How does decanting red wine affect its taste? And why is it suggested for red wine, but not white?

by Andrew L. Waterhouse, a professor in the department of viticulture and enology at the University of California at Davis.

Scientific American 2004 vol:291 iss:5 pg:112 -112

The decanting of red wines has a long tradition in high quality wine service and can be done solely to add a special flourish at a meal. In decanting, the wine is simply poured into another container, usually one of clear glass or crystal. If sediment is expected, the use of a candle to assist in visualization adds even more to the ceremony. From the perspective of modifying the taste or appearance of a wine, the decision about whether or not to decant is based largely on two criteria, although the amount of published literature on the topic is very limited. (Terms that are not based on measurements, but are descriptive terms conventionally used by wine drinkers appear in quotations.)

Some young red wines–between three and 10 years older than the vintage date–can be harsh or astringent if consumed directly after opening the bottle. These are usually expensive wines that cost more than $20 in the U.S. market today and are produced with cellar aging in mind. Such wines have this harsh character because red wine is maintained in a relatively oxygen-free environment during aging in a bottle. Over time this environment results in a “closed” character for the beverages that is derived from the accumulation of particular aroma compounds. A wine’s aroma will change during the first 10 to 30 minutes the bottle is open. Decanting accelerates the “breathing” process, which increases the wine’s aromas from natural fruit and oak, by allowing a few volatile substances to evaporate. Decanting also apparently “softens” the taste of the tannins that cause harshness and astringency in young wines.

For optimal effect, a wide-bottomed decanter that gives maximum air exposure to the wine should be utilized. It is interesting to note, however, that chemists have not observed changes to these tannins after decanting. Less dramatic changes can be achieved by just uncorking a bottle 15 to 60 minutes prior to pouring. Keep in mind that many inexpensive to moderately-priced wines, as well as some more expensive wines, are intended for immediate consumption and will probably not improve with aging or decanting.

In older red wines the tannin reactions have proceeded long enough to reduce astringency. As a result, the taste is not as harsh but a sediment or precipitate may have formed in the bottle. This sediment is safe to consume, but if it is not removed it will make the wine look cloudy and taste gritty. Decanting leaves the sediment behind, yielding clean wine. (When decanting to remove sediment, a narrow container should be used instead of a wide-bottomed one.) In the case of older wines, one should not wait to pour the wine after decanting, but instead serve it immediately. The “bottle bouquet” of old wines, especially very old wines, can be exceptionally fleeting, often disappearing in less than 20 minutes.

In comparison to reds, white wines have little tannin and are not aged in bottles very long before serving. Thus they have little opportunity to develop bottle aromas that need evaporation. Instead their natural fruit aromas more specifically define their taste. Because these aromas are volatile, decanting actually results in a wine with much less of the aroma than the winemaker intended. In addition, because white wines contain fewer tannins and pigments, they don’t produce the same quantity of sediments that red wines do.

The author would like to thank Kay Bogart for her help in preparing this answer.

Scientia Vitis: Decanting the Chemistry of Wine Flavor

By Amy Coombs

http://www.chemheritage.org/pubs/ch-v26n4-articles/feature_wine_p1.html" onclick="window.open(this.href);return false;

Only one problem with the theories here: I know lots of people who decant white Burgundy and other serious whites, and I’ve found it very beneficial for newly released German riesling sometimes.

Now let the debate begin again…

Agree as it relates to German Riesling. Find in some cases, the younger ones taste considerably better on day 2. In general, see more downside than upside decanting wine. Suggest more often than not to decant in the glass. Decanting for the purpose of removing sediment never made a whole lot of sense to me? Pour with care into a glass as you would a decanter and all should be fine until you hit the final inch.

