Woodn't It Be Nice? - Part One
By F. Paul Pacult
Member Bourbon Hall of Fame
The raw, flowery smelling, crystal clear grain spirit that is pumped into oak barrels doesn't legally become bourbon whiskey until it's spent a minimum of two years resting in wood. Well, why wood? Why oak, for that matter? And further, what if the new spirit was placed in glass or steel containers or aluminum kegs or spruce barrels rather than oak barrels for its legal period of maturation? Consumers frequently ask me practical questions like these at tasting events. Fact is, they are all logical queries. Let's click them off one at a time.
Distillers and winemakers around the world centuries ago figured out that some grain and grape spirits and almost all red wines mature best in wood casks. The reasons are simple. Top grade spirits, like grain-based bourbon whiskey or grape-based cognac, are far more palatable after they've quietly relaxed in wood barrels for a spell. When the wood's acids, mostly tannin and lignin, mingle with the clear, high-alcohol spirits, the rough edges of the spirit, or spikes as some distillers call them, get smoothed out and the spirit becomes mellower. Also, because wood is porous, a small amount of air invades the barrel and affects the spirit in positive ways. Fine spirits require some contact with air in order to gracefully mature and evolve.
Oak is the wood of choice for the overwhelming majority of spirits and wine aging across the globe because it possesses the right amount of porosity. In other words, oak's grain pattern allows just the proper amount of air into the barrel at just the correct rate for fine spirits to evenly and gradually mature. Other types of woods are either too porous or too dense in their make-up, letting in either too much or too little air for adequate maturation.
Last and obviously, hermetically sealed vessels such as glass, steel or aluminum kegs aren't used for aging fine wine and spirits because they prevent all transfer of air. This means automatically that the wine or spirit wouldn't change or improve with age at all. In other words, the spirit trapped in an aluminum keg would be the equivalent of moonshine (a k a, white dog, smash skull), the harsh-tasting grain-based spirit that hasn't been matured in oak barrels. It's the same as raw spirit taken straight from the still, which, while intriguing, is hardly drinkable.
Oak barrels, then, are the major difference between what makes moonshine and what makes fine straight bourbon whiskey. Next time, we'll discuss why some bourbons, like those considered as "small batch", just keep getting better while aging in oak barrels.
Cheers, my dears. Paul