Reusing yeast

[Martybhoy]

My next 4 brews all require WLP001. I think now is the time to reuse the yeast from one brew, for the next one.

I'm fairly comfortable with washing the yeast etc. My question is -

When calculating how much yeast you require for fermentation, how do you know how many cells you have to begin with? With a vial of new liquid yeast, it is 100bn, less cells lost over time (easily calculated). But what about when you harvest your own?

 

[DoctorMick]

It's very difficult to accurately predict, there is a slurry calculator on mrmalty which should help give a best guess tho.

 

[TheQuokka]

It's always difficult to predict. You are almost certain to harvest more than you really need, but hopefully less than too much.

I use vegemite jars, or a drinking glass if I am going to use it the same day. Sterilise the glass or jar in your pressure cooker or by boiling gently for 20 minutes. I also sterilise a stainless salad spoon and use it to collect from the top 1/2-2/3, as the bottom tends to be trub.

If you are re-using the same day, just cover with cling wrap until ready. Hopefully you will have enough beer on top to swirl and pitch. Otherwise you have probably collected about 100ml yeast and can add about the same cooled boiled water to swirl around.

Some say pro brewers use up to 20% but I personally don't recommend it for home brewers. I find that 100ml or so of good yeast will get a good fermentation happening real quick with minimal oxygenation.

If you have a few to do, divide all the yeast up into about 4-5 sterilised jars, again with a bit of beer to settle on top, and store in the very coldest part of your fridge (lowest part towards the rear,) for up to 6 months.

Sorry it took so long to post - new kitten has decided he likes Vodka martinis (I always knew James Bond was a pussy - I prefer a real martini when I have real gin.)

 

[MyQul]

As others have said, it's quite hard to predict but about 100ml of fairly clean trub will do the job. Or up to about 300ml if you have a lot of break material/dead cells/ etc mixed in there

 

[Martybhoy]

Ok, so 100ml. Would I still create a starter with it, a couple of days before brew day? And would I treat the 100ml or so like a fresh vial of new liquid yeast? By that I mean assume 100bn cells on day 1, and reduce accordingly with time?

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[Linalmeemow]

If you're pitching it within a week or two of harvest you can stick it straight into your wort as long as you've got enough, and you'll almost certainly have more than enough. I've just reused a WLP530 - rather than making a starter I made a low gravity patersbier to build up the amount of yeast then harvested and repitched into a strong golden ale. It went berserk, filled up 7 litres of headspace and still managed to spill out. Definitely a healthy ferment!

 

[Fore]

If you're pitching it within a week or two of harvest you can stick it straight into your wort as long as you've got enough, and you'll almost certainly have more than enough. I've just reused a WLP530 - rather than making a starter I made a low gravity patersbier to build up the amount of yeast then harvested and repitched into a strong golden ale. It went berserk, filled up 7 litres of headspace and still managed to spill out. Definitely a healthy ferment!

Although, I think best practice would be to use a starter, just to reinvigorate. When harvesting, it's dealt with the brew, and sat under fairly strong alcohol for some days. Of course I've never tested both approaches against each other, just repeating what I understand from what I read.

 

[MyQul]

Ok, so 100ml. Would I still create a starter with it, a couple of days before brew day? And would I treat the 100ml or so like a fresh vial of new liquid yeast? By that I mean assume 100bn cells on day 1, and reduce accordingly with time?

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You can do it you like. If your using it within a week or two weeks of harvesting you dont really need to but it wont do any harm if you do.

Viability will reduce over time but it's hard to know exactly how many cell you have unless you can count them with the correct equipment (microscope etc). So I generally stick to the two week rule (make a starter after two weeks of harvesting, just chuck it in if less) and chuck a bit more in just to make sure - about 120ml. As doing this wont do any harm either

Just to be clear 100ml is of fairly clean yeast (washed or equivelent) , compacted down in your collection receptical. If it's 'dirtier' (ie more trub) add more volume. I always err on the side of caution and chuck more in if I'm in doubt as it's quite hard to overpitch at the home brew level.

 

[Linalmeemow]

Although, I think best practice would be to use a starter, just to reinvigorate. When harvesting, it's dealt with the brew, and sat under fairly strong alcohol for some days. Of course I've never tested both approaches against each other, just repeating what I understand from what I read.

I'm pretty new to harvesting yeast and read up extensively beforehand as I do whenever I try a new technique. The majority of advice seemed to be that as long as you repitch in 1-2 weeks the starter isn't necessary. Some seemed to insist that a starter was best practice, others insisted that rinsing the yeast isn't even necessary and repitching the slurry mixed in with a little of the beer from the end of the previous batch is fine. There doesn't seem to be a definitive answer as is the case with all things homebrew!

