/s/EVERYTHING-YOU-ALWAYS-WANTED-TO-KNOW-ABOUT-OAK-BUT-WERE-AFRAID-TO-CASK
It is rumored that a skilled cask cooper can assemble a leak-proof barrel in under a minute using no glues or fasteners. Word is, that an oak tree needs to be at least 75 years old to possess the maturity in its fibers to make a good barrel, and that typically within many forests of the world, only about 5% of the trees are truly suitable for this destiny (due to straight trunks and closing of pores, among other criteria.) Wow. Oak trees & barrels are DOPE.
Yet, I think we take them for granted in our quest to not look ignorant when we engage in epicurean talks about adult beverages. It seems like any conversation you have about wine or whiskey, or any tech sheet, article, or retail “shelf talker” you read will tell you that “this whiskey was aged for 10 years in blah, blah, blah” or “this wine was aged in new Barriques for blah, blah, blah”….and we all just nod our heads, as if ANY details given about wood (or years) are impressive and meaningful just for the act of being revealed…but yet not really understood. What exactly does wood do, and how, and when, and in what way?
If someone does tell me a wine was aged in Limousin oak, should I be impressed, excited, or wary? Should I anticipate a particular flavor…does Limousin taste like Gummi Bears? Straight Bourbon is aged for 2 years minimum in heavily charred new American oak. Why this recipe? Do we just accept this info at face value? Nod your head.
To truly understand the use of barrels, and their contributions in flavor, texture, and weight to a wine or whiskey held in it, you need to get to know sugar, and how it gets transferred from wood to liquid, because it doesn’t just happen without unique circumstances or under specific conditions (We’ll try do this without scientific jargon that uses “Poly”-this, or “-hyde” that.)
We need insights into:
· Wood Fiber (differences among different trees)
· Terroir (influences of the environment where the trees grow)
· Sugar (different types, different flavors)
· Barrel sizes (two words: surface area)
· Cooperages (the process of making barrels matters)
PART 1: WOOD FIBER
Inside wood fibers are sugars that are basically held within the walls of the fiber strands on a cellular level. These sugars are caged inside. The cell walls must be shattered, altered, or broken down or the sugar will not come out. Using fire to literally scorch (or toast) the wood, the cell walls will break open and become “fractured”, giving escape routes for the sugars.
In addition, due to humidity and temperature changes, wine and whiskey (or other distillates) expand and contract. Even if the barrel staves are toasted through just a mere 1/16 of an inch, this fracturing allows a pathway for the liquid to infiltrate those fractured fibers, and then withdraw the sugars as they retract. Humidity (and associated air pressure) changes are critical to this process and are symbiotic to the toasting or charring. They need each other; they work together.
Also, as the liquid passes into the wood, it goes through the actual layer that has been charred (which, being burnt, has carbon all over it like charcoal) and now acts as an awesome spongy filter for attracting and holding impurities (such as sulfur.) The barrel interior basically has its own “Swiffer.”
From here, even with the incredible technology of the day (what number is the iPhone up to now???) there is still a mystery of exactly how much barrels affect the alcoholic liquids marinating within the now fractured fibers (versus flavors derived from the toasted grains themselves.) It is estimated that approximately 50-80% of the flavor in a Bourbon, for example, comes from the oak, and yet studies have shown that during maturation of a Bourbon in wood for periods of 1,2, 5, 10 years, that there is only a major breakdown of wood fibers in the itty-bitty charred layer, but not any huge change in structure of the rest of the barrel stave. In other words, over the years, it’s not like the liquid continues to penetrate or burrow its way into the wood stave, deeper, and deeper as time goes on. It only penetrates the fractured fibers (most people know this penetration depth as “The Red Line” within the thickness of a stave.)
The charred or toasted layer is releasing its sugar once it breaks down, but at some point it gives all it has. So when we age Bourbons or whiskeys for years and years, what is being accomplished if the fractured layers of wood are effectively depleted (NOT releasing any additional sugar flavor,) and the un-fractured layers are impenetrable and effectively innocuous?
