Oxygen, how much is too much?

[bondra76]

Okay, I re-read it. On the flip side, YOU may want to read the article again.



Now look at the graph again . Ninety minutes to get to 68-75% oxygen saturation in water with the "aquarium pump" proxy (keeping in mind that the solubility of oxygen in standard gravity wort is 15-25% less than water makes it even worse)

Agree to disagree. The guy doesn't use ppm which is probably the best way to measure oxygen. He states that he only conducted the tests once, which make the results pretty questionable. And lastly they state they tried the air experiments with or without the aeration stone. One thing I will agree with you on though - anyone trying to pump air into wort without a stone is really off the mark. Punching holes into a tube like the experiment suggests is a horrible method for introducing air and definitely would take 90 mins. I hope no brewer is using that method. But the stone is definitely a viable option with use of a hepa filter.

 

[FarmerTed]

Agree to disagree. The guy doesn't use ppm which is probably the best way to measure oxygen. He states that he only conducted the tests once, which make the results pretty questionable. And lastly they state they tried the air experiments with or without the aeration stone. One thing I will agree with you on though - anyone trying to pump air into wort without a stone is really off the mark. Punching holes into a tube like the experiment suggests is a horrible method for introducing air and definitely would take 90 mins. I hope no brewer is using that method. But the stone is definitely a viable option with use of a hepa filter.

I think the basic assumption made in the article that aerating water and aerating wort is the same thing (with scaling for different oxygen solubilities) is flawed. Water and wort have very different properties. Water doesn't foam up the way that wort does, it is less viscous, and has a different surface tension (different density, too). My guess would be that it is easier to aerate wort to saturation just because of the foaming, and perhaps because of the greater viscosity relative to water. I'm not sure if the relative efficacies of the different techniques that they tested would be different, but then again, I have no real reason to believe that things would line up just they way that do when aerating water. And that is a very good point that they only did one test per technique.

 

[Iseneye]

This is a weird thread. The OP asked how much oxygen is too much and there were a few good replies and then it got derailed into non-pure 02 discussions.

If you don't use pure 02 that is fine - noone is making you. I also find it strange that people say "I only aerate by shaking and I make good beer" without comparing it to the same beer made with pure 02. I'm sure the beers are great but it doesn't mean that you wouldn't get better results with 02 (or vice versa).

I used to shake and now use 02. I can't quantify if the beers are better but lagers require more 02 than you can get via shaking.

 

[masaba]

To the OP. When you are getting the off-flavors, have you been using only one particular type of yeast? A few strains of yeast do in fact show poor performance in the presence of as little as 20 ppm of O2, a level that I am sure some people hit quite often with pure O2 setups. So, one option would be to try a few different strains of yeast and only use the ones where you don't experience the off flavors. Here's an article that shows the performance of yeast with different amounts of O2 for four different 'types' of yeast (See Figure 2).

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1980.tb06882.x/epdf

I also find it interesting that the need for oxygen in the wort is essentially eliminated if you propagate your yeast in an oxygen rich environment (see Table 2). This could explain why some people experience big differences in fermentation when switching to pure O2 and others don't really see any difference.

 

[ArcLight]

1. What most people don't realize when using Oxygen is that the bubbles that come up are not dissolving in your wort. After Oxygenating, seal up your fermentor and shake the crap out of it to better dissolve the O2 into the wort. Having a lot of O2 in the head space doesn't help that much. You need to rock and shake it to get the O2 dissolved.

2. I wouldn't worry so much about over oxygenating your wort unless you seriously over do it. 16 ppm wont be a problem. 35 ppm may be a problem. Chances are if you are using that much O2, a fair amount is bubbling out of the wort and not dissolving. Yeast will use Oxygen in preference to fermenting because respiration is far more efficient (i.e. makes better use of the available food for the yeast).

 

[BaldApe]

What I was doing is opening the valve close to all the way and running oxygen for 2 minutes. The headspace was filled with oxygen, so there was certainly the capacity to have way too much.
The yeast I had a problem with was the WLP001.
My plan is to aerate in the kettle after chilling, and only run the oxygen lightly for 30 seconds.

 

[Iseneye]

What I was doing is opening the valve close to all the way and running oxygen for 2 minutes. The headspace was filled with oxygen, so there was certainly the capacity to have way too much.
The yeast I had a problem with was the WLP001.
My plan is to aerate in the kettle after chilling, and only run the oxygen lightly for 30 seconds.

Without putting a quantity to it, that sounds like way too much for a standard ale. Try 30sec to 60 sec. There should be very little bubbling on top of the wort when you have the 02 on. I barely turn my canister valve on.

Also good advice about closing fermenter and giving a small shake.

 

[BrewSavage]

20-30 seconds vs. 5 minutes. I take the 5 minute route and now pay $0 per batch..just preference I guess

What does the "air" line mean in that chart above? Does is mean simply having your wort exposed the atmosphere?

So if I do nothing then after 5 minutes (300 sec) my wort will have 8 ppm of dissolved oxygen? Cooling my wort with my immersion chiller takes longer than 5 minutes.

 

[bondra76]

What does the "air" line mean in that chart above? Does is mean simply having your wort exposed the atmosphere?

So if I do nothing then after 5 minutes (300 sec) my wort will have 8 ppm of dissolved oxygen? Cooling my wort with my immersion chiller takes longer than 5 minutes.

Sorry I'd post the article if Zymurgy let me copy/paste their archives..

The air injection method used a 2 liter per minute aquarium pump (Tetra Whisper model #77853) through a 0.2 micron air filter and a stone. Complete setup costs $30.

The interesting thing about the Zymurgy test is that they pumped nitrogen into the samples, and then pumped O2 or air into the sample and measured PPM that way.

 

[BrewSavage]

Ok, thanks for clarifying.