(InForum) - One of my students inquired about how wine came about being made in oak barrels. My immediate answer was, what else could be used, if you were in the Iron Age (800 to 900 B.C.)?

By the first century B.C., fully closed barrels were used for holding wine, beer, milk, olive oil and water. Being more durable and easier to handle than the very breakable clay pottery, the skilled craft and science of barrel making — or cooperage — came into being.

In addition to the added strength the wooden barrels gave to shippers, they were round and could be rolled to wherever needed. Finally, it was gradually discovered that storing wine in wooden barrels — especially barrels made from certain species of oak — would add a benefit to wine's taste.

This happy historical coincidence of the marriage of wood and wine has resulted in a better tasting product than could ever be achieved without it.

Another recognition in using oak barrels was that a process of "micro-oxygenation" was taking place, which reduced the astringency and helped improve the color and stability of the wine, and evolves the fruity taste and aroma into more complex ones. Resting in a barrel for a number of months will also help to settle out sediment (the "lees," a collection of grape skins and dead yeast cells), allowing the wine to be racked — moved from one container to another — to improve clarification of the wine.

To distinguish the difference between a wine varietal that is oaked and not oaked, check the market for "unoaked" or "naked" on the bottle of your favorite wine. No matter how blunt your taste buds may be, the differences will be immediately apparent.

The selection of the appropriate oak varieties from the many that exist in the world boils down to mostly two basic species: the white oak — Quercus alba — and the French or English oak — Quercus robur. The structural cellular arrangement of these two species of oak are unique in that they seal the best while still allowing microscopic infusion of oxygen.

Despite meticulous care in selecting a perfect specimen tree (grown on plantations specifically for wine barrels), then hand-splitting or sawing the staves, to the careful sanding and fitting of the staves in making the barrel, and finally toasting the inside to just the right intensity (light, medium or heavy), the useful life of a barrel is limited to two to three years, with some as long as five years.

As they age, they impart less of an impact on the flavor or character of the wine. After that point, they are considered "neutral" storage containers, and make no impact on the taste of the wine.

Shortcuts to the full oak barrel impacts can be achieved with oak chips or staves and be used as a cheaper alternative, but the most expensive wines in the world use full oak barrels to age wine.