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Newsletter December 2020

How Many Good Bottles Do You Think

Will Be in a Case of 10 Year Old Wine Using Cork?

How many if the cork is protected with ProCork's breathable semi-crystalline Cork Tannin barrier?


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A finest quality cork showing signs of structural collapse after having its tannin extracted by wine for 15 years

and a solution of 10% alcohol in distilled water after it has been in contact with cork for 2 weeks.

After asking around, some people would not be surprised if, with cork, three were good, six were ok but well short of the good ones and three were poor.

One wine lover who heard about our question got in touch to say he had bought 60 bottles of a 2012 Bordeaux Superior this year with 8 years under ProCork and with ProCork, he would expect all twelve bottles in a case will be good because he had only opened good bottles so far.


The main offender is Cork Tannin. The variation in Cork Tannin between corks is amazingly high and new research is indicating Cork Tannin may destroy the wine flavour as insidiously as TCA.

In one study, Cork Tannins extracted into wine in 10 days from corks of the best quality, ranged tenfold from 53,000 to 742,000 parts per billion*. At 200 parts per billion the astringency of Cork Tannin is noticeable, that’s a few drops in an Olympic sized swimming pool.

Some wine critics are starting to observe that Cork Tannin appears to block the ability to taste the full flavour of the wine. Jean-Marc Quarin, independent wine critic, published a comparison tasting in his Chronicles on 21 October, 2020 where he identified the presence of bitter and tannic effects which “blocked the progress of the stimulation in the mouth and damaged the finish”. Cork Tannin was later shown to be responsible.

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ProCork                                       cork

17 years in the cellar


The problem with cases of 5 to 10 year old wine has nothing to do with TCA but the cork industry keeps pointing to TCA and that is a distraction. Rarely is TCA the problem. The problem is due to too much air getting into some bottles and Cork Tannin is causing astringency, bitterness and loss of flavour to varying degrees in other bottles.

ProCork’s crystalline membrane solves the problem and allows nature’s cork do its work without ruining the wine with too much Cork Tannin or too much air.


Cork Tannin Astringency - it’s a bigger problem than you think!


Contact: Dr Gregor Christie
               Text +61 410717081

*time equivalence based on surface area and ppb based on mg of ellagitannins expressed as mg of ellagic acid extracted into 750 ml of wine.

S. Varea, M.C. Garcia-Vallejo, E. Cadahia, B. Fernandez de Simon “Polyphenols susceptible to migrate from cork stoppers to wine” Eur Food Res Technol (2001) 213:56–61


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