Filtration’s Silent Revolution

There has been a revolution in wine technology and you have missed it. It was not televised.

You have missed it because, at the same time, people with loud voices, people with lots of Facebook friends, people with lots of Twitter followers, people with PR skills have been pimping all things natural in wine. And filtration seems a little un-natural.

Filtration is gross intervention, to put it bluntly. At a time when so-called “minimal interventionist philosophy winemaking” is de rigeur, those of us out the back filtering have kept quiet. But beware of winemakers touting philosophy. Time to speak up, because I believe wine anoraks and consumers are ready to acknowledge a few home truths about the wine we drink.

Firstly, when we (the global wine industry) are moving wine all around the world, it’s great to have some reassurance that things are not going to spoil. Screwcaps are also a part of that story, but also for those of us who hate Brettanomyces tainted wines and have lost time, love and money to this yeast, sterile bottling presents a terrific solution.

In the past, the problem has been how to get the wine sterile without ruining it in the process. Filtration has had a bad rap for some time now. I know why. Let me explain.

It’s a similar reason as for why many winemakers don’t like to pump wine. Because, when you look at it, a pump has a suction side and a delivery side. The suction side is under vacuum, and so any leaks, holes or loose moments and you might be sucking air through your wine. A pump is a great tool for grossly oxidizing your wines. And most filters rely on pumps.

As well as this, in the delivery vessel (tank, barrel, whatever) there is a big chance of splashing, turbulence and again, oxygen can have detrimental effects.

But why filtration has, in the past, been nasty and evil is also because conventional filters block, leaving the pump running, with the wine under suction at one end and massive turbulence and pressure on the other. Not a good scenario for the hand crafted, terroirdriven delights that recently left the small French oak casks after gentle ageing in cool cellars listening the Bach’s Piano Sonatas. So we have a situation where slapdash cellar hands were thrashing wines through earth and pads filters, and winemakers noticing that this hurts the wines, sometimes beyond recovery. On top of this, diatomaceous earth was commonly used and is a known carcinogenic dust. Nasty stuff indeed.

The response from purists – oftentimes successful – was unfiltered wines. Successful until something bad happens.

Then came the revolution, in two parts. In the 1970’s the usage of inert gases, in particular carbon dioxide, nitrogen, and argon, gave winemakers the tools to limit, reduce or even eliminate oxygen through sparging and gas blanketing during wine handling. Not very romantic, and in a world of storytelling, spin and terroir driven fantasy, these words are often just too science-geek to get past the marketing office.

The second phase of the revolution I first saw in 2000, when cross-flow filters first came onto the scene. Cross flow filters use new membrane technology originally developed for the cosmetics and pharmaceutical industries. By moving the wine across the membrane, not against the membrane, the little pores in the membrane do not block, and so there is no pressure build up, and the filter runs gently without blockage. In one pass only, we can take the previously unfiltrable Pinot noir from murky lees to limpid.

Now it’s arguable to say this, but I am convinced that our Shiraz smells and tastes better after filtration. Contentious, but let me explain. Firstly, lees bind up aromatics and themselves may present some slight sulphide aromas. Removing the lees, even the finest of hazes, the wines smell brighter. Also, removing solids – yeast, bacteria, grape matter and also crystalline precipitates – allows the palate to present its purest tannin and textural glory.

If that’s intervention, then so be it.

Dan Buckle, July 2011.

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