# S04 (and others) When is it overpitch with negative consequences?

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#### Kristoffer84

##### Active Member
Hello,
i would like to throw in a question concerning overpitch. Many websites or forum descripe the fact that overpitch is there and that it could be not good but wont happen easy etc etc... BUT its not saying WHEN it is an overpitch and also an overpitch with negative consequences like and empty taste.... etc.

So lets take the good kown S04. Every package contains 11,5g of yeast and Fermentis says that those 11,5 g are enough for 20 Liters of Beer with under 14% Plato?. They tested that of course in their standard wort which is 100% base malt and at a certain temperature of 20 Celsius.
Lets say i take two packages so 23g on 20 Liters of lets say 12% Plato, will it be an overpitch allready, an overpitch with negative consequences or are we still good? When will it start to be bad? 3 times or even more?

And another thing is related to that by having info on the number of yeast cells per package. The well known yeast pitch calculator of brewersfriend (Yeast Pitch Rate and Starter Calculator - Brewer's Friend) has some hints on that by saying:
• Mr.Malty says that dry yeast contains 20 billion cells per gram. Unfortunately we could not find a reference to a study that supports that number.
• From the manufacturers:
• Fermentis: > 6B cells/gram for US-05 and S-04.
• Danstar: > 5B cells/gram for Nottingham yeast.
• These numbers sound conservative and do not match with the study referenced above. According to our pitching calculator, with dry yeast, using the mfg's number of 6B cells/g, to hit a pitch rate of 0.75 (M cells / ml / ° P) for a 5 gallon batch @1.050 would require 3x 11g packs!

Its also stated that Fermentis guarantees 6B Cells but mostly its 20B cells/g.

So if we go and say its 15B cells/g and a classic 12% Plato brew needs 189B cells we would still need the 2 packages open to get enough cells. BUT we dont take in that calculation that the yeast will grow once in the wort. So after all a pretty complicated thing.

What are you guys thinking on that topic? Or maybe some of you had also experienced overpitch oder maybe even got sources about that overpitch topic...

I’m not sure I believe overpitching is even a thing, or even a thing at homebrew scales. I’ve dumped new batches right on top of the yeast cakes from old batches. I’ve put 11 g of dry yeast into a one-gallon batch. Never had anything in the results that plausibly connected to an overpitch.

I’m not a micro biologist so I apologize for the lack of depth here.

For a single batch or limited reuse, I don’t think the questions you ask have a definite line where you cross from under pitch to ideal pitch to over pitch. I think of it as a continuum that can be taste and performance driven. Your under pitch might be someone else’s ideal or over pitch. Pitching rates are another means of adding variation to the end product.

If you’re planning to reuse for several generations, I think “over pitching” is where you begin encountering more undesirable performance. One of the things that happens with over pitching is that it doesn’t generate very much new cell growth during the growth phase. Over time, this contributes to an older overall colony (not sure if that’s the correct term) which can be detrimental.

I think the best thing to do on a homebrew scale is to find the flavors and performance that best suits your taste and brewing. If you plan to keep yeast for many generations then shooting for an “ideal” pitch rate might benefit you.

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I have overpitched S04 and it goes crazy and blows out the top.

Generally speaking, the pitching numbers are not specific as one would think. It's more of a range you aiming for. An overpitch is better than an underpitch. The best thing you can do is to keep good notes and go for a more conservative number in regard to cells per gram. I have never believed there are 20 billion cells per gram, but I also think 6 billion cells per gram is too low. I generally run with cell count of dry yeast as somewhere around 12 billion cells per gram.

I'm thinking at the home brew level with home brew quantities you don't need to worry about overpitching.

You do need to make sure you pitch enough yeast. What is enough yeast? Well that's the argument. But I'd say enough is what ever makes you happy as long as it is at least the amount that gets you a successful batch of beer to drink.

If you don't know any better by your own experience, then do at least what the maker of the yeast you use suggests.

