# Fermentation funk odors



## verdot (Oct 23, 2021)

Hi everyone. I’m fermenting my first crop of merlot and cab sauv from my small vineyard, and have a about 12 gallons of must fermenting at proper temps for the past few days. Everything seems fine, but I’m getting a strange, funky, rotten grape and deviled eggs (not sulfur) kind of odor that’s very unpleasant. Should this be cause for concern?


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## salcoco (Oct 23, 2021)

any off odor could be stressed yeast did you add any yeast nutrient?


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## verdot (Oct 23, 2021)

I did add yeast nutrient when the yeast were pitched and a few days after fermentation began.


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## CDrew (Oct 23, 2021)

It sure sounds like H2S. And yes, address immediately. Is it done fermenting? if not, some more nutrient would be my next move. What yeast? Next year consider an H2S preventing yeast like Avante. Read up on these Renaissance yeasts which cannot produce H2S.

If its done fermenting, you might try to splash rack. When that doesn't work, consider Reduless. Full disclaimer-I've never used, but have heard it's very effective.


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## Juniper Hill (Oct 24, 2021)

Agree with nutrient if still fermenting. Also, lots (3 or more per day) of punch downs will introduce more oxygen and help drive off sulfur. Delastage is another way to add more oxygen, but is a bit of a pita.


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## Juniper Hill (Oct 24, 2021)

Which yeast did you use?


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## Cap Puncher (Oct 24, 2021)

As CDrew mentioned, reduless is a good option. I have used it and it works for smaller issues. For now, I’d add nutrient/optired or nobelese if you have it. Delestage is a good idea with nutrient. It really depends what part of fermentation you are in. Lots of oxygen is good, but actually can cause the yeast to want more nutrients. Scott Labs has a sulfur like odor protocol for red wine that you should look at. I wouldn’t add reduless until after alcoholic fermentation is complete.


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## verdot (Oct 24, 2021)

Thanks for all the great suggestions, guys. I used red star premier rouge yeast, and the must is getting three punch downs a day. I’m going to hope for the smell to dissipate more after pressing today. I was mainly curious if a musty/unpleasant smell was expected a few days into fermentation with grape must or if it should be expected to smell more like the kits I have used in the past which were more of an expected yeast/fruity fermentation smell. Does seem like H2S or some other byproduct may be lurking, though, but I’ll resist intervening with additives at this point other than some nutrient at pressing and let it run its course.


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## balatonwine (Oct 24, 2021)

verdot said:


> deviled eggs



As other said, this is most likely hydrogen sulfide (H2S).

And yes, needs to be dealt with quickly.

But it can be complicated. To deal with all the possible causes, and different solutions, I recommend reading the link below, from UC Davis. Because H2S can form for many reasons, depending on many factors, some of which have nothing to do with needing to add more yeast nutrient.





__





Off Characters


The second type of problem that can arise during fermentation is the development of an unpleasant aroma. What is deemed "objectionable" may depend upon the circumstances and aromatic profile of the wine. Some compounds, such as hydrogen sulfide (H2S), are universally perceived as negative while...




wineserver.ucdavis.edu





Ergo, it is complicated.

My personal suggestion, is to really first check if you might have an overly reductive environment. That is, not simply should you punch down the cap 3 or more times a day, but give it a good splashing stir each time for a minute or two. If you notice a decline in odor in 24 hours, and complete removal within 48 hours, then your wine was simply over reductive. Keep up this aeration schedule till about 2/3 of the sugar is gone. Then reduce severity to not over oxidize the wine (but keep a daily smell test and repeat the rigorous procedure if needed).

If the 48 hour test above fails, then, and only then, would I recommend trying to correct via chemistry with more nutrients. But adding nutrients if not needed now, might cause issues later.

If you have H2S later in fermentation, then other actions should be considered. See the above article for ideas.

Hope this helps.


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## winemaker81 (Oct 24, 2021)

balatonwine said:


> And yes, needs to be dealt with quickly.


This is essential advice. Most things in winemaking are "wait -n- see". H2S is the counter example. The longer you delay, the more difficult it will be to correct it. H2S forms mercaptans, and once that happens you have to treat that off-flavor as well.

Immediately stir very well and double-dose the K-meta. Ensure the area is well ventilated.

Reduless works well, but hopefully the stirring/K-meta will fix it so you don't need it. It bleaches the wine and mutes flavors. This is better than throwing the wine out, but it's best to avoid it if you can.


