In beermaking it is critical that you limit the beer’s exposure to oxygen. Oxygen can react with compounds in the beer to degrade the overall quality of the brew but perhaps most noticeably it can create undesirable flavors. However, exposing wort to oxygen is a whole different story. In fact, prior to pitching the yeast, you’ll actually want to make sure that there’s a certain amount of oxygen in the wort. Having oxygen in the wort will make for healthier yeast, better attenuation and an overall more complete fermentation.
It is important to note that you’ll only want to introduce oxygen to wort that has been properly cooled. Bringing oxygen into the mix with wort that is hot or warm will inhibit bacterial growth ultimately increasing the likelihood of infecting your beer. You should always make sure that you are cooling the wort to pitching temperature immediately after the boil is complete and before aeration.
There are a number of ways to introduce oxygen to wort but they all fall under two main approaches: aeration and oxygenation. Aeration is the process of adding air to the mix while oxygenation is the process of infusing pure oxygen.
The difference here is that air is only about 20% oxygen. Because of the difference in composition, using pure oxygen will be the quicker approach though aeration can get the job done just as effectively.
Aeration is the more common approach because air is obviously readily available at all times while pure oxygen must be purchased and contained within a proper gas cylinder. So if you choose to aerate, the simplest way to do so is to agitate the container it’s in.
After your wort has been cooled simply shake the container with the lid on for five minutes. If the lid has a hole for an airlock or blow-off system, make sure that it’s securely sealed. This is the most primitive method and certainly requires the most manual work and can also be a little bit riskier when it comes to ensuring that you have the proper amount of oxygen present. For smaller batch brewing, this can be an effective route to take.
An inexpensive way to step your aeration efforts up a bit is by way of a siphon spray wort aerator attachment. This is a very basic piece of equipment that attaches to the end of siphon tubing. As you transfer the wort from the kettle to the fermenter, the design of the attachment causes the wort to spray, which promotes further wort aeration. It’s an affordable piece of equipment that you may want to consider adding to your homebrewing arsenal. Employing this method in conjunction with agitation can improve overall results.
For those looking to kick things up even further, a powered wort aeration system can be far more effective than the two previous methods mentioned. This system uses an aquarium pump to infuse sanitary oxygen into the wort.
The pump and air line are attached to an inline filter which leads to a diffusion stone. The diffusion stone has tiny pores that allow the pump to push out air into the wort in the form of very small bubbles. These tiny bubbles rise through the wort, releasing oxygen within the liquid at a very high absorption rate.
Since this method requires that you submerge the diffusion stone into the wort, you’ll want to ensure that it’s properly sanitized prior to use.
The other approach is oxygenation. This method is similar to aeration by use of the aquarium pump except instead of using a pump to force air into the wort you’re using a pressurized gas cylinder filled with pure oxygen.
Driving pure oxygen into your wort can be very effective but you have to be careful not to over-oxygenate—especially with beers that do not have a particularly high specific gravity. Oxygenation is actually ideal for higher gravity beers with an original gravity greater than 1.065 because they have a higher sugar content making it more difficult for oxygen to dissolve into the wort. Diffusing pure oxygen into the wort is more effective than using air that is only one-fifth oxygen allowing you to complete the process more quickly.
The amount of oxygen necessary in the wort can vary by beer type, yeast and specific gravity, among other factors. In general, you’ll want about 8-12 ppm but no less than 8 ppm. Though, unless you have an oxygen sensor on hand, you won’t be able to properly measure the oxygen levels in the wort so there are good general guidelines for proper aeration or oxygenation that can vary by method. When you are agitating wort by hand you’ll want to do so for 5-10 minutes. When you are using a pump-driven aeration system, you’ll want to let the system run continuously for upwards of 20-30 minutes. If you’re using a pressurized pure oxygen system, you can get the job done in as little as one minute.
No matter which approach and method you choose, properly introducing oxygen to your wort will undoubtedly make for healthier yeast. Paired with a yeast starter, the quality of your beer can improve dramatically. If you’re not currently aerating or oxygenating your wort then there’s no better time to start. Soon you’ll be asking yourself why you deprived your wort of oxygen in the first place.