Rousing your carboy during fermentation? yes or no?

Quick question here. 2 parts.

I am wondering. Reading Papazian's book he talks about the krausen that develops on the primary fermentation. He talked further about removing the krausen and that there are elements within the krausen that will make the beer taste off or give hangovers.

I personally am using a 6.5 gal carboy. So if I fill it with 5.5 galons of wort I have some of that dead empty space at the top of the fermenter to accomodate this krausen.

Problem is I have no way to remove the krausen. Further I wonder to myself should I rouse my yeast when it starts to die out? Should I try and rouse the wort in the carboy to try and re initiate more fermentation?

If doing so it will consume my krausen back into the beer I assume, and I take it that isnt really a good thing.

What are others doing as far as these issues go?

Any advice is appreciated. Thanks

ST

Don't touch the krausen. That is the active yeast fermenting your beer, leave it alone and do not mess with it. It will drop back into the beer when the hard and active fermentation is done. Trying to remove it will only lead to contamination and then you will have to get rid of it all and not even worry about the off flavors as it trickles down the sink drain. Shaking or rousing the carboy is ok, it will just get more yeast from the bottom into suspension. You only really want to do this during your primary ferment and do not do it after a week or so, you want those yeast on the bottom by that time. There are elements in all beers that will cause off flavors and cause hangovers, they are part of the process and can't really be avoided. Your best bet to avoid off flavors is to ferment at the correct temperature for what you are trying to brew. If you drink enough of anything you will have a hangover, period. Just take it in moderation, and remember that the live yeast in your beer will add vitamin B to it and that will reduce the chance of a hangover as compared to a commercial beer. I think that stuff like thist is the reason a lot of better authors don't really care for Papazian's works that much.

I always let the krausen drop before doing anything. I don't take any hydrometer readings I don't swirl, nothing but let the yeast do what it does.

GaryA said:

I always let the krausen drop before doing anything. I don't take any hydrometer readings I don't swirl, nothing but let the yeast do what it does.

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Are you saying you do rouse after the krausen falls? Attempting to get 1 last shot at further fermentation?

I don't swirl or rouse at all, unless my beer seems unwilling to finish up. One thing I make sure to do is to carefully avoid all the crud on the side of the fermenter- the remants of the krausen. I've heard that stuff can impart a bitter taste, so I just leave it there. Otherwise, I just stick an airlock on the primary and walk away for about 2 weeks. I don't move or touch or mess with it at all. It seems to have worked for me so far!

Don't remove krausen, swirl or rouse your yeast at any point during the fermentation. Period. When fermentation is static for a period of time (usually around 3 days, checked by hydrometer and hydrometer only -- not airlock activity or "the recipe said 7 days primary") and you feel you have not acheived your desired attenuation, then you may ever so gently swirl the carboy to try to get yeast back into suspension. However, I have not read many, if any, reports of this working.

If you are not getting the desired attenuation from your yeast, you are most likely under pitching, under aerating/oxygenating, or both.

Like the others said, leave the krausen. If you use a bucket instead of a carboy, it is possible to skim off the krausen. I used to do this a long time ago, but never noticed any bad effects when I stopped it.

As for rousing after the krausen has fallen, it does help with highly flocculant yeasts such as WLP 002 and Wyeast 1968. I've never found it necessary with any other yeast (but there are plenty that I haven't tried).

-a.

As stated by others I only rouse the yeast back into suspension if I think it has not fermented enough. And this is after a couple (atleast) hydro readings to see what is going on in the primary.

Originally posted by BrewFrick
I think that stuff like thist is the reason a lot of better authors don't really care for Papazian's works that much.

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Hmmm, interesting comment. Never heard this before.

There can be benefits to skimmimg Krausen for certain styles such as American Pilsners or if you wish to top crop yeast from your fermenter. This is a practice that is perfomed by many large breweries.

Personally i ALWAYS ROUSE my beers during the first 3-4 days...especially high gravity ales and barley wines etc....

