The filter factor

Wines & Vines, June, 2004 by Larry Walker

Wine filtration, and to a lesser extent fining, remain subjects of controversy among winemakers. There is the school that argues filtration is always necessary for stability in the bottle. The other side argues that a carefully made wine, red wine in particular, which has gone through barrel aging, should not need filtration, either early or before bottling.

In Jancis Robinson's The Oxford Companion to Wine, the late professor Dinsmoor Webb of UC Davis wrote: "Filtration of fine wine is a controversial issue. While it may be necessary for ordinary commercial wines, too heavy a filtration can indeed rob a fine wine of some of its complexity and capacity to age." On the subject of fining, Webb wrote: "Most young wines, if left long enough under good conditions, would eventually reach the same state of clarity as fining can achieve within months."

There is also the perception among at least some consumers that an unfiltered or unfined wine is somehow superior or more "natural" than a wine that has been filtered. This attitude has been encouraged by wine marketers who put the message on the wine label, sometimes even the front label, that the wine has not been filtered.

Wines & Vines asked a number of winemakers around the country (via e-mail) about their approach to filtration. We asked the following questions:

1. Has your use of filtration in wine production changed in the past few years?

2. Please describe your present use of filtration. Does your approach vary with vintage? With variety?

3. Some believe that filtration can "strip" a wine of flavor elements. Would you care to comment on that?

4. Have you had any bad experiences with unfiltered wines?

5. Wineries sometimes state on the label that the wine in the bottle is unfiltered. Do you feel that wine consumers understand the process enough for that statement to be meaningful?

Not all responded to every question, but we did receive some thoughtful answers.

Dave Johnson, the winemaker at Stone Hill Winery in Missouri, said that his use of filtration had not changed, although he was looking into cross-flow filtration. He said that filtration does depend on variety. "In general, we try to keep filtration to a minimum by achieving maximum prefiltration clarity via fining. Almost all wines are, however, sterile filtered prior to bottling."

He does feel that filtration has some "stripping" effect on wine. "But this can be reduced by keeping filtration media to a minimum. The perceived negative impact of filtration seems also to be, at least partially, temporary."

Johnson has experienced problems with unfiltered wines. "In the past, a couple of unfiltered reds, which seemed fine at bottling, slowly developed ethyl phenol levels considered to be excessive, or Rhone-like, depending on one's point of view."

He expressed doubt that the word "unfiltered" on the label would have a "positive marketing impact in our market."

Patrick Campbell of Laurel Glen Winery in Sonoma County e-mailed: "We're a little less suspicious of it now, having seen over time the positive results of well-planned and executed filtration. We polish filter only. Of course, if a wine is problematic, a sterile filtration is called for. We haven't done one to date, but would not hesitate to do so if a wine has significant residual sugar."

As for stripping the wine of flavor elements, Campbell said, "Initially, a heavy-handed filtration can strip. I did a lot of work on this in the '80s with some pretty successful winemakers. We all came to the conclusion that while we saw no negative difference (and actually often found positive difference in favor of even sterile filtration) over time, we remained a bit suspicious. In short, filtration passes the scientific, rational, and organaleptic, if not the emotional and gut-feel tests."

While Campbell has not had any bad experiences with unfiltered wine of his own, he said he had tasted any number of wines that were bacterial, murky, petillant and gaseous that should have been filtered, and which were undrinkable.

Campbell said that he believes putting an unfiltered statement on the label isn't meaningful. "That is pure marketing hype." He added, "The real issue is that not all filtration is equal. A polish filtration is not harmful if done correctly--in fact, it's beneficial. Who wants to drink murky wine? A sterile filtration is better than the alternative--wine that is not stable in the bottle. What does filtration do? It takes out solids in varying degrees, depending on the fineness of the filter pads. Do solids add flavor to the wine? I doubt it, and I suspect that anyone who thinks about it would come to the same conclusion."

John Hawley (Hawley Wines, Sonoma) responded by e-mail: "My attitude about filtration has changed, but so has the amount of wine I make. At Clos du Bois I filtered almost everything. I guess I wanted to be sure that there wouldn't be any problems later. And we did not have any problems with the wines I bottled there. The one wine that I chose not to filter was the Pinot noir. And I did filter a portion which tested positive for Brettanomyces. When I started making wine for K-J in 1990, I continued to filter everything except the Pinot noir, until I was told to stop this unfiltered thing because it was 'too risky.'"