Reductive vs Sulfur

Can you experts weigh in on the differences…if any? When you smell a white burg for instance that has that match strike smokiness to it…some say it’s reductive…and some say lot of sulfur. I know reductive is the winemaking process of limited oxygen, which promotes more freshness, as does adding sulfur? Do they both produce the same smell and flavor profiles like the match strike, rubber, rotten eggs etc? Can you have a reductive wine that sees 0 sulfur? In general do winemakers go with more sulfur in whites, and less reductive winemaking…and vice versa with reds? Will a reductive wine “blow off” easier than a more sulfur added wine? For those who have smelled the MOST stank wine EVER the 2007 D. Leroy Aligote…is that just the cause of too much sulfur, AND too much reductive winemaking?
Thoughts?

As I understand it, the amount of sulfur added is just one potential contributor to reduced aromas and flavor. Those smells (and sometimes tastes) are also a function of other winemaking techniques and the grape type.

Dr. Vinny on WS has a pretty good summary:

[Reduced aromas] generally result from the presence of a volatile sulfur compound, or mercaptans, and can be the result of reductive winemaking. Wine needs a certain amount of oxygen to polymerize (have its molecules combine), and if it doesn’t, the reduced notes may come in.

How do you recognize reduced notes? Sometimes there’s a whiff of rotten eggs, rubber, struck matches or even sewage. When it’s just a whiff, decanting or swirling the wine in your glass might allow these notes to “blow off,” and it’s not considered a flaw—there might be a really beautiful wine underneath those notes. If there’s more than a whiff and those notes won’t go away, it’s not a good thing.

Some wines lend themselves to reductive winemaking—Syrah, for example, is more reductive than Pinot Noir. If a winemaker is worried that they’ve overdone it on the reductive winemaking and want to reduce “reduced” notes, they can do a process called racking, where wine is moved from one container to another, which exposes it to oxygen and can usually help.

The match stick scent is sulfur dioxide, which seems to dissipate fairly quickly. By contrast, the rotten egg smell, hydrogen sulfide, tends to stick around.

I have argued this as well in a thread about the “Coche signature”, though it’s not entirely clear this is the case (matchstick has a lot of phosphorus as well, so I don’t think it can be attributed just to SO2).

But Buzz raises an excellent point: I wish that we would distinguish between “reduction” and SO2. For me, SO2 is not reduction, it’s just SO2, call it that (and alert Meadows). Reduction should mean some form of sulfur contamination other than SO2 (and frankly, I’d be happy if we just abolished the term “reduction” altogether, and called it something else, because the term is totally mis-used in wine terminology).

Respectfully, the burnt matchstick aroma is a mercaptan: ethyl mercaptan. Here’s a rather lengthy article by Jamie Goode that may provide some insightful info.

FWIW, I’ve found it difficult to discern SO2 in bottled wine. Usually, the SO2 content needs to exceed 30ppm free SO2 before it becomes noticeable for most tasters; and post-bottling free SO2 drops significantly. With reduction, ppb levels are easily noticeable. I see more white Burgundy being bottled with higher amounts of free SO2. But this gets complicated when there are also reductive compounds in the wine.

He writes that, but it’s not clear to me it’s actually the case. Ethanethiol appears to be the odorant added to LPG (what’s in your BBQ propane tank), and that definitely does not smell like burnt matchstick.

I agree…I don’t see any way that Ethanethiol (aka ethyl mercaptan, before Thiols did a hostile takeover of the Mercaptan group) is responsible for the struck match smell of WBs. Ethanethiol’s odor is generally described as leeks, onions, durian or cooked cabbage…which is a fair stretch from struck match. Also, I smell wine with high levels of SO2 (unappealing imo) and it’s different than struck match (generally appealing).

Also, the members of the old Mercaptan group always seemed too limited for the range of complex sulfur (aka reductive) odors that make their appearance in wine. My guess is the struck match is another thiol (outside of the transposed mercaptans), tho Alan has disagreed with this. Despite that, another thiol is the most plausible imo.

Dissipating quickly: When thiols get some oxygen, their perception threshold (concentration level required to smell) goes up…meaning many thiols seem to ‘disappear’ with air. They didn’t disappear…the perception threshold went above the thiol’s concentration in the wine you’re smelling/drinking. Some thiols have a super low perception threshold that they’re always there to smell, with or without air. Anyways, a smell appearing to dissipate quickly isn’t proof that it’s SO2 (also, wines with high SO2 levels, PYCM for example, generally take a lot of air time to lower).

