The wine barrel is as ubiquitous in the popular imagination of wine as the vineyard itself. At a glance, rows of stacked wine barrels evoke the romance of an older era, an era defined by the natural materials, hands-on labor, and the slow, steady transformation of pressed grape juice into delicious wine beneath the barrel’s wooden surface.
But while the barrel may seem a quaint holdover in today’s modern era, oak plays an indispensable role in winemaking, representing important contributions to the flavor, texture, and color of the finished wine.
Nowhere is this more true than in Burgundy, a region that epitomizes the continued merit of traditional winemaking methods. Both Pinot Noir and Chardonnay benefit from a period of maturation in oak barrels, and after centuries of experimentation, Burgundian winemakers have turned this practice into an art.
Oak’s contributes to wine’s flavor
First and foremost, oak imparts distinctive aromatic compounds to both red and white wines. French oak in particular, used throughout Burgundy, is renowned for its delicate, decadent, fragrant aromas of:
- Baking spice
- Vanilla
- Caramel
- Cream
- Honey
- Nut
- And herbaceous spice
In wine drinking lingo, these are known as “secondary aromas”. In contrast to tight-grained French oak, American oak imparts much more sweet and prominent aromas of vanilla, dill, cream soda, and coconut. In both instances, the perceptibility and toastiness of these flavors depend in large part on how charred the wood was during the barrel-making process.
Oak’s contribution to texture
In addition to its aromatic compounds, oak also contains tannin, a naturally occurring organic molecule responsible for that dry, puckering sensation you’ll often notice in reds.
When wine comes into extended contact with oak, some of those tannins are drawn into the wine, bolstering the tannins already present in reds and introducing a bit of structure and refinement into otherwise tannin-free whites.
As with aroma, the tannins imparted by French oak tend to be on the smoother, softer, silkier side, while loose-grained American oak imparts bolder and more astringent textures.
Due to the porousness of the wood, oak also allows for a very gradual oxygen exchange between the inside and outside of the barrel. This controlled oxidation smooths out both new and existing tannins, resulting in more soft and supple wines.
A further softening effect comes from malolactic fermentation, a process that is often (but not always) carried out during oak barrel maturation. Malolactic fermentation converts harsh malic acids into soft and creamy lactic acids, and is a step used in the making of both red and white Burgundy.
How oak impacts wine color
Last but not least, the use of oak barrels stabilizes color pigments in red wine. The new tannins introduced by the oak bond and anchor color molecules in the wine (known as “anthocyanins”), meaning that oak-aged reds retain a lusher and more vibrant color throughout their lifespan.
In contrast, oak imparts an attractive golden and pale straw color to white wines, a color that becomes deeper and more prominent as the wine ages.
What it all comes down to
Without oak barrels, wines would, on the whole, be a little more harsh and astringent, unidimensional, and pale. With flavor and color additives rightfully forbidden in French winemaking, oak represents a way of bolstering nuance and complexity without sacrificing the integrity or character of the wine.
The biggest cost of using oak barrels is financial. The typical Burgundian barrel holds about 60 gallons of wine, or 288 bottles, and with each use, the influence of the oak diminishes as flavors are leached out, and the pores gradually obstructed.
For this reason, winemakers must regularly switch out their barrels if they want to maintain the characteristic flavor profile. But with French barrels coming in at about $1,000 a barrel (twice as much as their American counterparts), this represents another one of the significant overhead costs that go into the pricing of a bottle of Burgundy. But wine lovers around the world all agree: oak is worth the expense.