What is Krausen?

If you are new to making beer or homebrewing you may have heard the term Krausen used before and wondered what exactly it is?

So what is krausen? In this post, we will answer that question and show you how it can be used to determine if you have a healthy fermentation as well as indicating what stage of the fermentation your beer is at.

What is Krausen?

Krausen is defined as the yeasty foam that rises to the surface of fermenting wort.

In layman’s terms, it means as the yeast in your wort starts to go to work eating the sugars you will start to see a layer of foam begin to form on the surface of the wort. As the fermentation activity increases the size of the foam on top will typically continue to grow.

Krausen happens during what is referred to as active fermentation. Fermentation can take up to 10 – 14 days to complete, however, the Krausen is most present during the first 2-5 days.

Afterward, it will start to drop, some brewers refer to it as falling or crashing. Novice brewers make the mistake of thinking fermentation is over when it falls, this is not correct. It is important to either let your beer ferment for at least 10 days or take a hydrometer reading 2-3 days in a row to confirm fermentation has finished.

The Verb Krausen

The definition we just shared was the noun form of the word which is how most homebrewers and craft brewers use the word, however, you should be aware that there is a verb form of the word also, usually called Krausening.

Krausening is a technique first developed by the Germans, wherein they would remove the Krausen when it reached its highest point called high-krausen (see below) and introduce it to a fully fermented batch of the same beer.

There are 3 main reasons for doing this:

  • To naturally carbonate and condition
  • To restart fermentation
  • To clean up off-flavors

How to Pronounce Krausen 
A beer fermenting in a bucket with krausen present at the top. The title of the photo is What is Krausen.
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The word krausen is actually a German word and means curly. Which of course describes the action of the foam as it curls up the fermenter.

If you want to hear how it is pronounced you can head over to howtopronounce.com and have a listen.

Some people pronounce it as “kroy-zen”. However, a more accurate pronunciation is “krow-zen”. The “ow” would sound just like it would when you stub your toe, now simply put the “kr” in front of it and “zen” at the end.

What is Krausen Made of?

As we discussed krausen forms as the fermentation process begins. The yeast begins eating the sugars which create both carbon dioxide and ethanol.

The foam you see forming is actually a mixture of bubbles created from carbon dioxide, yeast cells both dead and alive, proteins from the wort itself as well as hop particles.

Some novice brewers will wonder if they should mix the krausen back into the wort, this is not recommended as it can create off-flavors in your beer.

Is Krausen a Sign of Fermentation?

Yes, it is a sign of fermentation but it is not the only sign. Some beers will have a lot of krausen while others will not have any at all. Some beers will have a krausen that rises and lasts for a few days while with other beers it will rise and fall very quickly. So the existence or size of it should not be the determining factor as to whether fermentation is happening.

Seeing activity in your airlock is one of the primary methods to confirm fermentation is underway and taking a gravity reading with your hydrometer is the most accurate method to determine if it has started and when it has ended.

When is High Krausen?

There are 3 stages of fermentation, the first stage would be considered to be as soon as you pitch your yeast. Many people expect to see some activity start to happen right away. This is usually not the case. The yeast has to rehydrate, come to life, and start multiplying, usually, within 24 hours you will start to see some activity in your airlock.

The second stage is what is referred to as high krausen, it is where the majority of the fermentation happens and the krausen will reach its highest. This typically happens during the first 72 hours of fermentation.

The third stage is when the krausen starts to drop, many people think that fermentation is over at this time. That is not correct, fermentation can go on for another 7 – 10 days. You might not see a lot of activity but the yeast is still working away creating alcohol, carbon dioxide, and cleaning themselves up.

When Does Krausen Fall?

As we discussed, usually after 72 hours you will start to see it fall. This is as a result of the yeast starting to slow its activity down, it will begin to do what is referred to as flocculating, which means it starts to fall to the bottom of your fermenter, or drop out of suspension and become what is called trub.

Some beers take longer to flocculate so the krausen will stick around longer. And in other cases what looks like krausen on the top of the wort might just be leftover residue of it caked to the side of your fermenter.

How Much Krausen is Normal?

