Author Topic: A bunch of questions on harvesting yeast  (Read 790 times)

Offline Joe_Beer

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A bunch of questions on harvesting yeast
« on: October 11, 2020, 11:33:07 AM »
I recently brewed a batch using Omega Lutra (kveik) and have been thinking about harvesting the yeast to save for future brews. I've been watching a handful of videos on it (seems to be a few different ways to do it). I have a lot of questions and wondering if anyone can answer. I know this is a lot for one post. The search software here gives results which are kind of all over the place so thanks in advance.

1) why boil the storage jars in water instead of just rinsing in Starsan?
2) after the slurry is poured into a jar from the fermenter, and left to separate, which portion do you want to reclaim? The slurry on top of the trub, or the trub on the bottom of the jar?
3) how many times should the #2 separation step be done?
4) I read something the other day that dry yeast (Safale, etc) can't be harvested effectively. Can someone explain why this is?
5) when brewing another batch using harvested yeast, do you re-harvest the stuff you've re-used ?
6) anyone ever dry their harvested yeast? Seems like a handy way to store it. There's a nice podcast on this site about doing it just wondering what some pitfalls are with it besides tying up the oven for 2 days.
7) can harvested yeast be stored in the freezer (slurry or dried) or will this mess it up?

Offline 4swan

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Re: A bunch of questions on harvesting yeast
« Reply #1 on: October 11, 2020, 12:20:43 PM »
Just a quick response.  I'm sure some others can be more in depth.
1.) boiling with kill a wider range of microorganisms, so it will probably be more sanitary for long term storage.
2.) generally people say the middle of the trub.
4.) Dry yeast is not 100% pure. I don't remember, but over 99%.  So there is a slight chance of unwanted organisms multiply in each batch.
5.) You can, if you maintain sanitation.
6.) I have dried kveik. Pitfalls: not drying it enough, overheating it, contamination.
7.) freezing liquid yeast can rupture many of the cells.

Online HopDen

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Re: A bunch of questions on harvesting yeast
« Reply #2 on: October 11, 2020, 12:31:02 PM »
This is how I proceed. I'm not saying it is right but it has proven to work for me> I have been collecting yeast for a couple of years.

Clean and sanitize a quart mason jar. I use one step and idophor respectively. I can't emphasize enough sanitizing everything including your hands.

Collect your slurry, wipe rim of jar if needed with iodophor. Apply lid loosely and place in your refrigerator. After a couple of days I will tighten lid a bit more. I have read that if you let jar build with pressure it is detrimental to the health of the yeast so you can release any pressure if needed.

On brew day, I will pour off most of the top layer of beer, swirl to mix then pitch cold.

I also will repitch yeast from one fermentor to another when possible.

Good luck!!

Offline majorvices

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Re: A bunch of questions on harvesting yeast
« Reply #3 on: October 11, 2020, 12:34:52 PM »
Quote
1) why boil the storage jars in water instead of just rinsing in Starsan?
2) after the slurry is poured into a jar from the fermenter, and left to separate, which portion do you want to reclaim? The slurry on top of the trub, or the trub on the bottom of the jar?
3) how many times should the #2 separation step be done?
4) I read something the other day that dry yeast (Safale, etc) can't be harvested effectively. Can someone explain why this is?
5) when brewing another batch using harvested yeast, do you re-harvest the stuff you've re-used ?
6) anyone ever dry their harvested yeast? Seems like a handy way to store it. There's a nice podcast on this site about doing it just wondering what some pitfalls are with it besides tying up the oven for 2 days.
7) can harvested yeast be stored in the freezer (slurry or dried) or will this mess it up?

