Filtration for Crystal Clear Wine?

OK, maybe not many people stay awake nights thinking about wine filtration, but this is often times an important part of the winemakers bag of tricks to produce wines that are clear and appealing as well as sterile and stable. We’re going to look at a couple of aspects of this technique and maybe revisit for a more in-depth look later on.

To start, let me say that not all wines are filtered. Some producers make a point of stating this on the wine label. What does this mean? This means that the wine is not filtered. DUH! It does not guarantee quality or a level of quality. It means what it says: This wine is not filtered. Period. There are some winemakers who believe that a wine should never be filtered as all of the particulate components of a wine add flavor; filtering a wine reduces overall flavor and complexity.

There is also fining-this is a process whereby, traditionally, some material is allowed to filter through the wine to remove certain particles and compounds that may cause a wine to cloud. Some of the most common fining materials are: bentonite,a type of clay from Wyoming; kaolin, another clay; silica and activated charcoal. These are inorganic agents.

Organic agents include albumin, casein, gelatin, and rarely, isinglas from fish bladders. These agents work largely by forming compounds with solids in the wine, called colloidal particles, and add weight to them so they settle to the bottom of the cask.

Much of this settling action happens if a young wine, fully fermented, is left to settle on its own time. But time is money and fining gets the wine hopping along its journey to your table faster than waiting for it to settle of its own accord.

Filtration can be performed almost anywhere along the wine making process: wine is often filtered after fermentation when the wine is racked, transferred from one barrel to another, to start the aging and settling process. This is a coarse type of filtration and removes only the largest of the wine solids.

Modern filtration is either depth filtration or surface (AKA absolute) filtration. Depth filtration has the wine pass through a reasonably thick filtering membrane or agent. Solids get trapped somewhere in the channels of the filter and do not pass go and do not collect $200. Bummer.

As the name suggests, absolute, or surface, filtration removes everything if the filter holes are small enough. These holes are on the surface of the filter and need to be removed when clogged. This type of filtration can have openings so small that even bacteria and yeasts are filtered, hence, absolute filtration.

There are myriad variations on filtering agents and filtering machines, so we can come back to this topic if you would like. Let me know.

So next time you hoist a goblet of vino, hold it up to the light and see just how beautifully clear this wonderful beverage is; and realize that it takes lots of skill and experience and love to produce this product.

A Trip to Napa

The last week in September I was lucky enough to enroll in a course, a wine course, at the Culinary Institute of America Rudd Center in Napa Valley. The Rudd Center is a portion of the facility located in the heart of the valley. While the main part of the entire facility, the old Christian Brothers Winery, is devoted to culinary study, there is a separate building on the property that is concerned with wine study. After all, wine and food were born together and make ideal study buddies.

The course, Great Wine Regions of Europe II, focused on the Loire, the Rhone, South of France, Austria and Greece. It was presented in the state of the art amphitheater style classroom that can accommodate around 30 students. The presenter was an extremely knowledgeable Master Sommelier by the name of Bob Bath.

There was lots of information presented, about 24 wines per day tasted, and a good group of folks to hang with. With breakfast and lunch included, nobody starved.

What is important about this facility is that the same level of professional expertise is demanded for the wine studies as for the culinary and baking programs. The CIA offers a Wine Professional Certificate which requires a high level of knowledge of wines, service, wine business and food and wine pairing. To my knowledge, this is the first facility of its kind in the US. And when I asked my classmates why the CIA was chosen for study, certainly there are other wine education programs around, the same answer came through-quality of educational experience and knowledge of the instructors. The fact that the Rudd Center is located in the heart of Napa Valley and is drop dead gorgeous as well, certainly didn't hurt.

A long time ago I graduated from the CIA in Hyde Park, NY with a degree in Culinary Arts. For the longest time I wanted to get to the Rudd Center as my teaching and learning focus has drifted towards wines over the last few years. I finally made it and intend going back next spring if at all possible.

Good place. The photo is the front door to the Rudd Center.

Spain and Portugal

This past Sunday my tasting group and I were scheduled for wines of Spain and Portugal, light wines as the Brits say; table wines as we Americans say. One of the great aspects of the Wine and Spirits Education Trust program, is that, over a couple of years, I tasted wines that I never before knew existed. And as part of my Diploma study course, we taste wines from all over the world for Unit Three, Light Wines of the World.

Beyond the “regular” and familiar wines we ventured into: Rioja Reserva, Gran Reserva, a red from Navarra, a red Duero, a white from Rueda, made with the Verdelo grape which is responsible for the verdelho style of Madeira, but here fermented bone dry and crisp. There was a wine from the Duoro River Valley where port grapes are grown. But this was a scrumptious red table wine using the Tempranillo grape and the Touriga Franca, which is one of the top five quality grapes used in producing the exquisite fortified Ports I love.

A Vinho Verde delighted with its low alcohol, early fruity taste and its wonderful fizzzzzzz! And of course, there was a strwawberry/raspberry scented rose′ from garnacha grapes from Rioja.

What impressed the group was the fine quality of the wines-not a dog among them. In fact, most were exceptional. And when the price was factored in, they were all great values. We taste blind and do not reveal labels and prices until after all wines are tasted.

Malo WHAT?

