Author Topic: Overpitching - Does it matter?  (Read 8586 times)

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Re: Overpitching - Does it matter?
« Reply #15 on: May 10, 2017, 07:08:02 PM »

To put a finer point on this, I think that for certain strains (hefe's and English ale strains in particular) you can get a muted flavor profile when pitched at typical ale rates based on Mr Malty. Personally, I don't consider this over- or under-pitching, but rather targeting a different pitching rate to get the results you are looking for. I haven't found a noticible difference in attenuation within this range of pitching rates.

Agreed
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Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #16 on: May 10, 2017, 07:36:34 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

Offline blatz

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Re: Overpitching - Does it matter?
« Reply #17 on: May 10, 2017, 07:57:14 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

perhaps.  but my experience is that you need to get it in the ball park to make optimal beer.  and it isn't that hard to do so, so why not. 
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Re: Overpitching - Does it matter?
« Reply #18 on: May 10, 2017, 07:57:34 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

I can guarantee you that my own testing says pitching rate does make a difference.  They did one test with one yeast.  That's a data point, not a conclusion.  And Dr. Clayton Cone of Lallemand would disagree with "I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong."
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Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #19 on: May 10, 2017, 10:16:00 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

I can guarantee you that my own testing says pitching rate does make a difference.  They did one test with one yeast.  That's a data point, not a conclusion.  And Dr. Clayton Cone of Lallemand would disagree with "I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong."

It doesn't surprise me that yeast manufacturers would claim pitching rate is important, just as mineral water manufacturers say you have to drink 7 glasses of water a day. I've struggled to find any empirical evidence to support the claim though. Can you point to any published papers?

 Braukaiser found no difference:

http://braukaiser.com/wiki/index.php?title=Experiment_Pitching_Rate_and_Oxygenation

I'm not saying it's impossible, just that the claim is dubious. What's the proposed mechanism? The idea that yeast are somehow stressed by low cell count is clearly nonsense.

Offline bayareabrewer

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Re: Overpitching - Does it matter?
« Reply #20 on: May 11, 2017, 01:02:48 AM »
IMO overpitching is tough to do at a homebrew level.
I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

If you are making a starter within reason, it will be fine. If you are repitching bottom cropped yeast, it's easy enough to do.

I guess I say this because breweries usually have an inordinate amount of yeast lying around, and the push for faster turnover can lead some to pitch huge amounts that a homebrewer never would. Sure a homebrewer could pitch 6 packets of dry yeast into a 5 gallon batch batch of medium gravity beer, but we rarely, if ever do.

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Re: Overpitching - Does it matter?
« Reply #21 on: May 11, 2017, 01:06:44 AM »
That's what I thought at first too, but it really doesn't taste like yeast, I am thinking it is a combination of fermentation byproducts?  I have tasted it in other beers I have tried made when pitching high rates of S-04 usually.  Almost a play-doh type flavor. Thought it was a dry yeast thing but like I said I have noticed it in beers pitched with high rates of WLP001.  Maybe a overabundance of diacetyl?  I have really been at a loss for identifying it.

do you only get this when you pitch large amounts of s-04, and not all the time. I ask because I really dislike the flavor profile of this yeast.

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #22 on: May 11, 2017, 05:51:53 AM »
Here's a thought experiment on pitching rate. Let's say you have a small pack of liquid yeast with low cell count but you want to brew 5 gallons of beer. So you make a decent starter and end up with a much higher number of cells than recommended by the yeast manufacturers. You pitch the starter. Have you overpitched or underpitched?

If you brewed two identical batches, one pitched with the low-count yeast pack and the other pitched with the large starter, would they taste different? If so, how would you explain why?

In both cases, the yeast have been through a growth phase from the same original cell number and any extra esters supposedly generated by the growth are in the beer.
« Last Edit: May 11, 2017, 12:12:19 PM by charles1968 »

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Re: Overpitching - Does it matter?
« Reply #23 on: May 11, 2017, 11:56:57 AM »

I've had the opposite result from overpitching.  Because both cell growth and ester production use acetyl co-A, if you pitch too much yeast there is no need for cell growth and the co=A goes to ester production.  I get more estery beers by overpitching and less estery ones by pitching the proper amount.

Interesting.  Have you experienced across a wide variety of yeasts or certain strains in particular?  When I have over pitched WLP001 and especially S-04 I have a few times now gotten a really mealy gaminess (no idea how else to describe it) in the finished beer.

