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A question of technique, TCA, but how much?

Wine producers also state an excessive percentage of wines that are ‘corked’. The use of cork stoppers is questioned because they are one of the causes of TCA (trichloroanisole) in wine, which then becomes a "corked" wine.

TCA is the most dangerous metabolite responsible for the unpleasant odours and flavours that can be found in wine. There is a risk of biological contamination by substances given out by the stopper or wood, leading to the formation of TCA.

Human beings are very sensitive to this substance and 4 nanograms/litre are sufficient to allow its detection; the equivalent of one soup spoon in 2000 Olympic swimming pools.
But how many bottles are actually affected by this phenomenon? There are cellars who believe the use of cork brings with it a certain level of uncertainty, even if the occurrence percentages are, generally, minor.

According to WWF, an international environmental NGO, these are between “0.5% and 0.7%”. Also according to WWF, cork is not the sole responsible, TCA can originate from other sources: barrels, pallets or contaminated bottles; bad bottling or corking practices; contamination from the environment of the cellars themselves.
However, there have been campaigns in the media with widespread repercussions which hold cork responsible for the unlikely percentage of bottles that present a defect from a sensory perspective.

A very high percentage is announced, for example, by Rodolfo Gaona, “The reality, with which we are all acquainted with, those who drink wine daily, is that this percentage is dramatically higher than 5%”. Alain Marty, president of the Wine & Business Club, states that “it represents between 2 and 8% of wines consumed. This is considerable.” Stéphane Queralt goes even further: “You will perhaps be surprised to learn that 10 to 15% of wines with cork stoppers are affected by the cork... Some believe that on average one bottle per wine case (12 bottles) is affected by infected cork”.

António Amorim, President of the European Cork Federation, considers that “a sector with such an amount of affected bottles could not survive. In fact, the percentage of complaints is definitely lower. At Amorim, for years, the percentage affected is much under 1%”.

The reaction in the industry also manifested itself with an intense research and innovation campaign. The research group of Raul Cabral, who work for the Amorim group, studied three methods: ozone, vacuum and steam. The latter showed a remarkable efficiency with a TCA elimination rate of 90% in tests. Another method, technologically advanced, originating from an INETI patent, uses gamma radiation to break down the molecule transforming it into residues with no unpleasant odour. One factory of the Oeneo group uses a process of TCA extraction which relies on supercritical CO2. This is a technique already used to extract caffeine from coffee grains or perfumes from aromatic plants...