Too much O2 in wort possible?

[Dland]

Just wondering if one can oxygenate too much. I have a new SS Brewtech O2 injector and kind of have to leave it on during wort transfer, or run up & down the stairs extra.

It takes about 10 minutes to cool wort and pump to fermentor, and the lowest setting on regulator that pushes though stone is .5L/min.

This adds up to considerably more o2 than what I used to add with regular wand/stone set up post transfer.

I'm not too worried, but I figure someone here would have definitive answer.

 

[NTexBrewer]

Can’t answer about too much O2 but is it possible to have a check valve on your oxygen line and only oxygenate half of the time?

 

[BigRedBrewer]

You can definitely have too much O2 in your wort. Typically too much O2 is going to increase yeast activity which will be similar to a high temp fermentation. You could potentially see an increase in byproducts like Acetaldehyde. Chris White and Jamil recommend 8-10 ppm in the yeast book. I usually get around 10 ppm at 30 seconds in an average OG wort on my Milwaukee O2 meter (with a wand/carb stone)

 

[ptmpls_uGU]

Would too much O2 explain why, since I started adding it to wort (45 seconds with stone/red tank from home depot), my yeast attenuation levels have gone from 70s to mid 80s?

 

[RPh_Guy]

Just wondering if one can oxygenate too much.

Yes. Over-oxygenation can potentially cause oxidative damage to the wort compounds and to the yeast. ... But the actual effects of this aren't well characterized, especially in homebrew where oxygen can rapidly reach equilibrium with air in the headspace given the relatively larger surface area.

Typically too much O2 is going to increase yeast activity which will be similar to a high temp fermentation. You could potentially see an increase in byproducts like Acetaldehyde.

I'm not sure that's a good comparison. The effects of temperature are very different than the effects of oxygen.

Increased wort aeration/oxygenation generally decreases the formation of acetaldehyde and promotes its breakdown (Kunze 2019 English p384).

https://onlinelibrary.wiley.com/doi/full/10.1002/jib.392

It's unclear whether oxidative stress on yeast actually play a role in homebrew beer, much less that it would increase fermentation byproducts.

Would too much O2 explain why, since I started adding it to wort (45 seconds with stone/red tank from home depot), my yeast attenuation levels have gone from 70s to mid 80s?

Oxygenation generally promotes yeast health and improves fermentation kinetics. What you are seeing is the effect of "adequate" oxygenation, not "too much".

 

[BigRedBrewer]

Increased wort aeration/oxygenation generally decreases the formation of acetaldehyde and promotes its breakdown (Kunze 2019 English

I know Kunze is a pretty reliable source of info, however according to the yeast book, page 78 at the bottom it states: "excessive usage of oxygen results in high levels of fusel alcohols, increased acetaldehyde and other flavor problems."

Aeration at the correct amount will help with yeast health which does help with the reduction of acetaldehyde during stationary phase. I think the issue with over aerating is, you increase yeast activity in the growth phase which results with a higher production of acetaldehyde and fusel alcohol.

Also on page 105 they provide a chart that says increasing aeration results in lower ester development and higher fusel alcohol production. Since fusel alcohol is most often associated with high fermentation temp, that's why I made the comparison.

 

[ptmpls]

Oxygenation generally promotes yeast health and improves fermentation kinetics. What you are seeing is the effect of "adequate" oxygenation, not "too much".

Adequate or too much? I am shooting for a FG around 1.012 range based on attenuation of strain, and the yeast keep working to the point it finishes 1.006.

 

[RPh_Guy]

Adequate or too much? I am shooting for a FG around 1.012 range based on attenuation of strain, and the yeast keep working to the point it finishes 1.006.

A healthy fermentation generally produces a beer tasting beer. The high attenuation is clearly the result of healthy fermentation, not unhealthy fermentation, unless you have a contamination.

FG is just a number and listed attenuation is just an estimate. If you want lower alcohol, you can use less malt, or you can adjust the mash parameters (temperature and/or time) to reduce fermentability.

I know Kunze is a pretty reliable source of info, however according to the yeast book, page 78 at the bottom it states: "excessive usage of oxygen results in high levels of fusel alcohols, increased acetaldehyde and other flavor problems."

Aeration at the correct amount will help with yeast health which does help with the reduction of acetaldehyde during stationary phase. I think the issue with over aerating is, you increase yeast activity in the growth phase which results with a higher production of acetaldehyde and fusel alcohol.

Also on page 105 they provide a chart that says increasing aeration results in lower ester development and higher fusel alcohol production. Since fusel alcohol is most often associated with high fermentation temp, that's why I made the comparison.

I don't know. I'd like to see some primary literature or some kind of experiment (that's not bungled by brulosophy).

Again, the vastly increased rate of diffusion for home brew means over-oxygenation is likely not significant a problem for us in my opinion, even if it is one at a commercial scale. But who knows?

 

[Ironedge]

I know Kunze is a pretty reliable source of info, however according to the yeast book, page 78 at the bottom it states: "excessive usage of oxygen results in high levels of fusel alcohols, increased acetaldehyde and other flavor problems."

Aeration at the correct amount will help with yeast health which does help with the reduction of acetaldehyde during stationary phase. I think the issue with over aerating is, you increase yeast activity in the growth phase which results with a higher production of acetaldehyde and fusel alcohol.

Also on page 105 they provide a chart that says increasing aeration results in lower ester development and higher fusel alcohol production. Since fusel alcohol is most often associated with high fermentation temp, that's why I made the comparison.

Really need to determine what excessive means. Unless you are using an dissolved O2 meter, it is just a guess. "Turn it on and count to..." is the normal recommendation for a hobbyist. The recommendation is .5 to 1 liter per minute once the correct temperature is reached during knockout. I use a plate chiller so that my wort is going into the fermenter at 65F and I set my flowmeter to just shy of 1 liter per minute, which should, in theory, give me 8-10 PPM. If I ever get a DO, I will test it.

Cheers