Yeast, how much is too much?

[SporkD2]

Me and a friend were debating on the effects of overpitching in ales. Is there danger, is there not?

My position is people pitch onto yeast cakes all the time, with no bad side effects (I do this also). Those same people however will criticize someone for making a 3L starter for a 5g ale.

He says to much yeast and you can get autolysis. AKA to much of a good thing is bad.

I want your thoughts and your vote, so I can show him.

 

[MikeFlynn74]

Im under the impression that your wasting time and maybe money by super pitching.

Its definitely better than under pitching. Not to be out done by side arm pitching.

 

[Brewsmith]

It all depends on the starting gravity of the wort. Pitching on a yeast cake is fine if the OG is hugh enough. Using an entire 5 gallon yeast cake on a 1.040 beer would be too much. You need some yeast growth to provide some of the flavors in your beer. If you overpitch, the yeast just goes right to work without multiplying. That being said, the majority of homebrewers underpitch, which has it's own set of problems.

 

[oberon567]

http://www.mrmalty.com/calc/calc.html

The chance for autolysis is pretty slim, that involves LOTS of yeast and/or LOTS of time.

But that is not the only off flavor. Chris White from White Labs Yeast and Jamil Z. both say that an important part of the final flavor of the beer has to do with the actual yeast growth. If you over pitch there will already be enough active yeast, and it will ferment fully but there is no yeast growth, and it will affect the flavor. The are myriad other ways that both under and over pitching can affect the final flavor. But all that said, if you're not brewing for style/competition, a lot of these unintentional flavors may not be entirely awful, just different than expected. And really, it is better than underpitching and having some bottles explode on you down the line.

 

[david_42]

both say that an important part of the final flavor of the beer has to do with the actual yeast growth.

This is true for some styles, but for 90% of what we make, over-pitching is not a problem.

 

[Yuri_Rage]

It depends. Sometimes a slight (or even gross) overpitch won't harm a thing, and it might actually help, especially when the wort is poorly aerated and the style requires a clean ferment. However, overpitching a hefeweizen or Belgian ale may cause less ester production, resulting in a less desirable flavor profile.

 

[MNBugeater]

From what I have read and heard, it is pretty hard to overpitch. Unless you are stepping up a starter well beyond the 3000mL mark for 5G, I wouldnt worry about it.

 

[Fingers]

I find the yeast growth comment interesting. What compound is available from growth that isn't there if you pitch too much? Seems to me that compound would still be in your yeast cake from the last time it reproduced. If not, then it wouldn't be in your final brew either.

 

[oberon567]

I dont know... I just know what they say... I have not done enough batches or experiments of my own to be able to taste the difference. But yeast creates a lot more than just alcohol, and some of the compounds it reuses/reabsorbs, others it does not. And some of those are created during growth, some are created as it feasts on sugar, some stuff happens after the alcohol has been pooped out but before the yeast dies... I dont know all the details, but it is a complex little organism, so it is safe to assume that using it in a different manner creates a different result...

 

[Jaeger48]

I dont know... I just know what they say... I have not done enough batches or experiments of my own to be able to taste the difference. But yeast creates a lot more than just alcohol, and some of the compounds it reuses/reabsorbs, others it does not. And some of those are created during growth, some are created as it feasts on sugar, some stuff happens after the alcohol has been pooped out but before the yeast dies... I dont know all the details, but it is a complex little organism, so it is safe to assume that using it in a different manner creates a different result...

I have heard the same. It isn't just a matter of what is there but what the yeast produce when they grow and bud healthy daughter cells. When the cells are dividing are building cell walls the sterols and esters they produce differ on the environment they are growing. I'm under the impression that the "yeast pee" is what changes.

 

[ohiobrewtus]

http://www.mrmalty.com/calc/calc.html

The chance for autolysis is pretty slim, that involves LOTS of yeast and/or LOTS of time.

But that is not the only off flavor. Chris White from White Labs Yeast and Jamil Z. both say that an important part of the final flavor of the beer has to do with the actual yeast growth. If you over pitch there will already be enough active yeast, and it will ferment fully but there is no yeast growth, and it will affect the flavor. The are myriad other ways that both under and over pitching can affect the final flavor. But all that said, if you're not brewing for style/competition, a lot of these unintentional flavors may not be entirely awful, just different than expected. And really, it is better than underpitching and having some bottles explode on you down the line.

I use this calculator quite often. If I'm pitching from a previous yeast cake I will always measure out the calculated amount rather than just pitch on the entire cake from a previous batch.