Evolution of phenolic compounds of Spanish oak wood during natural seasoning. First results

Low molecular weight polyphenols and ellagitannins were analyzed by HPLC, a nd the molecular weight distribution of ellagitannins was calculated by GPC , in oak heartwood of Quercus robur L., Quercus petraea Liebl., Quercus pyr enaica Wild., and Quercus faginea Lam., grown in Spain, before and after 1 year of seasoning, in Bordeaux, France. During this process, the concentrat ions of low molecular weight polyphenols (acids and aldehydes, benzoic and cinnamic, and coumarins) increased, and those of ellagitannins (castalagin, vescalagin, and roburins A-E) decreased. A similar behavior for the A and B compounds in all species was not found. This modification in the chemical composition was similar in the four Spanish species of Quercus studied and allowed the differentiation between the unseasoned wood and the wood after the first year of seasoning.