I promised you more on the 'screwcaps taint wine' issue, and now it's time for me to deliver. Off Licence News carried a story on its front page last week titled 'Cork may yet redeem itself'. This was based on the results of the faults clinic run at the International Wine Challenge (see my report here) in 2006. This was coordinated by Sam Harrop MW, who I know quite well - I was able, therefore to have a behind the scenes look at how this was carried out, and I was impressed by its rigour. Sam's palate is pretty hot, and so I'd be inclined to put a fair bit of trust in these results.
In short, 4.4% of wines sealed with cork were affected by cork taint (2.8%) or oxidation (1.6%), and 2.2% of wines sealed with screwcaps were affected by reduction issues. Sam's going to send me the raw data so I can look at all the faults in more detail, but these figures are interesting. They suggest that musty taint (cork taint) is coming in a bit lower than previous surveys (which seem to agree on a figure of around 4.5%), and that screwcap reduction is a real-world problem.
But I have some quibbles with OLNs reporting. To suggest that cork may redeem itself is a little premature - and I think the way they have reported the whole issue is a little bit sensationalized. Then there are the factual issues. Sulfur dioxide (SO2) does not smell of rotten eggs. That's hydrogen sulfide. And the sulfide problems caused by the tight seal of tin-lined screwcaps don't cause the wine to smell vegetal or eggy - it's more a problem of rubbery/struck flint aromas (mercaptans are responsible for these).
It's a shame also that the national press have come in with the line that screwcaps taint wine. Screwcaps with tin liners (the form used predominantly in Australia and New Zealand) have the potential for 'reduction' problems (caused by sulfur compound such as disulfides but more commonly mercaptans), but this is the sort of fault that most consumers and most wine trade people would never pick up. It's hardly in the same league as cork taint problems, where the wines are completely spoiled. Certainly for many fast rotation wines there's never a risk of reduction problems (which typically take 12-18 months to occur), and it would be a shame if this sort of reporting were to kill screwcaps as a closure: with the right liners I think they can be an ideal wine closure, although I do have misgivings about the supertight seal caused by a metal layer in the lining material.
Sorry if this is all a bit technical, but it's important stuff, and without the detail we're likely to miss the real issues.