I am struck by a number of points here in the original post, which Mitch gleaned from a 2004 Scientific American article published by Professor Andrew L. Waterhouse of UC-Davis. I get the sense that Professor Waterhouse does not drink a whole lot of older wine or much high acid young wine, as I find decanting an essential tool for older bottles and often very useful for younger wines. I understand the theory that some hold (and that Nick voiced here) that decanting old wines to remove sediment is not essential if one pours carefully and does not pour the last portion of the bottle- often this is proferred as a way to not lose some of the aromatic and flavor complexity of the delicate old wine by over-exposure to oxygen in the decanter. For some old bottles this will work, like old claret, Burgundies or California wines, as long as one person is pouring and they keep the bottle as close as possible to the same angle once they start pouring and pour off the bottle’s contents in one fell swoop around the table (or if a wine cradle is used for the same purpose of keeping the bottle at the same angle). But too often I have been at tastings (particularly of old Burgndies, which for historical reasons seem to be the most prone to being served without decanting) where the bottle gets tilted back and forth as it is poured and the last glass poured is decidedly muddy from sediment and is not even remotely as pure and interesting on either the nose or palate as the first glass poured.

And this method simply does not work at all IME for certain wines, such as Barolo or Barbaresco or Port, where the sediment is decidedly more bitter than is the case with Bordeaux or Burgundy, and even a small amount that gets kicked up again into solution during the act of pouring the wine multiple times can greatly downgrade the enjoyment of the wine by introducing extraodrinary bitterness into the old wine from the sediment. My understanding is that much of the sediment that a red wine throws off over time is formed by the tannins chemically bonding with oxygen that works its way into the bottle (or was already present at bottling), and that the addition of another oxygen molecule to the chemical chain of the tannins is what causes the tannins to change from liquid to solid form and precipitate out of solution. Given the greater bitterness found in tannins from nebbiolo when young, this is a character that I emphatically do not want in my mature Barolo, and I find that simply in terms of sediment removal, decanting of mature Piemonte wines is obligatory to enjoy the wine to its fullest. Additionally, most mature (say 20 to 30 years old) Barolo or Barbaresco also tends to benefit dramatically from the exposure to oxygen during its time in decanter (probably because of its inherently higher acidity than many other red varietals), and an oxygen exchange of several hours is often extremely beneficial for these wines prior to serving. This is particularly true of the “traditionalist” school of Piemonte producers, where the wines tended to be raised in a more reductive atmosphere of old, large oak vessels during longer periods of pre-bottling maturation in the cellars. I would not even consider serving a 1982 Giacosa or Bartolo Mascarello out of my cellar without giving the wines at least a couple hours of decanting time, as the wines simply are not open without their extended exposure to oxygen, and to serve them without doing so is to miss much of the most impressive fireworks that wines such as this can deliver.

With younger wines, either red or white, I often decant them as well if they are high in acid, as I find that the wines often improve immeasurably if given some extended oxygenation. While this can be done over time in a glass (particularly if only one or two people are drinking the bottle), I find that the larger surface area provided by the decanter dramatically improves these wines briskly (say within the first 10-15 minutes) and quickly renders the wines both more enjoyable to drink and much easier to critically analyze. I prefer this method to extended aeration in a glass- particularly if a large glass (such as a Burgundy baloon) is used to maximize the oxygen exchange once the wine is poured- because I often find that many wines will show elevated levels of alcohol in larger glasses and an apparent disequilibrium of their constituent components that is not replicated in less wide-based glasses. While this is less apparent if one uses a Burgundy baloon for a young riesling from Germany, it will be quite evident if one uses the same glass for an Alsatian riesling or a white Burgundy or California chardonnay. The contrasting perceptions of alcohol in the wine are dramatic when poured in a large Burgundy baloon and a more standard, straight-sided and smaller white wine glass. So for these types of wines, I find that decanting is very useful when the wines are young.

