Another question about yeast starters/slurry

[cc986]

I've decided that the next thing I want to try to master is harvesting and cultivating yeast from my own brews and from commercial beers. To be honest, my brain still hasn't really recovered from the last couple of years attempting to understand water chemistry, but I have to move on at some point.

Last week I harvested 500ml of yeast slurry from the bottom of my fermenter with the intention of using it to practice creating my own starters from my own yeast. After settling in the fridge for a few days I had a first attempt and used an online yeast starter calculator to work out how much DME and water to use for a 23 litre batch.

In the section where it asks for the starting amount of cells per billion, I entered 159 billion (because I didn't really have a clue and read somewhere that this was the rough amount per 100ml of slurry...) and the calculator responded by telling me to create a 0.6 litre starter using 59g of DME to get an SG of 1.036. So that's what I did, and once it had cooled down I poured in 100ml of slurry. All appeared to go well at first and within a few hours there was a nice krausen and what looked like a good fermentation going on. But when it had clearly stopped, I measured the SG and it was only 1.011.

If I was to guess, I would say that the amount of DME was far too low, but it could also be that I input an unrealistic number of cells, so my questions are:

1. How do I know how many billions of cells there are in, for example, 100ml of yeast slurry? I suspect there are multiple factors at play that prevent a definitive answer to that, but is there a good figure to work to?

2. Is there such a thing as an amount or ratio of DME to add per ml of yeast slurry or water?

One other thing just came to mind. The slurry was harvested from WHC labs Bond yeast which fermented a 19 litre batch of 7% beer. To say it was aggressive during fermentation is an understatement and the inside of my fermentation chamber looked like the aftermath of a volcanic explosion, so I guess it could be that the yeast was worn out, although it did get going quickly in the test and looked fairly active.

I have already done a fair amount of reading up on this, including on this site, but I'd still really appreciate any additional responses.

Thanks,

Chris

[MashBag]

Chris,

I read all the numbers. Blew my mind.
I stir up all the slurry & beer from the bottle of my kettle/fv and bottle it.
Normally 3 bottles. Stored in the fridge.
When I repitch, I allow it to get to room temp and then pitch what pours easily. The sediment stays a in the bottle.

Don't do more than 3 gens

[IPA]

Tomorrow I will post pictures of my method. Dead simple. Don't worry about cell counting. I am still using yeast that I bought ten years ago. I have revived yeast from bottles of beer that were thirty years old and several of them are now in BrewLab's yeast bank.

[cc986]

Mashbag,
Thanks very much. Without possibly knowing exactly how many billion starting cells there are, I couldn't understand how those calculators could possibly be effective, so I did wonder if there was a simple solution like yours. And I think I read on another thread here on JBK that someone else does something similar to you (or maybe it was you).
Thanks again,
Chris

[cc986]

Tomorrow I will post pictures of my method. Dead simple. Don't worry about cell counting. I am still using yeast that I bought ten years ago. I have revived yeast from bottles of beer that were thirty years old and several of them are now in BrewLab's yeast bank.

Great - looking forward to that, thanks!

[nallum]

It doesn’t really matter how many cells per ml are in a yeast slurry. What matters more is how many are alive (viable) and how vital (healthy) they are. The fresher the repitched yeast, the better, with more being alive at higher vitality therefore less slurry required. Best repitched directly within days to a week or so. Otherwise a starter is recommended. The older the slurry gets the more you’ll need. You might even reach a point where you’re better off stepping up from a small starter using a little slurry. It’s just something best determined empirically by you satisfying your expectations.

Online calculators ‘work’ because they have a big fudge factor and, when they fail, the home brewer thinks he did something wrong and usually is too reluctant to say anything about ‘his mistake’, because he believes these mysterious calculators actually work. A biased belief system. They basically just get you to make a starter. Combined with a little common sense, it should work regardless of the calculated numbers.

Don’t overthink it. It’s only beer. No need to get too scientific about it with, say, a microscope. You don’t need a reliable estimate of viable cells and the levels of vitality, just observe how they perform in your FV wort or starter relative to what you did. If left in the fridge for a month or two the yeast slurry is going to be relatively sluggish.

I probably wouldn’t repitch yeast from a higher gravity (OG>1.060) beer, but it depends on the yeast strain. The portion of slurry in bigger beers is best sacrificed. There’s normally more than enough to get away with sacrificing some.

Ideally, with wet yeast fit for repitching, fermentation starts within several hours. Certainly within <12 hours. If it takes longer, something about what was done is suboptimal and not really maximising the benefits of efforts to repitch yeast. It’s not just more cost effective, it’s about repitching the best yeast possible. The brewer’s biggest ‘secret’ weapon.

