Seven Essential Things to Know About Oak in West Australian Wine

For centuries, wine has been stored wine in watertight wooden barrels.  It was not long before it was discovered that this process not only kept the wine safe from deterioration, but actually added flavors that wine lovers enjoyed.

In most of the world's wine-making regions, the wines considered each winery's best were those "reserved" in barrels for additional aging before sale; thus the widespread use of words like "Reserve," "Reserva" or "Riserva" on more expensive wines; and a taste of oak in wine came to be thought of as a signal of high quality.

“It's hard to generalize about the exact effects of oak on wine because so many variables apply.  French, American and Yugoslavian oak are all widely used, each conferring somewhat different characteristics; moreover, some high-end wines even distinguish French oak by its forest of origin, such as Limousin or Nevers.  Oaking affects reds and whites somewhat differently; new oak has different characteristics (usually stronger and more harsh) than used oak barrels; and the amount of time the wine spends in oak is also significant, as is the wine maker's decision whether to ferment the wine in oak containers, whether to store it after fermentation in large or small casks, and whether to use casks that have been "toasted" (lightly charred) or not.” [1]

Most of the great wines of the world are aged in oak.  Indeed, all the wines for which Margaret River and Geographe are famous (particularly Cabernet Sauvignon and Chardonnay) are aged in oak barrels.  Winemakers spend decades searching for the best oak to match the terroir of their soil. 

Here are seven essential points to know about oak when discussing your West Australian wines.

1.     Oak Leaves “Non Fruit Aromatics” In Your Wine

Oak almost invariably leaves identifiable traces in the wine – but this is a good thing.  A noticeable vanillin aroma is commonplace, especially with American oak in white wines like Chardonnay and fruity reds like Merlot, where the vanillins often convey a sense of sweetness that seems to appeal to the marketplace.

Over-oaked wines may literally smell like wood, very much like the smell in a house with freshly sanded floors. Tasting such wines is like sucking on a pop stick.  In reds, especially California and Australian Cabernets, new American oak often smells like the herb dill. In Mediterranean reds, from Rioja to France's Languedoc, oak flavors show up as coconut or aromatic spices like cinnamon, cloves and nutmeg.
 

   
cinnamon                  clove                nutmeg
 

      (a)   European oak, and
(b)   American oak.

(a) European Oak

Most European oak used in Western Australia is French oak.  France, however, is just one of many European countries producing a significant amount of oak.  Other countries include some Baltic states and Eastern European countries, as well as Portugal.  As winemakers, we regularly receive brochures and letters extolling the virtues of Eastern European oak, but at Killerby, at least, we still always use French.

Quercus robur tree

The most predominant oak in France and the rest of Europe is Quercus robur, generally a wide grained species, which is tolerant of a variety of growing conditions.

When selecting our barrels, we are less concerned with what forest the oak comes from, and more concerned with the tightness of the grain of the wood.  “Grain” is the term used to describe how tightly the fibrous channels in the wood are packed.  A tight grain means the wood is less porous, and therefore is more likely to make a watertight barrel, but the grain also affects how the much oak flavour is imparted to the wine.

The most significant forests for the production of oak suitable for coopering are in Vosges, Limousin, Sarthe and the central regions of Nièvre and Alliers.

Certain forests, such as Tronçais in the central region, are particularly well known, and wood from this forest is a particularly match for the Killerby wines.

There are smaller forests in Alsace, Burgundy, the Loire Valley and Champagne that provide some wood for the local wines in that area.

The forest of origin is of some importance, as the climate in which the tree has grown will affect the density of the grain, and thus the quality and suitability of the wood.

Vosges, Nièvre, Alliers and Sarthe oaks all have a tighter grain, and we regard them as excellent sources of wood.  Oak from the Limousin forest has a wide grain and for that reason, we do not regard it as highly.

Other European oaks come from the Baltic States and Eastern Europe. Baltic oak was once highly prized, but communist rule and the resulting poor forest management severely reduced its use by European winemakers and resulted in almost negligible use by Western Australian winemakers.  

