Author Topic: Just say "no" to yeast rinsing  (Read 5372 times)

Offline S. cerevisiae

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Just say "no" to yeast rinsing
« on: July 11, 2014, 04:51:36 PM »
A yeast culture "owns" a batch of wort by shutting out competitors.  It rapidly consumes dissolved oxygen, which shuts out aerobic microorganisms.  A yeast culture also lowers the pH of the medium from around 5.2 to around 4.2, which shuts out pH sensitive anaerobic microflora.  The final defense that a yeast culture mounts is the production of ethanol, which is toxic to microorganisms, including the culture itself.

Replacing green beer with boiled water strips the culture of the force field that it built for itself, which means that the water has to be completely free of wild vegetative cells (and spores that can germinate into vegetative cells) because they will feast on dead yeast cells.   Bacteria cells multiply three times faster than yeast cells (i.e, an eight-fold increase in bacteria cell count for every two-fold increase in the yeast cell count), which means that a small infection can overtake a larger yeast culture when pitched into fresh wort.

The best way to crop is to "top crop" at high krausen.  However, top-cropping requires one to use a true top-cropping strain in order to be most effective.   Top-cropping naturally purifies a culture because wild yeast and bacteria do not floc to the top.  Top-cropped yeast can be repitched almost indefinitely.

When using a non-top-cropping yeast strain, I usually leave enough liquid behind after racking to be able to swirl the solids back into suspension (my primary volume is 1/3 to 1/2  gallon larger than the volume  I expect to rack).  Swirling the solids back into solution using green beer, waiting a few minutes for the heaviest fraction to settle, and then decanting the liquid fraction has the same effect as rinsing with boiled water; however, it keeps the low pH, ethanol laden environment intact.   If one wants to attempt to rid the culture of mutants, one can decant and discard most of the supernatant (liquid above the solids) as soon as a creamy layer of yeast forms on the bottom of the container.

As stated above, one of the first things that a yeast culture does when pitched into a batch of wort is to lower the pH from around 5.2 to around 4.2.  One has heard that pathogens do not grow in beer.  One of the reasons why pathogens do not grow in beer is due to its relatively low pH.  For example, Clostridium botulin growth is inhibited below pH 4.6.

Contrary to what was written in early amateur brewing books, brewing yeast cultures do not respire in wort due to a phenomenon known as the Crabtree effect.  Hence, brewing yeasts do not go through a period of respirative (aerobic) growth before they start to reproduce fermentatively (anaerobic growth).  In the presence of glucose levels above the Crabtree threshold, all reproduction is fermentative.  As many of you probably noticed while reading Yeast, yeast cells use dissolved oxygen to  build ergosterol and unsaturated fatty acid (UFA) reserves (these reserves are shared with with all of the daughter cells).  Yeast cells perform this feat by shunting oxygen to the respirative metabolic pathway while simultaneously metabolizing the carbon source via the fermentative  metabolic pathway.

What this preference to reproduce fermentatively means to a brewer is that yeast cells pretty much start producing ethanol almost as soon as they are pitched into a batch of wort.  While ethanol has a limiting effect on the viability of a yeast culture, it also protects the culture from infection.  Boiled water is not truly sterile.  Boiled tap water also tends to have a pH of at least 7.0; therefore, it raises the pH of the culture.

With the above said, most experienced amateur brewers eventually reach the conclusion that one can just crop and repitch without doing anything to separate the viable cells from the dead cells and break material, especially if they leave most of the break and hop material in the kettle.   Less is definitely more when cropping yeast.

« Last Edit: June 01, 2015, 07:26:50 AM by S. cerevisiae »
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

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A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline chumley

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Re: Just say "no" to yeast rinsing
« Reply #1 on: July 11, 2014, 06:22:04 PM »
Excellent post.  I have been brewing since 1990, and I never bought into the rinsing hooey.  And, my beers all attenuate well and are excellent.

