Yeast Cake and oxygen

[Zack]

I'm going to try my first attempt at dumping my wort on top of a previous batch of beer I just racked...My question is, I normally induce oxygen to the wort before I add the yeast as I understand that introducing oxygen after pitching will kill the yeast. If thats correct, and I'm not adding any new yeast, is there any better solution to aerating then by the old stand by of shaking?
thanks,
Zack

 

[Evan!]

Adding oxygen after pitching does not kill the yeast. I don't know where you read that, but it's wrongo-dongo. Yeast need oxygen for metabolism, so why would it kill them?

You don't want to add any oxygen after, say, the first signs of visible fermentation (unless it's a really high-OG beer). While there's still no risk of "killing" the yeast with it, you do run the risk of ending up with excess oxygen in the beer after fermentation is done, because you've introduced it at a point where the yeast don't need it as much (which is in their growth phase)...and that excess oxygen concentration can lead to an oxidized (read: cardboardy or sherry-like) finished product.

 

[Revvy]

What he said!

 

[ohiobrewtus]

Why can't you just aerate in the boil kettle after you've cooled to pitching temps, then dump it in primary?

 

[Bobby_M]

The truth is, you really don't need to oxygenate when pitching on the cake. It won't hurt, but it's not necessary because the cell count is already through the roof. In any case, you can oxygenate after you transfer onto the yeast. No problem.

 

[Desert_Sky]

The truth is, you really don't need to oxygenate when pitching on the cake. It won't hurt, but it's not necessary because the cell count is already through the roof. In any case, you can oxygenate after you transfer onto the yeast. No problem.

Exactly. Just dump onto the yeast cake and stand back, its going to be one furious fermentation

 

[Zack]

Thanks for all the help. I don't know where I read about oxygen being deadly to yeast, but that's why I'm a member here. U guys are the best.
Thanks again.

 

[coyote]

The truth is, you really don't need to oxygenate when pitching on the cake. It won't hurt, but it's not necessary because the cell count is already through the roof. In any case, you can oxygenate after you transfer onto the yeast. No problem.

would this also apply to Belgian ale fermentations? I thought you wanted some yeast growth for certain flavors in those styles.

appreciate your insight.

 

[Zack]

I have one more question for ya...I'm into lagers, with that being said, after fermentation at 50f for 2 weeks, when I cold crash and subsequently lager in my primary at close to freezing as I can get it (2 to 6 weeks at 32F) would it be ok to dump the new wort on top of the yeast cake after after its been cold for that long of a time? or would it better to rack into a secondary and then lager and use the primary to continue the second batch assuming both yeast cake and new wort being the same temps (50f)?

I guess what I'm asking is, will the yeast survive 2 to 6 weeks at 32F, then warmed back up to 50F (my fermentation range) for a second batch?

Thanks,
Zack

 

[Bobby_M]

The thing is, on ANY beer that relies heavily on a yeast's character, you do NOT want to be pitching on full cakes. You can harvest the slurry and pitch a smaller amount in an oxygenated wort to retain yeast growth flavor profile. If you just want a super clean, fast ferment with something like US-05/WLP001, the more yeast the better.

On the lager thing. You really should be transfering to secondary before you do month of lagering. However, the yeast will still be viable once they're warmed back up again.