Luke Bohanan, Jeff Strekas, Roger Boulton, Hildegarde Heymann, and David E. Block Department of Viticulture and Enology University of California, Davis

Some winemakers believe that this process may strip subtle aromas and flavors from the finished wine. Many winemakers argue that this process is not only bad for the wine but actually unnecessary. Others find it is essential for clarity and stability. Some winemakers choose not to filter to avoid robbing the wine of its true character Clarity Microbial Stability Need a systematic study to examine the effects of filtration

 Investigate any transient changes in chemical composition during filtration  Investigate the extent of oxygen pickup during the filtration process  Evaluate the sensory and chemical impact of sterile cartridge filtration on red and white wines

Push with nitrogen (no pump) Filter right into bottling line Extended one run of PVDF to look at transient behavior 2007 Sonoma Valley Post ML, oak aging

Figure 2. Tannin as a function of bottle number. Bottles were sampled from the bottling line during the course of filtration with a PVDF membrane filter. Tannin was measured on a sample from each bottle using the Adams-Harbertson Assay.

Not much difference during filtration—Now let’s examine differences between the filtration treatments

Figure 5. Canonical Variate Analysis (CVA) of sensory properties of Cabernet Sauvignon after filtration. This CVA plot illustrates distinct difference over time with very little difference as a function of filtration treatment.

2009 Oakville Post ML, oak aging Push with nitrogen (no pump) Filter right into bottling line

 Very few differences noted during filtration for color and tannin-no transient is obvious  So far, no major differences observed between filtered and unfiltered wine  Still completing chemical studies on red wines  Completed Week 4 of sensory panel for White Wine.

 Chik Brenneman  Paul Green  Jennifer Heelan  Ron Runnebaum  Tarit Nimmanwudipong  Sensory Panelists  Rodger Pachelbel  Gallo Sonoma  Silverado Vineyards  American Vineyard Foundation