In these times of austerity, and being a tight-arse as well as lazy, I am thinking about reusing the yeast from our current brew (the Windsor Knot IPA) in the next brew that I do.
During fermentation the yeast forms a thick sediment or slurry (called the “cake”) at the bottom of the fermenter which is left behind when you rack the beer off into a secondary or bottling bucket. With dry yeast sachets currently costing nearly £3 and vials or slap-packs probably double that, it seems a shame to let all this yeast go to waste. There are basically three ways you can reuse it:
1. Pour new wort directly onto the cake.
This is by far the easiest method with the appealing bonus of not needing to clean out and sterlise your fermenter! Just rack off your finished beer from a previous batch into your secondary/keg/bottling bucket and leave the lovely yeast cake sitting at the bottom. Make your next batch and once it is cooled, pour it straight on to the slurry. You will need to shake it to aerate the wort and you may want to do this after adding half the wort to make it easier to mix up the sediment.
Although it is by far the easiest method it is usually considered bad practice for a few reasons:
- there is a risk of bacteria getting in a spoiling the batch (if you are fairly clean in your methods I think this risk is minimal)
- the sediment contains all kinds of crap you don’t necessary want in your next brew – hop residue (which will alter your beer profile), dead yeast cells, trub, coagulated protein, etc.
Therefore it is only really recommended if you are doing a heavier beer that the first brew. And I wouldn’t reuse a cake more than once although some say it can be done two or three times.
2. Yeast washing
The proper way to reuse your yeast it to get it out of the ferment and and “wash” it to get rid of all the crap I mentioned above. It can then be kept in a jar and used as you wish into wort in a nice sanitised fermenter. I know Fendog has had some experience with yeast washing but I haven’t yet. I will post more on this topic when I do.
3. Pitch a cup of slurry
The compromise between the two methods above is to just keep part of the slurry. Scoop some out with a sterilised cup and re-pitch it into the new wort in clean, sanitised primary. This reduces the amount of crud in the second brew but it does mean you have to do some cleaning.
If you are not going to brew immediately, you can keep the salvaged slurry for up to a week in the fridge. Make sure it is in a clean sanitised jar and the lid is fitted loosely to allow any fermentation.
Having considered the options, I think I am going to go for option 1. I just can’t be arsed with anything more complicated. This weekend I am going to bottle the Windsor Knot IPA and lay down a new brew straight onto the cake.
To counter some of the drawbacks of this method, I am just going to go with a very basic Barleywine as the next brew. An extract barleywine is pretty simply business – a bit of crystal malt for steeping, enough malt extract (and possibly some sugar to get a really high gravity) and then hop it to high heaven!
I’m not going for subtle flavours or anything so any tainting from the reused slurry wont matter. And the key thing with big beers like Barleywine is lots of yeast. This should be just the ticket.