Whole yeast cake or half?

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matt76

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I've done a couple of brews recently where I've dumped fresh wort onto the yeast cake from a batch I've just bottled.

(This was two different yeast cakes, not reusing the same one several times)

So far no issues that I'm aware of...

But I'm sure I read, or heard something on a podcast, recently suggesting that it's ok to reuse a yeast cake but you should only use half the yeast cake.

The reasoning is you've got old and dead yeast cells in there - by using less yeast cake I guess you've still got plenty of viable cells in there but by starting with fewer cells you're encouraging them to grow and multiply.

(On that basis I'd have thought even a third or even a quarter yeast cake could be plenty to start with, depending a bit on ale Vs. lager yeast, your OG etc.)

Anyone got any thoughts on this?
 

samale

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I've done a couple of brews recently where I've dumped fresh wort onto the yeast cake from a batch I've just bottled.

(This was two different yeast cakes, not reusing the same one several times)

So far no issues that I'm aware of...

But I'm sure I read, or heard something on a podcast, recently suggesting that it's ok to reuse a yeast cake but you should only use half the yeast cake.

The reasoning is you've got old and dead yeast cells in there - by using less yeast cake I guess you've still got plenty of viable cells in there but by starting with fewer cells you're encouraging them to grow and multiply.

(On that basis I'd have thought even a third or even a quarter yeast cake could be plenty to start with, depending a bit on ale Vs. lager yeast, your OG etc.)

Anyone got any thoughts on this?
I regularly reuse the full yeast cake. It's a massive over pitch but I have never had a problem. I think the most I have did this is 3 times. It saves me the hassle of cleaning the fermentor.
 

Rodcx500z

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I regularly reuse the full yeast cake. It's a massive over pitch but I have never had a problem. I think the most I have did this is 3 times. It saves me the hassle of cleaning the fermenter
Hi Samale would this work with a kit, could I mix the kit as normal then put on the cake
 

samale

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Yes no problem as long as it's a similar brew. I brew alot of American style IPA/pale ales. The only risk if the first brew is anyway infected the second brew will be on the yeast cake before you pick it up after tasting the first.
 

Rodcx500z

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Cheers Samale will give that a go, my mother in law keeps buying me kits from wilko when she goes in athumb.. i do ag normally acheers.
 

Clint

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Ah.. mother in laws....you never know to despise them or just not like them very much..
 

Drunkula

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Anyone got any thoughts on this?
Thank god you didn't just put "Thoughts" I always ignore those threads even if I know what they're after. Like that I am.

Well on the Brewstrong podcasts a few times they've said that yeast create certain flavours in the reproduction phase and if you put in so much yeast that they don't need to reproduce then you won't get that element. I think you've really got to know your yeast characteristics for that, which is above my pay grade.
 

PhilBrew

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Hi Matt

+1 to what Drunkula says ... and while the quantities of yeast you'll be dropping your wort onto will probably constitute a "very high pitch", rather than "over-pitching", technically ... you probably are increasing the risks of all the problems that arise from yeast not reproducing (as much), resulting in an aging population in your yeast colony, which may lead to stalled ferments/greater risk of infections/etc. :?:

I don't know about other yeast calculators ... but the Mr. Malty calculator (link) includes an option for "Repitching from Slurry" (which is what you're yeast cake is) ... if you leave the Yeast Concentration and Non-Yeast Percentage options at the defaults ... and specify what volume of wort and at what gravity you're pitching into ... and it'll give you the volume of slurry you should use ... you'll probably find it would be around a 10th-15th of the whole cake :?:

Cheers, PhilB
 

Clint

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I've put a brew straight on top of another yeast cake and scooped out a cup full of slurry...both worked.
 

samale

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I've put a brew straight on top of another yeast cake and scooped out a cup full of slurry...both worked.
I have done both with no difference between them. I brew a lot of pale ales or IPA so it's a clean fermentation. Normally S05 or CML. Not sure on the effects when your looking for the yeast to contribute certain qualities. I know the kviek yeast likes to be stressed from under pitching
 

matt76

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I have done both with no difference between them. I brew a lot of pale ales or IPA so it's a clean fermentation. Normally S05 or CML. Not sure on the effects when your looking for the yeast to contribute certain qualities. I know the kviek yeast likes to be stressed from under pitching
Well I'm not at a point where I want to manipulate yeast qualities, certainly not in this way.

I think it's just a case of considering the options to try and stack the deck as favourably for me as possible to ensure a good/healthy fermentation.

Thanks all for your inputs athumb..
 

TommyK

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Hi. I've never used the remaining test cake for a next batch so I'm nervous. How long can you save it and is there any method to check if it's still alive? Do you just through all into the new batch?
 

Cwrw666

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I use it the next day after bottling and just put about 3 tablespoonfuls into a sterilised mug, sealing it with clingfilm to keep bugs out. Next day I do another brew and pitch this into it when it's the right temperature. Fermentation gets going a bit slower than pitching fresh dried yeast though.

I've also saved the dregs from 3 bottles of beer and pitched that into a brew and that has worked too. Useful to know if you've started brewing before you realise you have no yeast in stock!
 

Pennine

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The only problem I have had with it is less room in the fermenter so blow offs happen. I like limited head space so it's tight on a second and third batch. I'd make sure to dump all the liquid off before racking the wort. Also cool the wort off before transferring or your temps will never come down.

It's great when your fermenting kicks off within a few minutes of transferring.
 

Jakeyboi

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I’ve put a new batch straight onto the yeast cake a few times with no problems. I’ve also scooped up about 500ml in a sterilised Kilmer jar and put it in the fridge for a week. With no perceivable problems either way, I don’t have the most delicate of palates though. I recommend just experimenting for yourself.
 

samale

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The only problem I have had with it is less room in the fermenter so blow offs happen. I like limited head space so it's tight on a second and third batch. I'd make sure to dump all the liquid off before racking the wort. Also cool the wort off before transferring or your temps will never come down.

It's great when your fermenting kicks off within a few minutes of transferring.
Why limited head space. What's your thinking about that. I am the opposite I ferment 23 litres in a 30 litre barrel. No real reason but that's what I do.
 

Pennine

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Why limited head space. What's your thinking about that. I am the opposite I ferment 23 litres in a 30 litre barrel. No real reason but that's what I do.
Actually it's one of the few things I have changed in my brewing process. Usually with headspace of more than a couple liters I get an apple flavor. I am assuming it's acetaldehyde. It's a similar flavor to drinking a cask ale that isn't as fresh as it should be. I'm assuming it's an overabundance if oxygen issue. I can clearly detect the difference in brewing 10l in a 14l fermenter vs. a 20l. I think they have tested it a couple time on brulosophy might be worth a look.
 

samale

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Actually it's one of the few things I have changed in my brewing process. Usually with headspace of more than a couple liters I get an apple flavor. I am assuming it's acetaldehyde. It's a similar flavor to drinking a cask ale that isn't as fresh as it should be. I'm assuming it's an overabundance if oxygen issue. I can clearly detect the difference in brewing 10l in a 14l fermenter vs. a 20l. I think they have tested it a couple time on brulosophy might be worth a look.
Must check it out.
 

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