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General Category => Yeast and Fermentation => Topic started by: markaberrant on November 24, 2010, 09:41:20 PM

Title: Looking for opinions/facts on reusing dry yeast
Post by: markaberrant on November 24, 2010, 09:41:20 PM
There is a bit of a debate going on within our local club (Regina's ALES).  It started out with John Palmer's "secondary or not," but has turned into whether dry yeast is suitable for reuse.

One of our members came across 2 somewhat contradictory statements from Fermentis:

Homebrewing FAQ - http://www.fermentis.com/fo/60-Beer/60-13_faqHB.asp

"4/ Can I re-use the yeast?
Due to the risks of infection and the inability to check yeast cell counts of yeast slurries it is not recommended as the risk of failure is increased and outweighs the cost of new yeast"

Industrial FAQ - http://www.fermentis.com/fo/60-Beer/60-32_faqIB.asp

"5/ Can the yeast be re-pitched and how many times?
Depending on the integrity of the yeast handling system and the stress placed on the yeast by the brewing process it is possible to re-pitch. The exact number of cycles is dependant on the brewery environment. Dry yeast has proven very effective over 5-6 brewing cycles. "

Just wondering what everyone thinks about this?
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: tygo on November 24, 2010, 11:53:36 PM
"4/ Can I re-use the yeast?
Due to the risks of infection and the inability to check yeast cell counts of yeast slurries it is not recommended as the risk of failure is increased and outweighs the cost of new yeast"

That statement makes perfect sense coming from the people that sell the yeast.  And is likely true as well.


"5/ Can the yeast be re-pitched and how many times?
Depending on the integrity of the yeast handling system and the stress placed on the yeast by the brewing process it is possible to re-pitch. The exact number of cycles is dependant on the brewery environment. Dry yeast has proven very effective over 5-6 brewing cycles. "

Sounds about the same as for any yeast.

So I don't really know and haven't done it but I'd be inclined to say that there would be no real difference between repitching yeast which originally started off as dry or liquid.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: corkybstewart on November 25, 2010, 12:43:31 AM
I did 3 consecutive batches last year with Nottingham-a Fuggles ESB, a rye pale ale and finally a porter.  They were in the conical a total of over 2 months without me taking the lid off.  All 3 beers turned out great.  Maybe the yeast makers could find some flaw by the third batch but non of us who drank it ever did.
I just racked a wheat IPA onto a yeast cake from a rye IPA that I brewed with Safale 0-4.  I'll let you know in a month how it turns out.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: markaberrant on November 25, 2010, 01:17:48 AM
I know people do it, I have done it myself a few times with good results, and plan to try it more, but I'm just wondering if there is any data to backup why reusing dry yeast is possibly good/bad or somehow different than reusing liquid yeast.

I "think" the only possible issue may be that dry yeast is more prone to mutations due to the drying process, thus making it not as good a candidate for repitching, or at least not meant for a high number of successive repitches.  That is my only guess, but I was hoping someone more knowledgable could clarify this.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: majorvices on November 25, 2010, 03:49:23 AM
I've reused US-05 a few times with no problems. IMO the drying technique is "sanitary" enough. Certainly not sterile. But then, OTOH, making starters and harvesting yeast is "sanitary" and not sterile either. So it probably evens out in the end.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: tschmidlin on November 25, 2010, 08:10:17 AM
I think they would stick with their answer to #4 if they were selling liquid yeast at the same price point as dry yeast.  I read it simply as a statement about repitching yeast, not dry yeast specifically.

And answer #5 seems like the first sentence is their acknowledgment of the answer in #4 ("Depending on the integrity of the yeast handling system and the stress placed on the yeast by the brewing process it is possible to re-pitch.")

That's what I get out of it anyway.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: Malticulous on November 25, 2010, 03:17:05 PM
I think US-05 is better the second time. I top crop it or use it the day I rack. I never rinse it or store it for long. In my experience a half cup of fresh slurry is as good or better than a fresh pack.
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: bcastine on November 30, 2010, 01:55:18 PM
I re-pitch US-05 all the time.  Think i've gone as high as 4 generations.  I find it gets better and better.  I top crop when the beer is 50% fermented.  Typically I take  200-300ml of compacted slurry which I pitch into a 10-12 gallon batch.  Airlock activity always occurs instantly.  I just try to pitch the yeast soon after harvesting it, never had a single problem(knock on wood).  Go for it!
Title: Re: Looking for opinions/facts on reusing dry yeast
Post by: jeffy on November 30, 2010, 02:51:00 PM
I'm on my 4th use of W23/70 lager yeast.  I think it's getting better, but that may be because now I can actually measure the amount of slurry volume that I'm supposed to use according to MrMalty.  I've got a lot of leftover yeast that I've been rinsing, although it does not seem to separate much when left in the fridge.  Kai and Blatz had a thread going on that somewhere.