The answer lies with two elements: one, is air. The second, is air. Let’s talk about the first one. As air permeates the wood from outside the barrel and finds its way into the liquid, it will oxidize (decompose the sugars, proteins, and acids) the juice. So just like when we cut open an apple, leave it on our kitchen counter and it turns brown (from oxidation) so too will the wine or whiskey. And those sugars are changing…they are turning brown (rusting) and effectively caramelizing in this process. Air changes the fruit flavors of the wine or distillate.
The second implication of air is called “polymerization”. Oops! We just used a “poly-“ word. Let’s simplify: Juice (wine or whiskey) newly placed in barrels….fractured barrels, of course…doesn’t just absorb sugar, it also sucks in oils (lipids), “spices” (woody aromas, or those other vegetal-animal-mineral molecules derived from the soils the trees were grown in...this is one of the main components of what is called Terroir), and Tannins, which are inside the oak staves.
You know tannins…that “thing” in wine (and coffee, tea, foods, and whiskey) that causes your mouth to go dry, but more-so, that compacts liquid into a compressed focused ball of flavor. Tannins are like gravity, pulling molecules toward the center of a sip’s volume, and forcing a powerful narrow bandwidth of linear flavor down the center of the tongue. We snobby people call this “structure”.
Initially, then, it makes sense that wine or whiskey gains oils, sugars, spices, & tannins when first stored in oak. As time goes on, though, there's a paradox. The wood tannins will change (and one would more than likely say, reduce.) Oxygen will bond with tannins. In doing so, this “Polymerization” softens their famous grip. The tight, compact, compressed structure of the tannins starts to alter and get less intense. Tannins may have been gained, but the muscularity will atrophy, leaving behind a diminished tannic texture often described as “polished”.
With wine, the oxidized tannins from wood feel different on the palate than the non-oxidized tannins from grape skins & seeds. This is a game-changer for structure and texture. High-toned unadulterated tannins direct the juice down the center of the tongue like an arrow, while looser, polymerized tannin allows the juice’s “fabric” to stretch out, and it spreads wider over the tongue...feeling softer.
PART 2: TERROIR
So air gets into barrels and changes the sugars and tannins, but terroir determines the speed.
If a barrel has loosely packed grain (you will see this in plain sight and even better under a microscope), there will be larger spans of alternating fiber & air gaps. This does two things; first, more of the wine or whiskey permeates the wood and inhabits those spaces as it ebbs and flows in and out of the gaps as temperatures change through the seasons. This gives more contact with the sugars, spices, & tannins.
Large air gaps also allow more oxygen to burrow through the wood staves faster from the outside air toward the interior of the barrel, so the rusting or “decomp” of the wine’s sugar starts sooner, and at a more rapid pace. Given the same amount of time in two barrels (one with loose grain and one with tight grain), all else equal, the contents held within a loose grain cask will have sugars that become a bit more pruney, amber-brown, and “stewed” because of more oxidation.
Then, the fibers themselves can be thin (fine) or wide. If there are thin fibers, there will be more of them per inch, and more surface area from each one. Trees are all about terroir as much as grapes or grains. For example, trees grown in cold climate, with high altitude, and in volcanic soil produce tighter grain, and that tight grain provides a governor for oxidation (fresh, not stewed, fruit tones persist); and, tight grain happens to equate to more woody aromatics. Tree fibers contain the microflora of their region (bacteria and micro-fungi) as well as the biological & mineral molecules of the soils. With tighter & finer grain, there is a higher density of thinner fibers (effectively more fibers per inch…or per millimeter) and therefore a higher content of these microflora.
Aromas & flavors inherent to each tree lie within the location of each forest: from climate, soil minerals, vegetation, soil micro-organisms, water tables, animal deposits and decomposition...this is the environmental essence of terroir.
Given the impartations of polymerized tannin and the ingress of oxygen, as well as the indigenous flavors derived from location, even when a barrel stops contributing sugar, it contributes changes through air and air.
