Pascal Chatonnet

Identification of substances responsible for the ‘sawdust’ aroma in oak wood

The unpleasant sawdustI odour sometimes found in wines aged in new barrels was studied by gas chromatography olfactory detection and mass spec- trometry. A particular aromatic zone has several chromatographic peaks, corre- sponding to certain characteristic odours which can be detected by smelling the gas effluent. These include the subtle rancid, weedy odour of sawdustI. Various carbonyl components have been identi-ed in this particular zone. These include (E)-2-nonenal, 3-octen-1-one, (E)-2-octenal and 1-decanal. These molecules are the primary cause of disagreeable oak wood odours. By measuring (E)-2-nonenal in wines, after derivation by O-(2,3,4,5-pentaNuobenzyl)-hydroxilamine (PFBOA), it was possible to correlate the concentration of this unsaturated aldehyde with the intensity of the sawdustI character noted in tasting. The possible explana- tions for the presence of these carbonyl compounds are debatable. The carbonyl content varied from one wood sample to another. However, controling the toast- ing of the wood, both in the laboratory and in the cooperage, produced a major reduction in the extractable (E)-2-nonenal content and eradicated the sawdustI character of the wine. 1998 SCI. (

Identification of a New Source of Contamination of Quercus sp. Oak Wood by 2,4,6-Trichloroanisole and Its Impact on the Contamination of Barrel-Aged Wines

Thanks to practical experience in various wineries 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 affects staves in the same barrel very sporadically, with extremely limited contaminated areas on the surface that may reach several millimeters in depth. The precise origin of the TCP and TCA in oak wood is not known at this stage. Available data indicate that the phase where stavewood is naturally dried and seasoned is the source of these undesirable organochlorine contaminants. The strictly chemical formation of 2,4,6-trichlorophenol (TCP), derived from organochlorine biocides, was demonstrated to be 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 capacity to biomethylate 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 that this reaction involves chloroperoxidase (CPO). Several ideas have been proposed, but the microorganisms responsible for the formation of the TCA precursor in oak wood have not yet been identified. The extent of this problem is still severely underestimated by coopers and barrel-users, due to the extremely unpredictable, localized contamination of the staves.