Thank you Nicholas Heileman and Simon Hucko for contributing to last week's discussion on Harvest Methods!
This week: Filtering
What are the benefits and drawbacks to filtering wine prior to bottling?
A big reason for filtering a wine is for appearance purposes. By removing sediment and solids in certain wines they will not look as cloudy or hazy. They will look cleaner and brighter. Also -- you will be removing the particles that would otherwise be in full view in the bottle and/or in the glass. However, by giving the wine a cleaner look you risk losing color and certain flavor components changing the desired characteristics of the final product.
Another reason is microbial stabilization, resulting in a more consistent product with less bottle variation.
I think Darla and Jeremy covered the benefits pretty well.
I'd like to add that filtration can negatively affect a wines texture and overall lifespan potential.
The drawback of filtration is there is a potential to strip aromatic and other flavor compounds that could diminish a wine or producer's sense of identity. As Jeremy stated, the desire for consistency and stabilization leads many producers to filter ensuring that any unwanted microbes are removed prior to bottling. Filtration, or lack of, is just another technique that a winemaker has at their disposal.
Concerning negative effects to color, flavor, texture, aromatics, and lifespan, there is a great debate on this issue. One thing to keep in mind, all filtration methods are not the same. Sterile filtration, membrane clarification, reverse osmosis, ultrafiltration, electrodialysis, and crossflow are all widely used. Even within each category, there are various options for equipment and level of filtration. Crossflow and a pretty wide membrane won't be nearly as hard on the wine as a tight sterile filtration. Some say that wines bounce back from even the most extreme filtration. Some say that a few will bounce back, a few won't. And a few extremists out there (making beautiful wines, sometimes) say that any level of filtration is going to harm the wine. Shocking that there would be disagreement in winemaking philosophy.
A couple of other bullet point reasons for filtration:Remove VAAdjust AlcoholAdjust AcidityAdjust concentration of solids to waterChange Structure