Understanding the significance of wood fiber configuration, now it makes sense that we always want to identify the origin of the wood, because the terroir affects the fiber & air gap configuration, and the flavors hidden within. Our “Geek-Speak” now can have some context.
Different Sources & Options:
There are two types of oak in Europe: “Petraea” (or Sessile) oak trees have acorns that rest on top of the leaves; “Robur” trees have acorns that hang from a little stem.
· Petraeas oak has more varied & omnipresent aromas, and less tannin.
· Robur shares the root of its name with the word “robust”, and has more tannin.
Almost all Euro forests have a mix of these two trees, or inter-bred trees, except for the Limousin Forest in France, which has almost 100% Robur, giving more tannins to wines, or in its most common use, into Cognacs.
FRENCH OAK: in general, all French oak is known to impart sugars & spices with an aromatic, dried, stone-fruit sweetness (think apricot-nectarine-orange crème pastry), and a refined texture one could describe as a ‘delicate doily of custard cream.’ With higher toasts in French oak generally come tones of sweet Turkish coffee or white raisin-clove-bread pudding. All in all, there is a finessed creaminess imparted. Other distinctions come with the specific terroir influences of different forests as follows:
· Allier Forest, Central France
This forest grows the Sessiliflora (or Petraea) species of oak, which has very tightly packed grain. These barrels are known for soft tannins that are not overly present or dominating. When toasted lightly, the sugar takes a back seat to a grape’s terroir nuance; when heavily toasted, the sugars contribute a noticeable toffee, baking spice, & toasted nut flavor.
· Tronçais Trees, within the Allier Forest, Central France
Extremely tightly grained, and extremely fine grained….these are the prestige “royal” barrels. A wine’s fruit is able to shine through better than if it were sponge-soaked into looser grains, and the tannic texture is plush and almost rich & regal; the wine comes out more luxurious & meaty. A distinct wood-sugar sweetness is imparted. These trees are mostly Petraea species, known for softer tannins and more delicate yet intricate aromatics.
· Nièvre Forest, Central France
Northeast of Allier Forest, but the soils have a heavier silica and clay content. What does this do? Silica lends a vibrancy & ‘electricity’ to the aromatics of the grapes, and clay lends a richness of nutrients to the trees, giving them fine-grain growth. These barrels compliment the aging of white wines (such as Chardonnay and Sauvignon Blanc) and can help keep the wine “fresh” due to the compact, tight structure.
· Vosges Forest, Northeast France
The mountain range just west of Alsace, in the very north-east of France…just a stone’s throw away from Belgium, Luxembourg, and Germany. The grains can be relatively tight, but more on the medium side. These barrels give wine more robust tannins, and highlight the boldness & “big-ness” of reds.
· Limousin Forest, Western France
Oak trees have wide and loose grain, imparting more tannins. They often can contribute a noticeable aroma of fresh cut wood. These are the barrels of choice for aging Cognacs and Chardonnays in particular. Robur-palooza!
NOT FRENCH OAK:
· Slavonian Oak (not from SLOvania!), mostly from Croatia.
Known for very tight grain, this wood is often favored for producing larger than typical barrels (Barrique, or Vats), which hold a greater volume of liquid. The larger the cask, the less wood influence as there is way more liquid than surface area of oak. Slavonian oak is known to be quite neutral to the wine (allowing the varietals of grape or grain to shine through). When Slavonian barrels are used once in winemaking, the year-old barrels practically give no tannins to the next batch of wine. The Italians producing Sangiovese and Nebbiolo grapes (already quite tannic grapes), often choose Slavonian so the wines can age without gaining extra tannins. The juice retains more of its fruit character, and there is only a subtle taste of toasted wood…as intended.
· Russian Oak
If an oak tree grows in warmer climate, with nutrient-rich soil, and an abundance of water, they grow faster and the wood grain will be looser. Russian oak is known for its tight & fine grain due to cold climate, and stressful growing conditions. It is usually Sessile oak (low tannins) and tends to have low lactones (uh-oh, a science-y word!) a.k.a. woody aromas, so it is usually used with delicate grapes that are too sensitive to shine past an over-presence of oak. Pinot Noir and Merlot grapes are most often paired with Russian oak so that their finessed fruit character can show through, and the grape varietal characteristics seem to taste fresher & more aromatic.