In fact, I often think that the last twenty years of wine world evolution might have been dramatically different if more decanting was done on a systematic basis, particularly by those that write about wine. I have not tasted with Robert Parker, but I used to taste once in a while with Steve Tanzer, and Steve would invariably serve young wines from the bottle. He serves the wines single blind by category (an admirable way to taste IMO), but with higher acid wines such as young red Burgundies, I really feel that the wines are often quite bound up behind their acidities (particularly in higher acid vintages such as 2002 or 1996), and only show a small portion of their real characters when served in this manner, and I strongly prefer to taste such categories of wine out of decanters to allow the wines to more fully blossom for evaluation purposes. IME, wines that are lower in acid and aged in higher percentages of new oak often show better when poured out of bottle in their youth than wines with less new wood and higher acids. But out of decanter, I often find that the same low acid and highly oaked wines tend to collapse and become simple with aeration, while the high acid and less oaked wines blossom and become decidedly the more interesting category- at least in general terms.

Best,

John

I agree completely with what you say, John, in particular your link to acidity. I would add that Northern Rhones are another category where not decanting often seems to be a crime.

I’m baffled by the don’t-decant school. But, as you say, it may reflect the wines people are drinking. It sure doesn’t apply to the wines I like to drink.

I really appreciate the input of others here because my brief forays looking for molecular answers have left me empty-handed. Several interpretations that pop up with some regularity don’t, thus far, pass closer scrutiny (IMO).

1. The kinetics of (direct as opposed to peroxide-mediated) sulfite oxidation by molecular dioxygen, contrary to what’s encountered on the web, appears to be too slow to account for the beneficial transformations people swear by.
2. The kinetics of conventional polymerizations of polyphenols (e.g., tannins) in the timecourse of a few hours likewise seems somewhat of a stretch (IMO).
3. The kinetics of converting organic acids into their corresponding (fruity?) esters is probably much, much slower than the timeframes people use to aerate wines before drinking them.
4. One major change that many could probably concur with is, upon aerating a sealed wine, the wine’s so-called “half-cell potential” reduction-oxidation (redox) state would be dramatically altered very quickly. Jamie Goode has this to say about it (and my intent IS NOT to transform this thread into a screw cap debate, so let’s try to refrain from that minefield if we can ):

The term “reduction” is used extensively in tastings and I feel that in a lot of
circumstances people don’t really understand what it means.’ So, just what is a ‘reduced’ wine, and what do people mean by ‘reduction character’? We need to start with some elementary chemistry. It’s all about oxygen. ‘Reduction and oxidation are like orient and occident,’ explains Richard Gibson of Scorpex Wine Services, ‘opposites that depend on the relative absence of oxygen (reduction) and the relative presence of oxygen (oxidation).’ The precise definition depends on measuring what is known as the redox potential, which compares the affinity of substances for electrons. According to Gibson, this measure is rarely carried out in wines. Redox potential is measured in millivolts (mV). Typically, an aerated red wine will have a redox potential of 400–450 mV, whereas storage in the absence of air for some time will reduce this to 200–250mV. If levels get as low as 150mV then there is a danger that reduction problems can occur. Exposure to oxygen through winemaking practices such as racking, topping up barrels and filtering increases the level of dissolved oxygen in the wine and increases the redox potential, which will then return to 200–300mV. The effect of oxygen exposure is more severe in white wines, which have a lower buffering capacity (their redox state will change more easily) than reds. Another variable here is the level of free sulphur dioxide in the wine, which as an antioxidant will act protectively by absorbing the oxygen. Yeast lees also scavenge oxygen and protect the wine in a similar fashion, helping to lower the redox potential.

http://www.corkqc.com/newsandpress/WebReprint11.pdf> " onclick="window.open(this.href);return false;

Even so, this occurrence still leaves me scratching my head as to what sorts of chemical reactions ensue thereafter???

4b. One possibility that I have virtually no evidence to support would be aeration of wine could possibility oxidize several trace metals that had been previously kept in a more reduced (valence) state. Whether this change could lead to important reactions such as complexing with polyphenols is largely speculative on my part.

