Yeast Propagator

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Work in progress.jpg

It is well known that yeast propagation is best done with plenty of oxygen for the yeast. While this doesn't cause the yeast to start aerobic metobolization of sugars, the sugar concentration in worts brewers are using for yeast propagation inhibits aerobic metabolism, it is still beneficial for the yeast since it can create and store more sterols for healthy cell walls. In brewing fermentations sterol reserves are divided between mother and daughter cell when a daughter cell buds. This can lead to less than optimal sterol levels in yeast after the growth phase when adequate reserves are needed for sufficiently strong cell walls to withstand the increasing alcohol concentration.

During the early phase of yeast propagation on a stir plate, the starter beer will be saturated with air O2 at a level of about 8 ppm. This is a result of the vortex that is formed and the constant mixing of the beer with air from the head space. As yeast growth progresses and CO2 develops, the O2 concentration in the head space gradually declines and a Kraeusen forms, which also inhibits the contact between air and the beer.

Inspired by the design of the Carlsberg Flask[1][2][3], a yeast propagator that can be completely sterilized before the yeast is added and which also allows for aeration before and during the propagation, I wanted to build something similar. These were the requirements:

  • heat sanitation of the vessel and the wort
  • keeping the yeast in suspension
  • aeration during yeast propagation


Yeast propagator 1.jpg
Yeast propagator 2.jpg
Yeast propagator 3.jpg
Yeast propagator 4.jpg


References

  1. CPE Systems, Carlsberg Flask
  2. CPE Systems, Carlsberg Flask
  3. Alfa Laval, [http://www.alfalaval.com/solution-finder/products/scandi-brew-carlsberg%20flask/pages/scandi-brew-carlsberg-flask.aspx SCANDI BREW® Carlsberg flask