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General Category => Yeast and Fermentation => Topic started by: WattsOnTap on May 10, 2017, 03:06:18 PM

Title: Overpitching - Does it matter?
Post by: WattsOnTap on May 10, 2017, 03:06:18 PM
I understand there are ideal cell counts and that you can, technically, overpitch yeast for a given batch.  Does it really matter if you overpitch?  And, if so, what would be the effects?  Is there a tolerance range?

I recognize I have underpitched batches in the past, and now build a starter for nearly every brew.  I'm just wondering if it's possible that I'm over-correcting.
Title: Re: Overpitching - Does it matter?
Post by: bayareabrewer on May 10, 2017, 03:14:56 PM
IMO overpitching is tough to do at a homebrew level.
Title: Re: Overpitching - Does it matter?
Post by: Stevie on May 10, 2017, 03:20:15 PM
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.
Title: Re: Overpitching - Does it matter?
Post by: jrdatta on May 10, 2017, 03:34:15 PM
Absolutely possible to overpitch a homebrew batch (especially with dry yeast).  But it is strain and style dependent. Some strains need higher pitch rates some need lower to get the right ester profile.  So you really need to fit your pitch rates to your beer.  IE a British mild or bitter usually turns out better with a much lower pitch rate than we would use for an American Pale ale where we want a really clean highly attenuated profile.
Title: Re: Overpitching - Does it matter?
Post by: denny on May 10, 2017, 03:49:19 PM
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'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.
Title: Re: Overpitching - Does it matter?
Post by: jrdatta on May 10, 2017, 03:59:49 PM

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.
Title: Re: Overpitching - Does it matter?
Post by: dmtaylor on May 10, 2017, 05:08:02 PM
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.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.
Title: Re: Overpitching - Does it matter?
Post by: Todd H. on May 10, 2017, 05:13:20 PM
Are you sure that "mealy gaminess" isn't just the taste and texture of too much yeast, if indeed you end up pitching so much that no cell division occurs?  I mean the taste and feeling of the cells, not by-products thereof.

Biochemically speaking, what Denny says makes sense.

I've noticed on forums that a lot of people use the term ester to refer to any flavour compound the yeast produce, not just literally esters.  Maybe that's where some of the confusion lies.

BTW, specific to this discussion, I've seen papers indicating that overpitching can lead to more diacetyl production.  Of course, there are also more cells to clean up that diacetyl, so maybe that doesn't actually matter?

WattsOnTapp, if you assume that the saturation point of your starter wort and your beer wort are the same, then a 1 liter starter should divide roughly 4-5 times in your beer.  On a cell number level, that translates into 16-32x more cells than in your starter.  So using a normal sized starter it probably is impossible to overpitch into 5 gallons of beer.  Pitching onto a fresh yeast cake will net you close to zero cell division and would be considered an overpitch, I imagine.
Title: Re: Overpitching - Does it matter?
Post by: jrdatta on May 10, 2017, 05:27:29 PM
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.
Title: Re: Overpitching - Does it matter?
Post by: blatz on May 10, 2017, 05:56:00 PM
theres been a few times, maybe 4, that I used the mrmalty yeast calculator for repitching a lager slurry that was older (3-5 weeks) and questioned that it seemed like wayyyy too much slurry, but I followed it anyway. 

each of those beers ended up with some level of acetylaldehyde.

is it a correlation or a coincidence?  I'm not sure - I can't recall any other beers I've had the green apple monster rear its ugly head at otherwise, despite almost 240 batches. 
Title: Re: Overpitching - Does it matter?
Post by: denny on May 10, 2017, 05:56:13 PM
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.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA
Title: Re: Overpitching - Does it matter?
Post by: HoosierBrew on May 10, 2017, 05:59:51 PM
As for lagers, overpitching is theoretically possible. Also highly unlikely IMO. I do believe that overpitching ales can give you overly clean beers and that underpitching can (can, not will) increase esters. I like a clean profile on American ales and couldn't care less if it's a technical overpitch, where I pay more attention on Belgian styles to the amount of yeast (together with temp profile) I pitch. I also disagree that pitching rate has zero role in attenuation.
Title: Re: Overpitching
Post by: dmtaylor on May 10, 2017, 06:06:06 PM
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.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

"The word Imola is of Roman origin and means 'over there, down there'. It refers to the view enjoyed by the people looking down on the inhabited zone from the valley at midday."