One Chowhound poster had this to add to this general topic:

In an ideal world, at the time that we choose to pull the cork, the wine in the bottle will have reached the optimal redox state to express fully the winemaker’s intentions. But we don’t always achieve this, and the right amount of aeration can complete the task if more oxygen is needed. On the other hand, if a wine has gone too far down the oxidation path, it will taste best right out of the bottle and will degrade quickly with time in the glass.

http://chowhound.chow.com/topics/286536> " onclick="window.open(this.href);return false;

Perhaps others can lend some real-world information because many of us would really appreciate knowing what’s happening in that fermented grape juice after unsealing the bottle.

I produce several viogniers from cooler vineyard sites in Santa Barbara County. I often decant my Sanford and Benedict vineyard viognier to many people’s surprise. Since I produce several single vineyard viogniers I have experimented with decanting them over the years and none of them stand up to the aeration the way the S&B does. In fact, the wine demands it to show its full potential (it certainly surprised Tanzer when he left it out all night.) It does not have higher acidity then the viognier from the Santa Maria valley so I don’t think it is a factor of acidity. I’m think it is a factor of the age of the vines since my S&B is over 20 years old, maybe close to 25 years old (the vineyard manager has been replaced over the years and nobody there seems to know the actual year it was planted, I started working with it in 1996) and my Santa Maria was planted in 1998. But even with older vines, such as Alban vineyards viognier (I assume his are fairly “old” by now, by Cal standards) with high alcohols (anything above 14.5 is high to me, even though some are balanced) that these wines tend to fall apart with decanting becoming more like a eau de vie and offering up hot alcohol aromas. So I would add that higher acidity, lower alcohol, and age of the vine are things to consider when deciding if one should or should not decant a white wine.

Viognier from SB County is the absolute best, in my opinion - this coming from a guy who is forever reducing his load in CA wines, moving to Italy and France instead. Still, Santa Barbara Viognier (Melville Verna’s, for example) is spectacular to me. Thank you to those who make it!

I’ve never known a white Burgundy to be harmed by decanting, indeed I think it’s essential even for modest wines, but I’m wary of decanting reds. A couple of days ago I decanted a Faiveley Mazis 94 which smelt just cascadingly marvellous going into the decanter. the aroma never came back though in other respects it was terrific.

Mechanism of Interaction of Polyphenols, Oxygen, and Sulfur Dioxide in Model Wine and Wine
John C. Danilewicz,*, John T. Seccombe and Jonathan Whelan

Am. J. Enol. Vitic. 59:2:128-136 (2008)

44 Sandwich Road, Ash, Canterbury, Kent CT3 2AF, UK, and Department of Wine, Plumpton College (University of Brighton), Ditchling Road, Plumpton, Nr Lewes, East Sussex BN7 3AE, UK.

• Corresponding author (email: jdanilewicz@btconnect.com)

The interaction of oxygen, sulfur dioxide, and 4-methylcatechol (4-MeC) was studied in a model wine containing catalytic concentrations of iron and copper in order to provide further evidence that when a catechol and oxygen interact, hydrogen peroxide and a quinone are formed, both of which react with SO2. The aerial oxidation of the catechol in the presence of benzenesulfinic acid (BSA) slowly produced the BSA-quinone adduct in high yield. It was also quickly prepared by adding ferric chloride, demonstrating that the quinone is cleanly produced in this model wine and that the catechol is rapidly oxidized by Fe(III) ions. This reaction is important in the catalytic function of the metal. The oxygen and SO2 molar reaction ratio was 1:2, which is consistent with one mole equivalent of SO2 reacting with hydrogen peroxide and a second with the quinone. When BSA was added to the system to trap the quinone the ratio was reduced to 1:1. The rate of reaction of oxygen and SO2 increased with catechol concentration. However, the rate of reaction of oxygen was also markedly accelerated by SO2 and by BSA, and it is proposed that substances that react with quinones accelerate catechol autoxidation. When 4-MeC was oxidized in the presence of SO2, ~38% of the quinone that was formed reacted with bisulfite to produce the sulfonic acid adduct and most of the remainder was reduced back to the catechol. The O2/SO2 molar reaction ratio in two red wines was 1:~1.7, suggesting that some nucleophilic substances may be competing with bisulfite for quinones. The rate of reaction of oxygen was also accelerated by SO2 in red wine.

