Too Long On Yeast?

[komodo]

Guys,

Just wondering if there is a time limit for how long you can leave a brew on yeast for after fermentation activity has ceased. I tend to leave my brews in the fermenter for about 3 weeks but some times longer - once 6 weeks (I forgot about it...). I've not noticed (thats not to say it isnt - I just havent noticed) this to be detrimental to my beers so far. So is there a limit to how long you can leave your beer on the yeast and what are the likely effects? I always have my brews in a temperature controlled environment (tempmate) so im guessing this would be helpful to a degree.

Part of me thinks that there must be a limit but then part of me thinks that bottled beer that is naturally carbonated sits on yeast until it is consumed. But of course that is at lower quantities and is also under pressure from the CO2

any one got any input on this?

Cheers,
Komodo

 

[Adamt]

Yes, there is a limit, but it's variable and indefinite. It depends on temperature, yeast health, etc. Generally if you keep it around or under 20C (for ales) you can leave it for a couple of weeks without ill effects.

The big problem with leaving it on the yeast cake is yeast autolysis, you effectively start making vegemite in your beer.

 

[newguy]

In my experience, autolysis (bad flavours from the yeast dying) isn't an issue unless the temperature is too high (roughly mid 20's C+). I never transfer to secondary with my ales and I'll only sometimes do so with lagers. My really heavy OG beers sit on the yeast for 4-5 weeks, sometimes more, with no issues although I ensure that the temp never exceeds approx 20C.

In really low concentrations, I pick up autolysis as the flintstone vitamin aroma. I know people who have told me that it's a B vitamin type of aroma as well. In higher concentrations it can be soapy (dish soap), fatty (like lard), meaty, sometimes a bit salty, rubbery, etc. If you're curious what it smells and tastes like, set aside approx 200ml of yeast slurry with about 50-100ml of beer sitting on top in a sterile sealed container. If you're using glass, ensure that the beer has finished fermenting otherwise you may end up with a grenade. Follow your normal sanitation regime to ensure no bacteria end up adding their own (different) side effects. Place the container someplace warm, like on top of your fridge, and leave it for 4 -6 weeks. When you open it you'll know what autolysis is.

 

[komodo]

Interesting.

So if the yeast is sitting in the fermenter in a temperature controlled fridge crash chilling for a few weeks the chances of autolysis occuring is quite slim compared with if i left the temp controlled fridge at fermenting temps?

 

[newguy]

I don't think you even need to crash chill it unless your fermentation temperature is over 20C. I make one batch of mead every year and it stays on the yeast for approx 3 months with no ill effects. This is at my normal basement temperature of ~18C. It shouldn't be an issue unless you're fermenting a Belgian at 27C.

 

[MarkBastard]

I've only found bad things when I've left it too long, even when crash chilling.

I reckon as soon as your co2 barrier has gone away you're in trouble and it needs to be kegged or bottled ASAP.

 

[beerDingo]

BYO magazine did an experiment where people split up a brew and left each bach a bit longer on the yeast to see the difference. Not quite the same but similar.
Found here:
http://www.byo.com/component/resource/arti...-harm-your-beer

 

[komodo]

When you say too long mark how long are you talking (feel free to generalize here)? Are you talking 4 weeks? 3 weeks? 6 weeks? 2 months?
Also do you ferment with carboy? or with plastic fermenter with airlock? fermenter with gladwrap?
The reason I ask is I wonder where the CO2 is going? I thought that the fact that the fermenter is sealed all bar the airlock which should have a liquid barrier (i use cheap vodka) the CO2 barrier should be going any where provided the fermenter is left undisturbed?

Like I say mine normally sit for 3 weeks and the longest is 6 weeks so I'm glad that I now feel I can fairly safely leave it for this length of time with realitively little chance of autolysis occuring.

 

[MarkBastard]

I use glad wrap.

I find after say 2 weeks after fermentation has finished, that it seems like there is no co2 layer over the beer and sometimes in the past I have found fruit flies buzzing around the top of the fermenter trying to get in. This was when I did an unrefrigerated one in winter when my garage was perfectly 18 degrees day or not.

It was just a kit so I was a bit lazy when it came to racking. I ended up chucking the whole thing out, didn't even make an attempt to keg it.

 

[komodo]

I thought you might. I think the gladwrap breathes more than a "normal" fermenter lid. Much like plastic freezer bags "bleed" when meat is left in them. Something to do with the grade of plastic? I dont know I just remember listening to Dr Karl on JJJ one thursday morning talking about it. I would expect that a normal fermenter lid with airlock will retain the "pressure" and thus the CO2 'should' remain layered over the beer.

 

[katzke]

CO2 is heavier then O2 so unless your plastic fermentor leaks or you have lots of air movement with open fermentation it is not going anyplace. The flies were most likely attracted to the smell of the fermentation.

As to how long to leave the beer on the yeast. I leave mine for up to a month on a regular basis. You have 6 weeks and no problem.

I think this is one of those brewing things that someone read about it and ran away with a half-truth. Now it seems to be talked about more then it needs to. I personally feel that more bad beer is brewed at home because people are told to remove the beer from the yeast way too soon. I have seen recipes that say bottle in a week and drink in a week or 2.

As with any advice correct brewing practices must prevail. I guess that is what your question is about. What is the correct brewing practice for removing beer from the yeast cake? Leave it long enough to do its job, like 2 weeks before racking or 3 weeks, then bottle or keg when you have time. Keep it at a beer temperature and all will be well for 6 to 8 weeks at least. Some beers can be rushed and some will be much better given more time. That is the hard part about defining proper brewing practice. Each beer can be different as well as each brewery is different.

 

[Wisey]

I found the beer I left on the cake the longest turned out the clearest and smoothest I have produced so far

Others are murky and muddy with big hop flavour and no real malty flavour