Author Topic: Over pitching/under pitching experiment  (Read 9083 times)

Offline weithman5

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Re: Over pitching/under pitching experiment
« Reply #15 on: October 12, 2012, 08:47:39 AM »
i would think this would work well from one bucket to another as the pressure would not likely be as much a concern in terms of breaking a carboy. the active ferment would have the higher pressure and discharge to the lower pressure system.
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Re: Over pitching/under pitching experiment
« Reply #16 on: October 12, 2012, 09:28:09 AM »
If I were going to do it, I would just put the hose in the top of the carboy and cover it all with foil.  It's not gonna be on there for long, you don't want to over pitch the receiving carboy either.  I'd say an hour would be more than enough.

For a bucket I wouldn't do this.  You'd be better to top crop and be done with it in 5 minutes.

Offline dimik

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Re: Over pitching/under pitching experiment
« Reply #17 on: October 15, 2012, 06:47:32 AM »
Jason did a nice experiment about that a while back. Take a look:
http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/
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Offline kylekohlmorgen

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Re: Over pitching/under pitching experiment
« Reply #18 on: October 16, 2012, 06:27:01 AM »
Jason did a nice experiment about that a while back. Take a look:
http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

This is a good read - make sure you get to the bottom for Garrett Oliver's advice!
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Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #19 on: October 19, 2012, 11:44:11 PM »
Jason did a nice experiment about that a while back. Take a look:
http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

This is a good read - make sure you get to the bottom for Garrett Oliver's advice!
My only issue with what he says is this
Quote
Conversely, overpitching ages the culture – fewer daughters, over time, leaves you with a lot of battle-weary scarred cells with inflexible membranes that are no longer at their best. And not as many young, scar-free new cells.
If there are fewer daughters because the yeast aren't dividing as much, then the mothers will have fewer scars - the scars come from budding which is why they are called bud scars.  He is really talking about two different kinds of yeast aging, chronological and replicative.

There will be just as many scar free cells when you over pitch vs. under pitch - half.  1/4 will have 1 scar, 1/8 will have 2 scars, 1/16 will have 3 scars, etc.

His point is still fair though - older cells don't perform as well.
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Re: Over pitching/under pitching experiment
« Reply #20 on: October 20, 2012, 05:17:27 AM »
There will be just as many scar free cells when you over pitch vs. under pitch - half.  1/4 will have 1 scar, 1/8 will have 2 scars, 1/16 will have 3 scars, etc.

This is exactly what I said when Jason pointed me to Garett's comment after I commented in the surprisingly low gravity of the underpitched beer. He didn't let me disagree with Garett and I ended up researching the topic on-line. I found that a yeast culture will have the distribution Tom mentioned unless sedimentation creates an uneven age distribution. Older cells are bigger and heavier and as a result will settle first. But that doesn't apply here.

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Offline dimik

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Re: Over pitching/under pitching experiment
« Reply #21 on: October 21, 2012, 09:43:29 PM »
I've had my share of disagreements with Jason (purely healthy scientific discussion) and I respect his results and observations even if I disagree with them sometimes.
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Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #22 on: October 21, 2012, 11:29:48 PM »
There will be just as many scar free cells when you over pitch vs. under pitch - half.  1/4 will have 1 scar, 1/8 will have 2 scars, 1/16 will have 3 scars, etc.

This is exactly what I said when Jason pointed me to Garett's comment after I commented in the surprisingly low gravity of the underpitched beer. He didn't let me disagree with Garett and I ended up researching the topic on-line. I found that a yeast culture will have the distribution Tom mentioned unless sedimentation creates an uneven age distribution. Older cells are bigger and heavier and as a result will settle first. But that doesn't apply here.

Kai
He didn't let you disagree? ::)  That's lame, I don't know Garrett but I imagine he would have listened to your point.  The fact that Jason wouldn't listen doesn't speak well for his scientific mindset.  In the end I guess it was worth it because you proved something to yourself.  Did you ever go back to him with evidence, or did you decide it wasn't worth your time?
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Re: Over pitching/under pitching experiment
« Reply #23 on: October 22, 2012, 05:20:55 AM »
His point is still fair though - older cells don't perform as well.

