Wine Importer Neal Rosenthal on Filtration

By Evan Dawson, Finger Lakes Correspondent

After the recent discussion regarding the effects of filtration on wine, I contacted wine importer Neal Rosenthal for his thoughts.

Over the past three decades Rosenthal has been a leading voice calling for unfiltered wines. In his book Reflections of a Wine Merchant, Rosenthal writes often about how he routinely asked winemakers to stop filtering wines. He also wrote a brief defense of Brettanomyces, but he did not connect Brett and filtration in his book. I appreciate his response, and I learned a bit about the evolution of filtration. I'd love to hear from winemakers and industry professionals regarding the filtration techniques that Mr. Rosenthal discusses.

His comments are:

First, let me say that I am neither vigneron nor winemaker. And, I have never had the desire to delve in microscopic depth into the chemistry of wine. So, if I am an expert on this question, a label that I would reject by the way, it is only as a result of my 30+ years of experience buying and selling and drinking wine.

I have a preference for unfiltered wines. That being said, whether a wine is filtered or not is not the factor that determines its quality.  The most important elements in producing wine of quality is to have vines planted in the best places and to do fastidious work in the vineyards. The rest, I contend, is the easy part, although I am sure that those who consider themselves “winemakers” might object to that conclusion.

When I grew up in the wine trade in the mid-to-late 1970s, filtering was de rigueur and was done in a very aggressive manner. In my opinion, many wines had their growth stunted and their character shorn by the filtration process, then done via the filter plaque with tight fibers that truly stripped away important parts of the wine in exchange for clarity of color and security. Because of this, I strenuously objected to the filtering of the wines I was buying. This was particularly true in the case of wines that were aging for a considerable period of time prior to bottling because, in those circumstances, most of the deposit that might have accumulated was easily eliminated with a careful racking of the wine prior to the bottling. This, to me, was the safer and more sane way to treat wine rather than pumping a wine through a filter which, to my way of thinking, produced nothing of value. I never viewed filtration, in other words, as something done to improve the quality of wine. 

There have been dramatic changes in the way wines are handled now. The “kisselguhr” method appears to be less aggressive and, therefore, less harmful than the old filter plaque. Also, those who use the filter plaque now frequently resist using the most compact membrane. On the other hand, the process of filtering, no matter which method is used, forces the wine to undergo a process that I would argue is unnecessary. Why manipulate a wine to gain nothing. So, yes, I remain a devoted fan of unfiltered wines. 

That being said, I have participated in tastings of wines that I have purchased from my growers alongside the same wine that my grower had filtered and have come away on occasion preferring the filtered version. I think this occurred not because the filtering improved the wine but as a result of the fact that the wine bottled for us was drawn from a single barrel and the other cuvée was a blend of multiple barrels. As anyone knows who has been around wine cellars frequently enough, each barrel has its own special characteristics and each plays a role in developing the personality of the wine within. 

The bottom line is that good vineyard work and the harvesting of healthy, ripe grapes are the essential elements in producing top-flight wines and my goal is to protect those wines from anything that might change or diminish them. Filtering seems to me to be, in most instances, unnecessary and, perhaps worse, deleterious.

Regards,

Neal
Neal I. Rosenthal
Rosenthal Wine Merchant Ltd.

Comments

[Rowland]

agreed, with time and carefull racking you can get anything brilliantly clear. but im not a commerical producer under time/space/inventory constraints.

[Tom Mansell]

"And, I have never had the desire to delve in microscopic depth into the chemistry of wine."

While I don't discount the author's experience with wines, I have to say that I just have no patience for wine phenomena with no scientific evidence. Wine drinking and sensory perception in general are so highly influenced by psychology! Without a lot of data (and unfortunately there isn't much out there) on supposed adsorption of aroma, flavor, and mouthfeel compounds, I would have to favor the benefits of microbiological stability over any supposed "deleterious" effects.

Then again, people still buy the Vinturi and Clef du Vin thinking it will age their wine 10 years in 10 seconds, so maybe I'm in the minority.

There's a good piece about this topic in "Wines & Vines", found here http://www.winesandvines.com/template.cfm?section=columns_article&content=58981&columns_id=24

[Marco Montez]

For me filtration is a tool to avoid spoilage issues after the wine is bottled, not about clarity of the wine. Wines can be clear enough without the need for filtration.

