When talking about wine the "oak" discussion often turns to whether a particular wine was aged in French, American or other types of oak barrels.  No doubt, the type of oak influences the character of a finished wine, but what about the influences stemming from how the barrel is prepared? 

Regardless of the oak used to mature wine, the barrel treatment adds dimension to the inherent flavours already present in the oak.  It's a lot to consider, really.  Yet while this discussion may seem both ponderous, and only vaguely related to what's in your wine glass, a winemaker's "oak and barrel" decisions are abundantly evident in your mouth after the first sip!

So what, besides wine, goes in a barrel? 



For starters, how the wood is seasoned, for how long and whether it is air-dried or otherwise-aged prior to toasting greatly determines the underlying character of the barrel, which in turn will determine the taste of the wine.  

Wood contains about 80% humidity that has to be reduced to 15 to 18 percent before it can be made into a barrel. Seasoning, or drying the wood, can be done naturally or in a kiln.  The natural method is best but it takes 2-3 years to leach out ‘green' or bitter tannins from wood that is left stacked up outside and exposed to air. The kiln method is faster, but is less desirable because it cooks the green, astringent, rough tannin qualities into the wood.  This astringent quality will later interact less favorably with the wine in barrel.

Similarly, barrels made by individual coopers (barrel-making, wood professionals) will differ from one another, even when using oak sourced from a single forest.  Add to that the fact that machine cut staves render different taste outcomes to hand-split staves, with the latter being the preferred and superior method.   

All of these variables are further influenced by how much a barrel is toasted (placed over a fire), for how long, and whether the toasting is with the top uncovered, or not, also greatly affects the composition of the flavours a barrel will impart on a wine.  It's mindboggling to imagine the myriad of possibility! 

The World Cooperage Association suggests there are seven flavour categories that can result from toasting the barrel:

SWEET	Brown sugar, Bourbon, Cotton Candy, Chocolate, Maple Syrup, Butterscotch, Hot fudge, Caramel, Molasses, Honey, Toffee, Soy
CREAMY	Cream soda, Marshmallow, Lactic (milk-like), Butter
YEASTY	Popcorn, Baked Bread, Bread stick, Cookie dough
NUTTY	Hazelnut, Walnut, Almond, Peanut Butter, Coconut
ROASTED	Cedar, Graham cracker, Toasted bread, Coffee, Mocha, Cereal
SMOKY	Barbecue, Grilled Meat, Bacon, Sweet smoke, Burnt sugar
SPICY	Nutmeg, Cinnamon, Clove, Licorice, Anise

All this JUST from the toasting process!

Creating a barrel

French coopers were first to toast barrels to gain smoother character/richness in a wine. They also established a standard size of small barrels that weigh about 60lbs empty and hold about 22-25 cases of wine when full. To make a barrel the oak is cut into staves, shaped and formed, and then assembled.  Coopers prepare the barrel according to the requirements of the Château/winery.  A barrel is assembled with metal hoops at bottom, moistened, toasted and upper hoops set around the girth.  Then, barrel heads (ends) are fitted and a bung hole cut. Barrels are filled with hot water to find the leaks.  The leaks are filled and the barrels are finished by sanding.  Voila!  A barrel is born.



As mentioned earlier, the preparation involves toasting the barrel over an open fire to achieve a lightly-toasted, medium-toasted or a heavy-toasted result.  The heavy ‘burn' will, of course, impart the strongest flavours, including a smoky quality and should be used for aging big wines that are lavish with ripe fruit, high alcohol and character. Most winemakers opt for medium-toasted oak in order to obtain good, integrated flavours that will not overpower their wines.

Building a barrel may seem formulaic, yet it is not. Winemakers are very particular in their choice of cooper and brand of barrels because there can be so much variation.  A few of the well-known Châteaux in France produce their barrels on-site to ensure the best quality and control over the endless, subtle flavour enhancements derived from the barrel itself.  Every tiny detail relating to the barrel will exert an influence on the wines...even the way an oak tree has grown given the climate and soil within one forest, and the age of the tree when ‘harvested'!

Barrel lifespan

As sturdy and solid as barrels may be they have a limited life (around three years) in the winery.  This isn't because they fall apart, but because new oak barrels impart the strongest flavours whilst one-year old barrels will impart less oaky characteristics. Usually after three years the barrel is discarded because the pores in the wood clog up with suspended particle matter in the ageing wine.  Old, clogged barrels only allow very low levels of 'oak' flavours to emerge, hence their limited utility.

