Sulphur smell

[Dutto]

I'm using Alcotec Turbo yeast 23%. Have been for two years, all goes well. But this time I'm getting a sulphur smell, like a dried out car battery being charged, or rotten eggs. I've done a bit of googling and it says some yeast strains can emit this smell, but I've not changed the yeast, the only thing that's different is the brand of sugar I'm using (dextrose monohydrate). I'm happy just to wait and see what it tastes like, since it seems to be bubbling away so it's not dead.

But my real question is - where on earth does the sulphur come from? That element isn't present in the sugar, and I'm not doing alchemy, so what is the source?

During accident enquiries I always waited for "The only that I did differently was ..." :thumb:

Because this was a phrase that regularly preceded the reason why the accident occurred.

In this case, the yeast may be producing hydrogen sulphide (H2S) in VERY low quantities due to the change of sugar.

H2S is a colourless, highly toxic gas that smells like rotten eggs in concentrations as low as 5 parts per million.

In concentrations above 150ppm H2S kills the sense of smell and in concentrations above 600ppm a single inhalation will render the average person unconscious and kill them.

With regard to "Where does it come from?":

o The Hydrogen comes from the breakdown of the H2O (i.e. water).

o A common source of Sulphur in brewing is the gypsum (CaSO4) used in water treatment.

The good news is that it will probably disperse when the mash is de-gassed at the end of fermentation and should therefore not affect the finished product. :thumb:

 

[hucker]

I find it worrying that 5 ppm is when you start smelling it, but 150 ppm you can't smell it, then 600 ppm you die with one breath. I wonder how much it would have to build up to kill you breathing it all day/night?

I was also thinking that if the yeast is processing the sulphur, the yeast might not be very healthy and make the alcohol as it should.

 

[BeerCat]

Some yeasts are known to produce an eggy smell. I am brewing a one-off lager at present using a lager yeast and the smell is definitely more eggy than when I brew my normal beers using ale yeast.

Amen. My last Lager stunk the garage out with an eggy fart smell.

 

[Robin54]

Amen. My last Lager stunk the garage out with an eggy fart smell.

I find that as well, after Ive drunk the stuff. What a coincidence.

 

[hucker]

Ash long ash it makesh me shpeak funny, it'sh good enough.

 

[terrym]

With regard to "Where does it come from?":

o The Hydrogen comes from the breakdown of the H2O (i.e. water).

o A common source of Sulphur in brewing is the gypsum (CaSO4) used in water treatment.

Dutto
I cannot really believe that you believe that to be a fact. April 1st has now gone.
Yeast will not be able to convert the hydrogen atom in water and the sulphur atom in calcium sulphate into molecular H2S. It's impossible. Its like making H2S from car battery acid, H2SO4, that's impossible too. However if anyone can provide me with a scientific factual reference that says its possible then I'll admit I'm wrong. There's the challenge
As far as the eggy smell is concerned it could be any one of many things. Yes H2S smells of eggy farts. But then many organic sulphur compounds have strong odours. That's why some of them are used as odorants in natural gas so that gas leaks are detectable.
H2S and many organic sulphur compounds are odour detectable down to ppb levels (Wiki thingy quotes 0.47ppb for H2S), so the human nose is acutely aware of any such smells in tiny tiny concentrations.
And so any suggestion that the offgas from a yeast fermentation is sulphur toxic is absurd. I suggest that you are more likely to die from the effects of sitting in a room of egg curry fart gas, and we are all still alive aren't we?

 

[Robin54]

Dutto
I cannot really believe that you believe that to be a fact. April 1st has now gone.
Yeast will not be able to convert the hydrogen atom in water and the sulphur atom in calcium sulphate into molecular H2S. It's impossible. Its like making H2S from car battery acid, H2SO4, that's impossible too. However if anyone can provide me with a scientific factual reference that says its possible then I'll admit I'm wrong. There's the challenge
As far as the eggy smell is concerned it could be any one of many things. Yes H2S smells of eggy farts. But then many organic sulphur compounds have strong odours. That's why some of them are used as odorants in natural gas so that gas leaks are detectable.
H2S and many organic sulphur compounds are odour detectable down to ppb levels (Wiki thingy quotes 0.47ppb for H2S), so the human nose is acutely aware of any such smells in tiny tiny concentrations.
And so any suggestion that the offgas from a yeast fermentation is sulphur toxic is absurd. I suggest that you are more likely to die from the effects of sitting in a room of egg curry fart gas, and we are all still alive aren't we?