· Hungarian Oak
Other than the classic vanilla & chocolate tones that seem to come from all toast levels in oak, Hungarian oak is unique in its influences of leather, black pepper, and bittersweet coffee tones….there’s a dark/brown savory & spicy layer added into the wine. Hungary’s native oak species tend to possess exotic spices, especially the aromatic compound called Cinnamaldehyde (cinnamon!!), Eugenol (clove!), Syringaldehyde (smoked nuts), and lactones (spicy vanilla caramel.)
· American Oak (from Missouri, Minnesota, Wisconsin, Oregon)
Speaking in broad generalities, French oak barrels are typically more subtle in tannin & spice, offering textures of satin or silk (remember, a lacey crème doily.) American barrels tend to be stronger in flavor, often described as cherry-cream soda, vanilla, or coconut, and whose oils result in wines with a slightly thicker, creamy texture. The American oak species “Alba” contains more sweetness, more spice and more tannins. Just like our trucks, American oak is big & loud! The sugar flavors typically are more stewed or cooked, reminiscent of raisin figgy pudding and campfire s’mores, and there’s an additional weight given to the wine by virtue of the bigger presence of toasted sugar. Lastly, and strangely, sometimes American oak (depending on the toast level, length of aging time, and grape varietal put in contact with such wood) can often impart a Dill smell. Strange to think that either Dill or Coconut…dramatically different smells…can both be the hallmark aroma of American oak. With Dill, think of it more as a garden veggie smell (whereas Dill PICKLE smell is often considered a flaw in the wine and is thought to come from Volatile Acidity ---VA are components that tend to vaporize out of the liquid, and are usually indicative of the wine becoming, or already having turned, to vinegar. Volatile acidity is common with Acetic Acid…the acid of vinegar.)
There is one more type of American oak worth noting: in Oregon, they grow Garryana oak, which is starting to be used more because of unique impartation of "dark flavors." Garryana has more tannins, but it counterbalances that with a deep molasses, clove, blackberry syrup, and sweet campfire smoke flavor. Mmmm...you had me at molasses!
WHAT WOOD A BOURBON DO?
With Bourbon, the requisite heavy char of new American oak yields different flavors in addition to the common coconut-cherry-vanilla…
Lighter Char: vanilla, caramel, toffee
Dark Char: coffee, chocolate, smoke
Heavy Char: Smoke, black pepper
· Japanese Oak Known as Mizunara oak (or Mongolian Oak); these trees are tricky. Not only are they relatively scarce, but their name translates to "water oak" because it is highly porous, has an enormous water content, and they seldom grow straight. Translation: they don't hold liquids well, they take a really long time to "Season" or dry out (a process which is needed prior to toasting, but also to allow air to Polymerize the bitter tannins in the wood staves), and you can't easily cut proper boards for staves. Oh....and did we mention that the Mizunara trees need to be at least 200 years old....and up to 500 years old...to mature enough for cask making?? Ay caramba! So, you may be thinking right now: why use these trees? And you would not be wrong nor in the minority to think that.
And let's say that you manage to get some straight cuts of non-porous planks dried out to make staves....the overwhelming consensus would say you need to mature whiskey for no less than 15-20 years in this oak in order to mellow out bitter components in the wood, and to subsequently release the flavors. Anything less than that: not yummy. Still wondering why they use these trees?
Most oak barrels (American, French, etc) cost between $500-$1500 each. Mizunara barrels each go for $5000-$6000 each....if you can find them.
Dying to know why they use them???
Like anything rare, it makes it more coveted. You can only get so many bottles of whiskey in existence from such a limited number of Mizunara vessels...that are inherently hundreds of years old. Coolness factor, check!
And then there's the payoff: notes of coconut, banana, Asian incense (cinnamon, ginger, rhubarb, lavender, anise, chamomile), sandalwood, allspice, and tropical orange & yellow fruits.