--
Dave Taylor... arguing with Denny since 2003.
https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ (https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ)
Title: Re: Overpitching - Does it matter?
Post by: erockrph on May 10, 2017, 06:11:45 PM
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.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

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.
Title: Re: Overpitching
Post by: denny on May 10, 2017, 07:07:20 PM
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.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

"The word Imola is of Roman origin and means 'over there, down there'. It refers to the view enjoyed by the people looking down on the inhabited zone from the valley at midday."

--
Dave Taylor... arguing with Denny since 2003.
https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ (https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ)

:)
Title: Re: Overpitching - Does it matter?
Post by: denny 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
Title: Re: Overpitching - Does it matter?
Post by: charles1968 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.
Title: Re: Overpitching - Does it matter?
Post by: blatz 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. 
Title: Re: Overpitching - Does it matter?
Post by: denny 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."
Title: Re: Overpitching - Does it matter?
Post by: charles1968 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.
Title: Re: Overpitching - Does it matter?
Post by: bayareabrewer 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.
Title: Re: Overpitching - Does it matter?
Post by: bayareabrewer 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.
Title: Re: Overpitching - Does it matter?
Post by: charles1968 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.
Title: Re: Overpitching - Does it matter?
Post by: majorvices 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.
Title: Re: Overpitching - Does it matter?
Post by: majorvices 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.
Title: Re: Overpitching - Does it matter?
Post by: charles1968 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.
Title: Re: Overpitching - Does it matter?
Post by: denny 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. 
Title: Re: Overpitching - Does it matter?
Post by: charles1968 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.
Title: Re: Overpitching - Does it matter?
Post by: denny 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.
Title: Re: Overpitching - Does it matter?
Post by: majorvices 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.
Title: Re: Overpitching - Does it matter?
Post by: charles1968 on May 12, 2017, 05:37:36 AM


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.

I've no doubt it matters in a brewery setting, but that's more about ensuring a consistent and predictable fermentation time and process rather than controlling levels of esters.

There is published research on effect of pitching rate on esters but the results show minor effects and are inconclusive. This is from a 2007 paper in the Journal of the Institute of Brewing:

The volatile esters determined in this study were ethyl acetate, isoamyl acetate (3-methylbutyl acetate), ethyl butyrate, ethyl hexanoate (ethyl caproate) and ethyl oc-tanoate (ethyl caprylate). The pitching rate had no clear effect on the concentrations of esters with the exception of isoamyl acetate. Pitching at the lower rates produced a higher concentration of isoamyl acetate. The results ob-tained for isoamyl acetate in this study are in agreement with the findings of Anderson and Kirsop2, Edelen et al.7 and Suihko et al.16, but for ethyl acetate the results are in disagreement with the findings of Anderson and Kirsop2 and Suihko et al.16


Isoamyl acetate is the banana ester. This study got less of it at higher pitch rates. Starters were not pitched - the yeast was centrifuged and washed before pitching. Any differences in flavour associated with pitch rate would presumably disappear if a starter was pitched with the yeast.
Title: Re: Overpitching - Does it matter?
Post by: Big Monk on May 12, 2017, 12:24:00 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.

I've no doubt it matters in a brewery setting, but that's more about ensuring a consistent and predictable fermentation time and process rather than controlling levels of esters.

There is published research on effect of pitching rate on esters but the results show minor effects and are inconclusive. This is from a 2007 paper in the Journal of the Institute of Brewing:

The volatile esters determined in this study were ethyl acetate, isoamyl acetate (3-methylbutyl acetate), ethyl butyrate, ethyl hexanoate (ethyl caproate) and ethyl oc-tanoate (ethyl caprylate). The pitching rate had no clear effect on the concentrations of esters with the exception of isoamyl acetate. Pitching at the lower rates produced a higher concentration of isoamyl acetate. The results ob-tained for isoamyl acetate in this study are in agreement with the findings of Anderson and Kirsop2, Edelen et al.7 and Suihko et al.16, but for ethyl acetate the results are in disagreement with the findings of Anderson and Kirsop2 and Suihko et al.16


Isoamyl acetate is the banana ester. This study got less of it at higher pitch rates. Starters were not pitched - the yeast was centrifuged and washed before pitching. Any differences in flavour associated with pitch rate would presumably disappear if a starter was pitched with the yeast.

