From Forest to Barrel to Bottle


Understanding the Oak to Wine Connection
By Kirstin Jackson

Oak’s role in winemaking can be difficult to grasp. In one tasting room, a winery employee pouring you a splash of $90 reserve red implies that aging a wine in anything less than new French oak barrels is an offense to the grape, centuries of viticulture, and mothers around the world. A little further down the road at a winery where wine is housed in stainless steel, you hear that using wood is a corruption of the grape, and an affront to the precious palate of the wine consumer.

The varying opinions about oak storming the wine trade tell us one thing in particular: There is a lot to know about the impact an oak barrel has on wine. Not only does oak affect a wine’s flavor, texture, complexity, and ability to age, the manner in which it does all this is determined by the forest from which it comes, toasting levels, and how closely its chemical composition resembles that of a Christmas cookie.

To explore the mystery of this great tree and what it does to our wine, I consulted with two East Bay cooperage owners.

Peter Molnar, who lives in Albany, has been a partner in Kádár Hungary barrel cooperage since 1994, and is a partner of Obsidian Ridge, Kazmer and Blaise, and Molnar Family wineries in Lake County and Carneros. Jerome Aubin is the owner of Oakland’s Aubin Cellars/Verve Wine and Artisan Barrels, a firm that represents five wine barrel cooperages from France, Hungary, and the United States.


To make the classic Bordeaux- or Burgundy-sized barrel, Molnar explains, an oak tree is harvested and its trunk cut into meter-long sections that are trimmed to form staves. At high-end cooperages these will be stacked outdoors for at least two years to season, during which time microbes present in the environment start to work on the oak, resulting in a form of fermentation. After seasoning, the staves are pulled together with metal hoops into a partial barrel shape, which is then toasted: An open flame is applied to the interior, causing it to scorch, or even char, depending on the taste being sought from the wood. Then a single riverbank reed is placed between each stave and the next, the hoops are tightened with tremendous pressure, and another barrel enters the world. Nearly all fine oak cooperages produce barrels in the same manner.


Hungarian, American, and French oak trees, explain Molnar and Aubin, taste and function differently. Even the location where the staves are seasoned (fermented) affects the flavor of the oak. Molnar compares this to the way sourdough starters raised in different locations will affect the flavor of bread. He says that winemakers know this, and use wood as a winemaking tool, selecting barrels according to how they want to highlight their grapes and vineyard terroir. The oak’s terroir—soil, climate, and seasoning—along with its species and the levels of toasting, are factors in the winemaking process. For example, a zinfandel aged in American oak may emerge with a coconut flavor, a syrah housed in Hungarian oak could taste spicy and bacony, and a pinot noir aged in French oak is likely to seem quite polished.

According to Aubin, wood from the sessile oak (Quercus petraea) that grows in France is of exceptionally tight grain and provides much finesse, complexity, and tannins to a wine. It is a lighter type of oak, commonly used with pinot noir and other delicate varieties to prevent the quiet nose of such grapes from being overpowered by the scent of the wood. French oak is also the go-to wood for high-end wines that vintners want people to lay down before drinking. This is because the high tannin content such oak imparts to a wine helps it age. Most European producers still primarily use French oak—or a mix of French and tight-grained Hungarian—for the bigger European wines such as Barolo, Brunello, Burgundy, and Bordeaux.

Barrels made from American oak, on the other hand, are not known to help in the aging of wines. Rather than providing subtle tannins, America’s coarser-grained version of the sessile oak smoothes a grape’s rough edges and provides a softer finish. Used excessively, it can overpower a grape’s flavor. While some Spanish producers use American oak for the vanilla, sugar cookie, and coconut flavors it imparts to their wines, many will also rely on oak from elsewhere to provide their juice with age-worthy characteristics.

Hungarian sessile oak is nearly as fine-grained as that which grows in France. When winemakers don’t want to pay what French craftsmanship and the higher values of French wood demand, many use Hungarian oak, most often from the forests of Tokaj. Cold winters in this region and similar slow forest growth to that in France, says Molnar, produce the finer-grained trees. Hungarian oak is also known for lending creamy butterscotch, bacon, and spice notes.

Tighter grains aside, why does one country claim that their oak lends flavors of vanilla and cinnamon, and another says their oak—even of the same species—gives tastes that are polished and elegant? What explains this difference? Science suggests it is the phenylpropanoids, and not just a subconscious recollection of the morning’s pastry. When Molnar had chemists evaluate the different chemical compounds in his oak, years of scent claims were supported.

That freshly baked sugar cookie scent wafting from a zinfandel relates to the American oak it was aged in, which is heavy with vanilla compounds. That clove and cinnamon scent from a Hungarian oak aged wine? Molnar’s study says to credit eugenol, a phenylpropanoid compound also found in purest form in essential oils of clove, cinnamon, and nutmeg. The butterscotch character from Hungarian oak? Furfural compounds. The lack of heavy scents from French barrels? Quieter phenylpropanoids.

