Is aeration necessary?

Since aeration is important for yeast growth, is it really necessary to aerate if I pitch a "proper" amount of yeast?

My first thought is no. However, professional brewers aerate their wort...?

Yukmay said:

Since aeration is important for yeast growth, is it really necessary to aerate if I pitch a "proper" amount of yeast?

My first thought is no. However, professional brewers aerate their wort...?

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Having healthy yeast going in is only part of the equation. Adding dissolved oxygen gives enough oxygen to allow a very short period of time for aerobic respiration to allow rapid reproduction of good healthy yeast. After which the anaerobic fermentation commences and produces ethanol.

At least this is my understanding of it. Anaerobic fermentation is quite stressful on yeast compared to aerobic.

Aeration is indeed important if you want quality beer. Origination is even better. If you don't care about the flavors weak or improperly grown yeasts put off, and you're not running high gravity beer that requires healthy yeast, then you might be ok not doing anything. Myself? I'm picking up an oxygen stone this weekend if my LHBS has a oxygen kit.

HexKrak said:

...Origination is even better...

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Guessing you mean oxygenation, that's quite a Freudian slip!

To the OP, the answer is obviously yes. The "appropriate" amount of yeast is that which is needed as a starting point; there is still yeast multiplication going on during the beginning of fermentation. So you need dissolved oxygen during reproduction to provide the yeast the ability to form sterols that help strengthen their cell walls so they can effectrively resist the toxic environment created by swimming around in their own waste (ethanol).

There is a new book out about yeast health by Jamil Z and Chris White, you could go much deeper than the regurgitation of info I have provided here if you are interested.

Thanks for the replies guys

So to clarify, aeration is important for the reproductive phase before the yeast begin to produce ethanol through anaerobic pathways. What would the repercussions be of pitching enough yeast so that yeast reproduction is not necessary? Would this eliminate ester formation among other things?

Is it possible that aeration is around to eliminate extra work/resources needed to breed enough healthy yeast for full fermentation without reproduction? If pitching this high amount of yeast makes a better beer though, it might be better to put in the elbow grease. If not, let me know!

Aeration is not, however, necessary at all for dry yeasts, though it won't do any harm.

Yukmay said:

So to clarify, aeration is important for the reproductive phase before the yeast begin to produce ethanol through anaerobic pathways. What would the repercussions be of pitching enough yeast so that yeast reproduction is not necessary? Would this eliminate ester formation among other things?

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Yes. Beer needs esters and other yeast-reproduction byproducts to taste like beer. Overpitching is as bad if not worse than underpitching, because at least with underpitching you have a chance for the yeast to get up to proper numbers in the wort and/or put off good fermentation byproducts anyway.

Pilgarlic said:

Aeration is not, however, necessary at all for dry yeasts, though it won't do any harm.

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Explain.

Textbook answer ............ yes, aeration is very important.

That being said, I have brewed several award winning pale ales and IPA's and I do not aerate. I just chill, siphon, and pitch. No shaking, air or o2 stone.

I think its one of those things in brewing that it's good to do but its not one of those brewing purchases that is going to make a night and day difference in your finished beers ...... **ducks and runs for cover**

Calder said:

Explain.

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Dry yeasts have been "preconditioned", so to speak. Unlike liquid yeasts, they don't need to build up the lipids and other compounds necessary for budding and production of cell walls. Liquid yeasts require oxygen to go through this phase, that is unnecessary for dry yeasts. Dry yeasts only "need" rehydration, though many (myself included) just sprinkle it on the wort. See the Lallemand site and check the spec sheet for Danstar Nottingham or Windsor. One or the other, or both make the statement that aeration is unnecessary, but it will do no harm. A starter with a dry yeast, on the other hand is, in the opinion of some, not only unnecessary but probably counterproductive.

i didnt aerate much when i first got started, recently i created a venturi tube to go between my bk and fermenting bucket so air is forced into the wort as it drains into my fermenter, thus aerating it. I gotta say the difference was very noticeable. fermentation began faster and it seemed to ferment better than before