For thousands of years oak has been the secret ingredient wine makers use to craft their wines into complex, structured creations. Imparting this wood into wine has long been the key in rounding out the edges of the wines and maturing them. Oak can be used to add character to otherwise 'bland' varietals and help them take shape. Take for example the coconut flavours and toasty aromas added to Chardonnay. So what exactly is it about oak that makes winemakers use it so religiously?

First, it is important to note that the process of ageing wine is a gradual introduction of minute amounts of oxygen. Oxidation at these levels allows wines to develop layered and more complex aromas. White wines and some red wines soften their acidity, tannic red wines lose their rough edges, andboth types of wine take on a new, more appealing clour and graduation. White wines become golden and red wines brick red.

Where does oak come from?

Oak is-like wine-affected by the climate of the region it grows. Grains of oak wood are tightly compacted relative to other types of wood, this allows the oak to be permeable yet waterproof, letting in air but never leaking out wine.

There many species of Oak wood but only two reserved for wine making: white Oak varieties: Quericus Alba (American) and Quercus Petrea (European). In America, oak is grown in Missouri, Minnesota and Wisconsin. Oregon grows Quercus garryana which has many similarities with European oak.

In Europe: Slavonian, French and Hungrarian oak are used with the first typically used forlarger barrels. Hungarian barrels from Zemplén Mountains are highly sought after. The region is cold and the trees grow slower and take time to develop more compact grains therefore imparting very delicate flavours on the wine.

Oak is ready to harvest after about 20 years from planting with the best averaging around 80-100 years old.

The exterior bark is expertly stripped off. The process is very delicate and results in about two barrels per extraction. Add this to transportation, cooperage fee and the fact that any handling requires great skill (e.g toasting ) and the cost of a single barrel goes up.

Preparing the oak

After harvesting, the oak is dried for days and then heated over a fire by a cooper who works the staves into barrels. The level of toasting matters. Depending on how much heat you allow on the wood, you can determine the intensity of flabours the wine receives. The size also matters. Smaller barrels (barriques) have more surface area in contact with the wine and are preferred when ageing fine wines,

American oak is less tightly grained but more intensely flavoured than European oak. It gives more vanilla and sweet overtones. Winemakers use it for robust, powerful red wines and warm climate Chardonnay.

Both kinds of oak require zome time to season before they can be fashioned into barrels. They are air dried for about 24-36 months to allow them time to leach off undesirable chemicals and bitter tannins. Recently, and mostly for American oak, Kiln-drying has become common because it reduces the time to 6-10 months,

How winemakers use oak at the winery.

There are two different techniques to consider when using oak at the winery. Do you want it for fermentation or maturation?

Fermenting in oak means the must (mush of wine grapes and skin) is reacting with yeast inside the barrel, there will be less oak influence this way because once the yeast sediment is removed: some of the oak components will go with it. Maturing wine in oak guarantees that flavours are absorbed in wine.

How it all works

American oak makes a perfect partner for wines with abundant tannins and texture; it imparts its own modest amount of tannin to the wine resulting in a wine with soft, strong, palatable tannins and complex flavours.

French oak imparts light fruity flavours, spice and toasted almonds, sometimes jasmine and rose in white wines. Tannins generated are silky with a slight sweetness.

Winemakers may choose to use 100% new oak barrels to mature their wines. If there is slight toasting, the smoky and caramel flavours impacted will be less compared to tannins and natural oak flavours. This changes as you increase the amount of toast.

New oak has more to give. The more times a barrel is used to age wine, the more it loses flavour. You might find wines that have been matured first in new oak then in older barrels. Others combine the stark differences of both American and European oak to mature their wines 50-50%.

As you explore flavour, these little Easter eggs left by winemakers will become more apparent and sussing them out a relished treat.