| Abstract
| - The chemical composition of cooperage oak wood is highly variable, depending upon the tree species(Quercus robur L. versus Quercus petraea Liebl.), its geographic location, and the single-tree effect.In the process of cask-making, natural seasoning and toasting contribute strongly to the modificationof the oak wood chemical composition and therefore influence wine cooperaging. HPLC and GCquantification of ellagitannins and volatile compounds such as whiskey-lactones, eugenol, and vanillinover a sample set of 61 pedunculate oaks and 72 sessile oaks originating from six different forestsshowed that natural drying leads to a decrease of the ellagitannins and total extractives content leveland a quasi constant level of the volatile compounds. Toasting (medium type) drastically enhancedthe loss of ellagitannins and the gain in volatile compounds. Statistical treatment showed that thespecies effect remained significant throughout the process of drying and toasting, but not theprovenance. The poor correlation with ring width of extractives levels measured on fresh timberremained unchanged as did the single-tree effect, with high variability found for all chemicalparameters. These results provide further evidence that cooperage oak selection should not be basedsolely on the wood grain or the provenance but rather on a species−provenance combination. Keywords: Oak; extractives; Quercus robur; Quercus petraea; seasoning; toasting
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