real cork surface and 'feel' and, as subsequent tests proved a consistent permeability. Every natural cork is different, even those of the finest quality, punched out of the same piece of bark. Passage of air molecules through the cork varies according to the cell-structure, and this is why bottles of the same wine bottled at the same time and kept for many years in the same bin will often have developed noticeably differently. One of them has simply been admitting air molecules faster than the other.

So, if the new cork (it's called Altec) had achieved flexibility and permeability to an equal standard as natural cork, what about sterility? They're routinely batch-sampled on a random basis and in the five years they've been making the Altec closure they say they've had six corks removed as being 'doubtful'. In a press release dated 07JAN00 the company announced that it has sold one billion corks to 3,500 wineries around the world. It's an anecdotal figure, of course, but 6 out of 1,000,000,000 represents 166,666,667 to 1 against getting a bad cork. That's rather longer odds than winning the National Lottery. Oh, and the price? A typical bog-standard natural cork will cost you about 1 Franc a bottle. Altec corks are about 45 centimes.

An additional bonus which came along almost by accident was that the cork surface is so fine that it will take much more complex print or branding that a natural cork - company logos, filigree designs, one American client even has a description of the wine printed around the cork (rather than on the back-label). But, of course, by the time the customer pulls the cork, the wine's already been sold. An opportunity here for a bit of point-of-sale advertising? Our friend Dr Riedel might be interested - remember you read it here first!

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