When my old cat 'dropped one" it was pretty toxic:mrgreen:

 

[hucker]

Farts are strong enough to prevent your brain from continuing it's normal functions. The only thing you can think of is getting out of the room.

No scientist has ever worked out how you can tolerate your own farts. Surely they're the same chemicals?

 

[Dutto]

...

Yeast will not be able to convert the hydrogen atom in water and the sulphur atom in calcium sulphate into molecular H2S. It's impossible. .......

Sorry, but I have to disagree. It isn't "impossible" for yeast to produce H2S.

If you take the trouble to Google "Yeast and Hydrogen Sulphide" you will get 294,000 results, the first of which states in sentence one:

"Formation of hydrogen sulfide (H2S) is a major problem in winemaking
because, if untreated, it can leave a wine with an undesirable
rotten-egg sensory characteristic. "​

Reference: https://www.practicalwinery.com/novdec05/novdec05p26.htm

You may apologise any time you want! :thumb: :thumb:

PS

Gypsum (CaSO4) must be a fairly unstable molecule, otherwise it wouldn't be used to condition water would it? :whistle:

 

[terrym]

Sorry, but I have to disagree. It isn't "impossible" for yeast to produce H2S.

If you take the trouble to Google "Yeast and Hydrogen Sulphide" you will get 294,000 results, the first of which states in sentence one:

"Formation of hydrogen sulfide (H2S) is a major problem in winemaking
because, if untreated, it can leave a wine with an undesirable
rotten-egg sensory characteristic. "​

Reference: https://www.practicalwinery.com/novdec05/novdec05p26.htm

You may apologise any time you want! :thumb: :thumb:

PS

Gypsum (CaSO4) must be a fairly unstable molecule, otherwise it wouldn't be used to condition water would it? :whistle:

You have misread what I said which was...
Yeast will not be able to convert the hydrogen atom in water and the sulphur atom in calcium sulphate into molecular H2S. It's impossible.
Further I said
And so any suggestion that the offgas from a yeast fermentation is sulphur toxic is absurd. I suggest that you are more likely to die from the effects of sitting in a room of egg curry fart gas, and we are all still alive aren't we

And so I didn't say it was impossible for yeast to generate H2S or any organic sulphur compounds during fermentation. Anywhere. Which is what I intended. So I still need proof that yeast will act on CaSO4 and water to produce H2S. Then I'll say I was wrong

And my belief is that gypsum is a very chemically stable. It's been in the ground for thousands of years and is mined as, well, gypsum.

 

[Dutto]

You have misread what I said which was.....


And my belief is that gypsum is a very chemically stable. It's been in the ground for thousands of years and is mined as, well, gypsum.

That's rich!

My original post stated ...

"In this case, the yeast MAY be producing hydrogen sulphide (H2S) ..."​

... and that statement still stands as supported by all the Google hits I quoted. (I even highlighted the word "may" in the original Post.)

The Post carried on with ...

"The Hydrogen comes from the breakdown of the H2O (i.e. water)."​

... and that statement still stands in that H2O is broken down during the brewing process.

The brewing process itself breaks down the water molecule to produce ethanol. The formula for the production of ethanol from sugar finishes as ...

C6H12O6 > 2 C2H5OH + 2 CO2​

... but there is an intermediate stage where the enzyme Invertase gets involved as per ...

C12H22O11 + H2O + invertase > 2 C6H12O6​

My original Post went on ...

"A common source of Sulphur in brewing is the gypsum (CaSO4) used in water treatment."​

With regard to the sources of sulphur, are you saying that:
A) Gypsum isn't used in water treatment? or
B) There is no sulphur in gypsum?