Many secrets of art and nature are thought by the unlearned to be magical.
- Roger Bacon

No, this is not an incorrectly spelled Hawai’ian word. It is the first part of a somewhat mysterious process called MALO-LACTIC FERMENTATION. I say mysterious because it was not until the mid 1980s that the process was accurately identified, analyzed, and mastered. Though this process was present in winemaking since wine was first made, it was not known what “it” actually was. Malo-lactic fermentation, AKA secondary fermentation, is a process that occurs naturally and transforms the harsher malic acid (HOOC.CHOH.CH2.COOH., for you techno geeks), think sour green apples, into the softer lactic acid, (HOOC.CHOH.CH3), think dairy products. In so doing, a portion of the malic acid is converted into carbon dioxide, (CO2), and mostly goes away.

This process is beneficial in wines with high acidity, especially red wines from cooler growing areas; whites gain from this secondary fermentation as acid is quite noticeable, due in part to the fact that their acidity is high. However, in warmer climates, or in warm years in cooler growing areas, e.g. the Loire or the Mosel, if the Malo-lactic fermentation takes place, it may actually reduce the quality of the wine by throwing it out of balance. This is so because the acid in whites such as Chenin Blanc and Riesling, have their wonderful fruitiness balanced by high acidity. If acidity is reduced too much, the wines taste flat and uninteresting.

Try not to get confused here. Secondary fermentation relates to MALO-LACTIC FERMENTATION. If you are thinking about what happens with champagnes and sparkling wines, theirs is a SECOND FERMENTATION in the bottle. The wines are fermented dry and then put back in the bottle with the addition of yeast and sugar to create a second fermentation.

Chardonnay is a grape that does well with secondary fermentation. This determines the quality we often refer to as buttery in a wine that has undergone malo-lactic fermentation. (This chemical is known as DIACETYL.) If this aroma is in balance with the fruit and acid, it adds a wonderful note of aromatic and taste complexity. If overdone, it can become objectionable to the point where the “butteryness” overpowers the fruit of the wine.


How can a wine maker control this secondary fermentation? Historically, this secondary fermentation occurred in the spring time when cellar temperatures warmed and there was still sugar remaining in the “new wine.” In a modern winery, the wine maker can add lactic bacteria soon after fermentation starts. This timing allows the bacteria a comfortable temperature range; an acid level that it can tolerate; and an alcohol level with which the bacteria are comfortable. Those lactic bacteria are a picky group!

In some cases, a wine maker may rack off the wines after fermentation and place the juice in older wooden vats or casks that have a history of causing secondary fermentation. This does take longer and delays release of the wine. There may also be other bacteria that can contaminate and spoil the wine, so the wine maker must be careful in his or her choices for cask or barrel secondary fermentation.

If a malo-lactic fermentation takes place after a wine is bottled, it can create unpleasant tastes, will put bubbles in the wine , and will be an uncontrolled secondary fermentation. The winemaker will have no way of knowing if his wine is balanced and complex, or flabby and uninteresting.

I will give you another article on when a secondary fermentation is desired, even required, in certain traditional sparkling wines from France. But remember, these wines have a traditional secondary fermentation in the bottle because, decades ago when the wines were first produced, wine makers did not know what was happening. After time, this process of "unknowing" became tradition and then tradition became regulation.

Making Wine 2-Ageing

As I said in my first post on wine technology, there is an ongoing discussion of wine technology and tradition; and now a new factor is in play-so-called truth in labeling laws and regulations. As we continue in the series, many issues will be addressed; for now we’ll talk about how wine ages and techniques traditionelle and techniques moderne.

Texture, taste, color, and sediment deposits are factors in red wine ageing. Pigmented tannins, combinations of tannins and anthocyanins, provide mouthfeel, texture, and color in red wines. These components, called phenolics, are produced, or rather extracted or leeched, when the wine grapes are pressed. Early on the chemical reactions are based on these pheloics’ reactions with acid in the wine. As the wine ages, either in cask or bottle, these reactions are influenced by the presence of oxygen introduced into the wine when pressed, transferred, racked, or bottled. As time goes by, good title for a song, huh?, these different chemicals come together, agglomerate, and eventually get too heavy to stay in suspension in the wine. Hence, we have sediments, changes in color, and changes in taste. This why a fifteen year old fine Bordeaux needs decanting: the sediments are the harsher components of the wine that have dropped out, producing a wine with more integrated flavors, a harmonious texture, mouthfeel, and a slightly brown tinged color from the deep purple where the wine started when it was born.

The traditional method for ageing red wines is in the cask with added time in the bottle, sometimes for decades with potential for a great wine to achieve a century mark. Or more.

Based on the results of this ageing process, if like and kind results can be achieved in a fraction of the time, should modern techniques be used to achieve the desired result? Winemakers have available methods for filtering solids to remove bitter components from the wine. Oak flavor and nuance can be achieved by using oak staves, chips, and, some say, oak saw dust. By a process of micro-oxygenation, winemakers can hasten chemical processes that used to take months or years. This is where a wine is saturated with micron size molecules of oxygen, which filter through the wine to replicate the more traditional ageing in barrels.

Ageing can also be hastened by storage at higher temperatures than in traditional cellars. Again, cellaring was to hold wines at a constant temperature to allow the ageing process to occur. If you cellar your wines for five years, and I micro-oxygenate my wines and store at a higher temperature for one year, and we have almost the same result, is one process authentic and the other dishonest? Is one method old fashioned and the other making use of sound wine making technology?

If I use modern technology, should I be required to say this on my wine label? For example: “This wine was micro-oxygenated for six days, thirteen hours, seven minutes and four seconds before being aged in non-reactive vats with oak staves five cm thick, two meters long, and in a paddle array of five staves for three months, two days, five hours and six minutes?” You get the idea.

If aged traditionally, whatever that means, should producers be required to say like and kind describing in minute detail their processes and cellar environments?

These are not easy questions.