What happens to the wood?

[cowdery]

We talk a lot about aging and about the affect of wood on whiskey, but let's approach it a different way. What is the affect of whiskey on wood? I'm interested in what happens to new wood (i.e., bourbon aging) as well as what happens to old wood (i.e., scotch aging). Do changes that occur in the wood over time, either naturally or through its contact with whiskey, alter the way it ages whiskey later in the barrel's life?

For example, we know bourbon penetrates the wood and dissolves partially carmelized sugars and other substances such as lignin. What percentage of these substances are extracted from the wood after one year, five years, ten years, etc., and how does this affect the wood? Are any substances completely depleted in the early years, so they would be present in bourbon but never in scotch? Are there other substances that only become available later in the barrel's life?

No speculation please, just facts.

[Gillman]

Well, one effect of whiskey on wood indubitably is to leach out its tannins. Tannins, an amazing natural preservative, keep wood intact and free from bacterial and other degradation. As tannin leaves wood, the wood starts, quite literally, to rot. This is why some whiskey is musty. This why, too, artificial cycling, especially if effected too quickly, may prematurely deplete wood of its tannin and spoil the aging whiskey - even whiskey just 4 or 5 years old. My source: Charlie Thomasson, old-time, practical distiller of Willett's, writing in the 1960's.

Gary

[cas]

I don't have any special insights, just a related question. I suspect barrels have been made from oak for it's structural integrity. But have any other woods ever been used to age whiskey - maple or ash, for example?

Craig

[Gillman]

Sappy woods are not suitable, even oak needs to be dried properly to avoid sap leaching into the whiskey (or too much). As early as 1810 or so white oak had been identified as the best wood for whiskey. Samuel M'Harry's book of that era lists white oak first, then black oak, then a series of other woods in declining preference.

Gary

[tdelling]

There's also the issue of porosity... many woods just can't hold water,

and are only suitable for "dry cooperage". White oak is one those

that doesn't leak like a sieve.

I have heard stories of a couple small European (Scandanavian?) distilleries

using woods other than white oak, but can't recall the details. In my

recollection, they're the only ones in the world doing it these days.

Tim Dellinger

[tdelling]

It looks like you've been bitten by the bug that gives otherwise

rational people an intense curiousity concerning the complex and mysterious

chemistry of whiskey! Just a few warnings:

1) It gets more and more interesting the deeper you look.

2) People will accuse you of ruining the magic and trying to synthesize

whiskey from chemicals and taking the fun out of it. Little do they know

that exactly the opposite is true.

Anyway, those are some big questions you've asked, and I'll have to have a

look through my "library" a bit to give you referenced answers.

In the meantime, a few tidbits that I've been meaning to dig deeper into,

but haven't yet:

1) Musical instrument makers will tell you that wood will actually degrade

*in air*, and will measurably lose weight. They also have a few things to

say about this phenomenon's effect on the sound of the guitar/violin/etc.

So it doesn't take liquid to change wood!

2) In Scotland, they will sometimes "rejuvinate" barrels by scraping out

the insides, often with flailing chains that spin around and smash into the

staves of the barrel. They also re-toast sometimes. Both of these practices

are to "fix" barrels that "used up". All of this gives clues as to what makes

a barrel useful.

3) Oh, and a warning: whiskey people are traditional, and they also don't

spend gobs of money on detailed research... and the stuff you do find is

more likely to be Scotch than boubon. I've found myself spilling

over into wine barrel research, cognac aging, etc., as well.

Tim Dellinger

[Hedmans Brorsa]

I have heard stories of a couple small European (Scandanavian?) distilleries

using woods other than white oak, but can't recall the details. In my

recollection, they're the only ones in the world doing it these days.

Tim,

The Mackmyra distillery in Sweden, who has yet to offer a commercial product, matures some of their stock in new Swedish oak. They claim to be the first one ever to do so.

Unfortunately, I am not a botanical man so I cannot claim to possess any intimate knowledge of Swedish oak but I´ve always regarded it as white. I could be dead wrong on this one, though.

There is also a new distillery in Lahti in southwestern Finland. I know nothing about their production schemes, I´m afraid, but I have never heard of any "exotic" barrels being used.

[dougdog]

Headmans,

The botanical "Quercus" or "Oak" family is a large one. There is almost positively a "white oak" that would only/predominantly grow in Sweden and the locals would likely find that tree when searching for something unusual to use in a distillery wood/barrel/cask program. I'd bet if you contacted the distillery and asked around a bit you could get the exact "species/variety" name.

Oaks are so varietal/varied because they cross hybridize quite easily. This would lend to the concept that "local wood" would have its' own unique influence on the spirit being barreled. There is, after all, American oak, French oak, Spanish oak and Scottish oak being widely used in barrel/cask programs around the world...why not Swedish oak?