If your fermenter blows it's top, then that's not so much the amount of yeast you used, but inadequate FV and allowances for the Krausen. More headspace, larger diameter blow off tubes instead of a airlock. And other things.

@Kristoffer84, this is a great post with a lot of information and questions, so I will respond as best as I can.

First of all, I am not sure what exactly are the consequences of overpitching, because I myself have never experimented heavily with pitch rates yet. If anything, I’ve experimented far more with underpitching than overpitching. I typically use 1/4 to 1/2 of a sachet of dried yeast for 5 gallons, and only 1 full pack for high gravity lagers. The other millions of homebrewers out there who pitch multiple packs routinely for really no good reason IMO should be better equipped to respond as to whether or not overpitching might be problematic.

Quantitatively, I suggest we can and should agree with MrMalty that a dry pack contains 20B cells/gram, because he wrote the book on Yeast and should know. We don’t need further validation -- he is his own reference, and the experience of many suggests no issues believing this. I have been involved with discussions about this many years ago (see link below), and resolved to only pitch 1/4 to 1/2 sachet from then on (as I stated above) based on this reference. As far as I can tell I have not experienced any “underpitching” problems.

https://www.homebrewersassociation.org/forum/index.php?topic=27438.msg358328#msg358328
What should we do with the remaining yeast from a partial sachet? I fold over the corner and tuck it back into the refrigerator. Again… I am not aware that this is causing any problems.

Dry yeast keeps for many years in refrigeration. Recently I’ve seen people I respect saying they wouldn’t hesitate to use dry yeast stored for 10+ years in refrigeration, and neither would I.

Yeast manufacturers are in the business of selling yeast, of course, so there is no advantage to them providing realistic viability numbers. Underestimating their viability results in them selling more yeast! In general, I trust manufacturer data about as far as I can throw a sachet -- not very far.

I wouldn’t worry about overpitching, as far as it might affect beer quality. Personally I am more concerned about wasting money. And I think, about 9 times out of 10, homebrewers are overpitching their dried yeasts and thus wasting their money unnecessarily. If you want to overpitch, go right ahead, it’s not my money so I don’t care.

With overpitching there isn't much of growth phase. Many flavors come from the growth phase. You will end up with an older yeast population. If your pitching on a healthy yeast cake all should be fine.

I like to pitch at more predictable rates for consistency.

@Kristoffer84, this is a great post with a lot of information and questions, so I will respond as best as I can.

First of all, I am not sure what exactly are the consequences of overpitching, because I myself have never experimented heavily with pitch rates yet. If anything, I’ve experimented far more with underpitching than overpitching. I typically use 1/4 to 1/2 of a sachet of dried yeast for 5 gallons, and only 1 full pack for high gravity lagers. The other millions of homebrewers out there who pitch multiple packs routinely for really no good reason IMO should be better equipped to respond as to whether or not overpitching might be problematic.

Quantitatively, I suggest we can and should agree with MrMalty that a dry pack contains 20B cells/gram, because he wrote the book on Yeast and should know. We don’t need further validation -- he is his own reference, and the experience of many suggests no issues believing this. I have been involved with discussions about this many years ago (see link below), and resolved to only pitch 1/4 to 1/2 sachet from then on (as I stated above) based on this reference. As far as I can tell I have not experienced any “underpitching” problems.

https://www.homebrewersassociation.org/forum/index.php?topic=27438.msg358328#msg358328
What should we do with the remaining yeast from a partial sachet? I fold over the corner and tuck it back into the refrigerator. Again… I am not aware that this is causing any problems.

Dry yeast keeps for many years in refrigeration. Recently I’ve seen people I respect saying they wouldn’t hesitate to use dry yeast stored for 10+ years in refrigeration, and neither would I.

Yeast manufacturers are in the business of selling yeast, of course, so there is no advantage to them providing realistic viability numbers. Underestimating their viability results in them selling more yeast! In general, I trust manufacturer data about as far as I can throw a sachet -- not very far.

