How much oxygen do I need to put into my wort?
I've heard that homebrewers need to aerate with an oxygen stone and either aquarium pumps or oxygen. Is this true, or is shaking my carboy enough to get proper oxygenation?
So it turns out:
The proper amount of oxygen dissolved in wort is 8-10 ppm.
Shaking typically yields around 4 ppm. It's possible to achieve as much as 8 ppm with plenty of headspace and LOTS of vigorous shaking. As an example, 5 minutes of shaking a 1.077 wort may only achieve 2.7 ppm. Siphon sprayers will be in the same range.
Air with an Oxygen Stone can also only reach 8 ppm, regardless of the amount of time the stone is in the wort.
Oxygen with an Oxygen Stone Using a .5-micron stone and a flow rate of 1 L O2 / min, you need around 60 seconds to get 9 ppm, as shown:
30 seconds pure O2 5.12 ppm
60 seconds pure O2 9.20 ppm
120 seconds pure O2 14.08 ppm
When oxygenating a higher-gravity wort, you need higher oxygen levels - roughly proportionate to the amount of yeast. However, it's usually recommended to reoxygenate after the yeast have time for a cell division, This will result in a cleaner-flavored beer. Obviously, if you want your beer to have more off-flavors (specifically acetaldehyde and diacetyl), then a second dose of oxygen is counter productive.
Looks like I need to make a trip to the pet store...
EDIT: Keep in mind these values are also temperature dependent. The cooler the wort is, the better your ppm aeration will be in the end.
To quote from http://www.wyeastlab.com/hb_oxygenation.cfm:
It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone."
| Method | DO ppm | Time |
|---------------------------|----------|---------------|
| Siphon Spray | 4 ppm | 0 sec. |
| Splashing & Shaking | 8 ppm | 40 sec. |
| Aquarium Pump w/ stone | 8 ppm | 5 min |
| Pure Oxygen w/ stone | 0-26ppm | 60 sec (12ppm)|
I pour my wort into a bottling bucket and then letting it freefall from the spigot into the fermenting bucket about 2 feet below it. It's easy and it works well for me. I put aeration on the "art" side of brewing as opposed to the "science" side b/c I have no idea how to calculate O2 parts per million in my beer...
Also, I watched my buddy "shake" his wort to aerate it and dropped the bucket, the lid broke, and his garage was covered with 5 gallons of "floor beer."
We use a spaghetti strainer to aerate by lifting and splashing just as our wort chiller brings the temperature below 80. Hot liquids don't hold as much oxygen, so we wait until the end of the chill. Jim F
