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AWARD WINNING ORGANICALLY PRODUCED WINES |
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| Fermentation
Primer |
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Alchemy, the transformation
of one substance into another, is indeed
what yeast does, because these organisms
consume the natural sugars present in
grape juice and produce in their place
alcohol and carbon dioxide. In still wines,
the carbon dioxide produced during fermentation
is released; in sparkling wines, it is
retained to provide the bubbles we all
know and love.
Yeast is naturally present as an airborne
organism just about everywhere on earth.
(Some winemaking regions like Spain's
Jerez region depend on the indigenous
"wild" yeasts to lend a unique
character to their sherry.) In the right
conditions, any fruit, including wine
grapes, will spontaneously ferment without
added yeast. However, because these wild
yeast organisms are unpredictable, not
very vigorous and often accompanied by
less desirable bacterial companions which
may overpower them and spoil the product,
most winemakers rely on a cultured yeast.
Cultured yeast is, in a sense, a wild
yeast which has been selected for admission
to and graduation from a good school with
hordes of equally educated and clean-behind-the-ears
colleagues. It's not essentially different
from its wild cousin; in fact the "science"
of yeast cultivation is relatively new
and there has been very little development
of truly new strains. The key is that
a particular strain, with identifiable
and desirable characteristics, has been
identified, isolated, cleaned up and produced
in mass quantities. Think of it as the
Ivy League of single-celled organisms.
Some are best for beer, some for wine
and some for high-level management in
acidic, high-alcohol or sweet and sticky
environments.
Winemakers have 3 basic options
when it comes to fermentation:
- Eliminate all of the wild yeast and
other organisms in the juice by adding
sulfite or by pasteurization, and then
add in a selected yeast strain (there
are also "killer" yeast strains
available which will, in their tiny
bond-raider way, terminate their competitors);
- Let nature take its course and hope
for the best. Pray that your wild yeast
will be vigorous enough to commence
fermentation immediately so that sufficient
alcohol (anything between 1% and 5%)
will accumulate to deal with potentially
harmful bacteria and mold. If fermentation
doesn't start quickly, the entire batch
of juice can spoil in a day. This will
be a nervous, insomniac, fingernail-chewing
winemaker;
- Take the middle ground. We don't eliminate
the wild organisms, but we make sure
that the conditions are right for fermentation
to start quickly and vigorously. We
let the juice warm up, and expose it
to air so that it is well oxygenated
(no sulfite is added to protect the
juice from oxidation-we even let it
brown slightly). Then we inoculate the
juice with 2 different strains of cultured
yeast. We know that the cultured yeast
will control the fermentation process,
but there will still be some participation
from the wild organisms, which we hope
will add a bit of local colour and personality.
(This is the winemaking equivalent of
including a performance artist in a
Board of Directors stacked with MBAs.
It won't hurt, but it may help.)
- Our cultured yeast comes from Lallemand
Inc. of Montreal, a world leader in
their field. The 2 strains we've selected
are Wädenswil saccharomyces cerevisiae
HK-4, and good old EC1118, saccharomyces
bayanus. Both are highly vigorous strains,
capable of rapid, complete fermentation,
even in high-acid, high-alcohol environments
(these yeasts have enabled our Icewines,
for example, to reach 17% alcohol) and
we are pleased with the character they
impart to the wine during and after
fermentation. Although different strains
of yeast may not yield obvious differences
in the wine, the role of yeast in creating
a wine's character should not be ignored;
the juice from wine grapes bears very
little resemblance to the finished product.
Some tasters divide aroma into three
distinct components: the primary aroma
(from the grape), the secondary bouquet
(from the wine) and tertiary character
(from aging). All of these aspects benefit
from the character of the yeast during
and after fermentation.
- Once the juice has been inoculated with
yeast and fermentation begins, the winemaker
has another decision to make about temperature.
A controlled, extended, cool fermentation
will generally result in a fruity wine
in which the primary varietal aromas
dominate. A warm fermentation (in white
wines, something in the range or 20-22°C
and in reds ranging between 20-30°C)
is generally complete and rapid and
results in wines in which the secondary
or vinous character predominates. A
warmer fermentation (which is our usual
practice) can also provide better colour
extraction and stability, and is more
suited to a full-bodied wine style.
Our organic standards allow the use
of cultured yeast, but prohibit the
use of genetically modified yeast strains,
enzymes or synthetic yeast nutrients.
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