To filter or not to filter

One of the last steps in winemaking is usually filtering. When I worked at Wiemer, we used either the superfine cross flow filter or a pad filter for the wines made in smaller quantities. In winemaking you have to make some small sacrifices throughout the process. Each time you move the wine you risk exposing it to air, and inevitably each time you move it you risk losing a bit of its character, whether it be aroma, color, or flavor. Filtering is one of those steps that some winemakers would consider optional. The reason for filtering is to rid the wine of any bacteria or yeast that might remain in the wine and to ensure a “clean” wine before bottling. At Wiemer, where we made wines that often had some residual sugar left in them, filtering was necessary to ensure the yeast was completely removed from the wine. If any yeast remained, it could feed off the sugar and start another fermentation in the bottle, which at the very least might make the wine sparkle a bit, but at the worst it might cause the bottle to burst from the excess carbon dioxide and pressure.

Newton Vineyard in Napa was founded on the principle of unfiltered wines. Dr. Su Hua Newton, the first Asian female winemaker, began making unfiltered Chardonnay in the late 70s and then added the red Bordeaux varietals – Merlot, Cabernet Sauvignon, Cabernet Franc, Petit Verdot and Malbec. Her husband, Peter Newton, had been the first to plant Merlot in Napa when he worked for Sterling Vineyards, and the Newtons were one of the first to plant Petit Verdot in Napa. Dr. Newton built a state of the art winery between 1977 and 1979, with gravity flow and 30 feet of underground tunnels in the hills of Spring Mountain. The Newton vineyards are the only ones on the southern side of Spring Mountain, whose steep slopes and volcanic soil contribute to small concentrated berries and softened tannins. The winemaking process involves hand picking only the ripe fruit, which means they skip over the unripe fruit and go back to it later, making multiple passes through the vineyard until all the fruit is picked. The various pickings are kept separate, vinified in oak barrels in separate, temperature-controlled rooms. Then, the wines undergo aggressive “battonage” every day for 6 months – this means that after the fermentation has been complete (after a couple weeks), a long baton is inserted into the barrel to agitate the lees (dead yeast cells) that have fallen to the bottom. This action contributes a certain flavor to the wine and is “naturally antibacterial,” helping to “clean” the wine so the impurities settle out to the bottom. It’s similar to the process of riddling for sparkling wine, where the lees from the second fermentation in the bottle are forced to the neck of the bottle by a partial turn each day for 3 weeks, acting like a squeegee along the inside of the bottle until they are eventually disgorged. After the 6-month battonage, the clean wine – 85% of the barrel - is pumped out (this part is not done by gravity) and the remaining 15% of wine and solids is discarded. That amounts to about 4 cases of wine lost from this process - a significant loss but one preferred to the potential loss of color and aroma from machine filtering. The wine is then bottled and labeled “unfiltered.”

Views from Newton Vineyard

So does unfiltered wine taste better? Can you tell the difference? Newton wine still looks clear and clean. I tasted 4 wines paired with small bites from the Domaine Chandon gardens in Napa and their onsite restaurant, Etoile (Newton Vineyard is now owned by LVMH, the parent company of Moet & Chandon).  The 2009 Unfiltered Chardonnay was creamy with butterscotch and crème brulee notes. It wasn’t overpowered by oak and it went deliciously well with a spoonful of English pea soup accompanied by dungeness crab and meyer lemon. The 2008 Unfiltered Merlot had bright red fruit, black pepper and other spices, nice acidity, and grippy tannins that would soften with a bit more age. It went fabulously with a bite of tea smoked duck. The 2009 Unfiltered Cabernet Sauvignon had great black fruit that almost tasted sweet and again nice acidity and tannin that would lend well to further aging. The last wine was their Bordeaux blend that they call “The Puzzle” because of the shape of the vineyard blocks that it is sourced from. The 2008 Puzzle is made of 42% Merlot, 36% Cab Sauv, 14% Cab Franc, 6% Petit Verdot, and 2% Malbec. It was silky, smooth and complex and went great with the heirloom beet salad.

The last bonus wine was a 2002 Unfiltered Merlot from a Magnum bottle, which holds the equivalent of 2 regular bottles and is a better format for aging wine because of the reduced exposure to oxygen. This wine was musky and floral with additional characteristics of beets and lead pencil. It had great balance and structure and was very smooth. After recently enjoying the Newton 1991 Unfiltered Merlot and now trying the current releases, it was awesome to taste a wine right in the middle.

Now back to the question, to filter or not to filter? I can’t say I would be able to tell the difference unless I had the same wine in filtered and unfiltered form side by side. Winemaking is a combination of art and science, and I tend to gravitate toward wines made with the least manipulation. And as a former winemaker, knowing how the wine is made makes me appreciate and enjoy it more.

Corkscrew trees and the garden atop the wine caves