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The use of oak in wine plays a significant role in winemaking and can have a profound effect on the resulting wine, impacting the color, flavor, tannin profile and texture of the wine. Oak can come into contact with wine in the form of a barrel during the fermentation or aging periods. It can be introduced to the wine in the form of free floating oak chips or as wood staves (or sticks) added to wine in a fermentation vessel like stainless steel. Oak introduced in the form of a wine barrel can impart other qualities to the wine through the process of evaporation and low level exposure to oxygen.

Many winemakers choose to ferment their wine in oak as oak barrels tend to soften the wine and impart characteristics that improve the flavor of the wine. The oak wood used for these barrels is mainly derived from France and the United States although there are many countries from which oak barrels come including Spain, Hungry, Austria, and many more. American oak passes on prominent characteristics to the wine, while French oak tends to lend more subdued characteristics. Each type of oak imparts notes of vanilla, caramel, cream, clove, smoke, and fresh cracked black pepper. Another important trait passed over from the oak is the tannin found in the wood - tannins from American oak are sharp while French oak provides more subtle tannins.

Some other differences to note are that American oak tends to be more intensely flavored then French oak with more sweet and vanilla overtones due to the American oak having two to four times as many lactones. Winemakers that prefer American oak typically use them for bold, powerful reds or warm climate Chardonnays. Besides being derived from different species, a major difference between American and French comes from the preparation of the oak. The tighter grain and less watertight nature of French oak encourages coopers to split the wood along the grain rather than saw. French oak is then traditionally aged or "seasoned" for at least two years whereas American coopers will often use a kiln-dry method to season the wood. Long periods of outdoor season has a mellowing effect on the oak that kiln-dry methods have difficulties replicating. The sawing, rather than splitting, of American oak also enhances the differences between the two styles due to the rupture of the xylem cells in the wood which releases many of the vanillin aromatics and lactones responsible for characteristics like the coconut notes.

The length of time that a wine spends in the barrel is dependent on the varietal and style of wine that the winemaker wishes to make. The majority of oak flavoring is imparted in the first few months that the wine is in contact with oak but a longer term exposure can effect the wine through the light aeration that the barrel allows which helps to precipitate the phenolic compounds and quickens the aging process of the wine. New World Pinot noir may spend less then a year in oak. Premium Cabernet Sauvignon maybe spend two years. The very tannic Nebbiolo grape may spend four or more years in oak. High end Rioja producers will sometimes age their wines up to ten years in American oak to get a desired earthy, vanilla character.

These may not seem like important factors at first, but as you explore the world of wine you'll begin to notice subtle differences. California Chardonnays are often aged in toasted oak for a long period of time, which imparts the intense vanilla flavor that many have grown to love. But the fruit flavor drops off almost as soon as the wine is swallowed, a problem which many call "overoaking" a wine. Meanwhile, Chardonnay wines from Chablis in Burgundy have subtle vanilla flavors from shorter barrel storage, which allows the wine a crisp finish with fruit flavors that linger in the back of the throat long after being swallowed.

White wines that are fermented in oak often have a pale color with an extra silky texture. White wines that are fermented in steel and then matured in oak will have a darker coloring due to the heavy phenolic compounds that are still present. Flavor notes that are common descriptions of wines exposed to oak include caramel, cream, smoke, spice and vanilla. Chardonnay is a variety that has very distinct flavor profiles when fermented in oak that include coconut, cinnamon and cloves notes. The "toastiness" of the barrel can bring out varying degrees of mocha and toffee notes in red wine.

While oak aging is time honored and respected some wine lovers prefer wines that are fermented in steel barrels. These wines often have a more fruit-forward flavor and can be more true to the actual grape flavor. In these wines, we may feel slighted by the minimized tannins and lack of barrel spices, but these wines exude a more true expression of the grape. Oak aging can be seen as a more old world practice while steel aging will tend to be seen more in the new world as in New Zealand and Australia. One is not necessarily better than other. It is all a matter of preference. If you prefer a little more complexity and like more tannic wines go for an old world wine that is oak aged. If you like a more fruit forward wine then stick to a steel aged wine from South America or New Zealand.