The age-old
process of turning grapes into wine is a rigorous science with a bit
of magic thrown in. Here are the basic steps:
1.
Determine the Pick
Date: The first step in making wine is deciding when to pick
the grapes. In general, the
grape variety, combined with wine style, determines pick dates. Grape
ripeness is analyzed and judged. It's checked for sugar and acidity
levels, pH, colour, health, seed colour, aromas, and flavors.
But many other factors complicate the pick decision—particularly
weather. If it's too hot, grapes must be picked at night. If a long
period of rain is expected, it may be necessary to pick grapes before
optimum maturation. Early frosts and freezes can devastate an entire
vineyard.
2. Pick the Grapes: Once
the pick date is determined, containers are placed in the vineyard and picking of that grape variety begins.
Grapes are harvested as whole clusters, arriving at the crush
platform within hours of being picked—grape freshness is an important
aspect of producing an excellent wine.
Processing starts
immediately: grapes are visually checked, weighed, and then
processed.
It takes 2.4 pounds of grapes to make
one 750 ml (25.6 oz) bottle of wine.
3. De-stemming:
Fresh grapes are tipped from bins into the
de-stemmer. As the name suggests, this machine removes stems,
something it does with
minimal damage to the grapes. Stems are removed because they contain astringent, bitter, and tannic compounds
that can transfer to the juice (and ultimately, the wine) if left in contact too long.
On the other hand, some winemakers include stems for various effects;
for instance, green and unripened stems can add vegetal notes and
accentuate bitter tannins, which work well for certain wines.
What happens to the grapes after de-stemming depends on grape variety and style of wine to be
made.
4. Skin Contact:
White aromatic grape varieties receive up to 24 hours of skin contact.
This affects a greater release of phenolics and other compounds from
the skin of the grape, where most aromas
and flavors are stored. The skin of red wine varieties also
contains color pigments. Fermenting red wines in their skins releases the color
through a combination
of heat, alcohol, and natural acids.
Lucile Ball Pressing Grapes
5. Pressing:
All
grapes eventually pass through the press,
which extracts juice from the skins and seeds. In the case of non-aromatic varieties or
champagne-based wines, grapes are either destemmed first or placed
directly into the press. Aromatic varieties are pumped directly into the press after 24 hours of
skin contact. Fermented or fermenting red wine grapes are pumped (or dumped) from bins into the press.
The first juice to leave the press is classified as the free-run because it leaves without
force from mechanical pressure. This juice, the best part of the
pressing, is removed before the skins are pressed for a second time
(if at all). Second-pressed wine is of lesser quality than the first
pressing; oxidation occurs, and excessive tanins and harshness from
the skins is pressed into the juice. Second-pressed juice is avoided
by quality wine makers. Some winemakers blend it into lower-cost
wines.
6. Cold Settling:
White wine “must” (defined as
the unfermented or fermenting juice expressed from grapes) is cold-settled fresh from the press—in
other words, it's allowed to rest in a cool environment.
This process removes any grape skin particles that might have travelled with
the juice from the press. The result is a clean grape must ready for fermentation.
7. Fermentation:
The process of fermentation involves the metamorphosis of grape juice
to wine. Yeast creates the wine by metabolizing the grape sugars. It
digests and breaks down the sugars, which then form into carbon dioxide
and alcohol. Pure cultured yeasts are selected by the winemaker for their influences on
each individual grape variety. Some yeasts don't metabolize color and
are best suited for red wines. Other yeasts can tolerate the cold
and are great for cold cellars or white wines.
8. Racking:
When fermentation is complete, it's time for racking—the process by which yeast settled at the barrel's bottom is removed. More
accurately, the wine is removed from the yeast: that is, the wine is
pumped out of the barrel or tank, leaving the yeast behind. This
process may take place several times before the wine becomes clear.
Racking can take place a week or years after fermentation, depending
on the style of wine being made.
9. Fining:
Fining is the process in which unwanted natural substances
such as excess protein or tannins are removed. Such substances can cause wine to be cloudy or
develop an
unbalanced taste.
10. Cold Stabilization:
This process makes wine
"tartrate stable." Two main types of acid exist in wine, malic and
tartric. Both are abundant in grape juice, but become less soluble in
the presence of alcohol. The higher the alcohol, the less soluble the
acid. Potassium and calcium combine with the malic and tartric acids,
producing a white crystal which, if left uncontrolled, can form and
grow in the wine bottle instead of the tank. These tartaric
crystals are often referred to as wine diamonds or Weinstein ("wine
stone").
11. Filtering:
Filtering takes place in
many different ways. Some wines are ready to bottle right from racking
and aging. Others require diatomaceous earth (DE) filtering, pad
filtering, or micron filtering. DE filters are very gentle and work on
a sieve principle. Filter pads work on absorption. Micron filters,
which filter out extremely small particles, also work on the sieve
principle. Micron filters are sometimes called "police" filters because
they screen bacteria and yeast cells.
Bottling Wines
12. Bottling:
Filling the bottles, corking,
capsuling, labelling and palletizing are the last steps to finishing a
wine. Red wines often mature for years before being sold. White wines
tend to come to market earlier. Wine is made up of over a thousand
different minerals, vitamins, and other components; once in the
bottle, wine continues to mature and improve.
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