1) If they are clean the star san is fine. You won't lose a pitch of yeast to a clean star san soaked jar.
2) You can tell the healtiest part of the yeast -i it will look "creamy" and is generally in the middle. The brown stuff on the bottom is dead-ish and the stuff of the top is usually trub.
3) Not sure what you mean unless you are "rinsing" the yeast which I recommend avoiding. Just collect your slurry in jars.
4) You can harvest dry yeast no problem. Sure, it's not 100% sterile but neither is the harvest you just selected let alone the 7th generation of a harvest that works just fine. The key is having a healthy pitch that outcompetes all other organisms and doesn't give them a chance to take hold. Fermented beer is a relatively stable product due to it's low pH, alcohol and lack of oxygen.
5) You can re-harvest yeast into infinity from subsequent generations. Just be aware that yeast is at it's healthiest when harvested from a lower gravity beer  anything under 1.065 should be fine. I don't often harvest yeast from batches much higher than this unless necessary. Also, yeast tend to mutate a little each generation so you might start noticing that the beer yeast doesn't flocculate as well or starts to pick up wild yeast flavors. Generally speaking 7-10 gens but I rarely go over 4 or 5.
6) I have not dried my own yeast but have wanted to do that with Kviek yeast. You should try it if it interests you.
7) Freezing yeast is possible but you need to use glycerine so that the cells don't rupture. I have never tried this. You can also freeze samples in slants but it's best to use a lab freezer that doesn't cycle a defrost mode and gets colder than a standard freezer. I haven't tried this either. I have toyed around with plates in a dedicated fridge but it's so much easier just to buy yeast than to maintain a library.
« Last Edit: October 11, 2020, 12:38:24 PM by majorvices »

Offline Saccharomyces

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Re: A bunch of questions on harvesting yeast
« Reply #4 on: October 11, 2020, 01:07:42 PM »
1) why boil the storage jars in water instead of just rinsing in Starsan?

Either sanitation method will work, but I prefer Iodophor to Starsan.  Contrary to what a lot of amateur brewers believe, boiling does not render anything sterile.  Water make the phase change from liquid to gas (boils) at 212F at seal level.  That is not hot enough to kill spores.  Spores are not killed until a temperature of 121C/250F is reached. Suppressing the phase change from liquid to gas until a temperature of 250F has been reached requires boiling at 15psi above normal atmospheric pressure.  The process is known as autoclaving and it can be accomplished with any pressure cooker that is capable of boiling under 15psi above normal atmospheric pressure (most modern European and many modern American pressure cookers can only reach 13psi or less).

Quote
2) after the slurry is poured into a jar from the fermenter, and left to separate, which portion do you want to reclaim? The slurry on top of the trub, or the trub on the bottom of the jar?

If you leave at least a pint of beer behind, you can swirl the contents of the fermenter back into suspension, wait a few minutes for the break, dead cells, and any hop material that made its way into your fermenter to settle before decanting only the liquid fraction, which will be mostly clean yeast.

Quote
3) how many times should the #2 separation step be done?

Never, and I do mean never wash yeast with boiled water.  It is a bad practice that is not based on science.  Always, and I do mean always store a yeast crop under the beer from which it was harvested.  Why? Because a yeast culture shuts down competitors by first consuming all of the oxygen in batch of wort, shutting down aerobic competitors.  It then lowers the pH to around 4, shutting down pH sensitive competitors like the pathogen Clostridium botulinum, which stops replicating below pH 4.6.  Finally, it produces ethanol, which is toxic to all living creatures at different levels, even human beings.  Replacing green beer with water results in a rise in pH and the removal of ethanol, both which protect the culture in storage. Washing yeast is one of the worse practices in amateur brewing.  I can assure you that professional brewers do not wash yeast crops. Small to medium-size craft breweries usually just pump cropped yeast from fermentation vessels into sanitized soda kegs for storage.

Quote
4) I read something the other day that dry yeast (Safale, etc) can't be harvested effectively. Can someone explain why this is?

That is brewing dogma from the days when dry brewers yeast was a hit or miss affair with respect to viability and contamination.  I started to brew in early 1993.  Modern brewers have no idea as to how bad dry yeast was at that point in time.

Quote
5) when brewing another batch using harvested yeast, do you re-harvest the stuff you've re-used ?

It is known as serial repitching and it is how we obtained the cultures used in brewing today.  Back when most brewing cultures were not single strain, brewers used to crop and repitch yeast from good batches while discarding yeast from bad batches.  This practice is known as placing selective pressure on a culture.  Over a period of hundreds of years, these mixed cultures became domesticated and somewhat stable.  Brewers used to mostly top-crop yeast. The reason being is that wild yeast and bacteria generally do not rise to the top and form a skin after flocculation is no longer inhibited by mannose, glucose, sucrose, maltose, and the sugars that a yeast culture can reduce to one of these sugars.

