# Upside down yeast



## livo (8/2/22)

I've collected the yeast cake from a recent brew (US-05) in a sterile 2 litre glass flagon with the intention of washing. I've performed this process before, watched all the videos and read up a lot. I've never seen this before. I'm on the tablet entering this so I'll add photos later.

Usually when you add sterilised water to the yeast cake and collect it you will fairly quickly see the layers forming with the dark trub settling to the bottom, the lighter creamy yeast above and clearer liquid (water and residual beer) on top. If you refrigerate this it will become very clear layers with distinct lines. This did not happen for my most recent collection.

Instead, as the solids began to drop out of solution, I had the dark layer sandwiched between lighter creamy layers above and below. Now, yesterday after refrigeration, I have the distinct layers of separation but they are upside down. The bottom layer is light and creamy, the middle layer is darker and mottled with the clear liquid on top.

Anyone seen this before? Is the bottom layer the trub or the yeast?


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## livo (9/2/22)

Update: I ignored my confusion about the lightness / darkness of the layers and assumed the trub to be on the bottom, as you'd expect, despite the colour. I have allowed this to warm and poured off the clear liquid, followed by collecting the next layer, assuming it to be yeast. After the first washing in boil sterilised water the separation has occurred as expected with the darker stuff falling to the bottom. I've repeated the process and collected 4 small jars of very clean yeast which has been refrigerated overnight. I expect to have 4 nice jars of reusable US-05 this morning.

Maybe this isn't something new but I've never seen the bottom layer being creamy white and the usable yeast dark before.


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## livo (10/2/22)

Any ideas on how you would estimate the cell count in these collected jars? I estimate there to be approximately 20cc (ml) of yeast settled to the bottom of each jar. As this is the collected amount from a single fermentation and some has been discarded in the process, how much would you pitch into another brew?


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## MHB (10/2/22)

You can’t keep expecting simple answers to complex problems.

Typically yeast slurry is thought to be around 50% yeast balance being trub.
A fair rule of thumb would be 1.2Billion cells/mL, that is in a healthy fresh slurry, how long you keep it before use and what that will do to the population, its vitality and the number of mutations that can be expected is way more complex.

In a brewery the typical pitches are way bigger than most home brewers would consider, 0.5million cells/mL/oP would be a minimum.
Say you were pitching into 23L of 1.050 (12.5oP) wort at 0.5million cells/mL/oP you would need 23000*0.5EXP6*12.5=143,750,000,000 cells at 1.2Billion/ml (1.2EXP9) you need 119.79mL Ok call it 1.20mL.
Fair to say if you pitched all you have it would be an underpitch.

Making a decent starter, pitching one of your jars and making sure it’s well aerated and you might get the starter up to 80-100Million cells/mL Leave it to you to work out how big your starter should be. If I tell you I suspect you won’t believe the answer.

On the Catalyst episode linked earlier, did you notice dry yeast being sprinkled directly into the fermenter? Un-hydrated, not a starter in sight, I suspect you would be surprised at how many small breweries do exactly that.
Yeast is the wrong place to try and save money on a brew.
Mark


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## livo (10/2/22)

Thanks again Mark. 

I'm not expecting anything really. I just ask questions that occur to me as something I don't know. Any information freely given is well appreciated and you have once again provided as good an answer as one could hope for. I've pitched a new brew on a full yeast load from the previous fermentation before without removing any trub. I've washed yeast before and just used the whole lot. I was just wondering if it required all and apparently it does because I have maybe 80 ml and I'd need 120.

I was just interested in the maths and 1.2X10^9 /ml is a good starting point to at least see what I might have collected and then compare it to what might be in a packet. Whether or not I start playing with starters is undecided at this point although I have just treated myself to a 6 pack of Coopers Original Pale Ale (with birthday discount) and I'm about to do the harvesting as shown on their video. Again, just for the heck of it, but I intend to use it.

I'm not trying to save money. I'm a retired old (nearly) bloke and I like fluffing about with stuff. Playing with yeast is just something to do in the shed. If it succeeds then good. If I start getting dodgy beer, it won't last long.


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## Jolls (11/2/22)

MHB said:


> On the Catalyst episode linked earlier, did you notice dry yeast being sprinkled directly into the fermenter? Un-hydrated, not a starter in sight, I suspect you would be surprised at how many small breweries do exactly that.



Thanks Mark

That was one thing that stood out for me. I expected that they would be using a harvested liquid. The idea of growing a starter sounds great but there is a bit of work that goes into it. Maybe when I come across that incredible drop with some specialist yeast, or I retire in a couple of years and have the time, like Livo, to experiment. In the meantime I'm pretty happy with yeast from the LHBS.

Livo 

Let us know how it goes. 

Cheers n Beers
Jolls


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## livo (11/2/22)

I'm in the middle of reading an article on yeast propagation and maintenance by MB Raines on The Maltose Falcons website. Fascinating stuff. The interesting thing is under-pitching is very common in home-brew. An airlock method starter would need to be 50% of the final wort volume. I think this is what you were saying mhb. Those little packets of dried yeast are demonstrably inadequate and apparently put a lot of stress on the yeast, by forcing reproduction instead of fermentation. It appears we are lucky if we get a good beer with k&k approach.


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