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Cork taint
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Cork taint
Cork taint is a broad term referring to an off-odor and off-flavor wine fault arising from the presence in the cork of aroma-intense compounds that are transferred into wine after bottling.
Cork taint is characterized by a set of undesirable smells or tastes found in a bottle of wine, described as "musty", "mouldy", "earthy", or "mushroom". It causes losses to the industry (the estimated share of affected bottles is between 1% and 5%), and can destroy the reputation of a winery that is particularly unlucky (in rare cases up to a third of the bottles can be tainted). A wine found to be tainted on opening is said to be corked or "corky".
Not every contaminant in the cork is considered a "cork taint": for the issue to be classified as such, the problem should be caused by a compound introduced due to normal cork processing or forming in the cork naturally (for example, external naphthalene contamination during transportation is excluded). There are multiple sources of cork taint, but the 2,4,6-trichloroanisole (TCA) is by far most prevalent, with estimated 80-85% of all cork taints due to TCA. Occasionally, the same compounds found in the wine are not there due to the cork, but actually are introduced before bottling from the grapes, wooden barrels, and processing equipment.
The role of TCA in tainting the foodstuffs is known since at least 1970s. In 1982, Buser et al. identified TCA as a compound causing the cork taint. TCA is studied in detail and considered to be the main source of the issue (in some surveys, the TCA was present in all the bottles assessed to be tainted). Humans are very sensitive to the presence of TCA, with some experts capable of detecting the levels as low as 1-2 ng/liter, and a specially trained group reported to achieve a threshold of 0.3 ng/L. Individual sensitivity greatly varies, with some experts' threshold at 250 ng/L, while some assessors unfamiliar with the TCA odors were able to detect the problem only at mg/L levels.
In side-by-side comparisons for white wines, one panel had shown preference for non-corked wines at the level of 20 ng/L of TCA, while another study found the "rejection threshold" to be between 3.1 and 3.7 ng/L.
The primary chemical precursor to TCA is 2,4,6-trichlorophenol (TCP).[citation needed] Bacteria are able to de-toxify TCP, notably Pseudomonas and Stenotrophomonas, but both strains cannot de-toxify the TCP without the other.[better source needed] Chlorinated phenols can form chemically when hypochlorous acid (HOCl, one of the active forms of chlorine) or chlorine radicals come in contact with wood (untreated, such as barrels or pallets).[citation needed] The use of chlorine or other halogen-based sanitizing agents is being phased out of the wine industry in favor of peroxide or peracetic acid preparations.[citation needed] While chlorine dioxide had shown no links to TCA formation, it was not efficient against yeasts in an in vivo study.
The cork-industry group APCOR cites a study showing a 0.7–1.2% taint rate. In a 2005 study of 2800 bottles tasted at the Wine Spectator blind-tasting facilities in Napa, California, 7% of the bottles were found to be tainted.
In 2013, the Cork Quality Council ran over 25 thousand tests. The results, compared with data from eight years before, showed a sharp reduction in TCA levels, of around 81 percent. In the last test, 90 percent of samples of natural cork stopper shipments showed values of under 1.0 ppt and only 7 percent showed results of 1.0–2.0 ppt.
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Cork taint AI simulator
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Cork taint
Cork taint is a broad term referring to an off-odor and off-flavor wine fault arising from the presence in the cork of aroma-intense compounds that are transferred into wine after bottling.
Cork taint is characterized by a set of undesirable smells or tastes found in a bottle of wine, described as "musty", "mouldy", "earthy", or "mushroom". It causes losses to the industry (the estimated share of affected bottles is between 1% and 5%), and can destroy the reputation of a winery that is particularly unlucky (in rare cases up to a third of the bottles can be tainted). A wine found to be tainted on opening is said to be corked or "corky".
Not every contaminant in the cork is considered a "cork taint": for the issue to be classified as such, the problem should be caused by a compound introduced due to normal cork processing or forming in the cork naturally (for example, external naphthalene contamination during transportation is excluded). There are multiple sources of cork taint, but the 2,4,6-trichloroanisole (TCA) is by far most prevalent, with estimated 80-85% of all cork taints due to TCA. Occasionally, the same compounds found in the wine are not there due to the cork, but actually are introduced before bottling from the grapes, wooden barrels, and processing equipment.
The role of TCA in tainting the foodstuffs is known since at least 1970s. In 1982, Buser et al. identified TCA as a compound causing the cork taint. TCA is studied in detail and considered to be the main source of the issue (in some surveys, the TCA was present in all the bottles assessed to be tainted). Humans are very sensitive to the presence of TCA, with some experts capable of detecting the levels as low as 1-2 ng/liter, and a specially trained group reported to achieve a threshold of 0.3 ng/L. Individual sensitivity greatly varies, with some experts' threshold at 250 ng/L, while some assessors unfamiliar with the TCA odors were able to detect the problem only at mg/L levels.
In side-by-side comparisons for white wines, one panel had shown preference for non-corked wines at the level of 20 ng/L of TCA, while another study found the "rejection threshold" to be between 3.1 and 3.7 ng/L.
The primary chemical precursor to TCA is 2,4,6-trichlorophenol (TCP).[citation needed] Bacteria are able to de-toxify TCP, notably Pseudomonas and Stenotrophomonas, but both strains cannot de-toxify the TCP without the other.[better source needed] Chlorinated phenols can form chemically when hypochlorous acid (HOCl, one of the active forms of chlorine) or chlorine radicals come in contact with wood (untreated, such as barrels or pallets).[citation needed] The use of chlorine or other halogen-based sanitizing agents is being phased out of the wine industry in favor of peroxide or peracetic acid preparations.[citation needed] While chlorine dioxide had shown no links to TCA formation, it was not efficient against yeasts in an in vivo study.
The cork-industry group APCOR cites a study showing a 0.7–1.2% taint rate. In a 2005 study of 2800 bottles tasted at the Wine Spectator blind-tasting facilities in Napa, California, 7% of the bottles were found to be tainted.
In 2013, the Cork Quality Council ran over 25 thousand tests. The results, compared with data from eight years before, showed a sharp reduction in TCA levels, of around 81 percent. In the last test, 90 percent of samples of natural cork stopper shipments showed values of under 1.0 ppt and only 7 percent showed results of 1.0–2.0 ppt.
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