Stir plates. How effective are they?

[Braufather]

Looking at the pitch calculators it looks like a stir plate can make a massive difference, trebling or quadrupling yeast cells. Does peoples experience bear this out?

I’m never going to build one but you can buy them quite cheap now, cheaper in fact than buying a bigger flask. I’ve a standard 2litre flask to make 1 litre starters.

If I use a stir plate , would that give me enough cell growth in a 1 litre starter to cover at 19 litres at a max of 1065OG? let say the yeast is 3 months old at worse case. (never needing to step up or do do bigger starters?). Brewers friend calculator seems to say so But I’d be interested in people’s experience.

just for ales, not lagers.

Alternatively I’ve a 3 litre mason jar I could make 2 litres starters in but as I understand it the smaller surface area compared to 1 litre in my 2 litre lab flask may negate any benefits?

 

[BlackRegent]

Brewfather suggests a 2.3L starter for 19L of 1.065 wort using 3 month old yeast IF you overbuild your starter by 100 billion cells (so that you can reserve some of your starter for the next batch). If you didn't do any overbuilding, it suggests a 1.5L starter

 

[The-Engineer-That-Brews]

the smaller surface area compared to 1 litre in my 2 litre lab flask may negate any benefits?

FWIW I think that except in the very early stages, the benefit of the stir-plate comes from keeping the yeast in suspension and keeping the nutrients and by-products moving past, rather then the oxygenation - otherwise you might just as well use an ayirstone instead. I've found that a Mason jar works just fine; I've used a large (5L) one for a larger starter but the only problem is that because the base is slightly domed it's quite hard to keep the stir-bar centred and you have to use a slow speed to stop it spinning out.

That said, despite the chorus of voices warning about the dire consequences of under or over pitching, the controlled experiments I've read about seem to suggest that it's a small effect. For example, this is well worth a read: Yeast Pitch Rate: Underpitch vs. Overpitch In A Lager | exBEERiment Results!

For a 19L ale I'd not have any qualms about pitching with a 1L starter done on the the stir plate - although what you're brewing there is higher than the OGs I've got experience of.

It really is worth using a stir plate though - makes a huge difference to the amount of yeast growth. I know you say you'd never make your own, but all you need is an old PC cooling fan - or even a Lego motor - and a couple of rare earth magnets stuck on it with hot glue.

 

[Braufather]

Brewfather suggests a 2.3L starter for 19L of 1.065 wort using 3 month old yeast IF you overbuild your starter by 100 billion cells (so that you can reserve some of your starter for the next batch). If you didn't do any overbuilding, it suggests a 1.5L starter

is that with a stir plate? can you do a 1.5 litre starter in a 2 litre flask or will the surface area be to far reduced?

 

[Braufather]

FWIW I think that except in the very early stages, the benefit of the stir-plate comes from keeping the yeast in suspension and keeping the nutrients and by-products moving past, rather then the oxygenation - otherwise you might just as well use an ayirstone instead. I've found that a Mason jar works just fine; I've used a large (5L) one for a larger starter but the only problem is that because the base is slightly domed it's quite hard to keep the stir-bar centred and you have to use a slow speed to stop it spinning out.

That said, despite the chorus of voices warning about the dire consequences of under or over pitching, the controlled experiments I've read about seem to suggest that it's a small effect. For example, this is well worth a read: Yeast Pitch Rate: Underpitch vs. Overpitch In A Lager | exBEERiment Results!

For a 19L ale I'd not have any qualms about pitching with a 1L starter done on the the stir plate - although what you're brewing there is higher than the OGs I've got experience of.

It really is worth using a stir plate though - makes a huge difference to the amount of yeast growth. I know you say you'd never make your own, but all you need is an old PC cooling fan - or even a Lego motor - and a couple of rare earth magnets stuck on it with hot glue.

haha defo wont make my own, but good to hear they make a significant difference.

Will read that link later, i like those guys but the more you read them the more you think nothing matters! i notice they discount stuff with their experiments but then continue with the same process, as if they don't trust their own findings themselves! its a good read though and comforting at times for lazy brewers such as myself!

 

[BlackRegent]

is that with a stir plate? can you do a 1.5 litre starter in a 2 litre flask or will the surface area be to far reduced?

On a 2L flask, the difference in surface area between a 1L and a 1.5L volume isn't that great. Also (and I'll be corrected if I'm wrong) the main air intake is through the vortex that a stir plate creates

 

[Braufather]

Ok, so what I’m thinking is getting a stir plate and start doing 1.5 L starters. Then depending on the age of the yeast and the OG, I’ll either pitch the lot if needed or if it works out save some back for a starter for next brew.

 

[The-Engineer-That-Brews]

Sounds good to me It‘s worth getting a selection of stir-bars too, because sometimes one size seems to work better than others.
Top tip for putting in and retrieving the stir bar by the way is to use a metal skewer, sterilised over the gas.
Wort is quite a bit more viscous than water so don’t be surprised if you don’t get much of a vortex (and you don’t need one anyhow).
I‘ve only done a small number of stirred starters, but the experience is a bit different to the non-stirred ones. My ones have developed no kräusen, but after 24-48 hrs you can see they they start looking slightly curdled/granular at the side wall due to the flocculation; but it’s worth giving them a further 12-24 hrs before switching off. They clear down quite fast initially then need maybe 12hrs to drop fully clear (I guess depending on the yeast)

 

[peebee]

...
the benefit of the stir-plate comes from keeping the yeast in suspension and keeping the nutrients and by-products moving past, rather then the oxygenation ...

...
if you don’t get much of a vortex (and you don’t need one anyhow) ...

