Primary vs. Secondary yeast harvesting

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HardcoreLegend
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Primary vs. Secondary yeast harvesting

Post by HardcoreLegend » Mon May 17, 2004 12:59 am

I have been trying to harvest my yeast from my carboys and repitch them to new brews. I've been having rather mixed results. Should I save the yeast from the primary fermentation, or from the secondary? I usually save the yeast in a growler under airlock in the beer fridge until reuse.

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Mesa Maltworks
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Yeast Harvesting...

Post by Mesa Maltworks » Mon May 17, 2004 6:01 pm

You should only harvest yeast from the secondary. This is where the most viable and vital population exists and is virtually devoid of trub.

You can save yeast harvested this way, refrigerated UNDER DISTILLED WATER (NOT BEER), with little effect on viability for as long as 2 weeks. Try to keep the yeast as close to 32 Deg. F. as possible to slow cell metabolism to a crawl. Beyond this length of time, I would not use it as the viability and vitality will have been negatively effected and can create a myriad of problems. Good, clean yeast is readily available and cheap enough that it is not worth risking problems and wasting an expensive batch of beer if the stored yeast is questionable.

Eric

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More yeast questions...

Post by HardcoreLegend » Tue May 18, 2004 12:27 am

If you don't mind....
If you keep a growler of harvested yeast from the secondary under distilled water in the beer fridge at cold temps for longer than two weeks, could you make a starter with it? Would you mind to tell me what "myriad of problems" I could possibly expect? I just want to make the best !@#$ beer I can. Help me learn. Thanks Eric!

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all the time

Post by canman » Tue May 18, 2004 4:05 pm

I reuse my yeast all the time. For me it is expensive and I like bang for the buck. I store mine in mason jars under "beer" and have had excellent results even after a couple months. I would however suggest a starter. I also use the yeast from primary quite often with no ill effects

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More Yeast Answers...

Post by Mesa Maltworks » Wed May 19, 2004 5:08 pm

Q:"If you keep a growler of harvested yeast from the secondary under distilled water in the beer fridge at cold temps for longer than two weeks, could you make a starter with it?"

Answer: A starter could be made, but the yeast will have been under alot of stress beyond 2 weeks and will have significantly decreased viability. The degeneration of the cell walls (via autolysis)releases yeast toxic compounds that also furter weaken the remaining live cells. Those that survive will have mutated from the original culture. That is why at this point, most yeast knowledgeable brewers would elect to reculture the yeast via plating. Once plated and grown, a visibly correct colony can be observed, a few cells can be collected and propagated up to starter size.

A bit of a different topic, but still worth metioning in this answer is that you can store yeast up to 1 year under distilled water at 32 deg. F., but the source of the yeast has to be from a pure culture not a fermentation. The culturing process centers on yeast reproduction aerobically rather than fermentation. The yeast coming into the distilled water in this state have VERY strong cell walls that have not been degraded by exposure to alcohol nor have the yeast been exposed to varying food supplies in their life. They also have not produced glycogen for dormancy yet, so by keeping them in distilled water at a very cold temperature, this process is retarded much longer than trying to do this with harvested yeast from a fermentation.

Q:"Would you mind to tell me what "myriad of problems" I could possibly expect? "

A: The reason I used the term "myriad" is that there are a ton of variables that can change what effects can result from trying to use yeast in less than optimal shape. The most common problems are 1) sluggish fermentation and 2) under attenuation. Others can include a reduction in the yeasts ability to metabolize the "tougher to eat" sugars in the wort which could leave the beer underattenuated, sweet or viscous; the lag time between pitch and fermentation could increase leaving the wort much more susceptible to infection; then there is flavor drift caused by metabolic mutation... this is the one that those store yeast too long may not notice, but only because they may not have brewed the same beer from it as when it was harvested. If they kept a bottle or so from the first batch and brewed the exact same beer 1 month later using the harvested yeast and then treated it exactly in the same way until drinkable, I guarantee that the yeast character will not taste the same. It would be impossible to list all of the possible effects from this mishandling as they can be strain and temperature specific.

Here is the way to see if your storage method is appropriate (from a performance, not flavor standpoint): Brew the exact same beer twice, one pitched with a new, pure culture, one with a harvested and stored sediment and compare the starting and finishing gravities and how long it took to reach final attenuation. Look up the yeast vendors attenuation specifications for the yeast strain you used. If it sped up or slowed down (more likely) or/and attenuated below or above (more likely) the first batch with the pure culture, it has been negatively impacted via handling. A note: A number of brewers think fast fermentations are a good thing (<4~5 days). Actually, this is not good. The reason is that if the yeast ferment that fast, they cannot re-absorb the diacetyl they produced during fermentation. Usually once this has occured, you cannot correct for it.

An in-between technique: You can take secondary harvested yeast and wash them with a chlorine dioxide solution. This technique is much less detrimental than acid washing and has a wider safety margin if the chemical is mis-measured. After doing this you should viability stain the yeast to see how viable the cells are prior to storage. This is easily done with methylene blue stain and a microscope. If the cells are ok. yeast prepared in this way can be stored up to 4 months with little negative impact. If you want to know more about this I can post directions on how to do this. BUT... even though it is not a big investment to execute this technique, it still requires an investment which may errode your attempts at saving money until you have reached a payback point. How quicky you would reach that point would depend on how frequently you brew.

Statement: "I just want to make the best !@#$ beer I can."

Answer: If this is the criteria, there is only 1 answer... pitch new, pure cultures every time if you are not properly equipped or knowledgeable on how to maintain optimal yeast practices and techniques.

Eric

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canman: OK... interested in incremental improvement ?....

Post by Mesa Maltworks » Wed May 19, 2004 5:35 pm

At least pour off the majority of the beer from the yeast and add distilled water. Alcohol is the leading culprit to cellular breakdown, after all it is a solvent. This alone should lead to even better results.

I would be interested in viewing your fermentation statistics from like batches across generations beyond the initial pitch to see if you actually are experiencing no variations. I guess it might be possible, but according to the brewing microbiologists that I was trained by and know, the extended storage you described and the fact you are storing yeast in contact with alcohol and, in some cases trub, will negatively impact the yeast.

The problem with primary trub re-use is that there is a very high amount of the least healthy yeast that settled out on the bottom of the fermenter before transfer to the secondary. And to boot... there is alot of protein which bacteria can eat, but yeast can't. So, when the sugar is depleated in this trub slurry, the bacteria continue to multiply. The use of primary trub couples the high proportion of dead, viable but not vital, metabolically compromised (stressed) and mutated yeast cells with an increasing bacterial load. I think you can see this can easily lead to problems. I would recommend that you stop pitching primary trub.

Eric

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ain't no scientist

Post by canman » Tue May 25, 2004 11:32 am

by no means am I one. I do know what works though and I do feel you can make repeatable beers time after time. I do 2 beers over and over, 1 is a standard ale and the other a wheat using 1056 and 3333 respectively. They are pretty much identicle every time. I repurchase my yeast every 10-12 batches and have done so for over 3 years like this
I can't believe I'm the only one who stores yeast like this. Come on out you loveless yeast abusers!!!!!!

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Have to agree with Mesa

Post by fitz » Wed May 26, 2004 7:41 am

Eric is right, if you have a great batch, and want to save some of the secondary yeast, that is fine.
You always run the risk of contaminants, wild yeasts, and bacteria everytime you save it.
Canman, I am glad you have been lucky. I have used a few yeasts over, but I have also had mixed results.
Eric is using his knowledge to tell us how to have consistently great beer. I have to go with the Stats.
I will reuse yeast, but I'll do it with some guidlines.

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