Reusing yeast from Primary

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Reusing yeast from Primary

Postby jeffmc » Thu Feb 20, 2003 1:40 pm

Has anyone reused their yeast from primary vessel after racking?
Do you just scrap the crap off the bottom and repitch it, or do you have to put it in some fresh wort and build it up?
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Primary Repitch: Not the Best Point...

Postby Mesa Maltworks » Thu Feb 20, 2003 2:48 pm

It is best to pitch yeast from the secondary, not the primary. 2 major reasons: 1)Via natural selection, the yeast that settles out in the secondary represent the healthiest population among all of the yeast. In a perfect world, it would be optimal to harvest the yeast that has flocced in the middle of the secondary as this yeast will have the highest viability. This is rather difficult to do in practice, though, as you would basically have to stare at the carboy until the right moment... which via Murphy's law would of course happen either when you were asleep, at work or while enjoying your last batch ! and 2) There is a LARGE proportion of protein and vegetal matter mixed in the yeast in the primary. Once fermentation has ceased, the least healthy yeast is what settles out in the primary. Since there is no sugar left for them to eat, they go into preparation for dormancy. BUT... bacteria CAN metabolize some of the proteins in the trub. After the sugar is gone, they simply shift to metabolize that. This means that generally, the trub in the primary contains 2 things: the least healthy of the yeast population which is now or almost dormant and an active and growing bacterial population.

You can have good results on top of primary trub the first couple of times which is due to high cell counts, but each successive use of this trub derived yeast will contain more and more bacteria and, via natural selection, increasingly deficient yeast. What are the possible outcomes? 1) Bacterial infection; 2) Overattenuation; 3) Excessive lag; 4) Excessively rapid fermentation (yes... this can be bad); 5) Underattenuation; 6) Yeast derived flavor profile drift; 7) high yeast mortality leading to autolysis (nasty flavor from yeast cell breakdown).


How to solve this.... yeast washing and if infection is suspected, acid washing. Both of these proceedures also carry the risk of either contamination, or in the case of acid washing, viability reduction. Acid washing is best left to persons with good lab equipment as extremely accurate pH readings are required using $300 + pH meters, a microscope, hemocytometer and viability stains. Yeast washing, however, is relatively simple as all you are doing is eliminating the proteins and vegetal matter. BUT... you are still left with the least healthy yeast and whatever bacteria was present.

For reliability sake and flavor consistency, it is best to either repitch new yeast, pitch yeast that was orginally propagated from a yeast pack or cultured from a single cell and propagated to pitching volume (not as hard to do as it sounds).

An exception to the above: IF you use a conical fermenter with a sloped bottom, through successive bleeding of the sediment, you can obtain the best portion of the yeast for repitching. This is essentially what most small craft brewers do that have conicals. They pitch from cone to cone through hoses or buckets.
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Darwin's Bulldog

Postby Gravity Thrills » Thu Feb 20, 2003 5:26 pm

Eric, I may never, ever have the opportunity to clarify on post of yours again, so I had better do it now. The least viable yeast (unfit variants) are filtered out of the system in primary through artificial selection, not natural selection. This is, of course because the selective environment (the fermenter) is being directly manipulated by the brewer, rather than left to the whim of a dynamic natural environment over time. Since it is purposefully directed by human hands, rather than left to the "blind watchmaker," artificial selection produces notably different phenotypes in a fraction of the time reqired by natural selection. Nevertheless, artificial selection has yet to foster the sort of macromutational events that lead to eventual speciation. Maybe in a million years or so...

Carry On,
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harvest yeast for dummies

Postby canman » Thu Feb 20, 2003 6:12 pm

just thought I'd throw this out there. Excellent article to get you started
http://www.homebrewsupply.com/libationa ... astwas.htm
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MACROMUTATIONAL EVENTS......

Postby dartedplus » Thu Feb 20, 2003 6:18 pm

I dont think I'm even in this conversation....


ed (feeling kinda insignificant cuz I dont know any big words like that)
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Darwins missing link???

