Yeast starter flask volume

[kaiserben]

How big a starter can I fit in a 3L erlenmeyer flask if I don't have anything to control foam? (will be using a stir plate for the first time and I need to get as close to 3L as I can to reach my required cell count).


Will be pitching WLP838 (71% viability). I need 425 million cells (would rather over- than under-pitch).

Was going to do a 2-step starter. Yeastcalc says I can get there by:
1st step 0.7L
2nd step 3L

But I assume doing 3L in a 3L flask without fermcap or something will make a huge mess?

Also, can I do both steps in the same flask? Or should I do earlier steps in a smaller vessel (like a cleaned and sanitised PET bottle? If so, can I do it without an airlock? Maybe just have the lid on but not airtight?)

 

[slcmorro]

Mate, with a stirplate you'll barely get much of a krausen. The spinning action knocks it down. I would personally leave at least 500ml of headspace though - filling to the top can get messy.

Not sure there's science behind my reasoning, but I like to think a bit of headspace helps the CO2 blow off better and promotes more efficient oxygen exchange.

What you can do to increase your cell count without overfilling your flask, is pop it in the fridge after your first step. Then, 12 hrs later pour off the spent wort and add your new fresh wort to the flask afterwards. Boil up your DME in a seperate saucepan and let it cool, and then pour it into your flask with your yeast in the bottom. Make sure you take the flask out of the fridge for a few hrs before doing this, to let the yeast come up to a decent temp too - thermal shock and all that jazz.

 

[Crusty]

Mate, with a stirplate you'll barely get much of a krausen. The spinning action knocks it down. I would personally leave at least 500ml of headspace though - filling to the top can get messy.

Not sure there's science behind my reasoning, but I like to think a bit of headspace helps the CO2 blow off better and promotes more efficient oxygen exchange.

What you can do to increase your cell count without overfilling your flask, is pop it in the fridge after your first step. Then, 12 hrs later pour off the spent wort and add your new fresh wort to the flask afterwards. Boil up your DME in a seperate saucepan and let it cool, and then pour it into your flask with your yeast in the bottom. Make sure you take the flask out of the fridge for a few hrs before doing this, to let the yeast come up to a decent temp too - thermal shock and all that jazz.

I beg to differ on flask size.
It depends on what yeast you have & how much of a beast it is.
I made a stepped starter in a 2lt flask & then onto a 5lt flask ( 2.5lt total wort ) & during the night, the Krausen climbed out the flask pushing my foil lid off & spewing out onto the kitchen bench. WLP400, what a beast!

edit: I was using a stir plate.

 

[mckenry]

Mate,
Just go 1.25L. Ferment it out (about 24hrs should see it done) Turn the plate off and decant the beer when the yeast has settled.
Boil up 2L in another pot. Cool it and add it to your yeast. Plenty of room left in the flask and youll end up with over 500B cells.
Good for lager.

Edit - in my experience, I dont get much krausen on the first step, but second and third can throw huge krausen.

 

[kaiserben]

Thanks for the tips everyone.

I assume it's okay to get a bit of no-rinse in my flask? For example, when I decant spent wort and add fresh wort I can spray the lip of the flask liberally with no-rinse?

How do people measure temp inside a 3L flask? (my longest thermometer doesn't quite reach the top of the flask. I either have to touch inside flask with my fingers (assume that's a huge no-no), or sanitise a pair of bbq tongs and try to get the thermometer in and out with tongs. Or do people just guesstimate temps when combining wort and yeast?

I began my first starter overnight. Please correct me if any of this is the wrong idea:

1st step: Went with 0.9L starter. Will leave on stir plate for 36 hours. Then put in fridge for 12 hours (till I've got time to make 2nd starter).
2nd step: Will ditch spent wort before adding 2.2L of fresh wort. Will leave on stir plate for 36 hours. Then in fridge until ready to pitch a few days later.
Pitching to main wort: Will ditch spent wort, kepping enough to stir up yeast cake for pitching.

 

[Mr B]

Thanks for the tips everyone.

I assume it's okay to get a bit of no-rinse in my flask? For example, when I decant spent wort and add fresh wort I can spray the lip of the flask liberally with no-rinse?

How do people measure temp inside a 3L flask? (my longest thermometer doesn't quite reach the top of the flask. I either have to touch inside flask with my fingers (assume that's a huge no-no), or sanitise a pair of bbq tongs and try to get the thermometer in and out with tongs. Or do people just guesstimate temps when combining wort and yeast?

I began my first starter overnight. Please correct me if any of this is the wrong idea:

1st step: Went with 0.9L starter. Will leave on stir plate for 36 hours. Then put in fridge for 12 hours (till I've got time to make 2nd starter).
2nd step: Will ditch spent wort before adding 2.2L of fresh wort. Will leave on stir plate for 36 hours. Then in fridge until ready to pitch a few days later.
Pitching to main wort: Will ditch spent wort, kepping enough to stir up yeast cake for pitching.

I usually guestimate. Get to room temp and maybe a bit cooler than the bench (not a certified temp ). For starters in the ballpark is ok.

Since you use a calculator I assume that your wort volumes etc give you the required cell numbers. Process looks good - You may have already done it so just take this as reassurance B)

For each step, I usually wait until the C02 bubbles finish - you'll know what I mean when you do it if not already.

