Meandering through Greg Noonan's New Brewing Lager Beer, I was struck by this:
"Kraeusen beer should be added [to the layering vessel] to produce the smoothest possible beer. Kraeusening generally reduces diacetyl, corrects poor primary-fermentation yeast performance, entrains CO2 in the beer, and gives fuller, mellower flavors. Seed yeast for starters and culturing should be collected from the primary-fermenter yeast cake."(pg 243)
I really want to try this. Anyone done this? Any pointers?
When I brew lagers I set aside a small jar of yeast from my starter and also a 2 liter soda bottle (sanitized) of chilled wort which goes into the freezer (the wort--not the yeast). When the beer is done fermenting I thaw the leftover wort and pitch the saved yeast and basically make a fresh mini starter. When it is at full kräusen I add it to a keg and transfer the beer on top of that. I let it naturally carbonate at that stage at cellar temps with a spunding valve and then chill and lager for at least a month. The kräusening aids attenuation, cleans up off flavors, can add a little sulfur, and turns "green" homebrew lager into proper lager.
Chris Colby has a nice overview:
Kräusening (Part 1 of 3)
You might also consider that the book was published in 1986. There was all sorts of stuff going on back then that seemed to work but now has been shown to either not be necessary or doesn't do anything or the con's outweigh the pro's.
If you have a issue that this procedure might resolve, then try it. But if you don't have the issue, then don't do this and think it's something that must be done every time. Diacetyl pretty much takes care of itself given time and proper temps in the FV.
Eric Toft, longtime head brewer at Schönramer (considered by many to be one of the best breweries in Germany) strongly endorses using kräusen to ferment lager beers.
Greatest Drinkability: The Bavarian Brewer's Art
“Only with kräusening can you get the proper aging, the desired maturation process,” he says. However, that means more gear in the brewhouse. “You’re looking at 50 percent more equipment for the same amount of beer.”
Here's a description from their website (edited Google translation):
Schönramer - Gär- und Lagerkeller
"After fermentation is complete, the young beer is pumped into the lager cellar and blended with 8 to 10% “Kräusenbier” on the way there. Kräusenbier is a name for the beer in the first 18 to 36 hours of fermentation. During this time the yeast is particularly vital and active and the beer is covered with a deep, foamy layer called “Kräusen”. By adding the Kräusen beer, the fully fermented beer undergoes a secondary or secondary fermentation in the storage tank. Since the tanks are closed, the resulting carbon dioxide can naturally dissolve and bind in the beer. Carbon dioxide gives the beer its effervescence, or liveliness. During storage, also known as maturation, the beer gradually clears and the taste develops. We store our beers, depending on the variety, for 4 to 10 weeks at temperatures of 3 to -1°C."
[Nach Abschluss der Gärung wird das Jungbier in den Lagerkeller gepumpt und auf dem Weg dorthin mit 8 bis 10% „Kräusenbier“ verschnitten. Kräusenbier ist eine Bezeichnung für das Bier in den ersten 18 bis 36 Stunden der Gärung. In dieser Zeit ist die Hefe besonders vital und aktiv und das Bier ist mit einer tiefen, schaumigen Schicht, die „Kräusen“ genannt wird, überzogen. Durch die Kräusenbiergabe erfährt das fertig vergorenene Bier eine Zweit- oder Nachgärung im Lagertank. Da die Tanks geschlossen sind, kann sich die dabei entstehende Kohlensäure im Bier auf natürliche Weise lösen und binden. Kohlensäure verleiht dem Bier seine Rezenz, oder Spritzigkeit. Im Laufe der Lagerung, auch Reifung genannt, klärt sich das Bier allmählich, und der Geschmack entwickelt sich weiter. Wir lagern unsere Biere, je nach Sorte, für 4 bis 10 Wochen bei Temperaturen von 3 bis zu – 1°C.]
Of course, they use decoction and open ferment all of their beers, so they are obviously unscientific traditionalists who don't know how to make proper modern lager.
My lagers have greatly improved since I started down this path. I say go for it.
