For you experts and those who talk of reduction in certain OR Pinots. Back when I was firing ceramics, we strived for reduced glazes which were starved for oxygen in the final firing. We called that final reduction. So is reduction in wines caused by lack of oxygen and the blowing off caused by the wine oxidizing? If that is true are the wines purposely fermented or aged in an oxygen depletion regimen? ![[thankyou.gif]](/uploads/db3686/original/2X/d/df165fe9c1593d19166ae7e1ffe5e272089cc07b.gif "thankyou"){kind=small}
You’re on the right track, I think.
As it’s used to describe flavors, it is related to a relative shortage of oxygen along the way. When people say a wine is reduced, they usually means it shows some sulfur aromas that need oxygen to dissipate or which might have been avoided if the wine had had a little more exposure to oxygen.
The alternative is not oxidation (too much exposure to oxygen). You hope for a happy medium. But a bit of reduction isn’t so bad, in my book anyway. It’s very common with syrah, particularly. I’ll defer to others on why that is.
is reduction in wines caused by lack of oxygen and the blowing off caused by the wine oxidizing? If that is true are the wines purposely fermented or aged in an oxygen depletion regimen?
I think John is right.
But you have some other assumptions here.
When you don’t have a lot of oxygen, it is a reductive environment. Sulfur is added to mop up the oxygen and if there is no access to air, you get a reductive wine. Some grapes are more prone to oxidation, some to reduction, and the winemaker has to figure out what to do in each case.
But “blowing off” isn’t really what it sounds like. What happens is that the sulfur molecules that stink combine with oxygen and form bigger molecules The bigger molecules aren’t as volatile so they stay in the wine and you don’t smell them. The sulfur is still there however.
And yes, wines are usually aged in a non-oxidative environment. Wood is slightly porous and you can get micro-oxygenation through the wood and that actually helps stabilize the wine. But too much oxygen will end up ruining your wine, unless that’s what you want, as in the case of some sherries and Madeiras.
From a chemists perspective, reduction is the opposite of oxidation. Iron rusting is an example of oxidation (i.e. rust is iron oxide…aka oxidized iron). Whatever caused the iron to rust becomes reduced…i.e. oxidation and reduction always happens in pairs…one thing becomes oxidized and the other becomes reduced (the not very helpful description is that the oxidized molecule loses an electron (or its ‘oxidation state’ is increased) and the reduced molecule gains an electron (or has its oxidation state lowered)).
I’m assuming in your glazing/firing example, your final firing creates mostly ‘non-oxide’ compounds. If that’s the case…that seems like a decent/accurate use of the term reduced.
John’s right that reduction refers to wines that contain complex sulfur containing compounds that get produced in barrel or recently bottled wine. However, the production of these compounds are not the same as an oxidation-reduction reaction (like the iron rusting is).
In wine, reduction refers to young wine (in barrel) that contains very little oxygen (which is a poor/incorrect use of the term reduction)…and young wines in that state often produce complex sulfur containing compounds.
Young wines, esp wines in barrel, have many complex chemical reactions that require oxygen molecules to complete correctly. One reason wine is stored in oak barrels is they provide a slow/constant source of air/oxygen to the wine…so hopefully the complex reactions need for oxygen will be satisfied. If it isn’t, in a Cab for example, then the wine is racked (moved to tank and back to barrel), which puts some dissolved oxygen into the wine. If the wine isn’t racked (meaning there’s little oxygen in the wine) then these complex reactions may occur anyways, but using a sulfur molecule instead of oxygen (creating one of the complex sulfur molecules). A wine’s need for oxygen is one of the factors that determines the best time to bottle a wine (since the wine will get very little oxygen once bottled).
Note that these ‘complex chemical reactions that require oxygen’ are not examples of oxidation…the reactions are producing new molecules that contain one (or more) oxygen…e.g. producing water (H2O) from hydrogen (H2) and Oxygen (O2) isn’t an oxidation reaction either.