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## Ct Winemaker (Oct 24, 2021)

There are a variety of smells associated with fermentation most of which are normal and not necessarily “good”. When the fermentation is fully developed (cranking along at high speed!), there is usually associated heat and some funky odors. What you are smelling may be completely normal and not an issue. As long as you have been using an appropriate nutrient protocol ( fermaid O and K for example), temps aren’t out of control, and your punching down regularly (3 time per day), I would go easy with attempting to adjust too early. Also, not sure about the k-meta suggestion. If that is referring to potassium Metabisulfite, adding it during fermentation could end in a stalled fermentation. It should be added only when fermentation is complete (including Malolactic Fermentation if you are doing that).


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## winemaker81 (Oct 24, 2021)

Ct Winemaker said:


> Also, not sure about the k-meta suggestion. If that is referring to potassium Metabisulfite, adding it during fermentation could end in a stalled fermentation.


H2S is an unmistakable odor. Rotten egg and swamp gas are good descriptions. When this occurs, there is nothing worse that can happen to the wine. Untreated, the wine is destroyed, so fermentation stopping is not honestly a concern. Do a search -- vigorous stirring and a high dose to K-meta (potassium metabisulfite) is a recognized first treatment. If fermentation is not completed, adding nutrient is suggested.


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## Cap Puncher (Oct 25, 2021)

winemaker81 said:


> Reduless works well, but hopefully the stirring/K-meta will fix it so you don't need it. It bleaches the wine and mutes flavors. This is better than throwing the wine out, but it's best to avoid it if you can.


Again, I agree that reduless works well, but to say that it “bleaches” wine and mutes flavors is only true if you give large/ multiple doses. 

If used in proper dosage, it works great. I have had wines with the aroma slightly muted by reductive sulfurs but not enough to really detect. Add a small dose of reduless and it unmasks the true fruit aromas and end up being wonderful. 

Dose and bench trials are key (just like with most things in wine)

I don’t disagree with the Kmeta with a good stir/splash rack but I would wait until alcoholic fermentation is complete. 

Here is the Scott labs protocol for sulfur aromas in reds:



https://scottlabsltd.com/content/files/Documents/SLL/Fermentation%20Protocols/Sulfuroffaromasreds.pdf


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## winemaker81 (Oct 25, 2021)

Cap Puncher said:


> Again, I agree that reduless works well, but to say that it “bleaches” wine and mutes flavors is only true if you give large/ multiple doses.


I used the minimum recommended dosage and it affected the color. I had another carboy of the same wine to compare against.

Of course, the best way to deal with H2S is to use sufficient nutrient before and during fermentation to avoid it completely!


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## Mario Dinis (Oct 25, 2021)

Had the same problem last year with a Pinot Noir. Solved the problem by splash racking several times. Got lucky.


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## verdot (Oct 25, 2021)

Thanks for the replies. Definitely seems like low oxygen and nutrition at start of fermentation is an issue. I ordered some go-ferm protect evolution for next year and will be more precise with nutrient addition next time around and be more selective with my my grapes. Some bad and broken ones may have made their way into the must. Will be splash racking a bit as you suggested Mario and will just hope it dissipates with time.


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## Juniper Hill (Oct 25, 2021)

I've had good luck with reduless for H2S that didn't clear with other measures. I haven't noticed any muted flavours, but of course compared with rotten eggs just about anything else is gonna be good.


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## Cynewulf (Oct 25, 2021)

Mario Dinis said:


> Had the same problem last year with a Pinot Noir. Solved the problem by splash racking several times. Got lucky.


Same here. I had the issue with a Grenache bucket I was fermenting with some pressed pomace last year. I splash racked once or twice and the H2S smell dissipated over the next month or two and was completely gone when I bottled this year. I didn’t add anything, not even SO2. YMMV, just another reference point.


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## Mario Dinis (Oct 25, 2021)

Cynewulf said:


> Same here. I had the issue with a Grenache bucket I was fermenting with some pressed pomace last year. I splash racked once or twice twice and the H2S smell dissipated over the next month or two and was completely gone when I bottled this year. I didn’t add anything, not even SO2. YMMV, just another reference point.


I also didn't add anything.


