Cork clay

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Cork taint , cork taint , corked , short cork , also Stoppler in Austrian or pins in the Swiss, referred to in the language of wine an odor - and off flavors of wine , the most on the closure of the wine bottle, the cork goes back. This externally registered wine error is perceived differently from person to person and leads to smell and taste notes that change the aroma of the wine and can impair or destroy its taste .

Structural formula of 2,4,6-trichloroanisole

The most common cause of corkon is the occurrence of a phenol derivative, 2,4,6-trichloroanisole (TCA). The olfactory experience perceived is often not only due to the odor triggered by trichloroanisole itself, but also to the declining olfactory perception of other aromas. For TCA, the formation of olfactory signals in the odor sensory cells (olfactory cells) already interfere in very low concentrations, also reduces other odors whereby a smell or is temporarily suppressed. Then only a flattened and changed profile is perceptible, which is missing some odor notes.

The occurrence of trichloro anisole has long been due to the bleaching of the punched raw corks with hypochlorous compounds, e.g. B. potassium hypochlorite or Javel water , recycled. In the meantime, the corks are mostly bleached hypochlorite-free with hydrogen peroxide , without the frequency of occurrence of the corkon having been significantly reduced.

The formation of 2,4,6-trichloroanisole can already take place on the tree and can be traced back to various causes. One possible cause is bushfires, which are relatively common in the south of the Iberian Peninsula , where most of the cork oaks grow, and which can lead to the formation of 2,4,6-trichlorophenol in the cork bark . 2,4,6-Trichlorophenol is toxic to many organisms at a correspondingly high concentration and can be converted by microorganisms into the less toxic and more volatile 2,4,6-trichloroanisole by methylation .

We investigated furthermore the conversion of chlorophenol-containing fungicides , in particular of the previously widely used in wood preservatives used pentachlorophenol , the biodegradation by microorganisms. The highly toxic 2,3,4,5,6-pentachlorophenol (PCP) is also converted to 2,4,6-trichloroanisole (TCA) via 2,4,6-trichlorophenol (TCP) as an intermediate product. Therefore serving EU -wide ban on pesticides in cork oak forests also help prevent TCA in food. Furthermore, with the pentachlorophenol prohibition ordinance from 1989, the placing on the market of products with a content of more than 5 mg / kg PCP was prohibited. In relation to the mass of a conventional 20 mm thick, 4 cm short and 6 g weighing cork made of natural cork, this would correspond to a load of more than 30,000  ng PCP. Contaminated corks could thus bring a natural product into disrepute.

However, TCA can also be formed in other ways and then not only transported by cork. TCA has also been detected in coffee , beer , mineral water and other luxury foods and foods. Plastic closures, carpeting, filtration media and other products contaminated with TCA were also identified. Exposure to TCA as a result of environmental pollution has even been found in groundwater .

After closing the wine bottle with a cork that contains a significant amount of TCA, part of the TCA migrates into the wine within a relatively short time (a few hours to 14 days). TCA has a very low odor threshold of around 2  ng / m³ equal to 2  pg (= 2 · 10 −12  g) per liter of air and is suitable for experienced wine tasters, but also for consumers from a concentration of 1–3 ng / l (billionths of a second) Grams per liter) in white wines and from 5 ng / l in red wines. With coffee, on the other hand, quantities of more than 10 ng / l are often barely noticed.

In addition, a number of other substances can be responsible for a smell called corkon (e.g. 1-octen-3-ol ). The description of the missing tones ranges from woody to musty. Bromophenols, for example, can hardly be distinguished from TCA from a sensory point of view.

Alcohol and low temperatures can hide deficiencies in wine. If there is any doubt as to whether it is a cork tone, the wine should be diluted with water, if necessary also slightly warmed.

Web links

Individual evidence

  1. ↑ a b c Eva Derndorfer: Wine Sensory. From science to practice. Österreichischer Agrarverlag, Vienna 2009, ISBN 978-3-7040-2348-3 , p. 110 f.
  2. ↑ Hans Tanner, Carla Zanier: Experiences with bottle closures made from natural corks. In: The wine economy. 114, 1978, ISSN  0723-1369 , pp. 608-613.
  3. ↑ Corking wine suppresses the sense of smell. Der Standard, September 16, 2013, accessed September 19, 2013 .
  4. ↑ Hiroko Takeuchia, Hiroyuki Katoc and Takashi Kurahashia: 2,4,6-Trichloroanisole is a potent suppressor of olfactory signal transduction. PNAS, August 15, 2013, accessed September 19, 2013 .
  5. ^ For example, a study result published by the "Arbeitsgemeinschaft Ökologischer Forschungsinstitute eV (AGÖF)" (article by the Arguk environmental laboratory, Oberursel / Ts, overview ), accessed on May 14, 2013.
  6. ↑ O. Ezquerro, MT Tena: Determination of odor-causing volatile organic compounds in cork stoppers by multiple headspace solid-phase microextraction. In: Journal of chromatography. A. 1068, 2, 2005, ISSN  0021-9673 , pp. 201-208, PMID 15830925 .