Aerating, or adding oxygen, to your wort is perhaps the easiest way to improve the quality of your homebrewed beer. Proper aeration before the start of fermentation ensures that your yeast is both healthy and happy.
Ways To Aerate Your WortSo, while your beer may end up alcoholic without aerating your wort, (it will be - unless you have other problems altogether) it will not be as attenuated as it would have been with proper O2, and will almost certainly take longer to ferment than it would have with appropriate levels of oxygen. To increase attenuation rates for better beer, we can aerate the beer in a variety of ways such as with a paddle, an aquarium pump, or a pure oxygenation kit.
Brewers should only attempt to dissolve oxygen into their wort after it has been cooled to below 80°F. Methods for dissolving oxygen can vary. Simple methods such as agitating the wort and dumping cooled wort from (sanitized) vessel to (sanitized) vessel - i.e. boil kettle and fermenting bucket - are the most common. A step up from that is using a device that connects to a common household drill such as the Mix-Stir, or the Grainfather Whirlpool and Aeration Paddle.
Aquarium pumps can also help with aeration. When using an aquarium pump, it’s important to remember that oxygen makes up only a small portion of the earth’s atmosphere, and that is what the aquarium pump will be putting into the wort - meaning that the pump should be run for longer (perhaps as long as an hour or more).
When using pure O2 gas, such as our Oxygenation Kit ample levels of O2 gas can be achieved in as little as 5 minutes (assuming that a carb stone is used to increase the efficiency of dissolving the gas into solution) for a 5-gallon batch. 8 to 10 parts per million is a good level for dissolved oxygen in solution. You can measure your oxygen levels with our oxygenation upgrade kit.
Why Is Oxygen Necessary For Fermentation?Aerobic respiration is the first phase of active fermentation and occurs after the lag time associated with pitching yeast into a new environment. During this time, the yeast scavenges available oxygen and ferments sugars - but the byproducts of this fermentation do not include alcohol yet. The yeast needs oxygen for sterol synthesis. The sterols keep the yeast cell walls pliable which ensures cell growth and health.
This phase of fermentation, which typically can be finished in as little as several hours, will produce many new yeast cells and significantly aid the yeast in its ability to continue to ferment the remaining sugars and produce our well-beloved byproduct of fermentation, alcohol.
Over-Oxygenating WortIt is possible for the brewer to dissolve so much oxygen into his/her wort that oxygen levels are actually too high. These levels could be toxic to yeast or cause oxidation and/or flavor instability in the finished beer. Neva Parker at White Labs stated while this is a possibility, it is highly unlikely that the average homebrewer would be able to achieve this feat of beer ruination.
Moral of the story: 'Give your yeast what it needs, and it will give you what you need (or want)' Even simple and unsophisticated methods of dissolving oxygen into wort can yield an improved product along with shorter fermentation times and more attenuated beer.