A press release commenting on this year’s cork harvest caught my eye today. It reads very much like a grape harvest or vintage report. Yet, I could not help but think that, just like with wine grapes, while the harvest may be exceptional, individual corks can still be spoiled.
I have nothing against cork. Yes, it is a let down when I open a highly-anticipated wine only to find TCA gushing out of the bottle. That happens only in a small portion of cases.
There is considerable dispute over the origin of TCA in natural wine stoppers. Some attribute it to the interaction of remnants of fungi (which infect cork bark) and the sanitizing solutions used to process cork. Others say that TCA forms or originates from the dirt that gets on the cork bark as it is being processed.
TCA is not the lone spoilage substance which gives wines a musty, bleach-like aroma. TBA (tribromoanisole) also is know to contaminate all wooden elements of a winery or cellar and can spoil entire lots of wine. These compounds are part of a family of compounds called halogenated anisoles which can occur quite naturally in many substances, including your drinking water. Production of halogenated anisoles has been described in industry and in nature. However, the origin of TCA in wine corks appears elusive.
The process of cleaning and preparing cork closures is described here (“3.4. Washing/Drying”). It has been said by some (in casual conversation) that corks become tainted when the successive vats – particularly those containing rinsing solution and rinse water) are not emptied and refilled frequently enough.
I do not have enough facts before me to say if this is true. I have not sat down and worked out the chemistry, but it seems that anisoles may become halogenated non-enzymaticaly.
So, the following speculative thoughts come to mind:
Assuming that if the fungi infecting cork bark do not produce halogenated anisoles but the use of sterilizing and cleaning solutions may, it stands to reason that a drastic improvement in cork quality and a reduction in the incidence of TCA taint could be achieved by changing the standards and procedures for cork bark processing – either by changing rinse solutions more frequently or by using different chemicals.
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