Mizunara wood also tends to tame Iodine in Scotch, and in others, it can enhance or unlock smokey BBQ flavors and release exotic fruit tones.
Shazam.
PART 3: SUGAR
SUH-weet!
Okay, let’s recap. We have covered the essence that a tree is not just a tree. Every type of oak grown all over the world will have different sugars & air gaps, and different flavor systems. This brings up the ubiquitous number we see on the label of our aged adult beverages. We always want to know OLD our potion is, which is really asking how many years has this been marinating with oak, and air?
A more techy, science-y breakdown of oak sugar is as follows:
There are actually several types of sugar inside oak, and since they come from different sources on a cellular level, we need to dissect their cells. Wood fibers, or their cellular walls, are made up of:
HEMI-CELLULOSE: toasting or charring this layer releases simpler (shorter) sugar chains…there are three sugars that get released (glucose, xylose, galactose.) These produce flavors such as maple, caramel, toffee, licorice, almond, walnut, butter, and wax. This enters the aging liquid as the “first wave” of sugar. Xylose, in particular, takes about 5-6 years to seep out into a distillate.
CELLULOSE: Alcohol contact breaks this component down into glucose sugar after 6+ years of maturation (a “second wave” of sugar). So cellulose doesn’t really do anything significant within the first 6 years*. It comes into play for distillates that are kept in barrel for 7 years or more. Glucose can take up to twice as long to integrate into a distillate as first-wave sugars.
*There are exceptions. With great fluctuation in temperature, especially through the Continental “four seasons”, we will see a more rapid release of Second Wave sugar. Hence, we often see Kentucky Bourbons released at ages between 2 and 7 years because it doesn’t take as long to get the maturity of hemi-cellulose sugar release.
LIGNONS: break down with heat AND continued contact with alcohol, releasing big gobs of vanilla flavor. This comes into play in the short and long term.
OTHER WOOD EXTRACTS (LACTONES): only a small amount is present in wood, but each tree species grown within different terroirs will also have a unique combination of these aromatic esters (special acids); the most prevalent lactones present coconut, and sweet custard/crème Brulee essences.
NERDY DIAGRAM ALERT!
Regarding whiskey, there is a clear distinction between flavor layers built up over time, especially after the seven year mark.
So is more age (more years in barrel) better? What is the difference between a 10 year or 20 year or 30 year old whiskey given the different release dates of sugars from fiber?
Distillates that come right out of the still are usually rather metallic tasting; it takes a good six or seven years to get rid of the metal “tang” through “subtractive maturation” in oak barrels. This is where the charred layer of the oak is soaking up these undesirable metal molecules, since the charcoal acts like a filter & a sponge. After 7-8 years (usually the youngest posted age on a whiskey) the wonderful flavors within the oak now start to show themselves; in the absence of the metal molecules, additional flavors emerge and are gained. Welcome home vanilla, toffee, honey, etc., hence “additive maturation”.
The maturation process (subtractive to additive) is its own art. Then, there are decisions about whether or not to change barrels and "Finish" the recipe with impartations from other wood, as well as possibly other ingredients (namely, the liquid leftovers of other "adult beverages" left behind inside the fibers of their alma mater barrels.) Here, it’s quite simple: the first time a used & then emptied wine/sherry/port/rum/Sauternes/bourbon cask is filled up for whiskey (“First Fill”), it possesses the most "alumni" sugar within its spongy staves. In other words, the wine/sherry/port/rum/Sauternes/bourbon sugar becomes the final wave of flavor. At this point, the second-hand barrel will contribute its biggest flavor back into the whiskey fill. Of course, the casks get depleted each time they are re-filled to finish yet another incoming batch of whiskey.
In spirits maturation, it is the art of aging that must balance the prior use & potency of the cask, to the correct number of months or years the spirit is sitting in that cask, to the correct strength or prominence of “distillery character” (i.e. the make-up or blend of the grain mash, including its malting style….were the grains steamed, smoked, baked, etc?) But to all this, add to the algorithm that water is evaporating out of the cask (during both maturation and finishing), and this changes the concentration of the golden potion inside, which in turn changes the formula needed to achieve that balance. Just nod your head.
