Author Topic: Overpitching - Does it matter?  (Read 10526 times)

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #30 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.
« Last Edit: May 12, 2017, 11:57:42 AM by charles1968 »

Big Monk

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Re: Overpitching - Does it matter?
« Reply #31 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.

Offline HoosierBrew

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Re: Overpitching - Does it matter?
« Reply #32 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.
Jon H.

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Re: Overpitching - Does it matter?
« Reply #33 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.

Offline HoosierBrew

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Re: Overpitching - Does it matter?
« Reply #34 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.
Jon H.

Offline zwiller

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Re: Overpitching - Does it matter?
« Reply #35 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. 
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Offline brewinhard

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Re: Overpitching - Does it matter?
« Reply #36 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?

Offline Philbrew

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Re: Overpitching - Does it matter?
« Reply #37 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.
« Last Edit: May 13, 2017, 02:12:55 AM by Philbrew »
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Offline majorvices

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Re: Overpitching - Does it matter?
« Reply #38 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.

Offline WattsOnTap

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Re: Overpitching - Does it matter?
« Reply #39 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).

Offline chumley

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Re: Overpitching - Does it matter?
« Reply #40 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.

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #41 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     

Big Monk

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Re: Overpitching - Does it matter?
« Reply #42 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 

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #43 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.

Offline charles1968

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Re: Overpitching - Does it matter?
« Reply #44 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:



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"