Friday, February 26, 2010

Aging Gracefully

"I like my whisky old and my women young"
- Errol Flynn

The recent discovery of three crates of one hundred year-old whisky left in Antarctica by Ernest Shackleton provides the perfect backdrop to a posting about age and whisky.

It's a pretty common misconception in the whisky world that older is always better. Age is often thrown about as a measure of the quality in the same vein as karats of a diamond, but the reality is slightly more complex. Although age will definitely induce change in a whisky, it will not necessarily improve it. Increased age will generally be reflected in the price, at a near exponential rate with higher ages (30+ years) but that is more due to its scarcity than overall quality of the product. As a discerning whisky drinker, it is important to understand why whisky is aged so that you can judge the potential effects of extended aging.

There are different laws governing how whisky must be aged, but for Scotch whisky it must be aged for at least 3 years in oak casks (in Scotland) for it to be called scotch. If you ever have the opportunity to sample raw spirit from the still before it is introduced to a cask, it will become immediately obvious what a difference even 3 years of aging makes. The raw spirit is nearly colourless and very harsh, with more of a chemical aspect to it, although very sweet. If you know anyone who makes moonshine, it is essentially raw spirit unless they do their own aging in casks. So how does storage within a wooden cask allow the whisky to mellow?

The wood in the cask is porous, and this allows many of the more volatile elements in the whisky to evaporate as they pass through the wood. Unfortunately, not all of these volatile elements are undesirable, so you lose some good alcohol (ethanol) along with some of the bad alcohols (like methanol). This lost volume of ethanol, affectionately called "the angel's share", amounts to roughly 3% of the alcohol volume per year. While 3% may not seem like such a dire loss, you can imagine how much the lucky angels have taken out of a cask after 40 years! This is a contributing factor to the scarcity of older whiskies and why the price rises so much with age - there is less volume to sell and the distillery is losing more product the longer it sits in the warehouse. Other chemicals are also being lost through the wood. Lighter, more volatile compounds are lost before heavier oily ones. The esters which contribute to the fruity and floral aromas of the whisky are harder to retain than the heavier smoke and peat flavours and aromas.

The wood doesn't just steal, however. it also adds its own special touches to any whisky aging inside, which is why wooden casks are still used after hundreds of years. As the whisky penetrates into the pores of the wood, other chemical reactions take place as it reacts with compounds in the wood. The products of these reactions can leach into the whisky and imbue it with their own special flavours: vanilla, nuts, oak, and butter, for example. The use of wooden casks that have previously held sherry, port, bourbon, or other wines and liquors results in "special finishes", where aspects of the previous occupant (such as colour and flavour) will influence the aging whisky. Just pick up a bottle of something like the MacAllan Fine Oak and compare it to their standard sherry-finished expressions to appreciate the influence wood and casking can make (see the Wood, Wine and Whisky posting).

To much aging in a cask can mellow a whisky too much, however, muting its character. This is why distillery managers are always sampling whisky from aging casks and making important decisions about when to bottle the contents. Whiskies known for their particularly strong flavour characteristics can lose these over time. Aging Ardbeg, for example, brings out some of its more subtle flavours, but too much time and mellowing and it can cease to be recognizable as Ardbeg. Whisky reviews of old bottles (30+ years) will often comment on the extent to which it has retained its traditional character. Ideally, old whisky should keep some of its youthful perkiness while adding smoothness and grace. Just like people!

My father-in-law once boasted to me that he had a bottle of 30 y-o Chivas Regal, then proceeded to show me a bottle of the 12 y-o blend that had been sitting in his liquor cabinet for roughly 20 years (unopened). This is another common misconception about aging of whisky, and I think it must be due mainly to the popularity of wine and wine aging in the bottle. Once whisky is removed from the wooden cask and placed within a corked glass bottle, it is essentially inert, or frozen in time. The glass bottle has none of the porosity of the wooden cask and will not react chemically with the whisky (to any significant degree) with the whisky, so it will not change within the bottle. This has been observed for many old unopened bottles which have been sold in auctions and subsequently sampled. Once a bottle is opened however, it is the presence of air within the bottle which allows for evaporation and can react with the whisky. This brings me back to the lost "Shackleton Reserve". A large measure of the excitement over these bottles is the fact that some of them are unopened, intact, well corked and are therefore expected to be essentially the same as when they were bottled more than a hundred years ago.

One of the great benefits of drinking whisky relative to wine is that you can keep an opened bottle on the shelf for an extended period of time, dipping into it occasionally before it begins to diminish in quality. There is currently some debate over the extent and rate at which air will start to degenerate the quality of the whisky in a bottle. I tend to look at it in terms of how much air is present within the bottle that can react with the liquor: More air in the bottle means more reactions with the whisky. Some people, as a rule, will try to finish a bottle within a year of it first being opened. I try to finish it within a year once it is below half its original volume within the bottle. The more times the bottle is opened, the more air is exchanged and that will speed up the degeneration. You can experiment with your own whisky stocks to see how they change over time, but the important factors when thinking about whisky changing in the bottle are 1) presence of air 2) time 3) light (in that order of importance).

If you are really concerned about your favourite bottles, there are several tricks to help stave off the ravages of air and time: 1) Transfer remaining whisky to smaller bottles (therefore less air) 2) Displace the oxygenated air within your bottles and replace it with a more inert gas, like nitrogen (yes, people do this!) 3) Put clean glass marbles in the whisky bottles to displace the air. I'm pretty confident that all of these tricks work, but personally I'd rather just finish the whisky!

Sir Ernest Shackleton's Imperial Trans-Atlantic expedition may have ended badly, losing the good ship Endurance in the process, but I'm glad he decided to bring along some Scotch whisky. It will be a great test for whisky preservation in bottles, provides a glimpse of what whisky was like a hundred years ago, and gives a whole new meaning to Scotch on the rocks!

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