That sounds like possible autolysis from bringing over too many dead cells.

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Re: Overpitching - Does it matter?
« Reply #24 on: May 11, 2017, 12:06:50 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

This is completely false.Just because of one Brulosophy experiment does not make it an absolute. Underpitching, for instance, can cause ecessive cell growth and can cause head retetntion problems due to excess fusel alcohols. Over-pitching can certainly cause autolysis which can easily be determined by a higher pH in the finished beer (or a raise in pH in the finished beer.) Pitching rate also will affect the pH in the finished beer.

While I agree with Denny about acetyl co-A, I still find that if I over pitch my Belgians or a Koelsch in particular it affects (lowers) the ester production, especially in the case of esters I like and look for in those beers.

I have found the MrMalty calculator to be very good at calculating fresh slurries of yeast. It pairs up well with my own cell counts and viability tests. So there is no reason not to use it.

If you have a slurry older than a couple weeks old and don't have access to a microscope/hemocetometer I recommend either making a starter from that slurry or just starting fresh. One of the worse things you can do is over pitch a beer on purpose because you fear the viability is low then bring in a bunch of dead cells.

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #25 on: May 11, 2017, 12:15:53 PM »
Pitching old slurry isn't quite the same as overpitching as you're adding decomposing yeast to the wort too. I totally agree that that can spoil beer, though it takes quite a long time for autolysis to occur in my experience.

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Re: Overpitching - Does it matter?
« Reply #26 on: May 11, 2017, 02:37:31 PM »
I have a suspicion that pitching rate makes no difference to the flavour of beer. Brulosophy did a pitch rate experiment with lager and found nothing. I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong.

I can guarantee you that my own testing says pitching rate does make a difference.  They did one test with one yeast.  That's a data point, not a conclusion.  And Dr. Clayton Cone of Lallemand would disagree with "I think the theory that yeast produce different levels of esters at different cell counts is possibly wrong."

It doesn't surprise me that yeast manufacturers would claim pitching rate is important, just as mineral water manufacturers say you have to drink 7 glasses of water a day. I've struggled to find any empirical evidence to support the claim though. Can you point to any published papers?

 Braukaiser found no difference:

http://braukaiser.com/wiki/index.php?title=Experiment_Pitching_Rate_and_Oxygenation

I'm not saying it's impossible, just that the claim is dubious. What's the proposed mechanism? The idea that yeast are somehow stressed by low cell count is clearly nonsense.

I talked about the mechanism via acetyl co-A.  I'm not enough of a biochemist to tell you more than that. 
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Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #27 on: May 11, 2017, 06:44:43 PM »
The acetyl coA idea is based on some very old research. As I understand it, the logic is that actively growing yeast use up the acetyl coA and so leave less for ester production. Therefore, underpitching reduces ester synthesis and overpitching increases it. This obviously  contradicts received wisdom that underpitching raises ester production by stressing yeast.

It's ALL very sketchy. Also worth bearing in mind that many brewers pitch the starter wort, so any excess esters that might be created by the growth phase end up in the beer anyway, yet the same brewers claim the beer is cleaner tasting thanks to the large starter.

In the absence of any persuasive evidence indicating otherwise, I'm inclined to believe that pitching rate doesn't matter.

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Re: Overpitching - Does it matter?
« Reply #28 on: May 11, 2017, 07:08:29 PM »
The acetyl coA idea is based on some very old research. As I understand it, the logic is that actively growing yeast use up the acetyl coA and so leave less for ester production. Therefore, underpitching reduces ester synthesis and overpitching increases it. This obviously  contradicts received wisdom that underpitching raises ester production by stressing yeast.

It's ALL very sketchy. Also worth bearing in mind that many brewers pitch the starter wort, so any excess esters that might be created by the growth phase end up in the beer anyway, yet the same brewers claim the beer is cleaner tasting thanks to the large starter.

In the absence of any persuasive evidence indicating otherwise, I'm inclined to believe that pitching rate doesn't matter.

And my own testing says it does, so we can each do what we want.
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Re: Overpitching - Does it matter?
« Reply #29 on: May 11, 2017, 10:41:19 PM »


In the absence of any persuasive evidence indicating otherwise, I'm inclined to believe that pitching rate doesn't matter.

I agree it is less important if you are not super concerned about consistency and repeatable processes. Once you start running a brewery and brewing every day you suddenly realize very, very quickly how absolutely important pitching rates are.