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Preemptive Fining of White Wine

05/09/2012

Fining: not just post-fermentation!  

Remember from chapter one that fining is the process of improving the wine by adding a specific product that will remove/lessen an unwanted element? Examples of this are egg white fining for removing excess tannins/astringency in red wines, or using Bentonite/gelatin to help a white wine clear out quickly post fermentation. However, fining is often done for more than aesthetic reasons in white winemaking, such as to reduce harshness, bitterness, and astringency along with limiting the potential for oxidative browning. In addition, fining is the only way to ensure heat stability (prevention of a potential protein haze) in a finished white wine.  

The various compounds responsible for harshness, bitterness, astringency, and haze (phenolics, tannins, proteins, etc) come largely from the seeds, skins, and pulp and are released into the juice as soon as we process the fruit. In fact, the more the fruit is handled during processing; the greater the quantity of these undesirable compounds that will be in our final juice. The important part to understand here is that these compounds are already here in our juice before the fermentation has even begun. Once the fermentation is underway all of these compounds start knitting themselves together, becoming evermore intertwined as the wine ages.  

All fining, by nature, alter the wine. A good way to think about this is to use an analogy of a house of cards. As the wine ages its various elements become increasingly interconnected through polymerization and a balance is struck in the overall balance of the parts. The longer we go the higher we build. However, when we remove one of these pieces by fining (for example to remove out a protein that could potentially cause a haze in the bottle) we will cause a shift in the structural balance of the wine and the wine will have to put itself back together again. Depending on how much of the compound that was removed, this can be a slight shift or the wine can change dramatically. This is why fining is a compromise and the goal should be to use the least amount needed to achieve the desired effect.  

Now we come to the practical part: the best time to fine for removing a large portion of undesirable elements is in the juice phase before the wine has started to put itself together! This pre-emptive fining does not create a loss of aromatic quality, and it gives a greater heat and oxidative stability to the wine from the very beginning.  
 
How fining works

The elements in wine that are subject to fining are usually positively or negatively charged. As with magnets where opposites attract and stick together, fining is the act of selectively removing a targeted element in the juice/wine. Tannins or proteins can be removed by using this principle. Add an oppositely charged element to the wine, and your targeted compound and the two smaller molecules interact to form a larger molecule that will stick together. Depending on the size of this newly created molecule, it will get pulled down by gravity and eventually settle out of the wine, or it will need to removed by filtration.  
 
Preemptive Fining is used in juice to help treat the following problems:

•  Heat Stability: All grapes contain protein. Depending on the grape varietal and the growing factors the amount of protein in our juice can be very little or quite a bit. In the beginning this protein is in a clear, solubulized form and it is relatively harmless. However, over time this protein can become unstable and flocculate out of solution (one way to think about this is to picture the way an egg white starts clear then turns opaque white when dropped into a boiling broth). The reactions are sped up when the wine is heated and this is referred to as a "heat stability" problem. The result is that a once clear wine will now suddenly see the appearance of wispy, white, fluffy clumps of material that look like a snow-globe when agitated. To avoid this from happening in finished wines, we need to remove this protein. In white wines* this is done by adding Bentonite clay. The clay is negatively charged and grabs the positively charged protein out of solution and settles it out. This is a very effective treatment, but there is a downside: depending on the type of Bentonite used the lees can be very fluffy and result in a loss of wine volume when the treated wine gets racked off of the deposit. Sodium based Bentonite is very fluffy and for that reason it is usually accompanied by a light gelatin (“Ichtyocolle” (FIN74)) or silica-gel dosage to help compact the final treatment lees and therefore reduces volume loss. Calcium based Bentonites are not quite as effective as Sodium based ones so you wind up using a bit more to get the job done. However, they have the benefit of being very compact in the final lees so there is little loss of wine post treatment. Calcium based Bentonites also benefit from a light gelatin or silica-gel dosage, not for compacting the lees during settling but for clearing out any fine particles that may be slow to settle once the main deposit has dropped.  

*Red wine must also contains protein at the early stages but the presence of seeds and skins during the fermentation creates a greater tannin presence in the finished wine. Since tannin is reactive with proteins the protein gets fined out as a natural by-product of red winemaking.

  • Oxidation/Browning: There are certain compounds (oxidative polyphenols) in must/wine that react with oxygen to create an undesirable brown color (the same way an apple turns brown after being cut open). When this happens, as an added insult to injury, a wine that was once fresh and lively becomes flat a dull. These polyphenols can be removed by fining with Casein, usually supplemented with PVPP. These are usually more  effective when used together (“Polylact” (FIN73)).

Note: If there is any rot in the grapes this will greatly increase the browning phenomenon. However this is from a highly reactive protein called "laccase" that is produced by the mold and is treated with Bentonite (not Casein or PVPP).

  • Bitterness/Astringency: These negative qualities come from tannins and other phenolics and are found in the seeds, pulp and skins of the grape (especially if the fruit is not completely ripe). Depending on the source these can be softened or removed by using Bentonite, Casein, PVPP, and or Gelatin.

How to choose the specific product(s) and determine the dosage rates for fining is determined by when you will be using them:
 

  • Juice stage: One of the beautiful things about preemptively fining in the juice stage is that the amount needed for each of the various fining agents is not as precisely regimented as it would be if treating the final wine. In fact, when treating the juice, we recommend following more of a "kitchen-sink" approach.  Great results can be had by using a combination of products to cover all of your bases! This is why we recommended preemptively fining our white wine juice with "Polylact" a combination of Casein, and PVPP, followed right after with a dosage of Bentonite:  

“Polylact” (FIN73) use at a rate of 2 g/gal. Mix with 10x its weight in cold water and let it soak for 2 hours. Then mix a little bit at a time into the juice while stirring. It is important to mix it into the wine slowly while stirring or pumping because if you pour it in too fast it will clump and just float on the surface of the wine.

“Albumex” Bentonite: (FIN51), use at a rate of 8 grams/gallon. Albumex has been prepared so that no swelling is needed before it is used. Just add it directly to the must right after adding the Polylact. Add a little bit at a time while stirring or pumping to ensure an even dosage on the entire juice volume.  

Important Note: Albumex is a Calcium-based Bentonite which, as explained earlier, means a larger dosage (8 g/gal) is needed compared to Sodium–based bentonites to be effective. However, if you are using a Sodium- Bentonite, then we recommend you use a dosage rate of 1 to 1.5 g/gal.

Once you have added the Polylact and Albumex, we recommend mixing the tank again around 1-2 hours after the initial dosage. This allows the fining to be more effective. The juice is racked once the deposit settles. 

  • Wine stage: Unlike the juice stage, when we get into fining in the wine stage we must be very careful and bench-trials are definitely recommended! (For complete information on bench trials see our Guide to Bench Trials)

 
A final word about preemptive fining of the juice before fermentation: it does require extra handling and you do lose some juice to the process. However, what you lose in volume you definitely gain in quality... This may not be the technique you use for all of your white wines, but if you have the ability to keep the must cold, can protect the juice from oxidation with inert gas, and can be thorough with your SO2, we highly recommend  giving it a try.

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