Impressive, but while scientists can pinpoint varying phenylpropanoids levels in the trees, few attempt to explain why they differ in trees from country to country. Cooperages point to terroir, the natural variations of earth and soil that occur from place to place, explains Aubin.


Toasting, says Molnar, “helps to mellow raw oak flavors and urges the wood to reveal flavors in different ways.” The way the staves are toasted, like the mix of phenylpropanoids in the wood, will affect a barrel’s flavor and can amplify certain characteristics in the final product.

Toasting caramelizes the sugars in wood. The same species of oak toasted at varying levels of heat can produce different flavors. It’s like the difference between an onion cooked slowly with low heat and one cooked quickly on high. A slowly caramelized piece of oak reveals sweeter characteristics, and a stave toasted quickly with high heat will produce meatier, bacon-like characteristics. Vintners can dictate barrel toast to order.


Aubin says he helps wineries choose a cooperage according to the needs of their wine. A winemaker who has paid top prices to obtain grapes from the most coveted vineyards in California is going to work hard to make sure that the vineyard profile is expressed in the wine. For this, he’ll go to someone like Aubin, who can help choose the appropriate cooperage. “I’m trying to allocate to each of their vineyards a certain cooperage profile. My clients want to show the vineyards’ layers, and sometimes even more layer complexity is offered by using more than one cooperage. Certain coopers work better with certain vineyards than others, because they offer a certain stylistic approach on that particular vineyard and wine.”

Both Aubin and Molnar agree that overall, Hungarian oak is a good pairing for elegant syrah, chardonnay, and cabernet. French oak barrels are king in Burgundy and Bordeaux. French is the most favored barrel in high-end winemaking everywhere, sometimes simply because tradition holds strong. An exception is zinfandel, where American oak is almost always used for its sweeter vanilla spice traits. Australia and South Africa buy many American barrels for their deep shiraz (syrah’s name down under) rather than Hungarian barrels that many love for syrah because American oak helps to produce the jammy, concentrated flavors that pleases their palate.

But nothing is set in stone. Cooperages merge and a winery’s barrel preferences change. Molnar’s Kádará cooperage was recently invited to join forces with the celebrated French Taransaud firm, for example, and now Hungarian oak has piqued some interest again among winemakers traditionally devoted to French barrels.


Oak chips, a byproduct of stave production, have become a popular and inexpensive way to put an oak flavor into wine, and some winemakers even ask what it is that a barrel can do that a chip cannot. besides provide snob appeal.

Barrels are a huge expense for winemakers: each holds only around 230 liters and has a useful life of just three to five years. At $350 a pop for American oak on up to $1,000 for French, the costs start to add up. Thus the appeal of chips.

Both Aubin and Molnar agree that wood chips are an acceptable tool for everyday table wine, and Molnar even commends the Gallo company for mastery of the wood chip in their under-$15 collection. But Aubin and Molnar also agree that chips fall short for producing a quality wine capable of aging or evoking awe at the dinner table.

If expense is the main concern, Aubin points out, there are ways to give wine the oak characteristics without reverting to chips. Such as the 900-gallon oak cask his company makes: It sells for under $12,000 and will last for 10 to 15 years. And critics are beginning to accept the idea that not all fine wines need expensive barrels to age in.

But both cooperage heads say there is more to a barrel than just tradition. First, chips do not allow oxygen to work its magic on the wine. They don’t gently surround the fermenting juice, as does a barrel, which allows for the slow evaporation of around 10 percent of the wine, Aubin explains. But more importantly, the wine loses out on subtle micro-seasoning, slow extraction of oak, and tannin accumulation that an all-wood vessel provides. Molnar puts it another way.

“Using chips rather than barrels is like just adding barbecue sauce to meat rather than barbecuing—it will add flavor, but not complexity. You lose out on the much more complex molecules built over time.”


Reading about differences in oak and barrel will get one only so far. Tasting is the key to understanding oak’s impact, and enjoying the variations. The following wines provide good examples of how oak from different countries affects the final bottled product. All of these wines are available for purchase in the East Bay or through the winery websites.


’07 Obsidian Ridge Syrah, Lake County Hungarian oak
’05 Verve Cellars Sonoma or Columbia Valley Syrah French oak
’07 Fort Ross Chardonnay, Fort Ross Vineyard, Sonoma Coast French oak
’07 Molnar Family Chardonnay, Poseidon’s Vineyard, Carneros Hungarian oak
’05 Silveroak Cabernet, Alexander or Napa Valley American oak
’05 Long Meadow Ranch Cabernet Sauvignon, Napa Valley French oak

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