yeast oxygenatinng

[Fred Scheer]

HI All:

I want to start this thread to find out if other Brewers
aerate their yeast before pitching?
To what extent are you aerating?

Anybody any experience between keeping the yeast in anaerobic vs.
aerobic stage?

Lot's of Brewers in Germany aerate their yeast to about 10 ppm before pitching. This keeps the viability above 95% and the pH is < 4.5
even after re-pitching.

Cheers,

Fred

[South County]

This is an interesting topic I've read about. I'm curious as to how brewers are getting the air into the yeast? Is this done by pressure vs. surface area, sintered stone, inline venturi? Quick search suggest this is done with the yeast suspended in a small starter solution of grain derived simple sugars and then run through a venturi assembly. In first link below they talk about the advantages of aerating the yeast vs. the wort and how it produced better fermentations, flavors, and reduced staling precursors. Another question is can this be done effectively from cone to cone? Must it be done while pitching the yeast solution into tank before the main wort is added?
My thought is that aerated too early the yeast may deplete any available stable nutrient and turn back on itself?! Another words keeping the yeast in an aerobic stage could be more harm than good and much harder to manage?!

http://www.wipo.int/pctdb/en/wo.jsp?IA=US2001008235&DISPLAY=DESC

another article supporting such

http://www.aaccnet.org/meetings/2006/abstracts/o-42.htm

[wiredgourmet]

I can add this little abstract from a 2004 presentation: http://www.worldbrewingcongress.org/...ting/Orals.pdf Item O-76. I can't find the full text, but searching indicates that it's been quoted in a subsequent papers.

It seems a sound hypothesis, but I haven't heard of anyone actually doing it. I wonder if that means it requires specialised equipment. Or perhaps it's one of those things that works best on paper.

It's meant to "optimise" fermentation, I am told. Fair enough, but that's not the same as optimising quality in the final product. If anyone has used this method, I would love to hear about your results.

[dick murton]

We only aerate / oxygenate the wort, but as you say, I have heard lots of European brewers oxygenate the wort. The problem with oxygenating yeast too early in storage is that it depletes the nutrients and following subsequent storage the yeast is less effective. I know that Esau & Hueber oxygenate (or "revitalise" to use their phrase) yeast but mix it with wort to give it some nutrients and bring it up to the growth phase as the yeast is pitched into the main body of wort, so reducing the lag phase normally experienced. If I remember correctly from some of our pilot brewery trials, they found oxygen control more difficult when treating yeast than when treating wort, I think due to the danger of nutrient exhaustion. But I don't think they were adding wort for yeast food beforehand.

Key to good viability in our expereince is simply to crop good yeast and keep it cold, 3 or 4 degrees, with gentle agitation so you don't freeze yeast in contact with the coolant jackets or PHE

Cheers