Why add silly extra steps to the process?  KISS

Offline S. cerevisiae

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Re: Just say "no" to yeast rinsing
« Reply #2 on: July 11, 2014, 07:04:26 PM »
KISS indeed!
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

Separate the National Homebrew Conference from the National Homebrew Competition

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline S. cerevisiae

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Re: Just say "no" to yeast rinsing
« Reply #3 on: July 11, 2014, 07:18:39 PM »
By the way, here is an interesting publication that I found on the Fermentis website this evening: http://www.fermentis.com/wp-content/uploads/2010/07/2010_TT_EN_HD.pdf


"Recovering yeast after fermentation and repitching

Recovering yeast after fermentation and repitching is possible if the cell count is controlled to give the correct yeast pitching levels. In order to control them, laboratory equipment will be needed. In the same way and using the same equipment, bacteria can be removed by acid washing in carefully controlled conditions. In case of repitching, yeast must not be stored out of beer for long periods, even at low temperatures, as yeast glycogen levels will fall causing slow fermentations.

Yeast mutation occurs rapidly in brewing environments, repitching can be a delicate operation and may cause beer quality problems in terms of flavour, yeast settling, diacetyl absorption. Effects of repitching can be seen in as few as 3 to 5 brews especially concerning diacetyl reabsorption. For ale beers that are generally more flavoursome diacetyl levels are less critical."



Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

Separate the National Homebrew Conference from the National Homebrew Competition

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline erockrph

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Re: Just say "no" to yeast rinsing
« Reply #4 on: July 11, 2014, 07:28:12 PM »
Great info. One of the reasons I was hesitant as a newbie to reuse yeast was I thought I was doing it wrong (or at the very least, half-assing it) by not washing my yeast. Now my only reason is that I don't want to catch s*** from my wife for all the mason jars in the fridge.
Eric B.

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Offline quattlebaum

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Re: Just say "no" to yeast rinsing
« Reply #5 on: July 11, 2014, 07:29:14 PM »
S. Cerevisiae i really enjoy your post! Very educational truly appreciated ;D

Offline Joe Sr.

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Re: Just say "no" to yeast rinsing
« Reply #6 on: July 11, 2014, 07:41:14 PM »
I didn't read your post.  It's far too long for my attention span this evening.

I like the Old Rasputin in your fridge, though.  You get props for that.

Between that and the subject line, I think I got all I need to know.

I've never bothered rinsing yeast, and I don't see any reason to start.  Stay with what works.
It's all in the reflexes. - Jack Burton

Offline Jeff M

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Re: Just say "no" to yeast rinsing
« Reply #7 on: July 12, 2014, 07:14:27 AM »
I rinsed ~1 cup of slurry with 2~ cups of autoclaved(15 min at 15PSI in a pressure cooker) water about a week ago.  do you think using this is a bad idea?  Its a first gen slurry.

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Offline Kinetic

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Re: Just say "no" to yeast rinsing
« Reply #8 on: July 12, 2014, 10:10:16 AM »
I like the concept of re-using yeast.  Saving money on yeast is fiscally responsible.  The results are good and can even be subjectively better than the first pitch depending on your preferred taste.

However, I tend to prefer a different yeast on the next batch and use a wide variety of yeasts.  It may be 3-5 months before I get a hankering for the same yeast, so I rarely harvest and re-use yeast.  If I did, I could save maybe $20 a year.  Not really worth the risk or effort to me.  Keeping a proper yeast bank with multiple strains is more effort than I'm willing to provide.

Occasionally, when I want to use the same yeast twice in a row, I'll make a double sized starter and split it in half.  Use one half immediately and save the other for the next batch.  That seems to work well for me.   

Offline erockrph

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Re: Just say "no" to yeast rinsing
« Reply #9 on: July 12, 2014, 11:25:34 AM »


Occasionally, when I want to use the same yeast twice in a row, I'll make a double sized starter and split it in half.  Use one half immediately and save the other for the next batch.  That seems to work well for me.   

