The oldest oak tree alive today is over 2000 years old, key constituents exist within the wood of these trees to ensure its long term preservation, preventing rot, maintaining structure and supporting a healthy ecosystem. This is even more remarkable when you consider that the outer bark is essentially the “living” part of this organism. So what exactly stops the tree from rotting after a decade or a century later?
Wood contains potent congeners, tannins and phenols that are naturally designed to prevent oxidation and ageing.
The 5 core wood congeners provide the building blocks of protection and flavour
A sugar based polymer composed of glucose and multiple sugars which break down into their individual parts when stimulated by dramatic changes in their environment such as heat. It is these newly activated by-products which provide the deep brown colors and subtle almond, walnut, butter and maple notes from a lightly toasted cask and higher of toasting providing rich caramel and toffee.
Lignin is also a polymer and is composed of two core structural parts, guaiacyl and syringyl. It is the direct result of these combined parts, which is responsible for giving us sweet and spicy aromas, especially vanilla. Lignin congeners can be released very easily with only the smallest amount of activated heat however, it’s the effect of heavy toasting and deep charring which break down the lignin further into steam volatile phenols responsible for delivering smokey flavour elements.
A small element of tannin is required to supply oxidization and fragrances like cooked apple. More importantly however is the role tannin plays on long maturation. The wood chemical reacts slowly with the oxygen molecules in the spirit, over time creating a new compound called diethyl acetal. This new compound ensures that a 20+ year old Scotch or Cognac for example, is left with rich and complex top-notes and not flat and insipid.
Lactone is a flavor element influenced by certain oils, soluble fats and waxes simply known as lipids which deliver a unique coconut-woody taste to a spirit. Almost all flavor attributes are released in the first year of barrels’ maturation.