Sure wines can be bottled unfiltered, but it can kill the winery’s reputation and business. Will people come back to buy my Chardonnay after a small refermentation in the bottle while on their kitchen counter for a few days? I do agree that often filtration adds nothing to the wine besides stability, but stability is no small thing in the world of winemaking. It’s like saying that skydiving is much more exciting without a parachute.

I try to avoid filtering my wines but this is not always possible. As Mr.Rosenthal admitted himself, unfiltered wines don’t always taste better than filtered ones, though he justified this with what to me feels like (with all due respect to him) a lame “excuse”.

It’s unfortunate that many in the wine world portrait a negative image of filtered wines without much understanding.

[Jim Silver]

Bright and stable is the way to go, on that there can be no question. The world has little patience for wine that referments on the kitchen counter as Marco points out. While Tom quite correctly points out that there is little scientifically to point to as regards the mouthfeel (etc.) he also points out "Wine drinking and sensory perception in general are so highly influenced by psychology!"

Please, please, let more of Neal Rosenthal's sort of pyschology find its way to the wine drinking public. I've never met Neal, but I've had hundreds of bottles of his imports, and he is a GIANT among men in his field.

Unfiltered wines from Mr. Rosenthal's producers (and the likes of producers represented by K. Lynch and R. Kacher) are sold to people like me, who seek an experience that is as close to the natural as possible. These wines are a more holistic, organic, and terrior-driven than their sterile opposites. It is an intimate experience really.

Now don't get me wrong - I do NOT confuse brettanomyces with complexity and I do allow for the spoilage of mishandled bottles of wine in this genre. But that is quite rare indeed. There is nothing wrong with filtered wine, only boring, sterile wines.

[David Falchek]

I developed a taste for unpasterurized dairy products in Afganistan -- they all taste so much better that what is commonly sold in the U.S. I can't see why every dairy just avoids pastuerization and filtration all together since we know those high-tech processes negatively impact taste. Sure, SOME people will get sick, SOME companies destroyed by lawsuits and boycotts, but the product is clearly better and I just can't enough of the pure, natural flavor of raw cow and goat milk.

[Evan Dawson]

David - Not sure if you're being facetious, but there are plenty of folks who also believe that pasteurization strips milk of its nutrients. Regardless, I look for the least pasteurized milk products available.

[Evan Dawson]

Marco - I don't mean to be rude, but your sky-diving analogy doesn't wash at all. Without a parachute, sky-diving is suicide. Deciding not to filter wine does not necessarily kill it.

While we're on the subject of analogies, I'll give it a shot. Filtering wine is like sending your kid to school with a security guard to deal with the bullies. No one is going to beat your child up, but they're not going to learn to fight. They'll always come home clean. Send your kid to school alone and he'll have to deal with the bullies head on. Sometimes he'll get his clock cleaned and his clothes ripped. Most of the time he'll learn to scrap and fight and come out stronger and with more character.

At least, I imagine that's what many folks who enjoy unfiltered wine believe. But no one can say that all unfiltered wines are dead wines.

I also took particular interest in Mr. Rosenthal's description of the various methods of filtering. It seems that modern methods are not nearly as intrusive, and if someone as skilled and knowledgeable as Peter Bell is comfortable with the process, it's hard to believe it's always going to harm the wine.

[Marco Montez]

Evan, you are right... my analogy was exaggerated. But most of what I wrote was in agreement of not filtering whenever the winemaker has a high degree of confidence that there will be no spoilage post bottling. But for people to write off filtered wines as inferior with no concrete and extensive tasting data to back this up... that's what I find unfortunate.

[Thomas Pellechia]

I trust Rosenthal's wine selections, so I have no problem with what he believes.

The excuse, however, for liking that filtered wine over the unfiltered, the one about the barrels, illustrates a weakness in his argument--and of course, it's the barrel's fault, not the palate or the psychology.

I've loved both filtered and unfiltered wine, but I've hated more of the latter than of the former. Could be my psychology at work, and it could be some scientific thingie--until scientifically proven, I vote for psychology!

I do know for a fact that filtered wine removes potential problems and unfiltered may not.

[Evan Dawson]

Marco - I think you and I are largely on the same page, to the extent that someone like me is even qualified to opine on such matters. That's why we'd all benefit from more analysis. There are wonderful winemakers who have produced stunning filtered wines and stunning unfiltered wines; there are so many other factors in play.

