Oak and Wine - What's The Story?
Oak has a big impact on a wine’s style. It does not just add flavor and aromas. Oak also influences wine texture, helps integrate its tannins, stabilizes it, and improves its aging potential.
Wine has been part of human civilization for more than 7,400 years. However the wood barrel has only been used in more modern times. Archeologists say barrels started significantly replacing ceramic vessels around 200 AD, with the earliest evidence of iron tools to make barrels around 100 BC.
It is notable that only about 2% of wines in the world today are aged in barrels. In general these are the best wines, and are predominantly red wines.
Barrels are expensive, usually exceeding $1,000 each. French oak barrels are most expensive, partly because their wood structure requires splitting along the grain. American oak can on the other hand be sawed, giving a higher yield.
The story of a barrel starts in the forests. Oak trees are influenced by climate, soil, and genetics. Only 3 of more than 600 species of oak trees throughout the world are suitable for making oak barrels.
French forests are used most often, followed by American, and occasionally other regions such as Hungarian. The characteristics of oak for barrels vary from forest to forest within the same region. Capillary structure varies a lot between French and American oak. That has an influence on micro oxidation during wine aging.
Cell density within the wood can vary from year to year, which affects wood-grain permeability, flavors, and aromas. In France trees between 150 and 300 years old are used, and only a section between about 4 to 14 feet above the ground is used to avoid knots that could cause leakage.
The story gets more complex when the wood is harvested, aged and processed. A barrel is made from about 30 staves, with the widest stave containing the bung.
If the staves used to make barrels are aged outdoors out of the sun they are “heart staves”. Heart staves provide aromas of coconut, violet, cinnamon, black pepper, and nuts.
Sun staves on the other hand are aged with sun exposure. They generate vanilla, nutmeg, paprika, cumin and dry fruit aromas. Our Tamarelli Vineyards wines are aged in barrels that include both heart staves and sun staves.
More than 17 specific compounds are formed in the staves (all are derived from the oak’s lignin and hemicellulose). It is not unusual for winemakers to use a variety of barrel types from a variety of coopers (barrelmakers) to optimize wine quality.
Another complexity is the type and amount of toasting of the interiors of barrels. Toasting is done over an oak-chip fire. It can be regular, medium, or strong. It can vary depending on whether the barrel ends are toasted in addition to the sides. Heat caramelizes sugars in the wood, reducing tannins and releasing aromatic aldehydes. Degrees of toasting provide differing flavors and aromas.
Then the story diverges based on whether all new barrels are used, second use barrels are used, or a combination.
For our Tamarelli Vineyards wines we use a combination of new French-oak barrels and once-used French-oak barrels.
Farming (viticulture) has to produce great grapes in order to make great wines.
However oak plays a major role in the winemaker’s tool kit for making great wines from great grapes.