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Stir Plate - How Long to Let Run?

KB

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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.
 

GigaFemto

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I don't think it matters. There is no such thing as unwanted oxygen in a starter, assuming you pitch it before it goes stale. Most people oxygenate their wort just before or just after pitching the starter, so it is not bad to have a little oxygen in the starter liquid. If you make a starter and then store it for a long time the oxygen could cause staling reactions and generate off flavors. Don't do that. If you are going to store it for awhile, refrigerate it and pour off the liquid after the yeast settle out.

--GF
 

BOB357

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Aerobic fermentation encourages propagation. That's why you use a stir plate for starters. Once the starter has finished fermenting, there's no longer a need for O2 until you pitch it into wort.
 

KB

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Well... that's my question. What if I am not physically present with the starter has finished fermenting, analyzing, hovering over/around the beaker? Is there a "rule of thumb", "standard time" to let the stir plate run? I’d believe there comes a point where are introducing oxygen at a BAD time.
 

BOB357

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24 to 36 hours is pretty normal for starters. An extra day or so won't hurt a thing.
 

Finn Berger

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I think it definitely matters not to let it run after the yeast has consumed the sugars. Palmer, in How to Brew (p.122), tells us to take the starter off the stirer when it's halfway through, because the yeast needs to have the rest of the time to build energy stores (glycogen and trehalose). The implication there is that continued supply of oxygen hampers that.

I've mailed him about this, and didn't get a real answer. All he said was that he reckoned that at 12 hours after starting the starter would be about the right time to take the starter off the stirer. I can find no source to support the claim that you need to take it off - which of course does not mean it doesn't exist:). But I'd love to see it. (I assume that his source might be Chris White, as they're well aquainted, and White is on the list in Acknowledgements.)

Anyway, having yeast that has built good energy stores is vital. The yeast needs the glycogen for fueling the building of sterols and fatty acids, which are materials for the membranes. It does this using the oxygen we supply at the start of a brew, and the store of membrane materials is again vital for the yeasts capacity to multiply. The store will not be renewed through the brewing process (unless we supply more oxygen, which is what we do when brewing very strong beer), and if the synthesizing of membrane materials does not give the yeast maximum stores, it will not be able to produce enough new cells. The likely result is that we will have problems like incomplete fermentation and off flavors due to weak yeast not being able to "tidy up" waste products.

The trehalose stores are also important, as the yeast use trehalose when it is exposed to stress - and it is very likely to be exposed to stress.

I'm sceptical about the need for taking the yeast off the starter before all the sugars are used up. I mailed Jeff Caudill of Imperial yeast about this, and he said he saw no need for it, but that letting the starter spin after the sugars where consumed, would be harmful. So that's what I'm trying to live by theses days.

Now it's rather hard to decide when that crucial moment has come. There are lots of signs you can look for, but you can never be really sure unless you pour a sample and take a reading. So that's what I do. And I don't aim to wait as long as possible. I think it's better to get a little less yeast in order to secure maximum quality, so I tend to take the starter off a little earlier than I need to.

How much harm is done if the starter should be spinning an hour or two too long I do not know. Maybe it's not very critical? Or maybe it is? But as long as I don't know ... well, better safe than sorry.

I'm not a biologist or a chemist - I'm actually a retired history/litterature/philosphy teacher:) - so reading scientific papers in the field is a little beyond me. I'm trying to piece together an understanding based on scraps and pieces of knowledge that i pick up, and I'd be extremely happy if anyone with some real (and I mean really real!) knowledge could tell me what happens when the yeast is fed oxygen after it has eaten all the sugar. I know that it respires, and will use the oxygen to feed off the etanol, and if what Caudill said is right - and he ought to know these things - that process does not give us good yeast. But I'd really like to know why.

Timing a starter is hard. You can't say how many hours it will take, because there are many factors influencing it. And so I sometimes miss.But if I do, and the yeast has been spinning too long, I do of course not discard the yeast. But I assume it has got somewhat depleted stores, so I then give it a vitality starter at the start of the brewday. That seems to work fine.
 

BOB357

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I think there's some confusion about yeast starters. There are starters that promote cell count and starters that promote vitality. Vitality starters are generally either shaken vigorously or spun on a stir plate and pitched while active. I don't have How to Brew handy but think Palmer was referring to a starter aimed at vitality or a happy medium between the 2 types.

I've left starters spinning on my stir plate for 3 days a couple of times and saw no ill effects.
 

Kevin58

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The only problem with using a stir plate is shear force that will damage yeast cell walls. Look up the Shaken Not Stirred method of making a yeast starter as developed by Mark Van Ditta aka Saccharomyces aka S. Cerevisiae.





And here is an article I wrote in my brief attempt at blogging... https://mgbeer.blogspot.com/2019/06/shaken-not-stirred.html
 

Finn Berger

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I think there's some confusion about yeast starters. There are starters that promote cell count and starters that promote vitality. Vitality starters are generally either shaken vigorously or spun on a stir plate and pitched while active. I don't have How to Brew handy but think Palmer was referring to a starter aimed at vitality or a happy medium between the 2 types.

I've left starters spinning on my stir plate for 3 days a couple of times and saw no ill effects.
Nope, he's taking about promoting cell growth there. And he is definitely stating that giving oxygen all the way is bad for the yeast. Considering how widespread the use of stirplates is it is strange that he says so little about it in that book. After all he has allowed himself almost 600 pages:). (I do love that book, and Palmer sure is a great guy, but I don't necessarily regard him as God. I don't think he'd like me to do that, either:).)

