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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Reclaiming Pacman Yeast - Stir Plate or No Stir Plate?
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Old 10-09-2013, 05:40 PM   #1
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Default Reclaiming Pacman Yeast - Stir Plate or No Stir Plate?

So I made a 250 ml starter of 1.040 wort, and added the dregs from 4 rogue bombers (two were chocolate stout, 2 were Santa's helper ale or whatever). Now I'm wondering: should I let it sit and ferment on its own, or should I throw it on a stir plate? Seems like a completely sanitary environment would be beneficial since I'm using tired, old, and weak dregs (they won't have to compete with other organisms), but then it seems like a stir plate would really help get them going and replicate faster (although it does obviously expose them to competing organisms).

Thoughts? I searched and found people suggesting both ways for the first step in this process.

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Old 10-09-2013, 08:10 PM   #2
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but then it seems like a stir plate would really help get them going and replicate faster (although it does obviously expose them to competing organisms).
How does it expose them to competing organisms?
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Old 10-09-2013, 08:28 PM   #3
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Originally Posted by Zabuza View Post
So I made a 250 ml starter of 1.040 wort, and added the dregs from 4 rogue bombers (two were chocolate stout, 2 were Santa's helper ale or whatever). Now I'm wondering: should I let it sit and ferment on its own, or should I throw it on a stir plate? Seems like a completely sanitary environment would be beneficial since I'm using tired, old, and weak dregs (they won't have to compete with other organisms), but then it seems like a stir plate would really help get them going and replicate faster (although it does obviously expose them to competing organisms).

Thoughts? I searched and found people suggesting both ways for the first step in this process.
I've done it both ways. Stir plate is faster, other than that it doesn't matter.
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Old 10-10-2013, 12:26 AM   #4
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How does it expose them to competing organisms?
Stir plate starters are left open to the air, with no airlock, that the agitated wort can pick up oxygen from the air. They also, however, pick up whatever else is in the air...that's why it's commonly recommended that you decant off the majority of the liquid and use (primarily) the slurry at bottom.

Thanks for the replies, you guys. I'm still worried that microorganism exposure with such a small amount of pitched yeast could be problematic, but I guess I'm overly concerned.
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Old 10-10-2013, 12:35 AM   #5
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I wouldn't worry about it. Just sanitize your flask, and your stir bar and you should be fine. Put a piece of sanitized foil loosely on top of the flask. I'd say there's more of a chance of contamination from collecting the dregs than from your stir plate.

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Old 10-10-2013, 12:36 AM   #6
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Stir plate starters are left open to the air, with no airlock, that the agitated wort can pick up oxygen from the air. They also, however, pick up whatever else is in the air...that's why it's commonly recommended that you decant off the majority of the liquid and use (primarily) the slurry at bottom.

Thanks for the replies, you guys. I'm still worried that microorganism exposure with such a small amount of pitched yeast could be problematic, but I guess I'm overly concerned.
If you're not covering your starter container with a piece of foil or something, YDIW! I have never seen any container on a stir plate that's completely open.
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Old 10-10-2013, 12:41 AM   #7
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Quote:
Originally Posted by Zabuza View Post

Stir plate starters are left open to the air, with no airlock, that the agitated wort can pick up oxygen from the air. They also, however, pick up whatever else is in the air...that's why it's commonly recommended that you decant off the majority of the liquid and use (primarily) the slurry at bottom.

Thanks for the replies, you guys. I'm still worried that microorganism exposure with such a small amount of pitched yeast could be problematic, but I guess I'm overly concerned.
Your starters should always be covered, stir plate or not. And open starter is a recipe for an infected batch for sure. It is commonly recommended to crash and decant your starter so you don't pour weak, flavorless starter wort into your good beer, not to pour off other microbes.
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Old 10-10-2013, 01:05 AM   #8
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Whoa, guys, I get it. Typically, though, people advocate not tightening the foil completely (otherwise it would just be pushed off by the pressure and no air could get in to oxygenate the wort). So, you either cover it loosely or poke holes in the top. I mean, there're even foam plugs for sale on various sites for starters to allow air exchange AND co2 blowoff. Either technique prevents there being a seal and exposes the starter to airborne microbes - there's no way around that. Typically, what causes us not to worry about it is the large amount of co2 being released, the relatively large pitching rates for starters (the yeast crowds out other organisms), and the short amount of time starters are active for.

All three of those things are absent in this scenario, and thus the cause for concern.

EDIT: I see that I wasn't clear when I said "open." All I meant is that a perfect seal is not used, and thus the starter is 'open' to the air (in a loose sense). I know some sort of cover is necessary, but the ones used do not achieve a true cover like an airlock - a one-way seal.

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Old 10-10-2013, 01:24 AM   #9
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Foam plug or foil lid, either works like a charm. Oxygen can eventually permeate a plastic carboy, so making it around some foil is no problem, no holes needed.

Most sources of contamination result from the handling, not the air, anyway. There is plenty of oxygen in the headspace, the stirring just promotes better gas exchange.

Stepping up bottle dregs is common and done successfully by many. Like Denny said, stirplate is fast, other than that it doesn't matter.

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Old 10-10-2013, 03:53 AM   #10
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Wort becomes infected by dust-borne bacteria, not from the "air". The reason plugs work is because they prevent dust from falling in your starter. Stop the dust, prevent infections. Look up Pasteur's sterilized broth experiment.

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