Reclaiming Pacman Yeast - Stir Plate or No Stir Plate?

Zabuza said:

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).

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Zabuza said:

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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bja said:

How does it expose them to competing organisms?

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Zabuza said:

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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Zabuza said:

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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Ichthy said:

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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Zabuza said:

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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