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Andrei Prida,1
Jessica Drinkine-Magneux,3
Regis Gougeon,2
David Chassagne2,3
1 - Tonnellerie Seguin Moreau,
Z.I. Merpins, Cognac, France
2 - Institut Universitaire de la Vigne et du Vin
“Jules Guyot,” E.A. 581 EMMA,
Université de Bourgogne, Dijon, France
3 - CESEO (Cellule d’Expertise Scientifique en
OEnologie), Institut Universitaire de la
Vigne et du Vin “Jules Guyot ,”
Université de Bourgogne, Dijon, France
Barrel ageing is a key stage in producing great wines. Two major phenomena
occur during barrel ageing: one consists of oxidation of certain substances
in wines due to oxygen penetrating into the barrel and the other is the diffusion
of extractable compounds from oak wood into the wine. These substances modify the
wine’s aromas and flavors, adding complexity and hints of “coconut,” “toast,” “vanilla” etc.3
PHOTO ABOVE: Volume in the water-immersion tank is changed every seven barrels,
through continuous introduction of new water (de-chlorinated, filtered, and
UV-sterilized), and removal of water charged with oak extractives. Each barrel
spends less than one hour in the tank prior to fire-bending.
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Photo (left): Barrel immersion in hot water prior to bending.
Figure 1 (ABOVE): Barrel production process. A – bending following
heating over a fire; B – bending following heating by immersion.
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Once the extractable compounds from the wood have been released into the wine, they may be modified
by chemical and enzyme reactions.7,9,10,11,2,4 Furthermore, the macromolecular
structure of oak wood may absorb certain constituents from the wine.1,8 These
phenomena result in marked organoleptic changes in the wine.
The complexity of barrel-ageing phenomena and their impact on wine quality make
these containers valuable winemaking tools. Winemakers’ objectives change to suit
market tastes. The current trend in the winemaking world is to make barrel-aged
wines with complex, fruity flavors, and relatively discreet oakiness. This trend
is most marked among independent winegrowers, who want their wines to express
their terroir, rather than any “universal” taste.6
Some coopers use immersion in hot water to prepare the raised (assembling of the
staves in the shape of the barrel before staves are bent and heads are inserted)
barrels for bending, but this process is much less widespread than traditional
heating over a wood fire.
The immersion method consists of soaking raised barrels in hot water, then bending
the staves rapidly to form the barrel before it is 
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toasted. The only difference
from the traditional process is that heating over a fire
prior to bending is replaced by immersion in
water, and then the process continues with toasting.
The first objective of this technique is to reduce stavewood breakage with water
immersion before bending, to minimize the waste of broken oak staves occurring from
bending following heating over an open fire.
However, this is by no means the most important aspect of the process. The adsorption
of water by wood, extraction of wood components, and heat transfer in the wood-water
system formed by immersing the barrel in hot water, then toasting wood with a high
humidity level drive different kinetics in the production of compounds from toasting
and degradation of wood compounds over fire from those that occur after traditional
fire bending prior to toasting.
It is noteworthy that during traditional fire toasting coopers spray some water on
the inside of the barrel in order to prepare the barrel for bending. However, contrary
to water immersion, this operation does not allow any significant changes in wood
composition, the moisture content remaining stable.
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