Postby Fraoch » Fri Feb 21, 2003 3:15 am

Doesnt your post predispose that 2ndary is carried out in a separate vessel???.If dropping from primary AT critical flocculation to 2ndary,you are ensuring that all protein and vegetal matter are above wort level.Therefore, the new clean head formed during 2ndary is the cleanest and healthiest yeast harvested.This then settles once fermentation subsides and if procedure is followed correctly, ensures natural selection through artificial selection.After all, artificial selection can only exist if outside manipulation occurs.

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Continued

Postby fitz » Fri Feb 21, 2003 4:18 am

Following Mesa Eric's thought process(Yes, I think I got it)
If the secondary has better yeast than the primary, and you bottle condition your beer, then make a yeast starter from that. It should have the most viable yeast in it. Least the other for septic enzymes. That's what I use my trub for. Works great.
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'taint natural...

Postby Gravity Thrills » Fri Feb 21, 2003 6:29 am

Outside manipulation is occurring, unless we are talking about some wild grain stew spontaneously fermenting in a tree stump somewhere.

Whether you are fermenting in two separate vessels or dropping the primary sediment out of a uni, harvesting yeast from the bottom of the fermenter or from the krausen, you are the one defining and manipulating the environment that determines which variants in the yeast populationare 'most fit' and 'least fit.' That is why it is artificial selection - the environment is not one of stochastic dynamic change. Rather, it is one in which the brewer determines fermentation temperatures, pitching rates, starting gravity, and when to dump the first yeast to floc out.

Cheers,
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The Selection Is Natural, the Environment is Artificial....

Postby Mesa Maltworks » Fri Feb 21, 2003 7:31 am

Gravity;

Yes... you are completely correct. Technically, for complete natural selection to occur, everything must evolve at it's own pace without any intervention. I used this term somewhat erroneously, but to point out that in our worts the least healthy cells among the population will floc out in the primary on their own accord naturally without our intervention. (ie... natural selection in an artificial environment). Of course, we could intervene and drop the temperature to speed floccing, but it will occur anyway, even with "nonflocculant" strains such as Weitzens, it just takes one heck of a long time. But in my experience, few homebrewers do this while the beer is in the primary, but rather once they have racked to the secondary.

Is that a bit better?

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Postby Mesa Maltworks » Fri Feb 21, 2003 7:55 am

Fraoch, I may have misunderstood your post and have the following question related to this excerpt of your message:

"...Therefore, the new clean head formed during 2ndary is the cleanest and healthiest yeast harvested."

Yes, this basically agrees with what I posted except the part I may be misinterpreting which is the "new head" part.

Usually once primary fermentation is complete a new krausen doesn't form after transfer to the secondary. I could see, however, this occuring if the beer was gyled (new wort added), sugar added, or if the beer was not fermented out yet,especially if oxygen was taken into solution during transfer or artificially added. If the beer is being transferred prior to reaching terminal gravity, you are going to end up with some of the less healthy cells. But... this is still much better than pitching on/from primary trub as you will leave the vast majority of the protein and vegetal matter behind.
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Yup: Ya Got It...

Postby Mesa Maltworks » Fri Feb 21, 2003 8:00 am

That is an excellent practice which is exactly what a number of commercial brewers that lack a propagation lab and yeast brink dosing system do to bottle condition their brews.
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New head

Postby Fraoch » Sat Feb 22, 2003 2:57 am

Mesa, we may be travelling down a farmiliar path here.My main priority because of open fermentation and trub collection due to run off through counterflow chiller is to prevent the krausen from primary falling through the beer.In order to do this i rack off when the yeast has reached anaerobic condition,i judge this stage (visually) to be at the point when large billowing bubbles are being formed.After all, the yeast has finished multiplying and is now producing alcohol and co2, the trub etc is sitting on top of the beer.If you drop the beer at this stage a second head will be formed and even if brewing the darkest of stouts, will be white and fluffy,This then drops through the beer within 12 - 24 hrs and 2ndary commences.Yes i rack off slightly early, but this is to ensure the cleanest beer i can for the longer 2ndary period.Also with open fermentation for primary, you really do not want to be any later and have the beer exposed to atmosphere for any period of time. Id be interested in your procedure for open.
A stickler for old ways,

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OK... I've Got It....