How old is "older?" Would that happen in a single batch of beer, or are you talking about repitching?
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Re: Over pitching/under pitching experiment
« Reply #24 on: October 22, 2012, 07:03:19 AM »
Gonna keg this today and keep some for re-pitching.  Based on this, would it be better to keep the yeast from the underpitched or the over pitched for a porter (WLP007).  Gonna keg today and brew tomorrow.
Will update with FG and comments later.

Offline davidgzach

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Re: Over pitching/under pitching experiment
« Reply #25 on: October 22, 2012, 09:39:20 AM »
Gonna keg this today and keep some for re-pitching.  Based on this, would it be better to keep the yeast from the underpitched or the over pitched for a porter (WLP007).  Gonna keg today and brew tomorrow.
Will update with FG and comments later.

I would say overpitched but can't wait to hear other responses on that.

Dave
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Re: Over pitching/under pitching experiment
« Reply #26 on: October 22, 2012, 09:41:15 AM »
Quote
How did you release the pressure?  I'm picturing a blowoff tube from one grommet to another.  If that is the only outlet for each, how did you account for the change in pressure going in to the underpitched batch?  Or am I missing something obvious?  Happens to me sometimes..... ???

Carboy caps would work, methinks. Airlock in one hole and a tube in the other?

That makes sense.  There has to be a way to relieve the pressure from the combined system.

Dave
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Re: Over pitching/under pitching experiment
« Reply #27 on: October 22, 2012, 09:44:21 AM »
If I were going to do it, I would just put the hose in the top of the carboy and cover it all with foil.  It's not gonna be on there for long, you don't want to over pitch the receiving carboy either.  I'd say an hour would be more than enough.

For a bucket I wouldn't do this.  You'd be better to top crop and be done with it in 5 minutes.

That makes sense too!
Dave Zach

Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #28 on: October 22, 2012, 11:07:36 AM »
His point is still fair though - older cells don't perform as well.

How old is "older?" Would that happen in a single batch of beer, or are you talking about repitching?
This is a more complicated question than it may seem :)

There are two ways that scientists talk about how old a yeast cell is - replicative lifespan, and chronological lifespan.  Neither of these is investigating the health of cells that are fermenting without dividing over time so the results may not be directly applicable.  With that caveat . . .

The replicative lifespan of yeast is roughly 25, meaning it can divide 25 times before it stops.  I am making a broad generalization here because it is strain specific.  This number comes from my old labs' work on strains BY4741 and BY4742, common lab strains that are the opposite mating types but otherwise the same.  I never did lifespans on any brewing strains because it is a huge pain and requires a dissecting microscope - basically, you plate cells, use the dissector to move individual cells to their own spot on the plate, then incubate for 2-4 hours.  Then you go back to the scope and pull the daughter cell away from the mother, put it in a garbage area, and count that as one.  You do this again and again until the mother stops dividing.  You can't let it grow too long or it can become hard to tell the mother from the daughter, or you may count the daughter's daughter as a daughter of the mother.  It is very labor intensive - we had a group of people who did nothing but pick daughters all day long because they went through the entire yeast deletion collection, ~5000 strains that are the same as above but with a single gene deleted, plus controls, etc.

Anyway, older mothers don't perform as well as younger mothers.  Daughters of older mothers don't perform as well as daughters of younger mothers, although they recover after a couple of generations.  I believe in this case "perform" means grow, they were not checking for fermentation performance or anything like that.

The other kind of aging, chronological aging, is quite a bit different.  In this case, a strain is grown to stationary phase and let sit for some period of time and then tested to see if it will grow again.  Again, the entire yeast deletion collection was screened by a guy I know (much easier for one person to do).  The normal strain was 50% viable at ~2 weeks.  This is misleading though, because the media used affected the results.  Another guy I know showed later that the effect was almost entirely due to pH, and more specifically the ability of the strain to withstand acetic acid.

So, will this happen in a single batch of beer?  The scales for a single fermentation are too short to apply to either one of these sets of data.  If you are constantly repitching replicatively older cells I think you will notice in your fermentations.  But isolating replicatively older cells is a real pain, labs have spent years trying to figure out how to enrich a culture for older mothers.  If you are harvesting from a carboy don't worry about it.  From a conical, as long as you are blowing out the first bit to get rid of the trub, don't worry about it.

