For the fourth year at the London International Wine Fair, Amorim sponsored a wine faults workshop with Dr. Pascal Chatonnet, a well-known wine researcher from Laboratoire Excell in Bordeaux, France. Chatonnet began the workshop by saying, "The number one suspect in faults is cork. But plastic and screw caps also influence faults. Reduction characteristics are very common, depending on the composition of the wine; closure can also influence this."

He, like many other people, uses data on faults from the International Wine Challenge (IWC) as one of the challenge's co-chairmen, Sam Harrop MW, tracks all faults each year. Harrop has been tracking faults since he joined the challenge in 2006, earning the name "the Faultmeister." There is now data for four years of opening about 16,000 bottles per year. Harrop sees wines that may have more than one fault but groups the faults into the following categories: TCA/musty, brett (volatile phenols), sulfides (reduction), sulfur, volatile acidity, oxidation and rot.

Chatonnet uses this data because it is such a good sample; no other massive tasting keeps track of faults as well. Chatonnet claims that the sample is large, international, has consistency across the tasting, shows a real world incidence of faults; and if the experts who are judging didn't recognize a fault, then it was likely that a consumer wouldn't either.

The incidence of faults at the IWC was displayed on a chart for the years 2006-2008. The incidence of cork taint was the same and has remained constant: of the bottles with faults, cork taint stayed at an average of 29 percent of the faulty bottles. It was interesting to see that reduction carried the same percentage.

Chatonnet claims that cork taint is now at 3 percent or a bit less and that there is very little evidence of winery taint.

Sulfide reduction is a remarkably similar fault. Tasters differ widely in their ability to pick up this fault; there exist some false positives, but many go unreported and are only obvious by comparison. Reduction, Chatonnet claimed, is more complex because it can blow off or later disappear. Chatonnet states that reduction due to screw caps now represents close to 3 percent incidence in 2008, the same as cork taint.

Chatonnet led the audience in a tasting of doctored wines to see what could be recognized. He said there were different origins of volatile sulfur compounds (VSC) in wine, including the grape itself from pesticides or even the nitrogen levels in the vineyard. Aging sur lies can also produce VSC promoters.

How can VSC or its promoters be removed? There are three ways: through copper fining, by increasing the headspace to manage the O₂ intake and by increasing the O₂ transmission rate of the stopper or liner. But if copper is used, the copper creates cupric sulfate, which is not volatile. "It's chemistry," said Chattonet. "It works, but at a cost. The thiols (fruitiness) disappears; the copper reduces the aroma." When using headspace, the more headspace you leave, the quicker you lose the SO₂ and get premature aging: oxidation, he noted.

"If you don't use copper, you need to work in the vineyard--during fermentation, aging, and be concerned about evolution in the bottle along with your choice of closure," said Chatonnet.

"Your best tools really are your choice of closure and the oxygen transfer rate," he concluded.

Chatonnet said that maybe next year he will present a workshop on oxidation. wbm

--Lisa Shara Hall