Melissa Sanborn
Because the industry usually demands them to be clear and brilliant, white wines undergo different stages of clarification in the winery. If you’re lucky, a wine will clarify on its own with time and a little racking. If not, there are a few options open to winemakers: filtration is one of those options. Along with clarification, filtration is used to remove unwanted microorganisms from wine, either it be yeast in a sweet wine or spoilage organisms.
In our opinion, filtration is the least fun of all winery activities, hands down. It can be stressful, frustrating, time consuming, and will more than likely test the strength of one’s marriage. If it goes smoothly, one can rejoice in the brilliant wine at the end. If it doesn’t, blown-out filters often fly across the winery without any particular target in sight.
We spent last Sunday filtering our 2009 Riesling, Pinot gris, and Late Harvest Riesling in order to clear the wines up before finishing them. Additionally, we needed to remove remaining yeast from therieslings , both sweet. These wines have been chilling since fermentation to force the yeast into dormancy. Sweet wines have residual sugar in them, and any remaining yeast will start to ferment the sugar if they are allowed to warm and wake up. By filtering out the yeast, we can now bring the wines up to temperature and finish processing them.
There are a few types of filtration systems out there. In our winery, we use primarily pad filtration and membrane filtration. Unless a contamination occurs, we only use membrane filtration to sterile filter wine when bottling. Membrane filters have smaller pore sizes and are used to filter out finer, usually microscopic particles. We pad filter some of our wines at different stages of processing, depending on the wine. Pads of different pore sizes can be used, depending on what you are trying to filter out. A ‘rough’ filter has larger pores and filters out larger particles (sediment, bugs, pruners). As pore sizes decrease, the filters become ‘finer’ and filter out smaller and smaller particles. We use a succession of pore sizes, from large to small, to gradually remove things from the wine.
Needless to say, our weekend filtering went smoothly, a large cry from our initial attempt a month earlier when we could push no more than 20 gallons through the filters. We are now one big step closer to getting our 2009 whites into the bottle and into your hands!