I definitely think I've seen ill effects of letting the starter go spinning. And I think that may be why some have found that techniques like Conn and Beechum's Shaken Not Stirred actually works better than stirplate starters. (I think the theory it's based on is flawed, but it still seems to work, so I won't say it's bull. It's definitely great as a vitality starter:).)
 

BOB357

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Guess I've just been lucky in getting good results for ~15 years doing everything wrong. I'd definitely try the SNS method (actually developed by Mark Van Ditta), but I understand it doesn't work well with dry yeasts, which don't do well in starters. Guess that's another bad practice that's produced good results for me and many others.

Do what works for you and I'll do what works for me. There's more than one way to skin a cat!
 
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Finn Berger

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Guess I've just been lucky in getting good results for ~15 years doing everything wrong. I'd definitely try the SNS method (actually developed by Mark Van Ditta), but I understand it doesn't work well with dry yeasts, which don't do well in starters. Guess that's another bad practice that's produced good results for me and many others.

Do what works for you and I'll do what works for me. There's more than one way to skin a cat!
I've no problem with that. But what kind of advice do you think we should give people?

Modern dry yeast doesn't need oxygen. Fermentis advices against oxygenating the wort when using their products. But you might still do an SNS - or perhaps rather a NSNS (Neither Shaken Nor STirred:)) if you want to pitch active yeast, which I don't think is a bad idea. I actually mostly do that.
The only problem with using a stir plate is shear force that will damage yeast cell walls. Look up the Shaken Not Stirred method of making a yeast starter as developed by Mark Van Ditta aka Saccharomyces aka S. Cerevisiae.





And here is an article I wrote in my brief attempt at blogging... https://mgbeer.blogspot.com/2019/06/shaken-not-stirred.html
I asked a biologist about that, and he said that shearing thing was bull. Sorry.

Troester found that stirrer speed was conducive to growth. Spin faster, get more growth. If the stirrer hurt the cell walls. that wouldn't be the case, I think.
 
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BOB357

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"Modern dry yeast doesn't need oxygen. Fermentis advices against oxygenating the wort when using their products. But you might still do an SNS - or perhaps rather a NSNS (Neither Shaken Nor STirred:))"
Come on Finn. This self-contradicting statement from someone who asks what kind of advice we should give people.

If it strays from basics, I consider what has consistently worked well for me. I certainly wouldn't pass on excerpts from opinions I've read.
 

Finn Berger

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"Modern dry yeast doesn't need oxygen. Fermentis advices against oxygenating the wort when using their products. But you might still do an SNS - or perhaps rather a NSNS (Neither Shaken Nor STirred:))"
Come on Finn. This self-contradicting statement from someone who asks what kind of advice we should give people.

If it strays from basics, I consider what has consistently worked well for me. I certainly wouldn't pass on excerpts from opinions I've read.
Where's the self-contradiction? What I meant was that if you want to use dry yeast - say you love Verdant, for instance - and you also want to start your batch with active yeast, which is much of what SNS is about, then you can have the best of both worlds by sprinkling the dry yeast over that quart of starter wort and just drop the shaking. The starter will get started, and then you throw it into your wort when it and you are ready.

What is "basics"? It changes all the time. If you compare the first edition of Palmer's How to Brew with the last, a lot has changed. And I'm pretty sure that a new edition today, five years after his last, would also be different from the previous.

What mars many forum discussions is people insisting on the validity of anecdotal evidence, i.e. "This has worked for me, so that's how it is". I am totally sceptical about what people claim based on their own experiences - and that definitely includes my own. That doesn't mean I think people should not talk about their experiences, but they should not present them as evidence. And while one person's experiences aren't necessarily very interesting, the sum of what many people experience can certainly be.

You can do a lot of strange things while brewing and still get a decent beer - or beer, at least:). And many details matter a lot less than we may sometimes think. Marshall Schott and his gang of brülosophers have certainly showed us that. I've come from being rather sceptical about those xbeeriments to being quite enthusiastic. What I have learned from them is to be a bit more relaxed about many things which really are not very important.

But some details are important, and one of them is pitching healthy yeast, I think. I'm not much hung up on cell count. You need to be in the ball park, but that ball park is probably fairly big. But I am hung up on yeast health. So I'm very interested in what scientists and people working professionally with yeast has to say about it. And when discussing yeast health I will refer to what they have to say. That is not "
passing on excerpts from opinions I've read", it is attempting to present - to my best ability - what people who have seriously studied the topic have found out.

And that is what I think we should base discussions on.
 

BOB357

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Accepted procedures may evolve with time but basics remain the same.

You're entitled to your opinion, but I don't fix things unless they're broken. If my way works well, that constitutes evidence and means it has just as much value as your way. Both have a place in the discussion. I've read most all of the opinions you cite and don't need any of them explained further.
Have you ever considered a career as an evangelist? :):):)
 

Finn Berger

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Accepted procedures may evolve with time but basics remain the same.

You're entitled to your opinion, but I don't fix things unless they're broken. If my way works well, that constitutes evidence and means it has just as much value as your way. Both have a place in the discussion. I've read most all of the opinions you cite and don't need any of them explained further.
Have you ever considered a career as an evangelist? :):):)
This is meaningless. It ends here.
 

KB

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OK. Please realize my OP wasn't asking about dry yeast(s). I'm asking about stepping up liquid yeast and reaching a point where too much oxygen is bad (if this is a cause for concern).
 
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