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Vinification of sparkling
wines
Sparkling wines
can be produced by two different methods: the classic
method (which until recently was also known as the Champagne method) which involves
a second fermentation in the bottle and the Charmat or Martinotti method where
the second fermentation takes place in a pressure
tank.
For both methods the first stage is to obtain a base wine, following
traditional vinification procedures for making white wine. Different grapes may
be used for production of sparkling wines: either those with white berries (such
as Chardonnay or Riesling) or dark-skinned grapes (such as Pinot Noir). The grapes
to be used for sparkling wines are usually harvested just before they are completely
ripe so they have the most fragrant aromas possible and good acidity
which will give the wine freshness.
In the classic method the base wine is
then bottled and will undergo a second fermentation in the bottle. In this stage
(known as 'tirage') sugar is added to the base wine, along with selected yeasts
and riddling agents. This mixture is known as 'liqueur de tirage'. Once they have
been filled the bottles are closed with a special stopper, a cylinder placed with
the opening facing down towards the wine (the 'bidule' or cartridge), over which
the better-known crown cork is applied. The bottles are then arranged horizontally
in racks for the so-called 'prise de mousse'. During this period the bottles are
shaken by hand at regular intervals so that the deposit accumulates in ever larger
granules. After around 40 days the 'prise de mousse' is complete which means that
the right pressure has been reached. The sparkling wine will have become dry again
and will contain more alcohol.
At the end of this period the bottles are moved onto special wooden bottle-racks,
trestles in the shape of a capital A, with holes to hold the bottles. These structures
are known as 'pupitres' and are used to bring the bottles from a horizontal position
at first to a vertical position head down, by means of the operation called 'remuage'
(riddling), which is also carried out by hand and is designed to bring the lees
(yeasts) gradually to the cork of the inverted bottle. The wine then remains in
contact with the yeasts for several months.
The next stage is disgorgement
('dégorgement'): the bottle next is immersed in a liquid solution cooled
to -25°C. After a few minutes the part immersed in the solution cools and forms
a cylinder of ice containing all the lees and detritus which have accumulated
against the cork of the bottle. The bottle is uncorked and the little cylinder
is expelled. Now the bottle has to be filled up to replace the liquid which has
been lost. This is done either with some of the base wine kept for the purpose
or with dosage ('liqueur d'expedition') which is a sugary syrup, the exact composition
of which is each producer's secret formula. In the first case, when base wine
is added, the sparkling wine is referred to as zero dosage ('pas dosé').
Now the proper champagne cork can be fitted, covered with its little metal cage
(muzzle). All these operations are performed over a fairly long period of time,
usually at least 24 months. The longer the sparkling wine lies on the lees the
more complexity it acquires.
Charmat or Martinotti?
With the
Charmat or Martinotti tank method (there is argument about exactly who invented
this method, which appears to have been invented by the Italian Martinotti and
perfected by the Frenchman Charmat) the base wine, with added sugar and selected
yeasts, is placed in stainless steel pressure tanks which are hermetically sealed
and can resist high pressures. After around 10-15 days the 'prise de mousse' has
taken place so yeast activity has to be stopped. This is done by bringing the
wine temperature from +14°C to -4°C. This causes the yeasts to die and fall to
the bottom. The sparkling wine is left for a period of between 6 and 9 months
(long Charmat) on the lees then filtered, cleaned and transferred to a second
tank from where it is bottled. Corking
and muzzling follow.
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