I am often asked about the differences between filtered and unfiltered wines, and which are better to drink. Although the debate over filtered versus unfiltered remains unresolved with little scientific research, there are questions to consider before making an informed decision, such as: 1) What is filtration?, 2) How does the process affect wine?, and 3) What are the benefits and drawbacks?
Throughout history, winemakers have used a method called “fining” to ensure clarity in their wines. Fining is the process of combining wine with a binding substance of a positive charge, like egg whites, gelatin, casein protein from milk, isinglass collagen from fish bladders, or bentonite clay, among others, in order to remove negatively charged molecules which cause haziness in wine. Within the past several decades, advancements in technology have elevated fining to a more intense level called filtration.
In winemaking, filtration is the mechanical and chemical process of using a medium to strain out yeast, bacteria, and other undesirable grape particles like sediment. The main objectives of filtration are visual appeal and microbial stability. The visual element is simple, removing tiny floating particles will allow for a more brilliant color and clarity in the wine. Stabilization is achieved after remaining yeast cells are removed, which prevents additional fermentation and unwanted flavor changes from occurring in the bottle, thus establishing uniformity for any given batch. There are multiple filtration methods, including membrane filtration which passes wine through micro-porous filters to eliminate yeast cells, depth filtration which uses agents like cellulose powder, diatomaceous earth, etc. to trap particulates, and a new pressurized method whereby wine is spun at high speeds discarding unwanted contaminants.
The advantages of filtering are evident. So what is the debate about? Since the time monks were making wine centuries ago, these filtration practices were not utilized. Some winemakers argue filtering is untraditional and removes elements that affect aroma and flavor, therefore reducing quality. The question then becomes, ‘Is there enough flavor in the particles being removed to affect the wine’s end result, and if so, is that loss in flavor significant enough to risk spoilage and financial losses?’ While there are limited studies performed on this topic, the findings to date show no conclusive evidence either way. The highly respectable Viticulture School at UC Davis found sediment’s flavor to be negligible, and it further found that particles containing sizeable flavor were physically smaller than the holes in the filter, therefore allowing the wine to both clarify and stabilize as well as maintain its zest. In fact, many experts have participated in blind tastings and have been unable to identify a filtered wine from an unfiltered wine.
If studies conclude filtration doesn’t negatively impact taste, why would a winemaker still choose not to filter? One reason is many consumers prefer the deeper color and heavier mouthfeel from an unfiltered wine. The decision to produce both filtered and unfiltered wines weighs mainly on the end-product the winemaker is trying to achieve. One could argue it is simply a clever business decision to cater to both filtered and unfiltered wine drinkers, yet many winemakers assert there is an effect on a grape varietal’s true character depending on the method employed. Pinot Noirs, for example, can have low pH readings and are said not to necessarily require filtration to avoid microbial growth. Other grapes, however, such as Sauvignon Blanc, typically have more solids that should be fined or filtered out. The same applies for Zinfandel, which is picked when the grape has a higher sugar concentration and may result in leftover sugar continuing to ferment and throw off a wine’s balance. Unfiltered wine is available in most wine shops; some popular brands include: Dehlinger, Newton, Paul Hobbs, Presidio, Saintsbury and Williams-Selyem.
Given there are successful vineyards worldwide making quality wines both with and without the use of filtration, it seems the more pertinent factor is the artistic style of the winery itself. Neither practice seems to assure or harm a wine’s ability to reach its potential. Other alcoholic beverages, such as sake, whiskey, and vodka, also have unfiltered alternatives. The bottom line is there are a number of methods to create a uniquely notable wine, and that evidence is more than scientifically obvious.
* In this issue we are reprinting one of Daniele’s earlier columns, originally published in August/September 2012.
Danielle’s “Adventures in Wine” have been very well received by our readership and we appreciate her contributions to SOMI Magazine.