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?
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.
extractives are solubilized into the ethanol and water matrix. The
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
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
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
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
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
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.
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.