Fast USW-6 fermentation sulphur smell

[PeatyKeats]

Looking to make a 100% peat single malt to age in a bourbon barrel.

Mashed 25 gallons, cooled to pitching temp (63°F), and pitched 58 g of USW-6 in to a 55 gallon plastic drum. Put the top on with 2 airlocks.

The wort, which had an OG of 1.061, took off. The temp rose 20° in 30 hours, and the SG was cut in half in the same time.
I checked everything this morning, almost 48 hrs later, and the SG is at 1.01. I’ve read that USW-6 works very fast and the temperature range is between 68°-90°. It smells of sulphur which is a bit disconcerting. Not vomit, just sulphur.
Should I have concerns? Please feel free to share any thoughts?

[Ben]

That yeast is supposed to be low sulfur, what was your initial pitching temp? 20° could mean you are quite hot, yeast tend to produce different esters at different temps and you may have just got it too hot. The sulfur smell could also be translation of some of the peat character by your brainbox. I would give the yeast a couple days, or even weeks to clean up after themselves and see if it fades off a bit. Copper in your vapor path should take care of anything that remains.

[PeatyKeats]

That yeast is supposed to be low sulfur, what was your initial pitching temp? 20° could mean you are quite hot, yeast tend to produce different esters at different temps and you may have just got it too hot. The sulfur smell could also be translation of some of the peat character by your brainbox. I would give the yeast a couple days, or even weeks to clean up after themselves and see if it fades off a bit. Copper in your vapor path should take care of anything that remains.

Initial pitching temp was around 65°. I’ve read that USW-6 works fast, and the temperature rise quickly. I normally use US-05 which has an ideal temp of 65-68°. I’ve also read that copper will help take out sulphur notes during distillation, so it’s good to get that comment as a reminder. I’m just curious how strong would a sulphur odor need to be in a fermentation to become a concern.
Thanks.

[Ben]

Depends on the ferment conditions and the yeast used. A lot of Lager yeasts and wine yeasts throw a ton of sulfurs, you use temp and the non-sugar conversion processes of the yeast to clean it up. All yeasts throw some, It is only a problem if you can't get it out of your finished spirit. I really think time is your ally on this, if you can delay the run a bit it should fade on its own.

[Demy]

Agree with the others, sulfur depends on the types strain but also on the fermentation conditions and on what ferments, it is generally not very present in cereal ferments except in the case of lager yeasts. Leaving a couple of days to rest is my best suggestion, and .. yes the copper helps.

[PeatyKeats]

Agree with the others, sulfur depends on the types strain but also on the fermentation conditions and on what ferments, it is generally not very present in cereal ferments except in the case of lager yeasts. Leaving a couple of days to rest is my best suggestion, and .. yes the copper helps.

Thanks. Although my 13 g boiler is SS, my column and condenser are all copper, so I hope that will help in removing unwanted odors. I’ve also read that sulfur is quite often burnt along with peat to keep peated malt from developing nitrosamines. I wonder if that is something to consider as my mash bill is 100% peat malt.
As I posted above, USW-6 has a fermentation range of 68°-89°, and my fermentation, which began at 65°, didn’t go above 86°.

None of my previous fermentations, in which I’ve regularly used 50% peat malt, have had this strong of sulphur odor before.
We’ll see what happens.

[Ben]

Please follow up after you get it through the still, I am interested to hear your impressions on the distillate.

[PeatyKeats]

Please follow up after you get it through the still, I am interested to hear your impressions on the distillate.

Will do. The wort fermented out to 1.00 in 48 hrs. I’m letting it clear for a few days, and plan to do stripping runs this weekend. The smell of sulphur has subsided which I hope to be a good sign.

[StillerBoy]

The wort fermented out to 1.00 in 48 hrs. I’m letting it clear for a few days,

To assist in clearing the mash, give it a good degassing stir, as this action will remove the C02 which has a tendency to hold back the cleaning action, then let sit for a day or before racking it off it trub/grain bed..

Mars