K97 dried yeast producing sulphur aroma

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ziggy13

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I've been using the K97 strain of dried German ale yeast to make a Kolsch, and the past few batches have had a sulphur aroma that doesn't seem to go away. Does anyone have any experience with this? What could the possible reasons for the sulphur aroma be? It doesn't seem to produce much flavor wise, but it's definitely there on the nose. Any ideas?
 

giraffe

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I havent used K97 in particular, but kolsch yeasts will produce sulfur if stressed. Not enough O2, underpitching, too cold fermentation temp, etc.

Degassing the keg and then adding more co2 through the out line instead of the in line several times will usually scrub it.
 

highgravitybacon

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I've been using the K97 strain of dried German ale yeast to make a Kolsch, and the past few batches have had a sulphur aroma that doesn't seem to go away. Does anyone have any experience with this? What could the possible reasons for the sulphur aroma be? It doesn't seem to produce much flavor wise, but it's definitely there on the nose. Any ideas?

I have used this yeast with great success. It's unfortunate that it isn't sold packaged by the manufacturer as they're only losing money every day they only sell it in 500g bricks and force retailers to package it themselves.

Because the yeast is repacked, there's much more opportunity to contamination than would otherwise be present in the commercial made versions, like how US-05 is made. I have noticed a sulfury aroma that fades over time during fermentation but nothing that persisted. There's some other causes of sulfur that aren't due to the yeast. The main one being DMS compounds from inadequate boil time, intensity. If you pitch cool, like around 55F and slowly raise the temp to the mid 60s by the time fermentation ends, that will help drive off a lot of the sulfur. So you might try:
Pitch at 55-56F, hold for two days.
Raise to 58F, hold for two days.
Raise to 60F, hold for two days.
Raise to 62F for a day.
64F for a day. Hold at 64F. When fermentation appears to be done, raise to 68F and hold for a few days. It should be done fermenting in about 10 days but you could go up to two weeks total. Any longer and you might have underpitched or had very poor yeast health. Nothing wrong with using two liter starter on a stir plate if you have one pack of this yeast. That will help attenuate the beer fully and keep off flavors away.

Pitch cool and as fermentation progresses, slowly raise the temp as fermentation slows. As the temp increases, the ability of the sulfur to remain in solution as a gas decreases. The dissolved CO2 will scrub much of the sulfur out as it leaves the beer. This is what I did and the resulting beer was absolutely delicious.
 
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ziggy13

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@highgravitybacon, I've actually been buying the 500 gram packs and pulling out what I need for a 10 gallon batch, then vac sealing the pack back up with a food saver vacuum sealer. Perhaps it is my fault then? It was really weird because the first few times I did it the sulphur was basically not noticeable and then it seemed to get more and more sulphur with each successive brew. This would tell me I maybe got the yeast a bit contaminated and am causing the sulphur aroma myself...? However, I just opened a brand new 500 gram pack for my last brew it too had the sulphur aroma. Strange.
 

Twinkeelfool

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I have used this yeast with great success. It's unfortunate that it isn't sold packaged by the manufacturer as they're only losing money every day they only sell it in 500g bricks and force retailers to package it themselves.

Because the yeast is repacked, there's much more opportunity to contamination than would otherwise be present in the commercial made versions, like how US-05 is made. I have noticed a sulfury aroma that fades over time during fermentation but nothing that persisted. There's some other causes of sulfur that aren't due to the yeast. The main one being DMS compounds from inadequate boil time, intensity. If you pitch cool, like around 55F and slowly raise the temp to the mid 60s by the time fermentation ends, that will help drive off a lot of the sulfur. So you might try:
Pitch at 55-56F, hold for two days.
Raise to 58F, hold for two days.
Raise to 60F, hold for two days.
Raise to 62F for a day.
64F for a day. Hold at 64F. When fermentation appears to be done, raise to 68F and hold for a few days. It should be done fermenting in about 10 days but you could go up to two weeks total. Any longer and you might have underpitched or had very poor yeast health. Nothing wrong with using two liter starter on a stir plate if you have one pack of this yeast. That will help attenuate the beer fully and keep off flavors away.

Pitch cool and as fermentation progresses, slowly raise the temp as fermentation slows. As the temp increases, the ability of the sulfur to remain in solution as a gas decreases. The dissolved CO2 will scrub much of the sulfur out as it leaves the beer. This is what I did and the resulting beer was absolutely delicious.

So you make a starter with the k97?. I normally use wyeast 2565 but thought I'd try the k97. Reviews I've found were either great, or terrible. I'm a big fan of pitching cool so I might give it a go. 2litre starter on the stir plate.
 
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