I wouldn’t worry about overpitching, as far as it might affect beer quality. Personally I am more concerned about wasting money. And I think, about 9 times out of 10, homebrewers are overpitching their dried yeasts and thus wasting their money unnecessarily. If you want to overpitch, go right ahead, it’s not my money so I don’t care.
Thank you m8 for the answer. I guess i forgot to explain why i asked that question at all. I normaly make summer style Brown Ales when it gets warmer... Those Ales have 50% special malt (mainly crystal) and i go on the 20 liter range. They run on 11% Plato and are mash at 70 Celsius. So we got a AA of 48% with the S04. This hughe amount of crystals come from the low alc range. I am aming here for a 2,8% Alc Ale full bodied. And there we got the problem. Eventhough i used Wyeast yeast Nutri for my brews, some just didn go thourg and S04 slept just to awake once in Keg and bottle.... So even after 25 day of primary and testing the S04 suddenly woke up in bottle and i got a little more carbonisation than i calculated... mostly i aimed for 3,5g/l Co2 and got 4-4,3g/l. So i began thinking that the amount of yeast supplied by one package of S04 is not enough for a 50% special malt brew fermented at 16-17 Celsius. Since the normal brews like classic 10% Speical Malz grain bill work fine, it must be the yeast on hat point which seems to be in trouble.

I did "overpitching" by dumping fresh wort directly on the yeastcake from previous batches, sometimes I even did this continuously multiple times with the same yeast, no harm taken.

The only thing truely problematic i could see is that also the amount of dead cells increases, so after months and months you might end up with some of them falling apart leading to autolysis induced flavours. Another thing is that you might, or actually might not decrease ester production, so if you are after yeast expression, this might be or might be not a bad thing to do.

Otherwise, I'd say dump it all in, the more healthy yeast, the better.

Thank you m8 for the answer. I guess i forgot to explain why i asked that question at all. I normaly make summer style Brown Ales when it gets warmer... Those Ales have 50% special malt (mainly crystal) and i go on the 20 liter range. They run on 11% Plato and are mash at 70 Celsius. So we got a AA of 48% with the S04. This hughe amount of crystals come from the low alc range. I am aming here for a 2,8% Alc Ale full bodied. And there we got the problem. Eventhough i used Wyeast yeast Nutri for my brews, some just didn go thourg and S04 slept just to awake once in Keg and bottle.... So even after 25 day of primary and testing the S04 suddenly woke up in bottle and i got a little more carbonisation than i calculated... mostly i aimed for 3,5g/l Co2 and got 4-4,3g/l. So i began thinking that the amount of yeast supplied by one package of S04 is not enough for a 50% special malt brew fermented at 16-17 Celsius. Since the normal brews like classic 10% Speical Malz grain bill work fine, it must be the yeast on hat point which seems to be in trouble.
Pitch rate has nothing to do with what happened. Your recipe and process, combined with flocculation characteristics of this yeast, are what caused this. Nothing to do with pitch rate. S-04 is a fast fermenter, flocculates quickly, and might have become excited upon being disturbed during packaging. You had a stuck fermentation, which a little rousing whether in the primary or during packaging would reawaken.

Pitch rate has nothing to do with what happened. Your recipe and process, combined with flocculation characteristics of this yeast, are what caused this. Nothing to do with pitch rate. S-04 is a fast fermenter, flocculates quickly, and might have become excited upon being disturbed during packaging. You had a stuck fermentation, which a little rousing whether in the primary or during packaging would reawaken.
I know what you mean but how comes that i only had this issue with those 50% low alcs and not with normal brews ? I mean there must be a reason.

Also to add that on the first go with double yeast it worked fine on the same grain bill which worked not fine before.

It's difficult to say with certainty exactly what caused a stuck fermentation, but I do think the 16 C fermentation temperature seems low for this yeast, in MY opinion.

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