Seeking closure

The longer the closure debate runs, the clearer it becomes that every wine style has its own requirements. Matching these to the most suitable closure takes trial and error, says Patrick  Schmitt

COULD we be approaching a time when 2,4,6- Trichloroanisole (TCA) taint is no longer the critical issue in the closure debate? A stage when wine closed under cork, as well as plastic, glass or screwcap seals is equally likely to be "infected" by TCA, or rather, guaranteed to be "clean"?

And if so, how does one choose between these different materials or closure mechanisms? Take the TCA issue out of the discussion, and the criteria for choosing one type of closure over the other changes.

No longer does the argument focus on the incidence of one spoiling factor, but several. Not only that, but suddenly it appears there is no one ideal seal, but perhaps a handful, each to suit different styles of wine.

Furthermore, even with the right closure selected for the right type of wine, there is still the treatment by the winemaker, carrier, retailer, or end-user to consider, as all will affect the wine and the suitability of certain closures.

Of course TCA is still very much present, not just in corks, but in anything from cornflakes to coffee.  In fact, it’s rather unfortunate the word "corked" is used to describe "off" wine, because TCA can come from a number of sources.

James Gabbani, managing director Cube Communications, which conducted the Sabaté test, recalls in particular a screwcap-sealed wine in the closure trial which was infected with TCA.

The cause, he believes, could have been cardboard dust present during bottling, proving that TCA can even be airborne, a worrying conclusion for even the cleanest of wineries.  But, as for the compound’s presence in cork, it’s hard to judge the levels accurately. 

Certainly figures vary from 15% to 1%, but these are for the number of wines at fault, and not only could the flavours be something other than TCA, but the source could be something other than cork.

Carlos de Jesus, Amorim’s marketing and communications director, suggests around 300m  bottles were reported as faulty last year, or around 3.5% of all wines globally, although he draws attention to the Wine and Spirit Association’s trial, which, using gas chromatography to detect TCA, picked up the compound on less than 1.5% of wines.

But even with scientific studies, it’s important to check the detection level used, which varies – it was as low as 0.2 parts per trillion in the case of Sabaté’s trial, but for others it might be 2ppt, or more.

As for human detection, most people can smell or taste TCA at around 5ppt, professional wine tasters down to 1.5ppt or even lower, although drinkers do vary in their sensitivity to the taint.

And to give a quick idea of the power of this compound in affecting the flavour of wine, even in minuscule doses, it is said that one teaspoon of TCA would be enough to spoil the entire US wine production.

Sources of TCA

So where does TCA come from? In cork, according to Dr Miguel Cabral, director of research and development at Amorim, it’s believed the substance is formed by the interaction of certain moulds with trichlorophenol (TCP), and the moulds turn the TCP to TCA because the former is toxic for them.

The TCP on the other hand is created by the reaction of phenols with chlorine.  Phenols are found in many organic substances including corkwood, while the chlorine can be both naturally-occurring or introduced by man.

Whatever the source of TCA, cork is the classic carrier, and the parochial nature of the cork industry and its past monopolistic position, provided the perfect conditions for a do-nothing approach to the problem of TCA, which in any case was only identified in 1981.

As de Jesus admits, the arrival of alternative closures has, in fact, been good for the cork industry, as it has provided the motivation to assess the problem and innovate. 

Currently, the techniques to attempt to solve the problem of cork taint, if not eradicate TCA, are myriad and include preventative as well as curative measures.

Amorim, in particular, has invested heavily in new cork plants near the bark-producing forests, which include huge areas of concrete-covered floors for seasoning the cork, as leaving it on the soil increases the risk of TCA forming.

The removal of any wood from these factories is also important, and even the pallets are stainless steel.  Hand selection of the bark, cutting out green spot, as well as any pieces that have been in contact with the soil, also helps.

Curative measures on the other hand at Amorim include boiling the cork without compressing it, as well as the more technologically advanced ROSA and INOS II systems.

These latter two use steam to clean the cork, be it granules used for agglomerated corks or the natural stoppers punched from the boiled bark. 

Of course Amorim isn’t the only company tackling the problem, but it is the largest cork manufacturer, churning out some 3bn of the 12bn corks sold annually.

Oeneo, owners of Sabaté and producers of a range of closures, have developed the Diamant process for extracting TCA from cork granules using supercritical carbon dioxide, and rather than attempting to explain this process, it’s just worth noting that it’s the same technique used to take nicotine out of tobacco, or caffeine from coffee, and that it’s highly effective.

The company also use a ROSAlike process called Revtech, which uses steam.  Competitors have also developed technology to combat TCA, for instance Janosa’s Jatosy, a washing process, and Juvenal’s Delfin, which uses microwaves.

As for the efficacy of these treatments, Diamant appears the most powerful, effectively eliminating TCA, but the process can only be used on granules and discs as it distorts natural stoppers.

ROSA, on the other hand, can be used on granules, discs and natural stoppers, and tests show it reduces TCA by 69 to 80%. Revtech, Oeneo’s steam treatmentmethod, removes, it is claimed, 70 to 80% of TCA, while Janosa’s Jatosy promises around a 75% reduction.

As for the microwave treatment, no figures are available, though it should be mentioned that  the science is still young.  Next step? So, what does the success of these measures mean for the wine producer considering a range of closures?

