How to calculate the amount of harvest yeast into next batch?

[RawAbility3]

Good morning all.

I am currently strugelling finding out how much yeast to pitch into my next batch of beer.
I have just started to wash and collect my liquid yeast and now have 4 x Mason jars sitting in my fridge.
So I have googled and found that their are 3 options to determine how much yeast I have... Volume size, weight or cell count.

The difficulty is that I find all 3 complex for example.
Volume - how do I measure the creamy white layer of slurry/yeast?
Brewers friend calculator uses a litre as their prefilled calculation so guess that 1 jar would be roughly 10ml = 0.04?
Take it I would need all 4 x jars and starter too?

Weight - Do I just need to buy a scale that's sensitive enough to determine the weight of an empty jar and compare with one filled. If so, wouldn't their be an element of wort in this too?

Cell count - would love to try this yet looking at microscopes and the kit to go along with on sure would be a fairly expensive option.

I am just looking for the easiest way to pitch roughly the right amount of yeast.

Many thanks for your help everyone.

 

[cushyno]

This is a minefield. I'd love to have some definitive reference on yeast pitching as there is a lot of useful but conflicting and often technical info out there in internet land. Some of the referenced articles I came across from so called experts differed by 2x, 4x, or 10x on some calculations. Who is right?

What I have found is this:

• Densely packed liquid yeast is approximately 2bn cells / ml
• Decent yeast slurry without much hop/grain/protein debris is about 1bn cells / ml. This is a good estimate to use for saved yeast.
• I then use the calculator here to work out how many cells I need. Typical for me that's between 210-240 bn cells.
• A 250ml jamjar full of yeast slurry is good for one batch (so long as it's fresh).
• 250ml of slurry is approximately 1/3 of the slurry in my FV from a 23l batch.

Any time I stray from the ordinary, then I use the brewunited calculator.

As every yeast has a different cell density and health of yeast is difficult to estimate as it depends on storage conditions, age, and how much it was previously stressed, the whole calculation is based on assumptions.

You can always err on the side of caution and overpitch. However, if you want esters such as in a wit or weizen, then you will want to underpitch which may be difficult to judge correctly.

 

[BeerCat]

Was all yeast from one batch? If it was a lager i would have no issue using all of it but if its fermented at ale temps and lowish gravity i would of thought 1 jar would do. As long as its fresh. You could make a starter with one of them and pitch that at high krausen.
Sorry thats not a very scientific answer, i would love a microscope.

 

[Slid]

My method is simple and "works" in the sense that it makes beer every time!
After bottling you will have all the trub and maybe one half a litre of beer in the bottom of the FV - if you tip it up a bit.
Give it a swirl and drop the contents into a large 2L jug (Wilko sell cheap plastic ones, for instance).
Use a funnel and 4 empty 250ml PET bottles (lemonade or tonic water can be available). Fill the bottles with the trub & green beer and store in the fridge.
Just sanitise everything and chuck in the whole contents of one 250ml bottle on brew day.
Cell count? One, two, a lot...

 

[cushyno]

I'm with @BeerCat on those approximate pitching rates. 1/4 to 1/3 of the slurry is good for repitching for ale. For lager I'd use all of it.

 

[samale]

I'm with @BeerCat on those approximate pitching rates. 1/4 to 1/3 of the slurry is good for repitching for ale. For lager I'd use all of it.

This is interesting, I saved the full yeast cake from my Munich dunkel last night, split between two jars. I had only planned on using one for my Vienna lager tomorrow. Should I use both jars then.

 

[cushyno]

To be honest, I'm no expert on this. My guestimates are based on approximations throughout the calculations.

How much yeast cake did you save? What is your next batch size? How stressed would the yeast have been previously (high or low OG, high or low temperature)?
What's the OG and temperature of your next recipe?

So many questions.

If your answers are 500ml, 23l, 1.050, 11°C, 1.050 and 11°C, then I'd say pitch all of it.

 

[RawAbility3]

Many thanks for all your advice. This has been really helpful. Can I just clarify, when I wash my yeast, I am then left with a thin layer of healthy yeast on the bottom of my jar and the rest is wort. Their is no trub or cake in this jar. I take it that one would do?
If so, and I use one jar and a starter. Would it not be beneficial to use more jars and less starter so that the yeast isn't stored in my fridge for as long?
Also, on the calculator that you provided l, it has a date of production. Would this be the day that you harvested the yeast?

Many thanks again.

 

[cushyno]

I think there's a balance to be struck with starters. If you pitch too much healthy yeast into a starter you aren't making the yeast grow. Growth of new healthy cells is what you want. Also, too high an 'innoculation' makes the starter go crazy and climb out of the vessel!

If you have plenty of healthy yeast cake you may not need a starter, just repitch the yeast.