Whether a wine produces these sulfur molecules (aka thiols et al) or not depends on the wine’s need for oxygen (i.e. the number of ‘complex chemical reactions that require oxygen’ that are occurring), the availability of sulfur in a useful form to these reactions and many other factors I’m sure. The lees at the bottom of the barrel is a common place for these sulfur molecules to be produced because lees absorb oxygen (creating the low oxygen conditions) and lees often/sometimes contain amino acids (a common source of sulfur).
Whether you can smell/taste these sulfur/thiol molecules or not depends on the ‘sensory perception threshold’ of the sulfur molecule in question. If the concentration of, for example, dimethyl sulfide is above its perception threshold then you’ll smell/taste it. If it’s below the perception threshold then you won’t smell/taste it. However, the perception threshold is different depending on whether the molecule is oxidized or not. Often times, the oxidized form has a much much higher perception threshold than the non-oxidised form does. This means you might smell the sulfur compound when the wine is first opened (i.e. when the sulfur compound is not yet oxidized and has a lower perception threshold…meaning less is needed to smell it)…and later, when the wine has gotten some air, the sulfur compound oxidizes the smell goes away…because the perception threshold went up when it becomes oxidized (higher being less likely to be smelled). Of course, if there’s so much of the sulfur compound present in the wine then it might be above both oxidized and non-oxidized perception threshold, so in that case you’ll smell it no matter what.
In addition to this oxidized vs non-oxidized perception threshold thing…as Greg describes, some sulfur compounds can turn into different compounds when they become oxidized. For example, an oxidized Thiol might turn into a Disulfide. Generally speaking disulfides are far more stinky/nasty, and much more difficult to get rid of. However, this is less common, and doesn’t explain why wines ‘clean up’ with some air (which is explained by the different perception thresholds, discussed above). There has to be a simpler way of expressing all of this without missing something, but I’m too tired to figure that out…anyways, if you’ve read this far, I’m surprised 
Great post Eric. Even late at night!
Thanks for the reply Eric, I was wanting the wine maker response. I know enough chemistry to be dangerous. All this discussion of sulphur is very informing. I have a sulphur sensitivity and need to be very careful and not eat food containing sulphur, egg yolks being the number one offender. So far Sulfite has not been a problem. Those stinky vegetables of the cabbage family have been off limits for the last ten years, so those funky wines may not be recommended either.
Make sure to not confuse oxidation with oxygenation- or more properly aeration. Aeration is dissolved air- oxygen et al- into the wine helping it open by forcing aromatic compounds into the air. Oxidation is a chemical reaction and is a bad thing.
Just thought I’d bump this…
Had a bottle a few nights ago, it was an inexpensive rhone that I bought for weeknights… I popped, poured and it stunk. My first thought, this is not corked, not oxidized. I haven’t experienced this before… WHAT IS THIS FLAW?
Thanks to some searching here, it was Reduction.
To me, the wine clearly reeked of burnt rubber.
The best part? My son came home… Saw I had a bottle and glass sitting in the kitchen while I was enjoying something else. He asked about it and I told him the bottle was flawed. He took a smell… A sip. And said, “Dad, this smells like sulfur… Rubber?” I taught the boy well.
I tried to intro air into it over the next night. No luck, still stunk. Down the sink it went. Meh…
Way to dig up an old thread!
And nice that your kid knows.
I wouldn’t have poured it down the sink though. You could have tried dropping a bit of copper into the wine if you have old pennies that were actually made of copper.
Just a couple of additional thoughts. I am going to avoid the serious chemistry for this and stick with how I see reduction as a player in the winery and my wines.
While oxygen plays a part in affecting reductive aromas(and flavors), the lack of Oxygen is not necessarily the cause. Yeast stress can/will cause sulphite production(H2S in a simple form). Once the H2S is formed it can continue to become more complex, if not addressed, and the more complex forms of reduction are more stable, i.e. resistant to and unchanging in the presence of or exposure to oxygen, copper, silver, pennies, etc. A fermentation that is cooking along quickly is an oxygen deprived environment, and simple reduction can become complex reduction very quickly.
