Why is oak used in winemaking?
Brown Hill Assistant Winemaker Angus Pattullo explains why oak is such an important part of the winemaking process. Wineries use oak barrels not only to store and age wine, but also to impart a unique flavour, aroma and structure to many varieties of both red and white wine.
Many tasting notes and wine bottle labels refer to oak, whether it’s oak integration, oak influence, oak ferments or oak storage. You’ll be hard-pressed to find a winemaker, wine reviewer or wine connoisseur who doesn’t talk about oak influence, tannins or oak barrels at some point. This is because as an ingredient in wine, oak selection can in many cases be as important as the grapes. Here, we explore how winemakers use oak in the winemaking process and cover different types of oak and their flavour characteristics.
What is oak?
Images of moody, earthy-smelling cellars stacked with portly wooden barrels are classic motifs in the wine world. Although winemakers have access to thousands of types of grapes to make the wine that ages inside the barrels, did you know that winemaking uses only one type of wood? That wood is oak.
For centuries, oak has been the traditional storage vessel for wine, as oak trees grow throughout Europe, a continent with one of the longest histories of winemaking. Though oak adds flavour, aroma and structure to wine, there may be a much more functional reason behind why winemakers first used it. Oak trees grow straight, which makes them easy to process into uniform planks of wood. These planks, in turn, are later turned into staves to make barrels.
As a material, oak is a soft wood that contains very few knots, which also makes it easy to bend into the curved silhouette of a wine barrel. Once coopers, or barrel makers, transform the oak staves, the barrels become watertight thanks to the tight grain of the wood. Oak’s tight-grain advantage also helps minimise the angel’s share – the portion of wine that evaporates through the pores of the wood during the aging process.
In addition to winemakers using oak for its practical benefits as a wine storage vessel, they can also manipulate the oak to produce wonderful aromas, flavours and textures in their wine.
Where does oak come from?
It can take as long as 120 years for an oak tree to reach maturity and be ready for harvest. Plus, it’s not uncommon for natural phenomena, such as bushfires or severe storms, to wipe out entire growing regions for a generation or two. This, together with the fact that most of the oak in the wine industry comes from only two countries, makes the production of barrels for the global wine industry even more specialised.
France and the United States of America account for about 95% of all oak barrel production, with Hungary also supplying a small amount from its French oak species. Although they are from the same family, French and American oak react differently with different wines, creating varying structures, textures and body weights.
What is the difference between French and American oak?
French oak originates from what’s known as the Old World of winemaking. In addition to its appealing structural aspects for barrel making, French oak can impart subtle effects onto the wine’s palate – flavours redolent of roasted coffee beans, dark chocolate and savoury spices – to enhance the fruit.
American oak barrels, on the contrary, impart heavy coconut, vanilla and sweet spice notes, and help build structure and weight in lighter wine styles. Whereas French oak can be more elegant, American oak can be more assertive and pungent. At Brown Hill Estate, we use small portions of American oak in our shiraz blends because it imparts the body weight, structure and spicy notes that have become hallmarks of Margaret River reds.
Today, the industry is so nuanced; each winemaker and winery will have their own ‘house style’ of barrels that are in rotation. Winemakers can look at how certain cooperages produce their barrels and pinpoint certain forests that work perfectly with the wine styles they are producing. For our 2018 Golden Mile Shiraz, for instance, we trialled a combination of different oak barrels. The Burgundy oak barrels we ultimately chose were Louis Latour and François Frères, which together brought unique, complex flavours and textures to this shiraz.
How do winemakers use oak in winemaking?
Why does wine need that woody taste or influence? And is it even desirable? These were just some of the questions going through my head during the first semester of my winemaking degree. So, let's look at answers to why winemakers use oak, what it does to wine and – most importantly – how it enhances wine.
Winemakers use oak to help produce a particular style of wine. Both whites (the most common being chardonnay) and reds (from shiraz to cabernet sauvignon and pinot noir) can have oak influence. In white wines, oak can add buttery, nutty flavours, as well as depth and roundness to the body. We love what it does in our Brown Hill Estate Sauvignon Blanc, Semillon and Chardonnay. We bring in small portions of batches, whole-bunch press them and then ferment them in French oak barrels. We then let them age for a short time – from three to nine months. In the barrel, the acid mellows, and the oak imparts beautiful buttery, creamy, nutty flavours. Then we blend the oak-aged wine with portions that don’t have contact with oak to create complex, well-balanced wines.
With red wine, we do things a little differently. We age our reds longer – from 15 to 18 months – depending on the style of wine. Reds have a lot more going on: we ferment the wines on skins and seeds to extract colour and tannin to give them their rich colour and texture. The longer the wine spends in barrel, with oxygen slowly coming in through the pores of the wood, the more the harsh acid breaks down and the more influence the tannins have. This can also introduce some beautiful dark chocolate, coffee and spice to the wine’s palate. To reiterate, different cooperages and different forests produce different profiles that can influence the final wine. So as winemakers, we’re constantly looking at how each barrel performs.
We age our reds in a mixture of French and American oak to impart specific qualities, sometimes, specifically for our shiraz blends, using both oaks in the same wine. We age our Bill Bailey Shiraz Cabernet Sauvignon, for example, in French and American oak for 18 months.
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