Lately, due to the popularity and character of a great find, the Stonestreet Alexander Mountain Estate Cabernet Sauvignon 2006, I have spoken with a number of customers expressing concerns about residue and crystals that they have found on their corks and in their glasses. (See the picture of the cork above.) Appearance of residue is generally not considered a flaw, but rather an indication of a winemaker’s choices in production. Discussions about deposits in wine seem to be a hot topic in my world right now. So this is probably a great time to impart a little information about fining, filtering and cold stabilization of wine.
The article below was written by Jordan Ross, a writer an viticultural academic who studied at UC Davis and who has worked extensively in the wine business. Jordan does a great job of explaining the ins and outs of fining and filtration and references some very popular wines and winemakers as examples. If you are really curious, it will give you some ideas on wines to seek out so you can learn more by pulling a cork or two.
Fining and Filtration: The True Story
Jordan P. Ross
Connoisseurs, members of the wine trade and particularly wine critics, are under the increasingly popular notion that unfined and/or unfiltered wines, because they are manipulated less and therefore considered more authentic, are superior in quality.
Based on the experiences of some of the best winemakers in California, it can be concluded that wines of extraordinary quality are produced both with and without fining and filtration. Since these practices do not necessarily guarantee or compromise wine quality, the best way to evaluate a wine is by drinking it. Nonetheless, some producers trying to exploit the trend, attempt to boost sales by pandering to influential wine critics. But what the critics do not realize is that fining and filtration are indispensable to the winemaking craft and, used properly, can improve wine quality.
After a wine completes fermentation, yeast, bacteria and fragments of grape cells are in suspension which make the wine cloudy. During aging, the wine clarifies as gravity pulls these particles to the bottom of the oak barrel or stainless steel tank, producing a sediment called “lees.” When this natural settling is insufficient to achieve a clear wine, fining or filtration is necessary prior to bottling.
|FiningFining and filtration are both used for clarifying a wine as well as to “stabilize” a wine. A stable wine will not undergo undesirable changes resulting from extremes of storage conditions such as temperature. It is not enough for a bottled wine to be visually brilliant because certain particles present in excess (tannin, protein) can become insoluble during the first 2-3 years of bottle aging, making the wine cloudy and, over time, leaving a deposit. Fining, a practice as old as winemaking itself, specifically removes tannins and proteins, ensuring its future clarity.Common fining agents for white wines are milk, casein (the protein found in milk), and isinglass (from the air bladder of sturgeons). Bentonite is a special fining agent added to remove protein in white wines. Otherwise, if the wine reaches a temperature of 80-90 degrees F, the proteins may denature (same as heating an egg white), appearing as a haze in the bottled wine. Bentonite is natural clay, carrying a negative charge which binds with and removes proteins, which are positively charged. Winemakers add the absolute minimum amount of bentonite because it can strip aroma compounds attached to the proteins.Red wines do not present problems with protein instability because the excess tannins react with and precipitate the proteins during fermentation. Fining agents also are used to clarify a red wine to the point where only a light filtration or no filtration at all is needed prior to bottling. But their more common use in red wines is to remove tannins, which reduces harshness. Common fining agents for red wines are animal proteins such as egg whites, gelatin and milk, all of which are positively charged. The attraction resulting from these opposite charges causes these substances to precipitate. The wine is then racked to separate the clear wine from these fining lees.
Filtration, a technique used for clarification and microbiological stabilization was introduced to winemaking only 30-40 years ago. The advantage of filtration over fining is that it can clarify a young, cloudy wine faster and more efficiently than fining. It clarifies by removing particles in suspension that cause cloudiness. Filtration not only clarifies visually, but by removing suspended particles can, from a sensory standpoint, make the fruit characteristics of a wine clearer and more vivid. Since some of these particles are yeast and bacteria, filtration plays an important role in the “microbiological” stability of a wine by eliminating the risk that these microbes will ferment undetectable quantities of sugar (or other food sources) still present after bottling.Filtration works by forcing a cloudy wine through a filter bed consisting of tiny pores which trap impurities. The most common materials used are cellulose fibers which are packed together into a pad. As the wine passes through, the fibers trap particles due to their negative charge and sieve-like effect. How densely the fibers are packed together determines the pore size and whether the filtration is rough, medium or sterile. A sterile or membrane filter, the most extreme filtration, is composed of cellulose fibers compressed to create pores in the filter bed small enough to entrap yeast and the considerably smaller malolactic bacteria.
The Influence of Malolactic Fermentation
Chardonnays from Burgundy and California’s coastal regions (Carneros, Russian River, Santa Barbara) typically undergo complete MLF’s. These colder climates produce grapes with higher acid levels which withstand the acid-lowering effects of the MLF, and therefore benefit from the stylistic changes. Since all of the malic acid is consumed, these wines do not need to be filtered since the malolactic bacteria have nothing left to eat.
In California’s warmer growing regions (parts of Dry Creek, Alexander and Napa Valleys) where grapes are harvested with lower acidity levels, a full MLF will drop the acidity even more, resulting in flabby wines which deteriorate rapidly after bottling. The winemaker arrests the MLF by chilling the wine or adding sulfur, both of which inhibit the malolactic bacteria. A partial MLF gives some of the stylistic benefits but leaves malic acid behind. The malolactic bacteria present in the wine pose a risk because if they ferment the remaining malic acid in the bottled wine, the carbon dioxide produced will make the wine fizzy. Even the winemaker most ardently opposed to filtration must filter this wine to remove malolactic bacteria.