I've been doing quite a bit of research into this topic as I am currently starting some trials with a "pitch cool and let rise" fermentation profile with no temp control. Some of the things I have been researching are the other "levers" you can pull, i.e. Pitch rate, gravity, attenuation, wort composition, etc. and one of the things that may be more important than pitch rates in general, is how individual strains respond differently to different pitch rates and how that affects their natural tendencies toward esters.
Title: Re: Overpitching - Does it matter?
Post by: HoosierBrew on May 12, 2017, 01:23:37 PM
I agree, Derek. There's no 'one size fits all' statement about every strain with respect to pitching rates. Strains behave differently.
Title: Re: Overpitching - Does it matter?
Post by: Big Monk on May 12, 2017, 01:37:15 PM
I agree, Derek. There's no 'one size fits all' statement about every strain with respect to pitching rates. Strains behave differently.

The strain is ultimately the deciding factor on how the fermentation will precede in the face of the many variables. With that said, those variables, i.e. Pitch rate, temperature, aeration, gravity, attenuation, wort composition, etc. HAVE been studied extensively and there is a ton of information out there about how those variables, taken separately or combined with others, affect fermentation.
Title: Re: Overpitching - Does it matter?
Post by: HoosierBrew on May 12, 2017, 01:50:07 PM
I agree, Derek. There's no 'one size fits all' statement about every strain with respect to pitching rates. Strains behave differently.

The strain is ultimately the deciding factor on how the fermentation will precede in the face of the many variables. With that said, those variables, i.e. Pitch rate, temperature, aeration, gravity, attenuation, wort composition, etc. HAVE been studied extensively and there is a ton of information out there about how those variables, taken separately or combined with others, affect fermentation.


Agreed.
Title: Re: Overpitching - Does it matter?
Post by: zwiller on May 12, 2017, 03:43:07 PM
+2;  I will add that I have done some pretty crazy things over the years such as pitching the dregs of a single bottle into 5G and racking an average strength wort onto a whole yeast cake and good beer still resulted.  That said, I personally believe pitch rate is a factor with expressive strains but not to the extent some suggest. 
Title: Re: Overpitching - Does it matter?
Post by: brewinhard on May 12, 2017, 06:17:27 PM
+2;  I will add that I have done some pretty crazy things over the years such as pitching the dregs of a single bottle into 5G and racking an average strength wort onto a whole yeast cake and good beer still resulted. 

Ha.  The good old days. Everything seemed so much easier, didn't it?
Title: Re: Overpitching - Does it matter?
Post by: Philbrew on May 13, 2017, 02:07:00 AM
+2;  I will add that I have done some pretty crazy things over the years such as pitching the dregs of a single bottle into 5G and racking an average strength wort onto a whole yeast cake and good beer still resulted. 

Ha.  The good old days. Everything seemed so much easier, didn't it?
And it still is, if you don't let yourself get taken in by the siren song of promised perfection.  RDWHAHB

Hey, it's a hobby.  Have fun.  Though fun, like beauty, is in the eye of the beholder/doer.
Title: Re: Overpitching - Does it matter?
Post by: majorvices on May 13, 2017, 11:51:05 AM
I have to admit I brew homebrew sized batches (for fun and for experiments and for a special "club" we host once a month at the brewery) about 4 times a week, if not more. I almost never make a starter unless the yeast is not fresh. I pull fresh yeast directly from 60 bbl conical fermentor into plastic measuring cups and "guestimate" how much feels right. I'll swirl around the slurry in the bottom of a carboy and pour a bit of yeast directly into another carboy using intuition on my "pitching rate". I haven't had a bad batch in a long time.

OTOH I have brewed for over 20 years and I have brewed well over 1,500 batches just in the last 6 years so I have a pretty good "feel" on what works and what doesn't. For new brewers, the pitching rate guidelines are not a bad idea to use. I don't think you will ruin a batch, necessarily, by pitching directly on a yeast cake or over or under pitching. But I still think it is  a much better idea to get as close as you can to pitching the right amount of yeast. But, as I can attest, seat of the pants intuition works. Especially if you have the experience under your belt to guide you.
Title: Re: Overpitching - Does it matter?
Post by: WattsOnTap on May 14, 2017, 01:17:02 AM
Didn't expect to get such a response to my question.  I feel like some big knowledge bombs were dropped in here, thank you all!

Seems the stress my yeast are experiencing (judging comments on a few recent brews) probably isn't from what might be just the slightest (on homebrew scale) overpitching.  Need to take a look at how I could do temp control better, most likely, or when I pitch starters (when I do them).
Title: Re: Overpitching - Does it matter?
Post by: chumley on May 14, 2017, 11:23:10 PM
Out of curiosity - Denny, what yeast strains have you encountered increased ester production when overpitching?

