I just brewed a Kolsch using WLP029. According to the White Labs website the Optimum Fermentation Temperature for this yeast is 65.00-69.00. I also understand that Kolsch should be lagered. I am concerned that lagering with a strain will cause off flavors since the OFT is in the mid sixties and lagaring takes place if the 40’s - 50’s. In other words, what is the connection between the Optimum Fermentation Temperature and lagering temp? I hope this makes sense.
First kolsch is a ale brewed as a ale and that yeast is a ale yeast. You do not need to lager with the yeast. Lager the beer when you are finished fermenting. That’s what they mean by lager (cold condition)
As a follow up question, is there any value in cold conditioning an ale for an extended period of time? Will it harm anything?
Last year I was PM’ing a home brewer in Romania. He always cold conditioned his ales. Has since opened a micro brew attached/with a restaurateur and is doing very well on bar sales. Ultra fancy 750 ml bottles with neck tags rather than labels.
I’ve never tried cold conditioning though. My temps are almost always at 67° to 68°F. I would see no harm in cold conditioning unless you are impatient to taste.
In the case of ales, this process is referred to as Cold Conditioning, and is a popular practice at most brewpubs and microbreweries. Cold conditioning for a week clears the beer with or without the use of finings. Fining agents, such as isinglass (fish bladders), Polyclar (plastic dust), and gelatin, are added to the fermentor to help speed the flocculation process and promote the settling of haze forming proteins and tannins. While much of the emphasis on using finings is to combat aesthetic chill haze, the real benefit of dropping those compounds is to improve the taste and stability of the beer.When the beer is conditioned at low temperatures various processes take place that lead to the smooth character which is expected from a lager. Proteins and polyphenols (tannins) bind with each other to form larger molecules which become insoluble and precipitate out of solution. Hop polyphenols will drop out leading to milder hop bitterness. Some of the alcohols and acids form esters in the beer which leads to new flavor compounds. This process is very slow and becomes only significant after more than 12 weeks. Some yeast activity may be present which leads to further clean-up that removes the yeasty smell and taste associated with young beer. Also, it is not uncommon to see extract reduction of the beer where an extract drop of 0.1 – 0.2 Plato over the course of a few weeks can occur.
damian has eloquently stated the process, so all I can add is a personal observation:
So far I’ve only done 1 kolsch, but altbiers are my thing using WY1007 and I generally do 2-4 each year. I generally cold condition them for 3-4 weeks after fermentation is finished, and usually include a day or two of cold crashing and gelatin as well. The one time I didn’t bother with the 3-4 week cold conditioning, there was a noticeable difference. The quicker batch was not nearly as smooth or tasty.
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Jim, you mention cold conditioning and cold crashing. How do you define these two in terms of both temperature and time?
Must… resist… soapbox…
Ok, I’ll keep it to a minimum and on task. Traditionally, Germans do not categorize their beers as “ale”. That’s something specific to English/Belgian/French/Western brewing culture. Kölsh and Alt are considered Obergäriges Lagerbier, which means “top fermenting lager beer.” Top fermenting, or sacch. cerevisiae (what we usually mean when we say ale yeast), is the yeast species that WLP029 is, and you’re correct that it should be fermented at warmer temperatures. And as previously mentioned, go ahead and bring it as close to freezing after fermentation completes and hold it there for as long as you can stand it. I’ve gone for 8 weeks at about 30F and not had an issue with bottle conditioning. Be advised, though, that the krausen from WLP029 REALLY likes to hang around the top of the fermenter, and it might take much longer than usual for the yeast to drop.
You can thank the Reinheitsgebot from Köln for this particular quirk of history, as their version of the “purity” law prevented them from using bottom-fermenting yeast.
And go ahead and call your beer a lager if you want! 
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I for one welcome the history lessons. It makes it weird though… whenever I go to NB and start weighing out grain bills and picking up yeast, they invariably ask what I’m making. I pause, try to remember all the historical background and pronunciations, and end up shrugging and saying “Hopefully beer…”
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Cold conditioning for me is moving my fermenter out to my garage and sit it in a swamp cooler filled with water. In the summer I add ice bottles, but in the winter that’s certainly not necessary. In the summer(actually spring or fall because I stop brewing from June through August) I shoot for a temp. below 45. In the fall/winter I can get her down to 32. I leave her there at least 3 weeks. Longer depends on my bottling availability.
Cold crashing I use all the frozen ice bottles I can load into her and shoot for as close to 32 as I can get. I do it overnight, then hit her with a dose of gelatin the next morning. Let it stay in the cooler until the ice is all melted then bottle.
I was looking for a place to post this regarding WLP29…I’ve made 3 Kolsch with vary levels of success, almost certainly due to variations in yeast performance.
The first was quite nice, fermented around 65F. For some reason I decided I would have liked a little more of the vinous character that some Kolsch have, so the next time I made it, I fermented somewhat higher…maybe 68F or so. That one was a disaster…the beer never cleared despite well over a month of cold conditioning in the keg, and even gelatin. It wasn’t just the appearance, but the yeast flavor could be discerned easily and destroyed the delicate subtlety that you look for in the style. It wasn’t a horrible beer, but it wasn’t a Kolsch at all.
Last one I did I fermented cooler…I think maybe 62ish, trying to avoid the disaster of the 2nd, and it was decent, but had a noticable acetyldehyde note that didn’t go away. It was OK, but the green apple bugged me with every glass.
My thinking now is that the 2nd batch was pretty much a fluke, or something else was wrong with the yeast health beyond the fermentation temp. I did starters for all three and I should have had good yeast health and cell count for all, but maybe something went wrong with #2 that I didn’t perceive when I pitched.
My next Kolsch I’ll do around 65-67 and try to make absolutely sure I have the right cell count and no other issues, but I’m curious as to others experience with this yeast. I know it’s supposed to be quite finicky and my own experience certainly bears that out. What fermentation temps do people usually use? Any other tips, dos and don’ts that I may not have thought of?
Sorry for the long post–any feedback/advice is welcome!