All the best

edit: Little bit of no rinse is ok. I prep my starters in the erlenmeyer with a foil cap so the lip is mostly sanitary, but if you are tipping in from a saucepan etc no probs with a bit of a spray

 

[kaiserben]

Right now I'm in the middle of my second step. I've got roughly 2.3L in the flask and it's 24 hours in. No massive krausen, but it's obviously active and I suppose big krausen might still be on the way (hopefully the stir plate keeps it down).

I stopped the first step after ~33 hours and think I probably stopped earlier than I should have.

I'm much more confident about the process now that I've done it twice (well once, but 2 steps).

 

[kaiserben]

For each step, I usually wait until the C02 bubbles finish - you'll know what I mean when you do it if not already.

This was good advice.

Even though I never saw obvious krausen there were bubbles (although not many) at the surface while it was active. After about 48 hours there was no bubbles and the surface was like a glassy ocean. It was obvious once it happened.

 

[buckerooni]

a slight tangent but of interest around starters - - this guy who's experiments are great reads: http://brulosophy.com/2015/06/29/yeast-pitch-rate-pt-2-viable-cell-count-vs-vitality-exbeeriment-results.

from the article: Purpose: To evaluate the differences between a conventional yeast starter made to increase viable cell count and a starter produced a few hours pre-pitch to increase yeast vitality when used to ferment a split-batch of the same wort.

 

[technobabble66]

a slight tangent but of interest around starters - - this guy who's experiments are great reads: http://brulosophy.com/2015/06/29/yeast-pitch-rate-pt-2-viable-cell-count-vs-vitality-exbeeriment-results.

from the article: Purpose: To evaluate the differences between a conventional yeast starter made to increase viable cell count and a starter produced a few hours pre-pitch to increase yeast vitality when used to ferment a split-batch of the same wort.

He does a beer quality experiment using a DIPA?!?
Is it just me or is there something seriously wrong with this?
I appreciate high alcohol beers test out the yeast much more, so merit in doing an 8.5% beer; but with so many hops in there how well would any flaws stand out?

That aside, it's a great little mini-experiment he's done that may indicate some useful changes to brewing practices, namely the use of a 4-6 hr starter instead of a 48hr starter.
He also points out a major consideration of this concept - that the yeast needs to be healthy in the first place (ie: his 2 vials were 2 months or less old).

It'd be great to see several follow ups on yeast of different ages, different levels of under pitching, and different strains of yeast.

More importantly: do the experiment(s) with something like a kolsch or a Scottish ale to really reveal any differences in quality.

EDIT: fwiw, I'd be tempted to give it a crack next time I'm brewing, just use a quick 4 hr starter to rev up those yeasties, then chuck it all in. Mainly for lack of time management than being converted to this technique. But it at least suggests it'll help and be worth the little extra effort.

Apologies for the OT

 

[TheWiggman]

I began my first starter overnight. Please correct me if any of this is the wrong idea:

1st step: Went with 0.9L starter. Will leave on stir plate for 36 hours. Then put in fridge for 12 hours (till I've got time to make 2nd starter).
2nd step: Will ditch spent wort before adding 2.2L of fresh wort. Will leave on stir plate for 36 hours. Then in fridge until ready to pitch a few days later.
Pitching to main wort: Will ditch spent wort, kepping enough to stir up yeast cake for pitching.

Yeast health when stepping is discussed a bit here but hard to find. I used to use your line of thought (i.e. step up given the limits of my flask, do it 2 or 3 times with similar volumes) but it's bad practice.
Check out this post by Wolfy who does a good job at explaining the risk with small incremental starters. There is good info in the following posts too. Essentially, when stepping, you want to increase the starter volume between 5 - 10x to encourage the appropriate growth and maintain good yeast health.

If you are intending to increase cell count after the first step, the next step needs to be minimum 5 x the volume of the last. Hence if you did a 900ml starter, after decanting the spent wort you want to add 5 x 0.9 = 4.5l. You'll need a 5l flask.

My preference (with fresh yeast and 19-23l batches) is to do a single step with a single pack. For 19l of a 1.046 OG lager I'll need about 325 billion cells. Assuming 90% vitality from a fresh pack of yeast, I pitch into 3l of 1.040 wort using O2 and a bit of yeast nutrient and run the stir plate until it's done at about 25°C. This will give me a theoretical count of 350 billion cells (at least), putting me right in the sweet spot.

In your case if you need 425 billion cells, you can do that with a 5l starter with a single pitch (stir plate). So either way you look at it if you want good yeast health with a single smack pack you're going to want a 5l flask.

 

[kaiserben]

Thanks for that. It also helped me better understand what was going to be my next question, ie how much yeast cake would I need to rescue to use in my next lager. But I'm still not sure I've got it ...

Looking at Wyeasts instructions for estimating cell count, http://www.aussiehomebrewer.com/uploads/albums/1320903318/gallery_14391_695_116230.jpg

I need to rescue my slurry, let it settle in the fridge, and decide what percentage of yeast solids it has.

Assuming it has 40% yeast solids, I would have 1bn cells per ml.

If my next lager batch requires a pitch 425bn cells then I would require 425ml of that same yeast slurry.

Is that right?

 

[TheWiggman]

I can't confirm actual count but be wary that when harvesting 'yeast' from a batch you need to separate the yeast from the trub. If you haven't washed the yeast then there'll be a fair swag of other stuff in there you don't want to pitch into a fresh batch. If you have washed it, then 40% is probably a fair estimate.
If you have more than 425ml then use it. For a lager I would pitch as much as possible, the risk of under pitching lagers is far greater than over pitching.