Quote
6) anyone ever dry their harvested yeast? Seems like a handy way to store it. There's a nice podcast on this site about doing it just wondering what some pitfalls are with it besides tying up the oven for 2 days.

It is a practice that I would not recommend because it ensures that your culture will not remain a single strain culture.  The drying process is what used to be large part of the problem with contamination in dry brewers yeast.

Quote
7) can harvested yeast be stored in the freezer (slurry or dried) or will this mess it up?

Yes, but it requires the use of glycerol and a non-frost-free freezer.


I started maintaining a yeast bank on agar slants in 1993 because dry yeast was unusable and liquid yeast was only available on the East Coast during the cool months.  At that point in time, Wyeast was the only real player in the liquid yeast market and their culture collection only contained about a dozen cultures.   White Labs did not appear in the market until 1995.  Plating and slanting cultures allowed me to brew what I wanted to brew without having to worry about obtaining clean yeast cultures.  Today, the only reason I see for keeping a person yeast bank on agar slants is out of curiosity or for cultures that are difficult to obtain.  With good sanitation, if stored under the beer from which they were harvested, most crops will contain viable cells for at least six months in refrigerated storage.  If yeast is pitched within a month of being cropped, it can usually be repitched after the liquid portion has been discarded without making a starter.  Many of us have restarted crops that were over a year old.
« Last Edit: October 12, 2020, 03:33:12 AM by Saccharomyces »

Offline Joe_Beer

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Re: A bunch of questions on harvesting yeast
« Reply #5 on: October 11, 2020, 03:33:56 PM »
Thanks all! Yes, #2 was in regards to yeast rinsing. I did some more poking around and Saccharomyces is spot on. I don't think I'll do that after all.  I forgot to ask  -- how do you know how much harvested yeast to add  to the starter? The Lutra package is 100ML which is about a 1/2 cup of liquid so do you just measure that much out or do you pitch the whole works and re-harvest it all later? I'm assuming any new/viable yeast floats around above the trub and anything that died from the first gen goes to the bottom.

Offline denny

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Re: A bunch of questions on harvesting yeast
« Reply #6 on: October 11, 2020, 03:46:48 PM »
Thanks all! Yes, #2 was in regards to yeast rinsing. I did some more poking around and Saccharomyces is spot on. I don't think I'll do that after all.  I forgot to ask  -- how do you know how much harvested yeast to add  to the starter? The Lutra package is 100ML which is about a 1/2 cup of liquid so do you just measure that much out or do you pitch the whole works and re-harvest it all later? I'm assuming any new/viable yeast floats around above the trub and anything that died from the first gen goes to the bottom.

I estimate a tablespoon or so.  Close enough.
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Offline Joe_Beer

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Re: A bunch of questions on harvesting yeast
« Reply #7 on: October 11, 2020, 05:06:25 PM »
I was wondering about that. A Tablespoon of water is about 14 grams and a packet of dry yeast is 11.5g so it's a nice easy measurement to remember. :)

Offline denny

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Re: A bunch of questions on harvesting yeast
« Reply #8 on: October 11, 2020, 05:15:20 PM »
I was wondering about that. A Tablespoon of water is about 14 grams and a packet of dry yeast is 11.5g so it's a nice easy measurement to remember. :)

Don't know if slurry will weigh the same as water
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Offline Saccharomyces

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Re: A bunch of questions on harvesting yeast
« Reply #9 on: October 12, 2020, 03:43:40 AM »
I was wondering about that. A Tablespoon of water is about 14 grams and a packet of dry yeast is 11.5g so it's a nice easy measurement to remember. :)

The volume of a tablespoon is 14.78ml.  However, you should use the rule of thumb that one 1ml of thick yeast slurry contains approximately 1.2 billion yeast cells; therefore, a tablespoon of thick yeast slurry contains 14.78 * 1.2 billion = 17.7 billion cells.   A 1L starter at maximum cell density contains roughly 200 billion cells.  Pitching 17.7 billion cells is a 1 to 11.3 step ratio. Anything up to 1 to 20 ratio should work without a hitch with most yeast strains.

