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Aeration by dumping

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Mitchpaul

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I am relatively new to AG brewing (5 batches) and have noted emphasis on aerating prior to pitching yeast. I was looking for opinions of what i have done over past few AG brews for aeration. Once i have drained my cooled 25 litre wort from boil kettle to fermenter i then tip it back and forth between another sterilised bucket 2 or 3 times to introduce oxygen. Does this sound like a good idea or could it have risks? (other than spillage and back injury) For my last brew i didnt do this dumping i just drained straight to fermenter and pitched my yeast . To me the fermentation seemed a little slow and i had to increase temp to bring it to life, and the final gravity after nearly a week was still about 1015, more than expected. Any thoughts??!!
 

Tex N Oz

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Hi Mitch,
Oxygen is a medium of propagation. It's sole purpose is to make more yeast cells. it's a huge misconception that yeast eat sugar and poop alcohol. That's not the case at all. The reality is yeast breathe oxygen just like you and I. However, they have a unique ability to breathe sugar as well and in this process they "exhale" alcohol. Alcohol is mostly expressed when yeast are stressed from lack of oxygen.
Oxygenating wort provides an environment wherein the yeast can reproduce in an environment and the new cells are more adapted to that environment making them more efficient workers. However, most alcohol production occurs once the infused oxygen is consumed.
If your starter was large enough (enough yeast cells) and they were well adapted to the wort, they would manage to produce a fine product.
Hopefully this helps.... I've had a bottle of wine and I'm tired.

Edit: to answer your question, ambient air is fine as it's 21% oxygen. You only risk introducing infection. Pure oxygen infusion is best because it requires less volume to be infused and it's more sanitary. It's my opinion that oxygenation isn't so important if you have a very adequate starter that was started in the wort very similar to what you are fermenting. But that will be highly debated.
 

tugger

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I have also read some articles about the Japanese using sterile air over pure oxygen.
Mostly saying that a good healthy pitch didn't need super high o2 concentration, to prevent un needed oxidisation.
 

Mitchpaul

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Thankyou Tex. I must admit your descriprion of how yeast behaves and works is an angle i hadnt really taken much notice of. I may tone down my "sloshing" to reduce un necessary risk of contamination and concentrate on getting my yeast starter right?
 

kaiserben

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The article and the table showing how much O2 you can get into your wort using all the various methods on this page is a great reference.

It shows that the most O2 you can get into your wort by splashing or using an aquarium pump is 8ppm. The article mentions that 10ppm is suitable for most situations (you'll likely need more for a lager or high gravity beer. I think I've read 14ppm or so? I can't recall exactly).

IMO the important message to take out of all the various info out there is that you can have successful ferments with lower than ideal O2 levels; You might have countless ferments without any issues, it's just that with a less than ideal amount of O2 your chances of experiencing a ferment problem increases. Couple that with a higher gravity wort and/or a lower than ideal pitch of yeast cells and your chances of problems increase further.

EDIT: And just to confirm that 8ppm is the most that you could get by the method described by OP.
 

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