Reusing yeast by adding fresh wort on top of the yeast cake

[obscure]

I currently have a batch of Yorkshire Bitter that is almost done fermenting and was planning to keg it on Saturday. The yeast was Wyeast West Yorkshire Yeast and I am planning on doing a batch mild on Saturday. Could I simply pour the wort from the mild on top of the sediment left over from the Yorkshire Bitter or is this probably a bad idea.

 

[St00]

I've done something similar by using the slurry from a saison I've had in the fridge for a month on a saison I brewed on Sunday. If you give me a couple of weeks I'll let you know how it turns out!

In all seriousness though, if you empty the fermenter and then pitch the cooled wort straight on top of the yeast cake I've read of people doing this without issues on this and the David Heath Facebook Group, although I've never done it this way.

 

[terrym]

I often recover yeasty trub from one brew and store it in the fridge for reuse. However I usually don't keep it for longer than two weeks or so, will only use the top layers of settled yeast, only go up to three generations and importantly I scrupulously sanitise anything that comes into contact with the yeast.
Otherwise there is a longish thread about this subject here
https://www.thehomebrewforum.co.uk/threads/trub-yeast-re-use.85651

 

[obscure]

I've done something similar by using the slurry from a saison I've had in the fridge for a month on a saison I brewed on Sunday. If you give me a couple of weeks I'll let you know how it turns out!

In all seriousness though, if you empty the fermenter and then pitch the cooled wort straight on top of the yeast cake I've read of people doing this without issues on this and the David Heath Facebook Group, although I've never done it this way.

Thanks I was thinking it should work but was worried was missing something obvious and it seems such a waste not to try.

You need to get your spell checker adjusted. Its wort you are talking about not wart which are something else!
Anyway I often recover yeasty trub from one brew and store it in the fridge for reuse. However I usually don't keep it for longer than two weeks or so, will only use the top layers of settled yeast, only go up to three generations and importantly I scrupulously sanitise anything that comes into contact with the yeast.
Otherwise there is a longish thread about this subject here
https://www.thehomebrewforum.co.uk/threads/trub-yeast-re-use.85651

Well that is embarrassing corrected the spelling as of course I mean Wort not wart.

Also thank you for the link my original plan was to literally keg the bitter then add the cooled wort straight on top immediately afterwards so no issues with storage. However what I am thinking now is put the wort into a fresh fermentor and take a couple of cups of fresh slurry and pitch that.

Ideally if it works I would try to do similar beers in a row i.e. a batch of sixty shillings ale, then a batch of wee heavy using Wyeast Scottish Ale, as while I like hassle free brewing if their is an easy way to reuse yeast and bring down the cost a little I am all for it.

 

[Horners]

I did this for a batch of Black Sheep. Fresh wort straight into used FV with Wyeast whitbread cake from previous brew. Came out fine. Did try and clean the dried on krausen off from previous brew but other than that no messing about.

 

[The Baron]

I do as Terry says I put the yeast/trub in a sterilised jar or 2 and let it settle and before pitching pour off the beer on top I also agree about using the yeast more than 3 times as I have found that it can take a lot longer to ferment out on subsequent brews.
Ps make sure if you store the yeast in the fridge/cold place that you let it get to the same temp as the wort for pitching or it may shock it and kill a lot of the cells off

 

[Clint]

I've only tried with dry yeast/kits and have both put wort straight on top and took a jar of slurry and tipped it into the next brew. Both were fine although it's not something I've done since.

 

[matt76]

I did this for a batch of Black Sheep. Fresh wort straight into used FV with Wyeast whitbread cake from previous brew. Came out fine. Did try and clean the dried on krausen off from previous brew but other than that no messing about.

Likewise, I've done it a few times too, no problems at all. I didn't even bother trying to scrape off the dried on krausen.

I suppose my only issue is it feels like more shag & hassle of you have to combine bottling and brewing into one day.

 

[Horners]

Likewise, I've done it a few times too, no problems at all. I didn't even bother trying to scrape off the dried on krausen.

I suppose my only issue is it feels like more shag & hassle of you have to combine bottling and brewing into one day.

