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Ageing and maturation
in barrels and barriques
'Excuse me, is this a barrique-aged wine?'
This question is heard more and more frequently, as if it was the latest thing
or as if wines aged in barriques were necessarily a step forward. One thing must
be said: for thousands of years wine and wood have been associated. In fact in
the past wood was the only container for wine. After the war steel containers,
which are much more practical, but also more passive in terms of their relationship
with the wine, temporarily replaced barrels. Now the trend towards ever greater
complexity has seen wooden barrels reintroduced into the cellar.
Properties
of wood
Certain wines, from high quality grapes and particular varieties,
derive elements which give them greater structure and ageing qualities from their
time in contact with wood. But a wine which has been aged in wood also acquires
particular aromas from the wood. These
are most agreeable if well judged, but if barrels are over-used the aromas can
be unpleasant; these excesses carry over into the bottle, where wood aromas overpower
the original bouquet of the wine. Not only the type of wood, but also the cut,
seasoning, drying and even washing have an influence on the aromas which the barrique
will impart to the wine.
Large barrel or small barrel?
The
'legendary' barrique is a small barrel with a capacity of 225 litres. According
to French tradition they were usually made of oak from the Allier, Limousin, Tronçais,
Nevers, Vosges and the Massif Central and, more recently, from the Rocky Mountains
and also with wood from Russia. Compared with a large barrel, in the barrique
more of the surface area of the wine is in contact with the wood, which means
that there is a greater exchange of substances with the wood. The physical and
chemical ratio between a big barrel and a small one is around 3 to 1. This means
that three years are required in a large barrel to give the same bouquet as one
year in a barrique. This does not mean, however, that small barrels should be
preferred to big ones. It is up to the knowledge of the cellarman, given the grapes
used and what they are for, to decide the 'dose' of wood and choose the size,
type and time required for ageing.
Type of wood
There are
innumerable variables involved in barrel production which lead to differences,
sometimes quite marked, in the aromas the wood will give the wine, especially
in the case of small barrels in which, as mentioned above, there is more contact
with the wine. The first factor is the area the wood is from: the land where the
woods used for the barrel grow plays a fundamental role in deciding the aromas
which a wine can acquire from contact with the wood.
In lighter, damper soils (in the Limousin, for example) the
wood is more porous, with more aggressive tannins so it is more
suitable for brandy. The opposite is the case in more lime-rich
terrain (in the Allier, but also in the Tronçais and
the Vosges); the wood will be milder and less porous. The first
stage is choosing the wood. Human experience is crucial; the
best quality wood must be selected, the straightest trunks and
those with less branches. The trunk is cut to obtain the strips
of wood for the staves. The best technique is to split the wood.
Compared with cutting this has the advantage of preserving and
respecting the fibres, keeping them intact. The staves must
then be seasoned. When the wood is cut its moisture level is
about 70%, rendering it impossible to make barrels which will
have a good seal after assembly, as the wood would shrink a
lot. The wood is dried in the open air or in special kilns,
which makes a difference of 3-4 years. Kiln-drying can give
the required moisture level in a short time, but care is required;
if the wood loses its water content quickly the tissues and
fibres shrink fast which could cause cracking and splitting.
Natural drying occurs by simply leaving the
strips of wood stacked in a large area in the open air. The producers work on
the rule of thumb of a minimum of one year for each centimetre of thickness of
the wood. This means two or three years or more in the case of barriques. Natural
seasoning not only gives a normal drying process, it also imbues the wood with
volatile compounds which are highly aromatic, especially vanillin (to which the
classic aroma of vanilla is attributed), something which does not happen with
kiln-drying.
Shaping and toasting
Once the staves have been
dried they are trimmed to the same size and shaped by bending the ends so as to
have the widest part in the centre where the barrel is widest. The staves are
then joined with the first hoop to form an open conical shape.
The bending
of the staves to complete the barrel is done over heat, which is needed to make
the staves more pliable. Toasting - exposure of barrels to fire - is, perhaps,
the stage which produces the main aromatic differences from barrel to barrel.
Light toasting involves around five minutes exposure to the fire, medium toasting
ten minutes and heavy toasting around fifteen to twenty minutes. It is this operation
which will increase the toasted aromas in the wine - smoke, coffee, tobacco etc.
- that distinguish important wines.
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