[Rowland]

... hmmmmm well it seems the only responsible thing to do is to keep tasting a lot of wines! time to hit the caves and do some blind tastings (with glasses that are not clear, so there is no cheating).

[Rémy]

What strikes me is that, in good part, the fans of filtration commenting on this page and during the previous comment debate are taking what I would call a remedial stance - i.e. you should filter because brett is going to take over.

Really?

I've certainly had a lot of unfiltered wines that showed not the least trace of brett. There are plenty of other factors at work - alcohol levels, overall ecosystem in the winery and vineyards, hygiene in the winery, etc. So that type of equation seems a little simplistic.

Of course, if a winemaker is dealing with specific problems - like brett - and that filtering remedies the problem, why not. But it shouldn't be taken as a wall-to-wall solution. In the same way that I wouldn't tell a winemaker who's solving a specific problem to not do it and sell defective wine, I don't see why I should tell a winemaker who makes delicious, balanced, solid, un-bretted wines to filter if he doesn't want to.

[Charles Massoud]

When I was younger it was easier to enjoy wine. We talked about its qualities, what we liked or did not like about it. There is still some of that that goes on amongst consumers. There is however a growing community of wine lovers who preach for one thing or another. Frequently it is driven by our quest for more knowledge about the topic. Yet a little knowledge can be dangerous.

Filtration is not an end in and of itself. It is a tool. And like most tools it can be used successfully and it can be misused.

There are wines that are safe to bottle unfiltered. These wines will typically be dry, will have all the malic acid depleted, a low pH and adequate amount of free sulfur. Even then they should better be stored below 60F.

There are wines that are not safe to bottle unfiltered, and will have either residual sugar or malic acid, a high pH, or active bacteria or yeasts.

Filtration can be made at several levels of "tightness". The coarser the filtration the less likely it will strip a wine permanently. A very tight filtration may indeed strip a wine. It is accepted, as was demonstrated at the Geneva Lab, that a filtration down to 1 micron will in fact produce a wine that is a biologically stable wine. At that same demonstration it was also established that such wines, that would appear stripped right out of the filter, do recover sufficiently that the audience was unable to find a difference in the filtered wine and the control after 6 months.

So to simply choose to drink nothing but "unfiltered" wines misses a lot of very good wines out there. And to accept no wine unless seen through a filter also leaves a lot of very good wines that did not need it in the first place. A competent winemaker will know whether a wine needs to be filtered or not.

For those who shop based on such parameters, the "unfiltered" mention by itself cannot mean anything as to the quality of the wine, without knowing the crucial details as to whether that wine should have been filtered or not. Also a filtered wine is not automatically a better wine and is not guaranteed not to spoil.

Finally, many winemakers will use the mention "unfiltered" as long as their wines have not gone through sterile filtration which starts at 0.45 micron. Since there is neither a standard for the term "unfiltered" nor an enforcement mechanism, it is a term that is mainly used to suggest to the consumer added qualities that are ill defined. It makes this largely a marketing device.

[Evan Dawson]

Charles -

No surprise to see such an excellent series of comments from you. Now, let me ask, based on your comment:

"The coarser the filtration the less likely it will strip a wine permanently"

And based on Peter Bell's contention that a filtered wine might lose some character only temporarily before "bouncing back"... Why does a wine lose a bit of character or flavor? How does it bounce back?

These are probably questions that can't be answered, but I find it fascinating.

Regarding the demonstrations at the Geneva lab, do you have a link to more info? I'd love to get more detail.

[Charles Massoud]

Evan,

Good questions.

The answers not so easy to explain but easier to experience.

The easy ones first: someone in Geneva should have a copy of the proceedings of a wine seminar organized perhaps eight years ago when Thomas Henick Klink was there. In there should be a review of an experiment produced by a graduate student whose name I do not remember but who ended up being a winemaker at Chateau Ste Michelle. He had taken a red wine and put some of it through a sterile filter and left some of it unfiltered as control. A few months later these were tasted side by side, blind, at the subject seminar. My recollection of my own tasting was that I did not detect a difference. And I recall the rest of the room could not conclusively pin down one or the other.
Later we replicated the same at our winery and came to the same conclusion.

