Yeast Propagator

I finally took some pictures of the yeast propagator I built a while back and posted them along with descriptions here: Yeast Propagator

The intend was to enhance the yeast propagation on the stir plate by being able to aerate the starter beer during yeast propagation when the Kraeusen would get in the way of aeration though the vortex of the stirred starter.

2 thoughts on “Yeast Propagator

  1. In your opinion, is this better than simply covering the flask with foil? Using either a foil cap or a foam plug, I have always assumed that the stir plate continually introduced sufficient O2 by its own stirring action. However, I suppose that it’s possible that as the beer produces CO2, the partial pressure of O2 in the atmosphere (i.e. passive diffusion) looses out to the “push” of the generating CO2. Since you’ve certainly already weighed the merits of two-way air flow in your starters, could you speak at any more length on this particular point? Thank you.

    • David,

      Sorry for the late reply. I must have missed the notification e-mail.

      I’m wondering about this myself. I know that the stirring action will saturate the wort with oxygen. But the big question is, will there still be oxygen uptake once the Kraeusen forms. O2 uptake would only be able on top of the foam and the O2 infused beer in that region of the foam would need to trickle back into the starter. Looking at how static that foam looks, I don’t think that there is a lot of beer circulation between the foam and the starter.


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