In our cellar, fermentation
ends when all of the natural sugar has
been consumed by the yeast, leaving a
dry wine with very little or no residual
sweetness. (Other wineries may stop fermentation
earlier in order to retain sweetness.)
At this point, many of the yeast cells
are dead and the rest are only marginally
active. Along with any other solids left
in the juice, they fall to the bottom
of the fermentation tank and form a dense,
sludgy mass called lees which usually
represents 2 to 4% of the tank's contents.
The wine by now is quite clear, and will
be left in the same tank, in contact with
the lees for a period of 6 to 9 months,
a process called aging "sur lie."
Aging sur lie makes a lot of sense in
an organic wine cellar for a couple of
reasons. Firstly, enzymes within the yeast
cells are still active enough to continue
removing any oxygen dissolved in the wine,
and by doing so, they provide a sulfite-free
form of protection against oxidation.
(Sulfites are added to our wines only
at the very end of the winemaking process,
and we're not quite there yet.) Secondly,
as the yeast cells gradually break down,
they release a unique toasty flavour to
the wine, a very desirable characteristic
particularly in less aromatic white wines
like Chardonnay or Pinot Blanc. (In our
wines, this "sur lie" character
is often mistakenly attributed to oak
aging.) The flavour of wine lees is so
desirable, in fact, that it's added to
bread.
Some wineries will stir the lees during
this aging process. This is usually done
to accelerate the rate at which lees character
is imparted to the wine, and we haven't
found it necessary in our cellar.
When the wine is deemed ready, it will
be carefully "racked" or drained
off the lees sediment, and then someone
gets the really fun job of going into
the tank and cleaning the lees out. This
is something like having a sauna while
standing in a knee deep vat of khaki colored
sourdough starter. It's a very special
part of every cellar worker's initiation.
The lees is then composted and returned
to the Vine Yard.
All of us have probably encountered a
red or white wine which, when opened,
released a fine spritz of carbon dioxide.
(This is not always unpleasant, by the
way.) This spritziness, perhaps accompanied
by a bit of turbidity or sediment, is
a sign that the wine has probably gone
through a secondary fermentation in the
bottle. This secondary fermentation is
carried out, not by yeast cells, but by
Malolactic bacteria which consume malic
acid (naturally present in juice or finished
wine-think of it as the Granny Smith apple
of wine acids) and produce as by-products
lactic acid and carbon dioxide. This process
can be a problem in a finished wine (a
bit of spritziness is one thing; explosions
and cloudy wine are another) and that's
why many winemakers will wait for their
wines to complete Malolactic fermentation
(or prevent it altogether) before bottling.
Malolactic fermentation is deemed desirable
for 3 main reasons. It softens acidity
(often necessary in a cool climate region
such as ours), it makes the wine more
stable, and it adds a layer of complexity
to the wine's aromas and flavours (the
lactic acid can lend a buttery note).
The bacteria are fickle creatures, however,
and are active only within a fairly narrow
set of conditions. Waiting for them to
work can often add to the length of time
it takes for the wine to be "market
ready." The organism can be introduced
into the winemaking process by means of
inoculation but we have a resident population
in our cellar, and when conditions are
right (which seems to be the case for
most of our wines), they will set to work.
When Malolactic fermentation is complete
(and this can be during or after the primary
fermentation), the bacteria will fall
to the bottom of the tank with any other
residues.
Sur lie aging and Malolactic fermentation
are not unique to organic winemaking (in
fact, with the exception of trendy "blips"
in production methods, these practices
have generally been in use worldwide)
but the benefits of both processes are
part of what makes organic winemaking
possible. Without Malolactic fermentation,
for example, de-acidification would involve
the use of additives which are tightly
controlled by our organic standards. Without
sur lie aging, we would have to add sulfite
earlier in the winemaking process, with
the risk that levels at bottling would
exceed organic standards. All this, and
added complexity, too, thanks to a natural,
low-tech process of leaving well enough
alone. |
