'Cork taint' in new barrels
Following an increasing number of observations in various wineries around the world in recent years, it is now clear that, similarly to the well-known phenomenon in corks, there are several sources of unpredictable contamination of oak wood by 2,4,6-trichloroanisole (TCA). TCA from the wood then contaminates wine aged in new barrels, giving it an extremely unpleasant, musty "cork taint" and polluting the entire blend unless it is detected at a very early stage!
The first results obtained by Laboratoire EXCELL, illustrating this discovery, will soon be published in the prestigious Journal of Agricultural and Food Chemistry. In this work, the EXCELL researchers demonstrated that TCA affected staves in the same barrel very sporadically, with extremely limited polluted areas on the surface that could reach several millimeters in depth. The precise origin of the TCP and TCA in oak wood is not known at this stage. The data presented indicated that the phase where stavewood was naturally dried and seasoned was the source of these undesirable organochlorine contaminants. It was demonstrated that the strictly chemical formation of 2,4,6-trichlorophenol (TCP), derived from organochlorine biocides, was impossible under traditional cooperage conditions and its accumulation remained highly improbable. Similarly to previous discoveries in corks, all the analyses of oak wood suggested that the TCP was of biochemical origin. The biomethylation capacity of chlorophenols is well known and relatively widespread among the usual microflora in stavewood, but the precise origin of the intermediary leading to TCP formation is still unknown. One probable hypothesis is the intervention of a highly-specific enzyme system (chloroperoxidase). Several ideas have been proposed by the EXCELL team, but the microorganisms responsible for the formation of the TCA precursor in oak wood have not yet been strictly identified. The extent of the problem is still severely underestimated by coopers and barrel-users, due to the extremely unpredictable, localized contamination of the staves. An exclusive system for testing new barrels individually (CHECK LIST BARRIQUES©, www.labexcell.com), developed and patented by EXCELL, is suitable for both cooperages and wineries and should be used systematically to guarantee risk-free barrels.
N.B.: This information was taken from an article submitted for publication in the Journal of Agriculture and Food Chemistry in 2010
Identification of a new source of contamination of Quercus sp. oak wood by
2,4,6-trichloroanisole (TCA) and its impact on the contamination of barrel-aged wines
Pascal CHATONNET*, Antoine FLEURY*, Stéphane BOUTOU* and Antonio Tomas PALACIOS**
* : Laboratoire EXCELL France Parc Innolin 10, rue du golf 33700 MERIGNAC, France
** : Laboratorio EXCELL IBERICA, Polígono Portalada II, calle Planillo 12 , LOGRONO (La Rioja) España