When the first vigorous fermentation starts...co2 is produced very quickly...the proteins in the wort will facilitate elasticity and integrity of the co2 bubble membranes which thus dont burst right away on reaching the surface.

As these bubbles rise they also interact with suspended and active yeast cells...carrying them up to the surface and eventually OUT of the wort where they are needed!..this is the yeasty bubble mass on the top of fermenting beers what we call the krausen...

By swirling your fermenter you will reintegrate these active yeast cells back into the wort where they are needed....of course most beers will probably have an adequate supply of yeast already in suspension fermenting away and under normal circumstances using low to mid gravity brews you probably wont notice much difference to the fermenting process...hence the reason many breweries and home brewers just leave it....

But when i ferment big beers like my anticipated 11-12% Imperial IPA am fermenting now, I always swirl my fermenter during the first 3-4 days...this gets the MAX number of yeast in suspension and speeds up the whole process and i definitely feel improves overall attenuation rates...
People always go on about pitching the correct amount of yeast as being important..which it is of course, but why leave so much useful yeast just sat on top of the krausen doing nothing.

Of course a lot depends on what yeast you are using and its potential krausen properties.

My advice before listening to conventional advice is to try a few experiments yourselves...Use two fermenters ..say 5 galls each and brew a high gravity ale..say 1.100+....swirl the first fermenter in the first 3-4 days of active fermentation say 5 times a day...and do nothing with the second....i can guarantee the first one will not only ferment in a shorter period of time, but will also risk less chance of getting stuck!

Or here is an even simpler test...using only ONE fermenter find the number of bubbles through the airlock over 1 min...then swirl the fermenter vigorously, after the initial co2 rush that is expelled through the airlock dies down after a minute or so....do the time test again.....you will almost certainly see an increased rate of fermentation...the extra yeast cells are back in suspension and doing their job once again....of course as the krausen builds back up you will have to swirl it back into suspension again, i swirl my fermenters 4-5 times a day.

i do this throughout the active vigorous fermentation period and i have never had a beer get stuck or take forever to ferment...i do tend to brew mainly big beers over 8-12% Abv

Anyway for those more interested on this subject I recommend this book as great reading...particularly pages 645-650

Malting and Brewing Science: Hopped Wort and Beer
By D. E. Briggs, James Shanks Hough

It's funny how many things "you aren't supposed to do" seem to work just fine.

You definitely don't need to skim krausen. However, it doesn't hurt anything and was a yeast harvesting technique for hundreds of years.

You rarely need to rouse yeast, but many breweries do just that injecting co2 from below.

5 gallons of beer in a bucket is a whole lot more forgiving than most people want to admit.

I actually read here.. that skimming the fresh Krausen and saving it in the frig is good.

Especially with a Big beer. As you can add it back to the secondary to make sure you have enough yeast come bottling day.

BTW.. that a good Idea ?

Interesting idea. Do you think fermcap would benefit the beer? It might save a lot of time, and keep more yeast in suspension on average.

I don't know I had heard this trick was good for Big Beers, that have a hard time carbonating after fermentation has worn out the yeast.

Taking fresh Krausen off since the yeast are sitting on top of the foam and not doing anything anyway.. Seems like a good idea.

Not sure if I should do it, and risk infection and oxidation by opening up my fermenter doing something unnecessary.

Right now I have a healthy Krausen, and its on a RIS... so the time is now if I were to do it.

during the first few days mixing and shaking is a good thing. However, after 72 hours, the carboys should remain undisturbed until bottling.

Related question: I've got a persistent krausen that just won't drop. It's been three weeks. I haven't wanted to take a hydrometer reading through the krausen for fear of messing with the yeast while it's doing its thang. That said, I've still got (slow) airlock activity, so between that and the krausen, I assume the yeast is still chewing on the wort. This is on a kolsch yeast fermenting at about 55, so... slow fermentation and a slow krausen drop is to be expected, right?