Made in forests, spoiled in processing?
October 23rd, 2009
Docking.
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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October 23rd, 2009 at 1:31 pm
Ever smell TCA in hotel water? I do–often.
To your last point: I was led to believe that’s what the cork industry is doing or has done. Do you have information to the contrary?
October 23rd, 2009 at 2:03 pm
Thomas,
My understanding is that at least some producers are moving to improve their processing methods.
This would probably be reflected in dramatically lower prevalence/incidence of TCA taint - which has yet to be touted.
As it stands, this press release only touts what a great harvest they have had this year. To which I responded with this post.
October 23rd, 2009 at 2:14 pm
The cork industry has a record of producing great press releases, a lot of good news stories, and still no definitive remedy.
Either the will or the science (or both) isn’t there yet.
Then again, there was a time before cork, so what’s to preclude a time after cork? Progress waits for no industry, except maybe the one in Detroit.
October 24th, 2009 at 10:36 am
I find it ironic that when it comes to this topic we’re asking for some form of closure from the cork industry.
October 24th, 2009 at 4:48 pm
Arthur: Recalling my o-chem from 30 years ago, anisole is a strong ortho/para director in electrophilic aromatic substitution reactions - I believe phenol is as well.
Many fungi will catalyze the formation of TCA from 2,4,6 trichloro-phenol, which is either a contaminant or a breakdown product of chlorinated pesticides that were once used widely in cork forests, and are presumed to have accumulated in the environment.
Chloroperoxidase and bromoperoxidase, enzymes found in some fungi and bacteria, can also halogenate phenol and anisole.
So, fungi break lignin down to phenols and anisoles, which can be halogenated - when sources of halogen are present, presumably form santiizing agents - by those same fungi and some bacteria, as well as perhaps non-enzymatically. Also, halogenated aromatic compounds are present in the environment as a consequence of the use of pesticides, which can be converted by these same bacteria and fungi into TCA.
Even eliminating sources of halogen from cork manufacture will not eliminate TCA, until this environmental source is depleted.
November 9th, 2009 at 8:32 am
[...] I broached the subject of improving cork processing and production to reduce the incidence of T.C.A.-tainted wines. It is cork taint that hindered me from completing a piece on a rather rare variety. Two separate [...]