Sorry, but ... @The-Engineer-That-Brews is expressing the common "denial" these days: Oxygen is bad, don't let it come anywhere near your beer.

But for yeast to grow rapidly and healthily, it needs oxygen. The stir-plate accelerates the transfer of gases (oxygen in, CO2 out). The other mistake is to fit a airlock or like to the flask's neck - use cotton-wool or one of those special anti-bug foam bungs.

The starter liquid is oxidised. I do try to avoid pouring it all into the wort by allowing the starter a few hours in the cold and decanting off most of the clear starter solution. Use multi-step starters (two is usually enough) limiting each step to 12-24 hours to avoid huge starters (start small and step up), but I brew 45L+ batches so single-step starters are often enough for 20-25L batches.

Avoid over-filling the flask, 1-and-a-bit-Litre in a 2L flask is probably enough or the stir-bar will probably be quite ineffective.





Something that always bothers me: You go to the trouble of growing enough yeast cells to do the job in a manner that ensures they have plenty of reserves of oxygen to be going on with, then go to the extra trouble of dissolving more oxygen into the wort for the yeast to grow (which it doesn't need).

Why?

But I keep aerating my worts, I'm not stopping just yet (although I don't bother for 20L batches using dry yeast).

For example (Tilt screenshots). This is dried yeast, wort not aerated, and BRY-97 yeast which is notoriously slow starting and sedate fermenting (also 2 months past best-before, but I don't recommend that!):

3 days. Not too tardy, just "sedate".

 

[The-Engineer-That-Brews]

Sorry, but ... @The-Engineer-That-Brews is expressing the common "denial" these days: Oxygen is bad, don't let it come anywhere near your beer.

Get yer fact rights old chap! I never said that :-) :-) .... indeed, I agree with you on the benefits of oxygen for yeast growth.

I was merely expanding on my previous opinion that the reason stir plates work well is not because they oxygenate more (if that were the case then you might as well just use an air-stone), but rather that they keep the yeast in suspension and the nutrients and byproducts circulating past

 

[Braufather]

One thing everyone is agreed on is recommending stir plates At least!

will this do the job?

https://www.geterbrewed.com/magnetic-stir-plate-2-litre/

in the meantime I’ve got a starter on the go since last night fir a brew tomorrow. I wondering if I’ve time to cold crash it tommorrow morning for a few hours.

 

[peebee]

Get yer fact rights old chap! I never said that :-) :-) .... indeed, I agree with you on the benefits of oxygen for yeast growth.

I was merely expanding on my previous opinion that the reason stir plates work well is not because they oxygenate more (if that were the case then you might as well just use an air-stone), but rather that they keep the yeast in suspension and the nutrients and byproducts circulating past

Aye ... but I was trying to tread carefully as I was surprised I was criticising you. But what you said was playing into the hands of the "craft brewing" mis-information brigade, so I felt I needed to insert a bit of sanity (says the guy with the ID card explaining "sanity" might not be my best asset).

I don't think you can get away with an air-stone (I have considered it!)? Stirrers do the job considerably more "subtly". But they do need to create that vortex to get decent gas-transfer The times I've had weak vortex has been down to overfilling the flask.

 

[Braufather]

That sort of confirms what I though about volume limited for a 2 litres flask. I have sort of settled on 1.1 or 1.2 litres.

 

[The-Engineer-That-Brews]

Aye ... but I was trying to tread carefully as I was surprised I was criticising you. But what you said was playing into the hands of the "craft brewing" mis-information brigade, so I felt I needed to insert a bit of sanity (says the guy with the ID card explaining "sanity" might not be my best asset).

I don't think you can get away with an air-stone (I have considered it!)? Stirrers do the job considerably more "subtly". But they do need to create that vortex to get decent gas-transfer The times I've had weak vortex has been down to overfilling the flask.

Ah mate - I'd never take offence at you :-) My tongue was firmly in my cheek

Yes you're right I'm sure, about the vortex thing, but I do struggle to get a decent vortex going in wort with my DIY setup without the stir bar spinning out (it seems to be fine in water...?). Even so, I feel like just stirring the liquid around so that differs parts of the fluid are at the surface for gas exchange is better then nothing :-)

 

[The-Engineer-That-Brews]

Looks alright doesn't it... if you get one, have a peek inside the box and see if it's just an old PC cooling fan with a couple of rare earth magnets stuck to it

https://www.geterbrewed.com/magnetic-stir-plate-2-litre/

 

[Braufather]

if i took it apart id put it back together all wrong so best left alone i reckon!

 

[peebee]

Ah mate - I'd never take offence at you ...

Okay, now we've got that settled amicably ...

Get yer fact rights old chap! ...

What's this "old chap" business?

 

[The-Engineer-That-Brews]

Okay, now we've got that settled amicably ...


What's this "old chap" business?

Oh deary me, you’re quite right -you could be a chap-ess for all I know!

 

[Braufather]

The starter liquid is oxidised. I do try to avoid pouring it all into the wort by allowing the starter a few hours in the cold and decanting off most of the clear starter solution. Use multi-step starters (two is usually enough) limiting each step to 12-24 hours to avoid huge starters (start small and step up), but I brew 45L+ batches so single-step starters are often enough for 20-25L batches.

Oxygen is good here right? Just before pitching. Not sure I’ll have time to cold crash so most likely will pitch most of it.

 

[peebee]

Good for the yeast, not so good for the starter liquid (taste it ). But it is very unlikely that flavour transfers into considerably larger volume of the beer. So play it by ear, you don't want to be decanting off perfectly good yeast still in the bulk of the beer.

And if you cool the starter you are supposed to allow it to warm again before pitching.