Yeast Starter: How Much Stirring is Too Much Stirring

[Garrett_McT]

I am doing my first yeast starter with 280 mL of approx. 1.036 gravity wort and WLP320 pure pitch yeast at approx. 33% viability. It is in a 2000 mL Erlenmeyer flask and on astir plate.

How much stirring is too much stirring?

 

[GoeHaarden]

Not sure a normal stir plate would ever be too much.

Just curious, what is your end goal with this starter? Asking because I question your rather small (280mL) starter with such low viability. Stepping it up? Doing a small batch?

 

[day_trippr]

Even for my 5 liter starters I give them 24 hours then pull the stir bar and crash hard.

What yeast starter calculator are you using? Those numbers give a 1.21x increase in cell count and would require another pass to come up with enough cells for a 5 gallon batch of ~55 point gravity...

Cheers!

 

[Garrett_McT]

Not sure a normal stir plate would ever be too much.

Just curious, what is your end goal with this starter? Asking because I question your rather small (280mL) starter with such low viability. Stepping it up? Doing a small batch?

I am making a 2.5 gal batch of a 1.048 OG Hefeweizen. I am under pitching at like 60% of what BeerSmiths calculator calls for. If things go well maybe I could use the slurry for a second batch for my Oktoberfest party on Oct 2

 

[GoeHaarden]

I am under pitching at like 60% of what BeerSmiths calculator calls for.

On purpose? I've never bought into the whole idea to under pitch for more yeast character.

If you're wanting to use the yeast for another brew it might be a better idea to just build the largest starter capable and then save half for the second brew. That way you can pitch clean yeast.

 

[Golddiggie]

With starters, I use either of a couple of calculation tools to figure out what size to make for the batch (size and OG). Typically a two, or three, step process. I was using the one built into BeerSmith for the last several I made and went as close to the needed cell count as possible (in 1L increments). I would set the stirplate to create a nice vortex in the flask, without throwing the stirbar, and let it finish. Depending on the age of the yeast would determine how long that was. I would then chill the starter in the fridge for 24-48 hours, decant and either do a second, or have it ready to pitch.

I would never under pitch by more than a few percent if at all possible. Working the starter sizes to get as close as possible, or a hair over, the cell count called for. I'd rather over pitch than under pitch.

 

[Craiginthecorn]

18 hours is what I have seen cited. Also, most brewers use too much speed on their stirplates. The object is to keep the cells in suspension and maybe add a bit of oxygen. A big vortex can create too much agitation which can damage the cell walls. But don‘t sweat it too much.

 

[Golddiggie]

18 hours is what I have seen cited. Also, most brewers use too much speed on their stirplates. The object is to keep the cells in suspension and maybe add a bit of oxygen. A big vortex can create too much agitation which can damage the cell walls. But don‘t sweat it too much.

A decent vortex is what you want. I also use the foam stoppers (sanitized) in my flasks to allow full gas exchange. It allows CO2 out and the entry of oxygen without allowing any bugs inside. I know people use sanitized aluminum foil 'hats' on flasks, but [IMO] that leaves an entry for bugs (either insect of smaller) from getting into the starter. The foam stoppers are easy to get, and cheap enough, that using them should be a 'no brainer'. Even for the largest of skinflints.

 

[Craiginthecorn]

A decent vortex is what you want. I also use the foam stoppers (sanitized) in my flasks to allow full gas exchange. It allows CO2 out and the entry of oxygen without allowing any bugs inside. I know people use sanitized aluminum foil 'hats' on flasks, but [IMO] that leaves an entry for bugs (either insect of smaller) from getting into the starter. The foam stoppers are easy to get, and cheap enough, that using them should be a 'no brainer'. Even for the largest of skinflints.

Foam stoppers are fine, but if you use them, make sure that there's sufficient head space in your flask in case of foaming. I don't believe you can sanitize a foam stopper nearly as well as foil. I've used both, but slightly prefer foil.

 

[Golddiggie]

Foam stoppers are fine, but if you use them, make sure that there's sufficient head space in your flask in case of foaming. I don't believe you can sanitize a foam stopper nearly as well as foil. I've used both, but slightly prefer foil.

I put the stoppers in my bucket of Starsan, letting them get fully saturated and squeezing it out (and then letting more take it's place) several times before finally getting them clear of Starsan and used. Probably at least as sanitized as your foil, if not more so.

I typically only make 1L of starter in my 2L flask. In my 3L flask, I don't go with more than 2L of starter (or add that much starter wort). Using a drop of fermcap also keeps foaming under control.

 

[Vale71]

A big vortex can create too much agitation which can damage the cell walls.

You'd have to venture into ultra-centrifuging territory to cause any actual damage to the cells. Yeast won't even notice it's being spun by a laboratory-grade stir plate. The only real issue with excessive turning speed is the bar possibly flying off and you only noticing much later.

 

[cactusgarrett]

I understand it to be that you only need to stir fast enough to create a small dimple in the surface. This provides enough agitation to off-gas CO2 while having enough liquid exchange to expose it to air (oxygen). A vigorous stir (again -from what i understand) is detrimental due to the potential to introduce shear stress.

Rabbit hole time:
https://www.homebrewersassociation.org/forum/index.php?topic=23610.15https://www.homebrewersassociation.org/forum/index.php?topic=21705.msg276016#msg276016

 

[ScrewyBrewer]

As a general guideline, try to spin the starter wort just fast enough to create a vortex in the wort about as long as a fingertip. It only needs to keep the wort in motion gently to get the job done.

 

[Holden Caulfield]

Regarding stir plate rate and vortex. - I will offer up no opinion, as that is what it is without any of my own controlled experiments, but here is some quantitative analysis that demonstrates higher is better. Below is the graph of results. Check out the article from Braukaiser to see the visual of what is considered high and more details on the vortex size, experiment, analysis, and conclusions.

http://braukaiser.com/blog/blog/2013/03/25/stir-speed-and-yeast-growth/

 

[cactusgarrett]

Good points. "Higher is better" jibes if just growth is desirable. However, we're also in the business of healthy yeast. Reading up on yeast shear suggests that produces somewhat unhealthy yeast, though. I'm with Holden on this, though - I can't offer up an opinion to say what's best, but I just wanted to set the table with all potential variables.

 

[Vale71]

Good points. "Higher is better" jibes if just growth is desirable. However, we're also in the business of healthy yeast. Reading up on yeast shear suggests that produces somewhat unhealthy yeast...

What material have you been reading exactly? If you're referring just to the links you posted that's just pure speculative conjecture from an unqualified poster who reports his starters "smelling foul" when the stir plate is run at a high speed. Hardly conclusive proof, wouldn't you agree?

 

[Garrett_McT]

I am simply taking in info on this post, but foe the record @Holden Caulfield nice name, hopefully home brewing keeps you young. Never grow up my friend