Oxygenating after pitching yeast

[dermotstratton]

Beer is kegged and carbed. Only difference I can notice is the beer is a little hazier than normal. Attenuation was right on. Flavors are as expected. I am not sure if adding O2 after pitching can impact haze, but it is the only thing I notice.

 

[C-Fizzle]

I'm not making this up. It's a documented scientific experiment that you can literally watch for yourself. You don't have to take my word for it (like some of the anedoctal evidence others are presenting).

The wyeast video seemed much more like a statement and not a repeated/verified scientific experiment. They don't even mention how full the carboy was. I'm just saying I wouldn't hang my hat on a video with a guy making a statement in blue scrubs.

On another note, I know this thread is old and you've probably brewed plenty of batches since, but there is no harm done in oxygenating after you pitch (except the risk of contamination) if you oxygenate during the lag phase (typically 12-24hrs assuming proper pitch rate). In fact, for really big beers (1.100+) you have to do a second oxygenation prior to fermentation commencing if you want full attenuation.

I won't go into depth on the technicalities but as long as a majority of the cells are in the reproduction phase, the oxygen in the wort is being absorbed (within about an hr) by the yeast to prepare their cell walls for division. Once a majority of the cells have moved into the fermentation phase (24hrs +) the addition of oxygen to wort will not be absorbed by the yeast, instead, it will react with a yeast reproduction by-product that has not yet been cleaned up and result in acetaldehyde (green apple), diacetyl, or fusel alcohols. (Yeast, Chrise White & Jamile Zainasheff)

 

[dermotstratton]

Once a majority of the cells have moved into the fermentation phase (24hrs +) the addition of oxygen to wort will not be absorbed by the yeast, instead, it will react with a yeast reproduction by-product that has not yet been cleaned up and result in acetaldehyde (green apple), diacetyl, or fusel alcohols. (Yeast, Chrise White & Jamile Zainasheff)

I'm confused. Is this saying that adding O2 after fermentation starts will result off flavors (acetaldehyde, diacetyl and fusel).

But you also state that sometimes in high OG beers, you need to add O2 late in the cycle. How is this not contributing to off flavors.

On side note, Jamil answered this question in Brew Strong Q and A show. He said it would be next to impossible to have conditions where straight O2 would be toxic to yeast, regardless of when it is added.

 

[C-Fizzle]

Adding O2 once a majority of the cells have started ferrmentation is bad for the beer. The second addition of O2 to high OG beers occurs before fermentation starts. Now knowing when fermentation starts is obviously an art not a science, but in general, it's fine to add oxygen before or after you pitch yeast as long as the majority of them are still in the reproduction phase (typically 0 - 24hrs).

 

[dermotstratton]

Gotcha. So if adding O2 to a big beer after pitching yeast, do it within 24 hours?

I suppose logic is that the huge pitch needed for big beer will eat up all the O2 in wort and could use more before fermentation really starts?

 

[ja09]

I seem to remember Dr Clayton Cone saying that the optimal time to oxygenate is around 14 hours after pitching the yeast, though I can't find his Q&A session on the homebrew digest. At any rate I always oxygenate after pitching the yeast (sometimes 12 hours later, sometimes immediately) and I've never had a problem.

Found it:

http://www.danstaryeast.com/articles/oxygenation-timing

Very interesting. I pitched 05 last night but ran out of oxygen, debating whether I was going to get another tank and try today.....