When is aeration OK and when not ?

Is aeration while sparging OK or will it have detrimental effects ? (Hot wort aeration)

What about just prior to pitching the yeast ? I assume that is OK, but is it possible to contaminate the wort with bacteria or mold doing this and if so, how does one prevent it ?

What about after pitching the yeast ? For how long is it OK to aerate ?

While not aeration, is it ever advantageous to stir a fermenting brew ?

How bad is aeration when racking ? Is a little air OK or should the goal be absolutely none ? I've noticed that otherwise stable beers will start fermenting after racking. Is that due to aeration and is that a good or bad thing ?

Generally I am paranoid about aeration and oxidation. I am wondering if am over doing it.

Thanks.

you are worrying too much.

As long as you know about it and try not to do it then it's fine,
The only time you should aerate is to help the yeast get going. If air touches your beer then you don't need to worry. Once the yeast gets going the brew will be strong enough to fight of airborne baddies and stuff. plus when in a container the co2 it creates will purge the air from a container.

Now if you bottle into dirty bottles or go splashing the brew all over the place then that is a different matter.

A good brew is strong forgiving stuff.

I agree with Orfy You know about it becareful and keep it to a minimum, but there is debate over this.
Its always possible to contaminate the brew when it cools down. Dont just sanitize, but clean and sanitize. I guess I would'nt stand under the AC vent in the house while racking if the AC or heater is on? Try the powdered brew wash, it works great to clean, then sanitize. I keep vodka in a spray bottle to help. Although I clean and sanitize my stoppers and airlocks I hit em with the vodka spray sometimes but thats probably overkill.
Some aerate before, some aerate before and after, I would'nt start to aerate unless your brew is at or below your max temp for yeast, a cooler wort will hold more air I dont aerate unless I have a high gravity brew
I would'nt stirr a fermenting brew
Sometimes the stable beers bubble a little when racking because the saturated CO2 is coming out or its not done fermenting yet
Are you overdoing it? How does your beer taste?
Are you all grain brewing?

Aeration is not only bad b/c of the risk of contamination from airborne baddies. When you aerate your beer, you run the risk of oxidation, which may/will have two potential effects on your beer. First, badly oxidized beer tasted stale or like cardboard. If the beer is very oxidized, this can begin happening immediately. Oxidized beer also has a shorter shelf life. So, stay away from aeration to make your beer "keep" longer.

As for when it is ok and not. Think about it in terms of hot side vs. cold side. Hot side aeration = bad, post boil, cold side/pre ferment aeration = good. In other words, do not aerate your wort as you sparge, do not aerate your hot wort after the boil, but you should aerate your wort after it is cool and before fermentation begins. Never aerate your beer after fermentation (at bottling, etc.).

brewman ! said:

Is aeration while sparging OK or will it have detrimental effects ? (Hot wort aeration)

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Not recommended...it can lead to oxidized/wet-cardboardy flavors. But don't worry about some slight occidental aeration. It's not the end of the world.

What about just prior to pitching the yeast ? I assume that is OK, but is it possible to contaminate the wort with bacteria or mold doing this and if so, how does one prevent it ?

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Depends wholly on your aeration techniques. Personally, I use an aeration kit from Austin Homebrew Supply. It pumps air through an inline HEPA filter, then through an aeration stone that sits in the wort. I always aerate...always. Ever since I started using this device, my attenuation levels have increased by about 10%. Highly recommended. Just aerate it once it's cooled down and in the primary vessel, but before pitching your yeast.

What about after pitching the yeast ? For how long is it OK to aerate ?

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It's okay to continue aeration after pitching, but I'd refrain from it once fermentation is visible. As for how long...again, this depends on your methods. With an aeration kit like I have, they say 20-60 minutes for a 5-gallon batch.

While not aeration, is it ever advantageous to stir a fermenting brew ?

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No, you risk oxidation of the final product, especially if it's later in the fermentation process.

How bad is aeration when racking ? Is a little air OK or should the goal be absolutely none ? I've noticed that otherwise stable beers will start fermenting after racking. Is that due to aeration and is that a good or bad thing ?

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Once primary fermentation is finished, you want to minimize aeration at all times. That having been said, don't worry too much about it. Also, restarted fermentation has little to do with the small amount of aeration, and more to do with the fact that you've "roused" the dormant yeast.

Generally I am paranoid about aeration and oxidation. I am wondering if am over doing it.

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You are worrying too much, yes. Just relax. Don't worry. Have a homebrew. Aeration is important, and I highly recommend getting a kit to do it, but it's not necessary. I've done 20 batches, and none of them have become oxidized...and I've never really been too concerned about aeration. I just try to minimize it, but I don't worry alot, either way.

More simply, the only time you aerate is the cooled wort in the fermenter. Before pitching or after pitching, doesn't matter much.

Introducing oxygen at any other time will damage the brew.

Thanks guys.

Are you overdoing it? How does your beer taste?
Are you all grain brewing?

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I haven't brewed for 5 years. The last beers I brewed were pretty good, but they were slightly harsh. Just a tiny bit. I thought I was maybe oxidizing the beer a bit. I don't have particulars at this time, but now that I am starting up again I want to watch that part of my process.

Yes, I am brewing all grain. I like lighter lagers.

The other thing I might be doing is over sparging my grains ?

oversparging can extract surplus tannins, which may account for the "harsh" qualities you talk about. Tannins are by definition harsh. Oxidation wouldn't make a beer harsh, it would just make it taste like wet cardboard.

Evan! said:

oversparging can extract surplus tannins, which may account for the "harsh" qualities you talk about. Tannins are by definition harsh. Oxidation wouldn't make a beer harsh, it would just make it taste like wet cardboard.

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Tannin extraction (for the homebrewer) is less about oversparging. We are not going to pull tannins out of our grain by oversparging . . . unless we are pressing grain bags like tea bags or something.

Now, a wort that is too acidic will create tannins. You should worry more about the ph of your wort rather than oversparging if you are worried about tannins. Get some ph test papers and test your strike and sparge water and your wort during mash and during sparge, etc. See what you have in terms of ph. I think that you want it as near 5.0 as possible. There is even a product you can buy to ensure that your mash ph is right.

david_42 said:

More simply, the only time you aerate is the cooled wort in the fermenter. Before pitching or after pitching, doesn't matter much.

Introducing oxygen at any other time will damage the brew.

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Is there a precise temperature range in which you want to aerate? Like 80-100ºF or so?

at pitching temp.