Some home brewers don’t mind if it takes longer, even days, for fermentation to start. It’s your brew, your choice. The longer it takes to start the higher the risk of subtle off flavours in the final beer.

I would definitely recommend using a yeast nutrient supplement containing zinc too when repitching yeast. Something like lallemand servomyces. A 10g sachet last me ages.

[cc986]

Thanks very much nallum.

[IPA]

As promised here is my method of saving yeast
36 hours into the ferment take a sample of the fermenting wort and almost fill a swingtop fitted with an airlock using one of these.
https://www.northernbrewer.com/products ... e5eGZGp-V7
This is a piccie

P1010614.JPG (154.5 KiB) Viewed 4143 times

When fermentation has finished remove the airlock and seal the bottle with the swingtop. Store at room temperature for 14 days.

P1010632.JPG (158.5 KiB) Viewed 4143 times

I store my bottles in a dedicated fridge

P1010635.JPG (153 KiB) Viewed 4143 times

When you want to use the yeast pour most of the now beer into a glass and check that it is not contaminated by DRINKING IT. Your tongue is a very sophisticated instrument.
Swirl the bottle to dislodge the yeast stuck to the bottom and add it to a 300ml starter wort at 1040. then when it is fermenting happily step up to a 1200ml starter. When this is ready pitch it into you next brew.
It really is that easy.
I try to use my samples within one year but they remain viable for at least two years.
Good luck
Ian

[nallum]

I like that method, Ian. You’re basically selecting for viable yeast cells active in suspension. Kind of like top cropping in that respect, even for bottom-cropping strains.

[cc986]

Hi Ian,
I like that as well. So you just plunge the wine thief in through the top of the fermenter and you should get some yeast with it? Have you tried drawing it out through a tap at the bottom of the fermenter instead of the wine thief?

[IPA]

Hi Ian,
I like that as well. So you just plunge the wine thief in through the top of the fermenter and you should get some yeast with it? Have you tried drawing it out through a tap at the bottom of the fermenter instead of the wine thief?

If you take the sample via the tap it is difficult to sanitise the tap afterwards.

[cc986]

Hi Ian,
I like that as well. So you just plunge the wine thief in through the top of the fermenter and you should get some yeast with it? Have you tried drawing it out through a tap at the bottom of the fermenter instead of the wine thief?

If you take the sample via the tap it is difficult to sanitise the tap afterwards.

Yes, good point.
I have two fermentation chambers, one small one that I use for primary and a second tall one like yours that I use for conditioning beers and there's plenty of room in it for some extra bottles. I really like your method so I'm definitely going to be giving that a go from now on. Thanks very much for posting all that information.
Chris

[guypettigrew]

If it's any help, my method is taken from IPA's. I sanitise a jug, then scoop half a litre or so from the top of the fermenting beer, including the krausen.

Tip it into a kilner jar and put it in the 'fridge. It carries on fermenting, even at 4°C. The kilner jar allows exces gas to be released as neccesary.

Super easy.

When it's time for a brew I put about 120g of malt extract into 1 litre of water. Boil it for 10 minutes, cool it to about 20°C, put it on a stir plate. Then the clear liquid in the kilner jar is tipped off the yeast sediment. The yeast is swirled round in the small amount of liquid left behind and tipped into the malt extract.

Ready for use a couple of days later.

As nallum says, 'don't overthink it'!

Guy

Edit; See new bit in italics above--forgot to mention about getting the yeast out of the kilner jar!!

[MashBag]

I like that. Possibly a smidge more work than mine, but a much cleaner outcome. And a really good test before pitching.

Ps. Can't you just spritz the tap with sanitizer?

[cc986]

If it's any help, my method is taken from IPA's. I sanitise a jug, then scoop half a litre or so from the top of the fermenting beer, including the krausen.

Tip it into a kilner jar and put it in the 'fridge. It carries on fermenting, even at 4°C. The kilner jar allows exces gas to be released as neccesary.

Super easy.

When it's time for a brew I put about 120g of malt extract into 1 litre of water. Boil it for 10 minutes, cool it to about 20°C, put it on a stir plate. Then the clear liquid is tipped off the yeast sediment. The yeast is swirled round in the small amount of liquid left behind and tipped into the malt extract.

Ready for use a couple of days later.

As nallum says, 'don't overthink it'!

Guy

Thanks Guy - I was just about to ask how much DME to add to the starter.