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## winemaker81 (Oct 25, 2021)

Treating H2S depends on how early it's caught. If detected before mercaptains start forming, stirring may be enough. In my situation a year ago, that was not the case, so I had to do a more extensive treatment, and months later treated with ascorbic acid to handle the mercaptains.

The moral of the story? Use sufficient nutrient and sniff test the wine daily. I admit that my encounter has made me paranoid. But better paranoid that a carboy of bad wine! 

Note on ascorbic acid -- I use a very light dose as it can made the wine very sharp. It took nearly 2 months for the ascorbic acid to work. Once the H2S is handled, the wine is back to "slow, steady, and patience" as the mantra.


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## verdot (Nov 22, 2021)

An update on this - I followed Cap Punchers suggestion and followed the scottlabs guidelines. The company was also quite helpful over email. I started with noblesse, splash racked as others suggested and later added Reduless. The issue seemed to persist which led me to believe the additives had not done the job. So another splash rack and left to rest for a few weeks. Upon sampling, the foul smell was almost completely gone and the fruit was now showing in the nose. No signs of oxidation. So the wine will likely be saved. Ph was 3.5 and TA 6.7 Thanks to everyone who gave tips.


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## mgarnto (Dec 6, 2021)

Question for everyone, is it possible that people think they smell H2S but it’s actually something else?

Everywhere you look it says “H2S can only be solved by splash racking if you’re lucky or chemicals, but it not treated early there’s no way to fix it”.

Yet, there are plenty of anecdotes where people say it magically fixes itself. Or they tried and failed early on with chemicals but several months down the road it’s fine.

So either H2S isn’t the doomsday people claim, or it frequently gets confused for some other aroma.


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## sour_grapes (Dec 6, 2021)

mgarnto said:


> Question for everyone, is it possible that people think they smell H2S but it’s actually something else?
> 
> Everywhere you look it says “H2S can only be solved by splash racking if you’re lucky or chemicals, but it not treated early there’s no way to fix it”.
> 
> ...



IMHO, the resolution to your last proposition is that H2S is detectable in minute quantities (like ppm). So you have a small amount of H2S, you smell it, but it dissipates to the ppb level where it "just adds complexity."


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## reeflections (Dec 6, 2021)

Question: will splash racking under vacuum help or is the point to introduce oxygen?


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## mainshipfred (Dec 6, 2021)

reeflections said:


> Question: will splash racking under vacuum help or is the point to introduce oxygen?



I have no proof of this though I would think vacuum racking might reduce O2, it definitely reduces CO2.


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## reeflections (Dec 6, 2021)

mainshipfred said:


> I have no proof of this though I would think vacuum racking might reduce O2, it definitely reduces CO2.



So is the point of splash racking for removing the H2S odor to introduce O2?

IOW, it would be better to splash rack via siphoning?


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## mainshipfred (Dec 6, 2021)

reeflections said:


> So is the point of splash racking for removing the H2S odor to introduce O2?
> 
> IOW, it would be better to splash rack via siphoning?



I'm fortunate to have only had an H2S problem one time. I can't remember if I pumped from one vessel to another or splash racked it under a vacuum. I do believe though that the splashing released the hydrogen sulfide and the vacuum sucks it out without introducing O2. There are tons of folks on here that can give a more scientific response and even disprove my theory.


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## reeflections (Dec 6, 2021)

mainshipfred said:


> I'm fortunate to have only had an H2S problem one time. I can't remember if I pumped from one vessel to another or splash racked it under a vacuum. I do believe though that the splashing released the hydrogen sulfide and the vacuum sucks it out without introducing O2. There are tons of folks on here that can give a more scientific response and even disprove my theory.



Yes, I only had it once as well - with Skeeter Pee. I poured it from one open bucket to another and back again. That fixed it but I hated introducing that much O2 after the fermenting was almost done (1.000).


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## sour_grapes (Dec 6, 2021)

Yes, vacuuming should help with H2S.


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## reeflections (Dec 6, 2021)

sour_grapes said:


> Yes, vacuuming should help with H2S.



Thanks!


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## winemaker81 (Dec 7, 2021)

mgarnto said:


> Question for everyone, is it possible that people think they smell H2S but it’s actually something else?


It's possible someone smells sulfite and believes it to be H2S. However, if you smell H2S in any quantity, there's no mistaking the odor.

With H2S there are 3 components: the cause, the H2S itself, and its fallout (mercaptans).