My experience, as a lazy and cheap brewer who tends to use yeast cakes over and over, is that of the others who have posted here.  That is, English and weissbier strains benefit from underpitching to achieve the ester character in the final product.  Having known you on various forums for many years, Denny, I am fairly certain that your experience on overpitching is not drawing on British bitters or hefewieizens.  :)

In fact, this subject seems to come up with some regularity, and as far as I am aware of, only you and Dr. Cone have had excessive ester production resulting from overpitching.  Which makes me wonder if it is 1450 thing. Or maybe an APA/IPA thing, the hop debris in the trub is causing some effect.

My experience:  besides the above, overpitching results in greater attenuation, especially with ale yeast.  Lager yeasts, I think you can pitch and pitch again on top of yeast cakes with no adverse affects, as long as you keep it clean.  I have gone up to 7 times with pilsner yeasts with no noticeable off-tastes.
Title: Re: Overpitching - Does it matter?
Post by: charles1968 on May 15, 2017, 07:52:30 AM

Here's a bit more research suggesting pitching rate has little effect on flavour:

Appl Microbiol Biotechnol 2009, Impact of pitching rate on yeast fermentation performance and beer flavour.
https://www.ncbi.nlm.nih.gov/pubmed/19018524

From abstract:

The influence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate. These results demonstrate that most aspects of the yeast physiology and flavour balance are not significantly or negatively affected when the pitching rate is changed     
Title: Re: Overpitching - Does it matter?
Post by: Big Monk on May 15, 2017, 12:24:28 PM

Here's a bit more research suggesting pitching rate has little effect on flavour:

Appl Microbiol Biotechnol 2009, Impact of pitching rate on yeast fermentation performance and beer flavour.
https://www.ncbi.nlm.nih.gov/pubmed/19018524

From abstract:

The influence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate. These results demonstrate that most aspects of the yeast physiology and flavour balance are not significantly or negatively affected when the pitching rate is changed     

I think it's important to make the distinction that while pitching rate alone may not affect flavor as much as people think, it is related to yeast growth and yeast growth is related to other contributing variables in fermentation, i.e. Aeration, etc.

So it's simultaneously true and not true to say pitching rate doesn't matter 
Title: Re: Overpitching - Does it matter?
Post by: charles1968 on May 15, 2017, 12:49:37 PM

Here's a bit more research suggesting pitching rate has little effect on flavour:

Appl Microbiol Biotechnol 2009, Impact of pitching rate on yeast fermentation performance and beer flavour.
https://www.ncbi.nlm.nih.gov/pubmed/19018524

From abstract:

The influence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate. These results demonstrate that most aspects of the yeast physiology and flavour balance are not significantly or negatively affected when the pitching rate is changed     

I think it's important to make the distinction that while pitching rate alone may not affect flavor as much as people think, it is related to yeast growth and yeast growth is related to other contributing variables in fermentation, i.e. Aeration, etc.

So it's simultaneously true and not true to say pitching rate doesn't matter

Yes I agree oxygen complicates the picture.
Title: Re: Overpitching - Does it matter?
Post by: charles1968 on May 15, 2017, 12:55:44 PM
Here are the results from another published paper. This paper found a slight increase in ester production with higher pitch rate:

(http://i66.tinypic.com/2q3r5vp.png)

A near doubling of pitch rate causes a 3% rise in one ester and 7% rise in another. Perhaps it's enough to have a significant effect on flavour but changes this small could equally be a measurement error.

Institute of Brewing & Distilling, "The effect of pitching rate on fermentation, maturation and flavour compounds of beer produced on an industrial scale"

Title: Re: Overpitching - Does it matter?
Post by: Joe Sr. on May 15, 2017, 06:58:21 PM
Effects of pitching rate aside, I'll go back to post #2 and agree with bayareabrewer.

On the homebrew level, it's pretty hard to overpitch.  You need to do something deliberate such as pitching an entire yeast cake, growing a huge starter, or pitching many packs of yeast.

As far as does it matter?  As Keith pointed out, pitching rate matters most with respect to consistency.  All other things being equal, you'll need to pitch a similar amount of yeast to consistently repeat the same beer.

At the homebrew level, such consistency isn't always an issue.  It is for some of us.  Not all of us.
Title: Re: Overpitching - Does it matter?
Post by: brewmaster on May 25, 2017, 06:01:00 PM
Overpitching can result in yeast autolysis but is most evident if you are reusing your pitching yeast.  If reusing yeast and overpitching in each batch there will be very few new generations of yeast created, and the older generations of yeast will eventually become tired and sluggish.