As to why this happens, I am more tentative: during filtration, as during any wine movement, volatile elements, which are accepted as being behind most flavors, tend to be extracted. The same thing happens at bottling when a vacuum is extracted and we then call that bottle shock. But it is widely accepted that wine recovers from bottle shock. And if the same thing happens during filtration then wine recovers, as tasted, from filtration shock.

Another thing to consider is that wine is for ever changing, to the chagrin of those who believe that filtration makes a wine sterile and passive. And that is because the wine chemistry is unstable. If you remember any organic chemistry, you will recall that acid + alcohol = esther. That reaction is not stable and is reversible. There are different alcohols in wine, including ethanol, glycerol, and others in trace amounts. There are also many acids in wine including tartaric, malic, lactic and traces of succinic and citric and others. And they are not sitting there watching each other but reacting with one another.

A reversible alcohol acid reaction will go on producing different esthers. What is lost during bottling or fermentation will soon be replaced by these ongoing, reversible, yet very slow reactions.
These take place because the elements are cohabiting together, whether filtered or not. It is analogous to putting water on tissue paper, it will wet it naturally, just like an acid will react with an alcohol, naturally.

The question to now ask is what happens when you filter below 0.45 micron. That space is so small that you now remove components made of larger molecules such as polymerized tannin and polysaccharides. These cannot reform and then the wine is permanently stripped. This is primarily the reason why there are winemakers who will equate "unfiltered" with the absence of only this tight sterile filtration, as here you are really altering, usually negatively, the wine.

Again, a little knowledge is dangerous, and I may have gone further than I should have.

[Charles Massoud]

Correction:

In the third to last paragraph it should read: ..."What is lost during bottling or filtration...". Inadvertently I wrote fermentation when I meant filtration.

[Saint Vini]

I have found certain wines I myself made & bottled unfiltered to have a certain hit-or-miss chance of brett. Some are fine, others polluted by it. VA problems rarely show up to any great extent, and I can't comment as to any variation between filtered or unfiltered on that point.

Mr.Rosenthal starts to defeat his own argument with the statement "whether a wine is filtered or not is not the factor that determines its quality"...I wonder why he cares at this point. To go on that he doesn't have any experience making wine, and the "easy part" is all the work done in the cellar tells me he needs to get back into a cellar and see what it is he's objecting to. I think it sounds like his impression was formed some time ago, and needs to be updated by a quick "reality check" as to what's being done currently.
He may still arrive at the conclusion he holds presently, but at least he won't appear to be out of touch with current techniques and procedures. That he states filtration "no matter which method is used, forces the wine to undergo a process that I would argue is unnecessary" shows he is out of touch with the very reasons filtration is considered in the first place, and confirms his earlier statement that he has no practical production experience. It may seem rude, but I would say that from his letter it becomes clear that though he has a wealth of experience as a taster, importer, etc., it obviously takes more than that to make wine properly and understand the otherwise hidden consequences of rejecting a treatment outright.

There are many factors which might lead me towards filtering, and there are many types of filtration ("tightness of the filter media") which range from relatively "light" or porous filtration for larger particles to very "tight" or sterile filtration to remove yeasts and/or bacteria.

[Thomas Pellechia]

Charles,

You did everyone a service with your post--everyone who's listening.

As you allude to when you refer to a little knowledge, etc., in all too many cases and opinions, religion seeps in where reason belongs.

The more I discuss wine, the less I seem to think there are definitive answers to most questions. Sometimes, I wish everyone would take that attitude, if only to stop talking and instead just enjoy the glass in front of us.

Yesterday, I mentioned to Lenn that on the subject of purism, I am inconsistent. I admit to having religion on certain matters, like where the best Italian cheese should come from, and that does not include Wisconsin rip-offs. But then, if I am forced to taste cheeses side by side, blind, and I cannot tell the difference, what good is my religious purity on that subject?

The only thing one has left in that situation is a question regarding his/her purism, and we all know how everyone loves to be wrong ;)

[Rowland]

So just for clarification, just bombing the wine with a sulpher treatment just like before you add the yeast at the begining, that isnt enough to get a stable wine for bottling? (at least for the home wine maker?)

[Jeff]

How many non filtered wines are dosed with Velcorin...?

[Thomas Pellechia]

So just for clarification, just bombing the wine with a sulpher treatment just like before you add the yeast at the begining, that isnt enough to get a stable wine for bottling? (at least for the home wine maker?)

No.