During walk-around or sit-down tastings wine writers and occasionally connoisseurs ask wine makers or winery representatives what type of barrel a particular products was aged in.
Often the answer is European oak, but this is an imprecise answer as there are several European countries that produce suitable oak for wine aging, of which France is the most famous, followed by Slovenia, Hungary, Russia (Krasnoyarsk), and Romania.
In France Limousin, Troncais (used for cognac aging), Gascony (for Armagnac aging), Allier, Vosges, Jupille rank as the best.
European oak is called quercus robur. It is tight grained and imparts a fien
flavour and texture to the wine. The tighter grain of quercus robur allows for a more gradual integration of flavours in the wine.
American white oak is called quercus alba and it grows in several states. Teher
are 26 quercus alba species of which 25 belong to the same family. American oak is coarse grained and imparts a pronounced vanilla flavour to the wine and makes it taste coarse and rough.
Most Australian shiraz is aged in American oak barrels as they cost half as much as European oak.
Australian wine being high in alcohol can tolerate the coarse grain better but
quality oriented winemakers always prefer French oak.
There are visual differences that experts distinguish on live trees, and can establish the exact specie using specially designed equipment.
In the U.S.A, forestry companies cut oak trees in different states from wild forests and sell them to barrel makers, but all the oak sold may not belong to quercus alba family.
The following states are well known for their quercus alba – Missouri, Minnesota, and Wisconsin.
During the 12th century the government of France decreed that the same specie must replace any oak tree cut, and today, eight centuries later, the majority of French oak is quercus robur. A small portion of French oak belongs to quercus petrae.
Forests in France are public property and government sells the right to harvest them. Every tree cut is pre-sold to a barrel maker, and in many cases this is done years before harvest, hence the elevated cost.
American oak in general is loose grained and contains more vanilla, whereas French oak and in general European oak (i.e Hungarian, Slovenian, Romania, and Russian) are tight grained and impart less vanilla flavour, but allow for slower oxidation.
Allier, Vosges, Limousin, Jupille, and Troncais are the most famous French oak forests. Limousin and Troncais are often used to age cognac and armagnac.
Winemakers prefer Allier for cabernet sauvignon, blends of cabernet sauvignon, merlot, cabernet franc; Vosges for merlot, and Allier for chardonnay.
American white oak barrels seem to be more suitable for aging baco noir and shiraz.
In the U.S.A., forests are now being planted with specific species of white oak, but it will take at least a century for these trees to grow tall enough for barrel making.