Need input on American wheat ... tonight....

[jamilz]

A couple of points that seem to be incorrect.

The stirplate does draw in air. It does have other effects, but this is the one you really want. This is the right amount of O2 for a starter, not continuous pure O2, not a shot of O2 at the start.

There have been studies on the effect of stirring on yeast health. It is not a problem. Don't worry about it. For those interested, check the papers on the ASBC site.

[Kaiser]

The stirplate does draw in air. It does have other effects, but this is the one you really want. This is the right amount of O2 for a starter, not continuous pure O2, not a shot of O2 at the start.

I have read that overoxygenation with pure O2 may lead to faster aging of the yeast.

I have also read about brewers who use a stir plate and aerate with an aquarium pump and see even better yeast growth by doing so. This seems logical for me since the O2 intake through a vortex will be less than the having constant or pulsing aeration.

Kai

[rich]

Ok, boys let's take this outside. I've started a new topic dedicated to stirplate facts or fiction.
http://thebrewingnetwork.com/phpBB2/viewtopic.php?p=12701#12701

[jamilz]

Interesting thing about air stones and O2. I remember reading a paper on fish farming or some such thing years ago. They had a bunch of stuff on O2 for raising trout. It turns out that the main value to air stones are in surface agitation. That replacing the stones with surface action does just as much if not more duty in disolving O2 in the liquid.

I was talking with Dave Logsdon of Wyeast today and the same topic came up. He mentioned that they found shaking the carboy was more effective in disolving O2 in the wort than a continuous air pump with a stone. Same deal. You need lots of surface area to get the O2 to disolve and the stirplate does wonders in continuously exposing fresh surface to the air.

[Speyedr]

I was talking with Dave Logsdon of Wyeast today and the same topic came up. He mentioned that they found shaking the carboy was more effective in disolving O2 in the wort than a continuous air pump with a stone.

EIther this study or one just like has been up on Brew Monkey for a while now...

http://www.brew-monkey.com/brewschool/oxygenation.php

[Kaiser]

[quote="SpeyedrEIther this study or one just like has been up on Brew Monkey for a while now...

http://www.brew-monkey.com/brewschool/oxygenation.php[/quote]

Any idea how the shaking was conducted?

I'd like to know how much wort and how much air. If you cotinuously splash the wort in fresh air, you should hit the same O2 level in the wort as you would get with an aeration stone, because the partial pressure of O2 is the same in both cases.

But I still recommend the aeration store with an aquarium pump and in-line filter over the splashing as you are less likely to pick up airborne contaminants.

Kai

[Speyedr]

Any idea how the shaking was conducted?

Since this was a homebrew sized study, I would ASS-U-ME that they did what I do and just put a stopper in the carboy and shake the shit out of it 'til it hurts.

I'd like to know how much wort and how much air.

It says a 5gal carboy, so probably 5gal of wort. The air would depend on the pump itself, but the point is the number of bubbles in contact with the wort and how effectively that dissolves in solution.

If you cotinuously splash the wort in fresh air, you should hit the same O2 level in the wort as you would get with an aeration stone, because the partial pressure of O2 is the same in both cases.

The study says only 40 seconds of splashing, not continuous. The stone was running much longer.

I am sure they would be happy to answer any questions you have if you e-mail Wyeast. They have always been very receptive to such questions.

Finally, I use a siphon splasher thingy and then shake the crap out of the carboy, so I have no doubt that I am hitting 8ppm. However, Zymurgest (TTYL AND ILBCNU!) pointed out a cool device at http://wortwizard.com/default.htm
I picked one up and plan to try it soon, if I can get to brew before my Wife delivers our first next week.

Bottom line is to do what works for you, but know that you need to try to hit the minimum if possible.

Rob

[jamilz]

That study quoted on brew-monkey.com is from Wyeast.

The interesting thing about O2 from a cylinder is that the higher O2 level is probably because it fills the headspace with O2. As the bubbles agitate the surface, you're picking up a considerable amount of O2 from there.

So, as someone suggested, pure O2 with shaking will get you lots of O2 very quickly.