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Stir Plate - How Long to Let Run?

We probably all know oxygen is OK at certain points and BAD at other points in brewing. What about a stir plate? How long is a good/safe time to let the stir plate run without introducing unwanted oxygen? I ask as, basically, a starter is a smaller volume brew.
It is common run a starter on a stir plate for 24 to 72 hours. How long it too long depends several factors such as amount of yeast, starter volume, size of the flask (I assume a flask but vessel too) and the vortex rate. Also, is it covered, open, sealed, air injected? Generally, 48 hours on a typical starter is enough for the yeast. Keep in mind the amount of oxygen is low on open air versus pure O2 which is why a stir-plate helps quickly propagate the yeast.

Oxygen is bad for fermentation once yeast go anerobic and kick in the fermentation process. Some high ABV beers could have small additions of oxygen in the first 36 or so hours while the yeast are still growing in population and getting strong, healthy cell walls. Beersmith talks a little about oxygen here Beersmith Oxygen

I could not find a perfect reference (Braukaiser is a good place to read up though). White Labs suggest 24-48 hours White Labs. This is about propagation, not too much oxygen though.

Thus, a good, safe time is 24-48 hours to propagate the yeast.
 
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I just took a 3 liter starter off the stir plate. 24 hours. Measured SG and it was definitely finished; no more sugar. And this was some old yeast I had in my fridge, so it took some time getting started. Normally I'd say it doesn't take 24 hours.

The yeast will go on feeding on the ethanol is you don't take it off, and that's probably not good. I don't know how bad it is, but I don't think it's optimal, at least. Jeff Caudill (of Imperial Yeast) told me to definitely not let the starter run once the sugars are consumed.
 
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It is common run a starter on a stir plate for 24 to 72 hours. How long it too long depends several factors such as amount of yeast, starter volume, size of the flask (I assume a flask but vessel too) and the vortex rate. Also, is it covered, open, sealed, air injected? Generally, 48 hours on a typical starter is enough for the yeast. Keep in mind the amount of oxygen is low on open air versus pure O2 which is why a stir-plate helps quickly propagate the yeast.

Oxygen is bad for fermentation once yeast go anerobic and kick in the fermentation process. Some high ABV beers could have small additions of oxygen in the first 36 or so hours while the yeast are still growing in population and getting strong, healthy cell walls. Beersmith talks a little about oxygen here Beersmith Oxygen

I could not find a perfect reference (Braukaiser is a good place to read up though). White Labs suggest 24-48 hours White Labs. This is about propagation, not too much oxygen though.

Thus, a good, safe time is 24-48 hours to propagate the yeast.
As you say, vortex rate is a factor. I've got both a rather forceful stirrer and a small Intellab stirrer. I only use the latter when the big one is in use, and I need to make some more/other yeast. The small one is useless for anything more than 2 liters, and it takes longer to propagate yeast on it. I use it seldom, so I have no real idea about the difference, but it is very noticeable.

Oxygen in beer and in a starter are two rather different subjects. If fed oxygen, the yeast will use it to respire, which is a much more efficicent way of utilizing the energy stored in the sugar tha fermentation. It won't stop fermenting, but it will do both. We don't want it to do that when we're brewing beer, because it doesn't produce alcohol from the sugar when respiring, and it tends to produce unwanted flavors, too. (That's one reason why starter beer isn't very nice:).) But we definitely want it in a starter, because the more efficient way of utilizing the energy from the sugars allows it to multiply more. It also won't run out of sterols and fatty acids. We get more yeast that way.
 
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It is common run a starter on a stir plate for 24 to 72 hours. How long it too long depends several factors such as amount of yeast, starter volume, size of the flask (I assume a flask but vessel too) and the vortex rate. Also, is it covered, open, sealed, air injected? Generally, 48 hours on a typical starter is enough for the yeast. Keep in mind the amount of oxygen is low on open air versus pure O2 which is why a stir-plate helps quickly propagate the yeast.

Oxygen is bad for fermentation once yeast go anerobic and kick in the fermentation process. Some high ABV beers could have small additions of oxygen in the first 36 or so hours while the yeast are still growing in population and getting strong, healthy cell walls. Beersmith talks a little about oxygen here Beersmith Oxygen

I could not find a perfect reference (Braukaiser is a good place to read up though). White Labs suggest 24-48 hours White Labs. This is about propagation, not too much oxygen though.

Thus, a good, safe time is 24-48 hours to propagate the yeast.
Thank you! Most helpful.
 
I just took a 3 liter starter off the stir plate. 24 hours. Measured SG and it was definitely finished; no more sugar. And this was some old yeast I had in my fridge, so it took some time getting started. Normally I'd say it doesn't take 24 hours.

The yeast will go on feeding on the ethanol is you don't take it off, and that's probably not good. I don't know how bad it is, but I don't think it's optimal, at least. Jeff Caudill (of Imperial Yeast) told me to definitely not let the starter run once the sugars are consumed.
Most interesting
 
As you say, vortex rate is a factor. I've got both a rather forceful stirrer and a small Intellab stirrer. I only use the latter when the big one is in use, and I need to make some more/other yeast. The small one is useless for anything more than 2 liters, and it takes longer to propagate yeast on it. I use it seldom, so I have no real idea about the difference, but it is very noticeable.

Oxygen in beer and in a starter are two rather different subjects. If fed oxygen, the yeast will use it to respire, which is a much more efficicent way of utilizing the energy stored in the sugar tha fermentation. It won't stop fermenting, but it will do both. We don't want it to do that when we're brewing beer, because it doesn't produce alcohol from the sugar when respiring, and it tends to produce unwanted flavors, too. (That's one reason why starter beer isn't very nice:).) But we definitely want it in a starter, because the more efficient way of utilizing the energy from the sugars allows it to multiply more. It also won't run out of sterols and fatty acids. We get more yeast that way.
Great info.
 
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