The winemaking industry knows John Glaetzer, for his 70s catch-cry “no wood, no good!” His premium wine, John’s Blend is a tribute to an age-old love link between oak and wine. His phenomenal red, chock-full of lush soft Cabernet Sauvignon grapes, matures in the choicest oak heads, producing some of Australia’s best Shiraz.
Glaetzer gave his wine as much of new oak as it could take, saturating its bold, sweet qualities with a seductive mix of toasted coconut and vanilla flavourings. So, how does oak affect wine? The Barrosa Valley Shiraz, for instance, is a flavoursome wine with a dried currant and ripe blackberry aftertaste. Here, South Australia wine masters use oak as a “spice rack” teasing out complexity in the wine and adding to it, spicy undertones with chocolate zest.
Different ways to oak wine
Barrels
The Spanish Celts invented oak barrels, and then the roaming Roman soldiers adopted them for their journeys of conquest. Over time, the Romans realized that oak casks imparted attractive, new properties to their wines, making them smooth and softer. Minimal toasting of wood containers brought out scents such as cinnamon, cloves, vanilla or allspice.
Barrelled wines would also have butter or caramel aftertastes, as per the time spent in contact with the wood. How is oak added to wine today? Some oenophiles stand by the wine barrel as the standard of conferring the tree’s glorious notes to the grape. Hardwoods, however, take close to 150 years to ripen.
The tree’s staves require an extensive maturation process that cuts down on astringency and greenness. The French oak will produce two vessels per tree, making the container exorbitant.
Barrels could append the value of $4 per bottle. Consequently, affordable oak options such as chips, cubes, staves and oak extracts are a necessity.
Oak chips
Smaller portions of oak can give their characteristic to wine at a more reasonable cost. Cubes, staves or chips will speedily season the wine with their high levels of oak essences. Steeping these solid oak chips or staves in a wine tank has been prevalent since 2006. Wines that have ‘oak influence’ or ‘oak maturation’ on their labels have zest from oak chips.
Oak extract
Oak essences are a class of oenological additives that add the spirit of new oak to wine. Using tannin extractions is not legal in some countries. Oak infusions ensure a constant taste to wine each year.
Why do winemakers oak wine in barrels?
Élevage is a French term for ‘upbringing’ or ‘raising’. It is the method of aging wine covering the processes between fermentation and bottling. A wine’s élevage can last months or years fusing and maturing its nature and creating a distinction between oaked vs unoaked wines.
During élevage, a winemaker will monitor, manipulate and direct the end taste of wine. One crucial decision that the wine master has to make is the use of either wooden or steel containers. There are acacia, chestnut, mulberry, redwood or cherry vessels, but the European and American oak hogsheads are more popular.
Unlike all other trees, oak casks are indispensable to great winemaking because of the barrel’s gustatory signature. Below are some benefits of using oak for wine vats.
Adds flavour
Oakwood is made of 50% cellulose, 25% hemicellulose and 25% to 35% lignin. An aromatic tree, oak has high levels of tannins, that form 5% to 10% of its composition. Nevertheless, a tree’s origin and species significantly affect its nature.
Western France’s English oak or Quercus Sessilis takes the cup as cooperage’s choicest wood, for its tight grain and elevated levels of aromatic compounds. French oak confers subtle and un petit peu dark chocolate, savoury spice, and roasted coffee flavour to the wine.
American oak has a broader grain and imparts a quality as assertive and brazen as the American culture to the beverage. Wine, aged in American oak, has hints of coconut cream soda, sweet spice, or vanilla.
The cooperage process significantly changes oak’s sugar-laden hemicellulose binding agent. Exposed to heat, these sugars decompose to compounds like maltol, furfural and ethyl lactone. These are the origins of oaked wine’s caramel, roasted or malty notes.
The sugars within oak wood’s structure also hydrolyse when in touch with wine. Additionally, the wood’s lignin will also break down during the seasoning, charring and toasting stage of cooperage. In lignin, you will find flavouring profiles from vanillin, eugenol, guaiacol, and 4-ethyl guaiacol.
Vanillin delivers a vanilla quality while eugenol’s is aromatic cloves. Guaiacol generates a roast coffee, smoky tang while 4-ethyl guaiacol’s aftertaste has a smoky, floral and medicinal spicy effect on the wine. Oak has other compounds, in varying amounts.
You will find lactones in minute portions, giving wines a sensory personality of oakiness and a coconut or resin note when present in the wood at high levels. A cooper can restrain the heating process to produce a variety of flavour profiles in a vessel.
Allows the slow ingress of oxygen
Oak casks are the ideal fermentation agents, allowing the wine’s exposure to low levels of oxygen, which civilizes and makes a rich, age-worthy wine. The steel cylinder, on the other hand, does not admit the ingress of oxygen. Stabilizing wine in a steel vessel reserves the fresh fruit fragrances of white aromatic and semi-aromatic wines.
Provides an environment for malolactic fermentation to occur
Wines that ferment in mature oak have intimate contact with yeast, which transforms sugar into liquor. When the yeast dies, it forms a film of lees, freeing polysaccharides and amino acids into the wine. These elements develop a wine’s texture and flavour. The process also releases Glutathione, an antioxidant into the fermenting beverage.
How does oak affect white wine?
Most Aussie Sauvignon Blanc is unoaked and taken while young. A Sauvignon Blanc, however, can profit from oaking. Here is how to taste oak in wine; an unoaked white wine has a wide taste characteristic that can range from pungent tart or fragrant with citrus, cut grass, gooseberry, pineapple or capsicum profiles.
The oak-aged Sauvignon Blanc will have depth and complexity as fermentation and exposure to oxygen and old oak aroma’s work on it. It will have a creamy nature and more texture than your usual fruity pineapple or passion fruit notes.
How oak affects red wine
To illustrate what is oak in wine, the Australian wine industry has significantly developed since the days that Glaetzer would cram the wood’s traits into his wines. Coonawarra cabernets and the pinot noir from cooler climates were chock-full of oak qualities.
Today you can taste the down under Pinot’s low tannins and tasteful red berries qualities because modern winemakers are keen to show off their vineyards through their wines. They use larger and more traditional barrels and extensive vats that can hold thousands of litres at a go.
Grand 19th-century oak barrels were daggy for decades but are now trending in old cellars such as Barossa’s Yalumba and Hunter Valley’s Tyrrell’s Wines
What flavours do oaked wines display?
To round it all up here is how to tell if wine is oaked. First, oaked wines have loads of qualities and oak fragrances. Grapes like Chardonnay with a neutral aroma will have more complexity when aged in oak. An unoaked Chardonnay has crisp and clean undertones with apple and citrus undertones.
An oaked version has vanilla and riper tropical fruit flavourings. New oak will mutate the red wine’s composition, strengthening it and steadying it. Oaked reds, therefore, are silkier in texture and are pricier.