Concept card Process
Barrel and vessel ageing
In one sentence
The time a wine spends after fermentation in a vessel (tank, large cask, barrique…) that shapes its texture, its aromas and how it ages.
The oxygen a vessel lets through
Less oxygen
Stainless steel tank
It does not reproduce a barrel's slow passage of oxygen.
Barrel, five wines old
About 10 mg/L a year: use sharply cuts the flow.
New barrel
28 to 36 mg/L a year, depending on how it is closed.
More oxygen
Key points
- Oak plays two separate roles: it gives the wine aromatic molecules, and it lets oxygen through slowly.
- The more a barrel has been used, the less oxygen it lets through: after five wines, far less than when new.
- Left in contact with the wine, the lees break down; stirring (bâtonnage) puts them back in suspension.
- Oak chips and staves in a tank bring the taste of oak, not a barrel's slow passage of oxygen.
What it changes in the glass
- Vanilla, coconut, toast, clove: notes of new oak (toast can also come from the lees).
- On the lees, the wine grows rounder: astringency and bitterness are felt less.
Not to be confused with…
A length of ageing
A stated length says nothing of the wood's age or the share of new oak: over the same time, the oxygen received can vary widely.
In the traditional method, the lees come from the second fermentation, in the bottle itself: the wine ages on them before disgorgement.
Two reds each spend 18 months in barrel: one in new barrels, the other in barrels that have already aged five wines. Which took in more oxygen through the barrel?
One question to test yourself: it does not count towards your progress.
The barrel as a membrane
Oak lets oxygen through at a slow, steady rate that neither steel nor concrete reproduces on its own. A study published in 2021 in the journal OENO One measured it on a new barrel.
11.4 mg/L/yr
through the wood of a new barrel (2021 study)
14.4 mg/L/yr
counting the oxygen already stored in the wood's pores
- The study cites older measurements (Vivas and Glories, 1997): 28 to 36 mg/L a year for a new barrel, depending on how it is closed.
- By the same measurements, a barrel that has already aged five wines lets through only 10 mg/L a year.
- These 1997 figures do not compare directly with the 2021 ones: they come from another study, using different methods.
Where the oxygen gets in: an open question
On how oxygen gets in, two teams cited by the 2021 study disagree: they do not measure the same thing in the same way, and the study reports the disagreement without settling it.
- Vivas and Glories (1997): 63% through the joints between staves, 21% through the bung, 16% through the wood.
- Del Alamo-Sanza et al. (2017): 46 to 72% through the wood itself.
What the oak contributes
The taste of new oak comes down to a few molecules, formed or released as the staves are seasoned and toasted. How strong they are depends on the oak's origin, its seasoning and the toast the cooper chooses.
- Oak lactones, markedly more abundant in American than in French oak: coconut.
- Vanillin, released as the wood's lignin is toasted: vanilla.
- Furfural, from toasting: toast and almond, stronger at a heavier toast.
- Eugenol, released as the staves are seasoned and toasted: clove.
Lees, chips and what a length of time says
- As the lees break down, they release mannoproteins and polysaccharides: the texture rounds out and the wine holds up better against oxidation.
- Chips and staves offer more contact surface than a barrel for the same amount of oak; they are often paired with controlled micro-oxygenation in the tank.
- In Bandol, reds are aged at least 18 months in casks or foudres: a floor set by the rules, not a measure of what the wine gains from it.
To learn it in depth
Related reading
Sources (5)
- Academic publicationOxygen gas transfer through oak barrels: a macroscopic approach— OENO One
- Academic publicationVolatile Compounds in Spanish, French, and American Oak Woods after Natural Seasoning and Toasting— Journal of Agricultural and Food Chemistry
- Reference bookThe Oxford Companion to Wine— Oxford University Press
- Reference bookUnderstanding Wine Chemistry— Wiley
- Reference bookHandbook of Enology, Volume 2: The Chemistry of Wine — Stabilization and Treatments— Wiley