BARRELS might be thought of as one tool in the winemaker's shop that can contribute flavors to wine. Depending upon many variables, barrels offer a broad palate of aroma and flavor possibilities. Tannins, as well as other compounds such as vanillin, leech from the wood into the wine. The porosity of the wood also allows a very small and gradual amount of oxidation to mellow the wine.
Although hardwood species such as chestnut, maple, walnut and others are used in some regions, white oak is by far the most commonly used and universally accepted for wine aging. Less than 5% of the known species of oak are used for wine barrels and less than 5% of the oak harvested is suited to barrel making, mostly due to knots, wormholes, and other imperfections.
Many variables affect the character and strength of oak aroma and influence flavors: the type and source of wood, the openness or tightness of the wood grain, barrel size, barrel age, degree of "toasting", length of time the wine is barreled, temperature and humidity of the barrel-aging environment, and treatments during barrel aging, such as stirring of the lees.
Common oak aromas or flavors can be vanilla, cream, caramel, toffee, nutmeg, almond, dill, cinnamon, allspice, cigar box, toast, licorice, coffee, charcoal, or tar; these odors are not common in wines not treated in oak.
The relative coarseness or tightness of grain and porosity varies by species, the forest where the oak is grown and also by how the green wood is dried and formed. America, Yugoslavia and France produce the great majority of oak barrels used in the wine industry. French oak is the most highly prized and most expensive. Allier, Limousin, Nevers, Tronçais and Vosges are all French forests famous for the oak they grow to make wine barrels. An average oak tree is over 170 years old when harvested.
Workers who make and repair barrels are
called coopers. Cooperage (tonnellerie in French)
refers to either their workplace or to a winery's stock of barrels. Large
producers may have their own in-house, but most wineries use the services
of independent coopers, whose services are also used by the brewers and
distillers. Many old firms, such as François Freres and Taransaud
have become well-known for their craft.
Harvested trees are split or sawn into
boards that are dried, either by seasoning naturally or by being placed
in a drying kiln. The staves are cut and bent, either by immersion in
hot water, exposure to steam, or over an open fire. Roasting over fire
caramelizes sugars that are naturally present in wood.
Although there are minor construction variations by region and by cooper, the common barrel shape of bowed sides with flat ends and bungholes in both an end and at the bulge apex serves practical purposes. The bulge allows the horizontal barrel to be rolled and spun for steering; it also serves as the collecting point for sediment, allowing the liquid to be racked off.
A new barrel might typically be filled with fermenting chardonnay for a few weeks, up to three months, to absorb some of the new tannins. That barrel might then be filled a red variety for a usual span of eighteen months, or even up to three years or more. The time depends upon the variet and the style the winemaker is trying to achieve. Red wine is not barrel-fermented often because of the difficulty in filling and emptying that would be made by skins, seeds, and other solids. Occasionally, a freshly pressed and still-fermenting red wine will finish its primary fermentation in barrels.
Over time and at a rate depending upon the temperature and humidity of the environment, some wine evaporates through the wood. The evaporated wine is often referred to as the "Angel's Share". Aging barrels must be periodically inspected for leaks and "topped" with fresh wine to replace lost wine and minimize "head space".
Historically, there are many sizes and size names that vary from region to region, with little standardization. Modern barrel sizes are 50-60 gallons (barrique - by far the most common), 80 gallons (hogshead - mainly used in Australia & New Zealand), 120-130 gallons (puncheon), and 265-318 gallons (Fuder or Stück - Germany). Smaller barrels have less wine volume in contact with more wood surface, so generally impart flavor characteristics faster.
Barrels require extra care and handling to ensure water tightness, prevent leaks, and prevent contamination before, during, and between uses. With good care, the average useful life of a wine barrel is about three years. After that time the wood tannins have been leeched out and the barrel becomes relatively neutral in terms of contributing much flavor to wine.
A sound used barrel can sometimes be shaved inside once or twice, depending upon the thickness of the staves, to remove used surface and expose new wood, extending its useful life for a vintage or two. Barrels over eight or ten years old are recycled as planters or firewood.
Wooden barrels (barriques) can cost
from US$500 to over US$1000 each for a barrique; puncheons or larger are even more expensive.
Barrel-aging adds the expenses of labor, time, and materials to wine production costs
and all are reflected in the price of wine to the consumer.