The reason I ask is that gypsum is not "very chemically stable" as you state. In the 1970's gypsum was used for the commercial production of sulphuric acid as per ...

"Upon being mixed with shale or marl, and roasted, the sulphate liberates
sulfur dioxide gas, a precursor in sulfuric acid production ..."​

Finally, I DID NOT suggest that "the offgas from a yeast fermentation is sulphur toxic". From explaining that the smell of rotten eggs MAY be coming from the production of H2S I went on to explain (accurately) the properties of H2S after pointing out ...

"In this case, the yeast may be producing hydrogen sulphide (H2S)
in VERY low quantities due to the change of sugar."​

The VERY was already in capitals and highlighted. I suppose I could have put in "VERY, VERY, VERY small quantities" but I pre-suppose that the people on this Forum are intelligent.

Over to you, but I am backing out at this stage because I don't have anything more to add. :thumb: :thumb:

References:

https://en.wikipedia.org/wiki/Ethanol_fermentation
https://en.wikipedia.org/wiki/Calcium_sulfate

 

[hucker]

Is gypsum that horrid stuff they make plasterboard out of? (plasterboard being the daftest invention ever).

 

[Dutto]

Is gypsum that horrid stuff they make plasterboard out of? (plasterboard being the daftest invention ever).

Yes! Also plaster casts! :thumb:

 

[hucker]

I don't put gypsum into my brewing, so unless it's included with the yeast/carbon/nutrient pack, the sulphur must be in the sugar.

 

[Chippy_Tea]

H2S Hydrogen Sulfide

by Alberta Rager

Hydrogen Sulphide that Rotten Egg Smell

A rotten egg smell is due to the presence of hydrogen sulphide (H2S) gas. Although the production of hydrogen sulphide is a natural by-product of yeast metabolism, albeit in very small quantities, perceptible levels should not be detectable in the finished product.

Causes of elevated levels of Hydrogen Sulphide include stressed yeast from low available nitrogen during fermentation and/or lack of oxygen, grapes that have been over-treated with sulphur-based products, leaving the wine (or beer) on the lees (sediment) too long, or yeast choice.

Yeast under nutritional stress during primary fermentation will produce perceptible levels of H2S. Yeast requires nitrogen and oxygen to conduct a healthy fermentation. Higher gravity musts or worts create more challenging fermentation conditions for the yeast. Beers with an original gravity above 1.070 require additional yeast nutrient and oxygen as well as a higher yeast cell count when inoculated. This is also true for a must with a starting gravity of 1.100 or higher. The addition of diammonium phosphate in the form of Yeast Nutrient, Yeast Energizer or Fermaid K to all wine, mead and cider must is recommended as well as high gravity worts. This supplies the yeast with ammonia which gives the yeast a nitrogen source. Do not add diammonium phosphate after the gravity reaches 1.015-1.020 as the yeast can no longer take it up due to alcohol toxicity.

Although all yeast produces hydrogen sulphide during fermentation, some strains like Montrachet and lager yeast are predisposed to produce higher levels. Others strains like Lalvin 71B 1122 are low sulphur producers.

It is important to make sure there is enough dissolved oxygen in wine, mead, cider and beer. With insufficient oxygen yeast will become stressed producing off flavors and odors and possibly not completing fermentation before flocculating.

During primary fermentation, the top half of wine, mead and cider should be stirred daily to volatize the sulphur. Wine and cider should be racked from the primary off the sediment (lees) when the gravity reaches 1.010-1.020 not allowing the lees to form a deep compact layer because free sulphur becomes trapped in the lees of new wines and is readily reduced to hydrogen sulphide and a host of other sulphur based compounds. Lees lose their ability to reduce sulfur over time, so during the next month or two, weekly stirring is recommended.

Should you detect hydrogen sulphide in a very young wine that is still on the primary fermentation lees, rack off the lees vigorously splashing. If you’ve already done the initial racking and notice the hydrogen sulphide smell, rack from carboy to carboy a couple time aerating the must. The introduction of oxygen at this time is contrary to most practices, but the formation of hydrogen sulphide is a reductive process. Introduction of oxygen at this point shifts the reaction away from the formation of reductive compounds.