‘Used' barrels may be given a new lease of life.  Coopers will take the three or four-year old barrels apart and shave the staves to remove the clogged layers and reveal a new, porous layer.  These reassembled barrels, whilst inferior to new barrels because of their thinner boundaries, will do the job fairly well. Having new barrels available on hand is every winemaker's dream since good barrels cost upwards of four figures. A mix of old and new barrels will usually be employed to allow interplay between the muted ‘old' flavours with the strong, raw ‘new' ones whilst keeping costs manageable and ensuring a positive impact on the wine.

Oak maturation

Wine flavour and stability is enhanced in a number of ways when matured in oak barrels.  Slow absorption of air through the wood benefits wine and fixes a wine's colour after fermentation, particularly red wines.  In white wines that undergo barrel fermentation the interplay with oxygen, wood and the fermenting wine generally gives more complex and harmonious oak flavours in the finished wine. 

Barrel maturation also extracts wood tannins and other substances which add "structure" and "complexity" to the wine.  Overtime, the interplay between the oak and wine softens the wine's natural tannins and add spiciness and delicate flavours due to the slow, chemical and enzymatic reactions in wood. 

What does that mean?  In tasting terms it means that the oak will often leech out and soften the astringent tannic elements of the wine and make them smoother, and softer on the palate.  This helps a wine develop (what expert tasters would say) smooth, soft, velvety or fine grained tannins.  

The last thing to consider is that newly made wine is always cloudy from suspended materials, like dead yeasts that have completed their role of converting grape sugar into alcohol. Barrels naturally clarify the wine because over time the suspended matter settles to the bottom of the barrel leaving the wine clear.  Natural clarification, where the cellar-man drains the barrel and ejects the residue and refills the barrel, results in a wine that is fuller and subtler in flavour as compared to wines that undergo modern filtration methods. This process of emptying and refilling barrels is called racking the wine.

In the modern era, wine is pumped through filters to clarify wine. Lately though the trend has moved towards tradition as winemakers have turned back to letting wines clarify naturally. By not using filtration, wines have a fuller and subtler flavour and the drinker gets more of the natural taste.



Oak flavour from "other" oak sources

Barrel maturation or fermentation is not the only way that wines can get their oak flavour.  There are other, more modern means of imparting the flavour at a lower cost.  Oak chips are commonly used to add some complexity to large-volume, economically-priced wines.  Oak chips, cubes and oak marbles (which are a relatively recent innovation) manage to add much of the required flavours although incorrect usage of these oak fragments can impart some bitterness and coarseness to the wine.

This unwanted outcome is not entirely due to the modern process but is also due to the lower quality of oak used in chips, since the best oak go into making staves.  It is also because the "wood-to-wine" surface area ‘interaction' is higher per kilo of wood used.  This may be difficult to understand, but it's really simple.  The more wood that touches the wine...the more influence.  Chips or marbles are usually added to fermenting wine in the form of giant 'tea-bags' so that 'infusion' can take place.  Often this doesn't allow the oak to "integrate" with the wine as much as time in barrel would.

Other alternatives include using oak planks and even oak ‘dust' is common.  Oak dust however, confers little oak flavouring, but does impacts color stabilization and adds some tannin to a wine.  Dust is meant to be used with the most basic wines and is often used in combination with other oak treatments.

Tasters sometimes comment that if oak flavours in a wine are very pronounced, it must be due to oak chips and therefore, the wine must be cheap and nasty.  Such a conclusion is erroneous. Wines made from good, highly flavoured fruit will often demand strong oak flavours, and it is the best wines made from such fruit that will go into new oak barrels. The result is that when young, the wines are 'fully oaked' in flavour although supported by strong fruit flavours.

Still, this sometimes leads tasters to proclaim that oak chips have been used.  Even the most discerning taster will find it difficult to tell if a good wine has been made using oak chips or barrels when the balance between oak and fruit flavour is correctly accomplished.

In short, oak and barrels matter...

Know Your Barrels Ed Soon 27/03/09
All Photos in "Oak and Barrels Matter" Part 2 were taken and contributed by Ed Soon. Bravo!