Bobby Flay has his “throw downs”, but are you ready for a “punch
down”? No, not in the boxing ring, or on the local school yard, but in wineries
across the world.
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| A solid cap |
It is harvest time in the northern hemisphere, and in many
areas, the grapes have been picked and are nicely fermenting their way to
becoming wine. As a quick reminder, fermentation is the conversion of sugar to
alcohol. Through the metabolic activity of yeast, the sugars in the grapes are
converted to alcohol, and carbon dioxide (as well as a few other by-products,
including heat). White wines are typically fermented without their skins and
other solids, while red wines are fermented in contact with skins, stems, and
other solids.
The grapes are put through a crusher and then poured into
open fermentation tanks. Once fermentation begins, the skins in the tank of
fermenting red wine, are pushed upwards to the top of the must (juice), where
they form a thick layer that is known as the “cap”. Winemakers want to keep the
skins in contact with the must (this process is known as “maceration”). Maceration
is the winemaking process where the phenolic materials of the grape are leached
from the grape skins, seeds and stems into the must. Since 99% of all grape
juice (with the exceptions of teinturiers) is clear, the maceration process
extracts the color, flavor and tannins.
The cap needs to be mixed through the liquid each day, or
"punched down", which traditionally is done by stomping through the
cap. Is anyone having visions of Lucille Ball stomping grapes on the old “I
Love Lucy” show?
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| Angela at Turiya |
The main reason it is desirable to punch down the cap, is
that the wine will have a richer color, flavor, and astringency. But there are
other advantages…. During the early stages of fermentation, the physical act of
punching down, introduces oxygen into the yeast cells, and kick-starts the
fermentation process. It also helps distribute the yeast cells throughout the
must. Punching down also helps dissipate heat that naturally occurs during
fermentation. Red wines typically ferment between 60F and 70F, left alone, the
cap can reach temperatures exceeding 80F, which can spoil the wine, and providing
an environment that is beneficial to harmful bacteria. If the cap dries out, a
bacterial invasion is more likely. One example is the vinegar bacteria, which
converts alcohol into acetic acid. This is called “acetification” and will
spoil the wine, unless of course, the winemaker is trying to make vinegar.
There are two main ways to deal with the cap: punch-downs and
pump-overs, but modern technology has added several other techniques.
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| Brandon at Dragonette Cellars |
“Pigeage” (pronounced peej-AHJE) is a French winemaking term
for the traditional stomping of grapes in open fermentation tanks. Pigeage is
typically translated into English as “punching down”. Punching down is when the
cap is manually or mechanically pushed back into the juice from the top
(obviously an open container is needed). Feet, a punch down tool, paddle or a
hydraulic piston can be used to punch down. The most common punch down tool is
something like a long handled potato masher. This is both gentle and labor
intensive. It is performed at regular intervals during fermentation, and
depending on the amount of maceration the winemaker requires, can be done
numerous times during the day. The more aggressive the winemaker is, with
breaking up the cap, the more a wine will be extracted, dark and tannic. The
goal should be to break up the cap and work out all the lumps. When finished,
the surface of the wine should be smooth and moist throughout.
Historically, pigeage involved placing a wooden beam across
the lip of the tank and a worker with the punch down tool, using the beam to
step on for balance. Remember that CO2 rises, so the workers could easily be
overwhelmed by the CO2 fumes. There have been many reported cases of workers
passing out, and falling into the fermentation vats, drowning on the fermenting
wine. Nowadays, these vats are smaller fermentation bins, where accidents are
less likely to happen.
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| Remontage - photo courtesy of Madroña Vineyards |
A second approach to maceration is “remontage” which is
typically translated into English as “pumping over”. This technique is just as
it sounds, and involves pumping the juice from below the floating skins over
the cap. This doesn’t necessarily break up the cap, but does keep it submerged.
This technique is used for a wide range of wines and is especially common for
large batches that would be too difficult to punch down. Generally, remontage
is done with a hose that is connected to a spout at the bottom of the tank and
pushes wine through a pump and into a second hose that sprays the wine onto the
cap. This method does allow more oxygen to mix with the wine, ultimately influencing
the final wine product. If a wine is over-sulfured, some aeration would be desirable,
as it would help eliminate the off-odors.
Another, less common, method of maceration is the
"pneumatage process", in which compressed air or gas is injected into
the must. The bubbles created during the pneumatage process uses gravity and
the weight of the juice to circulate the wine juice with the cap of skins and
grape solids allowing for greater extraction of aroma, coloring agents and tannins
to diffuse into the juice. Additionally, tanks with built-in grates, that keep
the cap submerged in the juice, and rotary fermenters that turn constantly
during fermentation, are in use.
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| Active fermentation and punch down |
The newest method is known as “Rack & Return” This
method is uncommon, as it requires the use of two tanks. In this case, half of
the wine in a tank is moved to another tank and then returned to the original
tank, at a high velocity, using a pump at full speed, causing the cap to break
up.
In general, maceration takes about 2-3 weeks. At some point
the cap will stop forming, and the solids in the wine will start to sink, instead
of float. This happens because fermentation is slowing down and there are less
CO2 bubbles to push the solids to the top. Depending on the style the winemaker
intends to make, there is a balance. The winemaker wants to extract as much
potential from the solid materials in the wine as possible, but if he/she
extracts for too long, the wine can become bitter, because it begins to extract
tannins from the seeds, and not just the skins. Then again, if he/she extracts
for too little time, the wine may not be as complex as it could be, generally
producing a more fruit-forward, than complex, wine.
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| Pressing |
When the winemaker has determined the end of maceration, the
wine needs to be separated from the skins and seeds in the tank. The first step
in this process is to drain the wine from the fermentation vessel. This is
known as the “free run” wine, and is generally considered to be the finest
portion of the finished wine. The remaining juice and solids will be gently
pressed, and is known as “pressed wine”.
As you can see, there is a lot that goes on before the wine
ever makes it into the oak barrels, and begins its’ aging process (but not all
see oak, or aging), and it is all going on right now. The smell of fermenting
wine is one of the wonderful experiences of visiting wineries this time of year…and
I highly recommend it!
