What does wood contribute to flavor and mouthfeel of wine?
How did this chocolate flavor get into my Merlot? And why does your Chardonnay smell so much like hazelnuts? For that matter, what was up with that dill pickle thing in the Cabernet we had last night?
The answer to a great number of questions about the taste and smell of wine is, the barrel did it. Barrels and wine have been joined at the hoop since Julius Caesar discovered them while invading France, and they have been the wine storage vessel of choice ever since. Their squatty, puffy shape is ideal for rolling, spinning and moving them around, and they're far more photogenic than stainless-steel tanks.
But what exactly do they do for the wine?
Barrels show up in the glass in three basic ways. First, wooden containers of all shapes and sizes allow a small amount of slow oxidation, integrating the wine's components and helping it "grow up"—get beyond the simple fruit of its youth. Second, oak contains wood tannin, which contributes to texture, mouthfeel, and the stabilization of color over time. Most important, wood—especially new wood in small barrels—adds aromatic and flavor elements that can make or break a wine.
The last half century has seen a dramatic shift away from aging wine in large, old, flavorless casks (German Fudern, Italian botti, etc.) and toward the smaller, newer, more flavorful 60-gallon barrels (barriques) used first in Bordeaux and Burgundy. Despite some resistance from traditionalists, the overall trend in fine wine, especially in the New World, has been toward new oak and plenty of it. (The one significant exception is aromatic white wine—Riesling, Gewürztraminer, Muscat—where wood flavors of any kind just get in the way.)
Oak barrels—these days, very little other wood is used—offer a whole universe of condiments and accents. Among the most common sensory descriptors for oak are vanilla, coconut, butterscotch, caramel, spice, coffee, chocolate, toasted bread, bacon and smoke—and that's a starter list. As a rule of thumb, if you taste something in a clean, young wine that isn't fruit, it probably came from a barrel—or in the case of mass-market wines, from oak chips or other barrel alternatives.
Barrels aren't interchangeable; choices have to be made to complement any particular wine. The starting point is deciding between old and new oak, French or American wood, and lighter and heavier toast levels.
Old and New
The "new" in new oak refers to the first time a barrel is used; the tree it came from may have been 80 years old, and the staves likely spent two or three years drying and seasoning before the barrel was constructed. On the first fill, a barrel will contribute more of its flavor compounds and tannins than in a second or third year of use. Some winemakers, like Oregon Pinot Noir specialist Ken Wright, think that second-fill barrels rarely have much oomph left, though they still aid in maturing the wine; others, like Paul Draper at Ridge Vineyards in Cupertino, California, count on an influence from barrels in their sixth or seventh year.
Using a high percentage of new oak requires an intensely flavored wine that can absorb the impact, or a conscious stylistic decision to have the oak be prominent, or both. Grape variety matters: Cabernet Sauvignon is much better at soaking up new wood than Pinot Grigio. It's not just red vs. white: Full-bore Chardonnay can benefit from a high proportion of new oak, but an oaky Beaujolais would be silly.
Though winemakers draw the line in different places, everyone agrees that excessive oak is too much of a good thing. "Wine can't depend on oak for quality or interest," says Paul Draper. "That means your vineyards are mediocre." Wright produces a long list of single-vineyard Pinots, so he can't afford to have them all taste the same. He employs a high proportion (65 percent) of new oak, but still says, "If you notice the oak in my wines, I've gone too far."
Among major red wine regions, the Rhône is probably the most cautious in keeping oak off center stage, relying on older and often larger barrels. California wine, says Mark Heinemann, North American marketing manager for Demptos international cooperage, "is the most oaked in the world; it's something people expect stylistically. Riper fruit complements higher new oak percentages."
French and American
American white oak is a different species (Quercus alba) from the French standards (Quercus ruber and sissiliflora), but the great divide in the past was in the barrel-making. Thirty years ago, the prime purchasers of American oak barrels were Bourbon distillers, and the wine industry got the leftovers. American coopers dried their barrels rapidly in kilns, while the French let the staves dry in the open air, encouraging the interaction of beneficial molds and enzymes to season the wood in delicious ways. American winemakers and coopers got the message, and the sensory gap has narrowed considerably.
Within each country, of course, there are regional and forest differences—Allier, Nevers, Tronçais and Vosges in France; and Minnesota, Missouri, Pennsylvania and Alabama in the U.S. Hungarian oak has also made a splash in the marketplace. Another fine distinction has to do with the grain of the wood: wider-grained wood is more porous and thus more assertive, while tighter-grained wood is more restrained in its impact. And of course, since France is involved, there is the question of the terroir from which the oak emerges.
Still, there are some preference patterns. Chardonnay and Pinot Noir are almost never matured (or in the case of Chardonnay, fermented) in American oak, which is generally considered too rough and tough.
French oak is also the norm for Cabernet Sauvignon, not just in Bordeaux but in Napa. At Chimney Rock in Napa's Stags Leap District, winemaker Elizabeth Vianna says, "French oak has different aromatics—more higher-end vanillin, the clove family, chocolate, coffee; American oak tends to show coconut oil and dill aromas that don't work for our fruit." Chimney Rock continues to do trials with American barrels. Draper couldn't resist mentioning, however, that in a recent tasting with a number of Masters of Wine, few identified the Ridge Monte Bello Cabernet as a New World wine, let alone that it is aged in 100 percent new American oak.
American oak gets plenty of use with Zinfandel, Petite Sirah and Syrah in California, as well as in the Rhône, in Spain's Rioja, with Australian Shiraz and Cabernet, and with full-bodied Latin American reds. One major reason for its international popularity is price: American oak barrels cost somewhere between half and two-thirds as much as their French counterparts, which currently go for $600-$700.
Fire-toasting the insides of barrels is the final step in fine-tuning their flavor and aroma profile. Toasting provides a buffer between the alcohol of the wine and the tannins of the wood, moderating the influence of raw timber and adding some new characteristics. A light toast may accentuate sweetness and spice; a medium toast can provide honey, toffee and almond; a heavy toast might add chocolate, smoke and burnt sugar. Toasting can be limited to the staves or include the round heads at the ends of the barrel for more impact. Again, variation abounds: one cooper's medium toast is another's heavy.
How all these alternatives can interact with the intricate flavor chemistry of wine is devilishly complex, which is why wineries generally buy from multiple coopers and multiple forest sources and do constant trials and tweaks to their barrel programs.
Some matches are pretty obvious. Winery X's Chardonnay benefits from an infusion of vanilla and spice—the signature of contemporary Chardonnay. A dollop of coffee flavors would be out of place, but it's right at home in the winery's Syrah, along with some smoked meat, roasted nuts and mocha. A Syrah offering only sweetness and a little spice might be okay for an entry-level wine, but would disappoint serious Syrah fans. The slight burnt flavor from a few heavy-toast barrels in the blend of an upscale Cabernet could be quite intriguing; that same flavor in a Sauvignon Blanc would be peculiar. Nutmeg might be nice in both.
Other choices aren't so intuitive. While Pinot Noir cozies up to the gentler charms of French oak, it also seems to prefer fairly heavy, muscular toast levels—go figure.
The odds that you can taste a wine and identify the cooper and the forest are slim. But the chance that barrels had something important to do with how the wine smells, tastes and feels in your mouth is awfully good.