Key words: sulfur dioxide, oxygen, catechols, iron

re whites - I’m of the “always decant white Burgundy, sometimes decant red” school of thought. Also young German rieslings and most good Loire whites (including older ones). Oh, and young Sauternes as well.

It may be sacrilege, but over the last couple of years I have started to doubt the net value of decanting, in general. Even with younger wines, it seems that, while they often improve in the decanter, they often close down a bit, as well. With older wines, my personal experiments seem to greatly favor not decanting. In both cases, I prefer to just let them evolve in the glass.

The exceptions I’ve found are some fortified and oxidized wines, particularly very old Madeira and Sherry.

Just to be clear, I am talking about wines I plan to drink (as opposed to taste)…I’m not in the industry so cannot say whether young wines (or barrel samples or whatever) benefit from vigorous decanting in a tasting environment.

Cheers!

Googling “[PDF] Organoleptic Defects in Wine”

http://www.google.com/search?hl=en&source=hp&q=[PDF]+Organoleptic+Defects+in+Wine&aq=f&oq=&aqi=" onclick="window.open(this.href);return false;

discloses a nice PDF that covers the role of oxidation in certain reactions in aerated wine.

Correlation of Perceived Wine Astringency to Cyclic Voltammetric Response

Petrovic SC (Petrovic, Steven C.)
AMERICAN JOURNAL OF ENOLOGY AND VITICULTURE Volume: 60 Issue: 3 Pages: 373-378 Published: 2009

Abstract: > A link between perceived astringency in red wines and the cyclic voltammetric response of those wines is described. Voltammetric current, generated in large part from the B-ring oxidation of flavan-3-ols and malvidin, is significantly correlated to the perceived astringency (R-2 = 0.68) of a set of red wines having previously undergone sensory evaluation. It is suggested that the concentration-dependent formation of a passivation layer on a glassy carbon electrode, resulting from polymerization of electrooxidized wine phenolics, could be monitored by plotting the ratio of the A-ring:B-ring oxidation current. This current ratio is highly correlated to the perceived astringency (R-2 = 0.77) and to the sum of the epicatechin and epigallocatechin subunit concentration in the wines as previously determined by phloroglucinolysis (R-2 = 0.84). These results indicate that electrochemical determination of astringency is correlated to concentration and passivation effects at a glassy carbon electrode. Using simple dilution in a model wine matrix for sample preparation, cyclic voltammetry compares favorably with established analytical methods (e.g., protein precipitation and liquid chromatography) in the effort to correlate analytical response to red wine astringency.

From Ronald Jackson’s Wine Science:

Iron favors the polymerization of phenolics with acetaldehyde, whereas manganese ions catalyze the synthesis of acetaldehyde. … Although copper and iron can induce metallic astringent tastes, this occurs only at concentrations higher than those usually found in wine. … High sulfite contents can give wine a slightly salty-bitter taste.

Wine Science: Principles and Applications - Ronald S. Jackson - Google Books" onclick="window.open(this.href);return false;

I uncorked my first 2005 Rauzan-Segla yesterday (infanticide in the name of research ) and now understand why this wine received such high praise. Lovely aromas and flavors through and through. The small portion that I poured into a decanter soon became jumbled aromatically and flavor-wise.

Why a particular wine like this Margaux didn’t benefit from brief aeration has been firmly filed upstairs, however… I also intend to continue such side-by-side comparisons.