Cold Crashing

If you have done a D-Rest and you are sure fermentation is complete, you can crash it. The notion of keeping the yeast active during lagering is IMO a throwback to the days when lagering was begun for final gravity had been reached.

 

“Some brewing texts recommend slowly reducing the temperature by no more than 5 °F (3 °C) per day until the temperature is at the desired setting for lagering. However, many homebrewers ignore this advice and achieve excellent results. There is agreement that in order to achieve the maximum effect the lagering needs to be done cold, with the temperature no more than 40 °F (5 °C). Many commercial breweries lager at nearly freezing temperatures, in the 32–34 °F (0–1 °C) range.”

http://byo.com/stories/item/1488-the-lowdown-on-lagering-advanced-brewing

I am one of those homebrewers who ignore the advice of a slow cooling process and I achieve excellent results.

Cheers!

 

That would depend on when you start the D-rest. I start them when fermentation is almost finished. Having said that, it couldn't hurt to taste the beer before you cold crash it.

 

The cleanup processes don't wait for fermentation to be complete before they start.

 

Yes, but I suspect not for as long as you might be thinking. I've always been able to crash my lagers after a 2-3 day diacetyl rest begun when there are a few points of attenuation to go.

 

John, I have brewed over 75 batches of lagers using a variety of different lager yeasts (about 10 different varieties) and I have never conducted a diacetyl rest. I am very sensitive to diacetyl and none of my lagers had perceptible levels of diacetyl.

When primary fermentation is complete I take the beer down to lagering temperatures (e.g., less than 40 degrees F) over a timeframe of 24-48 hours.

Based upon my personal discussions with Kai Troester and reading his blog I am of the opinion that there is indeed yeast activity during the lagering process which is part and parcel of the overall lagering phase.

From Kai’s blog:

“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) form agglomerations (basically bind with each other to form larger molecules) which become insoluble and precipitate out of solution. [Nguyen 2007]
• Hop polyphenols will drop out leading to milder hop bitterness
• Yeast sediment which cleans up the beer and removes the yeasty smell and taste associated with young beer
• 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 [Narziss 2005].
• Some yeast activity may be present which leads to further clean-up and extract reduction of the beer. I oftentimes see another extract drop of 0.1 - 0.2 Plato over the course of a few weeks.”

http://braukaiser.com/wiki/index.php?title=Fermenting_Lagers#lagering.2Fcold_conditioning

Cheers!

 

John, all of the lagers I have brewed have been of moderate gravity (e.g., 1.050-ish) and all visible signs of fermentaton are complete at around the 10 day mark. My practice is to not transfer to the secondary (which is a carboy for me) no sooner than 14 days of primary. I do not have a specific time duration for "yeast clean up". I simply let the primary go for a minimum of 14 days and then lager for about 5-6 weeks. This process 'works' in my homebrewery.

The four lagers I brewed this year (as per the above) are: CAP, Tmavý Ležák, 1896 Michelob and Bohemian Pilsner.

Cheers!

 

Narziss advocates for a very strict schedule of slow temperature drops, based on the following criteria and/or desired results:

• achievement of final attenuation
• natural carbonation
• sensory maturation of flavor compounds
• clarification
• improvement of head retention
• excretion of unstable protein compounds
• improvement of colloidal stability due to the low temperatures

Maybe as a homebrewer you are not necessarily concerned with such (best) practices in these areas. But if you maintain equally long lagering times, I fail to see what benefits severe cold crashing might have vs dropping temps slowly. I believe @honkey mentioned that he avoided such cold crashing as it negatively affected his yeast. Perhaps he can chime in here as well.

 

And the Brulosophy folks suggest that on the homebrew level lager beers can be completed in less than a total of 30 days.

http://brulosophy.com/methods/lager-method/

Lots of varying viewpoints here.

Cheers!

 

I don't see what slow temperature drop (as opposed to crashing) has to do with most of those desired results, except for the first two. The first one, achievement of final attenuation, is easy to overcome...just don't cold crash before attenuation is finished...I don't think anyone who crashes advocates doing it before it's done. I suppose the natural carbonation one means that the continued fermentation (of incompletely attenuated) wort/beer as it is cooling slowly will produce carbonation. Okay, but how many people want to do that, and what would be the advantage? The rest IMO are functions of lagering and not functions of the cooling rate per se.

 

Well, Narziss's approach does imply secondary fermentation (often in a different vessel), so there's that. And, sure, all of those things can be achieved during primary and at higher temperatures. But to achieve optimal results (according to Narziss), final attenuation should be a longer process, lest the remaining extract be consumed too quickly. He even provides charts to show at what temperatures the remaining percentage of extract is optimally consumed. As for the advantages of natural CO2, in my opinion CO2 that is produced and retained naturally has a softer feel and less of a carbonic bite than forced (also forced carbonation is believed to scrub SO2). But that's a whole different point/debate (that the prevailing US literature similarly sees as moot).

 

Yes. Just providing the viewpoint of the most respected professor of lager brewing over the last century. OP is, of course, free to follow advice of US bloggers instead if he wishes.

 

You know, while I always recommend tasting the beer before transfers to keg and cold crashing, I have been burned a few times, where I didn't taste diacetyl only to taste it in the kegged beer. While I believe cold crashing is great when a beer is finished, I am second guessing exactly how to tell that it is finished.