Both fining and filtration are treatments that can be done to further polish or finish the wine just before bottling. Fining works by introducing an agent to the wine that physically binds with a targeted element, most commonly tannins or proteins. Once the reaction finishes and the agglomeration precipitates out to the bottom of the vessel, the wine is racked to remove it from the sediment. Filtration works by passing the wine through a material that contains a series of very small holes (or “pores”) similar to a coffee filter. Liquid and particles small enough to fit through these holes are allowed to pass through; particles that are too large get held back and are effectively removed from the liquid. Depending on what is going on in our wines, we may decide to do one, both, or neither of these treatments. It all comes down to our personal winemaking philosophies and whether or not we feel the wine needs maintenance. Let's take a quick look at both fining and filtration before we move onto bottling.
A red wine is usually fined in order to soften a harsh or astringent character and/or to improve clarification. Fining agents should be used at the lowest possible dosage needed to achieve the desired effect. Over dosage creates the risk of loss of mouthfeel, color, aroma and/or flavor. Yet, due to the complexity of the chemical structures in wine, different fining agents will be more or less effective at achieving a desired result. We strongly recommend conducting a bench trial first to determine which product gives the results you are looking for. Then, once this has been decided, do a second trial to determine the ideal dosage rate that will give the desired results for the least amount of product used.
Subtractive fining treatments
Subtractive fining agents work by physically removing offending elements from the wine. (Addition by subtraction.)
Additive treatments (A.K.A.: “coating”)
The following treatments are considered to be “additive” because instead of removing the offending element, they work by coating or adding to the molecular structures that are responsible for creating the perception of harshness in the wine. While this may seem counterintuitive, “additive” treatments are often able to modify the aggressive/harsh character(s) you were trying to eliminate so that the need for further fining can be reduced or even unnecessary. Since the “coating” of tannins is an additive process, there is no danger of stripping anything out of the wine during the treatment. However, the one caveat to additive treatments is that if overdone, they can overpower subtle elements in the wine. Once again, bench trials and a conservative approach to your additions will help to avoid any problems.
Note: When Opti Red/Booster Rouge/Noblesse additions are overdone, they can create a candied sweetness that comes across as artificial/not from the wine that should be watched for during the bench trial.
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Filtration
There are two reasons to filter wine: aesthetics and microbial stability. On the aesthetic side, filtration can make a wine more polished both in the glass and in the mouth; often creating a rounding effect that softens the wine‟s edges. If your wine is sound with no flaws, then you can decide if you want to further shape your wine by filtering it. However, if you have residual sugar or Malic acid left in the wine, or there was a problem with
Acetobacter or Brettanomyces during the ageing/storage period, then filtration is no longer an artistic decision; it becomes the only way to guarantee microbial stability for the wine.
Pore sizes of filters are measured in microns. Typical winemaking sizes are 5, 3, 2, 1, and .45 micron media. The smaller the holes, the “tighter” the filter is said to be. Filtration's guarantee of microbial stability comes from the fact that the pore size of filters can be made smaller than the actual yeast and microbes themselves. As the wine passes through the filter the larger microbes become stuck and are removed from the wine. Note: 2-micron filters are used to remove yeast, and .45-microns are needed to remove bacteria.
Filters are rated as being “Nominal” or “Absolute”. A nominal filter will remove most particles that are equal or greater than the rated micron size. An absolute filter will remove all particles larger than the micron rating. Nominal filters are cheaper than absolute ones, and if you are only doing a general cleaning up of the wine, a nominal filter may be all you need. However, if you are filtering to remove either yeast or bacteria, you will need to rely on an absolute filter. Note that an absolute filter is only needed at the final filtration of the wine (usually during bottling, right before the filler to minimize exposing the sterile wine to contamination).
The effect that filtration has on wine becomes more pronounced as the micron-size becomes smaller. Filtration does remove certain elements from a wine; however, these are often elements that are worth losing. Filtration can stress a wine and cause it to temporarily “fall apart” right after the process. However, just as with “bottle shock”, filtered wines put themselves back together just fine over the following weeks.
Filtration set-ups are based on the two different forms of filtration media: cartridges and pads. Cartridges use housings, whereas pads require a “plate and frame” set-up. Both require a pump to move the wine (note that small lots can also be done without a pump using a keg and pressurized gas if you have this equipment). Cartridges are more expensive than pads because they are more intensive to produce, but they can be cleaned and stored for future use. Pads are cheap but they can only be used one time. Both pads and cartridges are tried and true, and choosing between the two technologies just comes down to personal working preferences: cartridges are clean to work with but they are more expensive and time intensive for maintenance. Pads are economical and somewhat messy, however when you‟re finished you just toss them.
Note: Only cartridges can provide .45 Absolute ratings. In other words you cannot achieve a sterile filtration using a plate and frame set-up with pads.
Filtration Summary
In the end, filtration is a very effective winemaking tool that can be used to gently polish a wine or to make sure it is microbiologically stable. However, the initial investment for the housing(s) or the plate and frame system make it a bit of an economic hurdle for the beginning winemaker. Fining requires no equipment and offers a cheap way to clarify a wine and have control over its tannin profile. Fining is the only way to achieve heat stability in a wine- as filtration does not remove the proteins responsible for heat instability. The only caveat is that fining is not very selective. You need to be careful about preserving the balance of all of the elements. Finally, keep in mind that the two actions are not mutually exclusive and a lightfining is often done to improve a wine's filterability.
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