“Reduction”? - Augment your understanding…
Grapes and wines are the heirs to a bevy of diseases, pests, and flaws. The identification of “corkiness” for example has become quite easy to for many wine drinkers, but other flaws in wine are a bit more difficult to identify in the glass, and perhaps even less well understood on the “theoretical” side. Here’s a look at one of these “classic” flaws in wine: reduction.
In order to not get sucked into too much technical language, the simplified definition of reduction is a wine that has been deprived of oxygen at the wrong time, and reduction can also be said to be the opposite of oxidation. Things that are “reduced” (in this case, wine) have gained the electrons from the things that have been oxidized within the same closed system. One reaction cannot happen with the same amount of the other happening on the other side of the “equation”.
Now the word “reduction” used in the sense of “reductive winemaking” is the current modern standard for making wines, and most contemporary quality-minded winemakers take full advantage of it. In employing this technique, towards the end of alcoholic fermentation on into the aging process, reduction is a most desireable state to cultivate. The presence of reduction in these stages of winemaking protects and preserves the acidity and fruit flavors that modern drinkers consider to be a baseline requirement in well made wines. Reduction protects wines from oxidation. Wines that have oxidized (unintentionally or intentionally - many old-styled wines are purposely made in an “oxidative” style - Sherry and Madeira for example are highly oxidized wines) often lack primary fruit flavors, and are often said to be “flat” in the mouth.
So why is reduction sometimes good and sometimes bad? Well, like so many things, its all a matter of degrees. Reduction is a good thing until there’s too much of it, and then it’s bad. Simple, right? Fundamentally what happens is the wine’s tannins become polymerized (small molecules combining to produce large strings or clumps of molecules) and when this transformation has occured, the conditions favorable for the formation of sulfer compounds like mercaptans (the smelly compounds added to natural gas by the way) and hydrogen sulfide gain ascendance. So essentially, too much reduction creates the conditions for the formation of these stinky compounds. The reduction reaction itself, especially at lower levels, is harmless and olfactorily undetectable.
So enough with the organic chemistry lessons. Let’s cut to the chase - What does the product of reduction smell like, and what can I do about it if I meet it in a dark alley? The descriptors utilized for the resulting smells vary quite widely, but the biggest “basket” into which most fall could be said to be “funky”. Specific aromas like rotting vegetation, a just-struck match, hardboiled eggs, sewage, and burnt rubber are the most commonly cited in specifically describing what the effects of reduction smell like in the glass. So what can be done about this? In some cases, absolutely nothing. In certain instances the level of polymerization is so high that the process cannot be reveresed with anything less than a BIG chemistry set. But in many less grave cases, all that is required is AIR - remember the relationship outlined above - when one compound is reduced, another is oxidized. The stinkiness that results in a wine is the product of the wrong things being reduced and oxidized, and your job to to set things right again. In many cases, reductive smells dissipate naturally over time as the bottle remains opened. If you’ve ever heard people talking about funky smells “blowing off”, the reduction of reduction is almost surely to what they were referring. If leaving a bottle open for 15 or 20 minutes doesn’t do the trick, take the next step - decant! The more air one can introduce into the wine, the better chance one has of de-smellifying the wine in question. But, if after an hour or two, there’s no perceptible change in the smell of the wine, until you can get back to the shop where you bought it for a refund, the prescription is opening another bottle.
PS - In my experience there are certain grapes whose wines tend to reduce more frequently, the two most common being the Italian varieties of Dolcetto and especially Montepulciano d’Abruzzo. Exactly why this is so, I’m not sure, but it does indeed seem to occur more with these two than many others that I’ve encountered. Give wines made from these varieties the benfit of the doubt if you do come accross some “off” smells when the cork is first pulled…
TOM CIOCCO
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any effect on alchohol levels when using this practice?
Comment by Russ J — February 12, 2007 @ 4:33 pm
Russ-
While I’m not an oenologist, I think that the only factor that effects alcohol levels in wines are total sugar levels in the must and the types of yeasts used to ferment it. Anybody?