European Oak Tree

Portuguese oak was always important in European winemaking, not so much for barrel production, but because the bark of the cork oak is harvested for the manufacture of corks.  Portuguese oak barrels, however have not found there way into Western Australian winemaking.  The importance of Portuguese cork is also declining with the rise of Stelvin capsules on wine.

(b) American Oak

American oak has a history of use in Spain and Australia, as well as the obvious markets of North and South America. American oak is known for being richer in tannins.  The bold, spicy vanillin flavours imparted by maturation in American oak were deemed suitable for big, full-bodied red wines such as Rioja and ripe Australian Shiraz.  Indeed, the Killerby Shiraz during the early nineties was matured in French oak, but during the late nineties, we came around to the view that American oak made a better Shiraz.

The main species of oak in the USA is Quercus alba, but there are a large number of other species, not all of them suitable for wine barrels. In general, North American oaks are wide grained, because the warm climate and long summer season results in a greater amount of growth each year.

Upon first examination, one would think that the wide grain would mean that the wood is more porous than in French and European species.  In fact, the opposite is true. The American oaks are much richer in compounds called tyloses than the Europeans, and thus possible sources of leakage are less. 

Splitting oak at Dargaud et Jaegle cooperage in France

The market for American oak has increased in recent years, in part because it is less expensive than French oak. For example, we pay around $900 for a top quality 300 litre American oak barrel (holding 400 bottles worth of wine) and around $1,600 for the best French oak.  It is not, however, a question of cost.  It is a question of style.  Dan Pannell, winemaker at Picardy Wines in Pemberton, says,

“We can get good complexity using fine-grained American oak for Shiraz,” says Dan.  Oak is good for tight wines; it lifts the back palate and adds to the complexity.” [2]

French oak, however, is the choice for Picardy’s Chardonnay, Pinot Noir and Merlot Cabernet Wines.[3]  The Pannells have an association with the French cooper Tonnellerie Meyreiux Fils and now in fact import Meyreiux barrels into Western Australia.    Meyreiux is a very small, exclusive Burgundian cooper. They turn the raw barrel six times for only 15 minutes each time. This regime, plus a smaller oak wood brazier, penetrates the toasting much further into the stave. Killerby has used Meyreiux barrels obtained through the Pannells for several years in the production of the Killerby Cabernet Sauvignon – most notably the 2001 and 2002 vintages.  The exquisite flavours from these barrels have been most impressive.

It is not usual to see American oak being used in Cabernet Sauvignon production in Western Australia, however, Brendan Smith at West Cape Howe is quoted as using it for his Cabernet.  “American oak has come a long way in the last ten years,” says Brendan, “And you can fairly reliably choose the grains you want now.”[4]

The best quality French oak always distinguishes the forest from which it came.  American coopers, however, rarely specify the forest. This is surprising as the major American white oak forests span 18 Eastern American states and Oregon. The major eastern forests range from Pennsylvania in the North East through North Carolina, Tennessee, Kentucky, Missouri and through into Arkansas and Mississippi in the south. In fact, the US Forest Service estimates there are 5.2 billion white oak trees (greater than waist high) covering a total of 235,000 square miles.

At an Oak Barrel Symposium held in Fresno California, Jeff Cohn, winemaker from Rosenblum Cellars in California, outlined the differences in American cooperage.

“He explained that oak from Missouri produces big flavours of vanilla, lemon custard and spice, and in less seasoned oak, a dried herbal character. Pennsylvanian oak is tightly grained, and is reminiscent of French oak except with some subtle coconut and vanilla notes. In contrast, Virginian oak imparts a burst of coconut and vanilla, but also gives the wines finesse and mouth-feel with time. Finally Oregon oak is very toasty, resinous, spicy and caramel like, but can impart a degree of harshness due to the pick-up of hard tannins.”[5]

American oak influence in wine is usually to impart the flavours of coconut and vanilla. This is due to the occurrence of higher levels of the character impact compound cis-oak lactone in Quercus alba compared with European sessile oak.  Cis-oak lactone imparts flavours of coconut, vanilla, and custard powder, and gives an impression of overall sweetness on the palate.  This is why American oak is an excellent choice to match powerful Western Australian shiraz.

