Winemakers go to great lengths to produce wine that is pleasing (stimulating—in a good way) to the five senses—sight, smell and taste are the obvious ones, for sure, covering three of the four notions in “Swirl, Sniff, Sip, Spit”. Hearing is stimulated by the squeaky–pop of the cork (or the snap and scratch of the screw cap) and the gurgling–glug of liquid food flowing from bottle to glass (or the fizz of champagne and sparkling wine). Touch comes into play in several ways—the weight, shape and temperature of the glass in your hand, the gentle pressure of liquid enveloping your lips and washing over your tongue, the warmth expanding in your stomach and possibly other ways (especially if you are sharing the wine with someone). Try as they might, however, winemakers can’t always get everything done perfectly.
Sight, taste and touch can be impacted by unwelcome particulate matter in the wine, so winemakers often follow standard clarifying processes (such as filtering and fining) to remove the most noticeable solids. “Filtering” removes relatively larger particles and organisms that can reduce the stability of the wine. “Fining” eliminates “haze” in the wine by introducing substances—such as gelatin, egg white and bentonite (also used in kitty litter)—to absorb the insoluble material that filtering can’t remove and then separating the combined substances from the “fined” wine. While clarified wine is generally preferred, some winemakers use techniques that reduce the need for filtering or fining. Still others have gone the complete opposite direction and market their wine as “unfiltered” and/or “unfined” with varying degrees of haze to suggest that their wine is less processed and, therefore, more natural. Furthermore, excessive filtering and fining can strip the wine of desirable aroma, flavor and color characteristics and also some of its polyphenolic solids (like tannins), which can reduce the wine’s capacity to age well.
Another problem facing winemakers is that tartrate crystals (also known as “wine crystals” or “wine diamonds”) can appear as clear clusters in wine or on the end of the cork due to a chemical reaction in which potassium bitartrate (also known as potassium hydrogen tartrate and, in cooking, is known as cream of tartar) crystallizes during the fermentation of the grape juice. These crystals are mostly removed from the fermented juice during a process known as “cold stabilization” in which the temperature of the fermented juice is dropped to close to freezing for 1–2 weeks, which separates the crystals from the juice (the crystals stick to the sides of the tank). When the juice is removed from the tank, the tartrates are left behind—well, mostly. Although harmless, tartrate crystals can cause concern on the part of people who don’t understand what they are.
After winemakers have done what they can to produce an appealing bottle of wine, what can you do to enhance your wine–drinking experience? Most wines are meant to be consumed young. Yet, why do some wines taste better with age? In general, red wines that age well are higher in acidity and tannins, while white wines that age well are higher in acidity and had more contact with the grape skins during processing. The use of oak barrels in the pre-bottle ageing process also contributes to the ability of wine to age well. Why is this so?
Chemical reactions of polyphenolic compounds (which contribute to a wine’s taste, color and mouthfeel) continue to occur after the wine is bottled. Tannins are, perhaps, the most commonly known polyphenol found in wine and can contribute to the color, astringent taste and ageing capacity of wine. Winemakers do various things to influence the polyphenolic content of wine. The process of aging wine in oak barrels prior to bottling introduces polyphenols such as vanillin, which also adds a vanilla aroma to the wine. Conversely, as mentioned above, the fining process can reduce the tannin content of a wine.
Polyphenols have a higher acidity level than alcohol, so they act as antioxidants or preservatives which can help a wine age well. Yet, they break down over time. So, as red wine ages, the tannins soften in taste and the wine’s color tends to fade. Over time, polyphenols bind together and eventually become large enough to remain suspended in the wine as sediment. Although the aged wine may taste better, the resulting sediment, while harmless, can have an unpleasant taste and appearance. Naturally, people like to separate the wine from the sediment before serving the wine. This is done by decanting the wine.
A decanter is just a vessel to hold the wine poured from the wine bottle, although there is a continuing debate (some scientific and some not so) about the ideal decanter shape for particular types of wine (analogous to the discussions about using the wine glass shapes for particular types of wine). The formal decanting process (shown in the video below), which is slightly less intricate than the Japanese Tea Ceremony, involves careful handling of the bottle by cradling the bottle from cellar to pour and keeping the bottle at a fixed angle while pouring the wine in front of a candle or other light source in order to see the sediment so that you can avoid pouring any sediment into the decanter.
Some people take a less formal approach and just let the wine bottle sit upright for a several hours and then pour the wine into a decanter until they see sediment coming through.
Historically, in the days before more extensive filtering was performed, many wines needed to be decanted in order to separate the wine from the sediment. Today, however, sediment appears mostly in red wines that have been aged for awhile (typically, over 10 years), if it appears at all. So, why do people continue to decant wines that don’t have any visible sediment, particularly younger wines? The answer is that, technically, they aren’t really “decanting” the wine—they’re “aerating” it. Decanting traditionally means separating solids from a liquid—as in separating sediment from wine. When there is no sediment, you are simply pouring the wine from its bottle into a vessel that exposes the wine to oxygen while it rests for some time. This enables the oxidation process to take place much more quickly than it did when the wine was in its bottle. This oxidation process is really “aeration”, but people often call it “decanting” because they use a decanter and the process looks a lot like the more informal decanting process (the one done without the candle and the careful handling of the bottle), except there isn’t any sediment in the wine bottle. So, why do they do this and is there a better way to do it? Stay tuned for the answers next week.
(Decanter image courtesy of Creative Danes; Wine Crystal image coutesty of Bruce-p.)
February 11, 2009 at 6:00 pm
Thanks for clearing up a confusing topic. Especially the part about the wine crystals. I always wondered what those were.