TOM CIOCCO
Comment by Tom C — February 12, 2007 @ 4:47 pm
In my experience, grenache is another grape that is prone to reductive faults — ample oxygen is needed during fermentation to prevent the development of hydrogen sulfide. Tasted a 90% garnacha Priorat as part of a wine education class last weekend that showed this problem — even the participants who usually don’t say anything commented on it.
Comment by NeedzWine — February 12, 2007 @ 6:05 pm
Thanks for the info, Tom! I had never heard of this whole concept of over-reduction. I went back through all of the current entries in your blog last night, and I must say, I’ve learned alot, and had plenty of great chuckles along the way. Thanks again, and keep up the good work!
P.S. Although I know that reduction can lead to some really ugly, stinky results, did you HAVE to start off with that god-awful photo??? LOL (Who is that, anyway?) It could’ve scared several readers away from learning something useful. Heheh.
Comment by dealbhadair — February 13, 2007 @ 3:20 am
dealbhadair -
Thanks for the comments! Yeah, i though the picture was “appropriate”…I thought that a wine starved of oxygen was just about as ugly as this gentleman deprived of the same…
TOM CIOCCO
Comment by Tom C — February 13, 2007 @ 11:00 am
Is this the process that seems to make screw cap sealed wines a little stinky when first opened?
Comment by JimKay — February 15, 2007 @ 9:07 pm
Jim-
Yes indeedy - you are correct…there does seems to be tendency for screwcapped wines to help MAINTAIN a state of reduction in a wine - just want to be clear about this, the wine goes into the bottle reduced, the closure justs helps to keep it that way…
TOM CIOCCO
Comment by Tom C — February 16, 2007 @ 11:03 am
Hey Tom, interesting post. I have a question about this use of reduction in normal dry wines (not sherry or smth like that): is this reduction proces also a part of the vinfication in Jura Vin de Paille and Vin Jaunes?
The first (and only) time I tasted a Vin Jaune it seemed to more or less reduced, there was some Sherry-like tinge on it? The grower said that was typical, but, is it?
Comment by TSchampaert — February 18, 2007 @ 10:20 am
TSchampaert-
The Jura wines like Vin de Paille and Vin Jaune are not reduced, but rather just the opposite - they are intentionally oxidized just like Sherry and Madeira, and this is effected in the same way - with the use of a special mold that floats on top of the aging wine that in Spain is called a “flor”…there is also a Sardinian wine called Vernaccia di Oristano (no relation to the Vernaccia from Tuscany, by the way) that is also made in this intentionally oxidized, not reduced, style.
TOM CIOCCO
Comment by Tom C — February 19, 2007 @ 11:00 am
See, I thought there was smth wrong with that winemaker and the wine: this reduced tinge on a sherry-like wine (sorry for the crude generalisation) … . Good that my mistrust prevented me from buying. Anyway, thx for the answer and eh, Vernaccia di O, ever came across one? I never did, and I really want to taste it once. I am planning to go to Sardinia if I can’t get it over here.
Comment by TSchampaert — February 20, 2007 @ 9:56 am
Tom Im suprised not to have heard any comments on the possible confusion of reductive wines with bret infested wines.Certainly the downstream chemistry of bret(often 4ep and 4eg) producing the barnyard,swetty leather and sometimes fecal characterand would seem to provide a comparative olifactory condition. In fact do the downsteam reactions producing bret required a reduced atmosphere?
Comment by Al — August 7, 2007 @ 1:17 pm
Al-
Yes, good point. While most of the time, I and most of my colleagues can separate reduction odors from those produced by brettanomyces (a common, harmless, but nonetheless smelly bacteria that can infect wines), at times, they can be hard to distinguish (in fact, in times such as these, I’ve often thought that certain wines could be both reduced AND bretty…sometimes, only time can determine…in my experience, reduction “blows off”. Brett does not.
TOM CIOCCO
Comment by Tom C — August 7, 2007 @ 1:26 pm