Whiskey Aging ABC’s say to mature the whiskey for 8-10 years in American oak to get rid of the metal, then switch to another cask to impart secondary flavors of the wine or distillate that was held in it (not to mention the additive oak sugars) to “Finish” it (anywhere from a few months to another 1-2 years.) Beyond that grand total of 9-12 years lies the “love it or leave it” opinion of whether or not the whiskey aged for more than 12 years will now take on more wooded character than distillery (or grain "fruit") character. And if so, is this desirable? In other words, is there an imbalance of too much wood and we can no longer taste the grain? Or do we prefer a predominance of woody flavors over grain flavors? TBD based on personal preference.
This is the same personal choice of, let’s say drinking a Tawny Port at 10 years vs 40 years: Is 40 better? It's certainly more expensive, and considered "better"...more prestigious. But it's possible you may prefer the prominent caramel flavor in the 10 year. Over the additional 30 years, the sugar will continue to de-comp, diminish through time, and consequently the rich viscosity of the Port will thin out. Some may think the 40 year port tastes like a very expensive toothpick. Or, vice versa….the drinker feels the 10 is too sugar-dominant and the 40 is the most elegant nuanced juice quadruple the money can buy.
Somewhere in the Finishing process, though, lies a general consensus that the forest (oak) and the distillery (malt) must be in harmony, and that new casks from European trees are simply way too strong in woody flavor/aroma to use exclusively for whiskey maturation and finishing, unless they are larger in size to reduce the ratio of wood surface to juice. Using American oak for maturation is the preferred way to go for many producers to achieve balance of oak and grain.
For Bourbon: Yeah, yeah. We all know the rule: in order to be called a Kentucky Straight Bourbon, a corn dominant mash must be aged for a minimum of two years in HEAVILY CHARRED NEW AMERICAN OAK BARRELS. Why? What’s the secret sauce of burnt new American oak for 1,051,200 minutes (fans of Broadway’s “Rent” know the song, now times 2.)
The period of two years is significant for many reasons.
The term that defines "Straight" becomes a Standard Operating Procedure to ensure that a Straight Bourbon always tastes like a Straight Bourbon---that they ALL have a common formula of flavor derived from this prescription. That a gaggle of rogue distillers don’t produce a rainbow of bourbons with varying maturation periods and mediums, ensuring a kerfuffle of liquid personalities; that the very hallmark of flavor and viscosity this rule promises doesn't altogether disappear, or simply become unrecognizable, indiscernible, or unidentifiable.
This is how the French did wine. Every unique growing region (Appellation) had (has) rules. Rules, rules, rules. If you get a white wine from Sancerre, it WILL be Sauvignon Blanc, and WILL have a certain style & flavor from that exact prescribed grape, from that specific terroir. The grape & techniques are dictated. What this achieves is a certainty of flavor and quality…and a consistency of reputation and price-tag.
PART 4: HOW BIG IS YOUR BUTT?
So we've covered air gaps, sugar types, sugar release times, terroir & tannins and oxygen, and balance. All of these things are affected by the SIZE of the oak vessel. Size changes a few things. For one, how much liquid can be held inside. The bigger the volume of liquid, the slower the aging process. The smaller the volume of liquid, the more rapid the aging process. In a large vessel, there is way more liquid compared to the amount of wood. This means a little bit of oxygen has to cover a LOT of sugar oxidation; a little bit of wood sugar(s) gets diluted among more wine or distillate. It takes longer for all subtractive and additive processes to touch more ounces, and occur.
But the size of the wood vessel also affects the shape, which affects how short or long the staves are; in a taller one, the staves will be more stretched out, giving more exposed charred & fractured surface area. The top & bottom ("heads") of such barrels will be smaller. A more stout cask may have shorter staves, but there may be more of them to achieve a wider circumference. The heads may be much bigger in that shape. And while we typically don't see toasted heads, it certainly is an option to do if we want optimized oak influence!
