More and more the topic of oak is part of the discussion in the wine world. We thought that it would be a good idea to do a little further exploration in to the topic and share with our readers some of why oak is used in wine and why it is being discussed.
Oak got its start in the wine world simply as a vessel to store and transport wine. Back in the days of the Roman Empire, wine would be brought along with travelling armies to quench their thirsts and provide some level of nutrition. Water was not as safe and potentially subject to bacteria spoilage. The method of that time was to store wine in amphorae. An amphora is a large vessel made from clay. While the amphora was a reasonable storage vessel, it was not great for transportation due to its weight.
As the Roman Empire expanded, this transportation issue became increasingly problematic. The Mesopotamians used palm wood to make containers, which were lighter than amphorae, but the palm was very difficult to bend. As the Romans pressed north into Gaul (what is now France and neighbouring countries) they encountered barrels made of oak used to store beer. Oak, they found, offered three benefits: it was softer than palm and therefore easier to bend; its tight grain made it waterproof and it was abundant in the European forests. It did not take long for oak to catch on and the clay amphora was replaced by the oak barrel.
Today oak remains the material of choice for storing wine, but for a new set of reasons. There are many materials that are waterproof, that are malleable and easy to shape and that are light in weight that would make better vessels for transporting and storing wine. Plastic, fibreglass, aluminium come to mind. These would also generate cost savings as well. What oak uniquely does is impart a quality to the texture and flavour of the wine wine that other substances do not.
Oak is a slightly porous substance. Just enough to allow a certain amount of evaporation to occur. A typical 225 litre barrel will lose 21 to 25 litres per year to evaporation. or about 10%. The water and alcohol evaporate leaving a greater ratio of flavour and other compounds in the remaining wine increasing its concentration which adds texture and accentuates flavour.
When tasted next to a similar wine aged in steel or clay, a wine aged in oak will have a relatively fuller body and more intense flavour profile than one not aged in oak. Oak will also impart certain flavour elements into the wine due to the presence of certain phenolic compounds existing in the oak, such as vanilla, the flavour most often associated with oak. Oak will impart other flavours and aromas too, such as cedar, almond or hazelnut, caramel, spice and smoke. Oak will also soften some of the tannins naturally present in the wine creating a softer mouthfeel. Oak will also add colour to wines making them darker, especially white wines. These effects will increase as more time is spent in the barrel. Oak ageing typically tends to run form six months to 24 months. New barrels will impart much more of these effects than barrels that have been used. By the time a barrel has seen its fifth fill, these effects other than evaporation are close to nil as most of the phenolic compounds will have been leached out. These are then referred to as neutral barrels.
Different species of oak grow in different parts of the world. France, the USA and Hungary are where most of the oak is grown that gets used in wine barrels. French oak barrels are the most expensive and will cost just over USD$1,000 for a 225 litre barrel. French oak is desirable due to its tighter grain which tends to impart more subtle influence on the wine. American and Hungarian barrels sell for half that price and impart slightly different flavours. Barrels from all over the world are hand made by bending the staves over an open flame. This actually “toasts” the oak. A heavier toast imparts a different flavour than a lighter toast, leaning towards more intensity and more caramel flavours.
Winemakers can affect the taste, texture and aroma of their wines by adjusting the amount and type of oak treatment. Greater oak influence is obtained by using new barrels, leaving the wine to mature for longer periods in barrel, using American oak and using smaller barrels and toasting the staves longer. Less oak influence can be obtained by using French oak, second or later filled barrels, larger barrels and lightly toasted staves.
Most red grape varieties benefit from some oak influence. Cabernet Sauvignon almost always receives a good amount of barrel treatment as do other thicker-skinned red grapes (Syrah, Merlot, Tempranillo and many Pinot Noirs). Red varieties have enough inherent substance to stand up to and benefit from time in oak. Lighter coloured and lower tannin varieties (Grenache and some Pinot Noir) can lose some of their freshness if aged in oak. Of the white varieties, Chardonnay can gain wonderful texture and aroma when exposed to the right amount of oak. Other whites such as Semillon, Pinot Blanc, and some Sauvignon Blanc do well with oak. Riesling tends not to be raised in oak.
Today there is a trend toward generally less oak influence in wine. Part of this is a reaction to some heavy hands in winemaking in the late 90s and early 2000s. There may have been a need for some winemakers to dial things back. There is also a general trend today towards fresher wines that accentuate fruit and freshness over texture and barrel notes. The great thing about the wine world is there is room for all types of palates and all sorts of tastes.
The wine world will always be subject to various trends. The current trend is characterised by a shift away from big, extracted wines with noticeable oak influence toward fresher, fruit-driven wines with subtle or no oak influence. But regardless of any current trend, balance will always be fundamental to the creation of good wine. A wine is in balance if no one component sticks out significantly above the others. There can be too much oak if excessive vanilla are caramel notes are present and too little oak if the wine comes across as too lean or sharp. Where you place the fulcrum to determine the balance point is subjective and always up to you to decide, not any current trend.