Now, if we could just get someone in the bourbon industry to lay up some white dog in some of those barrels for a taste in a few years...let's say...Sampler at the Gazebo 2010 as a 4 year old. (Then in 2020 as a 14 year old)

Certainly there would be annual progress samples distributed for "research/documentary" purposes, right?

dougdog

[cowdery]

Buffalo Trace has laid up some bourbon in French oak, and shared tastes of it widely although no product has been released. When a group of us were given a taste a couple of years ago, we all knew we were tasting something different but couldn't put our finger on it. Then Marvin Franz said, "this isn't American wood." And he was right.

Great taster, that Marvin.

[JeffRenner]

The botanical "Quercus" or "Oak" family is a large one. There is almost positively a "white oak" that would only/predominantly grow in Sweden and the locals would likely find that tree when searching for something unusual to use in a distillery wood/barrel/cask program. I'd bet if you contacted the distillery and asked around a bit you could get the exact "species/variety" name.

Here is a good source of information on oak used in cooperage. The link there on French oak has this pertinent information:

The most common oak in France, as throughout the rest of Europe, is the Quercus robur species (also known by the designation of Quercus pedunculata and Quercus rubra) which flourishes in a variety of growing conditions. Another important, though less common species of oak in French forests is Quercus petraea (also known as Quercus sessiliflora, Quercus sessiflora and Quercus sessilis), which has a tighter grain. ... A tighter grain not only means a less porous wood, which ensures a watertight barrel, but releases oak flavor to the wine more slowly.

The flavor of wines fermented or aged in European oak is different from that of American oaked wines. I am not sure if I could pick it out in whiskey as Chuck notes that Marvin did, but the oak flavor we are familiar with in bourbon is typical of less expensive American Chardonnays (and some more expensive ones as well, to be sure). European oak is less vanilla-ish.

Jeff

[TMH]

In Japan, Suntory uses Mizunara (Japanese Oak) for much of their barrels. I copied the following from a Suntory press release:

Suntory’s history of distilling whisky began when Shinjiro Torii, the founder of Suntory, built the Yamazaki Distillery in 1923. A first-generation master blender, Shinjiro aged the first whiskies created in Japan, mainly using Spanish sherry casks for the first 20 or so years.

With the outbreak of World War II, however, these casks were no longer easily imported from Spain, and whisky storage shifted to casks specially crafted of Japanese Mizunara wood by Suntory for 20 or more years during and after the war. Containing little tylose, Mizunara from Hokkaido and Tohoku is more prone to leaks and less pliable, characteristics which caused the craftsmen of the time a great deal of trouble. The original Mizunara casks imparted a powerful and distinctive aroma and taste to key malts stored in them, and whisky made in this manner was consumed at a comparatively young age. In the 1980s, however, whisky blenders discovered that key malt aged over long periods of time in these Mizunara casks matured into highly aromatic spirits that recalled the woody fragrance of eaglewood. In 1989, second-generation master blender Keizo Saji created Hibiki, the ultimate Suntory blended whisky, from Mizunara cask malt, and this key malt has been essential in crafting Suntory’s premium whiskies ever since. Whisky connoisseurs around the world have come to love the distinctive characteristics of Japanese whisky – namely a taste and aroma not found in Scotch – that comes from the Mizunara cask key malt.

I don't know what happens structurally to wood after being used to store whisky, but Suntory sells its finished barrels to craftsmen who then create furniture with it. I assume the wood must maintain its most of its structural integrity in order to be used in furniture.

[bobbyc]

I suspect barrels have been made from oak for it's structural integrity.

And I thought it was as simple as the white oak being a wood easily split and straight grained. Barrel making more or less predates sawmills and there was a technique called "Riving" where a flat of iron is driven into the log top to bottom and splits out little "Planks". One wonders where happy coincidences and concious thought marry to produce the end result.

[tdelling]

> We talk a lot about aging and about the affect of wood on whiskey, but let's

> approach it a different way. What is the affect of whiskey on wood?

Well, the short answer to this is that the various components of wood degrade

into complex mixtures that contain hundreds of different components.

> I'm interested in what happens to new wood (i.e., bourbon aging) as well

> as what happens to old wood (i.e., scotch aging). Do changes that occur

> in the wood over time, either naturally or through its contact with whiskey,

> alter the way it ages whiskey later in the barrel's life?

Perhaps more important than old-vs.-new wood are the effects of toasting,

charring, etc. Some people say (oversimplifying a bit) that heat treatment

breaks down the wood before the whiskey gets in there, thus speeding up

the extraction process. This is true and not true... it turns out that

charring and toasting give different wood breakdown products than just

aging... and once these are gone, you're not going to get any more without

re-toasting or re-charring the barrel. So there are things in bourbon that

won't be in scotch. I've never seen evidence for the reverse: it looks like

wood doesn't undergo "late in life" changes that would suddenly give things

to scotch that wouldn't show up in bourbon.

The thing to understand is all of these extraction/degradation/oxidation/

hydrolysis/ethanolysis/evaporation/etc processes are happening at the same

time, and sometimes interact with each other... and they don't all respond

to changes in temperature/proof/time in the barrel/etc in the same way.

So it's a huge balancing act to find the aging conditions you want.