There is no exact answer to this question, every beer will be different depending on the amount of grains and fermentable sugars used, how well the grains were milled, what temperature you mashed at, how much and what type of yeast you pitched, what temperature you are fermenting at and what the original gravity was.

Remember krausen is not the only measure of whether a beer has had a good fermentation, airlock activity is a good indicator plus the only way to really be sure is taking the gravity readings.

Watch for the Blow Out

One thing to watch for is the dreaded blowout. This is when the krausen is so large and active that it actually spills out of your airlock and makes a big mess on the side of the fermenter and the floor.

This can happen if you put too much wort into the fermenter, typically for most beers of average strength if you leave 1 – 1.5 gallons of headspace between the top of the wort and the opening of the fermenter you should be ok. However, if you are brewing big beers you might need to use a blow-off tube instead of an airlock.

A blow-off tube is simply a length of plastic tubing that you connect to your airlock or mouth of the carboy. You put the other end into a bucket with sanitizer in it. Instead of the foam jamming up the airlock, it will blow off into the bucket.

Should I Remove Krausen?

This is really a matter of personal preference. Most people do not remove it as it is active yeast doing its job. Other people do remove it as they believe when it falls back down into the beer it creates a bitter taste.

There are two problems in our opinion with removing it:

The first is that it will remove yeast from the fermentation, which will result in the beer not fermenting fully.

The second is that in order to remove it you would have to open the fermenter which risks exposing the beer within to oxygen which can cause infections and off-flavors.

A tip to remove it without exposing the beer to oxygen is to use a smaller fermenter with the blog off tube we talked about and let it all blow off on its own.

Try it both ways and see how you prefer your beer. Brew the same beer twice, remove the krausen on one and leave it on the other. Whichever beer you prefer will be your answer as to what to do moving forward.

Is There Yeast in Krausen?

Yes, there are both live and dead yeast cells in krausen. This is why it is not recommended by us to remove it, if you do there is a chance you will not ferment the beer out properly and not reach your final gravity.

Lots of Krausen But No Airlock Activity

If krausen is present then fermentation is happening. If you are not seeing any activity in your airlock it is likely that you have a leak somewhere near the top of the fermenter.

If it is a plastic bucket-type fermenter you can try pushing down on the lid to make sure it is securely in place. If that does not stop the leak it might be the airlock or the bung it sits in and you may have to replace them.

The same goes for if you are brewing in a carboy. You can replace the bung or airlock now or wait to do so in your next batch. If it is a plastic fermenter and replacing the airlock or closing the lid tighter does not work it might be time to get a new fermenter.

Either way do not worry about it during this batch, the odds of oxygen getting past the lawyer of CO2 at the top of the wort is quite slim. Many brewers will ferment with an open to the air fermenter, with no lid. The Mr. Beer kits you buy have an opening in the lid also. Odds even with a small leak your beer is going to turn out fine.

Can You Rack Beer with Krausen High?

The short answer is that yes you can. But the better answer is why would you want to? If there is still krausen present, especially high krausen that indicates the beer is not done fermenting.

Although it is possible to go from grain to glass in 4-5 days (we’ve done it many times), it is not recommended unless you are in a pinch and need beer right away. It is recommended that you let your beer ferment for at least 10 days if not 14 days. This allows the yeast to not only finish fermenting but it allows it to condition for a while and clean itself up which makes for a better-tasting beer with fewer off-flavors.

If you are determined to rack it with krausen present, hopefully, you have a fermenter with a spigot on the bottom, if not you will want to use a sanitized instrument to poke down through the foam and create a hole so you can get your siphon hose through it to the beer underneath.

Final Word

As you have seen, krausen is a mixture of live and dead yeast, as well as CO2 and other proteins. It is a good indication of a healthy fermentation and can also indicate when the majority of the active fermentation has come to an end. Do not be in a rush, let the yeast and krausen do their thing, give it time to do its job properly and you will be rewarded with a much better quality and tasting beer.

Cheers, Big Robb is Out!

Big Robb with a pint of home brewed beer
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P.S. Be sure to check out the side of the blog or at the bottom if you are on a smart device. I am giving away the recipes to my top 5 best-selling beers from my brewpub. Enjoy!

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