Due to the perishable nature of wood material it is difficult to trace the usage of barrels in history. The Greek historian Herodotus noted that ancient Mesopotamians used barrels made of palm wood to transport wine along the Euphrates. Palm is a difficult material to bend and fashion into barrels, however, and wine merchants in different regions experimented with different woods to find a better wood source. The use of oak has been prevalent in winemaking for at least two thousand years, first coming into widespread use during the Roman Empire. In time, winemakers discovered that beyond just storage convenience that wine kept in oak barrels took on properties that improved the wine by making it softer and in some cases better-tasting. The porous nature of an oak barrel allows some levels of evaporation and oxygenation to occur in wine but typically not at levels that would cause oxidation or spoilage of the wine, small amounts of oxygen are allowed to pass through the barrel and act as a softening agent upon the tannins of the wine. The chemical properties of oak itself can have a profound effect on the wine. Phenols within the wood interact with the wine to produce vanilla type flavors and can give the impression of tea notes or sweetness. The degree of "toast" on the barrel can also impart properties affecting the tannin levels of the wine as well as the aggressive wood flavors. The hydrolyzable tannins present in wood, known as ellagitannins, are derived from lignin structures in the wood. They help protect the wine from oxidation.
Many different woods have been tried (including chestnut in Italy and eucalyptus in Australia,) and some continue to be used, but there is no question that oak produces the most sophisticated results. And not just any type of oak, Fine grained oak from French forests is held to be the best. American oak is regarded as more robustly flavored but can be subtle when skillfully selected, seasoned and coopered. New oak barrels give richer flavors (not just the taste of oak, but a more complex character) and a richer texture. White wines can readily be fermented in these small containers, but with red wines, the skins become a problem. They rise to the surface and need constant pushing down (as they would in any fermentation vessel) so that they don’t form a cap on the wine. For this reason, red wine is usually aged, but not fermented in barrels, though some producers transfer the wine, minus the skins to barrels as soon as the maceration (the color and tannin extraction period) is complete, but before fermentation is finished. Shortcuts to oak, as a means of imparting its characteristics without incurring the cost of expensive barrels (In 2007 for example, the price for a standard American oak barrel was $270 USD, French oak $600 USD, and Eastern European $480 USD) include suspending oak planks (staves) or bags of oak chips in tanks or vats of wine during fermentation or aging. This can give a douse of oak flavor, but the results are never as subtle or rich as in wine nurtured through the same processes in a high quality French oak barrel. Prior to 2006, the practice of using oak chips was outlawed in the European Union. In 1999, the Bordeaux court of appeals fined four wineries (including third growth Chateau Giscours) more than $13,000 USD for the use of oak chips in their wine. Oak essence also exists, but is mostly illegal.
Oak Chips in a Vat of fermenting Chardonnay
Watch this video about wine barrel production...
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