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Pressing a Red Wine Fermentation

02/22/2012

At the end of the fermentation the wine will have extracted everything it needs from the seeds and skins. When this is completed, it is time to press. It is important to press in a timely fashion because a prolonged exposure to grape solids post-fermentation might cause reactions that could generate off-flavors and otherwise ruin the wine.  
 
Pressing involves straining the liquid off and then squeezing the remaining skins and seeds (called pommace) to get the remaining wine out, much in the same way you squeeze a sponge to release residual water. You can use anything from a nylon mesh bag (BAG24) into a food-grade bucket (FE345) for smaller batches, to an actual wine press that can be purchased or rented for the day (WE110-WE160).  
 
Presses can be broken down into two design types: traditional ratcheting basket presses; and newer style bladder presses:  
 

  • Traditional Basket Presses work by pressing the pommace from the top of the holding basket down by using a heavy, cast iron, ratcheting mechanism. Basket presses are affordable and time-tested, but there are a few drawbacks. During pressing they develop a pocket of juice in the center of the basket which needs to be broken up and repressed to get all of the wine out. In addition, the pressing forces required by basket presses are usually much higher than for bladder presses. As a result, it is very easy to get harsh and aggressive characteristics from over pressing the seeds and skins. Finally, basket presses are difficult to sanitize and heavy to move around.  
     
  • Bladder Presses work by expanding a bladder using household water pressure via a garden hose. Since the bladder is situated in the center of the press, the grapes are squeezed from the inside out in an even fashion, avoiding the formation of juice pockets. Bladder presses are quite gentle on the must and create a higher quality wine than basket presses. Furthermore, bladder presses don‟t require any physical effort to operate, a hose will do all of the work for you. Finally, Bladder presses are easy to sanitize and lightweight enough to move around easily. The only downside to bladder presses is that they do cost more than basket presses.  
     

*Note: If you do not already own a press and are lucky enough to live close to a winemaking supply/retail store like MoreWine!, you may be able to rent equipment. This is a great way to get the benefit of using a high quality machine on your wines without having to buy it up front. If you do decide at some point to go ahead and purchase your own press, (or Crusher/Detstemmer) you will know exactly which one is best for you.  
 
 
Pressing  
There are several ways to get the fermented grapes into the press. With small volumes, the most common method is to scoop them out of your fermenter with a small bucket and pour them into the press. For larger volumes, you can purchase a must pump (PMP200), which is a large diameter pump with a rubber impeller to pump the must into the press. A must pump is a serious investment, but if you find that your production has increased over the years, it will be worthlooking into at some point. Another method for transferring must to the press is with a Suction Tube (WE548) to remove the liquid wine from the fermenter with a pump first, making shoveling the skins into the press a much easier job.  
 
Free-Run and Press-Run:  
When you transfer the must into the press, a large portion of the liquid will run through the press before any pressure has been applied to the skins. This is called free-run. If kept isolated, it often makes a better wine than the portion that is squeezed out of the skins, referred to as press-run. The pressed portion is not as good as the free portion because the act of pressing, while yielding more wine, also extracts some of the harsher tannins from the skins and seeds. As a result, it is a good idea to press lightly and taste the run-off frequently in order to monitor the end point for each press. The end point will be different for every must. The major signal to stop is a “thin” taste from the wine along with an astringent quality. Some winemakers separate these two portions of the press and age them individually. This practice can be difficult due to the need for two different sets of containers. You are welcome to experiment with separating the two runs. However, our winemaking has shifted back to blending free run and carefully- monitored press run together, as there are certain flavors in the pressed wine that we really enjoy.  
 
 
Transferring Pressed Wine to a Storage Vessel  
The wine is collected beneath the press in a shallow container and then depending on the volume, poured (often using a food-grade bucket with a handle) or pumped into a temporary storage vessel. Common storage vessels are carboys (glass or plastic) or variable volume fermenters which are topped with airlocks. If using carboys, they should be filled almost to the top in order to minimize the surface area which could be exposed to any oxygen in the headspace. You will want to leave a space 1-1.5 inches below the stopper to allow for the potential expansion of the wine as a result of temperature changes. If you are using tanks and will not be able to fill to the top, make sure that you flush the headspace with a blanket of inert gas to protect the wine from exposure to oxygen during this period

 

Click here for our Guide to Inert Gas in Winemaking.  
 
For expanded information about transferring, see section our Guide to Transferring and Racking Wine.

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