If you are constantly over pitching and re-pitching from an over pitched batch, you may be increasing the chronological lifespan of the culture.  However, the data there are not good enough to give a definitive answer.  We know there are pH effects, but the final pH of the research media is not in the same range as beer, the finished culture ends up much lower than beer (under 3) while the buffered cultures they used are higher than beer (pH = 6).  And they didn't do anything with serial repitching of these cultures.

I think I typed all of this stuff and didn't answer the question.  Bottom line - if you follow standard practices you should be fine.  Make starters, aerate well, pitch in the suggested range, etc.  If a culture gets old by sitting for a while, refresh it in a starter.  Don't worry about bud scars.
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Offline dimik

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Re: Over pitching/under pitching experiment
« Reply #29 on: October 22, 2012, 06:43:36 PM »
His point is still fair though - older cells don't perform as well.

How old is "older?" Would that happen in a single batch of beer, or are you talking about repitching?
This is a more complicated question than it may seem :)

There are two ways that scientists talk about how old a yeast cell is - replicative lifespan, and chronological lifespan.  Neither of these is investigating the health of cells that are fermenting without dividing over time so the results may not be directly applicable.  With that caveat . . .

The replicative lifespan of yeast is roughly 25, meaning it can divide 25 times before it stops.  I am making a broad generalization here because it is strain specific.  This number comes from my old labs' work on strains BY4741 and BY4742, common lab strains that are the opposite mating types but otherwise the same.  I never did lifespans on any brewing strains because it is a huge pain and requires a dissecting microscope - basically, you plate cells, use the dissector to move individual cells to their own spot on the plate, then incubate for 2-4 hours.  Then you go back to the scope and pull the daughter cell away from the mother, put it in a garbage area, and count that as one.  You do this again and again until the mother stops dividing.  You can't let it grow too long or it can become hard to tell the mother from the daughter, or you may count the daughter's daughter as a daughter of the mother.  It is very labor intensive - we had a group of people who did nothing but pick daughters all day long because they went through the entire yeast deletion collection, ~5000 strains that are the same as above but with a single gene deleted, plus controls, etc.

Anyway, older mothers don't perform as well as younger mothers.  Daughters of older mothers don't perform as well as daughters of younger mothers, although they recover after a couple of generations.  I believe in this case "perform" means grow, they were not checking for fermentation performance or anything like that.

The other kind of aging, chronological aging, is quite a bit different.  In this case, a strain is grown to stationary phase and let sit for some period of time and then tested to see if it will grow again.  Again, the entire yeast deletion collection was screened by a guy I know (much easier for one person to do).  The normal strain was 50% viable at ~2 weeks.  This is misleading though, because the media used affected the results.  Another guy I know showed later that the effect was almost entirely due to pH, and more specifically the ability of the strain to withstand acetic acid.

So, will this happen in a single batch of beer?  The scales for a single fermentation are too short to apply to either one of these sets of data.  If you are constantly repitching replicatively older cells I think you will notice in your fermentations.  But isolating replicatively older cells is a real pain, labs have spent years trying to figure out how to enrich a culture for older mothers.  If you are harvesting from a carboy don't worry about it.  From a conical, as long as you are blowing out the first bit to get rid of the trub, don't worry about it.

If you are constantly over pitching and re-pitching from an over pitched batch, you may be increasing the chronological lifespan of the culture.  However, the data there are not good enough to give a definitive answer.  We know there are pH effects, but the final pH of the research media is not in the same range as beer, the finished culture ends up much lower than beer (under 3) while the buffered cultures they used are higher than beer (pH = 6).  And they didn't do anything with serial repitching of these cultures.

I think I typed all of this stuff and didn't answer the question.  Bottom line - if you follow standard practices you should be fine.  Make starters, aerate well, pitch in the suggested range, etc.  If a culture gets old by sitting for a while, refresh it in a starter.  Don't worry about bud scars.

THAT, Sir, was probably the most interesting thing I've ever read on any brewing forum. Very nice!
Check out BKYeast for my yeast ranching adventures and home lab!

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