Catching the production of H2S early is fairly easy to reduce. Unfortunately, once the wine is more than a few weeks old, it is much more difficult to get rid of.

http://www.bacchus-barleycorn.com/catalog/article_info.php?articles_id=120

 

[Tau]

There's other trace molecules in water that may contain sulphur, the free Hydrogen radicals released in the breakdown of sugar bonds rather than from the water molecule iself, would more likely bond with any sulphur in other molecules disolved in the water, although saying that the H radicals could be released from water when C atoms are set free from the sugar when fermented and bond with the o2 to form co2. Chalky or slight traces of metallic compounds in the water could well have sulphur with or without gypsum treatment. Free H radicals are highly reactive and would break some of the existing elemental bonds in existing sulphur compounds and form the h2s gas. Also probably present in the nutrient you use, just that the yeast usually combines it into other compounds, when stressed it reverts to producing h2s rather than into cell production. Also the yeast has sulphur in naturally.

Although you might have a bacterial infection, many produce h2s.

 

[hucker]

I've just realised what else I did differently. The yeast instructions say to use 40C water. In the past I've always filled the container with water from the cold tap, then taken a kettlefull away at a time, boiled it, and put it back in, until I reach 40C. This time I heated the whole lot to 40C using an electric shower. Different amount of dissolved air? Not enough nitrogen or oxygen in it from the air? The yeast instructions don't say you have to make sure air is dissolved.

 

[Tau]

I've just realised what else I did differently. The yeast instructions say to use 40C water. In the past I've always filled the container with water from the cold tap, then taken a kettlefull away at a time, boiled it, and put it back in, until I reach 40C. This time I heated the whole lot to 40C using an electric shower. Different amount of dissolved air? Not enough nitrogen or oxygen in it from the air? The yeast instructions don't say you have to make sure air is dissolved.

There's tace sulphurous gases in the air and probably the metal in your shower. Plus shower not a sanitary source of water, so a bacterial infection may have got into your brew.

 

[Dutto]

I don't put gypsum into my brewing, so unless it's included with the yeast/carbon/nutrient pack, the sulphur must be in the sugar.

Some of the Alcotech Yeast Nutrients contain Zinc Sulphate as indicated by their SMDS here where it is listed as a "Hazardous Ingredient".

https://www.abvickers.com/yeastlife-extra/

However, Alcotec also take great pains to explain that yeast nutrients are designed to prevent ...

"Problems associated with reduced vigour include slow or sticking
fermentation, off-flavours associated with sulphur containing compounds,
slow diacetyl reduction, and autolysis."​

... so I'll revert to my original Post. i.e.

The good news is that it will probably disperse when the mash is de-gassed
at the end of fermentation and should therefore not affect the finished product.​

 

[hucker]

Some of the Alcotech Yeast Nutrients contain Zinc Sulphate as indicated by their SMDS here where it is listed as a "Hazardous Ingredient".

https://www.abvickers.com/yeastlife-extra/

However, Alcotec also take great pains to explain that yeast nutrients are designed to prevent ...

"Problems associated with reduced vigour include slow or sticking
fermentation, off-flavours associated with sulphur containing compounds,
slow diacetyl reduction, and autolysis."​

... so I'll revert to my original Post. i.e.

The good news is that it will probably disperse when the mash is de-gassed
at the end of fermentation and should therefore not affect the finished product.​

That's good to hear. It's certainly fizzing away in the normal manner, and the sulphur smell is disappearing. In it's place is the usual smell of alcohol and yeast.

There's tace sulphurous gases in the air and probably the metal in your shower. Plus shower not a sanitary source of water, so a bacterial infection may have got into your brew.

Not sure why a shower would be less sanitary than a kitchen tap. They're both fed from mains water - some people have showers running off a cold water tank for some strange reason, that wouldn't be a good idea. Doesn't make sense at all to me, you get less pressure that way.