I'm sure just about everyone is fed up with the issue of cork taint by now. I suspect magazine editors yawn wearily when they get yet another proposal on the subject. It's been 'done' again and again. But it's the issue that won't go away, and one that is in danger of polarizing the different camps into a trench warfare scenario, where each side just chants the same slogans repetitiously, with the other side not listening. This is why I'm continuing to write about it, hoping to forge a balanced position on the basis of good data -- and not just anecdotal accounts, strongly held beliefs and murky conflicting interests.

So, with this goal in mind, and as they currently stand, let me try to crystallize the key issues in point form, trying to be as balanced and factual as possible.

Cork taint is a problem. People are quite rightly cross about the fact that the traditional closure ruins  a significant percentage of bottles of wineat source. While in some cases this is due to the mechanical failure of the cork, in most instances it is through the contamination of the wine with tiny (but still detectable) quantities of trichloroanisole (TCA). Semi-quantitative estimates of cork taint consistently come up with figures in the range of 2-7%, although most of these studies don't involve chemical verification of the presence of TCA in offending bottles, and no definitive analysis has yet been carried out on a large enough sample. Even so, this is an alarmingly high failure rate and one that many in the wine industry consider to be intolerable.

Corks are the main culprit of TCA contamination. While there are other sources of TCA contamination of wine, there is no good reason to suspect that the majority of TCA contamination is NOT caused by natural cork. The stochastic nature of the incidence of TCA contamination, with one bottle being affected while others in the same batch aren't, is supportive of this conclusion. So are experimental data such as those from the ongoing Australian Wine Research Institute (AWRI) trial. It's probably worth questioning the independence (or judgement) of anyone who argues that corks aren't the main cause of this problem. While there have been well publicised incidences of TCA occurring endemically in wineries these are rare, and when this has happened it has usually affected the entire output of the winery, not just the odd bottle.

People differ in their sensitivity to TCA. The human olfaction system needs to be taken into account in assessments of the rate of cork taint. Studies have shown that people differ markedly in their sensitivity to different odorants, with individual differences in sensitivity as high as a factor of 10 000. There is every reason to suppose that even the most highly skilled wine tasters will have different biological sensitivities to TCA. This explains the often reported incidents where two wine experts (MWs even) have disagreed about whether a particular wine is corked or not. [Having said this, even if one's individual sensitivity to TCA is low, a corked bottle will presumably differ from a pristine one in other respects too.]

The Aus/NZ screwcap crusaders are running ahead of the data; the pro-cork lobby is also misguided. Wine writers seem to be polarizing into two camps on the issue of cork taint. On the one hand we have the (mainly antipodean) contingent who have embarked on a crusade against natural cork. They advocate -- with evangelical zeal -- its complete replacement with screwcaps (known commonly and rather irritatingly by the brand name 'Stelvin', or technically as ROTEs, for 'roll-on tamper-evident'). The other camp includes those in favour of the cork. Members of this second camp vary in their mission: some deny that there's a particular problem with cork, and that all the accounts of cork taint are wild exaggerations. Others acknowledge the problem with natural corks, but advocate sticking with them because they play an important, active role in the ageing process of wine that we know and like. I feel that both positions are ill-advised. Why? Well, the screwcap crusaders are simply running ahead of the data. Although we know that alternative closures work well in the short-term, there is a lack of independent, statistically sound data showing that they will work for long-term ageing of fine wines. Until we have these data, it seems a foolish gamble for producers to shift from a closure that causes failure in a few cases but works very well in others, to one that could potentially ruin all their wine in 10 years’ time. Two additional points here. The Australian contingent may well point to Rieslings that have aged wonderfully over a decade ‘under Stelvin’ (with screwcaps), but this is not in controlled trials, and there’s a world of difference between Aussie Riesling and classed growth Bordeaux. We like the way that fine wines age under sound corks; we need to be sure that these fine wines would age in a similar way under alternative closures over time-spans of more than just a few years. On the other hand, those who claim there is no problem with cork are quite simply in denial. There’s very little reason to stick with cork for wines intended for early consumption: this encompasses the vast majority of all wines produced. And those who claim that cork plays a significant role in the ageing of fine wine are merely expressing an opinion in the evidence of data.

The only thing that will settle this issue is more scientific evidence, not more lobbying or rhetoric. Personal opinions, no matter how eminent or self-important the individual expressing them is, are not going to settle this issue. Nor are crusades, no matter how well intentioned. What we need are independent data from trials that have been designed specifically to yield statistically significant results. Non-scientifically literate wine writers may find this hard to accept, but anecdotal evidence from tasting several bottles of old wines sealed with synthetic corks or screwcaps -- while of interest -- won't be much use in helping us reach an answer to this important question.

Conflicts of interest must be disclosed. Because this is an issue of economic importance, there's a lot of PR/marketing money flying around. And some of it has found its way into wine writers' pockets. However much these writers believe in the cause they are promoting, once they take freebies or even cash retainers, they can no longer hope to be considered an independent source of information on this topic. They may still write sensible things on the topic, but there's a worrying lack of honest disclosure by people who should know better. If you write a piece on this topic and you've had hospitality, flights or even payment from the cork industry or from screwcap manufacturers, then to fail to disclose this is a breach of journalistic ethics.

The environmental case for retaining corks is irrelevant here. The environmental argument -- that we should stick to corks because of ecological reasons -- is a smokescreen. It is completely separate to the debate about whether better alternatives for sealing wine bottles than cork exist.

Conclusion: a balanced view. For wines intended to be drunk young, natural corks should be replaced with screwcaps or synthetics. For wines intended for cellaring, let's stick with natural cork and wait for the data to emerge showing whether the replacements will do the trick. If they will, then I'll join the crusade for change. But now it's premature.

See also: special section devoted to the closure debate

Have anything to say on this issue? E-mal your responses to jamie@wineanorak.co.uk