When pitching straight slurry, we need to pitch 200 / 1.2 = 167ml of thick yeast slurry to approximate the amount of yeast cells in a 1L starter that has reached maximum cell density. In practice, if one's wort is well-aerated, one can get away with pitching 80ml of thick slurry as long as it is fresh.  I can assure you that 80ml of recently cropped yeast will tear through 5-gallons of well-aerated wort with an S.G. below 1.065.
« Last Edit: October 12, 2020, 03:47:06 AM by Saccharomyces »

Offline Joe_Beer

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Re: A bunch of questions on harvesting yeast
« Reply #10 on: October 12, 2020, 11:25:07 AM »
The volume of a tablespoon is 14.78ml.  However, you should use the rule of thumb that one 1ml of thick yeast slurry contains approximately 1.2 billion yeast cells; therefore, a tablespoon of thick yeast slurry contains 14.78 * 1.2 billion = 17.7 billion cells.   A 1L starter at maximum cell density contains roughly 200 billion cells.  Pitching 17.7 billion cells is a 1 to 11.3 step ratio. Anything up to 1 to 20 ratio should work without a hitch with most yeast strains.

When pitching straight slurry, we need to pitch 200 / 1.2 = 167ml of thick yeast slurry to approximate the amount of yeast cells in a 1L starter that has reached maximum cell density. In practice, if one's wort is well-aerated, one can get away with pitching 80ml of thick slurry as long as it is fresh.  I can assure you that 80ml of recently cropped yeast will tear through 5-gallons of well-aerated wort with an S.G. below 1.065.

Thanks for claifying with all the calculations! So, to make sure I get your drift (I'm still reading up on all this), a Tablespoon of thick slurry contains enough cells to make a viable 1L starter. If pitching fresh (within a few weeks of harvest) thick slurry without making a starter, a little more than 11 Tablespoons of thick slurry would be needed but ideal aeration could bring that amount down to about 5.5 Tablespoons (80ml)? Apologies for all the imperial conversions. 

Offline Joe_Beer

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Re: A bunch of questions on harvesting yeast
« Reply #11 on: October 14, 2020, 02:09:14 PM »
I harvested the yeast last night and let it crash in the fridge overnight at 34F. Shouldn't this have a few more layers of stratification to it or will it take a few days to develop?

« Last Edit: October 14, 2020, 02:11:02 PM by Joe_Beer »

Online HopDen

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Re: A bunch of questions on harvesting yeast
« Reply #12 on: October 14, 2020, 07:49:22 PM »
I harvested the yeast last night and let it crash in the fridge overnight at 34F. Shouldn't this have a few more layers of stratification to it or will it take a few days to develop?



It would probably take a few days or longer, not entirely sure about that though. I honestly just harvest and put into the fridge. I don't even try and separate the layers. On brew day I pour most of the beer off,swirl entire contents and pitch cold.

Do an experiment and proceed with 2 of them as you wish but on the 3rd do as I suggest and see if you can tell any difference.

Offline Joe_Beer

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Re: A bunch of questions on harvesting yeast
« Reply #13 on: October 14, 2020, 08:25:43 PM »
Do an experiment and proceed with 2 of them as you wish but on the 3rd do as I suggest and see if you can tell any difference.

Sounds like a plan but isn't that bottom layer dead yeast? I thought the usable stuff stuff was supposed to materialize in the layer above that to get poured off. Maybe I'm all confused.

Offline denny

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Re: A bunch of questions on harvesting yeast
« Reply #14 on: October 14, 2020, 08:26:47 PM »
Do an experiment and proceed with 2 of them as you wish but on the 3rd do as I suggest and see if you can tell any difference.

Sounds like a plan but isn't that bottom layer dead yeast? I thought the usable stuff stuff was supposed to materialize in the layer above that to get poured off. Maybe I'm all confused.

I just pitch it all.  Works great and less chance of screwing something up.
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