+1

Approaching this from the non-science perspective, I see reduction and sulfur two separate things in white burgundy. I associate reduction with a flinty, slightly struck match aroma. I associate sulfur with an overt sulfur aroma (with is a known entity to me as I grew up and still live near an active sulfur spring. Closest smell I can think of is rotten eggs). If a white burgundy is reduced but not overtly tainted with excess sulfur, I do not get the sulfur or rotten egg aroma. In my view a wine can have one or the other or both, but I see them often confused in tasting notes. Especially amateur tasting notes.

In wines like PYCM I often get reduction, but rarely get sulfur.

plenty of wines made without much or even any sulphur are reductive, and sometimes to a fault. get yourself a bottle of richard leroy and it will seem as most conventional white burgundy is not reductive by comparison.

We need to differentiate between reductive and reduced - the former is somewhat of a ‘temporary’ situation that will dissipate with air (like struck match - it will go away) - whereas the latter does not. Mercaptans are a result of a wine being reduced, and these are much much more difficult to get rid of in a wine (it involved ascorbic acid to hyper-oxidize and then copper sulfate to remove) . . .

Cheers.

No, mercaptans in wine are a result of too little oxygen (and perhaps other factors). Wine can’t be “reduced”

Unless you’re cooking with it…

But I get that it’s a mis-used terminology that isn’t going to go away.

Alan,

That is the term that I learned and that is used to differentiate it from reduction. As I said, reduction is relatively easy to reverse but if it goes beyond that, it is not.

Cheers.

I really hesitate to chime in when Alan is involved in a topic like this but I think that when it comes to wine, the term “reductive” is a little bit like “minerality”.

In other words, pretty much a catch-all term for a whole lot of things that may be related to chemical reduction, or may not be.

If I remember my chemistry, reduction is when electrons are gained. That would be the opposite of oxidation because oxygen likes to steal electrons when it can. It likes to react with things and that’s why we keep it away from wine. But those smells we call reductive can come from various forms of sulfur. They can probably come from other things too. When people write tasting notes, I suspect that they all mean something a little different.

And add to all that the fact that when you open a bottle and pour the wine, and some of the sulfur compounds have access to oxygen, they’ll change and the aroma of the wine will change and then it’s even less of an exact description.

I’ve heard people say a wine is reductive because it has some bell pepper notes.

The OP had an interesting question but my guess is that half the people can distinguish things chemically and write about them accordingly, half the people just identify specific aromas that they define as reductive, and half the people just refer to anything stinky as reductive.

!

Larry, I get that, and I’m just being unnecessarily pedantic, though it bugs me a bit that a scientific institution would use a term like that so improperly. “Oxygen deficient” or something of that sort would be a much more accurate description for what “reductive” is meant to convey, but I get that it doesn’t roll off the tongue so nicely.

So far, I don’t feel like anyone has really answered the OP’s question, which has really been the state of this issue for many years as far as I’m concerned. Is the character of older Coche (newer vintages seem to be missing this), older leflaive, and PCYM from added sulfur or reductive winemaking?

John,

SO2 added during the winemaking process or especially right before bottling will certainly remain in bottle for quite some time, depending upon the closure and the pH of said wine. That said, overtime, this will certainly diminish to the point where little to no free SO2 will be evident.

How old are these wines?

And more importantly, what happens as they sit open and oxidized? What changes occur to the wines?

If stinky sulfur compounds remain present for a long time after opening, my guess is that the wine has been afflicted with mercaptans. If it dissipates rather quickly, I guess is that it is slightly reductive and the oxygen added will get rid of this.

I have not had these specific wines and that’s why I’m asking all of these questions. Cheers.

The only explanation that makes sense to me is that the struck match character is from ‘complex sulfur compounds’ (i.e. thiols/etc, i.e. compounds formed during oxygen deficient (reductive) winemaking), rather than being something as simple as SO2 in the wine. And, I’m sorry I describe things in an overly obtuse way sometimes (perhaps more than just sometimes).

Yes, I too have wondered about this, because there is a characteristic of these white Burgundies, particularly older Leflaive’s in the 90’s and 80’s, and Coche-Dury’s in the same period and perhaps later, which I have found attractive and have described as a mild “creosote” aroma and perhaps this is the same as the “matchstick” aroma that is described. Though similar between older Leflaives and older Coche, they are not identical, I think. Some of the wines carried this to an extreme…for example, some of the 2004 Leflaives, particularly the Clavoillon, was terminally reduced and undrinkwble. But…again…what is this characteristic from…added sulfur, or reductive winemaking or something else?

Robert,

If a wine is ‘terminally reduced’, it would be due to winemaking practices, not SO2 on its own. These wines probably showed signs of ‘reduction’ during the winemaking process and this was not ‘alleviated’ and things went south. Again, I’m assuming we are talking ‘apples to apples’ and these wines do not ‘improve’, even with lots and and lots of aeration - true?

Cheers.

I think we can all agree that’s just wrong.