I think I probably got the idea from your thread.

 

[Surfingobo]

I often do this, mostly due to laziness. Means I only have to clean FV every other batch!

 

[PhilBrew]

Hi @obscure

Under-pitching is the more commonly experienced and thus the more often written about/discussed topic, when it comes to yeast pitching rates ... but over-pitching of yeast is a thing ... and pitching a volume of wort onto a yeast cake from a ferment of a similar volume of wort with a similar (or worse higher) OG, is a great way of risking suffering from the problems (like under-pitching, over-pitching can lead to stalled ferments, off flavours from petit-mutants, etc.)

If you use a pitching rate calculator like the one on the MrMalty website and choose the "pitching yeast slurry" option, then you'll see that dropping your wort onto the whole yeast cake from a previous brew will be (effectively) pitching 5-10 times more yeast slurry than even the most generous of pitching rates you could choose ... like not bothering to rehydrate dried yeast, or not bothering to make a starter from a pack of liquid yeast, just because other people have "got away with" doing it in the past, you have to ask yourself "Am I willing to risk my brew to it?"

Cheers, PhilB

 

[obscure]

@PhilBrew
Thanks for the input I am increasingly tempted to pitch some of the slurry rather than pitching on to the yeast cake directly. I have keyed it into brewers friend and it looks like a single mug of slurry would be more than enough to do for my standard 10L batch. Or even for the 13L barley wine kit I am half thinking of doing this weekend.

Honestly I will probably decide on the day how to proceed as it looks like a fair few people have done it and gotten away with it, but will probably try to skim a layer of slurry off the top.

 

[Cestrian]

If your using wyeast 1469 then you should try top cropping the yeast by skimming it off the top a few days into fermentation, then store it in a kilner jar in the fridge. This will give you a much cleaner yeast for your next batch and you can go on like that for multiple batches. That's because there's no trub or dead yeast like at the end of fermentation taking the yeast that's left after racking off. There's no real harm in doing it either way though. Just make sure everything is very clean and as others have said if you're collecting yeast from the bottom of the fermenter, try washing it to remove any trub, dead yeast and hop debris and check mrmalty to get the pitch volume right. On brew day I pour the water/beer off the top of the kilner jar so it just leaves the thick slurry, then put it on the kitchen scales. Weigh it, pour some out into the cooled wort, weigh it again, pour some out again, until I've added the amount it tells me on mrmalty.

I've been doing this for a while now with Kolsch yeast K96, which like wyeast 1469 creates a big krausen, so lends itself well to top cropping. Let's face it brewers and breweries have been reusing yeast from the last batch for hundreds of years. It's only relatively recently that we've been able to get dried yeast in little packets or liquid yeast from white labs etc.

 

[obscure]

Thanks for all the responses in the end I opted to take about a cup of the slurry (used the yeast calculator on brewers-friend for slurry and this should fingers crossed be more than enough) and pitched it this morning so should hopefully see some activity soon.

@Cestrian Unfortunately by the time I thought about reusing the yeast the fermentation was almost done, however I am considering doing this in future. Although admittedly if harvesting the slurry at the end works out well I will probably do that given how easy it was.

 

[matt76]

As I mentioned before, personally I don't have an issue with my frankly bone idle chuck the wort onto the entire yeast cake...

But @PhilBrew is absolutely right to point out there is a risk of over-pitching, and I suspect your slightly more diligent approach will strike the right balance

FWIW (and I've mentioned this before) there was a listener question on this subject a while back on the Experimental Brewing Podcast. Denny certainly didn't advise against using the entire yeast cake but recommended using only a third of it simply because he thought the beer turned out best when he'd done it this way.

So based on that I suspect your "about a cup of slurry" is probably somewhere in line with using a third of the yeast cake

 

[obscure]

Just to say thank you for all the advise as mentioned I ended up using about a cup of slurry in a Youngs Barley Wine Kit (made with the kit and 2.5KG of Marris Otter). The fermentation took,off extremely quickly and the sample I tasted from the fermentor was pretty good, no off flavours.

Plan to start reusing yeast this way on a regular basis as really cuts the cost of using liquid yeasts.