Author Topic: Yeast Harvesting  (Read 1493 times)

Offline Saccharomyces

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Re: Yeast Harvesting
« Reply #15 on: September 06, 2020, 11:48:45 am »
Mark, I think I'd take exception to "need to".  I certainly don't and it hasn't caused any problems.

The OP appears to want to repitch more than a handful of times. However, he appears to be serially repitching the entire cone. In order to do that without degradation of performance and flavor, one cannot continue to repitch dead as well as early and late floccing cells.  That is why pro brewers crop from the middle of the cone. It is the conical equivalent taking the middle head from a true top-cropper. Can one pitch the entire contents? Absolutely, but not without paying a price when serially repitching.
« Last Edit: September 06, 2020, 05:39:30 pm by Saccharomyces »

Offline denny

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Re: Yeast Harvesting
« Reply #16 on: September 06, 2020, 12:30:08 pm »
Mark, I think I'd take exception to "need to".  I certainly don't and it hasn't caused any problems.

The OP appears to want to repitch more than handful of times. However, he appears to serially repitching the entire cone. In order to do that without degradation of performance and flavor, one cannot continue to repitch dead as well as early and late floccing cells.  That is why pro brewers crop from the middle of the cone. It is the conical equivalent taking the middle head from a true top-cropper. Can one pitch the entire contents? Absolutely, but not without paying a price when serially repitching.

I guess what I'm saying is that maybe you shou,d try to qualify your answers a bit.  Believe me, I learned the hard way about making overly broad statements.  While I have no reason to doubt your advice on this I also know that other methods work also.
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Offline Saccharomyces

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Re: Yeast Harvesting
« Reply #17 on: September 06, 2020, 05:53:30 pm »
I get it, Denny.  I have repitched the entire contents minus the break and dead cells, which is pretty easy to accomplish in a 5-gallon-size batch by leaving behind about a pint of green beer, swirling the culture into suspension, and waiting a few minutes for the break and dead cells to sediment out before decanting the cells that are still in suspension.  That works for a few repitches, but ultimately culture degrades over time.  I serially repitched a true top-cropping yeast strain that I acquired from the NCYC in England a dozen times without a degradation in performance.  That is when the practice of discarding the brown head and cropping the second head became crystal clear.  This particular culture was not the easiest to use due to being a Yorkshire culture and Yorkshire cultures are notorious for having high O2 requirements.  If a brewer is not careful, Yorkshire cultures can come out of suspension early and leave a brewer with a diacetyl bomb.

Here is the brown head forming from that culture:



Here is the second head that formed after the brown head was skimmed:



I could repitch the second head indefinitely without a degradation in performance.  Sure, the culture would adopt a house character from selective pressure, but it would not become powdery or start to develop off-tastes due to an ever increasing dead cell count.   That is what happens when a brewer who serially repitches does not select from the middle of the cone.  In the end, does a brewer have to select the cells from the middle of the cone? Well, not if he/she only plans to repitch the culture a handful of times before returning to the reference culture. However, for those who want to repitch a culture until it adapts to their brewery, selecting from the middle of the cake is not an option, nor is plating the middle of the cake after a number of repitches.  The goal is to select cells that perform well in one's brewery.

« Last Edit: September 06, 2020, 06:00:46 pm by Saccharomyces »

Offline Bel Air Brewing

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Re: Yeast Harvesting
« Reply #18 on: September 07, 2020, 07:36:35 am »
Here are a couple pics of the harvested W-34/70, 7th generation. There is over 1/2 gallon, probably almost 3 qts. The aroma is very clean, and fresh. No "off" odors at all.




« Last Edit: September 07, 2020, 07:40:57 am by TXFlyGuy »
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Offline goose

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Re: Yeast Harvesting
« Reply #19 on: September 07, 2020, 08:12:43 am »

I have one such culture that I refer to as Natasha.  There is slight wild note to this culture when making bread, but it never becomes sweetart sour because the domesticated yeast keeps lactobacillus and acetobacter in check.  I have another culture that is pure wild microflora that I call Boris.  This culture can become sweetart sour if the fermentation is retarded more than 24 hours.  I use Natasha for my pizza and calazone dough ferments.  Boris is used for straight-up artisan sourdough baking.


Can someone say "Moose and Squirrel"?  Sorry, bad humor here. Couldn't help myself!

That said, good information here, Mark!  Thanks!
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Offline denny

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Re: Yeast Harvesting
« Reply #20 on: September 07, 2020, 08:18:53 am »
I get it, Denny.  I have repitched the entire contents minus the break and dead cells, which is pretty easy to accomplish in a 5-gallon-size batch by leaving behind about a pint of green beer, swirling the culture into suspension, and waiting a few minutes for the break and dead cells to sediment out before decanting the cells that are still in suspension.  That works for a few repitches, but ultimately culture degrades over time.  I serially repitched a true top-cropping yeast strain that I acquired from the NCYC in England a dozen times without a degradation in performance.  That is when the practice of discarding the brown head and cropping the second head became crystal clear.  This particular culture was not the easiest to use due to being a Yorkshire culture and Yorkshire cultures are notorious for having high O2 requirements.  If a brewer is not careful, Yorkshire cultures can come out of suspension early and leave a brewer with a diacetyl bomb.

Here is the brown head forming from that culture:



Here is the second head that formed after the brown head was skimmed:



I could repitch the second head indefinitely without a degradation in performance.  Sure, the culture would adopt a house character from selective pressure, but it would not become powdery or start to develop off-tastes due to an ever increasing dead cell count.   That is what happens when a brewer who serially repitches does not select from the middle of the cone.  In the end, does a brewer have to select the cells from the middle of the cone? Well, not if he/she only plans to repitch the culture a handful of times before returning to the reference culture. However, for those who want to repitch a culture until it adapts to their brewery, selecting from the middle of the cake is not an option, nor is plating the middle of the cake after a number of repitches.  The goal is to select cells that perform well in one's brewery.

Gret pics, Mark, and an excellent demonstration of what you're talking about.
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