Postby Mesa Maltworks » Sat Feb 22, 2003 9:27 am

Ok... as I guessed, you are racking to secondary at pre-terminal. With the technique you use (yes... we've been there!), that is the wisest method.

As far as how I'm doing it... I do two successive trub bleeds from my fermenter base and then let'er fly to terminal or step cool, dependant on brand. Example: I produce an American IPA that is bittered to 92 IBU. It has a very complex malt bill, but not enought to compete with this hopping rate on it's own, so I have to stop fermentation by semi-crash cooling when it reaches 1.017. This residual sweetness mingles with the malt flavor to balance against the high hopping rate. If I was operating without a lid, I'd never do this, of course, as the krausen fallout would eventually infect the beer which is what you are avoiding with your techniques. In my case, even though I'm at atmospheric pressure in the fermenter, the lid (no gasket, it just sits on top) allows me to maintain a very dense CO2 blanket that prevents oxygen ingress. By dropping it 5c/day down to -1c, I do not loose this protection via vacuum like I would if I literally crashed it to that temp in one day. After the desired contact time at this low of a temperature, I move my brews to Grundy's, which are sealed, to further condition at 38 deg. f. Using these techniques I have had no problems. I repitch new cultures after 7 generations for all of my beers. In a commercial setting with open fermentation (even the way I'm doing it) it would be unwise to go beyond this point in re-pitching. To do so would require a system truly geared for continuous open fermentation like the formerly (unfortunately) used Burton Union systems... ie.. Bass.

Without some of the equipment I have, I don't see an easy way a homebrewer could do open fermentation this way, even with a lid. Simply moving the fermenter to the point where it would be refrigerated would not only kick the krausen down, but also allow oxygen ingress... not good !

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I never realised

Postby Fraoch » Sun Feb 23, 2003 2:01 am

Never knew Mesa that you could reduce temp to -1c and not lose krausen.I was always led to believe that it is temperature determined as well as developement stage.Can you clarify a few points for me though, im most interested.
I take it that you are cooling to -1c in order to halt all fermentation and therefore leave the finished product with residual sweetness,why is it better to do this at primary and not rack to 2ndary at 1017 and crash cool then?Is it to avoid the very process i have described in that you do not want a new head to form and therefore avoid the beer sitting on yeast sediment for long periods( maturation).I dont know of the technique you describe and would like to learn more as to why the krausen remains at such low temps,any chance of explaning further for me??
Wassail!!!!!
Fraoch

Ps, thanks for converting to metric for me ,Im forever looking up the equvalents otherwise!!
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Replies...

Postby Mesa Maltworks » Mon Feb 24, 2003 8:27 am

"Never knew Mesa that you could reduce temp to -1c and not lose krausen."

You can't ! I let the krausen fall. I can do this because the CO2 blanket at the top of the fermenter protects the krausen from infection. Since I do trub bleeds, I am removing the highly flocculent population along with the other matter. When the krausen falls, this allows me to harvest the less flocculant, but more viable portion of the yeast. This is VERY important to me as I filter all but a couple of my beers with a diatomaceous earth filter. If I harvested the more flocculant portions, I risk binding my filter bed (REALLY BAD !)

"I take it that you are cooling to -1c in order to halt all fermentation and therefore leave the finished product with residual sweetness..."

The example I gave, my AIPA, detailed the technique that I use specific to that brand. I allow some of my beers to go terminal without arresting fermentation, then I do my cooling thing. The yeast that floccs out after the cold resting period is what I then harvest and re-pitch just prior to sending the beer to the aging tanks (sealed, no pressure though). The amount of yeast left after this transfer allows the beer to age much like a real ale, but is not enough to cause filtration problems later.

"...why is it better to do this at primary and not rack to 2ndary at 1017 and crash cool then?"

In a typical home brew setting, it is not advisable to do this in the primary for the reasons we have already discussed. The example I gave is what I do at my brewery, not at home. I am essentially recreating the conditions that exist after racking to a secondary through successive trub bleeds from the fermenter cone.

My techniques are part traditional, part adaptive due to the equipment I have to work with. I am forced to marry current techniques with former to minimize the risk of having batches go bad as each batch is 12.27 hl.

Does that help? If not, keep 'em coming !

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