Yeast cake

[Robbo100]

I read in the FAQs that you can put a new wort onto a previous yeast cake. I was wondering if you chaps might be able to answer a couple of simple questions.

1) am I right In thinking that the yeast cake is the crud left in the bottom of the FV?

2) should any scum be removed from the top of the previous beer (floating stuff) before adding the new wort, or is this classed as part of the "cake"?

3) is there a limit to the number of times you should do this in succession, to minimise infection (or for any other reason).

4) does the following wort have to be the same beer as the first beer for flavour reasons, or could I add a pale ale on top of a porter cake (for example), without any flavour contamination?

5) is there anything I should consider if I plan to use this technique?

Thanks all.

Robbo100

 

[WelshPaul]

1) Yep

2) Each time I've done it there hasn't been any krauzen left on the top after 2 weeks in the fermenter but I don't see what harm it would do if there was.

3) There shouldn't be much risk of infection but I've heard that yeasts can change their properties after several generations.

4) No, you can use whatever you like! :)

5) Don't cross the beams...

 

[graysalchemy]

General bit of asvice don't use a dark beer yeast cake on a light beer. Don't use a really hoppy yeast cake on a lightly hopped beer and finally discard a yeast cake from a really strong beer the yeast will be knackered and may well mutate.

Also you are best collecting the yeast cake from a primary fermentor before it has finished clearing. Th eyeast which is still in suspension is likely to be less floculating so a little bit of selection will help your yeast population.

I usually recover the yeast wash it in cooled boiled water, there are plenty of good threads on it. I would also use a yeast cake with in a couple of weeks they do deteriate to the point of getting infected.

I also no freeze yeast samples but you will need to use sample samples and dilute with a mix of water and glycerine in the following proportions:

Yeast 50% water 25% and Glycerine 25%. Freeze them in preferably an old style freezer which doesn't have a frost free setting or a thaw cycle. If you do havea modern one then make a styrene box to hold them in.

:thumb:

 

[robsan77]

Another rule is only go up in abv. So don't put a 1040 wort on top of a yeast that has fermented a 1050 beer.

It's best also to collect just 100 grams of the thick slurry and use a clean fv.

 

[graysalchemy]

It's best also to collect just 100 grams of the thick slurry and use a clean fv.

Good point

You don't actually need a full yeast cake. If you do you may end up with this

 

[Robbo100]

That photo is more like a whole bakery thank just the one cake.

Thanks for the tips chaps. Re-using yeast seems to be an advance brewing technique, but it sound like I would be crazy not to do it (especially if I am using expensive yeast).

It also sounds like the technique of starting a new brew on the day that I bottle my last one (with a scoop of the slurry from the bottom of the previous FV) is the simplest way forward.

Thanks all.

 

[WelshPaul]

Re-using yeast seems to be an advance brewing technique, but it sound like I would be crazy not to do it (especially if I am using expensive yeast).

I tend to re-use yeast, either by pitching the new batch of wort onto the newly syphoned yeast bed or by storing the slurry in the fridge for a week or two. Not for any reason other than money is tight and I do not want to pay another 3-6 quid for my next yeast! :grin:
It's not too difficult, especially when it comes to leaving the yest bed in the FV and pitching fresh wort on top; I've done it 3-4 times already and have never lost a batch.

 

[bunkerbrewer]

I usually recover the yeast wash it in cooled boiled water, there are plenty of good threads on it. I would also use a yeast cake with in a couple of weeks they do deteriate to the point of getting infected.

Interesting - do you literally mean the yeast cake, or the yeast that you recover? I was planning on washing and decanting some WLP001 from the yeast cake of my next brew.

If it's not wise to keep this for more than a couple of weeks I might rethink the plan and try to split the vial first.

Any advice appreciated!

 

[graysalchemy]

I have done both, washed it and recovered the yeast or used the whole yeast cake. My above photo was the aftermath of a 3 week old 2L yeats cake in 55L of a 1080 ish wort. :whistle: :whistle:

 

[bunkerbrewer]

:)

Looks like a couple of those old yeast cells survived then?! :)