To know vessel sizes & shapes is to understand why size matters:
CASKS: hollow cylindrical vessels…this is the “generic” name of all vessels holding liquids; not every cask is an actual “Barrel”
BARRELS: a particular size of cask; for wine and bourbon, it’s 200 Liters (or 53 Gallons) which is about 265 bottles of wine (750ml or 25.4oz). For spirits in Liter bottles, this would equal almost 17 cases of 12 bottles each.
BARRIQUE: Taller, and bigger (225 Liters, or 59 Gallons), also called a HOGSHEAD (which can be as large as 300 Liters). With the taller design, there is more surface area in the longer lengths of staves (hence more TOASTED area) while the resulting heads of the barrel (top & bottom) are smaller. Aging in Barriques has two implications: a larger capacity slows down the oxidation & maturation process, allowing a longer & more nuanced development of flavor. Also, there is a bigger impartation of the toasty qualities (vanilla & caramel, etc.) since the staves now comprise more area and the untoasted heads comprise less.
Barriques coming from France also have thinner staves, in terms of the depth, not width of a stave. Most barrels have staves that are 25 to 27mm thick. French (namely Bordeaux) Barriques have 20-22mm thick staves. Because they’re thinner, it takes less time for oxygen to burrow through. The rate of oxidation and aging is faster, or takes less time.
FOUDRE:
Humongous casks that can range in size from 2000 Liters to 22,000 Liters! (remember, a standard Barrel holds about 225 Liters, just for perspective.) In Manhattan, a Foudre would be the size of a good studio apartment!
Foudres and other over-sized casks are intended to allow the processes of barrel aging to take place, but at a much slower pace. For one thing, the size is so big, there is a lot more juice compared to only a bit more wood surface area. So it takes a lot more time for oxygen to continually permeate the wood and make its way through and to all the liquid. Second, the thickness of the staves (from the Oxygen’s standpoint, this is the depth of the wood going from the outside to inside) is thicker. So again, it takes longer for the O2 to burrow through. Foudres are typically used for the fermentation stage, and then possibly for slow-aging, with the objective of maintaining the fruit’s character and the fruit’s terroir (the flavors derived from the total environment, from sun to soil, surrounding vegetation to animal habitation) more-so over the terroir of the tree.
So why use a Foudre and not just a big stainless steel tank? Well, for one thing, there still is some aeration…which leads to a metamorphosis of flavor and texture. In Foudre, oxygen breaks down sugar and starts to transform it. Oxygen will polymerize tannins.
Lastly, with stainless steel, you have a network of cold freon tubes throughout the jacket of the tank (just like in your fridge) so temperature can be controlled. During fermentation, heat is produced. Winemakers can turn a knob and refrigerate the tank to keep the temperature from rising. This stable control keeps fermentation going for longer, and at a slower pace, and prevents a buildup of heat that would otherwise produce a more simmered, stewed, or “browned” flavor in the fruit. Stainless fermented wines therefore usually showcase bright, highly aromatic, deeply fresh, vivacious, & splashy fruit flavors and colors.
Foudres allow for mother nature, not a temperature knob, to determine when the heat becomes too high for yeast to metabolize sugar. So fermentation will stop naturally when the conditions hinder the yeast. Second, there still is some influence of the wood’s flavors & additives---there will be some absorption of the toasted oak sugar, some absorption of the natural spices & peppery notes inside the wood fibers. Thirdly, air is the hammer that 'cracks open the coconut shell' of the grape juice's tannin. Initially, the flavors & aromas are bound together, compressed and confined, and enclosed by the tannin compounds found inside the skins & seeds. Air…oxygen…will break down the tannin prison, poking holes into that shelled ball of flavor. With Foudres, however, and their grandiose volume, they may not be as effective and therefore not as appropriate for use with certain grape varietals that possess higher tannins; these grapes need more oxygenation to properly mature, release, and develop full flavor. Their tannins will evolve more timely, and the fruit will taste better in smaller casks that allow a more significant rate of air. So you may not see Foudres with certain grapes in them, and therefore, not in certain regions known for those grapes. It just wouldn't make sense.