Once the staves have been formed, either by splitting or sawing, there is still a long wait before the barrel can be made, and many decisions to make along the way.

Firstly, the wood is dried, which may be rapidly achieved using a kiln, but many prefer the practice of air-drying. At Killerby, we have never used kiln dried wood as we believe that there are still green flavours in such oak.

A large cooperage would have a huge amount of oak air-drying, or "weathering" at any one time, because the process is much slower than kiln-drying. In most cases the wood would be left outside for well over a year.   The barrels that are used at Killerby vineyards are in fact air seasoned for three years.

Some high quality wine producers in Europe will often buy in wood and weather it themselves, in order to ensure the process is carried out just to their liking. Yalumba is one of the few wineries in Australia that do this – they in fact have their own coopers to make the barrels for their Octavius wine. 

During the outdoor drying process, the colour will darken to a silvery-grey hue and the ground beneath the wood will stain darkly. Some winemakers say that this is due to the leeching of tannins from the wood, but we do not believe this to be the case.

The cooper then assembles the staves to form a barrel. This is frequently performed around a small fire, usually burning the wood shavings the cooper has generated when dressing the staves in preparation. This fire heats the staves whilst they are bent, but it also has the effect of toasting the inner surface of the barrel.

The amount of toast will greatly affect the flavours the barrel will impart to the wine. Alternatively, the barrel may be formed around a source of steam, or other heat source, and again different flavours will result.  At Killerby, we only use barrels that have been shaped around a fire, as the resulting toasting levels on the inside of the barrel are critical in creating the flavour profiles of our wines.

Shaping oak barrels around fires at Seguin Moreau in France

4.  Hogsheads and Barriques Are The Main Types of Barrels Used in Australia

The size of the container also varies the influence on the wine. A small barrel will provide a greater surface area to volume of wine ratio, and the flavours will be more pronounced than in wine matured in a large barrel.  The most usual barrel sizes in the small barrels are 225 litres (barriques) and 300 litres (hogsheads).  These are the only sizes used at Killerby. 

The majority of barrels used in Australia are hogsheads, whilst the majority of barrels used in Europe are barriques.  For those in Australia who favour barriques, the call is usually “line ball” between the two, with barriques arguably being slightly ahead in quality.  The reasoning is that barriques are smaller and the best oak is easier to select in the shorter lengths used for barriques than in longer lengths needed for hogsheads. 

5.    New and One-Year-Old Barrels Are Usually the Best

Having purchased the correct oak, specified the barrel size and the nominated the degree of toast, the next decisions are all made in the winery.

New oak barrels have never been used.  Therefore, the oak flavours are more powerful in new barrels than they are in barrels that have been used once or twice. It is rare that a winery will use 100% new oak for a red wine in Margaret River.  Gralyn are reputed to do so, but there are few others. 

The reason is that using 100% new oak will almost always overpower the weight of fruit in a wine.  Therefore, the winemaker will have to make a decision as to how much new oak to use for each wine. This means that the winemaker will have to use some of the barrels from the previous vintage, which in turn means that the previous vintage will have to come out of wood and be bottled so that the next vintage can go into those barrels.  

In Burgundy, where using 100% new oak would swamp the wine, the good producers are rightly cautious, only using a few new barrels each year. In Bordeaux, however, many châteaux will use 100% new oak each year, or even 200% in the case of some of the “vin-de-garagistes”, racking from one set of new oak barrels to another set after a year. A greater oak influence may also be achieved by fermentation in the barrel.  The Killerby Chardonnay and Sauvignon Blanc, for example, are fermented in new French oak barrels rather than in a steel tank.  It is much more difficult to barrel ferment wine – you can imagine keeping 100 barrels fermenting is more work than fermenting the same quantity in a stainless steel tank.  Barrel ferments, however, provide greater integration of the oak and fruit flavours in the finished wine.

The winemaker must also decide how long to leave the wine in the barrel before bottling. This will vary greatly according to the style of wine.  In France, the local appellation regulations sometimes specify the length of time in barrel.  In Australia, however, it is entirely up to the winemaker.

The rule is, “the longer the time in barrel, the greater the influence of oak on the final flavour profile of the wine.”

