Filtering wine is a touchy subject for some. Unfiltered wines are very popular in the market right now and it’s almost obligatory to bottle your wine unfiltered if you’re choosing to market yourself as a small, boutique winery. The reason for this is that some believe that when you filter a wine you rob it of its uniqueness and its character: metaphorically castrating the liquid in the bottle. If you’ve read Kermit Lynch’s acclaimed novel “Adventures on the Wine Route” you have a good idea of how some of the winemaking and wine consuming population feel about it. For those who haven’t here is a short excerpt describing two identical wines, one filtered and one unfiltered from Domaine Vieux Télégraphe, one of Mr. Lynch’s more famous imports from Châteauneuf-du-Pape,
“The filtered smelled as clean as it looked, but what little nose it had seemed superficial compared to the unfiltered, and it gave an impression of fatigue, which is not illogical because filtration involves pumping, or pushing, the wine through a long series of cardboardlike plaques… The unfiltered had a deep healthy aroma. One might say its aroma had texture; it seemed dense and full of nuances of spice and fruit. It smelled as good as the wine fresh out of the foudre.”
In this scenario the wines were tasted blind by Mr. Lynch and the whole staff at Vieux Télégraphe and the unfiltered wine declared the unanimous winner. However, this book was published in 1988 and therefore the wines tasted years before the book was even published, begging the question, “What would the results be if this test were replicated using today’s technology?” This leads me to the point of this increasingly lengthy rant: The idea that one wine is superior to another only because one was filtered and one was not is a false notion created by one’s own mind.
This debate wasn’t much of a debate until very recently: only groups of winemakers, sommeliers or enthusiasts of opposite camps swearing that their idea was the correct one. A sensory test is easy enough to conduct; a winery just has to save some bottles of unfiltered wine each year to compare to those that receive the regular filtered treatment. Multiple replicates including both older and younger vintages would give the experiment more credibility. Well, this is exactly what the entire crew (and a few unsuspecting guests) did at Donelan Family Wines this year after harvest concluded.
(The set up that was used to conduct our Filtered vs. Unfiltered experiment and the written guidelines that were laid out for us)
Four replicates of the same wine were assembled in sets of three: one reference and two glasses each assigned a random number. The object was to guess which of the numbered glasses was the same as the reference. As an added hurdle, the wines were tasted in black glasses so no differences in particulate matter could sway decision-making. This test was repeated with five different wines from the Donelan lineup over a five-day period. With a choice between two wines your results must be significantly higher than 50% in order to show that there was a difference that could be smelled or tasted in the wine that led you to make your decision, otherwise it would be akin to flipping a coin. The results of the test showed that out of 60 replicates there were exactly 30 correct responses, I personally went 10/20. These results proved to the staff at Donelan Family Wines that they were making the correct decision to filter their wines as another means of protection against spoilage from threats like Brettanomyces.
This test, while educational, may not be the hard scientific proof that some people crave to come to a final conclusion. For that we go to the lab of David Block of the enology department at the University of California, Davis. His findings are much too complex to explain here, but there is a short video and Powerpoint of his presentation that I highly recommend watching. The long and short of it is that Block conducted a much more controlled, thorough and extensive study with many more replicates than we did at Donelan and came up with (and is continuing to come up with) some quantifiable data that shows the same results. He explains that those components in wine that are responsible for flavor, aroma, body, texture and so forth, are smaller than the 0.45 micron filters that are used in modern wineries today and that the only effect that filtration has on a wine is an increase in visual clarity and microbial stability.
I’m sure the argument will continue, but this definitely arms those pro-filtering winemakers with some solid scientific evidence to support their decisions to do so. I have nothing against unfiltered wines; I have had several that I thoroughly enjoyed and believe that the decision to filter or not is part of a winemaking philosophy that adds variety to the business that we are in. However, those that perpetually seek the truth must find it in themselves to adapt from time to time in order to better themselves and their products.