Tuns: are primarily used for blending/marrying or resting wine
Pipes: Port, and eventually Scotch
Butts & Puncheons: Sherry, and eventually Whiskey
At the end of the day, watch out…there are differences in cask sizes across the world. English vs American cask nomenclature:
American cask sizes:
PART 5: “BARREL CHEFS”
Are cooperages important to the story of oak? Why do we hear that a winery or distillery used “Garbellotto, Valoga, and Seguin-Moreau barrels??” Is this Gucci vs Kirkland (Costco)? Ferrari vs Hyundai? Why do we care, and what does that indicate flavor-wise?
So of course each barrel maker (cooperage) sources their trees from different regions and forests. That’s enough right there for wine-makers and distillers to decide whom to use. But there’s also methodology and reputation for quality. Remember, only about 5% of trees in a forest are suitable for cooperage. That takes a discerning selection procedure.
Coopers must then season their wood. This involves air-drying the cut staves to allow water to evaporate and dry the planks out. If it is done improperly, or in incorrect conditions, the water can unevenly leave the wood, or remain, within different layers resulting in pressure forces that can warp and crack the wood. Methodology and controlled processes, not to mention elements of terroir where the wood is dried, will all affect the final barrel production. Often, the reputation (and cost) of a cooper may even be a direct relationship to their real estate---temperature, fluctuation, humidity, and other elements of climate are unique in each cooper's backyard, or as I call it, their "wood salon."
The seasoning process typically takes anywhere from 18 months to 6 years, and can often involve a precise stacking that resembles a sculpture, only to be dismantled, rotated, and re-stacked at times. It is a big deal.
Then, there's the cooking. Charring and toasting: there’s some chemistry in the art, and art in the chemistry. Using different temperatures and therefore different times of toasting will yield vastly different results. Think of slow-smoking your brisket or ribs for 14 hours, versus quick-searing a piece of meat onto a blistering hot cast-iron pan with high flames licking the sides. Slow & low, versus fast seal & sizzle?
Slower toasting results in more pronounced sugar aromas.
The control of the fire-pit temperature & time under flame is therefore a critical variable. Many coopers guard secret techniques. Garbellotto cooperage from Italy, for example, uses a patented digital temperature control called DTS™, or “Digital Toasting System”. Seguin-Moreau, of Napa Valley fame, uses an AQUAFLEX ™ where soaking the formed barrel in hot water softens the tannins, and reduces the smoky “grilled” aromas of the char as the vanilla aromas in turn stand out more. With this treatment, wine showcases more of its fruit tones because it won’t be masked or buried under toasted characteristics.
Seguin-Moreau also has other innovative techniques. Their “U-Stave” process chisels internal channels into the staves, and uses incremental toasting so that the channels get a lighter toast than the top surface. Effectively, there are stripes of light toast! This is a ‘two-fer’ of flavor by having a double-toast combo within one barrel.
It does matter who makes the barrels, and it is fascinating how they each make their barrels, and where they source their trees.
It can be a Cooper, or a Domaine of whiskey makers that conduct such a campaign. Buffalo Trace did experiments with variables ranging from how they seasoned the wood, the char level, the trunk portion and cutting techniques of the tree, etc. in what they called their "Single Oak Project."
They made 192 expressions of bourbon in this project and had thousands of tasters review. The winning recipe was: the bottom half of the tree, with a #4 level of Char, using average grain size trees, and conditioning (seasoning) the staves for 12 months. 1 out of 192 was the ONE. It all matters...
So what to do with your newfound oak insights? The next time you talk about wine & whiskey, and someone mentions the age of their potion…nod your head (of course.) And then say something super techy-jargon-nerdy-awesome, like “Hmmm…I wonder if the Xylose activation will be significant enough to balance out the non-polymerized tannins; maybe they should've gone with an English Firkin?” Throw in some Klingon, and you've got yourself one helluva conversation!!