*The cause* is typically low nutrient levels stressing the yeast. If the wine is currently fermenting, add nutrient. To prevent H2S in the future, use a proper nutrient regimen and/or use a yeast that doesn't produce H2S.

*The quick treatment* for H2S is to splash rack and/or stir well. This drives off the H2S -- do it in a well ventilated area. H2S is flammable, although I'm told that there isn't enough in a wine to produce a real danger; that said, even if it didn't reek, I'd still use a well ventilated area.

I run a fan while working with my wines and have 2 windows in my winemaking area that I open, weather permitting.

Also add a double dose of K-meta. Add more sulfur to combat sulfur ? Yup -- H2S and SO2 are completely different compounds. SO2 protects wine by binding to contaminants, which includes H2S.

*The heavy-duty treatment* is to expose the wine to copper. Although the "old time" remedy was to rack over new pennies, this is frowned upon because copper is a poison and there is no way to determine how much copper is introduced into the wine.

Instead use a product such as Reduless, in which the dose is calculated. Then fine the wine to help remove residue.

*Mercaptans* can be formed with the H2S interacting with alcohol, producing off flavors and smells that do not go away on their own. A treatment for mercaptans is ascorbic acid, but go VERY light on it, as very little makes the wine acidic, sharp tasting. Also, IME it takes months to work -- do not add ascorbic acid, taste the wine a week later, and then add more.



mgarnto said:


> Yet, there are plenty of anecdotes where people say it magically fixes itself. Or they tried and failed early on with chemicals but several months down the road it’s fine.


My guess is that H2S didn't "magically" fix itself. Either the person misinterpreted the smell, or they caught it early and something they did (add nutrient, add K-meta, stir, etc.) corrected the problem.

Regarding the wine being fine several months down the road? IME the treatment for mercaptans was not quick -- it took months, so the wine was fixed by the treatment.


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## Rice_Guy (Dec 7, 2021)

@mgarnto H2S is an extremely reactive chemical, ie it will not stay in the wine as H2S gas. YES it will magically go away producing less volatile chemicals classed as mercaptans. 

The danger in all this is that our ability to detect the desirable parts per billion fruity aromatics is covered over by the mercaptans so, ,,, you can produce a perfectly drinkable wine, ,,, which has meaty notes and might complement a dark chocolate candy, or as one of the gals in the vinters club says “fried chicken” flavor wines.


Rice_Guy said:


> This post evaluates ten webinars,, “BOOK REVIEWs” related to air exposure (AKA redox potential) while making wine. - - - - _- - - - - - - - - - - - - - - - - - - ->
> This video is about half chemistry and half treatments which can be tried to change reductive flavors. Ie sulfides / threshold detection level/ latent sulfur changes (in bottle), YAN prevents yeast from forming sulfide compounds, it is easier to flush SO2 out early with yeast CO2._
> * Managing ‘reductive’ aromas in wines; Speaker: Dr Marlize Bekker (The Australian Wine Research Institute) Webinar recorded: 7 November 2019 Additional resources: https://www.awri.com.au/industry_supp... Volatile sulfur compounds (VSCs) are known to cause ‘reductive’ aromas in wine, commonly described as ‘rotten egg’ (hydrogen sulfide), ‘putrefaction’ (methanethiol) and ‘rubber’ (ethanethiol). These compounds play important roles in determining wine aroma, consumer preference and the perception of wine quality. Therefore, the management of VSC concentrations in wines, whether from fermentation or 'other' origins, is an important consideration for winemakers. The main techniques used for VSC removal are oxidative handling and/or copper fining; however, the effectiveness of these treatments may be temporary, as the compounds can often reappear post-bottling when reductive conditions are re-established. This presentation will summarise the latest research on ‘reductive’ aroma formation in wines and discuss practical remediation strategies to manage these characters, 58 minutes (30 min. was Q&A)
> - - - - - - - - - - - - - -


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## winemaker81 (Dec 7, 2021)

Rice_Guy said:


> @mgarnto H2S is an extremely reactive chemical, ie it will not stay in the wine as H2S gas. _YES it will magically go away producing less volatile chemicals classed as mercaptans._


Thanks for pointing this out. In my research on the topic, I've not read that the H2S will dissipate on its own, although it makes sense that it does so.

Essentially, the symptom (H2S stench) goes away, but is replaced by a permanent-unless-treated problem (mercaptans).

I learn something new every week on this forum.


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