Smell of rotten vegetables - fermenting Hefeweizen

[Bayern1987]

I pitched some harvested wyeast 3068 a couple of days ago to my Hefeweizen (65% wheat, 20% pilsner, 15% munich)

Usually everything goes well and I get tthe odd smell of sulphur however this time when I opened the door to the spare room all I could smell was a rotten vegetable / bin like smell. The harvested yeast did smell funky when I took it out the fridge before I made the starter however the next day smelt fine... could it be this and is my beer infected? Or could it be DMS from the pilsner malt and will this settle out with more fermentation time?
Basically do you think my beer is definitely ruined / infected or will it maybe settle out and off flavours disappear over time?

Thanks

 

[duncan.brown]

I wouldn’t worry. That strain often kicks off a sulphur smell. Wyeast mentions this in the notes:

https://wyeastlab.com/yeast-strain/weihenstephan-wheat
It should dissipate with time.

One of my favorite yeasts (2308 Munich Lager) is a real stinker. The fresh yeast smells “off” to me and it produces a lot of nasty suplhorous odors during fermentation. The finished beer tastes great, though.

 

[Bayern1987]

I wouldn’t worry. That strain often kicks off a sulphur smell. Wyeast mentions this in the notes:

https://wyeastlab.com/yeast-strain/weihenstephan-wheat
It should dissipate with time.

One of my favorite yeasts (2308 Munich Lager) is a real stinker. The fresh yeast smells “off” to me and it produces a lot of nasty suplhorous odors during fermentation. The finished beer tastes great, though.

Thanks Duncan

It was just because I never had it before with the same ingredients and strain of yeast I have been harvesting... I top cropped it off the last batch (usually taken it from the bottom yeast cake) so I wondered if this had an effect or if it picked up an infection this time...

I will give it time and keep the faith cheers

 

[duncan.brown]

If you top-cropped a nice, active krausen, it’s probably extra healthy and so kicking up real a stink! I had a batch of helles kick off enough hydrogen sulphide (rotten egg gas) to discolor the brass fittings on a regulator that was in the same keezer.

At least with Hefeweizen you won’t have to wait long to taste it. Hope it turns out well!

 

[RPh_Guy]

It's sounds like the culture is producing a variety of volatile sulfur compounds (VSCs). It's not possible to know whether it's contaminated or not just from the presence of VSCs.

VSCs (hydrogen sulfide and a variety of thiols, AKA mercaptans) will oxide once fermentation completes and your beer is exposed to oxygen. The oxidation process removes the offensive flavor in most cases (in beer, wine is different).

https://***************.com/wiki/Hydrogen_sulfide
Good luck!

 

[Bayern1987]

If you top-cropped a nice, active krausen, it’s probably extra healthy and so kicking up real a stink! I had a batch of helles kick off enough hydrogen sulphide (rotten egg gas) to discolor the brass fittings on a regulator that was in the same keezer.

At least with Hefeweizen you won’t have to wait long to taste it. Hope it turns out well!

I hope you are right Duncan!

Even 5x more foul smelling than an original yeast 3068 smack pack?
Because this is really stinking it is so horrible my Mrs even commented on it... I am just hoping that the yeast is super healthy and making great Hefeweizen

 

[RPh_Guy]

H2S and VSCs are generally a sign that the yeast is not healthy, see the link above.

 

[Bayern1987]

It's sounds like the culture is producing a variety of volatile sulfur compounds (VSCs). It's not possible to know whether it's contaminated or not just from the presence of VSCs.

VSCs (hydrogen sulfide and a variety of thiols, AKA mercaptans) will oxide once fermentation completes and your beer is exposed to oxygen. The oxidation process removes the offensive flavor in most cases (in beer, wine is different).

https://***************.com/wiki/Hydrogen_sulfide
Good luck!

