Why I skim my fermenting beer

[bobtheUKbrewer2]

A head of foamy krausen will form on top of the beer. The foam consists of yeast and wort proteins and is a light creamy color, with islands of green-brown gunk that collect and tend to adhere to the sides of the fermentor. The gunk is composed of extraneous wort protein, hop resins, and dead yeast. These compounds are very bitter and if stirred back into the wort, would result in harsh aftertastes. Fortunately these compounds are relatively insoluble and are typically removed by adhering to the sides of the fermentor as the krausen subsides. Harsh aftertastes are rarely, if ever, a problem. credit John Palmer.

I sterilise a large spoon and skim it off 2 or 3 times a day wiping off the tide mark with paper tissues. Risk of infection must be low because in 43 years of brewing I have had only 3 batches smelling and tasting of stale vomit.

 

[KeninMN]

I just make and extra big yeast starter and decant a portion off into a sterilized 8 oz Mason jar...

 

[bobtheUKbrewer2]

how does your post address my post ? or am i thick

 

[KeninMN]

It's an even cleaner method of harvesting yeast and doesn't present an infection risk to a fermentation in progress.

That said, there are many ways to achieve the same outcome; just do what works best for you. No worries...

 

[70ls1nova]

I don' t think he's harvesting, he's throwing them away in an attempt to make his beer better. Correct me if I'm wrong?

 

[KeninMN]

My bad. Skimming is also a way to harvest clean yeast.

 

[bobtheUKbrewer2]

ah I get it, thanks.

 

[stpug]

I don't think the method of skimming the dirt layer is a necessary one and suspect that the difference in the final beer because of it is minimal at most. It would be interesting to do a comparison where a wort is innoculated and then split into two fermenters. One fermenter gets the treatment while the other does not, and then have it sampled by numerous people in an attempt to have them describe the differences between the beers (without knowing what or why they are difference, of course).

Overall, nothing wrong with skimming the dirt layer, I'm just not will to increase my risk percentage for that purpose; particularly the "multiple times a day" part. However, when I'm top cropping a beer I WILL skim the dirt layer in an effort to clean up the krausen and then later collect the yeast krausen.

 

[kh54s10]

I am glad it works for you. I leave it alone, leave the yeast that is in the foam there to continue their work.

I have only been brewing for 3 years and about 65 -70 brews. I have never noticed any off flavors that I would attribute to krausen crud. I have also not had any bad brews.

IMO that is all wasted (Edit: not wasted, but unnecessary work) effort.

 

[bobtheUKbrewer2]

thanks all - i brew brilliant beers - i think - but unwilling to leave krausen on for test purposes - note my failure rate is pretty low as i brew around 35 batches a year

 

[ArrrDubya]

Risk of infection must be low because in 43 years of brewing I have had only 3 batches smelling and tasting of stale vomit.

Bob,

Any idea what may have caused those very few infections you did get? Just out of curiosity, and IRT your last post, I'd be willing to back you up on your statement of brewing some really good beers by sampling...

 

[bobtheUKbrewer2]

I had them plated and looked at by a microbiologist friend, they were common airborne bacteria

 

[bobtheUKbrewer2]

Just out of curiosity, and IRT your last post, I'd be willing to back you up on your statement of brewing some really good beers by sampling...

I stated i brew v good beers but of course they might be better if i left the lid on and let some krausen sink into the beer - i dont know

 

[biertourist]

BobTheUkBrewer2 (you forget the password to your original account?),

I'm fully with you on this one.
The German brewing tradition is pretty obsessed with the QUALITY-of-bitterness derived from hops; they call this dark gunk "Braun hefe" (brown yeast) and they blame it for harsh, lingering bitterness (something that they really want to avoid). The "Braun Hefe" also includes non-isomerized hop alpha acids, which wasn't in Palmer's description.

-The non-isomerized alpha acids aren't soluble so they're quickly carried up to the krausen.

Who knows maybe this desire to avoid harsh lingering bitterness is also why german beers have really moved towards using isomerized hop alpha extract for bittering vs. actual hops -- as hoppy beers age the alpha acid content decreases, but the beta acids oxidize and these oxidized beta acids are more intensely and harshly bitter... (Maybe it's also why German prefer noble hops with high alpha to beta acid ratios?)


Adam

 

[wilserbrewer]

I've skimmed the Kreusen a few times, and never noticed a big difference.

Years ago at the carlsberg brewery in Denmark, I do recall a brewery worker skimming the Kreusen with what looked like a swimming pool pole skimmer from a fermenter that looked like a built in swimming pool.

30 years brewing and zero batches have smelled like vomit.


Wilserbrewer
Http://biabbags.webs.com/

 

[Rev2010]

I have only been brewing for 3 years and about 65 -70 brews. I have never noticed any off flavors that I would attribute to krausen crud. I have also not had any bad brews.

Me too. Been brewing for only coming up to 4 years but have done around 70 beers, never skimmed the krausen and never had a problem. I also don't bottle until a week after the krausen has completely fallen back into the beer and the top is clear. So typically I bottle after three weeks, two with my hefeweizen's. I think most of what is on top drops down to the bottom and is left in the fermenter when I bottle. As long as you don't stir it back into suspension I can't see it being an issue.


Rev.

 

[Rev2010]

The German brewing tradition is pretty obsessed with the QUALITY-of-bitterness derived from hops;

Hmm, everything I recall reading about skimming from actual German brewers themselves said they do it to capture yeast for reuse in the next batches.


Rev.

 

[Culbetron]

I think it sounds like a good idea if you are looking to do something beer-related multiple times per day but if it doesn't make a difference in taste doesn't it just seem like a huge waste of time?

 

[ncbrewer]

IIRC in the 90's it was fairly common to use a 5 gallon carboy for the primary and let kraeusen blow off to accomplish the same thing.

bobtheUKbrewer2: Thanks for posting this. I'm not ready to go this way yet, but it's always interesting to get input about alternate techniques.

 

[biertourist]

Hmm, everything I recall reading about skimming from actual German brewers themselves said they do it to capture yeast for reuse in the next batches.


Rev.

They're very obsessed with "lingering / harsh bitterness" from discussions of hop varieties to this subject ("braun hefe").

A great article by Ashton Lewis (BYO's Mr. Lewis), attributing Braun Hefe to harsh bitterness: https://byo.com/stories/item/697-glass-colors-blow-off-method-mr-wizard

Kai (the Beer Kaiser) tested the traditional practice and theory here: http://braukaiser.com/blog/blog/2010/02/14/should-the-kraeusen-fall-back-into-the-beer/

Zymurgy performed a very similar test and largely came to the same conclusion as Kai (that skimming the "braun hefe") can result in a less harsh bitterness. https://www.homebrewersassociation.org/forum/index.php?topic=486.msg8106#msg8106 (Vol 27 No. 6 November/December 2004
The Iowa Beer Tinkerers)



Adam