 

[MyQul]

I'm pretty new to harvesting yeast and read up extensively beforehand as I do whenever I try a new technique. The majority of advice seemed to be that as long as you repitch in 1-2 weeks the starter isn't necessary. Some seemed to insist that a starter was best practice, others insisted that rinsing the yeast isn't even necessary and repitching the slurry mixed in with a little of the beer from the end of the previous batch is fine. There doesn't seem to be a definitive answer as is the case with all things homebrew!

* As long as it's less than 2 weeks old it's fine without a starter. I do this all the time

* Rinsing isnt necessary, in fact it is probably detrimental as a) your seperating the yeast from the trub which the yeast use as nutrient b) Water isnt sterile even if you boil it, just sanitised so you can potentially introduce infection. Beer is much more resilient to bacteria so it's best to keep the yeast under it. I never rinse yeast just pour some slurry into a jar and keep it in the fridge until I need it

 

[Linalmeemow]

* As long as it's less than 2 weeks old it's fine without a starter. I do this all the time

* Rinsing isnt necessary, in fact it is probably detrimental as a) your seperating the yeast from the trub which the yeast use as nutrient b) Water isnt sterile even if you boil it, just sanitised so you can potentially introduce infection. Beer is much more resilient to bacteria so it's best to keep the yeast under it. I never rinse yeast just pour some slurry into a jar and keep it in the fridge until I need it

The thing I read about just dumping the slurry without rinsing was written by Denny Conn, who seems to know his stuff. I'm using the WLP530 again to make a Belgian IPA in a couple of weeks. I'll try this method...

 

[MyQul]

The thing I read about just dumping the slurry without rinsing was written by Denny Conn, who seems to know his stuff. I'm using the WLP530 again to make a Belgian IPA in a couple of weeks. I'll try this method...

I tend to repitch two or three times doing this, then use some fresh yeast (either another dry pack or overbuild the starter again I'm currently using) and have never had a problem. It's really simple and easy to do and perfect for a lazy brewer like me

 

[Linalmeemow]

I tend to repitch two or three times doing this, then use some fresh yeast (either another dry pack or overbuild the starter again I'm currently using) and have never had a problem. It's really simple and easy to do and perfect for a lazy brewer like me

The IPA will be the last time batch I do from this yeast but mainly because I'll get bored if I overstock similar Belgian styles. I reckon I might do a few saisons next.

 

[Martybhoy]

I tend to repitch two or three times doing this, then use some fresh yeast (either another dry pack or overbuild the starter again I'm currently using) and have never had a problem. It's really simple and easy to do and perfect for a lazy brewer like me

So when you re-pitch 100-120ml, its slurry as opposed to yeast from rinsed slurry? Hop debris and all?

If so, and it works, then this is surely quicker, less hassle, and less risk from infection.

What kind of volume of slurry would you expect from 15ltrs of fermented wort?

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[MyQul]

So when you re-pitch 100-120ml, its slurry as opposed to yeast from rinsed slurry? Hop debris and all?

If so, and it works, then this is surely quicker, less hassle, and less risk from infection.

What kind of volume of slurry would you expect from 15ltrs of fermented wort?

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The slurry 'with everything in' I would pitch more like 200ml-300ml. I talking the stuff at the bottom of the FV from when you do a BIAB and you throw everything into the FV so it contains a large amount of break material in there too. 100ml-120ml is the amount I would use for either rinsed yeast (not that I rinse yeast) or when you use some sort of method such as whirlpooling to leave most of the trub in the kettle

Depending on whether you use a method that prevents all the trub going into the FV or not, you'll easily have enough yeast to harvest. My last brew was a 5L stove topper where I just chucked everything into the FV. I collected all the trub in a jar and this came to about 500ml had I used a method to prevent the trub going in the FV I would have collected about 100ml- 200ml of quite clean yeast

 

[Martybhoy]

Cheers MyQul.

One last question (hopefully) :

if you harvest say 300ml of slurry, but don't use it for a month or more, what size of starter would you use to reinvigorate it?

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[MyQul]

Cheers MyQul.

One last question (hopefully) :

if you harvest say 300ml of slurry, but don't use it for a month or more, what size of starter would you use to reinvigorate it?

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I month isnt that long to keep (Ive got yeast in my fridge fridge from the end of last year). 1L - 1.5L will do the job if the yeast is relatively 'clean' (the equivalent of if you'd rinsed it, not with loads of break material in their.) and you'll only need about 100ml in the starter not the whole 300ml

 

[Gerryjo]

I'm pretty new to harvesting yeast and read up extensively beforehand as I do whenever I try a new technique. The majority of advice seemed to be that as long as you repitch in 1-2 weeks the starter isn't necessary. Some seemed to insist that a starter was best practice, others insisted that rinsing the yeast isn't even necessary and repitching the slurry mixed in with a little of the beer from the end of the previous batch is fine. There doesn't seem to be a definitive answer as is the case with all things homebrew!

That's exactly it there's no definite answer but what you can do is to try all approaches which will all work but use the method that suits you best and you're most comfortable with.

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