(As an aside, the Tim Dellinger theory of "whisk(e)y terroir" is that

the geographically determined temperature and humidity that you age in

are pretty much unchangable for a given location... thus geograpically,

scotch never could have developed in america (or vice versa), even if

local tastes and availability of grains willed it to be so.)

> For example, we know bourbon penetrates the wood and dissolves partially

> carmelized sugars and other substances such as lignin. What percentage of

> these substances are extracted from the wood after one year, five years,

> ten years, etc., and how does this affect the wood?

Luckily, the cellulose doesn't really break down, so the wood is held

together. I've never seen "weight loss vs. time" data for wood being

used as a whiskey barrel... most studies take the more practical

approach:

1) All we care about in the end is what's in the whiskey

2) We're really good at analytical chemistry on liquid samples, and the

liquid sample to choose is here is obvious: just use the whiskey.

You might be able to find studies that have done extractions of the

wood after aging, but they're certainly not prominant in the literature.

I've heard anecdotal evidence that barrels will eventually lose their

structural integrity, but it doesn't seem to be a problem for rational

(i.e. less than 30 year) aging times.

> Are any substances completely depleted in the early years, so they would

> be present in bourbon but never in scotch? Are there other substances that

> only become available later in the barrel's life?

I think I hit that one earlier.

I'll give a very brief summary of the pertinant effects of the different

wood components, (lifted word for word from the anonymous conference

proceeding listed below), which glosses over the chemistry and cuts to

the chase:

cellulose: no direct effect

hemicellulose: wood sugars (body), carmelization products, color

lignin: color, increase in blended complexity, production of vanilla,

promotion of oxidation

oak tannins: promotion of oxidation, productin of astringency, removal

of off notes

char layer: burnt wood flavors, removal of off notes

> No speculation please, just facts.

For further reading:

I haven't been able to get ahold of a pdf version of the Seagram paper

"Chemical Mechanisms of Whiskey Maturation" Am J Enol Vitic 32 4 (1981),

but that's probably the most readable of the journal articles, and gives

a good overview of bourbon aging chemistry.

There's a Schenley paper called "Chamges in Whiskey While Maturing"

in Industrial and Engineering Chemistry, March 1949, p.534. It's a little

harder to read, but not too bad if you're good at ignoring the tedious

parts.

There's a pdf fairly widely available on that net that's from an anonymous

conference proceeding from one of the barrel makers, with the informal

title "A Composition of Oak and an Overview of its Influence on Maturation".

This focuses mostly on the basics of the chemistry involved, and has some

good summary graphics and explainations that make it a bit easier to

wrap your head around... with the journal articles, it's easy to get a little

lost.

Jim Swan has a writeup in the Nov/Dec issue of Practical Winery & Vineyard

that talks about really dialing in the exact flavor profile you want,

just by changing charring/toasting conditions. This is for wine, of course,

but it really links the chemistry involved with the flavors produced, and

does so a rather readable manner.

Between to four of 'em, they for a pretty comprehensive review

what's going on, and (except for the Seagram article), should be

available to those who use Google and scholar.google.com.

I can help anyone who has trouble digging 'em up.

Piggott's book "The Science and Technology of Whiskies" is good, too,

but it's very very out of print.

Tim Dellinger

[bobbyc]

I can help anyone who has trouble digging 'em up.

Why not post the links, Tim? Some here would have a look-see.

[cowdery]

Thanks, Tim. Great information. I too would appreciate links to or copies of the documents you cited.

... the Tim Dellinger theory of "whisk(e)y terroir" is that the geographically determined temperature and humidity that you age in are pretty much unchangable for a given location... thus geograpically, scotch never could have developed in america (or vice versa), even if local tastes and availability of grains willed it to be so.)

Your theory is consistent with the Japanese experience. The Japanese whiskey industry began as a quest to duplicate scotch. Though never successful at that, they managed to create their own distinctive and successful product.

I've heard anecdotal evidence that barrels will eventually lose their structural integrity, but it doesn't seem to be a problem for rational (i.e. less than 30 year) aging times.

Agreed. What I have heard is that some scotch makers use barrels over and over until they fall apart, which usually happens at between 100 and 150 years old.

[Gillman]

I believe any drink (within reason) can be closely duplicated in foreign surroundings and that being so, differences in local climates and geographies are of minimal importance.

McCarthy's Single malt from Oregon tastes remarkably like an Islay single malt and this has been remarked by many experienced tasters.

If Doug had entered white dog in his barrel it would emerge (I have no doubt) very close to Kentucky bourbon in a few years.

Consider the ubiquity of many beer styles in America today that were associated with tiny corners in Europe.

Japanese whisky is fairly distinctive I think but in that case the movement towards a national style was intentional and is a recent phenomenon. In early days Japanese whisky was noted precisely for being similar to Scots malt and blended whisky.

In some cases duplicated results are achieved by importation of some foreign materials. But this is not always so, e.g., many beer styles use local ingredients.

Perhaps "Russian" vodka is the best example..

Gary