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Choosing Whether to Press or Macerate White Grapes

05/09/2012

The timing of filling the press depends on the technique of processing the fruit you decided to use:  

  • Whole clusters: Fill the press immediately, add SO2 to the juice as it gets released during the pressing cycle.
     
  • Crush with no cold soaking: Fill the press as soon as SO2 has been mixed into the must post crushing/de-stemming.
     
  • Crush with cold-soaking: Add SO2 after the crush.  When the soaking period is over, we fill the press.  

 
Soaking on the skins (A.K.A.: "Cold Soaking"): Wait to Fill the Press

If you have chosen to de-stem and crush (remember to add SO2), you have a choice of how soon to press. You can either start filling the press immediately or you can choose to allow the skins to soak in the juice for a period of time before separating them. The longer the skin contact, the more varietal characteristics will be infused into the juice. This makes for a bolder, richer wine. Enzymes can be added to the must to help with extracting desirable compounds from the skins (see below). However, there is a caveat: the longer you soak on the skins, the greater the phenolics (tannin), protein and potassium levels will be in the final juice! This is important because, depending on the grape varietal and the amount of time the skins are allowed to soak for, can cause a greater shift in the treatments needed to stabilize the wine when it is time to bottle. It is possible to overdo the soak and wind up with “too much of a good thing.” We recommend starting in the 4-8 hour range when trying cold-soaking for the first  time. This allows you to get a good portion of the benefits of the technique while limiting the potential negative side-effects on future stability (more on this later).
 
If you are going to initiate skin contact here are some key points to keep in mind:  

  • Soaking times generally vary from 2-16* hours, with the 4-8 hours range being a good place to start.
     
  • Yeast double every four hours at 68F (20C) and every 6-8 hours at 59F (15C). The SO2 we added at crush inhibits bacteria and most indigenous yeast. However, there are wild yeast strains that are SO2 tolerant. If present, they can become established in your must and potentially create off flavors and aromas. The way to control unwanted fermentation is by using both SO2 and temperature:
  1. As long as you are adding your yeast within 4 hours of crushing any wild yeast that happens to be SO2 tolerant will not have enough time to take hold and harm your must.        
     
  2. If you will be soaking for more than 4 hours it is important to be able to keep the temperature of the must at 55F or below to avoid contamination problems. Any higher and you could get a spontaneous fermentation starting before you have a chance to inoculate!  This is why this process is referred to as a "cold soak".  
     
  3. In summary: If you cannot keep the must below 55F, then your options are to only soak for up to 4 hours or not do a cold soak. (Tip: refrigerating the fruit before processing, frozen water/soda bottles (sanitized before going into the wine!) or even dry ice can help keep temps down for extended cold-soaking.)  
  • If there are signs of any mold or rot on the grapes, you will want to limit the skin contact, not extend it! Grapes that are not perfect are not to be used for cold soaking.   
     
  • Taste the fruit: unripe fruit that tastes herbaceous will only magnify this flaw in the must when cold-soaked. If the fruit is not fully ripe, do not cold-soak. 
     
  • The SO2 you added at the crusher is your friend, but it is only temporary. Using a blanket of inert gas (Argon, or CO2) will help avoid oxidative problems during the cold soak period. The SO2 and the inert gas should be thought of as internal and external protection respectively and work together as partners to protect the must from oxidation during the cold soak period.  
     
  • Lallzyme Cuvee Blanc (AD353) is a specialized enzyme that was designed to help release a greater amount of desirable aromatics from the skins during cold-soaking. To use: Cuvee Blanc is simply mixed with a small amount of water then added to the must during the crushing-destemming.   

Note: make sure that your SO2 addition has been mixed into the must before adding the enzyme as high levels of SO2 could interfere with the enzymes ability to do its job!

  • Tannin Galalcool (AD150) can also be added to the must at the crusher to give oxidative protection during a cold soak.

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