Thank you for information! What do you think the reason for the smell if this time? Could it be due to top cropping rather than bottom harvesting? Or might it be an infection after several generations of harvesting? And do you really think the smell will disappear... I tried sniffing the airlock there and burnt my nose

 

[Bayern1987]

H2S and VSCs are generally a sign that the yeast is not healthy, see the link above.

Thank you!

 

[duncan.brown]

H2S and VSCs are generally a sign that the yeast is not healthy, see the link above.

I'm not convinced that H2S is a sign of unhealthy yeast. Kunze Sec. 4.1.3.5 discusses sulphur compounds. H2S is produced as a by-product of fermentation by a number of strains during healthy fermentation, but it is highly volatile and is mostly desorbed by the ascending carbon dioxide during fermentation. Unhealthy yeast can over-produce, but it's not necessarily a sign of poor yeast health.

Mercaptans can damage beer aroma, however. They are oxidized to disulphides, which are less pungent. I interpreted the OP's post to be the rotten egg/garbage smell of H2S, but if a lot of mercaptans are coming off, that could be an issue.

Time will tell!

 

[Bayern1987]

I'm not convinced that H2S is a sign of unhealthy yeast. Kunze Sec. 4.1.3.5 discusses sulphur compounds. H2S is produced as a by-product of fermentation by a number of strains during healthy fermentation, but it is highly volatile and is mostly desorbed by the ascending carbon dioxide during fermentation. Unhealthy yeast can over-produce, but it's not necessarily a sign of poor yeast health.

Mercaptans can damage beer aroma, however. They are oxidized to disulphides, which are less pungent. I interpreted the OP's post to be the rotten egg/garbage smell of H2S, but if a lot of mercaptans are coming off, that could be an issue.

Time will tell!

Do you think perhaps opening the fermenter for a few minutes to allow oxidation and let off some of the foul smelling aroma may be a good idea? I have had a sulphur smell before however never as pungent and strong as this... was it maybe due to an infection when harvesting the yeast or stressing the yeast out when washing. Etc. As I may not have given the water enough time to cool when top cropping (the water I collected it with in a Mason jar) so perhaps some autolysis? And still yet... will this settle out and maybe even create a better beer in the end?

 

[RPh_Guy]

Unhealthy yeast can over-produce, but it's not necessarily a sign of poor yeast health.

Over-production of H2S results from nutrient depletion, particularly if it occurs early in fermentation. Only a small amount can be "normal", although it can usually be prevented entirely.

I discuss all of this is much greater detail than what's in Kunze in my article linked above.

I interpreted the OP's post to be the rotten egg/garbage smell of H2S, but if a lot of mercaptans are coming off, that could be an issue.

He said "rotten vegetable", which I would assumed to be most likely mercaptans. To H2S smells nothing like vegetables and is never described as smelling like vegetables. On the other hand, methanethiol or ethanethiol both smell like rotting vegetables. IMO the odor being present in the culture before pitching rules out excessive DMS. It could certainly be a contamination, but there's no easy way to verify that.

Cheers

 

[duncan.brown]

@RPh_Guy I think we agree, it just depends on what your definition of "over production" is. A very faint whiff of sulphide in a helles is desirable to me, but would be an off-flavor in an American lager.

The sections in Practical Brewer and Stewart's Handbook of Brewing agree with Kunze that some H2S production is normal, but over-production comes from: choice of yeast strain (looking at you, 2308!), poor yeast growth, lack of wort nutrients, lack of wort oxygenation, slow fermentation, retention of fermentation gas, and bacterial contamination of the yeast. This agrees with the page you linked, with the exception that they don't say to aim for zero H2S during fermentation, but that is likely style dependent. I looked at the references and most are from the wine world where any H2S is a definite no. I found this review, which might be helpful to @Bayern1987:

https://www.mdpi.com/2311-5637/4/2/23/htm
Table 6 in this paper might help you identify what's being produced.

But, yeah, if @Bayern1987's SO can smell it throughout the house, I don't think I'd argue that's not over production! And I agree that rotten vegetable is more likely to be mercaptans than hydrogen sulphide. The latter has an unmistakable bad-egg smell.