Burnt rubber is a complex form of reduction, and in my experience, very difficult to evolve the wine away from. Hair salon permanent solution, garlic, creamed corn, swamp gas, and burnt electrical wire or rubber are all complex reduction. Bummer for the wines.
Rotten eggs, farts, smoke/campfire(not to be confused with actual smoke taint), weedy, cereal grain, and celery seed are all milder reductive aromas and with aeration(not oxidation) should blow off.
IMHO-coffee, mocha, bacon fat, smoke, charcuterie, and cooked meat/leather are also mild, and desired, forms of reduction. I often get a fennel cool salami aroma from Pinot Noir made from one of our vineyards when it’s young. It blows off within 10 minutes or so of being exposed to air, and I really enjoy the aromatic. A very general rule: non-fruit aromas that dissipate with aeration are likely to be or be connected to reductive aromas. This is only a general rule, there are plenty of exceptions. Think about it though, exposure to air moves the wine away from the reductive process. A young wine hasn’t had time to polymerize as many complex molecules, and mostly smells like fruit(or stem in our case).
Last-Cameron. The famous Cameron funk is mostly a good dose of reductive winemaking. I think the high level of reduction is part of what makes John’s wines so ageable (and complex as they become mature). It’s not always there, but John’s wines are always damn good wines whether reductive/funky or not and the funky ones are usually smoking good with 10 years in the bottle.
Sulfides produced in fermentation by amino acid scavenging nitrogen deprived yeast is the result of a metabolic pathway.
Sulfides produced by anaerobic decomposition and putrefication are something else. Think protein hydrolysis, yeast bodies and fruit solids breaking down in the absence of oxygen.
Ewww…! Putrefication? ! ![[bleh.gif]](/uploads/db3686/original/2X/c/cbb27a94fa73081862abf910a8bfa05e2ae2f5c3.gif "[bleh.gif]"){kind=small}
Glad Peter brought up the two sources of sulphide characters. Nitrogen-starved yeast is probably the primary cause. Yeasts will metabolise sulphur compounds in the wine if they can’t get enough nitrogen. Perhaps Syrah is naturally low in nitrogen compounds (because of where it is grown?).
But it’s true that sulphide compounds can be formed after fermentation. Usually because of the breakdown of heavy lees. However, I’ve experienced strong sulphide characters in a wine where (I think) the sulphites that were added were not mixed thoroughly and the wine resting in the drainage tube of the tank became heavily reduced in character. Fortunately it was localized and I could just throw away that part.
You may have been too quick to pour it out. I had a bottle of Copain Syrah the other night that had real bad sulphur aromas that were completely gone the next day. Like John Morris mentioned up thread this is something I also find very common with Syrah.
Now if your wine was a Beaucastel all bets are off.
Northern or Southern Rhone?
Syrah is quite prone to reduction. Northern Rhone syrah can often have strong sulfur scents when first opened. Grenache, on the other hand, is very prone to oxidation.
Adding to the complexity, your nose is a very sensitive, but quirky, chemical sensor. Certain compounds are detectable at low levels as a certain smell, but at higher levels transform into a different smell. Thiols are famous for this.
Great discussion guys and nice to read the different thoughts from wine makers.
Some of these may indeed be due to sulfur-containing compounds, but it’s my own belief that others (particularly bacon, smoke, leather) are due to brett-produced compounds (which, at least the dominant ones, aren’t sulfur-containing).
Wine is a very complicated beast, and identifying the individual sources of a complex aroma can be difficult.
Good assessment John.
It was northern Rhone… Crozes hermitage to be exact.
Like I said, it was inexpensive wine ($16-17 bottle) I bought for weeknights at TW&M. I left it in the bottle and out for about 22 hours. The smell of burnt rubber was overwhelming and interestingly enough, upon recollection (and seeing Marcus’ description of) “Perm Solution” fits the bill as well. As I said, 22 hours out getting air and while it was not nearly as prominent, that small was still there.
Life is too short to drink flawed wine so I poured it out… I elected to pop a Herman Story John Sebastiano last night because my teeth aren’t purple enough.