Producing an unfined or unfiltered wine at a small winery is considerably easier because the winemaker is overseeing, if not actually performing all steps in winemaking. One such step is racking which is the drawing off of the more or less clear wine from the lees. A Cabernet Sauvignon, for example, is racked four times per year with each successive racking yielding a clearer wine. As long as the racking is done properly, after two years of barrel aging the wine will be sufficiently clear to bottle without filtering. The reality of larger wineries is that instead of 50 barrels, there are l,000 barrels, requiring the winemaker to delegate the racking to several cellar workers making it impossible to have adequate control over this important step in clarification. The larger the production, the less flexibility the winemaker has. Each fining or filtration step removes some amount (difficult to quantify) of aroma from the wine but will presumably add a greater amount in terms of insurance against cloudiness, haze or sediment formation, or microbiological instability.
Pros and Cons
Don Van Staaveren, Winemaker at Artesa Winery in Carneros, made a Bordeaux-style Cabernet Sauvignon called “Cinq Cepages” while winemaker at Chateau St. Jean. Van Staaveren filters his Cabernet Sauvignon but has not fined a wine since l985. He says, “I am against fining. Although it pulls out tannins, preventing sediment formation, some of these tannins contribute to aging and mouthfeel and you want to hang on to as much of that as possible.”
To eliminate fining, he takes several precautions during fermentation to extract sufficient tannin while avoiding astringency. Van Staaveren explains, “We crush lightly, leaving more whole berries. Low speed pumpovers and gentle punch downs help us to avoid grinding the pomace. By incorporating air into these practices, we get the phenols to polymerize, softening the wine. I try to take care of the problems during fermentation that would require fining later on.” As to filtration, “there is enough extract and power in our Cabernet so I am not so concerned with what we may lose in filtration.”
In the early 90’s, Chateau St. Jean produced more than l00, 000 cases of a $9.99 Chardonnay. Van Staaveren cites the microbiological risks of not filtering such a wine, “If you do not filter a Chardonnay that contains some residual sugar and has not completed malolactic fermentation, you might as well play Russian Roulette. For our white wines in general, we use one quarter of the recommended bentonite. Our wines are not squeaky clean; they will throw a protein haze if accidentally heated.” Van Staaveren continues: “The more limited, and therefore exclusive the wine, the more flexibility the winemaker has. Unfined and/or unfiltered wines are bought by sophisticated clientele and for them, slightly turbid or opaque is OK.” Van Staaveren casts a weary eye toward the proliferation of claims in this area. “It has become fashionable to say ‘unfined’ or ‘unfiltered’. At some level it can generate case sales. There is a place for fining and filtration. They are tools; it is how you use them, how you apply the technology and how they fit your wine style.”
But, this extra year of aging caused Meyer to take precautions before bottling. “A lot of things can happen in 30 months,” he said. Meyer is referring to the growth of microbes such as acetobacter which converts alcohol to vinegar, lactobacillus which produces volatile acidity and Brettanomyces (“barnyard” aromas) all of which spoil a wine unless removed by sterile filtration. He adds, “Even a red wine through malolactic fermentation with no residual sugar – if you bottle without sterile filtering, I believe you’re sitting on a keg of dynamite.” Meyer added, “We have conducted experiments putting some wines through a sterile filtration and some not and have had difficulty telling the difference. No one knows how much character is actually removed by filtration. It is a myth that unfiltered wines are inherently better.”
Newton Vineyards in St. Helena has produced an unfiltered Chardonnay for many years. Former Winemaker John Kongsgaard, patterned this Chardonnay after the European example. He explains, “Many of the great white Burgundies are unfined and unfiltered. We are unlearning the local traditions in favor of the older traditions.” Newton does not fine or filter its wines and Kongsgaard cautions that there are prerequisites, “To practice these methods, the wine must be microbiologically stable, meaning all of the sugar and malic acid are gone. You never have zero sugar and zero malic acid, so it is a guess. Every practitioner has to have some minimum target level which varies from vintage to vintage and winery to winery. It is not an absolute number.”
Tom Rochioli, winemaker at Rochioli Vineyard occasionally filters but never fines his Pinot Noir. He comments, “Pinot Noir is different by nature. Our Pinot Noir has a very low level of tannin so fining is unnecessary. I’m lucky; our wines clarify easily as well. We usually have relatively low pH readings and that is important to ensure a healthy fermentation, minimize sulfur additions and combat negative microbial growth.”
Rochioli also produces terrific Sauvignon blanc from a vineyard planted in l959. He explains the challenges in producing an unfined or unfiltered Sauvignon blanc, “We must fine and filter Sauvignon blanc. The grape has higher levels of solids and proteins which impede settling requiring two finings with bentonite. Isinglass is also used to polish the wine prior to bottling. It is the only wine we sterile filter because I choose not to complete the malolactic fermentation.
Ridge Winemaker Paul Draper has been producing Zinfandel for over 25 years. He often fines but never filters his Zins, and asserts that, “Careful fining and filtration have been a part of fine winemaking for many years.” He says that there is nothing inherently wrong with these techniques. “We fine 60-70% of our Zinfandels. We do not fine for visual clarity but for flavor clarity because the flavors of the wine are muddied, not clear-cut. Low levels of egg whites can lift that veil and add further definition.”
Draper stresses the importance of the fermentation in fining decisions,“The difficulty or ease of tannin extraction is different each year. You have to get a feel for this as early as possible in the vintage so you can assess how best to ferment it. The key is to avoid over-extraction of tannins because there is no simple correction for over-extraction. Fining later on will never make the wine as good as if you had gotten the tannin balance right in the fermentor.”
Zinfandel presents an added challenge because it is harvested at high sugar levels. The subsequent higher levels of alcohol can kill off the yeast before they ferment
Kistler Vineyards’ Vice President Mark Bixler explains how the design of their
The use of fining, filtration and cold stabilization says more about the individual differences between wineries and winemakers than these processes reflect in wine quality. Factors such as economics, production size, vineyards and stability concerns