5 Fixes If You Forgot To Aerate Wort

Its the biggest fear a homebrewer can experience. Fermentation, just is not starting, then you remember you forgot to aerate the wort!

Maybe its not as big a problem as you might think. Here are 5 things you can do if you forgot to aerate your wort.

  1. Do nothing.
  2. Shake the fermentation vessel.
  3. Pump oxygen into the wort.
  4. Start fermentation at a warmer temperature.
  5. Yeast choice alleviates wort aeration fears

Oxidation can ruin beer, but when you are undergoing an active fermentation oxygenated wort is very important to keeping your yeast healthy.

1. Do nothing

You make have nothing to fear at all. If you just sealed everything up and put it in storage, you might not need to do anything and fermentation could start up no problem.

In fact, most of the time there are no issues with fermentation at all. There is likely plenty of oxygen left in the wort to complete fermentation.

You may have unknowingly oxygenated the wort without even thinking about it by doing these things.

  • Exposing it to the air when cooling.
  • Pouring it into the fermenter.
  • Leaving some headspace in the fermenter.
  • Moving the fermentation vessel, shaking it as you walked.

If you did any of these things, which I’m sure you have then it is very likely that your wort has oxygen in it.

In fact, oxygen will naturally dissolve into the wort even if you don’t slosh it around. So your fermentation could start, but start much more slowly than it would otherwise.

2. Shake the Fermentation Vessel

If you forgot to aerate your wort and fermentation has not started, just pick up the carboy or bucket and give it a shake. You will dissolve the oxygen in the headspace into the wort speeding up fermentation.

This will increase your fermentation speed, if you were to otherwise do nothing so make sure you do this step if you forgot.

Urban Legends and Krausen

There is some fear of shaking after a bit of fermentation has started, but then slowed down in rapid succession.

The Krausen (foam on top of wort during fermentation) is thought to give bitter flavors to the beer and make it less desirable to drink.

I can assure you that during transit to the bottling bucket we have sloshed this Krausen around plenty of times and pushed it directly back into the beer with no ill effects.

So shake the fermentor to your hearts content!

Krausen is essentially just leftover yeast and if you give it a bit of time it will clean up any off flavors that were produced. So I should mention our experiments included bottling and not kegging.

Shaking other fermentations

If you have read this blog for a bit then you will notice we also talk about fermentation of mead and meadmaking.

When it comes to making mead you are required to shake up the fermentation vessel in order to degas it, or let some CO2 escape. This also increases the level of oxygen in the must, or the meadmakers name for wort.

So, I can assure you its perfectly safe to shake up your fermentation vessel during fermentation.

3. Pump Oxygen into the Wort

Depending on what kind of beer you are making you might want to pump oxygen into your wort manually. Higher gravity beers that are shooting for a high alcohol content will need more oxygen.

You will wan’t to keep your yeast as healthy as possible to hit those higher ABV levels. Especially if you are experimenting with weaker yeast strains, or even if you don’t have enough yeast.

It’s actually suggested that you drop in two yeast packets if you are planning on making a Belgian Tripel because you wan’t to push the upper limits of how much alcohol you can create from the wort.

Dangers of Pumping Oxygen into Wort

Since you likely already have a fair amount of oxygen in the wort you need to be careful when pumping oxygen into your wort.

For example, in the section where I said do nothing I offered multiple reasons why your fermentation will go just fine.

So if for any reason all of these things occurred and you have an excessive amount of oxygen, pumping more oxygen in could be detrimental.

In fact pumping oxygen into wort is a sure fire way to have to much oxygen dissolved into wort. The yeast might not even have enough sugar for all the oxygen and it will lead to beer oxidation.

So be careful when manually adding oxygen to wort, you can either play it by ear or there are even devices you can buy to measure the exact oxygen level of your wort.

But, those devices are expensive, so you are better off just letting things be.

4. Start Fermentation at a Warmer Temperature

There are two things that fermentation at warmer temperatures can achieve.

  1. Vigorous yeast growth and activity
  2. Faster dissolving of oxygen into wort.

There may be a decent amount of oxygen in the headspace of your fermentation vessel, if you did not shake it then it will slowly dissolve into the wort.

This will feed the yeast and lead to the growth of more yeast cells.

The temperature that you should ferment at will depend on the yeast. Since specific ranges will create different flavors in the beer.

For example, Kviek yeast is probably the most beginner friendly yeast since it can ferment at higher temperatures and still lead to a tasty brew.

5. Yeast choice alleviates wort aeration fears

The entire reason that we need oxygen in wort in the first place is to make sure yeast is healthy and can grow exponentially until the alcohol percentage begins to kill them off, or they run out of food.

There are two types of yeast that you can pitch into your wort. Dry yeast, and Liquid yeast.

Dry Yeast Oxygen and Pitch Rates

Dry yeast does not actually need oxygen in the wort at all. In fact it has all the nutrients it needs to pump out a delicious beer without even growing the number of cells pitched.

Because we are pitching so many healthy yeast cells already, oxygen in wort is not even essential, because we don’t need to grow new cells.

Of course there is also no fear of oxidation of the beer, since any oxygen left in the wort will be consumed to make more yeast cells and speed up the fermentation process.

Liquid Yeast Pitch Rates

Liquid yeast typically has lower pitch rates than dry yeast does. However, liquid yeast is already in an active state so it will be able to overcome any initial stresses.

This means that fermentation will start fast and vigorous. If it was getting to the point of slowing down it would likely snowball again since any oxygen in the headspace or in the wort itself will fuel more yeast growth.

Aeration in Wort No Worries for The Homebrewer

When it comes to aeration in wort, for the homebrewer its really not much of a worry. Sure if you were a commercial brewery it may be very important to increase your efficiency, but as a homebrewer rough estimates are just good enough.

Since we are not worried so much about pitching the exact amount of yeast to ferment our beer in a specific amount of time, or hitting the same abv every time then its not a big deal.

Wort Aeration for the Efficient Brewer

If you are trying to hit much higher ABV levels, and with weaker yeasts that can’t handle high alcohol tolerances, then getting as much out of the yeast as possible becomes important.

However, if your yeast dies at a certain ABV level and too much oxygen is left in the wort, then you will have a beer oxidize much more quickly.

Its better to have less oxygen in the wort and have the yeast run out of food (sugar) and die from alcohol tolerance. Since you will likely not need your yeast to grow beyond the initial pitch rates.

Since yeast propagation is a fairly simple process, its more important to keep beer from oxidizing than it is to speed up fermentation or create more yeast cells.


Hey, I'm the the creator of frugalhomebrew.com. I have been brewing beer since 2013 and started by brewing in my parents home. I have written copy on numerous websites. Most notably Seeking Alpha, where I analyze small cap publicly traded companies. I have also written content for netnethunter.com and brokenleginvesting.com.

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