Are you ready for a Punch Down?



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.

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?

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.

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.

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.

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.

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!

2 comments:

  1. Awesome blog. I enjoyed reading your articles. This is truly a great read for me. I have bookmarked it and I am looking forward to reading new articles. Keep up the good work! Blue Cheese

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