Oak Obsessed: How a Barrel can Influence Wine

But despite their long history, winemakers only started realising that their barrels could add flavour, aroma and complexity to the wine they contained, in the 1800s.

As wineries now use stainless steel to simply transport and store wine, hand coopered barrels play an ever more critical role in the maturation and development of subtle flavour nuances in premium red and white wines.

We are the only winery in the Southern Hemisphere with its own working cooperage onsite – not unexpected given that we are Australia’s most historic family owned winery.

So we are more than a little obsessed with oak and what goes on inside and outside a barrel.

Take a tour of the Yalumba Cooperage with Yalumba’s Master Cooper Shaun Gibson.

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When it comes to maturing wine in barrels, our winemakers consider a number of characteristics, including the source of the oak, the grain size and density of the oak timber, the size of the barrel, and the way it’s been toasted.

"The origins of the oak will determine the type of flavour and aroma the oak will impart to the wine, and grain size and the size of the barrel will also have an impact on this," Yalumba winemaker Kevin 'KG' Glastonbury says

"Due to a greater surface area to volume ratio, the smaller the barrel, the greater the oak impact."

We use several different sized barrels for our wines: Octaves (100 litres), Barriques (225 litres), Hogsheads (300 litres) and Puncheons (500 litres).

"Oak was celebrated for its influence on wine in the 1990s and early 2000s – often pushing the influence too hard,” KG says.

"But winemakers have now moved to a more subtle and diverse use of oak. You really want the oak to support the fruit rather than the other way around."

KG, who makes our fine red wines including The Signature Cabernet Sauvignon & Shiraz and The Caley Cabernet Sauvignon & Shiraz, says having our own in-house cooperage is a luxury.

"We can look at the individual vintage before making choices about what type of barrel to use, or method of bending or toasting to employ."

For example, a cool growing season may result in wines that have a lot of natural acidity, leaving them looking a little flat, lacking in texture and vibrancy. During these vintages Yalumba winemakers often choose to increase the toast a little more to add volume and expression to the wine.

Similarly, grapes grown in a warmer year will be naturally more expressive, rounder, and softer. Following a warmer growing season, the cooperage will really wind back the level of toasting to bring more line, length and focus to the wine.

"Applying oak in the right way really completes the story," KG says.

Shaun Gibson, our Master Cooper here at Yalumba, is just the seventh Master Cooper to make barrels at Yalumba. He follows in the footsteps of those who came before him using traditional tools and techniques to fashion these beautiful wooden vessels.

"To bend a barrel into shape the timber staves need to be warmed to make them more pliable,” Shaun says. "This way there’s less risk of breaking a stave during bending.

"Barrels are bent one of two ways, using fire or water."

"Water bending involves submerging the barrel in water heated to 80°-90°C for around 20 minutes."

According to Yalumba Winemaker, Sam Wigan, water bending is used predominately when the winemaker is looking for a barrel to have a less obvious, softer influence on the wine.

"Water bending will leach tannins out slowly, like a tea bag, making the oak softer and more approachable," he says.

"All of our Chardonnay will go into water bent oak barrels which is pretty typical – most white wine producers who ferment in oak will go for a water bend. Even some reds require an early or softer integration of the oak – we’re probably 65% water bend here at Yalumba."

Fire bending requires the use of an open flame to heat and bend the barrel into shape – this results in a more robust oak with more obvious tannins than water-bent barrels.

The effects of oak on wine are varied and generally depend on the type of oak used.

The most obvious flavour compounds from oak, the actual "wet wood" taste along with coconut and vanilla, usually come from American oak which is bolder and more robust.

French oak is more subtle so the wine tends to be more elegant and silky and the flavours suggestive of spice, chocolate and coffee.

Chemistry is at play here. Phenolics are plant based compounds in the wood that interact with the wine to produce sweetness, and the entry of tiny amounts of oxygen help to soften the wine’s tannin structure and create smoothness and texture.

Oak barrels also provide a vessel for malolactic fermentation to occur, resulting in a creamier taste in the wine.

Once our coopers have fashioned the oak into barrels, they are then toasted over a fire, both to seal the wood and impart flavour.

Our coopers predominately employ a long, slow, medium toast, which is proven to be more homogenous and penetrates deeper into the staves.

This process helps to eliminate any surface blistering and results in a sweeter, more even toast that softens the aromatic compounds of the oak and elevates the natural aromas of the wine, providing the winemaker with greater control.

KG says toasting is the way for the coopers to put their "stamp" on the style of a wine.

"I don’t think you’ll find a lot of light toasts these day – light toasts will still leave the wine tasting aggressive and bitter. You need a toast that will produce that chemical reaction in the timber that you’re looking for," he says.

"In the 90s it was all about charring the oak with a heavy toast, which gave you more bang for your buck, but somewhere between then and now we've settled on taking a subtler approach, particularly with French oak."

"We tend to go with a medium toast, using a lower flame for a longer time which gives a deeper penetration so that the warmth and the heat can seep further into the timber over time. That’s when you get a lovely flavour balance integrated into the wine."