I do this pretty often when I actually need a starter (which is generally just for lagers, since I brew 3 gallon batches). I figure if I'm growing a pitch I might as well make enough for two beers.

So, question to the yeast experts in the audience - how long would you say is too long to hold on to some yeast slurry under beer in the fridge I'd you're planning on making a starter with it prior to pitching?
Eric B.

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Offline S. cerevisiae

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Re: Just say "no" to yeast rinsing
« Reply #10 on: July 12, 2014, 02:40:03 PM »
I rinsed ~1 cup of slurry with 2~ cups of autoclaved(15 min at 15PSI in a pressure cooker) water about a week ago.  do you think using this is a bad idea?  Its a first gen slurry.

I personally believe that that yeast rinsing serves no useful purpose.
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

Separate the National Homebrew Conference from the National Homebrew Competition

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline ynotbrusum

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Re: Just say "no" to yeast rinsing
« Reply #11 on: July 13, 2014, 06:30:20 AM »
I rinsed ~1 cup of slurry with 2~ cups of autoclaved(15 min at 15PSI in a pressure cooker) water about a week ago.  do you think using this is a bad idea?  Its a first gen slurry.

I personally believe that that yeast rinsing serves no useful purpose.

Agreed.  I just repitch slurries and let the yeast sort it out, figuring that in most fights at the microbe level the yeast will win.  Be sanitary, of course, but let them stay in beer and don't mess with them otherwise.
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Re: Just say "no" to yeast rinsing
« Reply #12 on: July 13, 2014, 07:55:44 AM »
I rinsed ~1 cup of slurry with 2~ cups of autoclaved(15 min at 15PSI in a pressure cooker) water about a week ago.  do you think using this is a bad idea?  Its a first gen slurry.

I personally believe that that yeast rinsing serves no useful purpose.

My experience with rinsing and not rinsing agrees with you.
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Offline S. cerevisiae

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Re: Just say "no" to yeast rinsing
« Reply #13 on: July 13, 2014, 08:20:54 AM »
So, question to the yeast experts in the audience - how long would you say is too long to hold on to some yeast slurry under beer in the fridge I'd you're planning on making a starter with it prior to pitching?

Viability is strain and storage temperature dependent.   It comes down to how fast the cells exhaust their glycogen reserves.  A yeast crop will last a long time if one feeds it fresh wort every three to four weeks.  Some strains will last several months to a year or more without doing anything.  Granted, viability will drop over time, but there are a lot of yeast cells in 150 to 200 milliliters of slurry.   

I propagated a culture from a bottle of Tupper's Hop Pocket back in the nineties.   I repitched that culture every three to four weeks through the spring and summer.  The final crop sat in my refrigerator undisturbed until April of the following year.  I was about to discard it when a brewer that I knew at the time asked if he could have it.  I suggested making a starter, but he pitched the crop straight into a 5-gallon batch after decanting the supernatant.  I was astonished at how well it performed. 
« Last Edit: July 14, 2014, 02:02:03 PM by S. cerevisiae »
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

Separate the National Homebrew Conference from the National Homebrew Competition

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline klickitat jim

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Re: Just say "no" to yeast rinsing
« Reply #14 on: July 13, 2014, 08:45:14 AM »
I used to "rinse" my yeast for repitching. Then I tried a slightly different method after listening to a Brew Strong episode on rinsing. I saw very little difference in the final product.

For the last few batches ive left a half inch or so of beer on the yeast, swirl it up good,  and pour into a sanitized 2 qt jar. I can't say that the final results are drastically better but its much easier and makes sense as a happy place for yeast to store short term.

I have a chunk of wy1084 in the fridge from an irish dry stout I brewed several months ago. I'm tempted to toss it but im going to let it sit till next year and pitch it just to see how well it does.