New World Oak Shapes Old World Whisky
By Franz Scheurer
The use of ex-Bourbon barrels in the whisky industry is nothing new, as the thrifty Scots long ago discovered that the ratio of price to effect is rather favourable and most other whisky-producing nations followed suit. What started from economic necessity has become a taste standard and the use of new oak is now associated only with American whiskey.
Bourbon must, by law, be matured in new oak barrels for at least two years. After which, the barrels are sold to distilleries in Europe. Most oak for Bourbon barrels is sourced in the Ozark Mountains of Missouri, near Louisville, Kentucky (the centre of Bourbon distilling) and kiln- or air-dried for about three months. Glenmorangie’s Master Distiller, Dr Bill Lumsden, realised that a few extra steps in the barrel-making process could change the whiskies’ properties drastically, and in 1992 put a system in place, the results of which we can now taste and enjoy.
When the weather warms up in early spring, white oak trees start a growth spurt (called ‘early wood’) and then continue to grow slowly during the rest of the year (called ‘late wood’). ‘Early wood’ is porous and ideal for ageing whisky, as it allows the barrel to ‘breath’, letting air in to mature the whisky and allowing some alcohol to escape as the whisky mellows. ‘Late wood’ on the other hand is closed, tight, and less ideal for maturing whisky. The best trees for barrel making are therefore those that grow as slowly as possible during the ‘late wood’ phase, producing a ring structure with a favourable ratio of ‘early’ to ‘late wood’, resulting in a more porous barrel.
The microclimate of the Ozark Mountains allows for extremely slow growth of timber, producing just the right ring structure. Lumberjacks work in conjunction with the Missouri Department of Conservation, who mark the trees to be felled, choosing straight, mature trees ideal for barrel production. After they’re felled, a Forester selects the best trees and the wood is transported to a local sawmill, where it’s cut into stave length sections then quartered (‘quarter-sawn’) and all irregularities, such as sap and knots, are removed. The wood is then cut into staves with the grain running at 90-degrees to prevent leakage of the future barrels. From the sawmill the staves are transported to Blue Grass Cooperage in Louisville (the largest cooperage in the world) where they are air-dried for a minimum of 2 years as required by Dr Lumsden. This prolonged seasoning changes the internal structure of the wood, making it easier to extract the inherent aromas and flavours.
The seasoned staves are shaped into barrels, and those destined for Glenmorangie are lightly ‘toasted’ (exposed to fierce heat to char the inside of the barrel) for 30 seconds, whereas all others are far more heavily toasted (for 2 minutes). The toasting on Glenmorangie’s barrels still penetrates 2cm into the wood but never burns the wood sugars, preventing unnatural colour build up and any hint of bitterness. The barrels are then filled with ‘new make’ spirit at Jack Daniel’s Distillery and, after 3 years, emptied and shipped to Glenmorangie in the Scottish Highlands. Again Glenmorangie does things a little differently, shipping whole barrels to maintain their integrity, rather than breaking them down for shipping and reassembling them in Scotland as is normal practice.
In Scotland, they’re filled with Glenmorangie new spirit and matured for 10 years or more. The entire process adds a hefty price tag to each barrel, but these artisan barrels also make the difference when the resulting whisky is finally blended, bottled and enjoyed. Mid-2008 Glenmorangie will release Astar (Gaelic for ‘journey’), a whisky made exclusively from these special barrels. It will be bottled at cask strength and having tried some early samples, there’s no doubt in my mind that this will be a very special whisky indeed.
(Franz Scheurer travelled to Louisville and the Ozark Mountains as a guest of Glenmorangie, Scotland and Moet Hennessy Australia)