Practical Brewer says that sulfide compounds are reduced 50% by 30 days of aging, but OTOH, hefeweizen should be drunk fresh, and if you're way over the flavor threshold it won't help anyway. If the smell persists into the finished beer, you could try scrubbing by bubbling CO2 though to remove them. You could also be a bit less picky about cold-side oxygenation when you package, which would oxidize them, and drink the beer before it stales.

Let us know how it turns out.

 

[Bayern1987]

Thanks for advice everyone!

It is definitely more like rotten vegetables and blew me away when I inspected the airlock... I usually get a hit of sulphur from this strain and this time it was distinctly different... however this morning the smell does not seem to be so bad as yesterday...

I think it is something to do with the yeast... first time I top cropped instead of bottom harvested it and this is like the 5the or 6th generation of using it. I am hoping it is not contaminated and perhaps with the stress and everything going on, if I manage to get rid of the metacarptans and odour it may even produce some interesting and welcoming smells and tastes... you never know

Another thing... when harvesting the yeast I may have not let the water cool enough before pouring it into the Mason jar... or not been sanitary enough do perhaps some infection but I hope not... it is always a learning curve

I will let you all know how it turns out!

Any more advice is welcome

Thanks

 

[duncan.brown]

Another thing... when harvesting the yeast I may have not let the water cool enough before pouring it into the Mason jar... or not been sanitary enough do perhaps some infection but I hope not... it is always a learning curve

The best storage medium for yeast is beer, not water. The low pH and alcohol in beer helps prevent infections when you're storing the yeast in the fridge between batches. If you top crop, just scoop up enough krausen with a sanitized jar, as there's plenty of liquid in there and let it settle out. Just be careful not to expose the beer to the air when you're cropping the yeast.

Anything that touches my stored yeast gets at least a 10 min soak in iodophor before it's used. I always go by Charlie Bamforth's four rules for home brewers: 1. Sanitation, 2. Sanitation, 3. Sanitation, 4. Have an understanding spouse/partner.

 

[Vale71]

The best storage medium for yeast is beer, not water. The low pH and alcohol in beer helps prevent infections when you're storing the yeast in the fridge between batches. If you top crop, just scoop up enough krausen with a sanitized jar, as there's plenty of liquid in there and let it settle out. Just be careful not to expose the beer to the air when you're cropping the yeast.

This is actually a misconception. Beer is an excellent breeding ground for microorganisms that can thrive in that type of environment and those are the ones we absolutely want to avoid because that means that they can later infect and ruin our beer. On the other hand nothing can grow in pure water as its nutritional value is basically zero, so the best way to avoid infections when storing yeast is to thoroughly wash it with sterile water. For long term storage an isotonic saline solution would of course be ideal as it avoids any osmotic stress.

 

[duncan.brown]

Getting off topic, but storing yeast in beer vs water seems to be a subject of somewhat vigorous debate in the home-brewing community

I go by Chris White's advice which suggests storing under beer. For better bacterial control, you can also add phosphoric acid to drop the pH to 2.3 to 2.5 and/or add some hop extract. For longer-term storage it might be a good idea to add sterile water which helps keep the yeast glycogen higher for longer as it dilutes the beer in the yeast slurry down and slows down the metabolism of the yeast. But that's more for direct pitch, if you make a starter you can always build it back up. This is all relatively short term, though. I'd use slants for real long-term storage.

The water you get out of your tap is not free of dissolved organic carbon and even if you boil it, stuff can still grow in it if it gets contaminated. If there are beer-spoilage organisms in the beer you are harvesting the yeast from, I would expect that traces of them remain remain in the washed yeast. I don't see how washing could separate bacteria and yeast, but it's not a technique I've used so maybe someone who's done it can explain. I'm also not sure even sterile, distilled water would stay free of dissolved organic carbon that spoilage organisms can use once you add the yeast to it.