And yes, for the production date of yeast I'd say use the date that your last batch got down to final gravity. This accounts for time that you have left the beer sitting on slurry and some of the yeast will start to die off if left long enough.

 

[terrym]

If I harvest yeast from trub I collect about 3/4 pint which goes into a sanitised pint glass, and that goes into the fridge and then when I need some yeast from it, all I do is take about 4 good tablespoonful from the top and pitch that. But I don't keep the trub for more than two weeks. And the airlock is usually bubbling through the airlock within a few hours.
And that's as scientific as it gets.

 

[cushyno]

Do you usually do 10L batches at around 1.045 @terrym ? If so, 4 healthy tablespoons might be getting you about 80-90ml of yeast, which is in the same ballpark that brewunited recommends.

 

[terrym]

Do you usually do 10L batches at around 1.045 @terrym ? If so, 4 healthy tablespoons might be getting you about 80-90ml of yeast, which is in the same ballpark that brewunited recommends.

Most of my beers are about OG 1.040 and about 20 litres. The fact that it gets going reasonably quickly and I end up with lots of yeast laden trub at the end seems to indicate (at least to me ) that what I'm doing works.
However I'm always open to trying new ideas if there might be a tangible benefit.

 

[cushyno]

Most of my beers are about OG 1.040 and about 20 litres. The fact that it gets going reasonably quickly and I end up with lots of yeast laden trub at the end seems to indicate (at least to me ) that what I'm doing works.
However I'm always open to trying new ideas if there might be a tangible benefit.

Sounds great that Terry. As I said earlier all of this is an approximation. If you're scraping decent healthy yeast from the top which would have been in suspension and last to settle and won't have other debris in it, then you may be nudging on that 2bn/ml figure. If the brewunited calculator is to be believed, 20L of 1.040 wort needs ~150bn cells. So you'd be pretty close with your four healthy scoops.

I also guess that at 1.040 wort which is close to recommended starter gravity, you wouldn't be likely to stress your yeast severely even with an underpitch.

If it works for you keep doing it. Having these different views should help the OP either way.

 

[BeerCat]

This is interesting, I saved the full yeast cake from my Munich dunkel last night, split between two jars. I had only planned on using one for my Vienna lager tomorrow. Should I use both jars then.

Sounds good. . What was the OG? Mine are all around 1040 so the yeast is healthy at the end of fermentation. You don't need to pitch it all but it does not harm it. I like to get mine bubbling within 24 hours but realistically even if it takes 72 hours i have not had any issues. I just like to pitch lots of yeast so when i come to harvest it i know its not stressed.

 

[trueblue]

I've been reusing yeast when the closest thing to the internet was my kids speak and spell so there was no sort of calculator to play with and all the information came from the books of the day. I would fill a large jam jar with yeast trub and wash then a few days before brewing make a starter an always reusing within 2 weeks. These days as I like to keep a few strains on the go I do things different. A few days after fermentation has started I draw of some wort with a turkey baster fill a 500ml bottle and store in the fridge. When you want to brew just make a starter as if you were using a bottle conditioned beer. You will have bigger yeast deposits than a normal bottle conditioned beer and a taste of the beer on top will tell you if it is still OK. I have used bottles that have been in the fridge a few months.

 

[samale]

Sounds good. . What was the OG? Mine are all around 1040 so the yeast is healthy at the end of fermentation. You don't need to pitch it all but it does not harm it. I like to get mine bubbling within 24 hours but realistically even if it takes 72 hours i have not had any issues. I just like to pitch lots of yeast so when i come to harvest it i know its not stressed.

My Munich dunkel started at 1.060 and finished at 1.014. I made a 2 litre starter using wyeast Munich lager 2308. I had planned to reuse the yeast to make a bock and a Vienna lager.

 

[cushyno]

My Munich dunkel started at 1.060 and finished at 1.014. I made a 2 litre starter using wyeast Munich lager 2308. I had planned to reuse the yeast to make a bock and a Vienna lager.

If your Vienna Lager is first why not use 70-80% of the slurry for that and save the rest to build up in a starter for the bock? I think with the Bock being a bigger beer, it would benefit from a really healthy starter.

 

[Galena]

Why not make an extra 100bn cells in a 2L starter to give 300bn, then decant 0.5 litre into a Mason Jar and you have 100bn cells to make your next starter?

 

[samale]

Why not make an extra 100bn cells in a 2L starter to give 300bn, then decant 0.5 litre into a Mason Jar and you have 100bn cells to make your next starter?

That was the original plan. To over build the first starter by 1 litre. Save the litre back to make the next starter. I didn't have enough spray malt left. So the plan is to use the slurry from the Munich dunkel

 

[Braufather]

I am thinking about doing this with Belgium yeast. I plan to brew a lowper gravity beer 1045)with bought liquid yeast Then pitch the Whole cake into a Dubbel (OG 1066). Sound about right?