For a start, if cork is the preferred option, it must be from a reputable source. One of de Jesus’ bugbears is the fact that,  despite the efforts made by Amorim, unless the whole industry cleans up its act, it will never achieve an untarnished reputation.

For this reason he wants to build a branded cork proposition, and hopes the industry will  soon be asking not just for cork, but for Amorim corks.  Those that can’t provide TCAfree cork will then go out of business.

Amorim, however, believes the cork industry needs to consolidate, and it’s also behind the introduction of a code of practice for the whole cork industry, outlining, and hopefully enforcing,preventative measures.

Nevertheless, de Jesus thinks that cork’s share of the closure market, about 93%, could fall over the next few years to 80% or even 70%, although he suggests that of this potentially reduced market, "The premier league of cork companies will increase its share."

However, Antonio Amorim, chairman of the company, says, "The image of the cork industry is better than it was six years ago." 

He also notes that "plastics are starting to lose their market position", while even Australian and New Zealand producers are "starting to question reduced flavours and aromas of wines under screwcap", apparently.

In fact, if, as suggested at the outset, the problem of TCA derived from cork is nearing an end, or at least solutions to it are apparent, then the selection of particular closures must be based on other factors, in particular, the closure’s role in conditioning the wine.

Convenience and image are also important, but it is the question of oxidation that is starting to fuel the debate.  Before analysing the permeability of different closures, it is worth noting that there is some discussion over the role of oxygen in the ageing of wine.

Does wine actually need oxygen to develop, or does it do it anaerobically? And if it does require oxygen, at what rate? Is macro or microoxygenation better? The understanding of oxygen’s function in the ageing process of wine is still fairly undeveloped, but certainly oxygen is needed to prevent reduction in wine because sulphur and yeast lees both consume oxygen.

Also, evidence shows that wine draws oxygen through permeable closures over time and that this oxygen affects the chemistry of the wine.  This process is slow through cork, but, not necessarily in plastic, where oxygen can pass quickly down the sides of the stopper.

In screwcap the only oxygen the wine is exposed to is the amount found between the seal and the wine, in the neck of the bottle. 

However, what is key is that the amount of oxygen consumed by a wine aged under "good" cork is more than that found in the neck of the bottle, or in the cells of the cork, and it is released slowly and gradually over time, and the important aspect for the industry seems to be how to control the oxygen exchange.

Down to the winemaker

Nevertheless, many have suggested that the way to prevent reductive characteristics (sulphurous smells) developing in wines aged under screwcap, and possibly under other closures, is really down to the winemaker, who can remove sulphur, or hydrogen sulphide through the addition of copper sulphate.

As Villa Maria’s Warren Adamson says, "People are talking about reductive issues now, but they have been a by-product of winemaking for centuries and it’s not going to go away because we change closure.

We’ve to be aware of how we are finishing our wines.  Screwcap won’t mask anything.  What you put in, you get out."  But, having heard this from several producers, it is interesting to note that permeable screwcaps are being developed, ones which could provide an environment of controlled oxidation.

This seems to negate the very reason for using screwcaps in the first place, which is that they provide a hermetic seal, but nevertheless, provides evidence that there may be a need for oxygen exchange, or rather the demand for a seal which might mimic the ageing rates of wine under cork.

And if so, why bother? Well, aside from the convenience, and TCA issue, where screwcaps triumph over cork is in their consistency, whatever their effect on wine over time.  Cork stoppers have the potential to cause the same wine to age differently, being a natural product with inherent variations.

Nevertheless, even with the perfect seal, the same wine is likely to taste and smell differently depending on how it is handled during shipping, for instance, whether, as Gabbani points out, it is left on a dockside in 30 degrees plus temperatures before transporting, as well as how it is stored, which depends on the retailer, and how it is then treated by the end user.

And because of such variables, and the range of styles of wine, as well as prices and ageing potentials, it is likely that no one closure will provide the best solution, but rather a mixture of seals, depending on the winemaker’s preference.

Fiona Reith, European account director for Crown UCP, admits, "There’s an argument for screwcaps on rosé and Beaujolais Nouveau, wines that need to be kept fresh," before adding that she believes screwcaps "will hit a 20% market share globally".

Anne Seznec, Guala Closures, makes a different point in defence of screwcap: "Wine is travelling more and more, and if you’re not sure about the sealing property of the closure you risk a lot, not least because the selling point asking for a bottle to be replaced could be thousands of kilometres away."

Palandri’s Andrew Blythe, for instance, notes that the company "chose to switch to screwcap, especially for wines sub-£6, because of the spoilage factor with cork," but also because at lower price points in particular, the UK retailers were asking for it.

And whatever the arguments, if the major multiples want a particular closure, they have the power to enforce it.  According to a study commissioned by SupremeCorq, a manufacturer of synthetic closures, there was a big shift in terms of acceptance of alternative closures, in particular the levels of acceptance of screwcap this year versus last year.

"People aren’t suddenly anticork, they are just more broad minded than they were," said Richard Halstead, managing director of the study’s researchers Wine Intelligence.  But for the winemaker, the choice of closure has got to be based on which will show the wine in the best possible light.

And to guarantee against TCA? Well, one solution could be to develop wines which are TCA resistant, which is apparently not impossible, and could be necessary, because, as de Jesus says, "If we could eradicate TCA in corks tomorrow we would still have TCA in wine."