How does oak help in wine aging?

Wine barrels are predominantly made of oak if aging is desired. According to Simi Winery from California, the existence of open faced, wooden buckets through coopering dated back to as early as 2690 BC in Egypt. The Fully-closed barrels were first developed during the Iron Age (800-900 BC). By the first century, wooden barrels were widely used to hold wine, beer, milk, olive oil which turned out better than storing them in clay vessels. The increased use of wooden barrels created the need of cooperage (i.e barrel-making), eventually replacing the use of clay vessels as the major storage tools.

There are many different types of oak – French, American, Hungarian – all play a role in maturing the wine through a gradual oxidation process and the chemistry exchange between the wine’s phenolic components and the wood. What oak does to a wine is similar in our modern day of slow cooking whereby flavors and texture of the oak is assimilated into the wine. Under the effect of oxygen, the phenolic compounds of the wine change color from red to brown, then polymerize and precipitate. When there is too much oxygen, the alcohol will be turned into acetaldehyde which results in a flat taste. However, when the excessive oxygen is removed, the acetaldehyde will interact with the tannins and the flat taste disappears.

Oak is known to impart certain flavors or texture to wine during barrel aging. Some of the well known flavors are vanilla, toasty, tea and tobacco .etc. These are a result of the extraction of non-flavonoid phenols extracted from the oak - vanillic acid and ellagic acid. There are also materials containing hdrolyzable lignin and small sugar molecules like pentoses.

The barrel manufacturing techniques and type of oak affect greatly the amount and quality of flavor/texture impart to the wine. American and French coopers have different style of making the barrels, beginning with the type of oak used (Quercus alba vs Quercus robur), the toasting method (natural vs kiln, degree of toasting), staves binding (boiling water vs gas or fire), and the list goes on. Overall, cooperage is an extremely complicated craft and plays a critical role to the final quality of the wine.

Reference: Dr Yair Margalit (1996), Winery Technology & Operations published by Wine Appreciation Guild.

By Cher Lim
Wine Treasures Pte Ltd
http://www.wine-treasures.com
Email: limce@singnet.com.sg