Monday, August 6, 2012

Oak aging in easy talk

There is more to say about oak than I can fit into a post or two but much of it can be simplified and I'll try to do it here, and in some later posts.

Oaking spirits is serious business for distillers. The most common business plan for start-ups is to put out a top shelf vodka and/or gin because it's quick, while you wait for your whiskey to age in oak. Now that white or unaged whiskey is rising in popularity, this has become another immediate way to start selling spirits. The standards of identity for aged whiskies require 2-3 years in a barrel before they are complete. Obviously this makes it difficult to get a return on your investment quickly with these alone.

Here are some common questions people have about oaking spirits:

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?


...and here's the answer to the first, the rest in posts to come.

1. What does barrel aging do?

Barrel aging is a chemistry project. There are 6 or 7 (depending on whose papers you're reading) primary interactions going on in the barrel. The ones you'll hear a lot about are Angel's Share and extraction. Angel's share is loss of liquid to evaporation. It's often discussed as one of the drawbacks to aging time but it's necessary and I'll come back to that, now on to extraction.

Spirits go into a barrel somewhere between 55-62%ABV (alcohol by volume). Once in the barrel the spirit penetrates into the wood where it finds all sorts of wonderful things that are soluble in alcohol and/or water. Many of these these things are collectively referred to as phenolics due to their chemical structures or aromatics because 19th century scientists thought they smelled nice. Many of them come from lignin which is the stuff in hard woods that makes them hard. In oak, the lignin is made up of phenolics that happen to be really pleasant to the human pallet. Things like vanillin (I'll be you can guess what that smells and tastes like), guaiacol (parsley, spice), Eugenol (cloves), and whiskey lactone. Yes it's actually called that and it tastes and smells like coconut, woody, or caramel character, but it's not a phenolic, it's a lactone.

Oak extractives are solubilized into the ethanol and water matrix. The liquid then migrates back into the barrel interior bringing the flavors with. Once there they either remain in their native form or react with chemicals in the spirit. Within the spirit are fatty acids, alcohols, aldehydes, among other things many of which are very reactive. Extractives interact with these reactive spiritous elements forming larger molecules. Aging can be boiled down to a process of small slightly harsh and very volatile compounds, combining with other chemicals within the barrel. This produces an aggregate increase in average molecular weight of the components within the barrel. The larger the molecules are at the end of aging the more smooth, lingering, and pleasing the flavors and aromas will be. This is pretty simplified but works as a general rule of thumb.

Also, while the oak components are definitely a major aspect of aging, the compounds native to the spirit are reacting away as well. They are pretty volatile compounds and you can think of the volatility aspect this way; the more volatile a small molecule is the greater the speed and enthusiasm with which it will leap off of your nice warm tongue and into your sinuses. This is where the harshness of a young whiskey comes from or what people call 'the burn'. Some of it is ethanol of course, but the higher the concentration of low boiling point, markers of immaturity, the greater the burn. Within the barrel oxygen is fueling the reactions that combine these small volatile chemicals with other compounds creating the bigger molecules that are less volatile and hence, not so eager to leap off your tongue into your sinuses, and instead cling to your pallet to help produce the complex flavor and aroma profile.

Now back to Angel's share. It may not be a pleasant fact for distillers that they may lose 10-50% of the spirit they put into the barrel, depending on the barrel size, the climate, and the time in the barrel, but without that volume loss they'd never reach maturity. The volume loss concentrates all of those less volatile tasties that have been maturing away in the barrel. Don't forget that once the spirit comes out it has to be watered down to 40-45%ABV for bottling, diluting everything you've spent years producing. The concentration from Angel's share helps to ensure that the finished concentrations are high enough to create the magic.

This is the quicky primer to aging of spirits. It gives an outline of question one. I'll write more later on the other two and of course on other spirits as well.