To Filter or Not To Filter…That is the Question!

OK, so maybe I’m taking some liberty with Shakespeare’s quote here, but it is a bit of an ongoing question in the winery. And with a couple of conversations I had yesterday with wine lovers, I thought a quick primer here was in order.

Getting to the core of the subject, the answer to the question above is, “We filter when the wine needs to be filtered!” There, wasn’t that super insightful and helpful?

So there are a few background aspects that are necessary to build up a basic knowledge about filtering.

  1. There is active and passive filtration of wine. Active filtration is the process of filtering a wine through a piece of equipment and passive filtration is time and gravity slowly clarifying a wine.
  2. There are multiple ways to “active” filter wine including pad filtrations, crossflow filtrations, and sterile membrane filtrations.
  3. All active filtrations, no matter how delicate the process, can impact the wine. The basic concept is that you are filtering something out of the wine (usually solids of some sort for clarity, but also yeast, malolactic cultures, etc.). Thus filtering can also pull out some aspects of fruit or complexity.
  4. The more active filtrations you do on a wine, the more chance you risk of stripping out characters in the wine.
  5. Filtering wine (especially sterile filtering at the bottling line) improves the stability of the wine in the bottle. (There’s less chance for refermentation if that is a concern.)
  6. Wines with residual sugar and/or an incomplete malolactic fermentation usually need to be actively filtered for stability reasons.
  7. The American wine consuming public likes clear wines (no hazy or cloudy characters)
  8. Even filtered wines may throw a sediment over time.

So now, let’s get back to the original answer. At Madroña, we filter wines when we think we need to filter wines. A lot of it has to do with the basic stability of the wine, but it also has to do with where the wine is being sold and who is going to be drinking it.

Ideally, I would never filter wine. That is the purest expression of what the wine has in terms of fruit and flavor. And generally, the aging in the barrels slowly clarifies the wine as gravity settles out the solids.

So you’ll find that our highest end wines, the Single Vineyard Collection, are unfiltered. This is done for several reasons.

  1. We want that purest expression of the vineyards in your glass.
  2. Most wine consumers paying $50+ for wine understand the unfiltered nature and can expect a hint of sediment or cloudiness (if it’s there for insuring a better quality of fruit).
  3. We can expect that consumers looking for unfiltered wines know that cellaring temperatures in their houses are very important.
  4. These wines are hand-sold at the tasting room by a knowledgeable staff in small quantities. This gives us a chance to educate, and the risk of issues in the wine is minimal.

But not all wines should be bottled unfiltered.

First and foremost, if a wines still has fermentable sugar or fermentable malic acid, we would not bottle it unfiltered. There is too much risk that the wine would referment in the bottle.

Secondly, we need to take into account how the wine is going to be sold. If we will be sending the wine to distributors or stores to sell where the temperatures can vary on the shelves, we would filter the wine. The fluctuating temperatures, especially warmer, could potentially provide a hospitable environment for yeast to start working in the wine once again. Ever have a sparkly wine with some cloudiness? That’s it!

Lastly, we need to consider the final consumer in all this. Not everyone knows all the ins and outs of wine and how to store it. We need to assume that someone is buying a bottle of Madroña off the store shelf, taking it home, storing it on their kitchen counter, and then still want it to be crystal clear when they serve it. Filtering is some insurance that they will have a pleasurable experience with our wine.

Now, two last items. One. If you remember my push to get a crossflow filter here at Madroña, it is an expensive piece of equipment we bought several years ago. I wanted this type of filter because I only have to filter a wine once (instead of multiple times with pad filtrations), and I find the wines “less beat-up” after filtering than with traditional filtrations. That has allowed me the luxury of filtering some of the high-end Cabernets and not losing any of the subtle characters in the wine.

The second item is that filtering wine will not prevent all sediment or turbidity from forming. The crystals on the cork (tartrates) can form over time by the tartaric acid “salting out” with temperature (generally cooler temperatures) and pressure changes. This is not a quality aspect as the wine would not have been cold stabilized in the winery (like all red wines!). And remember that you can save up these crystals and make cookies as it’s just cream of tartar!

Older reds too may have sediments due to aspect binding up in the wine (pigments with tartrates, etc.). Just be careful pulling the cork out as the sediment will have collected on the cork if the bottle is aging upside down.

And finally, instabilities with proteins in the wine such as heat and polysaccharides instabilities are not filterable if they haven’t already formed. But all of these instabilities (including the tartrates) are purely cosmetic and have nothing to do with the flavors of the wines. But that’s all for another blog!

So back to the basic question, “To filter or not to filter?” Well, I stand by, “We only filter when we need to filter, and even that we try to do sparingly!” Sound good?

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1 Response to To Filter or Not To Filter…That is the Question!

  1. Don Young says:

    What is the pore size of your crossflow filter?


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