There's some a nice write up and pictures of the pro's SOP here. This seems to match what I've read from Chris White and they recommend storing under beer, acidifying, adding some hop extract, and diluting with some water.

 

[Vale71]

Beer spoilage organisms will multiply in beer if left to their own devices long enough, they will not be able to do so in plain water or saline and that is a big difference. Exotic organisms that can live from the minerals in tap water will not spoil your beer so they're not really a concern.
If you're dropping the PH of your storing solution to 2.5 then that's and acid wash and you have to use that yeast rather quickly. If you store it like that you'll destroy it sooner rather than later.
As for how the pros do it they will never be storing yeast for weeks or months so their SOPs are tailored to that scenario.

 

[duncan.brown]

I agree that beer is a good medium for the propagation of beer-spoilage organisms. There's a nice chart in Bokulich and Bamforth (2013) that shows the phylogeny of primary beer-spoilage bacteria:

https://mmbr.asm.org/content/mmbr/77/2/157/F5.large.jpg?width=800&height=600&carousel=1
A good chunk of these are Lactobacillus sp. which has many strains that salt tolerant, see El-Gendy et al. (1983) or Battock and Azam-Ali (1998). I guess my SOP is closer to the pros that I don't store yeast for long periods of time (usually a week between brews) and I worry that the sanitation risk from washing is greater than the risk from just putting the yeast and beer slurry directly in a media bottle, slightly acidifying, and storing that.

The moral here is probably: if your beer is spoiled, don't propagate the yeast from it! If it's clean beer, I suspect either method will work fine on the home-brew scale as long as you remember Bamforth's rules: Sanitation, Sanitation, Sanitation, ...

Bonus points to @Bayern1987 if he can plate the finished beer and tell us what is in it!

 

[Bayern1987]

I agree that beer is a good medium for the propagation of beer-spoilage organisms. There's a nice chart in Bokulich and Bamforth (2013) that shows the phylogeny of primary beer-spoilage bacteria:

https://mmbr.asm.org/content/mmbr/77/2/157/F5.large.jpg?width=800&height=600&carousel=1
A good chunk of these are Lactobacillus sp. which has many strains that salt tolerant, see El-Gendy et al. (1983) or Battock and Azam-Ali (1998). I guess my SOP is closer to the pros that I don't store yeast for long periods of time (usually a week between brews) and I worry that the sanitation risk from washing is greater than the risk from just putting the yeast and beer slurry directly in a media bottle, slightly acidifying, and storing that.

The moral here is probably: if your beer is spoiled, don't propagate the yeast from it! If it's clean beer, I suspect either method will work fine on the home-brew scale as long as you remember Bamforth's rules: Sanitation, Sanitation, Sanitation, ...

Bonus points to @Bayern1987 if he can plate the finished beer and tell us what is in it!

It has calmed down tonight Duncan... the smell seems to have faded... still have a good while to go before bottling and it will be interesting to see what the aroma is like then... will let it oxidize without too much thought during bottling.... and then anticipate the final result! Going to buy a fresh pack of wyeast 3068 for my future batches however I have another batch of Hefe which is nearly finished fermenting (and no obvious problems with that one) so going to try brewing up a dunkelweizen this week and pitch straight onto the yeast cake for a change

Keep the thread alive and I will let you guys know how this turns out.

Thank you

 

[duncan.brown]

I did a bit more research on the best storage for yeast, and this is the most up-to-date information I can find:

In order to protect the yeast culture’s quality, it should be stored under approximately 6 in. of beer (sterile water has been employed in the past, but its use is not currently favored).

"Stresses Imposed on Yeast During Brewing Fermentations and Their Effect on Cellular Activity," Graham G. Stewart, International Centre for Brewing and Distilling, Heriot-Watt University, Master Brewers Association of the Americas Technical Quarterly, Volume 57, No 1 (2020) pp.1–8.