Yeast Starter on a Stir Plate Questions

[beermanpete]

I am using a stir plate for the first time for making a yeast starter and have a few questions about the process:

1) How long should I let it ferment before taking it off the stir plate and chillling it?
2) How much head space should I leave in the Erlenmeyer flask?
3) How fast should I run the stirrer?

Thanks.

 

[flars]

I am using a stir plate for the first time for making a yeast starter and have a few questions about the process:

1) How long should I let it ferment before taking it off the stir plate and chillling it?
I'll turn the stir plate off after 24 hours, let it sit for an hour or so and then give it a swirl. If a krausen forms the yeast is not done fermenting the wort. The amount of time on the stir plate depends more on the strain of yeast and the vitality of the yeast than a certain number of hours.
2) How much head space should I leave in the Erlenmeyer flask?
With aggressive yeasts like WY3711 or WY 3068 you will need about half the volume of a flask for head space. Other yeasts much less.
3) How fast should I run the stirrer?
The stir bar only needs to keep the starter wort moving. A vortex all the way to the bottom of the flask is not necessary. Using the minimum speed to keep the starter wort moving and the yeast in suspension will avoid unnecessary shear stress on the yeast.

Thanks.

Hope this helps. More information here comparing starters using the "shaken not stirred" method and the stir plate. Begins at post #12.
https://www.homebrewersassociation.org/forum/index.php?topic=24460.0

 

[Dcpcooks]

1) until it’s done, usually within 24-48 hours. You’ll see the yeast spinning in suspension and it will settle pretty quickly once you turn off the power.
2)depends on batch size and your flask but if you should have 20% of head space in most instances.
3) as fast as you can without throwing the bar. As you build up the culture you’ll have more resistance so you may notice it’s more likely to throw the bar towards the end if you’ve set it too fast.

 

[day_trippr]

If using a healthy culture and proper SG vs volume, ime 18 hours is plenty of time for a stirred starter to have finished...

Cheers!

 

[kh54s10]

18 - 24 hours. After that the yeast have already reproduced and are just feeding on what sugars are left in the starter.

You should not be going by headspace in the flask but by the size of a starter you need for your beer.
http://www.yeastcalculator.com/

You only need a small dimple in the surface of the starter wort. Constant agitation is enough.

 

[JonM]

The head space for me really seems to depend on the strain and ambient temperature. If it’s 70+ F, the yeast seem to get more active and more likely to make a big krausen. Strains like 001 and 1007 seem to make enormous krausens regardless of temperature. Those two always overflow if it’s warm.

Anyway, I usually put 1 L in a 2L flask. If you’re not sure you have enough headspace, put the stirplate in a jelly roll pan to contain any overflow mess.

 

[beermanpete]

Thanks for all your replies.

I have 2L flask and this starter volume is 2L so the flask is full. Fortunately it did not overflow. The yeast strain is WLP830 German Lager Yeast. After 35 hours it seemed done based on the little bit of foam at the top disappearing so I took it off and let it settle for several hours. I now have it in the fermeting chamber cold crashing for use tomorrow afternoon.

For future brews; is a 2L starter made from the standard White Labs or Wyeast package sufficient for lager yeasts and an OG in the 1.070 range? (I am going ahead as-is tomorrow. The OG is supposed to be 1.056)

Flars: I had not seems that discusssion, thanks. If shear is an issue I could use an aquarium pump to continuously aerate the starter instead. I won't be able to shake the starter frequently enough to do it any good. This will allow the use of the 1 gal. cider jugs I have with convexed bottoms (that I suspect won't work well on the stir plate).

 

[BlueHouseBrewhaus]

+^ on all of the above. One added tip - use a drop of two of Fermcap and you won't have to worry about head space.

 

[cactusgarrett]

use a drop of two of Fermcap and you won't have to worry about head space.

This. I've got only 1L flasks and i fill those right up - fermcap knocks down any krausen that would otherwise threaten to overflow.