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.
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.
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.
That sounds like possible autolysis from bringing over too many dead cells.
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.
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.
I talked about the mechanism via acetyl co-A. I’m not enough of a biochemist to tell you more than that.
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.
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.
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.
+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.
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.
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.
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).