This period is referred to as barrel maturation, and it is not just the contact between oak and wine that is of importance. It is believed that the contact between the wine and the small amount of air present in the barrel has a beneficial effect on the way the wine matures.  The evaporation of wine and the transfer of air through the oak is the main reason that wine aged in oak barrels is more integrated than wine made with oak staves placed in stainless steel tanks.  The evaporation of wine in the barrel (usually around 3% of the total volume) is known, somewhat romantically, as the “angel’s share.”  

Oak barrels are very expensive. Consequently, some winemakers will add oak flavours to the wine by a variety of other methods, not all necessarily legal.

One obvious method for reducing the cost incurred by oak aging is to purchase second-hand barrels. As many top wineries use only new and one-year-old oak, there is a good supply of two-year-old barrels, which will be in good condition. Killerby Vineyards, for example, sells all its oak barrels once they are two years old.

Barrels in less than perfect condition, whether just purchased or in the winemaker’s cellar, can be repaired by the insertion of the necessary number of replacement staves. This not only breathes new life into the barrel, but also adds a touch of new oak influence to the wine. Old barrels may also be revitalised by disassembly, shaving down the staves, and retoasting during reassembly. This has been practiced by many top winemakers – Tim Adams of the Clare Valley is quoted as doing this - purely due to the prohibitive cost of new oak.

“If a bottle of wine retails for less than $15 it is highly unlikely that it has ever seen a barrel,” says Rob Keith, manager of Suber Lefort in South Australia.  Suber Lefort is a supplier of oak barrel alternatives such as inner staves, oak chips and oak planks that are placed in stainless steel tanks.  Keith says that the [yellowtail] Chardonnay that won a gold medal at the Royal Melbourne Show in 2001 was made solely with oak staves.  “It never saw a barrel,” he says.[6]

Oak flavours can be added simply by lowering a few staves of oak into the tank containing the wine, which avoids the business of cooperage altogether. Even cheaper is the option of adding oak off cuts, chips or shavings, all dangled into the wine in a porous sack, rather like a giant teabag. Whether or not this is legal depends on your location - Australian winemakers can do this within the law, whereas it is very much illegal for winemakers in Bordeaux. Another option is the use of powdered oak extract, although this is generally illegal regardless of location.

  “Oak planks or chips are placed in the vat with the wine and react in the same way as the wood of the barrel,” says Keith.  “The planks or chips stay in the wine for the same amount of time as the wine would be barreled.  The only difference is that the wine is stored in stainless steel tanks and the oak characteristics come from the planks or chips rather than sitting in an expensive oak barrel.”

Of course, we do not agree with this.  Yes, it is true that oak can cost more than $2 per litre, whereas oak planks or chips can cost around 10 cents per litre.  In our view, however, wine made in this manner lacks the integration obtained from the evaporation of wine and transfer of air that can only take place in a barrel.  Further, the quality of the oak supplied for staves is nothing like the quality of the oak in the best French or American barrels.  The premium Killerby wines are always aged in oak barrels.

There are three reactions that occur in wooden barrel aging that make it preferable to stainless steel vats with planks or chips:
(a) ethanol and water evaporate through the side of the barrel,
(b) oxygen is admitted, and
(c) wood substances such as tannins, vanillin and syringaldehyde are extracted into the wine.

These reactions do not occur in steel vats.  Since the processes are different, we believe that the results are also concomitantly different.

“Chipping and powdering can also produce a brown paper bag like flavour due to extraction of the celluloses from the wood, whilst tank staves may produce more obvious bacon and smoky aromas. So why are barrels superior given that the wine is in contact with oak no matter what method is used? The answer lies in not so much in the chemical nature of the oak itself but in the fact that a barrel is unique in that it allows controlled amounts of oxygen in and out of the wine over a long period of time. Oxygen reacts with wine components, both modifying, and in most cases improving its flavour and mouth-feel.”[7]

Conclusion

There is a lot more to oak than just the length of barrel maturation a wine experiences. The price you pay for a wine is often a good indication of the quality of the oak that it uses.  In our view, there is no substitute for using the finest oak barrels in the production of premium wines.