heartwood solids are cell-wall molecules,
cellulose, hemicellulose, and lignin. These are
mostly insoluble, but the lignins can be partly
broken down and extracted by strong alcohol,
and all can be transformed into new aromatic
molecules when the wood is heated during
barrel making (p. 449).
Coopers rely mainly on two European oak
species (Quercus robur and Q. sessilis), and
ten North American species, the most
important being the white oak (Q. alba). The
European species are mostly made into wine
barrels, American oak into barrels for aging
distilled spirits. American oak tends to have
lower levels of extractable tannins and higher
levels of the oak lactones and vanillin.
Making Barrels: Forming and Cooking In
order to make barrels, the cooper splits the
heartwood into pieces, dries them, and forms
them into thin, elongated staves, which are
then roughly hooped together and heated to