Tuesday, September 27, 2011

Oak aging, 3 of 200

The three questions I set out to answer first:


1. What does the barrel aging do?
2. If oak is good why not try other woods?
3. Is there another way to age whiskey faster?


I've covered the first two a bit, now on to the third. I'm thinking this could take a couple of articles but here's a first stab.

During aging there are two primary processes taking place: Extraction and Reaction.

Extraction


The first thing taking place in a barrel is material being pulled out of the wood and into the spirit. The compounds that are pulled out come from lignin (the stuff that makes wood brown and hard) as it breaks down during the seasoning and cooking of barrel staves. These compounds are called phenolics because of their basic chemical structure, which consists of an aromatic ring and any number of things attached to it. The phenolic or aromatic ring is a 6 carbon ring with a bunch of electron sharing going on between the carbon atoms. They are called aromatic rings because as they were being isolated in the nineteenth century they all smelled really nice. The compound below is called phenol, which means phenolic ring with an alcohol hanging off of it (OH).


Reaction

Once you've got some phenolic extracts into your spirit, they start to interact with the compounds in the whiskey or brandy. The list of interactions between compounds inside a barrel follows.

1. Interaction between barrel extract and spirit compounds
2. Interaction between barrel extract and each other
3. Interaction between spirit compounds with each other

These interactions can basically be summarized by saying that small compounds combine producing larger compounds. This is important for a few reasons. One big one is that many of the larger compounds being produced are esters. Esters have lovely flavors and aromas. They are used to flavor gum, candy, and many food products with fruit or flower-like characters. Another reason this is important is that the larger compounds are less volatile. Highly volatile components are what make a young spirit "hot" or burn your mouth. When they combine and the volatility goes down, the spirit becomes smoother and kinder to your sensitive pallet.

I've already talked about Angel's Share and what it does in terms of concentration of flavors and aromas and that it is important for the aging process.

So back to the question of speeding up aging. Aging time for most barrelled products in a standard 55 gallon barrel is a minimum of 2-3 years. Many spirits are aged longer and in most cases, the longer it's aged the higher quality it is, therefore more expensive, and more rare. Two years is really a minimum and even spirits labelled as two year are often blended with older spirits.

To speed up aging you have to speed up two things because Aging = Extraction + Reaction. Extraction is easy to speed up. A small barrel, oak chips in a barrel or some other oaking product will add a bunch of extract fast. At that point we encounter a problem.

The natural process of aging is an oxidation process. Oxygen, which slowly creeps into the barrel, fuels the production of the compounds that give the spirit mature character. Oxygen comes in, gets consumed, reactants are produced, oxygen is replaced, etc. The rate at which this happens is pretty ideal in a barrel and oxygen gets into the barrel slowly. When they try to drive this forward in the wine industry they pump O2 into 15,000-20,000gal tanks in units of Liters of O2/month (very little, very slowly). This is because when you oxidize something fast you can make a bunch of stuff you don't want and that tastes and smells bad. In the case of spirits you could easily catalyze reactions that produce off flavors, or produce way too much of the stuff that's good in small amounts, I've done it.

There are any number of other tricks that could be used to catalyze these reactions faster. Some people use subwoofers utilizing sound energy (they say) to move the reactions faster. I've spoken with people who wanted to use pressure, there's a company using ultra-sound, and I've tried any number of tricks myself in the lab. In the end, the largest distilleries in the world making many very fine, world class spirits, are using time. Not time machines, just plain old time.

To put this in perspective these companies have millions of dollars at their disposal, large well equipped laboratories, teams of R&D scientists, and lots of spirit to experiment with, and they continue to use the traditional method. I'll not say that it's not worth trying other things but I will say that many of the shorter aged spirits coming out of the artisan industry just aren't well aged. Some of them are interesting but it's rare to find a spirit coming from a small producer that has been aged to maturity. It's fine to bottle a young spirit as long as you call it that.

Extraction + Reaction.

I'll write about tasting spirits at some point but one of the major marks of a finished spirit is that when you taste it, the experience goes on for a while, and I mean up to 30 seconds or longer. This is because those larger molecules coat your pallet. Many of them are fatty acids and their esters so they can be downright oily. That coating allows volatile compounds to slowly evaporate into your sinuses where most of the "tasting" actually happens. Without this dynamic the experience is too short, flat and unfinished.

So there's question 3. I'll have to go into this more but I think this serves as a starting point. It's one of those things I could just keep writing about for the rest of the day.

Good Spirits!